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diff --git a/old/52838-0.txt b/old/52838-0.txt deleted file mode 100644 index 17dca7e..0000000 --- a/old/52838-0.txt +++ /dev/null @@ -1,4175 +0,0 @@ -The Project Gutenberg EBook of Creation of the Teton Landscape, by -J. D. Love and John C. Reed - -This eBook is for the use of anyone anywhere in the United States and most -other parts of the world at no cost and with almost no restrictions -whatsoever. You may copy it, give it away or re-use it under the terms of -the Project Gutenberg License included with this eBook or online at -www.gutenberg.org. If you are not located in the United States, you'll have -to check the laws of the country where you are located before using this ebook. - -Title: Creation of the Teton Landscape - The Geologic Story of Grand Teton National Park - -Author: J. D. Love - John C. Reed - -Release Date: August 18, 2016 [EBook #52838] - -Language: English - -Character set encoding: UTF-8 - -*** START OF THIS PROJECT GUTENBERG EBOOK CREATION OF THE TETON LANDSCAPE *** - - - - -Produced by Stephen Hutcheson, Dave Morgan and the Online -Distributed Proofreading Team at http://www.pgdp.net - - - - - - - View west toward Grand Teton on skyline. Hedrick’s Pond surrounded - by “knob and kettle” topography is in foreground, tree-covered - Burned Ridge moraine is in middle distance, and extending from it to - foot of mountains is gray flat treeless glacial outwash plain. - _National Park Service photo by W. E. Dilley._ - - [Illustration: View west up Cascade Canyon, with north face of Mt. - Owen in center. _National Park Service photo by H. D. Pownall._] - - _To Fritiof M. Fryxell, geologist, teacher, - writer, mountaineer, and the first ranger-naturalist - in Grand Teton National Park._ - - _All who love and strive to understand - the Teton landscape follow in his footsteps._ - - - - - _CREATION OF THE - TETON LANDSCAPE_ - The Geologic Story of - Grand Teton National Park - - - _By - J. D. LOVE AND JOHN C. REED, JR. - U.S. Geological Survey_ - - _Library of Congress Catalogue Card No._: 68-20628 - _ISBN_ O-931895-08-1 - - 1st Edition - 1968 - - 1st Revised Edition - 1971 - - Reprinted 1979 - Reprinted 1984 - Reprinted 1989 - - Grand Teton Natural History Association - Moose, Wyoming 83012 - - - - - CONTENTS - - - Foreword 6 - THE STORY BEGINS 8 - First questions, brief answers 9 - An extraordinary story 10 - An astronaut’s view 12 - A pilot’s view 14 - A motorist’s view 15 - View north 15 - View west 18 - View south 19 - A mountaineer’s view 20 - CARVING THE RUGGED PEAKS 24 - Steep mountain slopes—the perpetual battleground 24 - Rock disintegration and gravitational movement 24 - Running water cuts and carries 26 - Glaciers scour and transport 28 - Effects on Jackson Hole 30 - MOUNTAIN UPLIFT 36 - Kinds of mountains 36 - Anatomy of faults 38 - Time and rate of uplift 40 - Why are mountains here? 41 - The restless land 43 - ENORMOUS TIME AND DYNAMIC EARTH 45 - Framework of time 45 - Rocks and relative age 45 - Fossils and geologic time 46 - Radioactive clocks 47 - The yardstick of geologic time 48 - PRECAMBRIAN ROCKS—THE CORE OF THE TETONS 51 - Ancient gneisses and schists 51 - Granite and pegmatite 55 - Black dikes 58 - Quartzite 63 - A backward glance 64 - The close of the Precambrian—end of the beginning 64 - THE PALEOZOIC ERA—TIME OF LONG-VANISHED SEAS AND THE DEVELOPMENT - OF LIFE 66 - The Paleozoic sequence 66 - Alaska Basin—site of an outstanding rock and fossil record 66 - Advance and retreat of Cambrian seas; an example 69 - Younger Paleozoic formations 74 - THE MESOZOIC—ERA OF TRANSITION 79 - Colorful first Mesozoic strata 79 - Drab Cretaceous strata 81 - Birth of the Rocky Mountains 82 - TERTIARY—TIME OF MAMMALS, MOUNTAINS, LAKES, AND VOLCANOES 86 - Rise and burial of mountains 88 - The first big lake 92 - Development of mammals 95 - Volcanoes 98 - QUATERNARY—TIME OF ICE, MORE LAKES, AND CONTINUED CRUSTAL - DISTURBANCE 102 - Hoback normal fault 103 - Volcanic activity 103 - Preglacial lakes 104 - The Ice Age 105 - Modern glaciers 112 - THE PRESENT AND THE FUTURE 113 - APPENDIX 115 - Acknowledgements 115 - Selected references—if you wish to read further 116 - About the authors 117 - Index of selected terms and features 118 - - - - - _FOREWORD_ - - -Geology is the science of the Earth—the study of the forces, processes, -and past life that not only shape our land but influence our daily lives -and our Nation’s welfare. This booklet, prepared by two members of the -U.S. Geological Survey, discusses how geologic phenomena are responsible -for the magnificent scenery of the Teton region. - -Recognition of the complex geologic history of our Earth is vital to the -enjoyment and appreciation of beautiful landscapes and other natural -wonders, to the planning of our cities and highway systems, to the wise -use of our water supplies, to the study of earthquake and landslide -areas, to the never-ending search for new mineral deposits, and to the -conservation and development of our known natural resources. Who can -say, in the long run, which of the many uses of this knowledge is the -most compelling reason to seek an understanding of the Earth? - - [Illustration: Signature] - - W. T. Pecora, _Director_ - U.S. Geological Survey - - _This booklet is based on geologic investigations by the - U. S. Geological Survey in cooperation with the National Park Service, - U. S. Department of Interior._ - - “_Something hidden. Go and find it. - Go and look behind the Ranges— - Something lost behind the Ranges. - Lost and waiting for you. Go._” - KIPLING—_THE EXPLORER_ - - - - - THE STORY BEGINS - - -The Teton Range is one of the most magnificent mountain ranges on the -North American Continent. Others are longer, wider, and higher, but few -can rival the breath-taking alpine grandeur of the eastern front of the -Tetons. Ridge after jagged ridge of naked rock soar upward into the -western sky, culminating in the towering cluster of peaks to which the -early French voyageurs gave the name “_les Trois Tetons_” (the three -breasts). The range hangs like a great stone wave poised to break across -the valley at its base. To the south and east are lesser mountains, -interesting and scenic but lacking the magic appeal of the Tetons. - -This is a range of many moods and colors: stark and austere in morning -sun, but gold and purple and black in the softly lengthening shadows of -afternoon; somber and foreboding when the peaks wrap themselves in the -tattered clouds of an approaching storm, but tranquil and ethereal blue -and silver beneath a full moon. - -These great peaks and much of the floor of the valley to the east, -_Jackson Hole_ (a _hole_ was the term used by pioneer explorers and -mountain men to describe any open valley encircled by mountains), lie -within Grand Teton National Park, protected and preserved for the -enjoyment of present and future generations. Each year more than 3 -million visitors come to the park. Many pause briefly and pass on. -Others stay to explore its trails, fish its streams, study the plants -and wildlife that abound within its borders, or to savor the colorful -human history of this area. - -Most visitors, whatever their interests and activities, are probably -first attracted to the park by its unsurpassed mountain scenery. The -jagged panorama of the Tetons is the backdrop to which they may turn -again and again, asking questions, seeking answers. How did the -mountains form? How long have they towered into the clouds, washed by -rain, riven by frost, swept by wind and snow? What enormous forces -brought them forth and raised them skyward? What stories are chronicled -in their rocks, what epics chiseled in the craggy visage of this -mountain landscape? Why are the Tetons different from other mountains? - - - First questions, brief answers - -_How did the Tetons and Jackson Hole form?_ They are both tilted blocks -of the earth’s crust that behaved like two adjoining giant trapdoors -hinged so that they would swing in opposite directions. The block on the -west, which forms the Teton Range, was hinged along the Idaho-Wyoming -State line; the eastern edge was uplifted along a fault (a fracture -along which displacement has occurred). This is why the highest peaks -and steepest faces are near the east margin of the range. The hinge line -of the eastern block, which forms Jackson Hole, was in the highlands to -the east. The western edge of the block is downdropped along the fault -at the base of the Teton Range. As a consequence, the floor of Jackson -Hole tilts westward toward the Tetons (see cross section inside back -cover). - -_When did the Tetons and Jackson Hole develop the spectacular scenery we -see today?_ The Tetons are the youngest of all the mountain ranges in -the Rocky Mountain chain. Most other mountains in the region are at -least 50 million years old but the Tetons are less than 10 million and -are still rising. Jackson Hole is of the same age and is still sinking. -The Teton landscape is the product of many earth processes, the most -recent of which is cutting by water and ice. Within the last 15,000 -years, ice sculpturing of peaks and canyons and impounding of glacial -lakes have added finishing touches to the scenic beauty. - -_Why did the Tetons rise and Jackson Hole sink?_ For thousands of years -men have wondered about the origin of mountains and their speculations -have filled many books. Two of the more popular theories are: (1) -continental drift (such as South America moving away from Africa), with -the upper lighter layer of the earth’s crust moving over the lower -denser layer and wrinkling along belts of weakness; and (2) convection -currents within the earth, caused by heat transfer, resulting in linear -zones of wrinkling, uplift, and collapse. - -These concepts were developed to explain the origin of mountainous areas -hundreds or thousands of miles long but they do not answer directly the -question of why the Tetons rose and Jackson Hole sank. As is discussed -in the chapter on mountains, it is probable that semifluid rock far -below the surface of Jackson Hole flowed north into the Yellowstone -Volcanic Plateau-Absaroka Range volcanic area, perhaps taking the place -of the enormous amount of ash and lava blown out of volcanoes during the -last 50 million years. The origin of the line of weakness that marks the -Teton fault along the east face of the Teton Range may go back to some -unknown inequality in the earth’s composition several billion years ago. -Why it suddenly became active late in the earth’s history is an -unanswered question. - -The ultimate source of heat and energy that caused the mountains and -basins to form probably is disintegration of radioactive materials deep -within the earth. The Tetons are a spectacular demonstration that the -enormous energy necessary to create mountains is not declining, even -though our planet is several billion years old. - - - An extraordinary story - -Visitors whose curiosity is whetted by this unusual and varied panorama -are not satisfied with only a few questions and answers. They sense that -here for the asking is an extraordinary _geologic_ (_geo_—earth; -_logic_—science) story. With a little direction, many subtle features -become evident—features that otherwise might escape notice. Here, for -example, is a valley with an odd U-shape. There is a sheer face -crisscrossed with light- and dark-colored rocks. On the valley floor is -a tuft of pine trees that seem to be confined to one particular kind of -rock. On the rolling hills is a layer of peculiar white soil—the only -soil in which coyote dens are common. All these are geologically -controlled phenomena. In short, with a bit of initial guidance, the -viewer gains an ability to observe and to understand so much that the -panorama takes on new depth, vividness, and excitement. It changes from -a flat, two-dimensional picture to a colorful multi-dimensional exhibit -of the earth’s history. - - [Illustration: Figure 1. _The Tetons from afar—an astronaut’s view - of the range and adjacent mountains, basins, and plateaus. Width of - area shown in photo is about 100 miles. Stippled pattern marks - boundary of Grand Teton National Park._] - - [Illustration: Figure 2. _Sketch of the Teton Range and Jackson - Hole, southwest view. Drawing by J. R. Stacy._ - - BLOCK DIAGRAM VIEW SOUTHWEST SHOWING THE TETON RANGE AND JACKSON - HOLE] - - - An astronaut’s view - -The Tetons are a short, narrow, and high mountain range, distinctive in -the midst of the great chain of the Rocky Mountains, the backbone of -western North America. Figure 1 shows how the Tetons and their -surroundings might appear if you viewed them from a satellite at an -altitude of perhaps a hundred miles. The U. S. Geological Survey -topographic map of Grand Teton National Park shows the names of many -features not indicated on figure 1 or on the geologic map inside the -back cover. The Teton Range is a rectangular mountain block about 40 -miles long and 10-15 miles wide. It is flanked on the east and west by -flat-floored valleys. Jackson Hole is the eastern one and Teton Basin -(called Pierre’s Hole by the early trappers) is the western. - -The Teton Range is not symmetrical. The highest peaks lie near the -eastern edge of the mountain block, rather than along its center, as is -true in conventional mountains, and the western slopes are broad and -gentle in contrast to the precipitous eastern slopes. The northern end -of the range disappears under enormous lava flows that form the -Yellowstone Volcanic Plateau. Even from this altitude the outlines of -some of these flows can be seen. - -On the south the Teton Range abuts almost at right angles against a -northwest-trending area of lower and less rugged mountains (the Snake -River, Wyoming, and Hoback Ranges). These mountains appear altogether -different from the Tetons. They consist of a series of long parallel -ridges cut or separated by valleys and canyons. This pattern is -characteristic of mountains composed of crumpled, steeply tilted rock -layers—erosion wears away the softer layers, leaving the harder ones -standing as ridges. - -On the east and northeast, Jackson Hole is bounded by the Gros Ventre -and Washakie Ranges, which are composed chiefly of folded hard and soft -sedimentary rocks. In contrast, between these mountains and the deepest -part of Jackson Hole to the west, thick layers of soft nearly flat-lying -sedimentary rocks have been sculptured by streams and ice into randomly -oriented knife-edge ridges and rolling hills separated by broad valleys. -The hills east of the park are called the Mount Leidy Highlands and -those northeast are the Pinyon Peak Highlands. - - - A pilot’s view - -If you descend from 100 miles to about 5 miles above the Teton region, -the asymmetry of the range, the extraordinary variety of landscapes, and -the vivid colors of rocks become more pronounced. - -Figure 2 shows a panorama of the Teton Range and Jackson Hole from a -vantage point over the Pinyon Peak Highlands. The rough steep slopes and -jagged ridges along the east front of the range contrast with smoother -slopes and more rounded ridges on the western side. Nestled at the foot -of the mountains and extending out onto the floor of Jackson Hole are -tree-rimmed sparkling lakes of many sizes and shapes. Still others lie -in steep-sided rocky amphitheaters near the mountain crests. - -One of the most colorful flight routes into Jackson Hole is from the -east, along the north flank of the Gros Ventre Mountains. For 40 miles -this mountain range is bounded by broad parallel stripes of bright-red, -pink, purple, gray, and brown rocks. Some crop out as cliffs or ridges, -and others are _badlands_ (bare unvegetated hills and valleys with steep -slopes and abundant dry stream channels). In places the soft beds have -broken loose and flowed down slopes like giant varicolored masses of -taffy. These are mudflows and landslides. The colorful rocks are bounded -on the south by gray and yellow tilted layers forming snowcapped peaks -of the Gros Ventre Mountains. - -These landscapes are the product of many natural forces acting on a -variety of rock types during long or short intervals of geologic time. -Each group of rocks records a chapter in the geologic story of the -region. Other chapters can be read from the tilting, folding, and -breaking of the rocks. The latest episodes are written on the face of -the land itself. - - - A motorist’s view - -Most park visitors first see the Teton peaks from the highway. Whether -they drive in from the south, east, or north, there is one point on the -route at which a spectacular panorama of the Tetons and Jackson Hole -suddenly appears. Part of the thrill of these three views is that they -are so unexpected and so different. The geologic history is responsible -for these differences. - - - _View north._— - -Throughout the first 4 miles north of the town of Jackson, the view of -the Tetons from U. S. 26-89 is blocked by East Gros Ventre Butte. At the -north end of the butte, the highway climbs onto a flat upland at the -south boundary of Grand Teton National Park. Without any advance -warning, the motorist sees the whole east front of the Teton Range -rising steeply from the amazingly flat floor of Jackson Hole. - -From the park boundary turnout no lakes or rivers are visible to the -north but the nearest line of trees in the direction of the highest -Teton peaks marks the approximate position of the Gros Ventre River. The -elevation of this river is surprising, for the route has just come up a -150-foot hill, out of the flat valley of a much smaller stream, yet here -at eye-level is a major river perched on an upland plain. The reason for -these strange relations is that the hill is a fault scarp (see fig. 16A -for a diagram) and the valley in which the town of Jackson is located -was dropped 150 feet or more in the last 15,000 years. - -On the skyline directly west of the turnout are horizontal and inclined -layers of rocks. These once extended over the tops of the highest peaks -but were worn away from some parts as the mountains rose. All along the -range, trees grow only up to _treeline_ (also called _timberline_—a -general elevation above which trees do not grow) which here is about -10,500 feet above the sea. To the southeast and east, beyond the -sage-covered floor of Jackson Hole, are rolling partly forested slopes -marking the west end of the Gros Ventre Mountains. They do not look at -all like the Tetons because they were formed in a very different manner. -The Gros Ventres are folded mountains that have foothills; the Tetons -are faulted mountains that do not. - - Figure 3. _The Teton landscape as seen from Signal Mountain._ - - [Illustration: A. _View west across Jackson Lake. Major peaks, - canyons, and outcrops of sedimentary rocks are indicated by “s.”_] - - [Illustration: B. _View northeast; a study in contrast with the - panorama above._] - -Three steepsided hills called _buttes_ rise out of the flat floor of -Jackson Hole. They are tilted and faulted masses of hard, layered rock -that have been shaped by southward-moving glaciers. Six miles north of -the boundary turnout is Blacktail Butte, on the flanks of which are -west-dipping white beds. Southwest of the turnout is East Gros Ventre -Butte, composed largely of layered rocks that are exposed along the road -from Jackson almost to the turnout. These are capped by very young lava -that forms the brown cliff overlooking the highway at the north end of -the butte. To the southwest is West Gros Ventre Butte, composed of -similar rocks. - - - _View west._— - -The motorist traveling west along U. S. 26-287 is treated to two -magnificent views of the Teton Range. The first is 8 miles and the -second 13 miles west of Togwotee Pass. At these vantage points, between -20 and 30 miles from the mountains, the great peaks seem half suspended -between earth and sky—too close, almost, to believe, but too distant to -comprehend. - -Only from closer range can the motorist begin to appreciate the size and -steepness of the mountains and to discern the details of their -architecture. The many roads on the floor of Jackson Hole furnish -ever-changing vistas, and signs provided by the National Park Service at -numerous turnouts and scenic overlooks help the visitor to identify -quickly the major peaks and canyons and the principal features of the -valley floor. Of all these roadside vantage points, the top of Signal -Mountain, an isolated hill rising nearly 1,000 feet out of the east -margin of Jackson Lake, probably offers the best overall perspective -(fig. 3). To the west, across the shimmering blue waters of Jackson -Lake, the whole long parade of rugged peaks stretches from the north -horizon to the south, many of the higher ones wearing the tattered -remnants of winter snow. From here, only 8 miles away, the towering -pinnacles, saw-toothed ridges, and deep U-shaped canyons are clearly -visible. - -Unlike most other great mountain ranges, the Tetons rise steeply from -the flat valley floor in a straight unbroken line. The high central -peaks tower more than a mile above the valley, but northward and -southward the peaks diminish in height and lose their jagged character, -gradually giving way to lower ridges and rounded hills. Some of the -details of the mountain rock can be seen—gnarled gray rocks of the high -peaks threaded by a fine white lacework of dikes, the dark band that -cleaves through Mount Moran from base to summit, and the light brown and -gray layers on the northern and southern parts of the range. - -At first glance the floor of Jackson Hole south of Signal Mountain seems -flat, smooth, and featureless, except for the Snake River that cuts -diagonally across it. Nevertheless, even the flats show a variety of -land forms. The broad sage-covered areas, low isolated hills, and -hummocky tree-studded ridges that form the foreground are all parts of -the Teton landscape, and give us clues to the natural processes that -shaped it. A critical look to the south discloses more strange things. -We take for granted the fact that the sides of normal valleys slope -inward toward a central major stream. South of Signal Mountain, however, -the visitor can see that the Snake River Valley does not fit this -description. The broad flat west of the river should slope east but it -does not. Instead, it has been tilted westward by downward movement -along the Teton fault at the base of the mountains. - - - _View south._— - -About a million motorists drive south from Yellowstone to Grand Teton -National Park each year. As they wind along the crooked highway on the -west brink of Lewis River Canyon (fig. 1), the view south is everywhere -blocked by dense forest. Then, abruptly the road leaves the canyon, -straightens out, and one can look south down a 3-mile sloping avenue cut -through the trees. There, 20 to 30 miles away, framed by the roadway, -are the snow-capped Tetons, with Jackson Lake, luminous in reflected -light, nestled against the east face. This is one of the loveliest and -most unusual views of the mountains that is available to the motorist, -partly because he is 800 feet above the level of Jackson Lake and partly -because this is the only place on a main highway where he can see -clearly the third dimension (width) of the Tetons. The high peaks are on -the east edge; they rise 7,000 feet above the lake but other peaks and -precipitous ridges, progressively diminishing in height, extend on to -the west for a dozen miles (fig. 14). Giant, relatively young lava -flows, into which the Lewis River Canyon was cut, poured southward all -the way to the shore of Jackson Lake and buried the north end of the -Teton Range (figs. 13 and 53). South of Yellowstone Park these flows -were later tilted and broken by the dropping of Jackson Hole and the -rise of the mountains. - - - A mountaineer’s view - -As in many pursuits in life, the greatest rewards of a visit to the -Tetons come to those who expend a real effort to earn them. Only by -leaving the teeming valley and going up into the mountains to hike the -trails and climb the peaks can the visitor come to know the Tetons in -all their moods and changes and view close at hand the details of this -magnificent mountain edifice. - -Even a short hike to Hidden Falls and Inspiration Point affords an -opportunity for a more intimate view of the mountains. Along the trail -the hiker can examine outcrops of sugary white granite, glittering -mica-studded dikes, and dark intricately layered rocks. Nearby are great -piles of broken fragments that have fallen from the cliffs above, and -the visitor can begin to appreciate how vulnerable are the towering -crags to the relentless onslaught of frost and snow. The roar of the -foaming stream and the thunder of the falls are constant reminders of -the patient work of running water in wearing away the “everlasting -hills.” Running his hand across one of the smoothly polished rock faces -below Inspiration Point, the hiker gains an unforgettable concept of the -power of glacial ice and its importance in shaping this majestic -landscape. Looking back across Jenny Lake at the encircling ridge of -glacial debris, he can easily comprehend the size of the ancient glacier -that once flowed down Cascade Canyon and emerged onto the floor of -Jackson Hole. - -The more ambitious hiker or mountaineer can seek out the inner recesses -of the range and explore other facets of its geology. He can visit the -jewel-like mountain lakes—Solitude, Holly, and Amphitheater are just a -few—cradled in high remote basins left by the Ice Age glaciers. He can -get a closeup view of the Teton Glacier above Amphitheater Lake, or -explore the Schoolroom Glacier, the tiny ice body below Hurricane Pass. -He may follow the trail into Garnet Canyon to see the crystals from -which the canyon takes its name and to examine the soaring ribbonlike -black dike near the end of the trail. In Alaska Basin he can study the -gently tilted layers of sandstone, limestone, and shale that once -blanketed the entire Teton Range and can search for the fossils that -help determine their age and decipher their history. From Hurricane Pass -he can see how these even layers of sedimentary rock have been broken -and displaced and how the older harder rocks that form the highest Teton -peaks have been raised far above them along the Buck Mountain fault. - -Of all those who explore the high country, it is the mountaineer who has -perhaps the greatest opportunity to appreciate its geologic story. -Indeed, the success of his climb and his very life may depend on an -intuitive grasp of the mountain geology and the processes that shaped -the peaks. He observes the most intimate details—the inclination of the -joints and fractures, which gullies are swept by falling rocks, which -projecting knobs are firm, and which cracks will safely take a piton. To -many climbers the ascent of a peak is a challenge to technical -competence, endurance, and courage, but to those endowed with curiosity -and a sharp eye it can be much more. As he stands shoulder to shoulder -with the clouds on some windswept peak, such as the Grand Teton, with -the awesome panorama dropping away on all sides, he can hardly avoid -asking how this came to be. What does the mountaineer see that inspires -this curiosity? From the very first glance, it is apparent that the -scenes to the north, south, east, and west are startlingly different. - -Looking west from the rough, narrow, weather-ravaged granite summit of -the Grand Teton, one sees far below him the layered gray cliffs of -_marine sedimentary rocks_ (solidified sediment originally deposited in -a shallow arm of the ocean) overlapping the granite and dipping gently -west, finally disappearing under the checkerboard farmland of Teton -Basin. Still farther west are the rolling timbered slopes of the Big -Hole Range in Idaho. A glance at the foreground, 3,000 feet below, shows -some unusual relations of the streams to the mountains. The watershed -divide of the Teton Range is not marked by the highest peaks as one -would expect. Streams in Cascade Canyon and in other canyons to the -north and south begin west of the peaks, bend around them, then flow -eastward in deep narrow gorges cut through the highest part of the -range, and emerge onto the flat floor of Jackson Hole. - -In the view north along the crest of the Teton Range, the asymmetry of -the mountains is most apparent. The steep east face culminating in the -highest peaks contrasts with the lower more gentle west flank of the -uplift. From the Grand Teton it is not possible to see the actual place -where the mountains disappear under the lavas of Yellowstone Park, but -the heavily timbered broad gentle surface of the lava plain is visible -beyond the peaks and extends across the entire north panorama. Still -farther north, 75 to 100 miles away, rise the snowcapped peaks (from -northwest to northeast) of the Madison, Gallatin, and Beartooth -Mountains. - -The view east presents the greatest contrasts in the shortest -distances—the flat floor of Jackson Hole is 3 miles away and 7,000 feet -below the top of the Grand Teton. Along the junction of the mountains -and valley floor are blue glacial lakes strung out like irregular beads -in a necklace. They are conspicuously rimmed by black-appearing margins -of pine trees that grow only on the surrounding glacial moraines. Beyond -these are the broad treeless boulder-strewn plains of Jackson Hole. -Fifty miles to the east and northeast, on the horizon beyond the rolling -hills of the Pinyon Peak Highlands, are the horizontally layered -volcanic rocks of the Absaroka Range. Southeast is the colorful red, -purple, green, and gray Gros Ventre River Valley, with the fresh giant -scar of the Lower Gros Ventre Slide near its mouth. Bounding the south -side of this valley are the peaks of the Gros Ventre Mountains, whose -tilted slabby gray cliff-forming layers resemble (and are the same as) -those on the west flank of the Teton Range. Seventy miles away, in the -southeast distance, beyond the Gros Ventre Mountains are the shining -snowcapped peaks of the Wind River Range, the highest peak of which -(Gannett Peak) is about 20 feet higher than the Grand Teton. - -Conspicuous on the eastern and southeastern skyline are high-level -(11,000-12,000 feet) flat-topped surfaces on both the Wind River and -Absaroka Ranges. These are remnants that mark the upper limit of -sedimentary fill of the basins adjacent to the mountains. A plain once -connected these surfaces and extended westward at least as far as the -conspicuous flat on the mountain south of Lower Gros Ventre Slide. It is -difficult to imagine the amount of rock that has been washed away from -between these remnants in comparatively recent geologic time, during and -after the rise of the Teton Range. - -From this vantage point the mountaineer also gets a concept of the -magnitude of the first and largest glaciers that scoured the landscape. -Ice flowed southwestward in an essentially unbroken stream from the -Beartooth Mountains, 100 miles away, westward from the Absaroka Range, -and northwestward from the Wind River Range (fig. 57). Ice lapped up to -treeline on the Teton Range and extended across Jackson Hole nearly to -the top of the Lower Gros Ventre Slide. The Pinyon Peak and Mount Leidy -Highlands were almost buried. All these glaciers came together in -Jackson Hole and flowed south within the ever-narrowing Snake River -Valley. - -The view south presents a great variety of contrasts. Conspicuous, as in -the view north, is the asymmetry of the range. South of the high peaks -of crystalline rocks, gray layered cliffs of limestone extend in places -all the way to the steep east face of the Teton Range where they are -abruptly cut off by the great Teton fault. - -The flat treeless floor of Jackson Hole narrows southward. Rising out of -the middle are the previously described steepsided ice-scoured rocky -buttes. Beginning near the town of Jackson, part of which is visible, -and extending as far south as the eye can see are row upon row of sharp -ridges and snowcapped peaks that converge at various angles. These are -the Hoback, Wyoming, Salt River, and Snake River Ranges. - - - - - CARVING THE RUGGED PEAKS - - -The rugged grandeur of the Tetons is a product of four geologic factors: -the tough hard rocks in the core, the amount of vertical uplift, the -recency of the mountain-making movement, and the dynamic forces of -destruction. Many other mountains in Wyoming have just as hard rocks in -their cores and an equally great amount of vertical uplift, but they -rose 50 to 60 million years ago and have been worn down by erosion from -that time on. The Tetons, on the other hand, are the youngest range in -Wyoming, less than 10 million years old, and have not had time to be so -deeply eroded. - - - Steep mountain slopes—the perpetual battleground - -Any steep slope or cliff is especially vulnerable to nature’s methods of -destruction. In the Tetons we see the never-ending struggle between two -conflicting factors. The first is the extreme toughness of the rocks and -their consequent resistance to erosion. The second is the presence of -efficient transporting agencies that move out and away from the -mountains all rock debris that might otherwise bury the lower slopes. - -The rocks making up most of the Teton Range are among the hardest, -toughest, and least porous known. Therefore, they resist mechanical -disintegration by temperature changes, ice, and water. They consist -predominantly of minerals that are subject to very little chemical decay -in the cold climate of the Tetons. - -Absence of weak layers prevents breaking of the tough rock masses under -their own weight. All these conditions, then, are favorable for -preservation of steep walls and high rock pinnacles. Nevertheless, they -do break down. Great piles of broken rock _(talus)_ that festoon the -slopes of all the higher peaks bear witness to the unrelenting assault -by the process of erosion upon the mountain citadels (figs. 4 and 31). - - - Rock disintegration and gravitational movement - -A great variation in both daily and annual temperatures results in -minute amounts of contraction and expansion of rock particles. Repeated -changes in volume produce stress and strain. Although the rocks in the -Tetons are very dense, they eventually yield; a crack forms. Water which -seeps in along this surface of weakness freezes, either overnight or -during long cold spells, and expands, thereby prying a slab of rock away -from the mountain wall. Repeated _frost wedging_, as the process is -called, results eventually in tipping the slab so that it falls. - - [Illustration: Figure 4. _Talus at the foot of the jagged - frost-riven peaks around Ice Floe Lake in the south fork of Cascade - Canyon. Photo by Philip Hyde._] - -What happens to the rock slab? It may fall and roll several hundred or -thousand feet, depending on the steepness of the mountain surface. -Pieces are broken off as it encounters obstacles. All the fragments find -their way to a valley floor or slope, where they momentarily come to -rest. Thus, rock debris is moved significant and easily observed -distances by gravity. - -None of this debris is stationary. If it is mixed with snow or saturated -with water, the whole mass may slowly flow in the same manner as a -glacier. These are called _rock glaciers_; some can be seen on the south -side of Granite Canyon and one, nearly a mile long, is in the valley -north of Eagles Rest Peak. - -The countless snow avalanches that thunder down the mountain flanks -after heavy winter snowfalls play their part, too, in gravitational -transport. Loose rocks and debris are incorporated with the moving snow -and borne down the mountainsides to the talus piles below. Trees, -bushes, and soil are swept from the sites of the slides, leaving -conspicuous scars down the slopes and exposing new rock surfaces to the -attack of water and frost. Battered, broken, and uprooted trees along -many of the canyon trails bear silent witness to the awesome power of -snowslides. - -These are some of the methods used by Nature in making debris and then, -by means of gravity, clearing it from the mountain slopes. There are -other ways, too. A weak layer of rock (usually one with a lot of clay in -it), parallel to and underlying a mountain slope, may occur between two -hard layers. An extended rainy spell may result in saturation of the -weak zone so that it is well lubricated; then an earthquake or perhaps -merely the weight of the overlying rock sends the now unstable mass -cascading down the slope to the valley below. The famous Lower Gros -Ventre Slide (fig. 5) was formed in this way on June 23, 1925. - - - Running water cuts and carries - -Running water is another effective agent that transports rock debris and -has helped dissect the Teton Range. The damage a broken water main can -wreak on a roadbed is well known, as is the havoc of destructive floods. -The spring floods of streams in the Tetons, swollen by melting snow and -ice (annual precipitation, mostly snow, in the high parts would average -a layer of water 5 feet thick), move some rock debris onto the adjoining -floor of Jackson Hole. - - [Illustration: Figure 5. _The Lower Gros Ventre slide, air oblique - view south. The top of the scar is 2,000 feet above the river; the - slide is more than a mile long and one-half mile wide. It dammed the - Gros Ventre River in the foreground, impounding a lake about 200 - feet deep and 5 miles long. Gros Ventre Mountains are in the - distance. Photo by P. E. Millward._] - -Now and then the range is deluged by summer cloudbursts. Water funnels -down the maze of gullies on the mountainsides, quickly gathering volume -and power, and plunges on to the talus slopes below, as if from gigantic -hoses. The sudden onslaught of these torrents of water on the saturated -unstable talus may trigger enormous rock and mudflows that carry vast -quantities of material down into the canyons. During the summer of 1941 -more than 100 of these flows occurred in the park. - -Wherever water moves, it carries rock fragments varying in size from -boulders to sand grains and on down to minute clay particles. _Erosion_ -(wearing away) by streams is conspicuous wherever the water is muddy, as -it always is each spring in the Snake, Buffalo Fork, and Gros Ventre -Rivers. Clear mountain streams likewise can erode. Although the volume -of material moved and the amount of downcutting of the stream bottom may -not seem great in a single stream, the cumulative effect of many streams -in an area, year after year and century after century, is enormous. -Streams not only transport rocks brought to them by gravitational -movement but also continually widen and deepen their valleys, thereby -increasing the volume of transported debris. - -The effectiveness of streams as transporting agents in the Tetons is -enhanced by steep _gradients_ (slopes); these increase water velocity -which in turn expands the capability of the streams to carry larger and -larger rock fragments. - - - Glaciers scour and transport - -Mountain landscapes shaped by frost action, gravitational transport, and -stream erosion alone generally have rounded summits, smooth slopes, and -V-shaped valleys. The jagged ridges, sharply pointed peaks, and deep -U-shaped valleys of the Tetons show that glaciers have played an -important role in their sculpture. The small present-day glaciers still -cradled in shaded recesses among the higher peaks (fig. 6) are but -miniature replicas of great ice streams that occupied the region during -the Ice Age. Evidence both here and in other parts of the world confirms -that glaciers were once far more extensive than they are today. - -Glaciers form wherever more snow accumulates during the winter than is -melted during the summer. Gradually the piles of snow solidify to form -ice, which begins to flow under its own weight. Rocks that have fallen -from the surrounding ridges or have been picked up from the underlying -bedrock are incorporated in the moving ice mass and carried along. The -ability of ice to transport huge volumes of rock is easily observed even -in the small present-day glaciers in the Tetons, all of which carry -abundant rock fragments both on and within the ice. - - [Illustration: Figure 6. _The Teton Glacier on the north side of - Grand Teton, air oblique view west. Photo by A. S. Post, August 19, - 1963._] - -Recent measurements show that the ice in the present Teton Glacier (fig. -6) moves nearly 30 feet per year. The ancient glaciers, which were much -wider and deeper, may have moved as much as several hundred feet a year, -like some of the large glaciers in Alaska. - -As the glacier moves down a valley, it scours the valley bottom and -walls. The efficiency of ice in this process is greatly increased by the -presence of rock fragments which act as abrasives. The valley bottom is -plowed, quarried, and swept clean of soil and loose rocks. Fragments of -many sizes and shapes are dragged along the bottom of the moving ice and -the hard ones scratch long parallel grooves in the underlying tough -bedrock (fig. 7). Such grooves (_glacial striae_) record the direction -of ice movement. - -The effectiveness of glaciers in cutting a U-shaped valley is -particularly striking in Glacier Gulch and Cascade Canyon (figs. 2 and -8). - -The rock-walled amphitheater at the head of a glaciated valley is called -a _cirque_ (a good example is at the upper edge of the Teton Glacier, -fig. 6). The steep cirque walls develop by frost action and by quarrying -and abrasive action of the glacier ice where it is near its maximum -thickness. Commonly the glacier scoops out a shallow basin in the floor -of the cirque. Amphitheater Lake, Lake Solitude, Holly Lake, and many of -the other small lakes high in the Teton Range are located in such -basins. - -The sharp peaks and the jagged knife-edge ridges so characteristic of -the Tetons are divides left between cirques and valleys carved by the -ancient glaciers. - - - Effects on Jackson Hole - -Rock debris is carried toward the end of the glacier or along the -margins where it is released as the ice melts. The semicircular ridge of -rock fragments that marks the downhill margin of the glacier is called a -_terminal moraine_; that along the sides is a _lateral moraine_ (figs. 9 -and 10). These are formed by the slow accumulation of material in the -same manner as that at the end of a conveyor belt. They are not built by -material pushed up ahead of the ice as if by a bulldozer. Large boulders -carried by ice are called _erratics_; many of these are scattered on the -floor of Jackson Hole and on the flanks of the surrounding mountains -(fig. 11). - - [Illustration: Figure 7. _Rock surface polished and grooved by ice - on the floor of Glacier Gulch._] - -Great volumes of water pour from melting ice near the lower end of a -glacier. These streams, heavily laden with rock flour produced by the -grinding action of the glacier and with debris liberated from the -melting ice, cut channels through the terminal moraine and spread a -broad apron of gravel, sand, and silt down-valley from the glacier -terminus (end). Material deposited by streams issuing from a glacier is -called _outwash_; the sheet of outwash in front of the glacier is called -an _outwash plain_. If the terminus is retreating, masses of old -stagnant ice commonly are buried beneath the outwash; when these melt, -the space they once occupied becomes a deep circular or irregular -depression called a _kettle_ (fig. 12); many of these now contain small -lakes or swamps. - -As a glacier retreats, it may build a series of terminal moraines, -marking pauses in the recession of the ice front. Streams issuing from -the ice behind each new terminal moraine are incised more and more -deeply into the older moraines and their outwash plains. Thus, new and -younger layers of bouldery debris are spread at successively lower and -lower levels. These surfaces are called _outwash terraces_. - - [Illustration: Figure 8. _East face of the Teton Range showing some - of the glacial features, air oblique view. Cascade Canyon, the - U-shaped valley, was cut by ice. The glacier flowed toward the - flats, occupied the area of Jenny Lake (foreground), and left an - encircling ring of morainal debris, now covered with trees. The flat - bare outwash plain in foreground was deposited by meltwater from the - glacier. The lake occupies a depression that was left when the ice - melted away. National Park Service photo by Bryan Harry._] - - [Illustration: Figure 9. _Cutaway view of a typical valley - glacier._] - - [Illustration: Figure 10. _Recently-built terminal moraine of the - Schoolroom Glacier, a small ice mass near the head of the south fork - of Cascade Canyon. The present glacier lies to the right just out of - the field of view. The moraine marks a former position of the ice - terminus; the lake (frozen over in this picture) occupies the - depression left when the glacier wasted back from the moraine to its - present position. Crest of the moraine stands about 50 feet above - the lake level. Many of the lakes along the foot of the Teton Range - occupy similar depressions behind older moraines. Photo by Philip - Hyde._] - - [Illustration: Figure 11. _Large ice-transported boulder of - coarse-grained pegmatite and granite resting on Cretaceous shale - near Mosquito Creek, on the southwest margin of Jackson Hole. Many - boulders at this locality are composed of pegmatite rock - characteristic of the middle part of the Teton Range. This - occurrence demonstrates that boulders 40 feet in diameter were - carried southward 25 miles and left along the west edge of the ice - stream, 1,500 feet above the base of the glacier on the floor of - Jackson Hole._] - -Just as the jagged ridges, U-shaped valleys, and ice-polished rocks of -the Teton Range attest the importance of glaciers in carving the -mountain landscape, the flat gravel outwash plains and hummocky moraines -on the floor of Jackson Hole demonstrate their efficiency in -transporting debris from the mountains and shaping the scenery of the -valley. - -Glaciers sculptured all sides of Jackson Hole and filled it with ice to -an elevation between 1,000 and 2,000 feet above the present valley -floor. The visitor who looks eastward from the south entrance to the -park can see clearly glacial scour lines that superficially resemble a -series of terraces on the bare lower slopes of the Gros Ventre -Mountains. Southward-moving ice cut these features in hard rocks. -Elsewhere around the margins of Jackson Hole, especially where the rocks -are soft, evidence that the landscape was shaped by ice has been partly -or completely obliterated by later events. Rising 1,000 feet above the -floor of Jackson Hole are several steepsided buttes (figs. 13 and 55) -described previously, that represent “islands” of hard rock overridden -and abraded by the ice. After the ice melted, these buttes were -surrounded and partly buried by outwash debris. - - [Illustration: Figure 12. _“The Potholes,” knob and kettle - topography caused by melting of stagnant ice partly buried by - outwash gravel. Air oblique view north from over Burned Ridge - moraine (see fig. 61 for orientation). Photo by W. B. Hall and J. M. - Hill._] - -The story of the glaciers and their place in the geologic history of the -Teton region is discussed in more detail later in this booklet. - - [Illustration: Figure 13. _Radar image of part of Tetons and Jackson - Hole. Distance shown between left and right margins is 35 miles. - Lakes from left to right: Phelps, Taggart, Bradley, Jenny, Leigh, - Jackson. Blacktail Butte is at lower left. Channel of Snake River - and outwash terraces are at lower left. Burned Ridge and Jackson - Lake moraines are in center. Lava flows at upper right engulf north - end of Tetons. Striated surfaces at lower right are glacial scour - lines made by ice moving south from Yellowstone National Park. Image - courtesy of National Aeronautics and Space Administration._] - - - - - MOUNTAIN UPLIFT - - -Mountains appear ageless, but as with people, they pass through the -stages of birth, youth, maturity, and old age, and eventually disappear. -The Tetons are youthful and steep and are, therefore, extremely -vulnerable to destructive processes that are constantly sculpturing the -rugged features and carrying away the debris. The mountains are being -destroyed. Although the processes of destruction may seem slow to us, we -know they have been operating for millions of years—so why have the -mountains not been leveled? How did they form in the first place? - - - Kinds of mountains - -There are many kinds of mountains. Some are piles of lava and debris -erupted from a volcano. Others are formed by the bowing up of the -earth’s crust in the shape of a giant dome or elongated arch. Still -others are remnants of accumulated sedimentary rocks that once filled a -basin between preexisting mountains and which are now partially worn -away. An example of this type is the Absaroka Range 40 miles northeast -of the Tetons (figs. 1 and 52). - -The Tetons are a still different kind—a _fault block mountain range_ -carved from a segment of the earth’s crust that has been uplifted along -a fault. The _Teton fault_ is approximately at the break in slope where -the eastern foot of the range joins the flats at the west edge of -Jackson Hole (see map inside back cover), but in most places is -concealed beneath glacial deposits and debris shed from the adjacent -steep slopes. The shape of the range and its relation to Jackson Hole -have already been described. Clues as to the presence of the fault are: -(1) the straight and deep east face of the Teton Range, (2) absence of -foothills, (3) asymmetry of the range (fig. 14), and (4) small _fault -scarps_ (cliffs or steep slopes formed by faulting) along the mountain -front (fig. 15). - - [Illustration: Figure 14. _Air oblique view south showing the width - and asymmetry of Teton Range. Grand Teton is left of center and Mt. - Moran is the broad humpy peak still farther left. Photo taken - October 1, 1965_.] - -Recent geophysical surveys of Jackson Hole combined with data from deep -wells drilled in search of oil and gas east of the park also yield -valuable clues. By measuring variations in the earth’s magnetic field -and in the pull of gravity and by studying the speed of shock waves -generated by small dynamite explosions, Dr. John C. Behrendt of the U. -S. Geological Survey has determined the depth and tilt of rock layers -buried beneath the veneer of glacial debris and stream-laid sand and -gravel on the valley floor. This information was used in constructing -the geologic cross section in the back of the booklet. The same rock -layers that cap the summit of Mount Moran (fig. 27) are buried at depths -of nearly 24,000 feet beneath the nearby floor of Jackson Hole but are -cut off by the Teton fault at the west edge of the valley. Thus the -approximate amount of movement along the fault here would be about -30,000 feet. - - - Anatomy of faults - -The preceding discussion shows that the Tetons are an upfaulted mountain -block. Why is this significant? The extreme youth of the Teton fault, -its large amount of displacement, and the fact that the newly upfaulted -angular mountain block was subjected to intense glaciation are among the -prime factors responsible for the development of the magnificent alpine -scenery of the Teton Range. An understanding of the anatomy of faults -is, therefore, pertinent. - - [Illustration: Figure 15. _Recent fault scarp (arrows indicate base) - offsetting alluvial fan at foot of Rockchuck Peak. View west from - Cathedral Group scenic turnout. National Park Service photo by W. E. - Dilley and R. A. Mebane._] - -A fault is a plane or zone in the earth’s crust along which the rocks on -one side have moved in relation to the rocks on the other. There are -various kinds of faults just as there are various types of mountains. -Three principal types of faults are present in the Teton region: normal -faults, reverse faults, and thrust faults. A _normal fault_ (fig. 16A) -is a steeply _dipping_ (steeply inclined) fault along which rocks above -the fault have moved _down_ relative to those beneath it. A _reverse -fault_ (fig. 16B) is a steeply inclined fault along which the rocks -above the fault have moved _up_ relative to those below it. A _thrust -fault_ (fig. 16C) is a gently inclined fault along which the principal -movement has been more nearly horizontal than vertical. - -Normal faults may be the result of tension or pulling apart of the -earth’s crust or they may be caused by adjustment of the rigid crust to -the flow of semi-fluid material below. The crust sags or collapses in -areas from which the subcrustal material has flowed and is bowed up and -stretched in areas where excess subcrustal material has accumulated. In -both areas the adjustments may result in normal faults. - -Reverse faults are generally caused by compression of a rigid block of -the crust, but some may also be due to lateral flow of subcrustal -material. - -Thrust faults are commonly associated with tightly bent or folded rocks. -Many of them are apparently caused by severe compression of part of the -crust, but some are thought to have formed at the base of slides of -large rock masses that moved from high areas into adjacent low areas -under the influence of gravity. - -The Teton fault (see cross section inside back cover) is a normal fault; -the Buck Mountain fault, which lies west of the main peaks of the Teton -Range, is a reverse fault. No thrust faults have been recognized in the -Teton Range, but the mountains south and southwest of the Tetons (fig. -1) display several enormous thrust faults along which masses of rocks -many miles in extent have moved tens of miles eastward and -northeastward. - - - Time and rate of uplift - -When did the Tetons rise? - -A study of the youngest sedimentary rocks on the floor of Jackson Hole -shows that the Teton Range began to rise rapidly and take its present -shape less than 9 million years ago. The towering peaks themselves are -direct evidence that the rate of uplift far exceeded the rate at which -the rising block was worn away by erosion. The mountains are still -rising, and comparatively rapidly, as is indicated by small faults -cutting the youngest deposits (fig. 15). - -How rapidly? Can the rate be measured? - -We know that in less than 9 million years (and probably in less than 7 -million years) there has been 25,000 to 30,000 feet of displacement on -the Teton fault. This is an average of about 1 foot in 300-400 years. -The movement probably was not continuous but came as a series of jerks -accompanied by violent earthquakes. One fault on the floor of Jackson -Hole near the southern boundary of the park moved 150 feet in the last -15,000 years, an average of 1 foot per 100 years. - -In view of this evidence of recent crustal unrest, it is not surprising -that small earthquakes are frequent in the Teton region. More violent -ones can probably be expected from time to time. - - Figure 16. _Types of faults._ - - [Illustration: A.—Normal fault (tensional)] - - [Illustration: B.—Reverse fault (compressional)] - - [Illustration: C.—Thrust fault (compressional)] - - - Why are mountains here? - -Why did the Tetons form where they are? - -At the beginning of this booklet we discussed briefly the two most -common theories of origin of mountains: continental drift and convection -currents. The question of why mountains are where they are and more -specifically why the Tetons are here remains a continuing scientific -challenge regardless of the wealth of data already accumulated in our -storehouse of knowledge. - -The mobility of the earth’s crust is an established fact. Despite its -apparent rigidity, laboratory experiments demonstrate that rocks flow -when subjected to extremely high pressures and temperatures. If the -stress exceeds the strength at a given pressure and temperature, the -rock breaks. Flowing and fracturing are two of the ways by which rocks -adjust to the changing environments at various levels in the earth’s -crust. These acquired characteristics, some of which can be duplicated -in the laboratory, are guides by which we interpret the geologic history -of rocks that once were deep within the earth. - -The site of the Teton block no doubt reflects hidden inequalities at -depth. We cannot see these, nor in this area can we drill below the -outer layer of the earth; nevertheless, measurements of gravity and of -the earth’s magnetic field clearly show that they exist. - -We know that the Tetons rose at the time Jackson Hole collapsed but the -volume of the uplifted block is considerably less than that of the -downdropped block. This, then, was not just a simple case in which all -the subcrustal material displaced by the sinking block was squeezed -under the rising block (the way a hydraulic jack works). What happened -to the rest of the material that once was under Jackson Hole? It could -not be compressed so it had to go somewhere. - -As you look northward from the top of the Grand Teton or Mount Moran, or -from the main highway at the north edge of Grand Teton National Park, -you see the great smooth sweep of the volcanic plateau in Yellowstone -National Park. Farther off to the northeast are the strikingly layered -volcanic rocks of the Absaroka Range (fig. 52). For these two areas, an -estimate of the volume of volcanic rock that reached the surface and -flowed out, or was blown out and spread far and wide by wind and water, -is considerably in excess of 10,000 cubic miles. On the other hand, this -volume is many times more than that displaced by the sagging and -downfaulting of Jackson Hole. - -Where did the rest of the volcanic material come from? Is it pertinent -to our story? Teton Basin, on the west side of the Teton Range, and the -broad Snake River downwarp farther to the northwest (fig. 1) are -sufficiently large to have furnished the remainder of the volcanic -debris. As it was blown out of vents in the Yellowstone-Absaroka area, -its place could have been taken deep underground by material that moved -laterally from below all three downdropped areas. The movement may have -been caused by slow convection currents within the earth, or perhaps by -some other, as yet unknown, force. The sagging of the earth’s crust on -both sides of the Teton Range as well as the long-continued volcanism -are certainly directly related to the geologic history of the park. - -In summary, we theorize as to how the Tetons rose and Jackson Hole sank -but are not sure why the range is located at this particular place, why -it trends north, why it rose so high, or why this one, of all the -mountain ranges surrounding the Yellowstone-Absaroka volcanic area, had -such a unique history of uplift. These are problems to challenge the -minds of generations of earth scientists yet to come. - - - The restless land - -Among the greatest of the park’s many attractions is the solitude one -can savor in the midst of magnificent scenery. Only a short walk -separates us from the highway, torrents of cars, noise, and tension. -Away from these, everything seems restful. - -Quiescent it may seem, yet the landscape is not static but dynamic. This -is one of the many exciting ideas that geology has contributed to -society. The concept of the “everlasting hills” is a myth. All the -features around us are actually rather short-lived in terms of geologic -time. The discerning eye detects again and again the restlessness of the -land. We have discussed many bits of evidence that show how the -landscape and the earth’s crust beneath it are constantly being carved, -pushed up, dropped down, folded, tilted, and faulted. - -The Teton landscape is a battleground, the scene of a continuing -unresolved struggle between the forces that deform the earth’s crust and -raise the mountains and the slow processes of erosion that strive to -level the uplands, fill the hollows, and reduce the landscape to an -ultimate featureless plain. The remainder of this booklet is devoted to -tracing the seesaw conflict between these inexorable antagonists through -more than 2.5 billion years as they shaped the present landscape—and the -battle still goes on. - -Evidence of the struggle is all around us. Even though to some observers -it may detract from the restfulness of the scene, perhaps it conveys to -all of us a new appreciation of the tremendous dynamic forces -responsible for the magnificence of the Teton Range. - -The battle is indicated by the small faults that displace both the land -surface and young deposits at the east base of Mount Teewinot, Rockchuck -Peak (fig. 15), and other places along the foot of the Tetons. - -Jackson Hole continues to drop and tilt. The gravel-covered surfaces -that originally sloped southward are now tilted westward toward the -mountains. The Snake River, although the major stream, is not in the -lowest part of Jackson Hole; Fish Creek, a lesser tributary near the -town of Wilson, is 15 feet lower. For 10 miles this creek flows -southward parallel to the Snake River but with a gentler gradient, thus -permitting the two streams to join near the south end of Jackson Hole. -As tilting continues, the Snake River west of Jackson tries to move -westward but is prevented from doing so by long flood-control levees -built south of the park. - -Recent faults also break the valley floor between the Gros Ventre River -and the town of Jackson. - -The ever-changing piles of rock debris that mantle the slopes adjacent -to the higher peaks, the creeping advance of rock glaciers, the -devastating snow avalanches, and the thundering rockfalls are specific -reminders that the land surface is restless. Jackson Hole contains more -landslides and rock mudflows than almost any other part of the Rocky -Mountain region. They constantly plague road builders (fig. 17) and add -to the cost of other types of construction. - -All of these examples of the relentless battle between constructive and -destructive processes modifying the Teton landscape are but minor -skirmishes. The bending and breaking of rocks at the surface are small -reflections of enormous stresses and strains deep within the earth where -the major conflict is being waged. It is revealed every now and then by -a convulsion such as the 1959 earthquake in and west of Yellowstone -Park. Events of this type release much more energy than all the nuclear -devices thus far exploded by man. - - [Illustration: Figure 17. _Slide blocking main highway in northern - part of Grand Teton National Park. National Park Service photo by - Eliot Davis, May 1952._] - - - - - ENORMOUS TIME AND DYNAMIC EARTH - - - Framework of time - -One of geology’s greatest philosophical contributions has been the -demonstration of the enormity of geologic time. Astronomers deal with -distances so great that they are almost beyond understanding; nuclear -physicists study objects so small that we can hardly imagine them. -Similarly, the geologist is concerned with spans of time so immense that -they are scarcely comprehensible. Geology is a science of time as well -as rocks, and in our geologic story of the Teton region we must refer -frequently to the geologic time scale, the yardstick by which we measure -the vast reaches of time in earth history. - - - Rocks and relative age - -Very early in the science of geology it was recognized that in many -places one can tell the comparative ages of rocks by their relations to -one another. For example, most _sedimentary rocks_ are consolidated -accumulations of large or small rock fragments and were deposited as -nearly horizontal layers of gravel, sand, or mud. In an undisturbed -sequence of sedimentary rocks, the layer on the bottom was deposited -first and the layer on top was deposited last. All of these must, of -course, be younger than any previously formed rock fragments -incorporated in them. - -_Igneous rocks_ are those formed by solidification of molten material, -either as lava flows on the earth’s surface (_extrusive igneous rocks_) -or at depth within the earth (_intrusive igneous rocks_). The relative -ages of extrusive igneous rocks can often be determined in much the same -way as those of sedimentary strata. A lava flow is younger than the -rocks on which it rests, but older than those that rest on top of it. - -An intrusive igneous rock must be younger than the rocks that enclosed -it at the time it solidified. It may contain pieces of the enclosing -rocks that broke off the walls and fell into the liquid. Pebbles of the -igneous rock that are incorporated in nearby sedimentary layers indicate -that the sediments must be somewhat younger. - -All of these criteria tell us only that one rock is older or younger -than another. They tell us little about the absolute age of the rocks or -about how much older one is than the other. - - - Fossils and geologic time - -Fossils provide important clues to the ages of the rocks in which they -are found. The slow evolution of living things through geologic time can -be traced by a systematic study of fossils. The fossils are then used to -determine the relative ages of the rocks that contain them and to -establish a geologic time scale that can be applied to fossil-bearing -rocks throughout the world. Figure 18 shows the major subdivisions of -the last 600 million years of geologic time and some forms of life that -dominated the scene during each of these intervals. Strata containing -closely related fossils are grouped into _systems_; the time interval -during which the strata comprising a particular system were deposited is -termed a _period_. The periods are subdivisions of larger time units -called _eras_ and some are split into smaller time units called -_epochs_. Strata deposited during an epoch comprise a _series_. Series -are in turn subdivided into rock units called _groups_ and formations. -Expressed in tabular form these divisions are: - - Subdivisions of Time-rock units Rock units - geologic time - - Era - Period System - Epoch Series - Group - Formation - -The time scale based on the study of fossil-bearing sedimentary rocks is -called the stratigraphic time scale; it is given in table 1. The -subdivisions are arranged in the same order in which they were -deposited, with the oldest at the bottom and the youngest at the top. -All rocks older than Cambrian (the first period in the Paleozoic Era) -are classed as Precambrian. These rocks are so old that fossils are rare -and therefore cannot be conveniently used as a basis for subdivision. - -The stratigraphic time scale is extremely useful, but it has serious -drawbacks. It can be applied only to fossil-bearing strata or to rocks -whose ages are determined by their relation to those containing fossils. -It cannot be used directly for rocks that lack fossils, such as igneous -rocks, or metamorphic rocks in which fossils have been destroyed by heat -or pressure. It is used to establish the relative ages of sedimentary -strata throughout the world, but it gives no information as to how long -ago a particular layer was deposited or how many years a given period or -era lasted. - - - Radioactive clocks - -The measurement of geologic time in terms of years was not possible -until the discovery of natural radioactivity. It was found that certain -atoms of a few elements spontaneously throw off particles from their -nuclei and break down to form atoms of other elements. These decay -processes take place at constant rates, unaffected by heat, pressure, or -chemical conditions. If we know the rate at which a particular -radioactive element decays, the length of time that has passed since a -mineral crystal containing the elements formed can be calculated by -comparing the amount of the radioactive element remaining in the crystal -with the amount of disintegration products present. - - [Illustration: Figure 18. _Major subdivisions of the last 600 - million years of geologic time and some of the dominant forms of - life._] - - MILLIONS OF - YEARS AGO - - 0 Man - 0-60 CENOZOIC QUATERNARY and TERTIARY Mammals - 60-130 MESOZOIC CRETACEOUS - 130-180 JURASSIC Dinosaurs - 180-220 TRIASSIC - 220-260 PALEOZOIC PERMIAN Reptiles - 260-350 PENNSYLVANIAN, Amphibians - MISSISSIPPIAN - 350-400 DEVONIAN Fishes - 400-440 SILURIAN Sea scorpions - 440-500 ORDOVICIAN Nautiloids - 500-530 CAMBRIAN Trilobites - 530- PRECAMBRIAN Soft-bodied - creatures - -Three principal radioactive clocks now in use are based on the decay of -uranium to lead, rubidium to strontium, and potassium to argon. They are -effective in dating minerals millions or billions of years old. Another -clock, based on the decay of one type of carbon (_Carbon-14_) to -nitrogen, dates organic material, but only if it is less than about -40,000 years old. - -The uranium, rubidium, and potassium clocks are especially useful in -dating igneous rocks. By determining the absolute ages of igneous rocks -whose stratigraphic relations to fossil-bearing strata are known, it is -possible to estimate the number of years represented by the various -subdivisions of the stratigraphic time scale. - - - The yardstick of geologic time - -Recent estimates suggest that the earth was formed at least 4.5 billion -years ago. To visualize the length of geologic time and the relations -between the stratigraphic and absolute time scales, let us imagine a -yardstick as representing the length of time from the origin of the -earth to the present (fig. 19). On one side of the yardstick we plot -time in years; on the other, we plot the divisions of the stratigraphic -time scale according to the most reliable absolute age determinations. - - [Illustration: Table 1. The stratigraphic time scale.] - - Era System or period Series or epoch - - Cenozoic Quaternary Recent - Pleistocene - Tertiary Pliocene - Miocene - Oligocene - Eocene - Paleocene - Mesozoic Cretaceous - Jurassic - Triassic - Paleozoic Permian - Pennsylvanian - Mississippian - Devonian - Silurian[1] - Ordovician - Cambrian - — Precambrian - - -[1]_The Silurian is the only major subdivision of the stratigraphic time - scale not represented in Grand Teton National Park._ - - -We are immediately struck by the fact that all of the subdivisions of -the stratigraphic time scale since the beginning of the Paleozoic are -compressed into the last 5 inches of our yardstick! All of the other 31 -inches represent Precambrian time. We also see that subdivisions of the -stratigraphic time scale do not represent equal numbers of years. We use -smaller and smaller subdivisions as we approach the present. (Notice the -subdivisions of the Tertiary and Quaternary in table 1 that are too -small to show even in the enlarged part of figure 19). This is because -the record of earth history is more vague and incomplete the farther -back in time we go. In effect, we are very nearsighted in our view of -time. This “geological myopia” becomes increasingly evident throughout -the remainder of this booklet. - - [Illustration: Figure 19. _The geologic time scale—our yardstick in - time._] - - ABSOLUTE TIME (Years ago) INCHES STRATIGRAPHIC TIME SCALE - - First man → 0 CENOZOIC - 1 MESOZOIC - First dinosaurs → 2 PALEOZOIC - 3 - 500 million 4 - First abundant fossils → 5 PRECAMBRIAN - 6 - 7 - 1 billion 8 - 9 - 10 - 11 - 12 - 13 - 14 - Oldest known fossils → 15 - 2 billion 16 - 17 - 18 - 19 - 20 - 21 - 22 - 23 - 3 billion 24 - 25 - 26 - 27 - Oldest dated rocks → 28 - 29 - 30 - 31 - 4 billion 32 - 33 - 34 - 35 - Minimum age of the earth → 36 - - ENLARGEMENT OF THE LAST SIX INCHES - ABSOLUTE TIME INCHES STRATIGRAPHIC TIME SCALE - (Years Ago) - - 0 0 CENOZOIC QUATERNARY - TERTIARY - MESOZOIC CRETACEOUS - 1 JURASSIC - TRIASSIC - 2 PALEOZOIC PERMIAN - PENNSYLVANIAN - MISSISSIPPIAN - 3 DEVONIAN - SILURIAN - ORDOVICIAN - 500 million 4 CAMBRIAN - 5 PRECAMBRIAN - 6 - - - - - PRECAMBRIAN ROCKS—THE CORE OF THE TETONS - - -The visitor who looks at the high, rugged peaks of the Teton Range is -seeing rocks that record about seven-eighths of all geologic time. These -Precambrian rocks are part of the very foundation of the continent and -are therefore commonly referred to by geologists as basement rocks. In -attempting to decipher their origin and history we peer backward through -the dim mists of time, piecing together scattered clues to events that -occurred billions of years ago, perhaps during the very birth of the -North American Continent. To cite an oft-quoted example, it is as though -we were attempting to read the history of an ancient and long-forgotten -civilization from the scattered unnumbered pages of a torn manuscript, -written in a language that we only partially understand. - - - Ancient gneisses and schists - -The oldest Precambrian rocks in the Teton Range are layered gneisses and -schists exposed over wide areas in the northern and southern parts of -the range and as scattered isolated masses in the younger granite that -forms the high peaks in the central parts. The layered gneisses may be -seen easily along the trails in the lower parts of Indian Paintbrush and -Death Canyons, and near Static Peak. - -The _layered gneisses_ are composed principally of quartz, feldspar, -_biotite_ (black mica), and _hornblende_ (a very dark-green or black -mineral commonly forming rodlike crystals). Distinct layers, a few -inches to several feet thick, contain different proportions of these -minerals and account for the banded appearance. Layers composed almost -entirely of quartz and feldspar are light-gray or white, whereas darker -gray layers contain higher proportions of biotite and hornblende. - -Some layers are dark-green to black _amphibolite_, composed principally -of hornblende but with a little feldspar and quartz. In many places the -gneisses include layers of _schist_, a flaky rock, much of which is -mica. At several places on the east slopes of Mount Moran thin layers of -impure gray marble are found interleaved with the gneisses. West of -Static Peak along the Alaska Basin Trail a heavy dark rock with large -amounts of _magnetite_ (strongly magnetic black iron oxide) occurs as -layers in the gneiss. - -In some places the gneiss contains dark-reddish crystals of garnet as -much as an inch in diameter. Commonly the garnet crystals are surrounded -by white “halos” which lack biotite or hornblende, probably because the -constituents necessary to form these minerals were absorbed by the -garnet crystals. In Death Canyon and on the slopes of Static Peak some -layers of gray gneiss contain egg-shaped masses of magnetite as much as -one-half inch in diameter (fig. 20). These masses are likewise -surrounded by elliptical white halos and have the startling appearance -of small eyes peering from the rock. Appropriately, this rock has been -called the “bright-eyed” gneiss by Prof. Charles C. Bradley in his -published study (Wyoming Geological Association, 1956) of this area. - -What were the ancient rocks from which the gneisses of the Teton Range -were formed? Most of the evidence has been obliterated but a few -remaining clues enable us to draw some general conclusions. The banded -appearance of many of the gneisses suggests that they were formed from -sedimentary and volcanic rocks that accumulated on the sea floor near a -chain of volcanic islands—perhaps somewhat similar to the modern -Aleutians or the islands of Indonesia. When these deposits were buried -deep in the earth’s crust the chemical composition of some layers may -have undergone radical changes. Other layers, however, still have -compositions resembling those of younger rocks elsewhere whose origins -are better known. For example, the layers of impure marble were probably -once beds of sandy limestone, and the lighter colored gneiss may have -been muddy sandstone, possibly containing volcanic ash. Some dark -amphibolite layers could represent altered lava flows or beds of -volcanic ash; others may have resulted from the addition of silica to -muddy magnesium-rich limestone during metamorphism. The magnetite-rich -gneiss probably was originally a sedimentary iron ore. - - [Illustration: Figure 20. _“Bright-eyed” gneiss from Death Canyon. - The dark magnetite spots are about ¼ inch in diameter. The - surrounding gneiss is composed of quartz, feldspar, and biotite, but - biotite is missing in the white halos around the magnetite._] - -Minerals that were most easily altered at depth reacted with one another -to form new minerals more “at home” under the high temperature and -pressure in this environment just as the ingredients in a cake react -when heated in an oven. Rocks formed by such processes are called -_metamorphic rocks_; careful studies of the minerals that they contain -suggest that the layered gneisses developed at temperatures as high as -1000°F at depths of 5 to 10 miles. Under these conditions the rocks must -have behaved somewhat like soft taffy as is shown by layers that have -been folded nearly double without being broken (fig. 21). Folds such as -these range from fractions of an inch to thousands of feet across and -are found in gneisses throughout the Teton Range. In a few places folds -are superimposed in such a way as to indicate that the rocks were -involved in several episodes of deformation in response to different -sets of stress during metamorphism. - -When did these gneisses form? Age determinations of minerals containing -radioactive elements show that granite which was intruded into them -after they were metamorphosed and folded is more than 2.5 billion years -old. They must, therefore, be older than that. Thus, they probably are -at least a billion years older than rocks containing the first faint -traces of life on earth and 2 billion years older than the oldest rocks -containing abundant fossils. How much older is not known, but the -gneisses are certainly among the oldest rocks in North America and -record some of the earliest events in the building of this continent. - - Figure 21. _Folds in layered gneisses._ - - [Illustration: A. _North face of the ridge west of Eagles Rest Peak. - The face is about 700 feet high. Notice the extreme contortion of - the gneiss layers._] - - [Illustration: B. _Closeup view of some of the folds near the bottom - of the face in figure A. The light-colored layers are composed - principally of quartz and feldspar. The darker layers are rich in - hornblende._] - -Irregular bodies of granite gneiss are interleaved with the layered -gneisses in the northern part of the Teton Range. The _granite gneiss_ -is relatively coarse grained, streaky gray or pink, and composed -principally of quartz, feldspar, biotite, and hornblende. It differs -from enclosing layered gneisses in its coarser texture, lack of -layering, and more uniform appearance. The dark minerals (biotite and -hornblende) are concentrated in thin discontinuous wisps that give the -rock its streaky appearance. - -The largest body of granite gneiss is exposed in a belt 1 to 2 miles -wide and 10 miles long extending northeastward from near the head of -Moran Canyon, across the upper part of Moose Basin, and into the lower -reaches of Webb Canyon. This gneiss may have been formed from granite -that invaded the ancient sedimentary and volcanic rocks before they were -metamorphosed, or it may have been formed during metamorphism from some -of the sediments and volcanics themselves. - -At several places in Snowshoe, Waterfalls, and Colter Canyons the -layered gneisses contain discontinuous masses a few tens or hundreds of -feet in diameter of heavy dark-green or black _serpentine_. This rock is -frequently called “_soapstone_” because the surface feels smooth and -soapy to the touch. Indians carved bowls (fig. 22) from similar material -obtained from the west side of the Tetons and from the Gros Ventre -Mountains to the southeast. Pebbles of serpentine along streams draining -the west side of the Tetons have been cut and polished for jewelry and -sold as “_Teton jade_”; it is much softer and less lustrous than real -jade. The serpentine was formed by metamorphism of dark-colored igneous -rocks lacking quartz and feldspar. - - - Granite and pegmatite - -Contrary to popular belief, _granite_ (crystalline igneous rock composed -principally of quartz and feldspar) forms only a part of the Teton -Range. The Grand Teton (fig. 6) and most surrounding subsidiary peaks -are sculptured from an irregular mass of granite exposed continuously -along the backbone of the range from Buck Mountain northward toward -upper Leigh Canyon. The rock is commonly fine grained, white or -light-gray, and is largely composed of crystals of gray quartz and white -feldspar about the size and texture of the grains in very coarse lump -sugar. Flakes of black or dark-brown mica (biotite) and silvery white -mica (_muscovite_) about the size of grains of pepper are scattered -through the rock. - -From the floor of Jackson Hole the granite cliffs and buttresses of the -high peaks appear nearly white in contrast to the more somber grays and -browns of surrounding gneisses and schists. These dark rocks are laced -by a network of irregular light-colored granite dikes ranging in -thickness from fractions of an inch to tens of feet (fig. 23). - - [Illustration: Figure 22. _Indian bowls carved from soapstone, - probably from the Teton Range. Mouth of the unbroken bowl is about 4 - inches in diameter._] - -The largest masses of granite contain abundant unoriented angular blocks -and slabs of the older gneisses. These inclusions range from a few -inches in diameter (fig. 24) to slabs hundreds of feet thick and -thousands of feet long. - -Dikes or irregular intrusions of pegmatite are found in almost every -exposure of granite. _Pegmatite_ contains the same minerals as granite -but the individual mineral crystals are several inches or even as much -as a foot in diameter. - -Some pegmatites contain silvery plates or tabular crystals of muscovite -mica as much as 6 inches across that can be split into transparent -sheets with a pocket knife. Others have dark-brown biotite mica in -crystals about the size and shape of the blade of a table knife. - -A few pegmatites contain scattered red-brown crystals of garnet ranging -in size from that of a BB shot to a small marble; a few in Garnet Canyon -and Glacier Gulch are larger than baseballs (fig. 25). The garnets are -fractured and many are partly altered to _chlorite_ (a dull-green -micaceous mineral) so they are of no value as gems. - - Figure 23. _Dikes of granite and pegmatite._ - - [Illustration: A. _Network of light-colored granite dikes on the - northeast face of the West Horn on Mt. Moran. The dikes cut through - gneiss in which the layers slant steeply downward to the left. The - face is about 700 feet high. Snowfield in the foreground is at the - edge of the Falling Ice Glacier._] - - [Illustration: B. _Irregular dike of granite and pegmatite cutting - through dark layered gneisses near Wilderness Falls in Waterfalls - Canyon. The cliff face is about 80 feet high. Contacts of the dike - are sharp and angular and cut across the layers in the enclosing - gneiss._] - -Pegmatite _dikes_ (tabular bodies of rock that, while still molten, were -forced along fractures in older rocks) commonly cut across granite -dikes, but in many places the reverse is true. Some dikes are composed -of layers of pegmatite alternating with layers of granite (fig. 26), -showing that the pegmatite and granite are nearly contemporaneous. Prof. -Bruno Giletti and his coworkers at Brown University, using the -rubidium-strontium radioactive clock, determined that the granite and -pegmatite in the Teton Range are about 2.5 billion years old. - - [Illustration: Figure 24. _Angular blocks of old streaky granite - gneiss in fine-grained granite northwest of Lake Solitude. The - difference in orientation of the streaks in the gneiss blocks - indicates that the blocks have been rotated with respect to one - another and that the fine-grained granite must therefore have been - liquid at the time of intrusion. A small light-colored dike in the - upper left-hand block of gneiss ends at the edge of the block; it - intruded the gneiss before the block was broken off and incorporated - in the granite. A small dike of pegmatite cuts diagonally through - the granite just to the left of the hammer and extends into the - blocks of gneiss at both ends. This dike was intruded after the - granite had solidified. Thus, in this one small exposure we can - recognize four ages of rocks: the streaky granite gneiss, the - light-colored dike, the fine-grained granite, and the small - pegmatite dike._] - - - Black dikes - -Even the most casual visitor to the Teton Range notices the remarkable -black band that extends down the east face of Mount Moran (figs. 27 and -28) from the summit and disappears into the trees north of Leigh Lake. -This is the outcropping edge of a steeply inclined dike composed of -_diabase_, a nearly black igneous rock very similar to basalt. Thinner -diabase dikes are visible on the east face of Middle Teton, on the south -side of the Grand Teton, and in several other places in the range (see -geologic map inside back cover). - - [Illustration: Figure 25. _Garnet crystal in pegmatite. The crystal - is about 6 inches in diameter. Other minerals are feldspar (white) - and clusters of white mica flakes. The mica crystals appear dark in - the photograph because they are wet._] - -The diabase is a heavy dark-greenish-gray to black rock that turns rust -brown on faces that have been exposed to the weather. It is studded with -small lath-shaped crystals of feldspar that are greenish gray in the -fresh rock and milk white on weathered surfaces. - -The black dikes formed from molten rock that welled up into nearly -vertical fissures in the older Precambrian rocks. Toward the edges of -the dikes the feldspar laths in the diabase become smaller and smaller -(fig. 29), indicating that the wall rocks were relatively cool when the -_magma_ or melted rock was intruded. Rapid chilling at the edges -prevented growth of large crystals. In many places hot solutions from -the dike permeated the wall rocks, staining them rosy red. - - [Illustration: Figure 26. _A small dike of pegmatite and granite - cutting through folded layered gneiss in Death Canyon. - Coarse-grained pegmatite forms most of the dike, but fine-grained - granite is found near the center. Small offshoots of the dike - penetrate into the wall rocks. The dike cuts straight across folds - in the enclosing gneisses and must therefore have been intruded - after development of the folds. The white ruler is about 6 inches - long._] - -The black dike on Mount Moran is about 150 feet thick near the summit of -the peak. This dike has been traced westward for more than 7 miles. -Where it passes out of the park south of Green Lakes Mountain it is 100 -feet thick. The amount of molten material needed to form the exposed -segment of this single dike could fill Jenny Lake three times over. The -other dikes are thinner and not as long: the dike on Middle Teton is 20 -to 40 feet thick, and the dike on Grand Teton is 40 to 60 feet thick. - - [Illustration: Figure 27. _Air oblique view of the east face of Mt. - Moran, showing the great black dike. Main mass of the mountain is - layered gneiss and streaky granite gneiss. White lines are dikes of - granite and pegmatite; light-gray mound on the summit is about 50 - feet of Cambrian sedimentary rock (Flathead Sandstone). Notice that - the black dike cuts across the dikes of granite and pegmatite but - that its upper edge is covered by the much younger layer of - sandstone. Falling Ice Glacier is in the left center; Skillet - Glacier is in the lower right center. Photo by A. S. Post. - University of Washington, August 19, 1963._] - - [Illustration: Figure 28. _The great black dike on the east face of - Mt. Moran. The dike is about 150 feet thick and its vertical extent - in the picture is about 3,000 feet. The fractures in the dike - perpendicular to its walls are cracks formed as the liquified rock - cooled and crystallized. Falling Ice Glacier is in the center. - National Park Service photo by H. D. Pownall._] - - [Illustration: Figure 29. _Closeup view of the edge of the Middle - Teton black dike exposed on the north wall of Garnet Canyon near the - west end of the trail. Dike rock (diabase) is on the right; wall - rock (gneiss) is on the left. Match shows scale._] - -The black dikes must be the youngest of the Precambrian units because -they cut across all other Precambrian rocks. The dikes must have been -intruded before the beginning of Cambrian deposition inasmuch as they do -not cut the oldest Cambrian beds. Gneiss adjacent to the dike on Mount -Moran contains biotite that was heated and altered about 1.3 billion -years ago according to Professor Giletti. The alteration is believed to -have occurred when the dike was emplaced; therefore this and similar -dikes elsewhere in the range are probably about 1.3 billion years old. - - - Quartzite - -At about the same time as the dikes were being intruded in the Tetons, -many thousands of feet of sedimentary rocks, chiefly sandstone, were -deposited in western Montana, 200 miles northwest of Grand Teton -National Park. The sandstone was later recrystallized and recemented and -became a very dense hard rock called _quartzite_. Similar quartzite, -possibly part of the same deposit, was laid down west of the north end -of the Teton Range, within the area now called the Snake River downwarp -(fig. 1). - -The visitor who hikes or camps anywhere on the floor of Jackson Hole -becomes painfully aware of the thousands upon thousands of remarkably -rounded hard quartzite boulders. He wonders where they came from because -nowhere in the adjacent mountains is this rock type exposed. The answer -is that the quartzites were derived from a long-vanished uplift (figs. -42 and 46), carried eastward by powerful rivers past the north end of -the Teton Range, and then were deposited in a vast sheet of gravel that -covered much of Jackson Hole 60 to 80 million years ago. Since then, -these virtually indestructible boulders have been re-worked many times -by streams and ice, yet still retain the characteristics of the original -ancient sediments. - - - A backward glance - -So far we have seen that the Precambrian basement exposed in the Teton -Range contains a complex array of rocks of diverse origins and various -ages. Before passing on to the younger rocks, reference to our yardstick -may help to place the Precambrian events in their proper perspective. - -In all of Precambrian time, which encompasses more than 85 percent of -the history of the earth (31 of the 36 inches of our yardstick), only -two events are dated in the Teton Range: the intrusion of granite and -pegmatite about 2.5 billion years ago, and the emplacement of the black -dikes about 1.3 billion years ago. These dates are indicated by heavy -arrows on the time scale (fig. 30). The ancient gneisses and schists -were formed sometime before 2.5 billion years ago, and probably are no -older than 3.5 billion years, the age of the oldest rocks dated anywhere -in the world. - - - The close of the Precambrian—end of the beginning - -More than 700 million years elapsed between intrusion of the black dikes -and deposition of the first Paleozic sedimentary rocks—a longer period -of time than has elapsed since the beginning of the Paleozic Era. During -this enormous interval the Precambrian rocks were uplifted, exposed to -erosion, and gradually worn to a nearly featureless plain, perhaps -somewhat resembling the vast flat areas in which similar Precambrian -rocks are now exposed in central and eastern Canada. At the close of -Precambrian time, about 600 million years ago, the plain slowly -floundered and the site of the future Teton Range disappeared beneath -shallow seas that were to wash across it intermittently for the next 500 -million years. It is to the sediments deposited in these seas that we -turn to read the next chapter in the geologic story of the Teton Range. - - [Illustration: Figure 30. _A glance at the yardstick. The geologic - time scale shows positions of principal events recorded in the - Precambrian rocks of the Tetons._] - - ABSOLUTE TIME (Years ago) INCHES - - Beginning of the Paleozoic. First abundant fossils → 4 - 1 billion 8 - Maximum age of black dikes → 10 - Oldest known fossils 15 - 2 billion 16 - Old granite and pegmatite 20 - 3 billion 24 - Gneisses and schists formed sometime in this interval 20-27 - Oldest dated rocks → 28 - 4 billion → 32 - Minimum age of the earth 36 - - - - -THE PALEOZOIC ERA—TIME OF LONG-VANISHED SEAS AND THE DEVELOPMENT OF LIFE - - - The Paleozoic sequence - -North, west, and south of the highest Teton peaks the soaring spires and -knife-edge ridges of Precambrian rock give way to rounded spurs and -lower flat-topped summits, whose slopes are palisaded by continuous gray -cliffs that resemble the battlements of some ancient and long-abandoned -fortress (fig. 31). As mentioned previously, the cliffs are the -projecting edges of layers of sedimentary rocks of Paleozoic age that -accumulated in or along the margins of shallow seas. At one time the -layers formed a thick unbroken, nearly horizontal blanket across the -Precambrian basement rocks, but subsequent uplift of the eastern edge of -the Teton fault block tilted them westward. They were then stripped from -the highest peaks. - -The Paleozoic and younger sedimentary rocks in the Teton region are -subdivided into _formations_, each of which is named. A formation is -composed of rock layers which, because of their similar physical -characteristics, can be distinguished from overlying and underlying -layers. They must be thick enough to be shown on a geologic map. Table 2 -lists the various Paleozoic formations present in and adjacent to Grand -Teton National Park and gives their thicknesses and characteristics. -These sedimentary rocks are of special interest, for they not only -record an important chapter of geologic history but elsewhere in the -region they contain petroleum and other mineral deposits. - -The Paleozoic rocks can be viewed close at hand from the top of the -Teton Village tram (fig. 32) on the south boundary of the park. A less -accessible but equally spectacular exposure of Paleozoic rocks is in -Alaska Basin, along the west margin of the park, where they are stacked -like even layers in a gigantic cake (fig. 33). - - - Alaska Basin—site of an outstanding rock and fossil record - -Strata in Alaska Basin record with unusual clarity the opening chapters -in the chronicle of seas that flowed and ebbed across the future site of -the Teton Range during most of the Paleozoic Era. In the various rock -layers are inscribed stories of the slow advance and retreat of ancient -shorelines, of the storm waves breaking on long-vanished beaches, and of -the slow and intricate evolution of the myriads of sea creatures that -inhabited these restless waters. - - [Illustration: Figure 31. _Paleozoic rocks on the west flank of the - Teton Range, air oblique view west. Ragged peaks in the foreground - (Buck Mountain on the left center, Mt. Wister, with top outlined by - snow patch on the extreme right), are carved in Precambrian rocks. - Banded cliffs in the background are sedimentary rocks. Alaska Basin - is at upper right. Teton Basin, a broad, extensively farmed valley - in eastern Idaho, is at top. Photo by A. S. Post, University of - Washington, 1963._] - -Careful study of the fossils allows us to determine the age of each -formation (table 3). Even more revealing, the fossils themselves are -tangible evidence of the orderly parade of life that crossed the Teton -landscape during more than 250 million years. Here is a record of -Nature’s experiments with life, the triumphs, failures, the bizarre, the -beautiful. - - [Illustration: Table 2.—Paleozoic sedimentary rocks exposed in the - Teton region.] - - Age Formation Thickness Description Where exposed - (feet) - - Permian Phosphoria 150-250 Dolomite, gray, North and west - Formation cherty, sandy, flanks of Teton - black shale and Range, north - phosphate beds; flank of Gros - marine. Ventre Mountains, - southern Jackson - Hole. - Pennsylvanian Tensleep 600-1,500 Tensleep Sandstone, North and west - and Amsden light-gray, hard, flanks of Teton - Formations underlain by Range, north - Amsden Formation, flank of Gros - a domolite and red Ventre Mountains, - shale with a basal southern Jackson - red sandstone; Hole. - marine. - Mississippian Madison 1,000-1,200 Limestone, North and west - Limestone blue-gray, hard, flanks of Teton - fossiliferous; Range, north - thin red shale in flank of Gros - places near top; Ventre Mountains, - marine. southern Jackson - Hole. - Devonian Darby 200-500 Dolomite, dark-gray North and west - Formation to brown, fetid, flanks of Teton - hard, and brown, Range, north - black, and yellow flank of Gros - shale; marine. Ventre Mountains, - southern Jackson - Hole. - Ordovician Bighorn 300-500 Dolomite, North and west - Dolomite light-gray, flanks of Teton - siliceous, very Range, north and - hard; white dense west flanks of - very fine-grained Gros Ventre - dolomite at top; Mountains, - marine. southern Jackson - Hole. - Cambrian Gallatin 180-300 Limestone, blue North and west - Limestone gray, hard, flanks of Teton - thin-bedded; Range and Gros - marine. Ventre Mountains. - Gros Ventre 600-800 Shale, green, North and west - Formation flaky, with Death flanks of Teton - Canyon Limestone Range and Gros - Member composed of Ventre Mountains. - about 300 feet of - hard cliff-forming - limestone in - middle; marine. - Flathead 175-200 Sandstone, North and west - Sandstone reddish-brown, flanks of Teton - very hard, Range and Gros - brittle; partly Ventre Mountains. - marine. - -The regularity and parallel relations of the layers in well-exposed -sections such as the one in Alaska Basin suggest that all these rocks -were deposited in a single uninterrupted sequence. However, the fossils -and regional distribution of the rock units show that this is not really -the case. The incomplete nature of this record becomes apparent if we -plot the ages of the various formations on the absolute geologic time -scale (fig. 34). The length of time from the beginning of the Cambrian -Period to the end of the Mississippian Period is about 285 million -years. The strata in Alaska Basin are a record of approximately 120 -million years. More than half of the pages in the geologic story are -missing even though, compared with most other areas, the book as a whole -is remarkably complete! During these unrecorded intervals of time either -no sediments were deposited in the area of the Teton Range or, if -deposited, they were removed by erosion. - - [Illustration: Figure 32. _Paleozoic marine sedimentary rocks near - south boundary of Grand Teton National Park. View is south from top - of Teton Village tram. National Park Service photo by W. E. Dilley - and R. A. Mebane._] - - - Madison Limestone - Darby Formation - Bighorn Dolomite - Gallatin Limestone - - - Advance and retreat of Cambrian seas: an example - -The first invasion and retreat of the Paleozoic sea are sketched on -figure 35. Early in Cambrian time a shallow seaway, called the -_Cordilleran trough_, extended from southern California northeastward -across Nevada into Utah and Idaho (fig. 35A). The vast gently rolling -plain on Precambrian rocks to the east was drained by sluggish -westward-flowing rivers that carried sand and mud into the sea. Slow -subsidence of the land caused the sea to spread gradually eastward. Sand -accumulated along the beaches just as it does today. As the sea moved -still farther east, mud was deposited on the now-submerged beach sand. -In the Teton area, the oldest sand deposit is called the Flathead -Sandstone (fig. 36). - -The mud laid down on top of the Flathead Sandstone as the shoreline -advanced eastward across the Teton area is now called the Wolsey Shale -Member of the Gros Ventre Formation. Some shale shows patterns of cracks -that formed when the accumulating mud was briefly exposed to the air -along tidal flats. Small phosphatic-shelled animals called _brachiopods_ -inhabited these lonely tidal flats (fig. 37A and 37B) but as far as is -known, nothing lived on land. Many shale beds are marked with faint -trails and borings of wormlike creatures, and a few contain the remains -of tiny very intricately developed creatures with head, eyes, segmented -body, and tail. These are known as trilobites (fig. 37C and 37D). -Descendants of these lived in various seas that crossed the site of the -dormant Teton Range for the next 250 million years. - - [Illustration: Figure 33. _View southwest across Alaska Basin, - showing tilted layers of Paleozoic sedimentary rocks on the west - flank of the Teton Range. National Park Service photo._] - - - Mount Meek - Madison Limestone - Bighorn Dolomite - Death Canyon Limestone Member - Flathead Sandstone - Precambrian Rock - - -As the shoreline moved eastward, the Death Canyon Limestone Member of -the Gros Ventre Formation (fig. 33) was deposited in clear water farther -from shore. Following this the sea retreated to the west for a short -time. In the shallow muddy water resulting from this retreat the Park -Shale Member of the Gros Ventre Formation was deposited. In places -underwater “meadows” of algae flourished on the sea bottom and built -extensive reefs (fig. 38A). From time to time shoal areas were hit by -violent storm waves that tore loose platy fragments of recently -solidified limestone and swept them into nearby channels where they were -buried and cemented into thin beds of jumbled fragments (fig. 38B) -called _“edgewise” conglomerate_. These are widespread in the shale and -in overlying and underlying limestones. - - [Illustration: Table 3. _Formations exposed in Alaska Basin._] - - AGE (Numbers FORMATION (Thickness) ROCKS AND FOSSILS - show age in - millions of - years) - - (310) - MISSISSIPPIAN MADISON LIMESTONE Uniform thin beds of - (Total about 1,100 blue-gray limestone and - feet, but only lower sparse very thin layers of - 300 feet preserved in shale. Brachiopods, corals, - this section) and other fossils abundant. - (345) - LATE AND DARBY FORMATION (About Thin beds of gray and buff - MIDDLE DEVONIAN 350 feet) dolomite interbedded with - layers of gray, yellow, and - black shale. A few fossil - brachiopods, corals, and - bryozoans. - (390) - (425) - LATE AND BIGHORN DOLOMITE (About Thick to very thin beds of - MIDDLE 450 feet; Leigh blue-gray or brown dolomite, - ORDOVICIAN Dolomite Member about white on weathered surfaces. - 40 feet thick at top) A few broken fossil - brachiopods, bryozoans, and - horn corals. Thin beds of - white fine-grained dolomite - at top are the Leigh Member. - (440) - (500) - LATE CAMBRIAN GALLATIN LIMESTONE (180 Blue-gray limestone mottled - feet) with irregular rusty or - yellow patches. Trilobites - and brachiopods. - (530) - MIDDLE CAMBRIAN GROS VENTRE FORMATION - PARK SHALE MEMBER Gray-green shale containing - (220 feet) beds of platy limestone - conglomerate. Trilobites, - brachiopods, and fossil algal - heads. - DEATH CANYON Two thick beds of - LIMESTONE MEMBER dark-blue-gray limestone - (285 feet) separated by 15 to 20 feet of - shale that locally contains - abundant fossil brachiopods - and trilobites. - WOLSEY SHALE MEMBER Soft greenish-gray shale - (100 feet) containing beds of purple and - green sandstone near base. A - few fossil brachiopods. - FLATHEAD LIMESTONE (175 Brown, maroon, and white - feet) sandstone, locally containing - many rounded pebbles of - quartz and feldspar. Some - beds of green shale at top. - (570) - PRECAMBRIAN Granite, gneiss, and - pegmatite. - - [Illustration: Figure 34. _Absolute ages of the formations in Alaska - Basin. Shaded parts of the scale show intervals for which there is - no record._] - - STRATIGRAPHIC SCALE ABSOLUTE ENLARGED PIECE OF - TIME (Years YARDSTICK SHOWN ON - ago) FIGURE 19 - - 2 - PALEZOIC PENNSYLVANIAN ? - 300 million - MISSISSIPPIAN MADISON - DEVONIAN DARBY - 3 - 400 million - SILURIAN - ORDOVICIAN BIGHORN - 500 million 4 - CAMBRIAN GALLATIN - GROS VENTRE - FLATHEAD - 600 million - PRECAMBRIAN 5 - - Figure 35. _The first invasions of the Paleozoic sea._ - - [Illustration: A. _In Early Cambrian time an arm of the Pacific - Ocean occupied a deep trough in Idaho, Nevada, and part of Utah. The - land to the east was a broad gently rolling plain of Precambrian - rocks drained by sluggish westward-flowing streams. The site of the - Teton Range was part of this plain. Slow subsidence of the land - caused the sea to move eastward during Middle Cambrian time flooding - the Precambrian plain._] - - [Illustration: B. _By Late Cambrian time the sea had drowned all of - Montana and most of Wyoming. The Flathead Sandstone and Gros Ventre - Formation were deposited as the sea advanced. The Gallatin Limestone - was being deposited when the shoreline was in about the position - shown in this drawing._] - - [Illustration: C. _In Early Ordovician time uplift of the land - caused the sea to retreat back into the trough, exposing the - Cambrian deposits to erosion. Cambrian deposits were partly stripped - off of some areas. The Bighorn Dolomite was deposited during the - next advance of the sea in Middle and Late Ordovician time._] - - [Illustration: Figure 36. _Conglomeratic basal bed of Flathead - Sandstone and underlying Precambrian granite gneiss; contact is - indicated by a dark horizontal line about 1 foot below hammer. This - contact is all that is left to mark a 2-billion year gap in the rock - record of earth history. The locality is on the crest of the Teton - Range 1 mile northwest of Lake Solitude._] - -Once again the shoreline crept eastward, the seas cleared, and the -Gallatin Limestone was deposited. The Gallatin, like the Death Canyon -Limestone Member, was laid down for the most part in quiet, clear water, -probably at depths of 100 to 200 feet. However, a few beds of “edgewise” -conglomerate indicate the occurrence of sporadic storms. At this time, -the sea covered all of Idaho and Montana and most of Wyoming (fig. 35B) -and extended eastward across the Dakotas to connect with shallow seas -that covered the eastern United States. Soon after this maximum stage -was reached slow uplift caused the sea to retreat gradually westward. -The site of the Teton Range emerged above the waves, where, as far as is -now known, it may have been exposed to erosion for nearly 70 million -years (fig. 35C). - -The above historical summary of geologic events in Cambrian time is -recorded in the Cambrian formations. This is an example of the -reconstructions, based on the sedimentary rock record, that have been -made of the Paleozoic systems in this area. - - Figure 37. _Cambrian fossils in Grand Teton National Park._ - - A-B. _Phosphatic-shelled brachiopods, the oldest fossils found in - the park. Actual width of specimens is about ¼ inch._ - - C-D. _Trilobites. Width of C is ¼ inch, D is ½ inch. National Park - Service photos by W. E. Dilley and R. A. Mebane._ - - [Illustration: A.] - - [Illustration: B.] - - [Illustration: C.] - - [Illustration: D.] - - - Younger Paleozoic formations - -Formations of the remaining Paleozoic systems are likewise of interest -because of the ways in which they differ from those already described. - - Figure 38. _Distinctive features of Cambrian rocks._ - - [Illustration: A. _Algal heads in the Park Shale Member of the Gros - Ventre Formation. These calcareous mounds were built by algae - growing in a shallow sea in Cambrian time. They are now exposed on - the divide between North and South Leigh Creeks, nearly 2 miles - above sea level!_] - - [Illustration: B. _Bed of “edgewise” conglomerate in the Gallatin - Limestone. Angular plates of solidified lime-ooze were torn from the - sea bottom by storm waves, swept into depressions, and then buried - in lime mud. These fragments, seen in cross section, make the - strange design on the rock. Thin limestone beds below are - undisturbed. National Park Service photo by W. E. Dilley._] - -The Bighorn Dolomite of Ordovician age forms ragged hard massive -light-gray to white cliffs 100 to 200 feet high (figs. 32 and 33). -_Dolomite_ is a calcium-magnesium carbonate, but the original sediment -probably was a calcium carbonate mud that was altered by magnesium-rich -sea water shortly after deposition. Corals and other marine animals were -abundant in the clear warm seas at this time. - -Dolomite in the Darby Formation of Devonian age differs greatly from the -Bighorn Dolomite; that in the Darby is dark-brown to almost black, has -an oily smell, and contains layers of black, pink, and yellow mudstone -and thin sandstone. The sea bottom during deposition of these rocks was -foul and frequently the water was turbid. Abundant fossil fragments -indicate fishes were common for the first time. Exposures of the Darby -Formation are recognizable by their distinctive dull-yellow thin-layered -slopes between the prominent gray massive cliffs of formations below and -above. - -The Madison Limestone of Mississippian age is 1,000 feet thick and is -exposed in spectacular vertical cliffs along canyons in the north, west, -and south parts of the Tetons. It is noted for the abundant remains of -beautifully preserved marine organisms (fig. 39). The fossils and the -relatively pure blue-gray limestone in which they are embedded indicate -deposition in warm tranquil seas. The beautiful Ice Cave on the west -side of the Tetons and all other major caves in the region were -dissolved out of this rock by underground water. - -The Pennsylvanian System is represented by the Amsden Formation and the -Tensleep Sandstone. Cliffs of the Tensleep Sandstone can be seen along -the Gros Ventre River at the east edge of the park. The Amsden, below -the Tensleep, consists of red and green shale, sandstone, and thin -limestone. The shale is especially weak and slippery when exposed to -weathering and saturated with water. These are the strata that make up -the glide plane of the Lower Gros Ventre Slide (fig. 5) east of the -park. - -The Phosphoria Formation and its equivalents of Permian age are unlike -any other Paleozoic rocks because of their extraordinary content of -uncommon elements. The formation consists of sandy dolomite, widespread -black phosphate beds and black shale that is unusually rich not only in -phosphorus, but also in vanadium, uranium, chromium, zinc, selenium, -molybdenum, cobalt, and silver. The formation is mined extensively in -nearby parts of Idaho and in Wyoming for phosphatic fertilizer, for the -chemical element phosphorus, and for some of the metals that can be -derived from the rocks as byproducts. These elements and compounds are -not everywhere concentrated enough to be of economic interest, but their -dollar value is, in a regional sense, comparable to that of some of the -world’s greatest mineral deposits. - - Figure 39. _A glimpse of the sea floor during deposition of the - Madison Limestone 330 million years ago, showing the remains of - brachiopods, corals, and other forms of life that inhabited the - shallow warm water._ - - [Illustration: A. _Slab in which fossils are somewhat broken and - scattered. Scale slightly reduced. National Park Service photo by W. - E. Dilley and R. A. Mebane._] - - [Illustration: B. _Slab in which fossils are remarkably complete. - Silver dollar gives scale. Specimen is in University of Wyoming - Geological Museum._] - - - - - THE MESOZOIC—ERA OF TRANSITION - - -The Mesozoic Era in the Teton region was a time of alternating marine, -transitional, and continental environments. Moreover, the highly -diversified forms of life, ranging from marine mollusks to tremendous, -land-living dinosaurs, confirm and reinforce the story of the rocks. -Living things, too, were in transition, for as environment changed, many -forms moved from the sea to land in order to survive. It was the time -when some of the most spectacularly colored rock strata of the region -were deposited. - - - Colorful first Mesozoic strata - -Bright-red soft Triassic rocks more than 1,000 feet thick, known as the -Chugwater Formation, comprise most of the basal part of the Mesozoic -sequence (table 4). They form colorful hills east and south of the park. -The red color is caused by a minor amount of iron oxide. Mud cracks and -the presence of fossil reptiles and amphibians indicate deposition in a -tidal flat environment, with the sea lying several miles southwest of -Jackson Hole. A few beds of white _gypsum_ (calcium sulfate) are -present; they were apparently deposited during evaporation of shallow -bodies of salt water cut off from the open sea. - -As the Triassic Period gave way to the Jurassic, salmon-red windblown -sand (Nugget Sandstone) spread across the older red beds and in turn was -buried by thin red shale and thick gypsum deposits of the Gypsum Spring -Formation. Then down from Alaska and spreading across most of Wyoming -came the _Sundance Sea_, a warm, muddy, shallow body of water that -teemed with marine mollusks. In it more than 500 feet of highly -fossiliferous soft gray shale and thin limestones and sandstones were -deposited. The sea withdrew and the Morrison and Cloverly Formations -(Jurassic and Lower Cretaceous) were deposited on low-lying tropical -humid flood plains. These rocks are colorful, consisting of red, pink, -purple, and green badland-forming claystones and mudstones, and yellow -to buff sandstones. Vegetation was abundant and large and small -dinosaurs roamed the countryside or inhabited the swamps. - - [Illustration: Table 4.—Mesozoic sedimentary rocks exposed in the - Teton region.] - - Age Formation Thickness Description Where exposed - (feet) - - CRETACEOUS - Harebell 0-5,000 Sandstone, olive Eastern and - Formation drab, silty, drab northeastern parts - siltstone, and of Jackson Hole. - dark-gray shale; - thick beds of - quartzite pebble - conglomerate in - upper part. - Meeteetse 0-700 Sandstone, gray to Spread Creek area. - Formation chalky white, - blue-green to gray - siltstone, thin - coal, and green to - yellow bentonite. - Mesaverde 0-1,000 Sandstone, white, Eastern Jackson - Formation massive, soft, thin Hole. - gray shale, sparse - coal. - Unnamed 3,500± Sandstone and Eastern Jackson - sequence of shale, gray to Hole and eastern - lenticular brown; abundant margin of the park. - sandstone, coal in lower 2,000 - shale, and feet. - coal. - Bacon Ridge 900-1,200 Sandstone, light Eastern Jackson - Sandstone gray, massive, Hole and eastern - marine, gray shale, margin of the park. - many coal beds. - Cody Shale 1,300-2,200 Shale, gray, soft; Eastern and - thin green northern parts of - sandstone, some Jackson Hole. - bentonite; marine. - Frontier 1,000 Sandstone, gray, Eastern and - Formation and black to gray northern parts and - shale, marine; many south-western - persistent white margin of Jackson - bentonite beds in Hole. - lower part. - Mowry Shale 700 Shale, Gros Ventre River - silvery-gray, hard, Valley, northern - siliceous, with margin of the park, - many fish scales; and southern part - thin bentonite of Jackson Hole. - beds; marine. - Thermopolis 150-200 Shale, black, soft, Gros Ventre River - Shale fissile, with Valley, northern - persistent margin of the park, - sandstone at top; and southern part - marine. of Jackson Hole. - Cloverly and 650 Sandstone, light North end of Teton - Morrison(?) gray, sparkly, Range and Gros - Formations rusty near top, Ventre River Valley. - underlain by - variegated soft - claystone; basal - part is silty - dully-variegated - sandstone and - claystone. - JURASSIC - Sundance 500-700 Sandstone, green, North end of Teton - Formation underlain by soft Range, Blacktail - gray shale and thin Butte, Gros Ventre - highly River Valley. - fossiliferous - limestones; marine. - Gypsum Spring 75-100 Gypsum, white, North end of Teton - Formation interbedded with Range, Blacktail - red shale and gray Butte, Gros Ventre - dolomite; partly River Valley. - marine. - Nugget 0-350 Sandstone, North flank of Gros - Sandstone salmon-red, hard. Ventre Mountains, - southern Jackson - Hole. - TRIASSIC - Chugwater 1,000-1,500 Siltstone and North flank of Gros - Formation shale, red, Ventre Mountains, - thin-bedded; one north end of Teton - thin marine Range, southernmost - limestone in upper Jackson Hole. - third. - Dinwoody 200-400 Siltstone, brown, North flank of Gros - Formation hard, thin-bedded; Ventre Mountains, - marine. north end of Teton - Range, southernmost - Jackson Hole. - - - Drab Cretaceous strata - -The youngest division of the _Mesozoic_ Era is the Cretaceous Period. -Near the beginning of this period, brightly colored rocks continued to -be deposited. Then, the Teton region, as well as most of Wyoming, was -partly, and at times completely, submerged by shallow muddy seas. As a -result, the brightly variegated strata were covered by 10,000 feet of -generally drab-colored sand, silt, and clay containing some coal beds, -volcanic ash layers, and minor amounts of gravel. - -The Cretaceous sea finally retreated eastward from the Teton region -about 85 million years ago, following the deposition of the Bacon Ridge -Sandstone (fig. 40). As it withdrew, extensive coal swamps developed -along the sea coast. The record of these swamps is preserved in coal -beds 5 to 10 feet thick in the Upper Cretaceous deposits. The coal beds -are now visible in abandoned mines along the east margin of the park. -Coal is formed from compacted plant debris; about 5 feet of this -material is needed to form 1 inch of coal. Thus, lush vegetation must -have flourished for long periods of time, probably in a hot wet climate -similar to that now prevailing in the Florida Everglades. - -Sporadically throughout Cretaceous time fine-grained ash was blown out -of volcanoes to the west and northwest and deposited in quiet shallow -water. Subsequently the ash was altered to a type of clay called -_bentonite_ that is used in the foundry industry and in oil well -drilling muds. In Jackson Hole, the elk and deer lick bentonite -exposures to get a bitter salt and, where the beds are water-saturated, -enjoy “stomping” on them. Bentonite swells when wet and causes many -landslides along access roads into Jackson Hole (fig. 17). - -The Cretaceous rocks in the Teton region are part of an enormous -east-thinning wedge that here is nearly 2 miles thick. Most of the -debris was derived from slowly rising mountains to the west. - -Cretaceous sedimentary rocks are much more than of just scientific -interest; they contain mineral deposits important to the economy of -Wyoming and of the nation. Wyoming leads the States in production of -bentonite, all of it from Cretaceous rocks. These strata have yielded -far more oil and gas than any other geologic system in the State and the -production is geographically widespread. They also contain enormous coal -reserves, some in beds between 50 and 100 feet thick. The energy -resources alone of the Cretaceous System in Wyoming make it invaluable -to our industrialized society. - - [Illustration: Figure 40. _The yardstick and the sea. The shaded - part of the yardstick shows the 500-million-year interval during - which Paleozoic and Mesozoic seas swept intermittently across the - future site of the Tetons. When they finally withdrew about 85 - million years ago, a little more than 5/8 of an inch of the - yardstick remained to be accounted for._] - - ABSOLUTE TIME (Millions of years ago) INCHES - - {submerged} 85-585 ⅝-4⅝ - CENOZOIC 0-80 0-½ - MESOZOIC 80-180 ½-⅞ - PALEOZOIC 180-570 ⅞-4⅞ - PRECAMBRIAN 570- 4⅞- - -As the end of the Cretaceous Period approached, slightly more than 80 -million years ago, the flat monotonous landscape (fig. 41) which had -prevailed during most of Late Cretaceous time gave little hint that the -stage was set for one of the most exciting and important chapters in the -geologic history of North America. - - - Birth of the Rocky Mountains - -The episode of mountain building that resulted in formation of the -ancestral Rocky Mountains has long been known as the _Laramide -Revolution_. West and southwest of Wyoming, mountains had already -formed, the older ones as far away as Nevada and as far back in time as -Jurassic, the younger ones rising progressively farther east, like giant -waves moving toward a coast. The first crustal movement in the Teton -area began in latest Cretaceous time when a broad low northwest-trending -arch developed in the approximate area of the present Teton Range and -Gros Ventre Mountains. However, this uplift bore no resemblance to the -Tetons as we know them today for the present range formed 70 million -years later. - - [Illustration: Figure 41. _Grand Teton National Park region slightly - more than 80 million years ago, just before onset of Laramide - Revolution. The last Cretaceous sea still lingered in central - Wyoming._] - -One bit of evidence (there are others) of the first Laramide mountain -building west of the Tetons is a tremendous deposit of quartzite boulder -debris (several hundred cubic miles in volume) derived from the _Targhee -uplift_ (fig. 42). Nowhere is the uplift now exposed, but from the size, -composition, and distribution of rock fragments that came from it, we -know that it was north and west of the northern end of the present-day -Teton Range. Powerful streams carried boulders, sand, and clay eastward -and southeastward across the future site of Jackson Hole and deposited -them in the Harebell Formation (table 4). Mingled with this sediment -were tiny flakes of gold and a small amount of mercury. Fine-grained -debris was carried still farther east and southeast into two enormous -depositional troughs in central and southern Wyoming. Most of the large -rock fragments were derived from Precambrian and possibly lower -Paleozoic quartzites. This means that at least 15,000 feet of overlying -Paleozoic and Mesozoic strata must first have been stripped away from -the Targhee uplift before the quartzites were exposed to erosion. - - [Illustration: Figure 42. _Teton region at the end of Cretaceous - time about 65 million years ago. The ancestral Teton-Gros Ventre - uplift had risen and prominent southeastward drainage from the - Targhee uplift was well established. See figure 41 for State lines - and location map._] - -Remains of four-legged horned ceratopsian dinosaurs, possibly -_Triceratops_ (fig. 43), reflecting the last population explosion of -these reptiles, have been found in pebbly sandstone of the Harebell -Formation in highway cuts on the Togwotee Pass road 8 miles east of the -park. - - [Illustration: Figure 43. _Triceratops, a horned dinosaur of the - type that inhabited Jackson Hole about 65 million years ago. Sketch - by S. H. Knight._] - -Near the end of Cretaceous time, broad gentle uplifts also began to stir -at the sites of future mountain ranges in many parts of Wyoming. The -ancestral Teton-Gros Ventre arch continued to grow. Associated with and -parallel to it was a series of sharp steepsided elongated -northwest-trending upfolds (_anticlines_). One of these can be seen -where it crosses the highway at the Lava Creek Campground near the -eastern margin of Grand Teton National Park. - -During these episodes of mountain building, erosion, and deposition, the -dinosaurs became extinct all over the world. The “Age of Mammals” was -about to begin. - - - - - TERTIARY—TIME OF MAMMALS, MOUNTAINS, LAKES, AND VOLCANOES - - - [Illustration: Figure 44. _The last inch of the yardstick, enlarged - to show subdivisions of the Cenozoic Era._] - - STRATIGRAPHIC SCALE THE LAST INCH OF ABSOLUTE TIME (million - THE YARDSTICK years ago) - - CENOZOIC - QUATERNARY - Recent and 0 0 - Pleistocene - TERTIARY - Pliocene 0 0 - Miocene ⅛ 12 - Oligocene ¼ 25 - Eocene ⅜ 40 - Paleocene ⁷/₁₆ 55 - MESOZOIC - CRETACEOUS ½ 65 - -The Cenozoic (table 1), last and shortest of the geologic eras, -comprises the Tertiary and Quaternary Periods. It began about 65 million -years ago and is represented by only the final one-half inch of our -imaginary yardstick of time (fig. 19). Nevertheless, it is the era -during which the Tetons rose in their present form and the landscape was -sculptured into the panorama of beauty that we now see. In order to show -the many Tertiary and Quaternary events in the Teton region, it is -necessary to enlarge greatly the last part of the yardstick (fig. 44). -There are two reasons for the extraordinarily clear and complete record. -First, the Teton region was a relatively active part of the earth’s -crust, characterized by many downdropped blocks. The number of events is -great and their records are preserved in sediments trapped in the -subsiding basins. Second, the geologically recent past is much easier to -see than the far dimmer, distant past; the rocks that record later -events are fresher, less altered, more complete, and more easily -interpreted than are those that tell us of older events. - - [Illustration: Table 5.—Cenozoic sedimentary rocks and - unconsolidated deposits in the Teton region.] - - Age Formation Thickness Description Where exposed - (feet) - - QUATERNARY - Recent - Modern 0-200± Sand, gravel, and Floor of Jackson - stream, silt along present Hole and in canyons - landslide, streams; jumbled and on - glacial and broken rock in mountainsides - talus deposits landslides and on throughout the - talus slopes; region. - debris around - existing glaciers. - Pleistocene - Glacial 0-200± Gravel, sand, silt, Floor of Jackson - deposits and and glacial debris. Hole. - loess - Unnamed upper 0-500 Shale, brown-gray, Gros Ventre River - lake sequence sandstone, and Valley. - conglomerate. - Unnamed lower 0-200 Shale, siltstone, National Elk Refuge. - lake sequence and sandstone, - gray, green, and - red. - ? Pleistocene or Pliocene - Bivouac 0-1,000 Conglomerate, with Signal Mountain and - Formation purplish-gray West Gros Ventre - welded tuff in Butte. - upper part. - TERTIARY - Pliocene - Teewinot 0-6,000 Limestone, tuff, National Elk - Formation and claystone, Refuge, Blacktail - white, soft. Butte, and eastern - margin of Antelope - Flat. - Camp Davis 0-5,500 Conglomerate, red Southernmost tip of - Formation and gray, with Jackson Hole. - white tuff, - diatomite, and red - and white claystone. - Miocene - Colter 0-7,000 Volcanic Pilgrim and Ditch - Formation conglomerate, tuff, Creeks, and north - and sandstone, end of Teton Range. - white to - green-brown, with - locally-derived - basalt and andesite - rock fragments. - Oligocene - Wiggins 0-3,000 Volcanic Eastern margin of - Formation conglomerate, gray Jackson Hole. - to brown, with - white tuff layers. - Eocene - Unnamed upper 0-1,000 Tuff, conglomerate, Eastern margin of - and middle sandstone, and Jackson Hole. - Eocene claystone, green, - sequence underlain by - variegated - claystone and - quartzite pebble - conglomerate. - Wind River 2,000-3,000 Claystone and Eastern margin of - and Indian sandstone, Jackson Hole. - Meadows variegated, and - Formations locally-derived - conglomerate; - persistent coal and - gray shale zone in - middle. - Paleocene - Unnamed 1,000-2,000 Sandstone and Eastern margin of - greenish-gray claystone, Jackson Hole. - and brown greenish-gray and - sandstone and brown, - claystone intertonguing at - sequence base with quartzite - pebble conglomerate. - Pinyon 500-5,000 Conglomerate, Eastern part of - Conglomerate brown, chiefly of Jackson Hole, Mt. - rounded quartzite; Leidy and Pinyon - coal and claystone Peak Highlands, and - locally at base. north end of Teton - Range. - - [Illustration: Figure 45. _Pinyon Conglomerate of Paleocene age, - along the northwest margin of the Teton Range._] - -During the early part of the Tertiary Period, mountain building and -basin subsidence were the dominant types of crustal movement. Seas -retreated southward down the Mississippi Valley and never again invaded -the Teton area. Environments on the recently uplifted land were diverse -and favorable for the development of new forms of plants and animals. - - - Rise and burial of mountains - -The enormous section of Tertiary sedimentary rocks in the Jackson Hole -area (table 5) is one of the most impressive in North America. If the -maximum thicknesses of all formations were added, they would total more -than 6 miles, but nowhere did this amount of rock accumulate in a single -unbroken sequence. No other region in the United States contains a -thicker or more complete nonmarine Tertiary record; many areas have -little or none. The accumulation in Jackson Hole reflects active uplifts -of nearby mountains that supplied abundant rock debris, concurrent -sinking of nearby basins in which the sediments could be preserved, and -proximity to the great Yellowstone-Absaroka volcanic area, one of the -most active continental volcanic fields in the United States. The volume -and composition of the Tertiary strata are, therefore, clear evidence of -crustal and subcrustal instability. - - [Illustration: Figure 46. _Teton region near end of deposition of - Paleocene rocks, slightly less than 60 million years ago. The - ancestral Teton-Gros Ventre uplift formed a partial barrier between - the Jackson Hole and Green River depositional basins; major - drainages from the Targhee uplift spread an enormous sheet of gravel - for 100 miles to the east. See figure 41 for State lines and - location map._] - -The many thick layers of conglomerate are evidence of rapid erosion of -nearby highlands. The Pinyon Conglomerate (fig. 45), for example, -contains zones as much as 2,500 feet thick of remarkably well-rounded -pebbles, cobbles, and boulders, chiefly of quartzite identical with that -in the underlying Harebell Formation and derived from the same source, -the Targhee uplift. Like the Harebell the matrix contains small amounts -of gold and mercury. Rock fragments increase in size northwestward -toward the source area (fig. 46) and most show percussion scars, -evidence of ferocious pounding that occurred during transport by -powerful, swift rivers and steep gradients. - - [Illustration: Figure 47. _Teton region at climax of Laramide - Revolution, between 50 and 55 million years ago. See figure 41 for - State lines and location map._] - -Conglomerates such as the Pinyon are not the only clue to the time of -mountain building. Another type of evidence—faults—is demonstrated in -figure 16. The youngest rocks cut by a fault are always older than the -fault. Many faults and the rocks on each side are covered by still -younger unbroken sediments. These must, therefore, have been deposited -after fault movement ceased. By dating both the faulted and the -overlying unbroken sediments, the time of fault movement can be -bracketed. - -Observations of this type in western Wyoming indicate that the Laramide -Revolution reached a climax during earliest Eocene time, 50 to 55 -million years ago. Mountain-producing upwarps formed during this episode -were commonly bounded on one side by either reverse or thrust faults -(fig. 16B and 16C) and intervening blocks were downfolded into large, -very deep basins. The amount of movement of the mountain blocks over the -basins ranged from tens of miles in the Snake River, Salt River, -Wyoming, and Hoback Ranges directly south of the Tetons to less than 5 -miles on the east margin of Jackson Hole (the west flank of the Washakie -Range shown in figure 1). The ancestral Teton-Gros Ventre uplift -continued to rise but remained one of the less conspicuous mountain -ranges in the region (fig. 47). - -The Buck Mountain fault, the great reverse fault which lies just west of -the highest Teton peaks (see geologic map and cross section), was formed -either at this time or during a later episode of movement that also -involved the southwest margin of the Gros Ventre Mountains. The Buck -Mountain fault is of special importance because it raised a segment of -Precambrian rocks several thousand feet. Later, when the entire range as -we now know it was uplifted by movement along the Teton fault, the hard -basement rocks in this previously upfaulted segment continued to stand -much higher than those in adjacent parts of the range. All of the major -peaks in the Tetons are carved from this doubly uplifted block. - -The brightly colored sandstone, mudstone, and claystone in the Indian -Meadows and Wind River Formations (lower Eocene) in the eastern part of -Jackson Hole were derived from variegated Triassic, Jurassic, and Lower -Cretaceous rocks exposed on the adjacent mountain flanks. Fossils in -these Eocene Formations show that it took less than 10 million years for -the uplifts to be deeply eroded and partially buried in their own -debris. - -The Laramide Revolution in the area of Grand Teton National Park ended -during Eocene time between 45 and 50 million years ago, and as the -mountains and basins became stabilized a new element was added. -Volcanoes broke through to the surface in many parts of the -Yellowstone-Absaroka area and the constantly increasing volume of their -eruptive debris was a major factor in the speed of filling of basins and -burial of mountains throughout Wyoming. This entire process only took -about 20 million years, and along the east margin of Jackson Hole it was -largely completed during Oligocene time (fig. 48). However, east and -northeast of Jackson Lake a Miocene downwarp subsequently formed and in -it accumulated at least 7,000 feet of locally derived sediments of -volcanic origin. - - [Illustration: Figure 48. _Teton region near the close of Oligocene - deposition, between 25 and 30 million years ago, showing areas of - major volcanoes and lava flows. See figure 41 for State lines and - location map._] - - - The First Big Lake - -_Teewinot Lake_ (fig. 49), the first big freshwater lake in Jackson -Hole, was formed during Pliocene time, about 10 million years ago, and -in it the Teewinot Formation was deposited. These lake strata consist of -more than 5,000 feet of white limestone, thin-bedded claystone, and -_tuff_ (solidified ash made up of tiny fragments of volcanic rock and -splinters of volcanic glass). The claystones contain fossil snails, -clams, beaver bones and teeth, aquatic mice, suckers, and other fossils -that indicate deposition in a shallow freshwater lake environment. These -beds underlie Jackson Lake Lodge, the National Elk Refuge, part of -Blacktail Butte, and are conspicuously exposed in white outcrops that -look like snowbanks on the upper slopes along the east margin of the -park across the valley from the Grand Teton. - - [Illustration: Figure 49. _Teton region near close of middle - Pliocene time, about 5 million years ago, showing areas of major - volcanoes and lava flows. See figure 41 for State lines and location - map._] - -Teewinot Lake was formed on a down-faulted block and was dammed behind -(north of) a fault that trends east across the floor of Jackson Hole at -the south boundary of the park. Lakes are among the most short-lived of -earth features because the forces of nature soon conspire to fill them -up or empty them. This lake existed for perhaps 5 million years during -middle Pliocene time; it was shallow, and remained so despite the -pouring in of a mile-thick layer of sediment. This indicates that -downdropping of the lake floor just about kept pace with deposition. - - [Illustration: Figure 50. _Restoration of a middle Eocene landscape - showing some of the more abundant types of mammals. Mural painting - by Jay H. Matterness; photo courtesy of the Smithsonian - Institution._] - - _Uintatherium_ 6-horned, saber-toothed plant eater - _Stylinodon_ gnawing-toothed mammal - _Palaeosyops_ early titanothere - _Helaletes_ primitive tapir - _Sciuravus_ squirrel-like rodent - _Smilodectes_ lemurlike monkey - _Trogosus_ gnawing-toothed mammal - _Hyrachyus_ fleet-footed rhinoceros - _Ischyrotomus_ marmotlike rodent - _Homacodon_ even-toed hoofed animal - _Orohippus_ ancestral horse - _Patriofelis_ large flesh eater - _Mesonyx_ hyenalike mammal - _Helohyus_ even-toed hoofed mammal - _Metacheiromys_ armadillolike edentate - _Machaeroides_ saber-toothed mammal - _Hyopsodus_ clawed, plant-eating mammal - _Saniwa_ monitorlike lizard - _Crocodilus_ crocodile - _Echmatemys_ turtle - -Other lakes formed in response to similar crustal movements in nearby -places. One such lake, _Grand Valley Lake_ (fig. 49), formed about 25 -miles southwest of Teewinot Lake; both contained sediments with nearly -the same thickness, composition, appearance, age, and fossils. Although -these two lakes are on opposite sides of the Snake River Range, the -ancestral Snake River apparently flowed through a canyon previously cut -across the range and provided a direct connection between them. - - - Development of mammals - -The Cenozoic Era is known as the “Age of Mammals.” Small mammals had -already existed, though quite inconspicuously, in Wyoming for about 90 -million years before Paleocene time. Then about 65 million years ago -their proliferation began as a result of the extinction of dinosaurs, -obliteration of seaways that were barriers to distribution, and the -development of new and varied types of environment. These new -environments included savannah plains, low hills and high mountains, -freshwater lakes and swamps, and extensive river systems. The mammals -increased in size and, for the first time, became abundant in numbers of -both species and individuals. The development and widespread -distribution of grasses and other forage on which many of the animals -depended were highly significant. Successful adaptation of _herbivores_ -(vegetation-eating animals) led, in turn, to increased varieties and -numbers of predatory _carnivores_ (meat-eating animals). - -During early Eocene time, coal swamps formed in eastern Jackson Hole and -persisted for thousands of years, as is shown by 60 feet of coal in a -single bed at one locality. Continuing on into middle Eocene time, the -climate was subtropical and humid, and the terrain was near sea level. -Tropical breadfruits, figs, and magnolias flourished along with a more -temperate flora of redwood, hickory, maple, and oak. Horses the size of -a dog and many other small mammals were abundant. Primates, thriving in -an ideal forest habitat, were numerous. Streams contained gar fish and -crocodiles (fig. 50). - - [Illustration: Figure 51. _A typical Oligocene landscape showing - some of the more abundant types of mammals. Mural painting by Jay H. - Matterness; photo courtesy of Smithsonian Institution._] - - _Trigonias_ early rhinoceros - _Perchoerus_ early peccary - _Mesohippus_ 3-toed horse - _Aepinacodon_ remote relative of hippopotamus - _Archaeotherium_ giant piglike mammal - _Protoceras_ bizarre horned ruminant - _Hesperocyon_ ancestral dog - _Hyracodon_ small fleet-footed rhinoceros - _Poëbrotherium_ ancestral camel - _Hypisodus_ very small chevrotainlike ruminant - _Ictops_ small insect-eating mammal - _Brontotherium_ titanothere - _Protapirus_ ancestral tapir - _Glyptosaurus_ extinct lizard - _Hoplophoneus_ saber-toothed cat - _Subhyracodon_ early rhinoceros - _Merycoidodon_ sheeplike grazing mammal - _Hyaenodon_ archaic hyenalike mammal - _Hypertragulus_ chevrotainlike ruminant - -Early in the Oligocene Epoch, between 30 and 35 million years ago, the -climate in Jackson Hole became cooler and drier, and the subtropical -plants gave way to the warm temperate flora of oak, beech, maple, alder, -and ash. The general land surface rose higher above sea level, perhaps -by accumulation of several thousand feet of Oligocene volcanic rocks -(fig. 52) rather than by continental uplift. _Titanotheres_ (large -four-legged mammals with the general size and shape of a rhinoceros) -flourished in great numbers for a few million years and then abruptly -vanished. Horses by now were about the size of a very small modern colt. -Rabbits, rodents, carnivores, tiny camels, and other mammals were -abundant in Jackson Hole, and the fauna, surprisingly, was essentially -the same as that 500 miles to the east, at a much lower elevation, on -the plains of Nebraska and South Dakota (fig. 51). - -The Miocene Epoch (15 to 25 million years ago) was the time of such -intense volcanic activity in the Teton region that animals must have -found survival very difficult. A few skeletons and fragmentary parts of -camels about the size of a small horse and other piglike animals called -_oreodonts_ comprise our only record of mammals; nothing is known of the -plants. Farther east the climate fluctuated from subtropical to warm -temperate, gradually becoming cooler toward the end of the epoch. - -Fossils in the Pliocene lake deposits (8 to 10 million years old; see -description of Teewinot Formation) include shallow-water types of -snails, clams, diatoms, and ostracodes, as well as beavers, mice, -suckers, and frogs. Pollen in these beds show that adjacent upland areas -supported fir, spruce, pine, juniper, sage, and other trees and shrubs -common to the area today. Therefore, the climate must have been much -cooler than in Miocene time. No large mammals of Pliocene age have been -found in Jackson Hole. The record of life during Quaternary time is -discussed later. - - [Illustration: Figure 52. _Layers of volcanic conglomerate separated - by thin white tuff beds in Wiggins Formation. These cliffs, on the - north side of Togwotee Pass, are about 1,100 feet high and represent - a cross section of part of the enormous blanket of waterlaid debris - that spread south and east from the Yellowstone-Absaroka volcanic - area. These and younger deposits from the same general source filled - the basins and almost completely buried the mountains in this part - of Wyoming._] - - - Volcanoes - -Volcanoes are one of the most interesting parts of the geologic story of -the Teton region. Although ash from distant volcanoes had settled in -northwestern Wyoming at least as far back in time as Jurassic, the first -nearby active volcanoes (since the Precambrian) erupted in the -Yellowstone-Absaroka region during the early Eocene, about 50 million -years ago. From then on, the volcanic area grew in size and the violence -of eruptions and volume of debris increased until Pliocene time. This -debris had a profound influence on the color and composition of the -sediments and on the environment and types of plants and animals. - -The color of the volcanic rocks and the sediments derived from them -varies significantly from one epoch to another. For example, the middle -Eocene rocks are white to light-green, red, and purple, upper Eocene are -dark-green, Oligocene are light-gray, white, and brown, Miocene are -dark-green, brown, and gray, and Pliocene are white to red-brown. - - [Illustration: Figure 53. _Air oblique view south, showing the north - end of the Teton Range disappearing beneath Pleistocene lava flows. - Light-colored bare area at lower left is vertical Paleozoic - limestone surrounded on three sides by nearly horizontal rhyolite - lava flows. Bare slope at lower right is west-dipping Pinyon - Conglomerate, also overlapped by lava. Grand Teton is on right - skyline and Mt. Moran is rounded summit on middle skyline._] - -As mentioned earlier, it is probable that the vast outpouring of -volcanic rocks during late Tertiary time in the Teton region and to the -north and northeast is directly related to the subsidence of Jackson -Hole and the rise of the Tetons. - -The spectacular banded cliffs of the Wiggins Formation on both sides of -Togwotee Pass (fig. 52) and farther north in the Absaroka Range are -remnants of Oligocene volcanic conglomerate and tuff that once spread as -a blanket several thousand feet thick across eastern Jackson Hole and -partially or completely buried the nearby older folded mountain ranges. - - [Illustration: Figure 54. _Obsidian, a volcanic glass less than 10 - million years old, especially prized by Indians who used it for - spear and arrow points and for tools._] - -About 25 million years ago, with the start of the Miocene Epoch, -volcanic vents opened up within, and along the borders of, Grand Teton -National Park. Major centers of eruption were at the north end of the -Teton Range, east of Jackson Lake, and south of Spread Creek. They -emitted a prodigious amount of volcanic ash and fragments of congealed -lava. For example, adjacent to one vent a mile in diameter, about 4 -miles north-northeast of Jackson Lake Lodge, is a continuous section, -7,000 feet thick, of waterlaid strata derived in large part from this -volcanic source. These sedimentary rocks comprise the Colter Formation -which is darker colored and contains more iron and magnesium than the -Wiggins Formation. The site of deposition at this locality was a -north-trending trough that represented an early stage in the downwarping -of Jackson Hole. - -Pliocene volcanoes erupted in southern and central Yellowstone Park. The -volcanoes emitted viscous, frothy, pinkish-gray and brown lava called -_rhyolite_. This is an extrusive igneous rock that has the same -composition as granite, but is much finer grained. In several places, -lava apparently flowed into the north end of Teewinot Lake, chilled -suddenly, and solidified into a black volcanic glass called _obsidian_. -Because it chips easily into thin flakes having a smooth surface, -obsidian was prized by the Indians, who used it for spear and arrow -points (fig. 54). Some of this obsidian has a potassium-argon date of 9 -million years. - - [Illustration: Figure 55. _East face of Signal Mountain showing - Bivouac Formation (upper Pliocene or Pleistocene). Tilted ledge is - rhyolitic welded tuff 2.5 million years old, and slopes above and - below it are conglomerate. National Park Service photo by W. E. - Dilley._] - -After Teewinot Lake was filled with sediment, the floor of Jackson Hole -became a flat boulder-covered surface. Nearby vents erupted heavy fiery -clouds of gaseous molten rock that rolled across this plain and then -congealed into hard layers with the general appearance of lava flows. -Under a microscope, however, the rock is seen to be made up of -compressed fragments of glass that matted down and solidified when the -clouds stopped moving. This kind of rock is called a _welded tuff_. One -of these forms the conspicuous ledge in the Bivouac Formation on the -north and east sides of Signal Mountain (fig. 55), and is especially -important because it has a potassium-argon date of 2.5 million years. -More of this _welded tuff_ flowed southward from Yellowstone National -Park, engulfed the north end of the Teton Range (fig. 53), and continued -southward along the west side of the mountains for 35 miles and along -the east side for 25 miles. - - [Illustration: Figure 56. _The final 3 million years on our - yardstick of time, enlarged to show approximate dates of major - events._] - - THE LAST HUNDREDTHS ABSOLUTE TIME IMPORTANT EVENTS - OF AN INCH OF THE (Years ago) - YARDSTICK - 0 0 Last glaciation followed by - faulting - ¹/₁₀₀₀ 50000 Second glaciation - ²/₁₀₀₀ 100000 ?—First glaciation - ⁶/₁₀₀₀ 700000 ?—Second Quaternary lake - ⁸/₁₀₀₀ 1 million ?—Tilting and faulting of - southern part of Jackson Hole - ¹¹/₁₀₀₀ 1.3 million ?—First Quaternary lake - ¹²/₁₀₀₀ 1.5 million } Complex series of volcanic - eruptions in southern Jackson - Hole - ¹⁵/₁₀₀₀ 1.9 million } - ¹⁶/₁₀₀₀ 2 million ?—Development of Hoback - normal fault - ²/₁₀₀ 2.5 million Eruption of welded tuff in - Bivouac Formation - ²⁴/₁₀₀₀ 3 million - - - - - QUATERNARY—TIME OF ICE, MORE LAKES, AND CONTINUED CRUSTAL DISTURBANCE - - -The Quaternary Period is represented by less than 15-thousandths of the -last inch on our yardstick of time (fig. 56) and the entire Ice Age -takes up less than 2-thousandths of an inch (less than the thickness of -this page). Nevertheless, the spectacular effects of various forces of -nature on the Teton landscape during this short interval of time are of -such significance that they warrant a separate discussion. The role of -glaciers in carving the rugged Teton peaks and shaping the adjacent -valleys was mentioned in the first part of this booklet, but is -discussed in more detail here. The magnitude and complexity of crustal -movements increased during the final 2 million years of time—so much so -that the beginning of Quaternary time has not yet been identified with -any single event. Figure 56 shows the major events described below. - - - Hoback normal fault - -The _Hoback normal fault_, 30 miles long, with a mile or more -displacement, developed in the southernmost part of Jackson Hole about 2 -million years ago. This fault is on the east side of the valley. Thus, -the valley block was downdropped between this fault and the Teton fault -that borders the west side. - - - Volcanic activity - -During or shortly after major movement on the Hoback fault, and perhaps -related to it, there was a complex series of volcanic eruptions west and -north of the town of Jackson, along the south boundary of the park. In -rapid succession, lavas of many types, with a combined thickness of more -than 1,000 feet, were extruded and volcanic plugs intruded into the -near-surface sedimentary rocks. These volcanic rocks can be seen on the -East and West Gros Ventre Buttes. - -There are no active volcanoes in the Teton region today and no -postglacial lava flows or cinder cones. Five miles north of Grand Teton -National Park are boiling springs (Flagg Ranch hot springs) that are -associated with the youngest (late Quaternary) lavas in southern -Yellowstone Park. Elsewhere in Jackson Hole are a number of lukewarm -springs but their relation to volcanic rocks has not been determined. - -What happened to the vast thicknesses of volcanic debris? We know they -existed because sections of them have been measured on the eroded edges -of uptilted folds and fault blocks. Many cubic miles of these rocks are -now buried beneath the floor of Jackson Hole, but a much greater volume -was carried completely out of the region by water, ice, and wind during -the final chapter of geologic history. - - - Preglacial lakes - -Remnants of two sets of lake deposits in Jackson Hole record preglacial -events in Quaternary time. Downdropping of southern Jackson Hole along -the Hoback and Teton faults blocked the southwestward drainage of the -Snake River, and a new lake formed overlapping and extending south of -the site of the long-vanished Teewinot Lake. Incorporated in the lake -sediments are fragments of lava like that in nearby Quaternary flows. -From this we know that the lake formed after at least some of the lava -was emplaced. Apparently subsidence was more rapid than filling, for a -time, at least, because this new lake was deep. Fossil snails preserved -in olive-drab to gray fine-grained claystone overlying lava flows at the -north end of East Gros Ventre Butte are the kind now living at depths of -120 to 300 feet in Lake Tahoe, California-Nevada. Near the margins of -the lake, pink and green claystone and soft sandstone were deposited. -The duration of this lake is not known but it lasted long enough for 200 -feet of beds to accumulate. Subsequent faulting and warping destroyed -the lake, left tilted remnants of the beds perched 1,000 feet up on the -east side of Jackson Hole, and permitted the Snake River to reestablish -its course across the mountains to the southwest. - -Later downdropping of Jackson Hole impounded a second preglacial lake. -Little is known about its extent because nearly everywhere the soft -brown and gray shale, claystone, and sandstone deposited in it were -scooped out and washed away during subsequent glaciations. A few -remnants of the lake deposits are preserved in protected places, -however; two are within the Gros Ventre River Valley—one downstream from -Lower Slide Lake about a mile east of the park and the other 4 miles -farther east. The latter remnant is nearly 500 feet thick and the upper -half is largely very fine grained shale and claystone. This fine texture -suggests that the lake existed for a good many thousand years, for such -deposits commonly accumulate more slowly than coarser grained debris. - - [Illustration: Figure 57. _Map showing extent and direction of - movement of first and largest ice sheet. See figure 41 for State - lines and location map._] - - - The Ice Age - -With the uplift of the Teton Range and the formation of Jackson Hole -late in Cenozoic time the landscape gradually began to assume the -general outlines that we see today. Rain, wind, snow, and frost shaped -the first crude approximations of the present ridges and peaks. Streams -cut into the rising Teton fault block, eroding the ancestral canyons -deeper and deeper as the uplift continued. The most recent great chapter -in the story of the Teton landscape, however, remained to be written by -the glaciers of the _Ice Age_. - -The reasons for the climatic changes that caused the Ice Age are still a -matter of much scientific debate. Various theories have been advanced -that attribute them to changes in solar radiation, changes in the -earth’s orbit and inclination to the sun, variations in the amount of -carbon dioxide in the atmosphere, shifts in the positions of the -continents or the poles, and to many other factors, but none has met -with universal acceptance. No doubt the explanation lies in some unusual -combination of circumstances, for widespread glaciation occurred only -twice before in the earth’s history—once in the late Precambrian and -once during the Permian. It is quite clear, however, that the glaciers -did not form in response to any local cause such as the uplift of the -Teton Range, for concurrent climatic changes and ice advance took place -throughout many parts of the world. - -At least three times in the last 250,000 years glaciers from the -surrounding highlands invaded Jackson Hole. The oldest and most -widespread glaciation probably took place about 200,000 years ago; it -was called the _Buffalo Glaciation_ by Prof. Eliot Blackwelder in 1915 -(see selected references). The age estimate is based on measurements of -the thickness of the decomposed layer on the surface of obsidian pebbles -in the glacial debris. Major sources of ice were the Beartooth Mountains -(fig. 1), the Absaroka Range, and the Wind River Range. The Gros Ventre -Mountains and Teton Range furnished lesser amounts of ice. - -The ice from the Beartooth and Absaroka centers of ice accumulation -converged in the northeastern part of Grand Teton National Park and -flowed south along the face of the Teton Range in a giant stream that in -many places was 2,000 feet thick (fig. 57). All but the highest parts of -the Pinyon Peak and Mount Leidy Highlands were buried and scoured. -Signal Mountain, Blacktail Butte, and the Gros Ventres Buttes were -overridden and shaped by ice at this time. Another glacier, this one -from the Wind River Range, flowed northwest along the Continental -Divide, then down the Gros Ventre River Valley, and merged with the -southward-moving main ice stream west of Lower Slide Lake. Where Jackson -Hole narrows southward, the glacier became more and more confined, but -nevertheless flowed all the way through the Snake River Canyon and on -into Idaho. - - [Illustration: Figure 58. _Glacial deposits, outwash, and loess - exposed along Boyle Ditch in Jackson Hole National Elk Refuge. - Indicated are middle Pliocene Teewinot formation (A), oldest till - (B), Bull Lake outwash gravel (C), and post-Bull Lake loess (D), - which here contains snail shells dated by Carbon-14 as 15,000 years - old. Height of cliff is about 30 feet._] - -The volume of this great ice mass was probably considerably more than -1,000 cubic miles. When it melted, nearly all the previously accumulated -soil in Jackson Hole was washed away and a pavement of quartzite -boulders mantled much of the glaciated surface. In areas not -subsequently glaciated, the lack of soil and abundance of quartzite -boulders drastically influenced the topography, later drainage, -distribution of all types of vegetation, especially conifers and grass, -and the pattern of human settlement and industry. - - [Illustration: Figure 59. _View west from the Snake River overlook - showing at upper right the Burned Ridge moraine (with trees) merging - southward with the highest (oldest) Pinedale outwash plain. The next - lower surface is composed of outwash from the Jackson Lake moraine - which lies to the right, out of the picture. At the bottom is - Deadman’s Bar, a gravel deposit at the present river level. Photo by - H. D. Pownall._] - -The second glaciation, named _Bull Lake_, was less than half as -extensive as the first. A large tongue of ice from the Absaroka center -of accumulation flowed down the Buffalo River Valley and joined ice from -the Tetons on the floor of Jackson Hole. An enormous outwash fan of -quartzite boulders extended from near Blacktail Butte southward -throughout most of southern Jackson Hole. Glaciers in the Gros Ventre -Mountains did not advance beyond the east margin of the valley floor. -Carbon-14 ages and data from weathered obsidian pebbles suggest that -this glaciation took place between 35,000 and 80,000 years ago. - -Bull Lake moraines and outwash deposits are overlain directly in the -southern part of Jackson Hole by fine silt, rather than by deposits of -the third glaciation (fig. 58). This silt, of windblown origin, is -called _loess_ and contains fossil shells dated by Carbon-14 as between -13,000 and 19,000 years old. Wherever the loess occurs, it is marked by -abundant modern coyote dens and badger burrows. - - [Illustration: Figure 60. _Air oblique view west toward the Teton - Range, showing effects of Pinedale Glaciation on the landscape. Mt. - Moran is at top left; the mountain front is broken by U-shaped - valleys from which ice emerged into the area now occupied by Jackson - Lake. The timbered area bordering Jackson Lake is the Jackson Lake - moraine. One of the braided outlet channels breaching the Jackson - Lake moraine can be seen crossing the outwash plain at the left - center. Lakes at lower right occupy “potholes” near where the - 9,000-year-old snail shells occur. Snake River is in foreground. - Photo by R. L. Casebeer._] - -The third and last glaciation, named the _Pinedale_, was even less -extensive than the others. Nevertheless it was of great importance for -it added the final touches to the present landscape. The jagged -intricately ice-carved peaks (fig. 4) and the glittering lakes and broad -gravelly plains are vivid reminders of this recent chapter in geologic -history. - -Pinedale glaciers advanced down Cascade, Garnet, Avalanche, and Death -Canyons and spilled out onto the floor of Jackson Hole, where they built -the outermost loops of the conspicuous terminal moraines that now -encircle Jenny, Bradley, Taggart, and Phelps Lakes (fig. 13). Ice -streams from Glacier Gulch and Open Canyon also left prominent moraines -on the valley floor, but these do not contain lakes. Ice from Leigh -Canyon and all of the eastward-draining valleys to the north combined to -form a large glacier in roughly the present position of Jackson Lake. -This ice entirely surrounded Signal Mountain, leaving only the upper few -hundred feet projecting as an island or _nunatak_. - - [Illustration: Figure 61. _The Pinedale Glaciers in the central part - of Jackson Hole as they might have appeared at the time the Jackson - Lake moraine was built. Solid color areas are lakes; dark irregular - pattern shows areas of moraine deposited during the maximum advance - of the Pinedale Glaciers. Pattern of open circles shows older - Pinedale outwash plains; pattern of fine dots shows outwash plains - built at the time the glaciers were in the positions shown in the - drawing. Coarser dots near the margins of the glaciers represent - concentrations of rock debris in the ice._] - -The southernmost major advance of Pinedale ice from Jackson Lake is -marked by a series of densely timbered moraines that cross the Snake -River Valley. This series is collectively named the _Burned Ridge -moraine_ (fig. 61). Extending southward for 10 miles from this moraine -is a remarkably flat surfaced gravelly outwash deposit. It was spread by -streams that poured from the glacier at the time the moraine was being -built (fig. 59). East of the Snake River, the main highway from a point -just north of Blacktail Butte to the Snake River overlook is built on -this flat untimbered surface. We assume that the outwash is younger than -15,000 years because it apparently overlies loess of that age. - -The glacier withdrew rapidly northward from the Burned Ridge moraine, -leaving behind many large irregular masses of stagnant, debris-covered -ice. The sites of these became kettles, locally known as “The Potholes” -(fig. 12). The main glacier retreated to a position marked by the loop -of moraines just south of Jackson Lake (fig. 60). Figure 61 is a sketch -map showing how the glaciers in this part of Jackson Hole might have -appeared at the time the Jackson Lake moraine was built. - -Abundant snail shells have been found in lake sediments in the bottoms -of the kettles north of the Burned Ridge moraine (fig. 60) as well as on -low ridges between them. Carbon-14 age determinations indicate that the -snails lived about 9,000 years ago, either in a lake already present -before the Pinedale ice advanced and formed the Burned Ridge moraine or -in ponds that filled kettles left as the ice melted behind this moraine. - -In either case, the shells indicate that the Pinedale glaciers probably -existed on the floor of Jackson Hole as recently as 9,000 years ago, at -a time when Indians were already living in the area. We can easily -imagine the fascination with which these primitive peoples may have -watched as year after year the glaciers wasted away, slowly retreating -back into the canyons, then withdrawing into the sheltered recesses of -the high mountains, eventually to dwindle and disappear. - -Many bits of evidence, both from North America and Europe, indicate that -there was a period called the _climatic optimum_ about 6,000 years ago -when the climate was significantly warmer and drier than at present. We -suspect, though there is as yet no direct proof, that the Pinedale -glaciers wasted away entirely during this interval. - -The modern pattern of vegetation in Jackson Hole is strongly influenced -by the distribution of Pinedale glacial moraines and outwash deposits. -Almost without exception the moraines are heavily forested, whereas the -nearby outwash deposits are covered only by a sparse growth of -sagebrush. This is probably because the moraines contain large amounts -of clay and silt produced by the grinding action of the glaciers. -Material of this type retains water much better and, because of the -greater variety of chemical elements, is more fertile than the porous -quartzite gravel and sand on the outwash plains. - - - Modern glaciers - -About a dozen small rapidly dwindling glaciers exist today in shaded -reentrants high in the Teton Range. They are probably vestiges of ice -masses built up since the climatic optimum, during the so-called -“_Little Ice Age_.” These glaciers, while insignificant compared to -those still present in many other mountain ranges, are fascinating -working models of the great ice streams that shaped the Tetons during -Pleistocene time. - -The Teton Glacier (fig. 6) is one of the best known. It is an ice body -about 3,500 feet long and 1,100 feet wide that lies at the head of -Glacier Gulch, shaded by the encircling ridges of the Grand Teton, Mount -Owen, and Mount Teewinot. Ice in the central part is moving at a rate of -more than 30 feet a year. - - - - - THE PRESENT AND THE FUTURE - - -The geologic story of the Teton country from the time the earth was new -to the present day has been summarized. What can we learn from it? We -become aware that events recorded in the rocks are not a chaotic jumble -of random accidents but came in an orderly, logical succession. We see -the majestic parade of life evolving from simple to complex types, -overcoming all natural disasters, and adapting to ever-changing -environments. We can only speculate as to the motivating force that -launched this fascinating geologic and biologic venture and what the -ultimate goal may be. New facts and new ideas are added to the story -each year, but many unknown chapters remain to be studied; these offer -an irresistible, continuing challenge to inquisitive minds, strong -bodies, and restless, adventurous spirits. - -Most geologic processes that developed the Teton landscape have been -beneficial to man; a few have interfered with his activities, cost him -money, time, effort, and on occasion, his life. Postglacial faulting and -tilting along the southern margin of Grand Teton National Park diverted -drainage systems (such as Flat Creek, southwest of the Flat Creek fault -on the south edge of the geologic map), raised hills, dropped valleys, -and made steep slopes unstable. Flood-control engineers wage a -never-ending struggle to keep the Snake River from shifting to the west -side of Jackson Hole as the valley tilts westward in response to -movement along the Teton fault. Each highway into Jackson Hole has been -blocked by a landslide at one time or another and maintenance of roads -across slide areas requires much ingenuity. We see one slide (the Gros -Ventre) that blocked a river; larger slides have occurred in the past, -and more can be expected. Abundant fresh fault scarps are a constant -reminder that public buildings, campgrounds, dams, and roads need to be -designed to withstand the effects of earthquakes. Some of these problems -have geologic solutions; others can be avoided or minimized as further -study increases our understanding of this region. - -Man appeared during the last one-fiftieth of an inch on our yardstick of -time gone by. In this short span he has had more impact on the earth and -its inhabitants than any other form of life. Will he use wisely the -lessons of the past as a guide while he writes his record on the -yardstick of the future? - - - - - APPENDIX - - - Acknowledgements - -This booklet could not have been prepared without the cooperation and -assistance of many individuals and organizations. We are indebted to the -National Park Service for the use of facilities, equipment, and -photographs, and for the enthusiasm and interest of all of the park -staff. We especially appreciate the cooperation, advice, and assistance -rendered by the late Fred C. Fagergren, former superintendent of Grand -Teton National Park; Willard E. Dilley, former chief park naturalist; -and R. Alan Mebane, former assistant chief park naturalist. - -Profs. Charles C. Bradley and John Montagne of Montana State University -and Bruno J. Giletti of Brown University generously provided us with -unpublished data. Cooperators during the years of background research -were the late Dr. H. D. Thomas, State Geologist of Wyoming, and Dr. D. -L. Blackstone, Jr., Chairman, Department of Geology, University of -Wyoming. - -Helpful suggestions were made by many of our colleagues with the U. S. -Geological Survey; S. S. Oriel, in particular, gave unstintingly of his -time and talents in the review and revision of an early version of the -manuscript. A later version had the further benefit of critical review -by three other people, all experienced in presenting various types of -scientific data to public groups: John M. Good, former chief park -naturalist of Yellowstone National Park; Bryan Harry, former assistant -chief park naturalist of Grand Teton National Park; and Richard Klinck, -“1965 National Teacher of the Year.” - -We are indebted to Ann C. Christiansen, Geologic Map Editor, for advice -and guidance on the illustrations and to R. C. Fuhrmann and his staff -for preparation of many of the line drawings. Block diagrams and photo -artwork were prepared by J. R. Stacy and R. A. Reilly. All photographs -without specific credit lines are by the authors. From the beginning of -the Teton field study to editing and proofing of the final manuscript, -our wives, Jane M. Love and Linda H. Reed, have been enthusiastic and -indispensable participants. - - - Selected references—if you wish to read further - - - Blackwelder, Eliot, 1915, Post-Cretaceous history of the mountains of - central western Wyoming: Jour. Geology, v. 23, p. 97-117, - 193-217, 307-340. - Bradley, F. H., 1873, Report on the geology of the Snake River - district: U.S. Geol. Survey Terr. 6th Ann. Rept. (Hayden), p. - 190-271. - Edmund, R. W., 1951, Structural geology and physiography of the - northern end of the Teton Range, Wyoming: Augustana Library - Pub. 23, 82 p. - Fryxell, F. M., 1930, Glacial features of Jackson Hole, Wyoming: - Augustana Library Pub. 13, 129 p. - ——, 1938, The Tetons, interpretations of a mountain landscape: Univ. - California Press, Berkeley, Calif., 77 p. - Hague, Arnold, 1904, Atlas to accompany U.S. Geol. Survey Monograph 32 - on the geology of Yellowstone National Park. - ——, Iddings, J. P., Weed, W. H., and others, 1899, Geology of the - Yellowstone National Park: U.S. Geol. Survey Monograph 32, Pt. - 2, 893 p. - Harry, Bryan, 1963, Teton trails, a guide to the trails of Grand Teton - National Park: Grand Teton Natural History Association, Moose, - Wyo., 56 p. - Horberg, Leland, 1938, The structural geology and physiography of the - Teton Pass area, Wyoming: Augustana Library Pub. 16, 86 p. - Hurley, P. M., 1959, How old is the earth?: Anchor Books, Garden City, - N. Y., 160 p. - Ortenburger, Leigh, 1965, A climber’s guide to the Teton Range: Sierra - Club, San Francisco, 336 p. - St. John, O. H., 1883, Report on the geology of the Wind River - district: U.S. Geol. Geog. Survey Terr. 12th Ann. Rept. - (Hayden), Pt. 1, p. 173-270. - Wyoming Geological Association, 1956, Guidebook, 11th annual field - conf., Jackson Hole, Wyoming, 1956, Casper, Wyo., 256 p., - incl. sketch maps, diagrams, tables, and illus., also geol. - map, sections, and charts. Composed of a series of individual - papers by various authors. - - - About the authors - -J. D. Love, a native of Wyoming, received his bachelor and master of -arts degrees from the University of Wyoming and his doctor of philosophy -degree from Yale University. His first field season in the Teton -country, in 1933, was financed by the Geological Survey of Wyoming. -After 12 years of geologic work ranging from New England to Utah and -Michigan to Mississippi, he returned to the Teton region. Beginning in -1945, he spent parts or all of 20 field seasons in and near the Tetons. -He compiled the first geologic map of Teton County. He is the senior -author of the geologic map of Wyoming, and author or co-author of more -than 70 other published maps and papers on the geology of Wyoming. In -1961, the University of Wyoming awarded him an honorary doctor of laws -degree for his work on uranium deposits that “led to the development of -the uranium industry in Wyoming.” The Wyoming Geological Association -made him an honorary life member and gave him a special award for his -geologic studies of the Teton area. He is a Fellow of the Geological -Society of America and is active in various other geological -organizations, as well as having been president of the Wyoming Chapters -of Sigma Xi (scientific honorary) and Phi Beta Kappa (scholastic -honorary) societies. - -John C. Reed, Jr., joined the U.S. Geological Survey in 1953 after -receiving his doctor of philosophy degree from the John Hopkins -University. His principal geologic work before coming to the Teton -region was in Alaska and in the southern Appalachians. Beginning in -1961, he spent five field seasons studying and mapping the Precambrian -rocks in Grand Teton National Park, including all the high peaks in the -Teton Range. He is a noted mountaineer, a Fellow of the Geological -Society of America, a member of the Arctic Institute of North America, -and the American Alpine Club. His numerous publications, in addition to -those on the Tetons, describe the geology of mountainous areas in -Alaska, the Appalachians, and Utah. - - - - - Index of selected terms and features - - - _Term_ _Defined or described on page_ - - - A - amphibolite 51 - anticlines 85 - - - B - badlands 14 - bentonite 81 - biotite 51 - brachiopods 70 - Buffalo Glaciation 106 - Bull Lake Glaciation 108 - Burned Ridge moraine 111 - buttes 18 - - - C - Carbon-14 48 - carnivores 95 - chlorite 56 - cirque 30 - climatic optimum 112 - Cordilleran trough 69 - - - D - diabase 59 - dikes 56 - dipping 39 - dolomite 75 - - - E - “edgewise” conglomerate 73 - epochs 46 - eras 46 - erosion 27 - erratics 31 - extrusive igneous rocks 46 - - - F - fault 9 - fault block mountain range 37 - fault scarps 37 - formations 66 - frost wedging 25 - - - G - geologic 10 - glacial striae 30 - gradients 28 - Grand Valley Lake 95 - granite 55 - granite gneiss 54 - groups 47 - gypsum 79 - - - H - herbivores 95 - Hoback normal fault 103 - hole 8 - hornblende 51 - - - I - Ice Age 105 - igneous rocks 46 - intrusive igneous rocks 46 - - - J - Jackson Hole 8 - jade 55 - - - K - kettle 31 - - - L - Laramide Revolution 82 - lateral moraine 30 - layered gneisses 51 - Little Ice Age 112 - loess 108 - - - M - magma 60 - magnetite 52 - marine sedimentary rocks 21 - metamorphic rocks 53 - muscovite 55 - - - N - normal fault 39 - nunatak 111 - - - O - obsidian 101 - oreodonts 97 - outwash 31 - outwash plain 31 - outwash terraces 34 - - - P - pegmatite 56 - period 46 - Pinedale Glaciation 109 - - - Q - quartzite 63 - - - R - reverse fault 39 - rhyolite 100 - rock glaciers 26 - - - S - schist 51 - sedimentary rocks 45 - series 47 - serpentine 55 - “soapstone” 55 - Sundance Sea 79 - systems 46 - - - T - talus 24 - Targhee uplift 83 - Teewinot Lake 92 - terminal moraine 30 - Tetons 8 - Teton fault 37 - thrust fault 39 - timberline 15 - titanothere 97 - treeline 15 - Triceratops 85 - trilobites 70 - tuff 92 - - - W - welded tuff 101 - - - - - The GRAND TETON NATURAL HISTORY ASSOCIATION - - -The Grand Teton Natural History Association assists the National Park -Service in the development of a broad public understanding of the -geology, plant and animal life, history, and related subjects pertaining -to Grand Teton National Park. It aids in the development of museums and -wayside exhibits, offers for sale publications on natural and human -history, and cooperates with the Government in the interest of Grand -Teton National Park. - -_Mail orders_: For a publication list, write the Grand Teton Natural -History Association, Moose, Wyoming 83012. - - _Creative Director_: Century III Advertising. Inc. - _Designer_: Les Hays Studios, Inc. - _Color Separations_—_Assembly_—_Plates_: Orent Graphic Arts, Inc. - _Type_: Bodoni and Gothic - _Printer_: Omaha Printing Co. - _Printing_: Offset Lithography. - Six Colors on Covers - Two Colors on Body - - [Illustration: GEOLOGIC MAP OF GRAND TETON NATIONAL PARK] - - [Illustration: EXPLANATION] - - - CENOZOIC - QUATERNARY - Sand, gravel, and talus - _Includes glacial outwash and materials deposited by present - streams_ - Landslide deposits - Moraine deposits of Pinedale glaciers - Moraine deposits of Bull Lake and older glaciers - TERTIARY - Volcanic rocks - _Lava flows and volcanic ash_ - Conglomerate, sandstone, shale, claystone, marl, and pumice - _Deposited on land or in shallow lakes_ - MESOZOIC - Conglomerate, sandstone, shale, and coal - _Deposited on land_ - Shale, sandstone, and limestone - _Mostly deposited in shallow seas_ - PALEOZOIC - Limestone, shale, and sandstone - _Deposited in shallow seas_ - PRECAMBRIAN - Diabase dikes - Granite, gneiss, and schist - Fault - _Dashed where approximately located; dotted where concealed beneath - unfaulted younger deposits. U is on the side that moved up; D, - on the side that moved down_ - Geologic contact - - - [Illustration: View southwest from Lake Solitude toward the Grand - Teton (right), Mt. Owen, and Mt. Teewinot. _Wyoming Travel - Commission photo by J. R. Simon._] - - [Illustration: Grand Teton, Mt. Owen, and Mt. Teewinot from Jenny - Lake Flat. _National Park Service photo by W. E. Dilley._] - - - - - Transcriber’s Notes - - -—Retained publication information from the printed edition: this eBook - is public-domain in the country of publication. - -—Corrected a few palpable typos. - -—Re-arranged text in captions closer to the corresponding image. - -—Expanded ambiguous references to illustrations, _e.g._ “Figure D” to - “Figure 16D” - -—Added one section heading, “The First Big Lake” to match the table of - contents. - -—Included a transcription of the text within some images, with estimated - scale readings from charts. - -—In the text versions only, text in italics is delimited by - _underscores_. - - - - - - - -End of the Project Gutenberg EBook of Creation of the Teton Landscape, by -J. D. Love and John C. 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