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diff --git a/old/3772-h/files/ch15.html b/old/3772-h/files/ch15.html new file mode 100644 index 0000000..c403b70 --- /dev/null +++ b/old/3772-h/files/ch15.html @@ -0,0 +1,1000 @@ +<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> +<!-- saved from url=(0036)http://../Lyell/The Student's Elements of Geology --> +<html> +<head> +<meta name="generator" content="HTML Tidy, see www.w3.org"> +<title>The Student's Elements of Geology: Title</title> +<meta content="text/html; charset=iso-8859-1" http-equiv= +"Content-Type"> +<meta content="MSHTML 5.00.2919.6307" name="GENERATOR"> +<link rel="stylesheet" href="geology.css" type="text/css"> +</head> +<body> +<p><b>The Student’s Elements of Geology</b></p> + +<hr> +<p class="page"><a name="page 230">[ 230 ]</a></p> + +<p> </p> + +<center><b>Chapter XV</b><br> +<br> +LOWER MIOCENE <small>(OLIGOCENE OF BEYRICH)</small>.</center> + +<p class="intro">Lower Miocene Strata of France. — Line +between Miocene and Eocene. — Lacustrine Strata of Auvergne. +— Fossil mammalia of the Limagne d’Auvergne. — +Lower Molasse of Switzerland. — Dense Conglomerates and +Proofs of Subsidence. — Flora of the Lower Molasse. — +American Character of the Flora. — Theory of a Miocene +Atlantis. — Lower Miocene of Belgium. — Rupelian Clay +of Hermsdorf near Berlin. — Mayence Basin. — Lower +Miocene of Croatia. — Oligocene Strata of Beyrich. — +Lower Miocene of Italy. — Lower Miocene of England. — +Hempstead Beds. — Bovey Tracey Lignites in Devonshire. +— Isle of Mull Leaf-Beds. — Arctic Miocene Flora. +— Disco Island. — Lower Miocene of United States. +— Fossils of Nebraska.</p> + +<p><b>Line between Miocene and Eocene Formations.</b>—The +marine faluns of the valley of the Loire have been already +described as resting in some places on a fresh-water tertiary +limestone, fragments of which have been broken off and rolled on +the shores and in the bed of the Miocene sea. Such pebbles are +frequent at Pontlevoy on the Cher, with hollows drilled in them in +which the perforating marine shells of the Falunian period still +remain. Such a mode of superposition implies an interval of time +between the origin of the fresh-water limestone and its submergence +beneath the waters of the Upper Miocene sea. The limestone in +question forms a part of the formation called the Calcaire de la +Beauce, which constitutes a large table-land between the basins of +the Loire and the Seine. It is associated with marls and other +deposits, such as may have been formed in marshes and shallow lakes +in the newest part of a great delta. Beds of flint, continuous or +in nodules, accumulated in these lakes, and aquatic plants called +Charae, left their stems and seed-vessels imbedded both in the marl +and flint, together with fresh-water and land shells. Some of the +siliceous rocks of this formation are used extensively for +mill-stones. The flat summits or platforms of the hills round +Paris, and large areas in the forest of Fontainebleau, as well as +the Plateau de la Beauce, already alluded to, are chiefly composed +of these fresh-water strata. Next to these in the descending order +are marine sands and sandstone, commonly called the Gres de +Fontainebleau, from which a considerable number of shells, very +distinct from those of the faluns, have been obtained at Etampes, +south of</p> + +<p> </p> + +<hr> +<p class="page"><a name="page 231">[ 231 ]</a></p> + +<p>Paris, and at Montmartre and other hills in Paris itself, or in +its suburbs. At the bottom of these sands a green clay occurs, +containing a small oyster, <i>Ostrea cyathula,</i> Lam., which, +although of slight thickness, is spread over a wide area. This clay +rests immediately on the Paris gypsum, or that series of beds of +gypsum and gypseous marl from which Cuvier first obtained several +species of Palæotherium and other extinct mammalia.*</p> + +<p>At this junction of the clay and the gypsum the majority of +French geologists have always drawn the line between the Middle and +Lower Tertiary, or between the Miocene and Eocene formations, +regarding the Fontainebleau sands and the <i>Ostrea cyathula</i> +clay as the base of the Miocene, and the gypsum, with its mammalia, +as the top of the Eocene group. I formerly dissented from this +division, but I now find that I must admit it to be the only one +which will agree with the distribution of the Miocene mammalia, +while even the mollusca of the Fontainebleau sands, which were +formerly supposed to present at preponderance of affinities to an +Eocene fauna, have since been shown to agree more closely with the +fossils of certain deposits always regarded as Middle Tertiary at +Mayence and in Belgium. In fact, we are now arriving at that stage +of progress when the line, wherever it be drawn between Miocene and +Eocene, will be an arbitrary one, or one of mere convenience, as I +shall have an opportunity of showing when the Upper Eocene +formations in the Isle of Wight are described in the sixteenth +chapter.</p> + +<p><b>Lower Miocene of Central France.</b>—Lacustrine strata, +belonging, for the most part, to the same Miocene system as the +Calcaire de la Beauce, are again met with farther south in +Auvergne, Cantal, and Vélay. They appear to be the monuments +of ancient lakes, which, like some of those now existing in +Switzerland, once occupied the depressions in a mountainous region, +and have been each fed by one or more rivers and torrents. The +country where they occur is almost entirely composed of granite and +different varieties of granitic schist, with here and there a few +patches of Secondary strata, much dislocated, and which have +suffered great denudation. There are also some vast piles of +volcanic matter, the greater part of which is newer than the +fresh-water strata, and is sometimes seen to rest upon them, while +a small part has evidently been of contemporaneous origin. Of these +igneous rocks I shall treat more particularly in the sequel.</p> + +<p>The study of these regions possesses a peculiar interest very +distinct in kind from that derivable from the investigation</p> + +<p class="fnote">* Bulletin, 1856, Journ., vol. xii, p. 768.</p> + +<p> </p> + +<hr> +<p class="page"><a name="page 232">[ 232 ]</a></p> + +<p>either of the Parisian or English Tertiary areas. For we are +presented in Auvergne with the evidence of a series of events of +astonishing magnitude and grandeur, by which the original form and +features of the country have been greatly changed, yet never so far +obliterated but that they may still, in part at least, be restored +in imagination. Great lakes have disappeared—lofty mountains have +been formed, by the reiterated emission of lava, preceded and +followed by showers of sand and scoriæ—deep valleys have +been subsequently furrowed out through masses of lacustrine and +volcanic origin—at a still later date, new cones have been thrown +up in these valleys—new lakes have been formed by the damming up +of rivers—and more than one assemblage of quadrupeds, birds, and +plants, Eocene, Miocene, and Pliocene, have followed in succession; +yet the region has preserved from first to last its geographical +identity; and we can still recall to our thoughts its external +condition and physical structure before these wonderful +vicissitudes began, or while a part only of the whole had been +completed. There was first a period when the spacious lakes, of +which we still may trace the boundaries, lay at the foot of +mountains of moderate elevation, unbroken by the bold peaks and +precipices of Mont Dor, and unadorned by the picturesque outline of +the Puy de Dome, or of the volcanic cones and craters now covering +the granitic platform. During this earlier scene of repose deltas +were slowly formed; beds of marl and sand, several hundred feet +thick, deposited; siliceous and calcareous rocks precipitated from +the waters of mineral springs; shells and insects imbedded, +together with the remains of the crocodile and tortoise, the eggs +and bones of water-birds, and the skeletons of quadrupeds, most of +them of genera and species characteristic of the Miocene period. To +this tranquil condition of the surface succeeded the era of +volcanic eruptions, when the lakes were drained, and when the +fertility of the mountainous district was probably enhanced by the +igneous matter ejected from below, and poured down upon the more +sterile granite. During these eruptions, which appear to have taken +place towards the close of the Miocene epoch, and which continued +during the Pliocene, various assemblages of quadrupeds successively +inhabited the district, among which are found the genera mastodon, +rhinoceros, elephant, tapir, hippopotamus, together with the ox, +various kinds of deer, the bear, hyæna, and many beasts of +prey which ranged the forest or pastured on the plain, and were +occasionally overtaken by a fall of burning cinders, or buried in +flows of mud, such as accompany volcanic eruptions.</p> + +<p> </p> + +<hr> +<p class="page"><a name="page 233">[ 233 ]</a></p> + +<p>Lastly, these quadrupeds became extinct, and gave place in their +turn to the species now existing. There are no signs, during the +whole time required for this series of events, of the sea having +intervened, nor of any denudation which may not have been +accomplished by currents in the different lakes, or by rivers and +floods accompanying repeated earthquakes, or subterranean +movements, during which the levels of the district have in some +places been materially modified, and perhaps the whole upraised +relatively to the surrounding parts of France.</p> + +<p><i class="2">Auvergne.</i>—The most northern of the +fresh-water groups is situated in the valley-plain of the Allier, +which lies within the department of the Puy de Dome, being the +tract which went formerly by the name of the Limagne +d’Auvergne. The average breadth of this tract is about twenty +miles; and it is for the most part composed of nearly horizontal +strata of sand, sandstone, calcareous marl, clay, and limestone, +none of which observe a fixed and invariable order of +superposition. The ancient borders of the lake wherein the +fresh-water strata were accumulated may generally be traced with +precision, the granite and other ancient rocks rising up boldly +from the level country. The actual junction, however, of the +lacustrine beds and the granite is rarely seen, as a small valley +usually intervenes between them. The fresh-water strata may +sometimes be seen to retain their horizontality within a very +slight distance of the border-rocks, while in some places they are +inclined, and in few instances vertical. The principal divisions +into which the lacustrine series may be separated are the +following:—first, Sandstone, grit, and conglomerate, including red +marl and red sandstone; secondly, Green and white foliated marls; +thirdly, Limestone, or travertin, often oolitic in structure; +fourthly, Gypseous marls.</p> + +<p>The relations of these different groups can not be learnt by the +study of any one section; and the geologist who sets out with the +expectation of finding a fixed order of succession may perhaps +complain that the different parts of the basin give contradictory +results. The arenaceous division, the marls, and the limestone may +all be seen in some places to alternate with each other; yet it can +by no means be affirmed that there is no order of arrangement. The +sands, sandstone, and conglomerate constitute in general a littoral +group; the foliated white and green marl, a contemporaneous central +deposit more than 700 feet thick, and thinly foliated, a character +which often arises from the innumerable thin shells or carapace +valves shed by the small crustacean</p> + +<p> </p> + +<hr> +<p class="page"><a name="page 234">[ 234 ]</a></p> + +<p>called <i>Cypris</i> in the ancient lakes of Auvergne; and +lastly the limestone is for the most part subordinate to the newer +portions of both the above formations.</p> + +<p>It seems that, when the ancient lake of the Limagne first began +to be filled with sediment, no volcanic action had yet produced +lava and scoriæ on any part of the surface of Auvergne. No +pebbles, therefore, of lava were transported into the lake—no +fragments of volcanic rocks imbedded in the conglomerate. But at a +later period, when a considerable thickness of sandstone and marl +had accumulated, eruptions broke out, and lava and tuff were +deposited, at some spots, alternately with the lacustrine strata. +It is not improbable that cold and thermal springs, holding +different mineral ingredients in solution, became more numerous +during the successive convulsions attending this development of +volcanic agency, and thus deposits of carbonate and sulphate of +lime, silex, and other minerals were produced. Hence these minerals +predominate in the uppermost strata. The subterranean movements may +then have continued until they altered the relative levels of the +country, and caused the waters of the lakes to be drained off, and +the further accumulation of regular fresh-water strata to +cease.</p> + +<p><b>Lower Miocene Mammalia of the Limagne.</b>—It is +scarcely possible to determine the age of the oldest part of the +fresh-water series of the Limagne, large masses both of the sandy +and marly strata being devoid of fossils. Some of the lowest beds +may be of Upper Eocene date, although, according to M. Pomel, only +one bone of a <i>Palæotherium</i> has been discovered in +Auvergne. But in Vélay, in strata containing some species of +fossil mammalia common to the Limagne, no less than four species of +Palæothere have been found by M. Aymard, and one of these is +generally supposed to be identical with <i>Palæotherium +magnum,</i> an undoubted Upper Eocene fossil, of the Paris gypsum, +the other three being peculiar.</p> + +<p>Not a few of the other mammalia of the Limagne belong +undoubtedly to genera and species elsewhere proper to the Lower +Miocene. Thus, for example, the Cainotherium of Bravard, a genus +not far removed from the Anoplotherium, is represented by several +species, one of which, as I learn from Mr. Waterhouse, agrees with +<i>Microtherium Renggeri</i> of the Mayence basin. In like manner, +the <i>Amphitragulus elegans</i> of Pomel, an Auvergne fossil, is +identified by Waterhouse with <i>Dorcatherium nanum</i> of Kaup, a +Rhenish species from Weissenau, near Mayence. A small species, +also, of rodent, of the genus Titanomys of H. von Meyer, is common +to the Lower Miocene of Mayence and the Limagne</p> + +<p> </p> + +<hr> +<p class="page"><a name="page 235">[ 235 ]</a></p> + +<p>d’Auvergne, and there are many other points of agreement +which the discordance of nomenclature tends to conceal. A +remarkable carnivorous genus, the Hyænodon of Laizer, is +represented by more than one species. The same genus has also been +found in the Upper Eocene marls of Hordwell Cliff, Hampshire, just +below the level of the Bembridge Limestone, and therefore a +formation older than the Gypsum of Paris. Several species of +opossum (<i>Didelphis</i>) are met with in the same strata of the +Limagne. The total number of mammalia enumerated by M. Pomel as +appertaining to the Lower Miocene fauna of the Limagne and Velay +falls little short of a hundred, and with them are associated some +large crocodiles and tortoises, and some Ophidian and Batrachian +reptiles.</p> + +<p><b>Lower Molasse of Switzerland.</b>—The two upper +divisions of the Swiss Molasse—the one fresh-water, the other +marine—have already been described in the preceding chapter. I +shall now proceed to treat of the third division, which is of Lower +Miocene age. Nearly the whole of this Lower Molasse is fresh-water, +yet some of the inferior beds contain a mixture of marine and +fluviatile shells, the <i>Cerithium margaritaceum,</i> a well-known +Lower Miocene fossil, being one of the marine species. +Notwithstanding, therefore, that some of these Lower Miocene strata +consist of old shingle-beds several thousand feet in thickness, as +in the Rigi, near Lucerne, and in the Speer, near Wesen, mountains +5000 and 7000 feet above the sea, the deposition of the whole +series must have begun at or below the sea-level.</p> + +<p>The conglomerates, as might be expected, are often very unequal +in thickness, in closely adjoining districts, since in a littoral +formation accumulations of pebbles would swell out in certain +places where rivers entered the sea, and would thin out to +comparatively small dimensions where no streams or only small ones +came down to the coast. For ages, in spite of a gradual depression +of the land and adjacent sea-bottom, the rivers continued to cover +the sinking area with their deltas; until finally, the subsidence +being in excess, the sea of the Middle Molasse gained upon the +land, and marine beds were thrown down over the dense mass of +fresh-water and brackish-water deposit, called the Lower Molasse, +which had previously accumulated.</p> + +<p><b>Flora of the Lower Molasse.</b>—In part of the Swiss +Molasse, which belongs exclusively to the Lower Miocene period, the +number of plants has been estimated at more than 500 species, +somewhat exceeding those which were before enumerated as occurring +in the two upper divisions. The Swiss Lower</p> + +<p> </p> + +<hr> +<p class="page"><a name="page 236">[ 236 ]</a></p> + +<p>Miocene may best be studied on the northern borders of the Lake +of Geneva, between Lausanne and Vevay, where the contiguous +villages of Monod and Rivaz are situated. The strata there, which I +have myself examined, consist of alternations of conglomerate, +sandstone, and finely laminated marls with fossil plants. A small +stream falls in a succession of cascades over the harder beds of +pudding-stone, which resist, while the sandstone and plant-bearing +shales and marls give way. From the latter no less than 193 species +of plants have been obtained by the exertions of MM. Heer and +Gaudin, and they are considered to afford a true type of the +vegetation of the Lower Miocene formations of Switzerland—a +vegetation departing farther in its character from that now +flourishing in Europe than any of the higher members of the series +before alluded to, and yet displaying so much affinity to the flora +of Œningen as to make it natural for the botanist to refer +the whole to one and the same Miocene period. There are, indeed, no +less than 81 species of these Older Miocene plants which pass up +into the flora of Œningen.</p> + +<p>This fact is important as bearing on the propriety of classing +the Lower Molasse of Switzerland as belonging to the Miocene rather +than to the latter part of the Eocene period. There are, indeed, so +many types among the fossils, both specific and generic, which have +a wide range through the whole of the Molasse, that a unity of +character is thereby stamped on the whole flora, in spite of the +contrast between the plants of the uppermost and lowest formations, +or between Oeningen and Monod. The proofs of a warmer climate, and +the excess of arborescent over herbaceous plants, and of evergreen +trees over deciduous species, are characters common to the whole +flora, but which are intensified as we descend to the inferior +deposits.</p> + +<p>Nearly all the plants at Monod are contained in three layers of +marl separated by two of soft sandstone. The thickness of the marls +is ten feet, and vegetable matter predominates so much in some +layers as to form an imperfect lignite. One bed is filled with +large leaves of a species of fig (<i>Ficus populina</i>), and of a +hornbeam (<i>Carpinus grandis</i>), the strength of the wind having +probably been great when they were blown into the lake; whereas +another contiguous layer contains almost exclusively smaller +leaves, indicating, apparently, a diminished strength in the wind. +Some of the upper beds at Monod abound in leaves of +Proteaceæ, Cyperaceæ, and ferns, while in some of the +lower ones <i>Sequoia, Cinnamomum,</i> and <i>Sparganium</i> are +common. In one bed of sandstone the trunk of a large palm-tree was +found</p> + +<p> </p> + +<hr> +<p class="page"><a name="page 237">[ 237 ]</a></p> + +<p>unaccompanied by other fossils, and near Vevay, in the same +series of Lower Miocene strata, the leaves of a palm of the genus +<i>Sabal</i> (Fig. 151), a genus now proper to America, were +obtained.</p> + +<img src="../images1/fig151.jpg" width="174" height="226" alt= +"Fig. 151: Sabal major" align="right"> + +<p>Among other genera of the same class is a <i>Flabellaria</i> +occurring near Lausanne, and a magnificent <i>Phœnicites</i> +allied to the date palm. When these plants flourished the climate +must have been much hotter than now. The Alps were no doubt much +lower, and the palms now found fossil in strata elevated 2000 feet +above the sea grew nearly at the sea-level, as is demonstrated by +the brackish-water character of some of the beds into which they +were carried by winds or rivers from the adjoining coast.</p> + +<p>In the same plant-bearing deposits of the Lower Molasse in +Switzerland leaves have been found which have been ascribed to the +order Proteaceæ already spoken of as well represented in the +Œningen beds (see <a href="ch14.html#page 221">p. 221</a>). +The Proteas and other plants of this family now flourish at the +Cape of Good Hope; while the Banksias, and a set of genera distinct +from those of Africa, grow most luxuriantly in the southern and +temperate parts of Australia. They were probably inhabitants, says +Heer, of dry hilly ground, and the stiff leathery character of +their leaves must have been favourable to their preservation, +allowing them to float on a river for great distances without being +injured, and then to sink, when water-logged, to the bottom. It has +been objected that the fruit of the Proteaceæ is of so tough +and enduring a texture that it ought to have been more commonly met +with; but in the first place we must not forget the numerous cones +found in the Eocene strata of Sheppey, which all admit to be +proteaceous and to belong to at least two species (see <a href= +"ch14.html#page 222">p. 222</a>). Secondly, besides the fruit of +Hakea before mentioned (<a href="ch14.html#page 221">p. 221</a>), +Heer found associated with fossil leaves, having the exact form and +nervation of Banksia, fruit precisely such as may have come from a +cone of that plant, and lately he has received another similar +fruit from the Lower Miocene strata of Lucerne. They may have +fallen out of a decayed cone in the same way as often happens to +the seeds of the spruce fir, <i>Pinus abies,</i> found scattered +over the ground in our woods. It is a known fact that</p> + +<p> </p> + +<hr> +<p class="page"><a name="page 238">[ 238 ]</a></p> + +<p>among the living Proteaceæ the cones are very firmly +attached to the branches, so that the seeds drop out without the +cone itself falling to the ground, and this may perhaps be the +reason why, in some instances in which fossil seeds have been +found, no traces of the cone have been observed.</p> + +<center><img src="../images1/fig152.jpg" width="413" height="236" alt= +"Fig. 152: Fruit of fossil Banksia and leaf of Banksia. Fig. 153: Sequoia Langsdorfii."> +</center> + +<p>Among the Coniferæ the Sequoia here figured is common at +Rivaz, and is one of the most universal plants in the Lowest +Miocene of Switzerland, while it also characterises the Miocene +Brown Coals of Germany and certain beds of the Val d’Arno, +which I have called Older Pliocene, <a href="ch13.html#page 208">p. +208</a>.</p> + +<img src="../images1/fig154.jpg" width="237" height="282" alt= +"Fig. 154: Lastræa stiriaca." align="left"> + +<p>Among the ferns met with in profusion at Monod is the <i> +Lastræa stiriaca,</i> Unger, which has a wide range in the +Miocene period from strata of the age of Œningen to the +lowest part of the Swiss Molasse. In some specimens, as shown in +Fig. 154, the fructification is distinctly seen.</p> + +<p>Among the laurels several species of <i>Cinnamomum</i> are very +conspicuous. Besides the <i>C. polymorphum,</i> before figured, <a +href="ch14.html#page 219">p. 219</a>, another species also ranges +from the Lower to the Upper Molasse of Switzerland, and</p> + +<p> </p> + +<hr> +<p class="page"><a name="page 239">[ 239 ]</a></p> + +<img src="../images1/fig155.jpg" width="183" height="339" alt= +"Fig. 155: Cinnamomum Rossmässleri." align="right"> + +<p>is very characteristic of different deposits of Brown Coal in +Germany. It has been called <i>Cinnamomum Rossmässleri</i> by +Heer (see Fig. 155). The leaves are easily recognised as having two +side veins, which run up uninterruptedly to their point.</p> + +<p><b>American Character of the Flora.</b>—If we consider not +merely the number of species but those plants which constitute the +mass of the Lower Miocene vegetation, we find the European part of +the fossil flora very much less prominent than in the Œningen +beds, while the foreground is occupied by American forms, by +evergreen oaks, maples, poplars, planes, Liquidambar, Robinia, +Sequoia, Taxodium, and ternate-leaved pines. There is also a much +greater fusion of the characters now belonging to distinct +botanical provinces than in the Upper Miocene flora, and we shall +find this fusion still more strikingly exemplified as we go back to +the antecedent Eocene and Cretaceous periods.</p> + +<p>Professor Heer has advocated the doctrine, first advanced by +Unger to explain the large number of American genera in the Miocene +flora of Europe, that the present basin of the Atlantic was +occupied by land over which the Miocene flora could pass freely. +But other able botanists have shown that it is far more probable +that the American plants came from the east and not from the west, +and instead of reaching Europe by the shortest route over an +imaginary Atlantis, migrated in an opposite direction, crossing the +whole of Asia.</p> + +<p><b>Arctic Miocene Flora.</b>—But when we indulge in +speculations as to the geographical origin of the Miocene plants of +Central Europe, we must take into account the discoveries recently +made of a rich terrestrial flora having flourished in the Arctic +Regions in the Miocene period from which many species may have +migrated from a common centre so as to reach the present continents +of Europe, Asia, and America. Professor Heer has examined the +various collections of fossil plants that have been obtained in +North Greenland (lat. 70°), Iceland, Spitzbergen, and other +parts of the Arctic regions,</p> + +<p> </p> + +<hr> +<p class="page"><a name="page 240">[ 240 ]</a></p> + +<p>and has determined that they are of Miocene age and indicate a +temperate climate.* Including the collections recently brought from +Greenland by Mr. Whymper, the Arctic Miocene flora now comprises +194 species, and that of Greenland 137 species, of which 46, or +exactly one-third, are identical with plants found in the Miocene +beds of Central Europe. Considerably more than half the number are +trees, which is the more remarkable since, at the present day, +trees do not exist in any part of Greenland even 10 degrees farther +south.</p> + +<p>More than thirty species of Coniferæ have been found, +including several Sequoias (allied to the gigantic Wellingtonia of +California), with species of Thujopsis and Salisburia now peculiar +to Japan. There are also beeches, oaks, planes, poplars, maples, +walnuts, limes, and even a magnolia, two cones of which have +recently been obtained, proving that this splendid evergreen not +only lived but ripened its fruit within the Arctic circle. Many of +the limes, planes, and oaks were large-leaved species, and both +flowers and fruit, besides immense quantities of leaves, are in +many cases preserved. Among the shrubs were many evergreens, as <i> +Andromeda,</i> and two extinct genera, <i>Daphnogene</i> and <i> +M‘Clintockia,</i> with fine leathery leaves, together with +hazel, blackthorn, holly, logwood, and hawthorn. A species of Zamia +(<i>Zamites</i>) grew in the swamps, with <i>Potamogeton, +Sparganium,</i> and <i>Menyanthes,</i> while ivy and vines twined +around the forest trees and broad-leaved ferns grew beneath their +shade. Even in Spitzbergen, as far north as latitude 78° 56', +no less than ninety-five species of fossil plants have been +obtained, including <i>Taxodium</i> of two species, hazel, poplar, +alder, beech, plane-tree, and lime. Such a vigorous growth of trees +within 12 degrees of the pole, where now a dwarf willow and a few +herbaceous plants form the only vegetation, and where the ground is +covered with almost perpetual snow and ice, is truly +remarkable.</p> + +<p>The identity of so many of the fossils with Miocene species of +Central Europe and Italy not only proves that the climate of +Greenland was much warmer than it is now, but also renders it +probable that a much more uniform climate prevailed over the entire +northern hemisphere. This is also indicated by the whole character +of the Upper Miocene flora of Central Europe, which does not +necessitate a mean temperature very much greater than exists at +present, if we suppose such absence of winter cold as is proper to +insular climates. Professor Heer believes that the mean temperature +of North Greenland must have been at least 30 degrees higher than +at present,</p> + +<p class="fnote">* Heer “Miocene baltische Flora” and +“Fossil-flora von Alaska” 1869.</p> + +<p> </p> + +<hr> +<p class="page"><a name="page 241">[ 241 ]</a></p> + +<p>while an addition of 10 degrees to the mean temperature of +Central Europe would probably be as much as was required. The chief +locality where this wonderful flora is preserved is at Atanekerdluk +in North Greenland (lat. 70°), on a hill at an elevation of +about 1200 feet above the sea. There is here a considerable +succession of sedimentary strata pierced by volcanic rocks. Fossil +plants occur in all the beds, and the erect trunks as thick as a +man’s body which are sometimes found, together with the +abundance of specimens of flowers and fruit in good preservation, +sufficiently prove that the plants grew where they are now found. +At Disco island and other localities on the same part of the coast, +good coal is abundant, interstratified with beds of sandstone, in +some of which fossil plants have also been found, similar to those +at Atanekerdluk.</p> + +<p><img src="../images1/fig156.jpg" width="270" height="120" alt= +"Fig. 156: Leda (Nucula) Deshayesiana." align="right"> <b>Lower +Miocene, Belgium.</b>—The Upper Miocene Bolderberg beds, +mentioned in <a href="ch14.html#page 224">p. 224</a>, rest on a +Lower Miocene formation called the Rupelian of Dumont. This +formation is best seen at the villages of Rupelmonde and Boom, ten +miles south of Antwerp, on the banks of the Scheldt and near the +junction with it of a small stream called the Rupel. A stiff clay +abounding in fossils is extensively worked at the above localities +for making tiles. It attains a thickness of about 100 feet, and +though very different in age, much resembles in mineral character +the “London clay,” containing, like it, septaria or +concretions of argillaceous limestone traversed by cracks in the +interior, which are filled with calc-spar. The shells, referable to +about forty species, have been described by MM. Nyst and De +Koninck. Among them <i>Leda</i> (or Nucula) <i>Deshayesiana</i> +(see Fig. 156) is by far the most abundant; a fossil unknown as yet +in the English tertiary strata, but when young much resembling Leda +amygdaloides of the London Clay proper (see <a href= +"../images1/fig213.jpg">Fig. 213</a>). Among other characteristic +shells are <i>Pecten Hœninghausii,</i> and a species of <i> +Cassidaria,</i> and several of the genus <i>Pleurotoma.</i> Not a +few of these testacea agree with English Eocene species, such as +<i>Actæon simulatus,</i> Sowb, <i>Cancellaria evulsa,</i> +Brander, <i>Corbula pisum</i> (<a href="../images1/fig157.jpg">Fig. +157</a>), and <i>Nautilus (Aturia) ziczac.</i> They are accompanied +by many teeth of sharks, as <i>Lamna contortidens,</i> Ag., <i> +Oxyrhinaxiphodon,</i> Ag., <i>Carcharodon angustidens</i> (see <a +href="../images1/fig196.jpg">Fig. 196</a>),</p> + +<p> </p> + +<hr> +<p class="page"><a name="page 242">[ 242 ]</a></p> + +<p>Ag., and other fish, some of them common to the Middle Eocene +strata.</p> + +<p><i class="2">Kleyn Spawen beds.</i>—The succession of the +Lower Miocene strata of Belgium can be best studied in the environs +of Kleyn Spawen, a village situated about seven miles west of +Maestricht, in the old province of Limburg in Belgium. In that +region, about 200 species of testacea, marine and fresh-water, have +been obtained, with many foraminifera and remains of fish. In none +of the Belgian Lower Miocene strata could I find any nummulites; +and M. d’Archiac had previously observed that these +foraminifera characterise his “Lower Tertiary Series,” +as contrasted with the Middle, and they therefore serve as a good +test of age between Eocene and Miocene, at least in Belgium and the +North of France.* Between the Bolderberg beds and the Rupelian clay +there is a great gap in Belgium, which seems, according to M. +Beyrich, to be filled up in the North of Germany by what he calls +the Sternberg beds, and which, had Dumont found them in Belgium, he +might probably have termed Upper Rupelian.</p> + +<p><b>Lower Miocene of Germany.—</b><i class="2">Rupelian +Clay of Hermsdorf, near Berlin.</i>—Professor Beyrich has +described a mass of clay, used for making tiles, within seven miles +of the gates of Berlin, near the village of Hermsdorf, rising up +from beneath the sands with which that country is chiefly +overspread. This clay is more than forty feet thick, of a dark +bluish-grey colour, and, like that of Rupelmonde, contains +septaria. Among other shells, the <i>Leda Deshayesiana,</i> before +mentioned (Fig. 156), abounds, together with many species of <i> +Pleurotoma, Voluta,</i> etc., a certain proportion of the fossils +being identical in species with those of Rupelmonde.</p> + +<p><i class="2">Mayence Basin.</i>—An elaborate description +has been published by Dr. F. Sandberger of the Mayence tertiary +area, which occupies a tract from five to twelve miles in breadth, +extending for a great distance along the left bank of the Rhine +from Mayence to the neighbourhood of Manheim, and which is also +found to the east, north, and south-west of Frankfort. M. De +Koninck, of Liege, first pointed out to me that the purely marine +portion of the deposit contained many species of shells common to +the Kleyn Spawen beds, and to the clay of Rupelmonde, near Antwerp. +Among these he mentioned <i>Cassidaria depressa, Tritonium +argutum,</i> Brander (<i>T. flandricum,</i> De Koninck), <i> +Tornatella simulata, Aporrhais Sowbyi, Leda Deshayesiana</i> (Fig. +156), <i>Corbula pisum,</i> (Fig. 158) and others.</p> + +<p><b>Lower Miocene Beds of Croatia.</b>—The Brown Coal of +Radaboj,</p> + +<p class="fnote">* D’Archiac Monogr., pp. 79, 100.</p> + +<p> </p> + +<hr> +<p class="page"><a name="page 243">[ 243 ]</a></p> + +<p>near Angram in Croatia, not far from the borders of Styria, is +covered, says Von Buch, by beds containing the marine shells of the +Vienna basin, or, in other words, by Upper Miocene or Falunian +strata. They appear to correspond in age to the Mayence basin, or +to the Rupelian strata of Belgium. They have yielded more than 200 +species of fossil plants, described by the late Professor Unger. +These plants are well preserved in a hard marlstone, and contain +several palms; among them the Sabal, <a href="../images1/fig151.jpg"> +Fig. 151,</a> p. 237, and another genus allied to the date-palm <i> +Phœnicites spectabilis.</i> The only abundant plant among the +Radaboj fossils which is characteristic of the Upper Miocene period +is the <i>Populus mutabilis,</i> whereas no less than fifty of the +Radaboj species are common to the more ancient flora of the Lower +Molasse of Switzerland.</p> + +<center><img src="../images1/fig157.jpg" width="317" height="214" alt= +"Fig. 157: Vanessa Pluto."></center> + +<p>The insect fauna is very rich, and, like the plants, indicates a +more tropical climate than do the fossils of Œningen +presently to be mentioned. There are ten species of Termites, or +white ants, some of gigantic size, and large dragon-flies with +speckled wings, like those of the Southern States in North America; +there are also grasshoppers of considerable size, and even the +Lepidoptera are not unrepresented. In one instance, the pattern of +a butterfly’s wing has escaped obliteration in the marl-stone +of Radaboj; and when we reflect on the remoteness of the time from +which it has been faithfully transmitted to us, this fact may +inspire the reader with some confidence as to the reliable nature +of the characters which other insects of a more durable texture, +such as the beetles, may afford for specific determination. The +Vanessa above figured retains, says Heer, some of its colours, and +corresponds with <i>V. Hadena</i> of India.</p> + +<p> </p> + +<hr> +<p class="page"><a name="page 244">[ 244 ]</a></p> + +<p>Professor Beyrich has made known to us the existence of a long +succession of marine strata in North Germany, which lead by an +almost gradual transition from beds of Upper Miocene age to others +of the age of the base of the Lower Miocene. Although some of the +German lignites called Brown Coal belong to the upper parts of this +series, the most important of them are of Lower Miocene date, as, +for example, those of the Siebengebirge, near Bonn, which are +associated with volcanic rocks.</p> + +<p>Professor Beyrich confines the term “Miocene” to +those strata which agree in age with the faluns of Touraine, and he +has proposed the term “Oligocene” for those older +formations called Lower Miocene in this work.</p> + +<p><b>Lower Miocene of Italy.</b>—In the hills of which the +Superga forms a part there is a great series of Tertiary strata +which pass downward into the Lower Miocene. Even in the Superga +itself there are some fossil plants which, according to Heer, have +never been found in Switzerland so high as the marine Molasse, such +as <i>Banksia longifolia,</i> and <i>Carpinus grandis.</i> In +several parts of the Ligurian Apennines, as at Dégo and +Carcare, the Lower Miocene appears, containing some nummulites, and +at Cadibona, north of Savona, fresh-water strata of the same age +occur, with dense beds of lignite inclosing remains of the <i> +Anthracotherium magnum</i> and <i>A. minimum,</i> besides other +mammalia enumerated by Gastaldi. In these beds a great number of +the Lower Miocene plants of Switzerland have been discovered.</p> + +<p><b>Lower Miocene of England—Hempstead Beds.</b>—We +have already stated that the Upper Miocene formation is nowhere +represented in the British Isles; but strata referable to the Lower +Miocene period are found both in England, Scotland, and Ireland. In +the Hampshire basin these occupy a very small superficial area, +having been discovered by the late Edward Forbes at Hempstead near +Yarmouth, in the northern part of the Isle of Wight, where they are +170 feet thick, and rich in characteristic marine shells. They +overlie the uppermost of an extensive series of Eocene deposits of +marine, brackish, and fresh-water formations, which rest on the +Chalk and terminate upward in strata corresponding in age to the +Paris gypsum, and containing the same extinct genera of quadrupeds, +<i>Palæotherium, Anoplotherium,</i> and others which Cuvier +first described. The following is the succession of these Lower +Miocene strata, most of them exposed in a cliff east of +Yarmouth:</p> + +<p>1. The uppermost or Corbula beds, consisting of marine sands and +clays, contain <i>Voluta Rathieri,</i> a characteristic Lower +Miocene shell; <i>Corbula pisum</i> (Fig. 158), a species common to +the Upper Eocene clay of Barton; Cyrena semistriata (Fig. 159), +several Cerithia, and other shells peculiar to this series.</p> + +<center><img src="../images1/fig158.jpg" width="394" height="341" alt= +"Fig. 158: Corbula pisum. Fig. 159: Cyrena semistriata. Fig. 160: Cerithium plicatum. Fig. 161: Cerithium elegans. Fig. 162: Rissoa Chastelii. Fig. 163: Paludina lenta."> +</center> + +<p>2. Next are fresh-water and estuary marls and carbonaceous clays +in the brackish-water portion of which are found abundantly <i> +Cerithium plicatum,</i> Lam. (Fig. 160), <i>Cerithium elegans</i> +(Fig. 161), and <i>Cerithium tricinctum</i>; also <i>Rissoa +Chastelii</i> (Fig. 162), a very common Kleyn Spawen shell, and +which occurs in each of the four subdivisions of the Hempstead +series down to its base, where it passes into the Bembridge beds. +In the fresh-water portion of the same beds <i>Paludina lenta</i> +(Fig. 163) occurs; a shell identified by some conchologists with a +species now living, <i>P. unicolor</i>; also several species of <i> +Lymneus, Planorbis,</i> and <i>Unio.</i></p> + +<p>3. The next series, or middle fresh-water and estuary marls, are +distinguished by the presence of <i>Melania fasciata, Paludina +lenta,</i> and clays with <i>Cypris</i>; the lowest bed contains +<i>Cyrena semistriata</i> (Fig. 159), mingled with Cerithia and a +<i>panopæa.</i></p> + +<p>4. The lower fresh-water and estuary marls contain <i>Melania +costata,</i> Sowerby, <i>Melanopsis,</i> etc. The bottom bed is +carbonaceous, and called the “Black band,” in which <i> +Rissoa Chastelii</i> (Fig. 162), before alluded to, is common. This +bed contains a mixture of Hempstead shells with those of the +underlying Upper Eocene or Bembridge series. The mammalia,</p> + +<p> </p> + +<hr> +<p class="page"><a name="page 246">[ 246 ]</a></p> + +<p>among which is <i>Hyopotamus bovinus,</i> differ, so far as they +are known, from those of the Bembridge beds. Among the plants, +Professor Heer has recognised four species common to the lignite of +Bovey Tracey, a Lower Miocene formation presently to be described: +namely, <i>Sequoia Couttsiæ,</i> Heer; <i>Andromeda +reticulata,</i> Ettings.; <i>Nelumbium (Nymphœa) doris,</i> +Heer; and <i>Carpolithes Websteri,</i> Brong.* The seed-vessels of +<i>Chara medicaginula,</i> Brong, and <i>C. helicteres</i> are +characteristic of the Hempstead beds generally.</p> + +<p>The <i>Hyopotamus</i> belongs to the hog tribe, or the same +family as the Anthracotherium, of which seven species, varying in +size from the hippopotamus to the wild boar, have been found in +Italy and other part of Europe associated with the lignites of the +Lower Miocene period.</p> + +<p><b>Lignites and Clays of Bovey Tracey, +Devonshire.</b>—Surrounded by the granite and other rocks of +the Dartmoor hills in Devonshire, is a formation of clay, sand, and +lignite, long known to geologists as the Bovey Coal formation, +respecting the age of which, until the year 1861, opinions were +very unsettled. This deposit is situated at Bovey Tracey, a village +distant eleven miles from Exeter in a south-west, and about as far +from Torquay in a north-west direction. The strata extend over a +plain nine miles long, and they consist of the materials of +decomposed and worn-down granite and vegetable matter, and have +evidently filled up an ancient hollow or lake-like expansion of the +valleys of the Bovey and Teign.</p> + +<p>The lignite is of bad quality for economical purposes, as there +is a great admixture in it of iron pyrites, and it emits a +sulphurous odour, but it has been successfully applied to the +baking of pottery, for which some of the fine clays are well +adapted. Mr. Pengelly has confirmed Sir H. De la Beche’s +opinion that much of the upper portion of this old lacustrine +formation has been removed by denudation.†</p> + +<p>At the surface is a dense covering of clay and gravel with +angular stones probably of the Post-pliocene period, for in the +clay are three species of willow and the dwarf birch, <i>Betula +nana,</i> indicating a climate colder than that of Devonshire at +the present day.</p> + +<p>Below this are Lower Miocene strata about 300 feet in thickness, +in the upper part of which are twenty-six beds of lignite, clay, +and sand, and at their base a ferruginous quartzose sand, varying +in thickness from two to twenty-seven</p> + +<p class="fnote">* Pengelly, preface to The Lignite Formation of +Bovey Tracey, p. xvii, London, 1863.<br> +† Philos. Trans., 1863. Paper by W. Pengelly, F.R.S., and +Dr. Oswald Heer.</p> + +<p> </p> + +<hr> +<p class="page"><a name="page 247">[ 247 ]</a></p> + +<p>feet. Below this sand are forty-five beds of alternating lignite +and clay. No shells or bones of mammalia, and no insect, with the +exception of one fragment of a beetle (<i>Buprestis</i>); in a +word, no organic remains, except plants, have as yet been found. +These plants occur in fourteen of the beds—namely, in two of the +clays, and the rest in the lignites. One of the beds is a perfect +mat of the debris of a coniferous tree, called by Heer <i>Sequoia +Couttsiæ,</i> intermixed with leaves of ferns. The same +Sequoia (before mentioned as a Hempstead fossil, p. 246) is spread +through all parts of the formation, its cones, and seeds, and +branches of every age being preserved. It is a species supplying a +link between <i>Sequoia Langsdorfii</i> (see <a href= +"../images1/fig152.jpg">Fig. 153,</a> p. 238) and <i>S. +Sternbergi,</i> the widely spread fossil representatives of the two +living trees <i>S. sempervirens</i> and <i>S. gigantea</i> (or +Wellingtonia), both now confined to California. Another bed is full +of the large rhizomes of ferns, while two others are rich in +dicotyledonous leaves. In all, Professor Heer enumerates forty-nine +species of plants, twenty of which are common to the Miocene beds +of the Continent, a majority of them being characteristic of the +Lower Miocene. The new species, also of Bovey, are allied to plants +of the older Miocene deposits of Switzerland, Germany, and other +Continental countries. The grape-stones of two species of vine +occur in the clays, and leaves of the fig and seeds of a +water-lily. The oak and laurel have supplied many leaves. Of the +triple-nerved laurels several are referred to Cinnamomum. There are +leaves also of a palm of which the genus is not determined. Leaves +also of proteaceous forms, like some of the Continental fossils +before mentioned, occur, and ferns like the well-known <i> +Lastræa stiriaca</i> (<a href="../images1/fig154.jpg">Fig. +154,</a> p. 238), displaying at Bovey, as in Switzerland, its +fructification.</p> + +<p>The croziers of some of the young ferns are very perfect, and +were at first mistaken by collectors for shells of the genus <i> +Planorbis.</i> On the whole, the vegetation of Bovey implies the +existence of a sub-tropical climate in Devonshire, in the Lower +Miocene period.</p> + +<p><b>Scotland: Isle of Mull.</b>—In the sea-cliffs forming +the headland of Ardtun, on the west coast of Mull, in the Hebrides, +several bands of tertiary strata containing leaves of +dicotyledonous plants were discovered in 1851 by the Duke of +Argyll.* From his description it appears that there are three +leaf-beds, varying in thickness from 1½ to 5½ feet, +which are interstratified with volcanic tuff and trap, the whole +mass being about 130 feet in thickness. A sheet of basalt 40 +feet</p> + +<p class="fnote">* Quart. Geol. Journal, 1851, p. 19.</p> + +<p> </p> + +<hr> +<p class="page"><a name="page 248">[ 248 ]</a></p> + +<p>thick covers the whole; and another columnar bed of the same +rock, ten feet thick, is exposed at the bottom of the cliff. One of +the leaf-beds consists of a compressed mass of leaves unaccompanied +by any stems, as if they had been blown into a marsh where a +species of <i>Equisetum</i> grew, of which the remains are +plentifully imbedded in clay.</p> + +<p>It is supposed by the Duke of Argyll that this formation was +accumulated in a shallow lake or marsh in the neighbourhood of a +volcano, which emitted showers of ashes and streams of lava. The +tufaceous envelope of the fossils may have fallen into the lake +from the air as volcanic dust, or have been washed down into it as +mud from the adjoining land. Even without the aid of organic +remains we might have decided that the deposit was newer than the +chalk, for chalk-flints containing cretaceous fossils were detected +by the duke in the principal mass of volcanic ashes or tuff.*</p> + +<p>The late Edward Forbes observed that some of the plants of this +formation resembled those of Croatia, described by Unger, and his +opinion has been confirmed by Professor Heer, who found that the +conifer most prevalent was the <i>Sequoia Langsdorfii</i> (<a href= +"../images1/fig152.jpg">Fig. 153,</a> p. 238), also <i>Corylus +grossedentata,</i> a Lower Miocene species of Switzerland and of +Menat in Auvergne. There is likewise a plane-tree, the leaves of +which seem to agree with those of <i>Platanus aceroides</i> (<a +href="../images1/fig141.jpg">Fig. 141</a>), and a fern which is as yet +peculiar to Mull, <i>Filicites hebridica,</i> Forbes.</p> + +<p>These interesting discoveries in Mull led geologists to suspect +that the basalt of Antrim, in Ireland, and of the celebrated +Giant’s Causeway, might be of the same age. The volcanic +rocks that overlie the chalk, and some of the strata associated +with and interstratified between masses of basalt, contain leaves +of dicotyledonous plants, somewhat imperfect, but resembling the +beech, oak, and plane, and also some coniferæ of the genera +pine and Sequoia. The general dearth of strata in the British +Isles, intermediate in age between the formation of the Eocene and +Pliocene periods, may arise, says Professor Forbes, from the extent +of dry land which prevailed in that vast interval of time. If land +predominated, the only monuments we are likely ever to find of +Miocene date are those of lacustrine and volcanic origin, such as +the Bovey Coal in Devonshire, the Ardtun beds in Mull, or the +lignites and associated basalts in Antrim.</p> + +<p><b>Lower Miocene, United states: Nebraska.</b>—In the +territory of Nebraska, on the Upper Missouri, near the Platte +River, lat. 42° N., a tertiary formation occurs, consisting of +white</p> + +<p class="fnote">* Quart. Geol. Journal, 1851, p. 90.</p> + +<p> </p> + +<hr> +<p class="page"><a name="page 249">[ 249 ]</a></p> + +<p>limestone, marls, and siliceous clay, described by Dr. D. Dale +Owen,* in which many bones of extinct quadrupeds, and of chelonians +of land or fresh-water forms, are met with. Among these, Dr. Leidy +describes a gigantic quadruped, called by him <i>Titanotherium,</i> +nearly allied to the <i>Palæotherium,</i> but larger than any +of the species found in the Paris gypsum. With these are several +species of the genus <i>Oreodon,</i> Leidy, uniting the characters +of pachyderms and ruminants also; <i>Eucrotaphus,</i> another new +genus of the same mixed character; two species of rhinoceros of the +sub-genus <i>Acerotherium,</i> a Lower Miocene form of Europe +before mentioned; two species of <i>Archæotherium,</i> a +pachyderm allied to <i>Chæropotamus</i> and <i> +Hyracotherium</i>; also <i>Pæbrotherium,</i> an extinct +ruminant allied to <i>Dorcatherium,</i> Kaup; also <i> +Agriochoerus,</i> of Leidy, a ruminant allied to <i> +Merycopotamus</i> of Falconer and Cautley; and, lastly, a large +carnivorous animal of the genus <i>Machairodus,</i> the most +ancient example of which in Europe occurs in the Lower Miocene +strata of Auvergne, but of which some species are found in Pliocene +deposits. The turtles are referred to the genus <i>Testudo,</i> but +have some affinity to <i>Emys.</i> On the whole, the Nebraska +formation is probably newer than the Paris gypsum, and referable to +the Lower Miocene period, as above defined.</p> + +<p class="fnote">* David Dale Owen, Geol. Survey of Wisconsin, +etc., Philad., 1852.</p> + +<br> +<hr> +<small><a href="contents.html">Contents</a> / <a href="ch14.html"> +Chapter XIV</a> / <a href="ch16.html">Chapter XVI</a></small> +</body> +</html> + |