Miocene

“ Arctic fossil floras of temperate and, therefore, Miocene aspect are in all probability of Eocene age, and what has been recognized in them as a newer or Miocene facies is due to their having been first studied in Europe in latitudes which only became fit for them in Miocene times. ”

“ Yet we may fairly anticipate that even the most constant types will have undergone some modifications in passing from the Miocene to the Recent epoch, since in the former period the geography and climate of Europe, the height of the Alps, and the general fauna and flora were so different from what they now are. ”

“ In France, the Lower Miocene is represented in Auvergne, Cantal, and Velay, by a great thickness of nearly horizontal strata of sands, sandstone, clays, marls, and limestones, the whole of fresh-water origin. The principal fossils of these lacustrine deposits are Mammalia, of which the remains occur in great abundance. In the valley of the Loire occur the typical European deposits of Upper Miocene age. ”

“ Pliocene of Monte Hermoso. Restored from a skull in the Ameghino collection.
2. Miocene
North America.—Upper Miocene beds cover extensive areas of the Great Plains region and are scattered from Montana far into Mexico. The rich fauna is an outgrowth and development of that of the middle Miocene, with but few immigrant additions and, on the other hand, passes so gradually into that of the lower Pliocene, that any line of separation between them is very difficult to draw. The rodents, numerous as they are among the fossils, are almost certainly very incompletely represented in the collections ”

“ In Greenland, as well as in other parts of the Arctic regions, Miocene strata have been discovered which have yielded a great number of plants, many of which are identical with species found in the European Miocene. ”

“ 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.
Lower Miocene, United states: Nebraska.—In the territory of Nebraska, on the Upper Missouri, near the Platte River, lat. 42° N., a tertiary formation occurs, consisting of white limestone, marls, and siliceous clay, described by Dr. D. Dale Owen, [8] in which many bones of extinct quadrupeds, and of chelonians of land or fresh-water forms, are met with. ”

“ In the mode, therefore, of the succession of its teeth (which, as in all the old-World apes, exactly agree in number with those in man) it differed from the Gorilla and Chimpanzee, and corresponded with the human species.
Upper Miocene Beds of Œningen, in Switzerland.—The faluns of the Loire first served, as already stated (p. 211) , as the type of the Miocene formations in Europe. They yielded a plentiful harvest of marine fossil shells and corals, but were entirely barren of plants and insects. ”

“ It also seems to us that those who hold to the view that man was living in other parts of the world, as Asia, during the Miocene Age, ought readily to admit that a few wandering bands might penetrate into Europe.50 The climate was tropical, there was an abundance of animal life, and, if man was living anywhere, it is very reasonable to suppose that, at some epoch during the course of the Miocene Age, he would have found his way to Europe, unless shut off by the sea. ”

“ In the Miocene deposits, which are next in succession to the Eocene, we begin to find a considerable number, although still a minority, of recent species, intermixed with some fossils common to the preceding epoch. We then arrive at the Pliocene strata, in which species now contemporary with man begin to preponderate, and in the newest of which nine-tenths of the fossils agree with species still inhabiting the neighboring sea. ”

“ Whether or no, traces of human existence will eventually be found in deposits belonging to Miocene, or even earlier, times, I may take this occasion of remarking that the evidence hitherto adduced on this point by continental geologists is, to my mind, after full and careful examination still very far from satisfactory. ”

“ The Faluns are a well-known marine deposit of a shallow sea spread over a great part of Central and Southern France, and identified, beyond a doubt, as Upper Miocene by its shells. The Orleans Sands are another Miocene deposit perfectly characterized by its mammalian fauna, in which the Mastodon Angustidens first appears, with other peculiar species. The Calcaire de Beauce is a solid freshwater limestone formed in the great lake which in the Miocene age occupied the plain of the Beauce and extended into Touraine. ”

“ In the plants of the Older Pliocene strata of the same region we observe a larger proportion of species and genera which, although they may agree with well-known Asiatic or other foreign types, are at present wanting in Italy. If we then examine the Miocene formations of the same country, exotic forms become more abundant, especially the palms, whether they belong to the European or American fan-palms, Chamærops and Sabal, or to the more tropical family of the date-palms or Phœnicites, which last are conspicuous in the Lower Miocene beds of Central Europe. ”

“ In Europe a general emergence of land in late Oligocene time resulted at the beginning of the Miocene (Aquitanian) in widespread lacustrine conditions throughout the western part of that continent, upon which the sea encroached at few points, though it had gained access to the Vienna basin and extended westward into Bavaria. Otherwise, marine Aquitanian deposits are confined to the Mediterranean basin and the south-west corner of France. Most of northern Europe, including the British Isles, remained dry land throughout Miocene time. ”

“ In this area the lowest beds of the Laramie are seen to rest on those of the Fox Hill group of the Upper Cretaceous, and at one point on the west they are overlaid by beds of Miocene Tertiary age, observed by Mr. McConnell, of the Geological Survey, in the Cypress Hills, and referred by Cope, on the evidence of mammalian remains, to the White River division of the United States geologists, which is regarded by them as Lower Miocene. ”

“ The number of exotic forms which are common to the Eocene and Miocene strata of Europe, like those to be alluded to in the sequel which are common to the Eocene and Cretaceous fauna, demonstrate the remoteness of the times in which the geographical distribution of living plants originated. A great majority of the Eocene genera have disappeared from our temperate climates, but not the whole of them; and they must all have exerted some influence on the assemblages of species which succeeded them. ”

“ While it has been customary to describe the Miocene flora of Europe as of a North American type, it would be more accurate to describe the latter as having in great measure preserved its Miocene character.
If mountains serve as barriers which arrest the migration of the vegetation at their base, their upper levels and summits afford lines of communication by which the floras of colder regions in the northern hemisphere can obtain a southern extension even across the tropics. They doubtless equally supply a path by which southern temperate types may have extended northwards. ”

“ That there was a continuity of dry land between Europe and North America during the Miocene epoch, appears to me to be a necessary consequence of the fact that many genera of terrestrial mammals, such as Castor, Hystrix, Elephas, Mastodon, Equus, Hipparion, Anchitherium, Rhinoceros, Cervus, Amphicyon, Hyaenarctos, and Machairodus, are common to the Miocene formations of the two areas, and have as yet been found (except perhaps Anchitherium) in no deposit of earlier age. ”

“ Towards the latter part of the Mesozoic period the movement of upheaval around the shores of the Atlantic once more recommenced, and was very probably accompanied by a depression around those of the Pacific. The Vertebrate fauna elaborated in the Mesozoic continent moved westward and took possession of the new lands, which gradually increased in extent up to, and in some directions after, the Miocene epoch. ”

“ In the Miocene period there is a great development of the horse-like mammals. We have the remains of more than forty species, some continuing the main line of development on the firm and growing prairies of the Miocene, some branching into the softer meadows or the forests, and giving rise to types which will not outlive the Tertiary. They have three toes on each foot, and have generally lost even the rudimentary trace of the fourth toe. ”

“ Europe, during the Pliocene period, seems not to have enjoyed a climate fitting it to be the habitation of the quadrumanous mammalia; but we no sooner carry back our researches into Miocene times, where plants and insects, like those of Oeningen, and shells, like those of the Faluns of the Loire, would imply a warmer temperature both of sea and land, than we begin to discover fossil apes and monkeys north of the Alps and Pyrenees. ”

“ No British strata have a distinct claim to be regarded as Upper Miocene, and as the Lower Miocene are also but feebly represented in the British Isles, we must refer to foreign examples in illustration of this important period in the earth’s history. The term “faluns” is given provincially by French agriculturists to shelly sand and marl spread over the land in Touraine, just as similar shelly deposits were formerly much used in Suffolk to fertilise the soil, before the coprolitic or phosphatic nodules came into use. ”

“ We can carry back that knowledge now to the early Miocene period, to which belong the human relics found by the Abbé Bourgeois on the uplands of Thenay, in central France; and no one believes that the early Miocene age can be as recent as a million years ago. A vast space separates the Thenay relics from the later traces of man found in Pliocene sands with the bones of the archaic meridional elephant,--at a date when the German ocean was a forest, full of southern trees and huge beasts now long since departed from the earth. ”

“ It is certain that throughout the later Miocene and Pliocene the area of land in the northern hemisphere was increasing, and the large and varied continents were tenanted by the noblest vegetation and the grandest forms of mammalian life that the earth has ever witnessed. As the Pliocene drew to a close, a gradual diminution of warmth came on, and more especially a less equable climate, and this was accompanied with a subsidence of the land in the temperate regions and with changes of the warm ocean-currents. ”

“ Asa Gray, that the migration of species, to which the community of types in the eastern states of North America and the Miocene flora of Europe is due, took place when there was an overland communication from America to eastern Asia between the fiftieth and sixtieth parallels of latitude, or south of Behring Straits, following the direction of the Aleutian islands.*** By this course they may have made their way, at any epoch, Miocene, Pliocene, or Pleistocene, antecedently to the glacial epoch, to Mongolia, on the east coast of northern Asia. ”

“ Gray, Saporta, Heer, Newberry, Lesquereux, and Starkie Gardner have all ably discussed these points; but the continual increase of our knowledge of the several floras, and the removal of error as to the dates of their appearance, must greatly conduce to clearer and more definite ideas. In particular, the prevailing opinion that the Miocene was the period of the greatest extension of warmth and of a temperate flora into the Arctic, must be abandoned in favour of the later Cretaceous and Eocene ”

“ The Miocene period is unrepresented by any deposits in Great Britain, unless the Bovey lignite should belong to its earliest stage; we will therefore commence with the best known region—that of central Europe and especially of Switzerland, whence a prolific flora has been collected and described by Oswald Heer. The Miocene lacustrine deposits are contained in a number of silted-up lake basins, which were successively formed and obliterated during the uprise of the Alps and the continuous folding and bending of the earth's crust which was so striking a feature of the period. ”

“ Behind the quaternary comes in the tertiary, with its three great divisions of Pliocene, Miocene, and Eocene, each containing numerous subdivisions, and all showing a progressive advance in forms of life, from older and more generalized types towards newer and more specialized ones, and a constant approach towards genera and species now existing. Behind the tertiary comes the secondary period, into which it is unnecessary to enter for the present purpose, for all is different, and even mammalian life is only known to be present in a few forms of small and feeble marsupials. ”

“ This view is borne out by the fact that the Miocene plants of Europe are most nearly allied to the living plants of the eastern or Atlantic seaboard of the United States, and also by the occurrence of a rich Miocene flora in Greenland. As regards Greenland, Dr Heer has determined that the Miocene plants indicate a temperate climate in that country, with a mean annual temperature at least 30° warmer than it is at present. ”

“ In each successive period the climate becomes somewhat less tropical; but down to the Upper Miocene it remains warm temperate in Central Europe, and cold temperate within the polar area, with not a trace of any intervening periods of Arctic cold. It then gradually cools down and merges through the Pliocene into the glacial epoch in Europe, while in the Arctic zone there is a break in the record between the Miocene and the recent glacial deposits. ”