Page:Encyclopædia Britannica, Ninth Edition, v. 10.djvu/377

Rh M1oeENE.] Miocene period. With these exceptions there are no Miocene rocks in Britain. CO.'TINE.'T.-‘LL EURorE.—The records of the Miocene period in Europe bring before us a scene very different from that which the region presented during the Eocene ages. The least amount of change took place in the north-west and north. It consisted chieﬂy in the upraising of the ﬂoor of the shallow sea which had stretched eastwards across the north of France, and the formation of numerous fresh-water lakes, lagoons, and morasses. But over the Alpine region a vast revolution took place. The Eocene sea had its bed elevated, and the Alps rose many thousand feet above their previous height, carrying up on their ﬂanks the hardened, upturned, crumpled, and crystallized nummulite limestone. These vast corrugations of the carth’s crust were general over the whole globe about the same "geological period. Subter- ranean movements appear to have continued during Miocene times in the Alpine area; large lake—basins were formed over a great part of what is now Switzerland, and in these the deposits of the period took place. Hence the Miocene formations of Europe are in great measure of lacustrine and terrestrial formation. The sea, however, was allowed to pass across the south of France between the central axis and the Pyrenees. It likewise covered a wide area in eastern Europe, sweeping far up into the Vienna basin and the foot of the Austrian Alps. Traces of the occasional presence of the sea can likewise be followed across Belgium and North Germany, and even on the south side of the Eifel and Wcstphalian high grounds in the basin of Mainz. In France, on the north side of the axis of old rocks, the upper parts of the Eocene series are covered by certain marls, clays, and lime- stones, containing Ostrca cyathula, and passing up into the thick sandstone of Fontainebleau, well known for its picturesque scenery. '[‘hcse are considered as the base of the Miocene (or Oligocene) series. They contain Fusus elongatus, Aporrhais speciosa, Pcctzm- culus obovatus, Cyrcna scnn'st)'z'ata, Ccrz'tIn'u.m plicatum, 8:c. They are succeeded by some fresh-water limestones (Calcaire dc Beauce) full of Palurlina, Plano?-bis, Limnam, and Helix. These strata show very instruetively the gradual shallowing of the sea in the north of France, and its conversion into fresh-water lakes and land. Further to the south a subsequent depression took place, in which the shclly sands and marls (faluns) of 'l‘ourainc were accumulated. These strata lie in scattered patches, and seldom exceed 50 feet in thickness. They contain chiefly marine shells (Cg/prtea, Oliva, Mitra, Tcrcbra, Fasciolaria, Comts, &c.), also remains of the 1)icilobzI.ne and C/zcvropotmnus, with some of the huge early pachydcrnis,—.l[astodo)L, Dinotlzerimn, rhinoceros, hippopotamus, and species of dolphin, morse, &e. In North Germany the older Miocene rocks are marine where they pass westwards into the Belgian area, but as they are followed south- wards they bear evidence of increasing proximity to land, till at last the_v contain abundant seams of lignitc, and hence have been termed the Brown-coal series. They appear to underlie most of the great north Germanic plain, on the south side of which they rise up into the Rhine valley, Thuringia, Saxony, and Silesia. The ’.mwn-coal series consists of sandstones, conglomerates, and clays, with leaf-beds and seams of lignite. The last, which have been lzu-gely worked as fuel, are mainly composed of remains of conifers, (Tu.citcs, T(r..'co.r_1/Ion, Cuprcssz'/Lo:cylon, Sequoia), but with them are associated, in the neighbouring strata, leaves and other fragments of oak, beech, maple, fig, laurel, cinuamomum, magnolia, sassafras, palmacitcs, Szc. Thcsc strata are overlaid by marine beds contain)- ing Us-lrca, Crmlita, Plcurotoma, Voluta, and numerous corals. The subterranean movements above referred to as having long all}:--ted the Alpine region were felt likewise in North Germany, for we find these marine beds succeeded by a second lignitie forma- tion, seen at Grosser Ilubcneeken, on the eastern horn of the Gulf of Dantzic. But this could only have been a local uplift, for marine sands and clays are next found with a wide diffusion over the plains of northern Germany, _ Nowhere in Europe do the Miocene formations play so important a part in the scenery of the land, or present on the whole so interesting and full a picture of the state of Europe when they were deposited, as in Switzerland. Rising into massive mountains, as in the well-known Righi and llossberg, they attain a thickness of more than 6000 feet. While they include indications of the presence of GEOLOGY 363 the sea, they have preserved with marvellous perfection a large number of the plants which clothed the Alps, and of the insects which ﬂitted through the woodlands. They are termed “ .Iolasse” by the Swiss geologists, and have been divided into the following groups :—- Upper fresh-water Molasse and brown-coal, consisting of sand- stones, marls, and limestones, with a few lignite-seams and fresh-water shells, and including the remarkable group of plant and insect-bearing beds of Oeningen. Upper marine Molasse (Helvetian stage)—sandstoncs and calcare- ous conglomcratcs, with 37 per cent. of shells, which are to be found living partly in the Mediterranean, and partly in tropi- cal seas. Lower fresh-water Molassc (Mainz stagc)——-sandstones with abundant remains of terrestrial vegetation, and containing also an intercalated marine band with Ckrithium, Venus, &c. Lower brown-coal or red Molasse (Aquitanian stage)—the most massive member of the whole series, consisting of red sand- stones, marls, and conglomerates (Nagelﬂuh), resting upon variegated red marls. It contains seams of lignite, and a vast abundance of the remains of terrestrial vegetation. Lower marine Molasse ('l‘ongrian stage)—sandstone containing marine and brackish-water shells, among which is the 0strea- cyathula, above mentioned as a characteristic shell, at the base of the Miocene series in the north of France. By far the larger portion of these strata is of lacustrine origin. They must have been formed in a large lake, the area of which pro- bably underwent gradual subsidence during the period of deposition, so that the sea gained occasional admission into it. Ve may form some idea of the importance of the lake from the fact already stated, that the deposits formed in its waters are upwards of 6000 feet thick. Thanks to the untiring labours of Professor Hcer, we know more of the vegetation of the mountains round that lake than we do of that of any other ancient geological period. The woods were marked by the predominance of an arboresccnt vegetation, among which ever- green forms were conspicuous, the whole having a decidedly Ameri- can aspect. Among the plants were palms of American type, the Californian coniferous genus .S'cquoz'a, a great variety of maples, oaks, hornbeams, poplars, planes, willows, laurcls, evergreen oaks, with vines, clematis, cyprcsses, and many more. In the Ocningcn beds, so gently have the leaves, flowers, and fruits fallen, and so well have they been preserved, that we may actually trace the alternation of the seasons by the succession of different conditions of the plants. Selecting 482 of those plants which admit of comparison, llcer re- marks that 131_might be referred to a temperate, 266 to a sub-tropi- cal, and 85 to a. tropical zone. American types are most frequent among them; European types stand next in number, followed in order of abundance by Asiatic, African, and Australian. Great numbers of insects (between 800 and 900 species) have been obtained from Ocningen. Judging from the proportions of species found there, the total insect fauna may be presumed to have been then richer in some respects than it now is in any part of Europe. The wood- beetles were specially numerous and large. Nor did the large animals of the land escape preservation in the silt of the lake. 'e know, from bones found in the Molasse. that among the inhabitants of that land were species of tapir, mastodon, rhinoceros, and deer. The woods were haunted by musk-deer, apes, opossums, three-toed horses, and some of the strange, long-extinct Tertiary ruminants, akin to those of Eocene times. There were also frogs, toads, lizards, snakes, s uirrcls, hares, beavers, and a number of small carnivores. On the la cc the huge Dinotlwrium ﬂoated, mooring himself perhaps to its banks by the two strong tusks in his under jaws. The waters were likewise tcnantcd by numerous fishes (of which 32 species have been described, all save one referable to existing genera), crocodiles, and chelonians. Contemporaneously with the existence of the great Swiss Miocene lake, one or more 1. rge sheets of fresh water lay in the heart of F rancc. In these. basins a series of marls and limestones (1500 feet thick) acemnulated, from which have been obtained the remains of nearly 100 species of mammals, including some palzeotheres, like those of the Paris Eocene basin, a few genera found also in the Lower Miocene beds of Mainz, crocodiles, snakes, and birds. This water basin appears to have been destroyed by volcanic explosions, which afterwards poured out the great sheets of lava, and formed the numerous cones and prays so conspicuous on the plateau of Auvergnc. The sea which during the later part of the Miocene period stretched across the south of France ran also up the present valley of the Danube to the foot of the Alps and the high grounds of Bohemia and Moravia In this wide eastern bay or 'ienna l)aSlI] a series of deposits was laid down, which have been grouped in four divisions, —the two lower classed as Miocene, and the two upper as Pliocene. The lowest group (Mediterranean stage or Marine Tegel) has yielded more than 1000 species of mollusca (C'o7zzts, .»1ncz'IIm‘za, Pyruhz, J[m'c.7:, Cardium, &c.), with remains of Jlastodou, Dino-