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Miocene

MIOCENE, in geology, the system of strata which occurs between the Oligocene and the Pliocene. The term, derived from the Greek jueloc, less, and KO.IVOS, recent, was introduced by Sir Charles Lyell, as indicating palaeontologically a less percentage of recent species than is found in the Pliocene. Variable lacustrine, estuarine and marine deposits, especially characterized by soft calcareous sandstones and conglomerates (" molasse ") and sandy shell-beds (" faluns "), make up the Miocene system of the Neogene or newer Tertiary in Europe and western Asia, where it attains its fullest development. A. de Lapparent's classification is here adopted : V. Pontian or Pannonian. Brackish- and fresh-water marls, limestones and gravels: occurring at Vienna, in the Caspian and eastern Mediterranean basins, and in southern France; mammalian deposits of Pikermi and the Siwalik Hills, with Hipparion gracile. Mastodon longirostris. Rhinoceros schleiermachi, numerous ruminants, Congeria subglobosa. Marine beds of Belgium (Black Crag) and north Germany.

IV. Sarmatian. More or less salt-water sands and marls of the same basins with Mastodon angustidens, Anchitherium aurelianense, Cerithium pictum, C. rubiginosum, Ostrea gingensis, Mactra podolica, Tapes gregarius. Stages IV. and V. represented in north-western France by marine sands (Cardita striat issima) , and in Algeria and Morocco by marine marls and limestones. III. Vindobonian. Sub-stages: (b) Tortonian: Marine marls with Ancittana glandiformis, Conus antiquus, Ranella marginata, Trochus patulus, Valuta rarispina. Laminated fresh-water limestones of Oeningen with fish, countless insects, and plants showing seasonal changes of the year m their successive layers (Acer trilobatum, Populus mutabihs, Juglans acuminata, Camphora, Podogonium) ; and the lacustrine deposits of central Spain.

(a) Helvetian: Marine shelly sandstones and conglomerates (" molasse " of Switzerland) with Ostrea gingensis, Cardita jouanneti Panopaea menardi, Conus ventricosus \ the "faluns" of Tourame and Aquitaine; and the marine beds of Black Sea basin. At the base of the marine Helvetian in the Vienna basin clays ( Schlier ) with rock-salt and gypsum, and the lacustrine beds of Gascony (Calcaire de Simon e with Mastodon tapiroides, M. simorrensis Dinotherium giganteum) occur.

II. Burdigalian or Langhian. Marine 'faluns of Bordeaux (Oliva basteroti, Turritella terebralis) ; marls of Langhe in Liguna (Pecten burdigalensis); marine deposits of Vienna basin, Caspian region, Tunis and Algeria; fresh-water sands and marls of Orleans with Mastodon angustidens, M. tapiroides, Dinotherium cumen Anthracotherium onoideum; Littorinella clays of Mainz basin with Acerotherium incisivum Littorinella acuta, Dreyssema brardi; fresh water grey " molasse " of Switzerland, with acacias, laurels, palm: and sequoias.

I. Aquitanian. Limestones, sands and marls of lakes and lagoons with Anthracotherium, Anchitherium, Acerotherium in^vum Palaeochoerus typus. Helix ramondi, Limnaea pachygaster, Planorbi cornu, Potamides lamarcki; Quercus, Acacia, Ficus, Camphora Cinnamomum, Taxodium, Glyptostrobus, Sequoia, Sabal, Phoenix occur in central France (Calcaire de la Beauce); the plant-beds o Manosque; Mainz basin; lower "molasse" of Switzerland will ignite, gypsum, red marls and conglomerates; " brown-coal series " M north Germany with lignite. Intercalated marine sandstones xxur in Aquitaine and near Marseilles; other marine developments Dccur in the " faluns " of Gascony (Lepidocyclina mantelh, Mioypsina burdigalensis), the upper Aquitaman of Bavaria and Austrialungary (Ostrea crassiassima, Pectunculus pilosus), and in southern Spain, Italy and Malta (Lepidocyclina and Lithothamnium). Basic uffs and lavas occur in Auvergne.

SoVne authors assign Stage I. to the Oligocene, Stage V. to the Miocene; Stages I. and II. correspond to the first, and III. to the econd Mediterranean Stage of E. Suess.

In Europe a general emergence of land in late Oligocene time esulted at the beginning of the Miocene (Aquitanian) in widespread lacustrine conditions throughout the western part of that :ontinent, upon which the sea encroached at few points, though it lad gained access to the Vienna basin and extended westward into Javaria. Otherwise, marine Aquitanian deposits are confined to :he Mediterranean basin and the south-west corner of France. Most of northern Europe, including the British Isles, remained dry and throughout Miocene time. During the Burdigalian period, with increasing elevation of the mountain regions and depression of the Mediterranean and Caspian basins, a marine invasion began, which passed its maximum in the Vindobonian. The Mediterranean reached eastward to Persia, and, still open to the Atlantic, subnerged north Africa, most of Italy and the neighbouring islands. It ascended the Rhone valley, penetrated to the Mainz basin, and skirting the north flank of the Alpine region passed into the Vienna basin and thence around the Carpathian tract into the Pontic and Caspian depression. The waters of the Atlantic 'urther invaded the regions of the Garonne and the Loire, isolated Brittany and encroached upon north Europe between Belgium and Denmark.

The elevation of the Alps, and probably of the whole Alpine system of mountain folds from Morocco to Indo-China, though initiated by earlier Miocene and late Oligocene movements, took place mainly during the latter part of the Vindobonian period, and was completed in the Sarmatian. The waters of the ocean were then excluded from the Caspian and eastern Mediterranean basins, and replaced by vast fresh-water lakes; while brackishwater lagoons occupied much of the western Mediterranean. This jreat retreat of the sea culminated in the Pontian stage, and fand-connexion was established between North and South America. Outside the Eurasian region, Aquitanian deposits occur in Formosa, Java, Borneo and Madagascar; while Burdigalian deposits are found in Mongolia. The Vindobonian ranges from Greenland, Iceland and Spitzbergen, where it contains lignite and plants denoting a temperate climate, by Japan, Java and India, to Victoria. It recurs in the Azores and the Antilles, and at intervals along the American continent from Patagonia to Alaska, where all three lower stages are represented, as also in the West Indies. Along the Atlantic slope of the United States and around the Gulf of Mexico the complete Miocene series is present, the Sarmatian and Pontian also occur in California.

The Miocene was a period of change, of mountain-building, climatic differentiation hitherto unprecedented, and of moderation in organic life, especially on land. The rich European flora indicates an equable and moist sub-tropical climate, slowly cooling, as witnessed by the gradual increase of trees with deciduous foliage amongst those characteristic of more tropical conditions. Oaks, maples, poplars, planes, willows, Cinnamomum, Camphora, Myrica, Sequoia, Taxodium, Glyptostrobus and palms, flourished together. The marine calcareous alga Lithothamnium became an important reef-building organism. Nummulites gave place to Lepidocyclina; lamellibranchs and particularly gasteropods abounded in the shallow seas, of which the shark Carcharodon and the marine mammals Squalodon and Halitherium were amongst the largest denizens. The mammalian land-fauna of Europe made striking advances, and assumed a decidedly African aspect. Marsupials had disappeared from it before the Burdigalian period,. during which primitive genera like Palaeochoerus, Hyopotamus, and the hornless ruminants Anthracotherium and Brachyopus, became extinct, while proboscideans (Mastodon, Dinotherium), rhinoceros and apes (Oreoptthecus, Pliopithecus) came in, followed by antelopes, beavers and probably Machaerodus in the Vindobonian. The spread of turf-forming grasses was succeeded in the Pontian by an enormous increase of herbivorous mammals, including Hipparion and horned ruminants (Helladotherium, Antilope, Cervus, Camelopardahs, Palaeotragus), whose migrations were facilitated by the desiccation of the Mediterranean basin.

Note - this article incorporates content from Encyclopaedia Britannica, Eleventh Edition, (1910-1911)

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