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MIOCENE
, in See also:geology, the See also:system of strata which occurs between the Oligocene and the See also:Pliocene
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The See also:term, derived from the See also:Greek isiov, less, and Kaaos, See also:recent, was introduced by See also:Sir See also:
At the See also:base of the marine Helvetian in the Vienna basin See also:clays (" Schlier ") with See also:rock-salt and See also:gypsum, and the lacustrine beds of See also:Gascony (Calcaire de Simorre with Mastodon tapiroides, M. simorrensis, See also:Dinotherium giganteum) occur
.
II
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Burdigalian or Langhian.—Marine " faluns " of See also:Bordeaux (See also:Oliva basteroti, Turritella terebralis) ; marls of Langhe in See also:Liguria (Pecten burdigalensis) ; marine deposits of Vienna basin, Caspian region, See also:Tunis and Algeria; fresh-water sands and marls of See also: Most of See also:northern Europe, including the See also:British Isles, remained dry land throughout Miocene time . During the Burdigalian See also:period, with increasing See also:elevation of the See also: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 See also:Persia, and, still open to the See also:Atlantic, sub-merged north See also:Africa, most of Italy and the neighbouring islands . It ascended the See also: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 See also:tract into the Pontic and Caspian depression . The See also:waters of the Atlantic further invaded the regions of the See also:Garonne and the See also:Loire, isolated See also:Brittany and encroached upon north Europe between Belgium and See also:Denmark . The elevation of the See also:Alps, and probably of the whole Alpine system of mountain folds from Morocco to Indo-See also:China, though initiated by earlier Miocene and late Oligocene movements, took See also: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 brackish-water lagoons occupied much of the western Mediterranean . This See also:great See also:retreat of the sea culminated in the Pontian stage, and land-connexion was established between North and South See also:America . Outside the See also:Eurasian region, Aquitanian deposits occur in See also:Formosa, See also:Java, See also:Borneo and See also:Madagascar; while Burdigalian deposits are found in Momgolia . The Vindobonian ranges from See also:Greenland, See also:Iceland and Spitzbergen, where it contains lignite and plants denoting a temperate See also:climate, by See also:Japan, Java and See also:India, to See also:Victoria . It recurs in the See also:Azores and the See also:Antilles, and at intervals along the See also:American continent from See also:Patagonia to See also:Alaska, where all three lower stages are represented, as also in the West Indies . Along the Atlantic slope of the See also:United States and around the Gulf of See also:Mexico the See also:complete Miocene series is See also:present, the Sarmatian and Pontian also occur in See also:California . The Miocene was a period of See also:change, of mountain-See also:building, See also:climatic differentiation hitherto unprecedented, and of moderation in organic See also:life, especially on land . The See also:rich See also:European See also:flora indicates an equable and moist sub-tropical climate, slowly cooling, as witnessed by the See also:gradual increase of trees with See also: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 See also:reef-building organism . Nummulites gave place to Lepidocyclina; lamellibranchs and particularly gasteropods abounded in the shallow seas, of which the See also:shark Carcharodon and the marine mammals Squalodon and Halitherium were amongst the largest denizens . The mammalian land-See also:fauna of Europe made striking advances, and assumed a decidedly See also:African aspect . Marsupials had disappeared from it before the Burdigalian period, during which See also:primitive genera like Palaeochoerus, Hyopotamus, and the hornless ruminants Anthracotherium and Brachyopus, became See also:extinct, while proboscideans (Mastodon, Dinotherium), rhinoceros and apes (Oreopithecus, Pliopithecus) came in, followed by antelopes, beavers and probably See also:Machaerodus in the Vindobonian . The spread of See also:turf-forming See also:grasses was succeeded in the Pontian by an enormous increase of herbivorous mammals, including Hipparion and horned ruminants (Helladotherium, Antilope, Cervus, Camelopardalis, Palaeotragus), whose migrations were facilitated by the See also:desiccation of the Mediterranean basin . (C . B . |
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