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OLIGOCENE See also: Tertiary rocks, viz. those which occur above the Eocene and below the See also: Miocene strata
.
These rocks were originally classed by See also: Sir C
.
See also: Lyell as " older Miocene," the See also: term Oligocene being proposed by H
.
E
.
Beyrich in 1854 and again in 1858
.
Following A. de Lapparent, the Oligocene is here regarded as divisible into two stages, an upper one, the Etampian (from See also: Etampes), See also: equivalent to the Rupelian of A
.
See also: Dumont (1849), and a See also: lower one, the Sannoisian (from Sannois near See also: Paris), equivalent to the Tongrian (from Tongris in See also: Limburg) of Dumont (1859)
.
This lower division is the Ligurian of some authors, and corresponds with the Lattorfian (Latdorf) of K
.
Mayer in See also: north See also: Germany; it is in See also: part the equivalent of the older term Ludian of de Lapparent
.
It should be pointed out that several authors retain the Aquitanian stage (see MIOCENE) at the top of the Oligocene, but there are sufficiently See also: good reasons for removing it to the younger See also: system
.
The Oligocene deposits are of fresh-See also: water, brackish, marine and terrestrial origin; they include soft sands, sandstones, grits, marls, shales, limestones, conglomerates and lignites
.
The See also: geographical aspect of See also: Europe during this See also: period is indicated on the accompanying map
.
Here and there, as in N . Germany, aher A.de Lapparcpt Emory See also: Walker to
the
See also: sea gained ground that had been unoccupied by Eocene See also: waters, but important changes, associated with the continuation of elevatory processes in the Pyrenees and See also: Alps which had begun in the preceding period, were in progress, and a general relative uplifting took place which caused much of the Eocene sea floor to be occupied at this See also: time by lake basins and lagoons
.
The movements, however, were not all of a negative character as regards the water areas, for oscillations were evidently frequent, and subsidence must have been considerable in some regions to admit of the accumulation of the See also: great thickness of material found deposited there
.
Perhaps the most striking change from Eocene topography in Europe is to be seen in the extension of the Oligocene sea over North Germany, whence it extended eastward through Poland and See also: Russia to the See also: Aral-See also: Caspian region, communicating thence with Arctic waters by way of a Ural depression
.
The Asian extension of the central mediterranean sea appears to have begun to be limited
.
It was later in the period when the wide-spread emersion set in
.
In Britain Oligocene formations are found only in the Hampshire See also: Basin and the Isle of See also: Wight; from the admixture of fresh-water, marine and estuarine deposits, E
.
See also: Forbes named these the " Fluviomarine series." The following are the more important subdivisions, in descending See also: order: 'The Hamstead (See also: Hampstead) beds, marine at the top, with Ostrea callifera, Natica, &c., estuarine and fresh-water below, with Unio, Viviparus and the remains of crocodiles, turtles and mammals
.
The Bembridge marls, fresh-water, estuarine and marine, resting upon the Bembridge See also: limestone, with many fresh-water fossils such as Limnaea, Planorbis, Ohara, large See also: land snails, Amphidromus, See also: Helix, Glandina, and many See also: insects and plant leaves
.
The See also: Osborne beds, marls, See also: clays and limestones, with Unio, Limnaea, &c
.
The Headon beds (upper), fresh-water clays, marls and limestones (See also: middle), brackish and marine, more sandy (lower), brackish and fresh-water clays, marls, tufaceous limestones and sandstones
.
The clays and sands of the Bovey Basin in Devonshire were formerly classed as Miocene, but they are now regarded by C
.
See also: Reid as Eocene on the evidence of the plant remains, though there is still a possibility that they may be found to be of Oligocene age
.
In See also: France the best-known See also: tract of Oligocene rocks rests in the Paris basin in close relationship with the underlying Eocene
.
These rocks include the first and second See also: gypsum beds, the source of " See also: plaster of Paris "; at Montmartre the first or upper See also: bed is 20 metres in thickness, and some of the beds contain siliceous nodules (fusils) and numerous mammalian remains
.
Above the gypsum beds is the travertine of Champigny-sur-See also: Marne, a series of blue and See also: white marls (supra-gypseous marls), followed by the " glaises verts " or greenish marls
.
At the top of the lower Oligocene of this
See also: district is the lacustrine " calcaire de Brie " or middle travertine, which at Fertesous-Jouane is exploited for millstones; this is associated with the See also: Fontainebleau limestone, which at Chateau-Landon and Souppes is sufficiently compact to See also: form an important See also: building See also: stone, used in the Arc de Triomphe and other structures in Paris
.
The upper Oligocene of Paris begins with the marnes a huitres, followed by the brackish and fresh-water molasse of Etrechy, and a series of sandy beds, of which the best known are those of Fontainebleau, Etampes and Ormoy; in these occur the
See also: groups of See also: calcite crystals, charged with See also: sand, See also: familiar in all See also: mineral collections
.
Elsewhere in France similar mixed marine, fresh-water and brackish beds are found: in See also: Aquitaine there are marine and lacustrine marls, limestones and molasse; marine beds occur at See also: Biarritz; lacustrine and fresh-water marls and limestones with See also: lignite appear in the sub-Pyrenees; in See also: Provence there are brackish red clays, conglomerates and lignites, with limestones in the upper parts; and in Limagne there are mottled sands, arkoses, clays and fresh-water limestones
.
In the See also: Jura region and on the See also: borders of the central See also: massif a See also: peculiar See also: group of deposits, the terrain siderolithique, is found in beds and in pockets in See also: Jurassic limestones
.
Sometimes this deposit consists of red See also: clay (bolus) with nests of pisolitic iron, as in Jura and Franche-comte, See also: Alsace, &c.; occasionally, as in Bourgogne, See also: Berry, the valley of the Aubois, See also: Chatillon, it is made up of a See also: breccia or conglomerate of Jurassic pebbles cemented with See also: limonite and carbonate of lime or See also: silica (an intimate mixture of marl and iron ore in these districts is called " castillard ")
.
At Quercy the cementing material is phosphate of lime derived from the bones of mammals (Adapis, Necrolemur, See also: Palaeotherium, Xiphodon, &c.), which are so numerous that it has been suggested that these animals must have been suffocated by gaseous emanations
.
Similar ferruginous deposits occur in See also: South Germany
.
In the Alpine region the Oligocene rocks assume the character of the See also: Flysch, a complex assemblage of marly and sandy shales and soft sandstones with calcareous cement (" macigno ")
.
The Flysch phase of deposition had begun before the close of the preceding period, but the bulk of it belongs to the Oligocene, and is especially characteristic of the lower part . The Flysch may attain a very great thickness; in See also: Dauphine it is said to be 2000 metres
.
Obscure plant-like impressions are See also: common on certain horizons of this formation, and have received such names as Chondrites, Fucoids, Helminthoidea
.
The " gres de Taveyannaz " and " Wildflysch " of Lake See also: Thun contain fragments of eruptive rocks
.
Marine beds occur at Barreme, See also: Desert, See also: Chambery, &c., and parallel with the normal Flysch in the higher Alps of Vaudois is a nummulitic limestone; both here and near See also: Interlaken, in the marble of Ralligstocke, calcareous See also: algae are abundant
.
Part of the " schistes See also: des See also: Grisons " (" Biindner Schiefer ") have been regarded as of Oligocene age
.
In the Leman region the " Flysch See also: rouge " at the See also: foot of the Dent du Midi belongs to the upper part of the Flysch formation
.
In North Germany the lower Oligocene consists largely of sandy marls, often glauconitic; typical localities are Egeln near See also: Magdeburg and Latdorf near See also: Bernburg; at See also: Samland the glauconitic sand contains nodules of See also: amber, with insects, derived from Eocene strata
.
The upper Oligocene beds, which cover a wide See also: area, comprise the See also: Stettin sands and Septarian Clay or Rupelton, marine beds tending to See also: merge laterally one into another
.
In the See also: Mainz basin a petroleum-bearing sandy marl is found at Pechelbronn and Lobsann in Alsace underlying a fresh-water limestone which is followed by the marine
Meeressand " of See also: Alzey
.
Lignites (Braunkohl) are widely spread in this region and appear at Latdorf, See also: Leipzig, in Westphalia and See also: Mecklenburg; at See also: Halle is a variety called pyropissite, which is exploited at See also: Weissenfels for the manufacture of See also: paraffin
.
Map of
Europe
in the early part of the
Oligocene Period
MS
.
=Lando, undifferentlated area Lagoon.)areaa molasse " is usually given; mixed with the molasse is an inconstant conglomeratic littoral formation, called Nagelfluh . The molasse occurs also inSee also: Bavaria, where it is several thousand feet thick and contains lignites
.
Oligocene deposits occur in the Carpathian region and See also: Tirol; as Flysch and brackish and lacustrine beds with lignite in Klausenburg, lignites at Haring in Tirol
.
In the See also: Spanish Pyrenees they are well See also: developed; in the Apennines the scaly clays (" argille scagliose ") are of this age; while in See also: Calabria they are represented by thick conglomerates and Flysch
.
Flysch appears also in Dalmatia and See also: Istria (where it is called " tassello ") and in North Bosnia, where it contains marine limestones
.
Lignites are found at Sotzka and Styria, marine beds in the See also: Balkan peninsula, glauconitic sands prevail in So' ith Russia, Flysch with sands and grits in the See also: Caucasus, while 'marine deposits also occupy the Aral-Caspian region and Armenia, and are to be traced into See also: Persia
.
Oligocene rocks are known in North See also: Africa, See also: Algeria, See also: Tunis and See also: Egypt, with the silicified trees and See also: basalt sheets north of the See also: Fayum
.
In North See also: America the rocks of this period have not been very clearly differentiated, but they may possibly be represented by the White See also: river beds of S
.
Dakota, the white and blue marls of See also: Jackson on the See also: Mississippi, the " Jacksonian " white limestone of See also: Alabama, the limestone of Ocala in See also: Florida, certain lacustrine clays in the Uinta basin, and by the See also: rib-See also: band shales with See also: asphalt and petroleum in the coastal range of California
.
In South America and the See also: Antilles upper Oligocene is found, and the lignite beds of Coronet and Lota in Chile and in the Straits of See also: Magellan may be of this age; in See also: Patagonia are the lower Oligocene marine beds (" Patagonian ") and beds with mammalian remains
.
In New Zealand the See also: Oamaru series of J
.
Hutton is regarded as Oligocene; at its See also: base are interstratified basic volcanic rocks
.
A correlation of Oligocene strata is summarized in the following table : in the Eocene seas (Coelopleurus, Echinolampus, Clypeaster, Scutella) . Corals were abundant, and nummulites still continued till near the close of the period, but they were diminished inSee also: size
.
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