Paratethys

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Proto- Mediterranean and early Paratethys, approx. 30  mya ( Rupelium , local Kiscellium ), at the beginning of the main phase of the Alpidian orogeny
Final stage of the central Paratethys as Pannon Sea , approx. 11.5 mya ( Tortonium , locally Pannonium or Sarmatium ), the western Paratethys is already completely dry

The Paratethys is in the geological a marginal sea Eurasiens extending between the auffaltenden alpidic mountains and the Eurasian continent primarily on continental crust formed. It extended in the Palaeogene and Neogene from the Rhone area to the region of today's Aral Sea .

Spatial structure

The Paratethys is today divided into three sub-regions according to facial , biogeographical and plate tectonic aspects: western, central and eastern Paratethys. The western Paratethys includes the Rhone Basin in eastern France and the Molasse Basin in Switzerland and western Bavaria. The central Paratethys extends from the Molasse Basin of Eastern Bavaria to the eastern fore-depth of the Carpathian Arc and includes above all the intermontane basins, the Vienna Basin , the Styrian Basin and the Pannonian Basin . The eastern Paratethys is by far the largest of the three sub-areas. It extends from the Black Sea to the Aral Sea in Central Asia.

In fact, the Black Sea and the Caspian Sea as well as the Ohrid Sea in the border area of Macedonia and Albania are residual waters of the Paratethys. In the u. a. of today's Neusiedler See and Lake Balaton , there was an extensive brackish water lake , the Pannon Lake , from the Upper Miocene onwards , but the two today's lakes were created relatively recently and are therefore, unlike z. B. the Ohridsee, no residual waters of the Paratethys.

Naming and history

The term Paratethys was proposed in 1924 by Vladimir Dmitrijewitsch Laskarew (1868-1954) primarily to differentiate the fauna of the Paratethys from the Mediterranean fauna.

Plate tectonic situation

By the North drift of Africa along with the still fixed to the Arabian Peninsula and the present Indian plate disappeared Tethys ocean image to the upper Eocene increasingly in the forming alpidic orogenic . In the west, the southern Tethysarm was gradually reduced to a small remnant that is now in the eastern Mediterranean . The northern Tethysarm was basically reduced to a narrow, deep basin north of the Alpid collision front. A new ocean formed south of India, the Indian Ocean . In the further course of the Alpid orogeny, a predominantly continental marginal sea , the Paratethys, formed around the Eocene / Oligocene border north of the orogen front, and the Mediterranean Sea in the western part of the orogen, south of its front. In the further tectonic course of the events, new oceanic sub-basins also formed in the western Mediterranean. The deposit area of ​​the western part of the Paratethys is also commonly called the Molasse Basin .

Paleogeography and sedimentation

At the Eocene / Oligocene border, the western Paratethys was largely separated from the Mediterranean. Only in the western pre-Alps and in the area of ​​today's Slovenia did deeper sea areas open to the Mediterranean. The Danish - Polish Strait and another strait in the area of ​​the Rhine Trench connected the Paratethys with the North Sea during NP21 (paleogennannoplankton zone 21 = lower regional North German level Latdorfium , lower global level Rupelium ) . A first certain isolation of the Paratethys is indicated by the sedimentation of black schist in the following zone NP 22. In the upper part of NP 22 the widespread Spiratella / Limacina - or Pteropod - marls were deposited, which can be used as a guide horizon for correlation. In the eastern Paratethys the sedimentation did not keep pace with the subsidence . Black shale and manganese ores formed in the ever deeper basins under hydrogen sulfide conditions . These deposit conditions persisted in the eastern part through the entire Oligocene and Lower Miocene . In the NP23 zone, the connections to the world's oceans were largely interrupted, and under anaerobic conditions, dark, banded clays, nannoplankton marls, which contain only one species, and limnic - brackish diatomites were deposited . Marine fauna are only known from the westernmost part of the Paratethys.

Only in the middle Oligocene (NP24 = regional level of the Kiscellium , global level of Aquitaine ) were fully marine conditions established again in the entire Paratethys area. The strait of the sea in the area of ​​today's Slovenia became wider. Presumably there was also a connection from the Indian Ocean to the Paratethys in the area of ​​today's Caucasus . Now mainly clastic sediments ( clay and sandstones ) were deposited, e.g. T. also as Turbidite . At the end of the Oligocene, the sea withdrew from the western part of the Paratethys to the line Munich-Salzburg, so that only limnic and fluvial sediments were deposited here ("lower freshwater molasses"). Connections to the open sea widened further east. In the area of Thrace , a new connection to the Mediterranean opened up during the NP25 zone. These conditions lasted into the lowest Miocene (NN1 = Neogennoplankton Zone 1). Marine faunas from the area of ​​today's Iran ( molluscs and large foraminifera ) were able to penetrate into the central areas of the Paratethys. In the Burdigalium , too, there were close faunistic relationships with the Indo-Pacific region. A horizon with huge pectinid mussels and other large molluscs stretched from California to the Bavarian Molasse Basin.

In the lower Burdigalium (= Eggenburgium ) the connection in the western Paratethys opened again, but the sea connection in the area of ​​today's Slovenia closed. In the upper Burdigalium ( Ottnangium ), Africa and the Arabian Peninsula, which is still connected to it, collided with the Anatolian Plate , and the connection to the Indian Ocean was interrupted. The Mediterranean was now exclusively a bay of the Atlantic . The eastern Paratethys lost its connection to the open sea and sweetened, the so-called Kotsakhurium basin was created, in which an endemic fauna developed. In western Tethys, the connection to the Mediterranean remained open, a narrow corridor opened over the Rhine rift to the North Sea. The eastern part of the Carpathian pre-depth became an evaporite basin . At the end of the Ottnangian regression occurred and estuarine sediments were deposited in the central Paratethys.

In the middle Miocene there was a transgression that can be correlated with the base of the Langhium . A new connection between the Mediterranean Sea and the Indian Ocean opened up between Anatolia and the Arabian Peninsula, as did a sea connection in eastern Anatolia between the eastern Paratethys and the Indian Ocean. However, this sea connection probably did not result in fully marine conditions for the entire basin. This high sea level was also coupled with tropical conditions in the Paratethys area, which extended to southern Poland.

The regression in the lower Serravallian largely ended the links between the Paratethys and the open sea. The eastern Paratethys developed into the Karaganium Sea . In the central Paratethys, the Transylvanian Basin and the Carpathian pre-depth became evaporite basins. Only the Pannonian Basin retained a connection to the Mediterranean. This connection was made in the course of the Serravallium. In return, a sea connection opened up to the eastern and central Paratethys, as shown by the Indo-Pacific fauna in the Paratethys. The last time there were marine conditions from the Vienna Basin in the west to the Trans-Caspian Basin in the east.

At the end of the Badenium , the Paratethys was largely isolated from the open sea. Presumably there was only a narrow sea connection between the Mediterranean Sea and eastern Paratethys via eastern Anatolia.

At the beginning of the Sarmatian , this sea connection was probably also lost. The salinity sank and - more importantly for the fauna development - the alkalinity increased. All stenohaline organisms died out. The fauna was similar in the entire (remaining) area of ​​the Paratethys. In the area of ​​the central Paratethys, the sedimentation area became increasingly smaller and the Carpathian sub-depth fell dry. A brackish water lake with greatly reduced salinity, the Pannon Lake , formed in the Carpathian Arch . In this area, the Sarmatian fauna elements almost died out, while the Sarmatian fauna in the Dacian and Euxinian basins persisted. There, in the Bessarabian and Khersonian, a mass multiplication of mussels of the Mactridae family occurred . In the upper Khersonian there was a regression that briefly isolated the Black Sea, but which was flooded again in the lower Maeotian . Another regression in the upper maeotium led to the almost freshwater conditions of the pontium . The Pontic Sea extended from the Pannonian Basin to the Black Sea. With the Pliocene Transgression, the present-day situation came about.

stratigraphy

In the central and eastern Paratethys area, a graded structure that deviates from global stratigraphy is used, as the sedimentary rocks there are often very difficult to correlate with the global structure . In the western area the following structure is used:

In the eastern Paratethys area, such as the Black Sea and Caspian Sea, other regional levels are mostly used.

See also

literature

  • Martin Oczlon: Terrane Map of Europe. Gaea Heidelbergensis, 15, Heidelberg 2006 JPG ( Memento from March 10, 2015 in the Internet Archive )
  • Fred Rögl: Mediterranean and Paratethys. Facts and hypotheses of an Oligocene to Miocene palaeogeography (short overview) . Geologica Carpathica, 50 (4): 339-349, Bratislava PDF
  • HM. Schulz, A. Bechtel and RF Sachsenhofer: The birth of the Paratethys during the Early Oligocene: From Tethys to an ancient Black Sea analogue? Global and Planetary Change 49 (3-4), p. 163-176, Amsterdam 2005 doi : 10.1016 / j.gloplacha.2005.07.001
  • Fritz F. Steininger and Godfrid Wessely: From the Tethyan Ocean to the Paratethys Sea: Oligocene to Neogene Stratigraphy, Paleogeography and Paleobiogeography of the circum-Mediterranean region and the Oligocene to Neogene Basin evolution in Austria. Communications from the Austrian Geological Society, 92: 95-116, Vienna 2000 PDF

Web links

Commons : Paratethys  - collection of images, videos and audio files

Individual evidence

  1. ↑ Vladimir Laskarev: Sur les equivalents du Sarmatien supérieur en Serbie . In: P. Vujević (ed.): Recueil de travaux offerts à M. Jovan Cvijić par ses amis et collaborateurs . Belgrade 1924, p. 73-87 (cited in Steininger and Wessely 2000, p. 95).