Z zagadnień paleogeografii młodszego paleogenu na Niżu Polskim

Krystyna Pożaryska, Ewa Odrzywolska-Bieńkowa



European marine basins from the Early Tertiary times represented narrow, elongate basins filled up with terrigenous material. They were mainly inhabited by benthic fauna and the share of plankton was negligible. The paper deals with Early Tertiary paleobiogeographic provinces of the extra-Alpine Europe with a special attention paid to the area of Poland. In the Paleogene these areas were mainly affected by the Boreal province and the fauna inhabiting them adapted to its relatively low temperature conditions. Uplift of Alpine orogens which was taking place in these times modified migration routes of faunas by limiting spread of Tethyan forms. The influences of warm Tethyan province were marked in the Upper Eocene and Middle Oligocene and, on much smaller scale, in the Montian. In Poland, they may be traced only on the west.
In the Montian, warm-water microfauna from south-western Europe reached only to Pamiętowo near Chojnice whereas in the ate Eocene its extent covered the whole western Poland as it is recorded in several localities from the Fore-Sudetic monocline, Kujawy and the vicinities of Szczecin where even nummulitids occur. At that time the areas situated east of the Mid-Polish Anticlinorium was occupied by cold sea with typical cold-water microfauna. Such microfauna is known both from the Łeba elevation and the eastern Poland. The warm-water microfaunal assemblages appeared once more in the Oligocene but only in the western Poland and the Lower Vistula river delineated their distribution from the east. The whole area of the Mazury lakeland and Mazowsze region situated further to the east represent some kind of barrier separated the Middle Oligocene NW-European marine basin and the Maikop basin continuing from the area of the USSR. This was a relatively wide continental barrier formed in result of movements uplifting Scandinavia in these times and resulting an filling up its forefield with detrital material. I some parts of that barier area existed swampy areas without outflaw the deposits of which nowadays yield Oligocene floral remains. These deposits are known as Toruń clays.
It follows that in the Late Eocene and Oligocene the Mid-Polish Anticlinorium acted as barrier separating western province strongly influenced by warm Tethyan Ocean and the eastern, Boreal province (in the Eocene) or it represented a continental sandy region with the lacustrinal basins (in the Oligocene).
The mean annual temperature was very high in the Late Eocene in Europe (Denmark), ranging from +20°C to +28°C. This was followed by significant rapid coolness to +10°C or even +5°C in some places in the Oligocene. This coolness was universal as it is recorded in western Europe and USSR as well as New Zealand and it was one of most important events in the whole Cenozoic history.

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