Paleogeograficzne powiązania między epikontynentalnym a geosynklinalnym basenem w kredzie górnej i paleocenie

Abstract

PALEOGEOGRAPHIC CONNECTIONS BETWEEN EPICONTINENTAL AND GEOSYNCLINAL BAS INS IN THE LATE CRETACEOUS AND PALEOCENE IN POLAND Summary The connections between the Northern Basin and the Tethys are difficult to reconstruct as transitional area between the zones became incorporated in the Carpathian tectogen. Transitional features are displayed by the Baculites Marls (Upper Cretaceous) from the Carpathian Flysch in the vicinities of Przemyśl. In the Cretaceous, the connections between the Tethys and Polish Lowlands were presumably fairly good as the area of the present-day Lower San anticlinorium ha d been covered by sea at least till the Santonian. In turn, the sea way was confined to area east of the anticlinorium in the Paleogene, that is after Laramie inversion of the anticlinorium and other parts of the Polish-Danish aulacogen. In Poland, epicontinental Upper Cretaceous deposits yield remains of warm-water faunas, including innumerous Tethyan ammonites such as Placenticeras, Sphenodiscus, and Hauericeras. In the foraminifer microfauna, the share of forms coming from the Tethyan region is fairly large. Here predominate planktonic forms, especially keeled foraminifers typical of the Tethys. The studies on development of plankton in the Upper Cretaceous in platform areas in Poland made it possible to trace foraminifer sequence closely corresponding to that described from the Tethys. In the Polish Lowlands, foraminifer plankton of the lowermost Tertiary (Danian) is highly improverished but, nevertheless, it comprises the same forms as coeval deposits from the Carpathians. Benthic foraminifer assemblages of the Montian of the Polish Lowlands also comprise warm-water forms but of the western Buropean type, different than the Carpathian. Paleocene deposits from Babica yield benthic forms the same as in the Boreal province. It should be emphasized that the two basins, Tethyan and North European (epicontinental), were influencing one another along a fairly wide front in the Late Cretaceous and much narrower seaway in the Paleocene. The exchange of fauna was fairly intense at the beginning of the Late Cretaceous, gradually weakening thereafter. This may be explained by the rise of the Lower San anticlinorium which began in the Santonian, impeding the exchange of fauna.