OSADY PALEOGEŃSKIE W POLSKIEJ CZĘŚCI NIECKI ŻYTAWSKIEJ – NOWE ŚWIATŁO NA PROBLEM WIEKU ZAPADLISKA TEKTONICZNEGO

Abstract

PALEOGENE DEPOSITS IN THE POLISH PART OF THE ZITTAU BASIN – NEW LIGHT ON THE AGE OF THE TECTONIC DEPRESSION

Abstract. The aim of the study was to identify and examine the Cenozoic strata in the southeastern margin of the Zittau Basin (Ohøe Rift) at the crossborder of Poland, Czech Republic and Germany, and to determine the age of the sedimentary and volcanic rocks related to synsedimentary volcanic events. The Opolno Zdrój PIG-1 borehole, located near the village of Markocice, reached a depth of 200.0 m b.g.l. and it was stopped in the crystalline basement of the Zittau Basin, piercing the whole sedimentary series together with the volcanites. A number of sedimentological and lithological studies and laboratory examinations have been performed on samples taken from drill cores. They included (1) a mineralogical/ petrographic study of volcanic rocks and absolute age determination using the K-Ar method (three samples from the borehole and one reference sample from a neraby outcrop) and (2) research of pollen-spore and phytoplankton assemblages from a layer of lignite-bearing sediments lying below the volcanic rocks (six samples). This work determined the age of the covering volcanic rocks at the 24.9–32.7 million years BP, and therefore, the lignite-bearing rocks may have been deposited no later than the Late Oligocene. Although the results of palynological studies did not allow detailed determination of the age of the sedimentary rocks lying below the volcanites, but the superposition of the latter shows evidently that they are older than the Late Oligocene. They could not have been deposited later than in the Early Oligocene and are probably a stratigraphic equivalent of the Turoszów Formation. Thus, the results move the beginning of sedimentation of the coal-bearing layers in the basin Zittau Basin at least to the Late Paleogene.