OSADY PALEOGENU I NEOGENU W WIELKOSKALOWYCH STRUKTURACH GLACITEKTONICZNYCH WZGÓRZ DYLEWSKICH

Abstract

PALEOGENE AND NEOGENE SEDIMENTS IN MEGA-SCALE GLACIOTECTONIC STRUCTURES OF THE DYLEWSKIE HILLS

Abstract. The Wysoka Wieś borehole located in the center of Dylewskie Hills (NE Poland) reached a depth of almost 490 metres, with more than 400 metres of the Paleogene and the Neogene deposits. Palynological studies were designed to determine whether this huge Paleogene and Neogene sedimentary complex is located in situ or it has been glacitectonically redeposited. Forty-seven samples were analysed for all palynological matter components, i.e. palynomorphs (sporomorphs, phytoplankton, zoomorphs), palynoclasts (phytoclasts) and inorganic debris. Among the palynomorphs, 13 assemblages have been distinguished. Describing these assemblages from the bottom to the top of the section, dual or triple repetition of the same palynomorph zones indicates a strong glacitectonic deformation of the sediments. Palynological data evidence several disengagement zones and displacement of rock packages. The lowest sedimentary complex occurs in the primary position and it contains the pollen and phytoplankton assemblage D3–D4 of the Middle Paleocene to the Upper Paleocene (terrestrial facies), and the Lower Eocene assemblage D8. At a depth of ca. 455m there is the first discontinuity zone, along which the over 100-metres thick package of Middle Miocene sediments, containing pollen zones V, VI, VIII, IX and XI, became intruded/ pressed into the Paleogene deposits. The next disengagement zone occurs at a depth of ca. 339 m, where the Miocene sediments are overlain by a about 60-metres thick package of Paleogene deposits dated with the stratigraphically younger pollen and phytoplankton zones D12 of the Upper Eocene and Lower Oligocene (terrestrial facies). These Paleogene deposits were intruded by the Miocene series, a few metres thick, representing pollen zone IX. Then, at a depth of 240 m, occurs the Middle Miocene sedimentary complex, ca. 150m thick, with pollen zones V, VII and IX. The complicated glacitectonic processes caused such mosaic succession, reflecting the slice structure of glaciotectonic thrust moraines. Palynological studies provided unique data to define the glaciotectonic disengagement zones. The absence of Quaternary deposits in the internal moraine structure indicates the Early Pleistocene age of deformation.