A new stratigraphic position of some Early Pleistocene deposits in central Poland

Abstract

A new borehole in Rozce (S Mazovian Lowland) drilled in 2012, combined with a wide variety of research methods (palaeomagnetism, palynological analysis, studies of plant macroremains and textural features of deposits) shed new light on the age and stratigraphic position of the Early Pleistocene deposits, formerly assigned as the Lower Pleistocene. The study focuses on the deposits from 50.7−104.0 m depth, between glacial till of the Nidanian Glaciation (ca. 0.9 Ma) and the Poznan Clays (ca. 5.322 Ma). The deposits situated directly underneath the till (50.7−60.2 m) are related to the Nidanian Glaciation and show a reversed polarity and correlate with the end of the Matuyama epoch. The deposits from 60.2−104.0 m depth were accumulated during the Early Pliocene, i.e. approximately 5.332–4.6 million years ago. They appear to correlate with the middle part of the Gilbert Palaeomagnetic Epoch and thus they are considerably older than previously thought. The cored section indicates a stratigraphic gap of about 3.5 Ma from the Lower Pliocene to the first advance of the Scandinavian ice sheets into Poland, which are thought to have occurred in the early Middle Pleistocene. The analysed deposits accumulated under variable climatic conditions showing two periods with significant aridity alternated with two periods of increased humidity. Deposits of the arid periods contain no pollen, but aeolian sand quartz grains are found. During periods of more humid climate the area was covered by various types of mixed forest.