Extraglacial varved deposits, of the Warsaw Ice-Dammed Lake (younger Pleistocene), Mazovia Lowland, Central Poland

Abstract

The varved deposits of the Warsaw Ice-Damnled Lake (Younger Pleistocene), Mazovia Lowland, Central Poland display various sedimentary structures of both wave and current origin. High frequency of wave ripples indicates that the sedimentary environment was shallow water one. Distribution of current structures demonstrates that the deposits have accumulated in ice-dammed lakes fed exclusively by extraglacial rivers. Hence, the depositional basin is here called extraglacial ice-dammed lake, while the deposits are called extraglacial varved deposits. Through most of a year, the basin was ice-covered, and the sedimentary material was transported by currents, mostly turbidite currents. The three distinct varve types (A, B, C) were deposited in proximal, intermediate, and distal zones of the basin, respectively. The so-called composite varves may also occur within deposits of the intermediate and distal zones. Interseasonal lamination in light layers of the varves is interpreted as a reflection of subordinate rhythms in terrigenic influx and wave activity. The sediment type, distribution of sedimentary structures, and occurrence of inset sections is indicative of a complex and multistage development of the varve fades in the Warsaw Ice-Dammed Lake during the younger Pleistocene.