Varve sedimentation in extraglacial ice-dammed lakes

Abstract

Pleistocene extraglacial varved clays exposed in Central and northern Poland are deposits of long-time suspension currents. Their variation in the average varve thickness and the origin of varve-series is attributed to changes in the width of the depositional area in extraglacial ice-dammed lakes. The developmental sequence of sedimentary conditions leading from an extragIacial river valley to an ice-dammed lake is proposed and illustrated with examples from the investigated sections. A sharp contact between varved clays and the underlying cross-bedded sands reflects a sedimentary gap caused by the varve sedimentation encroaching upon a river terrace.