Genesis of the ‘glacial curvilineation’ landscape by meltwater processes under the former Scandinavian Ice Sheet, Poland

Abstract

Dobrzyń Plateau in central Poland contains a suite of enigmatic glacial bedforms termed ‘glacial curvilineations’ (GCL). These landforms occur within tunnel valleys forming a complex anabranched network. GCL consist of a series of parallel ridges extending for as much as 5km. Over their length, GCL ridges are parallel to neighboring ridges and to tunnel valley margins. Internal GCL composition consists of sand, gravel and till distributed randomly within ridges and in intervening troughs. Electric resistivity tomography surveys confirm the sediment distribution seen in field exposures. Truncated beds near the ridge forms and the heterogeneous nature and distribution of sediments suggest an erosional (rather than accretionary) origin for GCL. In this case, internal GCL composition is not related to GCL genesis: it records proglacial and subglacial conditions prior to GCL shaping by erosion. The terminal zone of the anabranched tunnel valley network is characterized by a broad apron-like ice-marginal sedimentary complex. Sand and gravel dominate sedimentary facies within this zone. Sediments record evidence of meltwater sedimentation associated with supraglacial melting near the ice margin and high-energy subglacial outbursts emanating from tunnel valleys. This interpretation suggests that the GCL surface is a regional unconformity representing an erosional landscape where sediments within landforms offer limited insights into landform genesis (cf., Sharpe et al., 2004). Subglacial meltwater erosion is proposed as unifying model of landscape development as it accounts for both erosion of tunnel valleys and GCL, and meltwater-dominated sedimentation in the ice-marginal sedimentary complex.