Subglacial bed deformation and dynamics of the Apriķi glacial tongue, W Latvia

Abstract

We evaluate the glacial dynamics and subglacial processes of the Apriķi glacial tongue in western Latvia during the Northern Lithuanian (Linkuva) oscillation of the last Scandinavian glaciation. The spatial arrangement of glacial bedforms and deformation structures are used to reconstruct the ice dynamics in the study area. The relationship between geological structures at the glacier bed and the spatial distribution of drumlins and glacigenic diapirs, on the one hand, and the permeability of sediment and bedrock, on the other, is ascertained. Drumlins are found in the upper part of the Apriķi glacial tongue area and are composed of soft deformable sediments overlying highly permeable Devonian dolomite. The soft deformable clayey silty bed with low hydraulic conductivity is conducive to the development of diapirs. The occurrence of diapirs and drumlins is controlled by the fluctuation of pore-water pressure at the glacier bed and is considered to be an indicator of fast ice flow of the Apriķi glacial tongue during its reactivation at the end of the Oldest Dryas (18-15kaBP). © 2011 The Authors. Boreas © 2011 The Boreas Collegium.