The sea cliff at Dwasieden: soft-sediment deformation structures triggered by glacial isostatic adjustment in front of the advancing Scandinavian Ice Sheet

Karsten Obst,Tom Van Loon,Szymon Belzyt,Henrik Rother,Małgorzata Pisarska-Jamroży,Gösta Hoffmann,Holger Steffen,Michael Kenzler,Heiko Hüneke,Andreas Börner,Rebekka Steffen

doi:10.5194/deuquasp-2-61-2019

Abstract

Abstract. Isostatic response of the Earth's crust as a consequence of the fluctuating extent of ice-sheet masses was accompanied by earthquakes probably due to local reactivation of pre-existing faults. Our study of a glacilacustrine and glacifluvial succession exposed on Rügen Island (SW Baltic Sea) indicates that some of the soft-sediment deformation structures within the succession must have formed shortly before the front of the Pleistocene Scandinavian Ice Sheet reached the study area (during the Last Glacial Maximum), thus during a stage of ice advance. Based on analysis of the textural and structural features of the soft-sediment deformation structures, the deformed layers under investigation are interpreted as seismites which formed as a result of seismically induced liquefaction and fluidisation.

Highlights

Bending of the Earth’s lithosphere and mantle displacement can be induced by loading–unloading cycles resulting from alternating advances and retreats of an ice sheet
The location under study is situated at the southernmost rim of the TransEuropean Suture Zone (TESZ)
The TESZ is a zone of crustal weakness and is characterised by numerous faults activated and reactivated during several late Palaeozoic and Mesozoic tectonic phases

Summary

Introduction

Bending of the Earth’s lithosphere and mantle displacement can be induced by loading–unloading cycles resulting from alternating advances and retreats of an ice sheet (see, e.g. Mörner, 1990). There is only little evidence that the ice-sheet advance could cause earthquakes, too (Brandes et al, 2011; Pisarska-Jamrozy et al, 2018a, 2019), and that corresponding SSDSs of seismic origin have been formed. Tertiary sediments are only locally preserved in graben structures bordered by WNW–ESE- to NW– SE-trending faults of the Western Pomeranian Fault System. This suggests reactivation of this fault system during the Cainozoic ( during the Oligocene–Miocene) due to changes in the stress field (compression) from NE to NW (Seidel et al, 2018)

Soft-sediment deformation structures interpreted as seismites

Age and origin of the seismites