Late Pleistocene earthquakes imprinted on glaciolacustrine sediments on Gnitz Peninsula (Usedom Island, NE Germany)

Abstract

Oscillation of an ice sheet can be accompanied by earthquakes due to local reactivation of pre-existing faults related to the ice loading. A sufficiently large magnitude of an earthquake can trigger seismic waves that may strongly deform susceptible sediment layers and can cause the development of soft-sediment deformation structures (SSDS). Morphological and structural features of SSDS within a glaciolacustrine succession exposed at the coastal cliff on Gnitz Peninsula (Usedom Island) in NE Germany indicate that they must have developed due to glacial isostatic adjustment, which was suggested earlier by Hoffmann and Reicherter (2012).Here we present detailed micro- and meso-scale SSDS within internally deformed layers interpreted as seismites, liquefaction and re-liquefaction sedimentological imprints on Gnitz Peninsula. New optically stimulated luminescence dating results indicate that the most probable time span of corresponding earthquake occurrence is between 23.2 and 14.6 ka. The interpretation of SSDS ‘trapped’ in layers as seismites is strongly supported by modelling of glacially induced Coulomb failure stress changes in this region. Our results point to a set of probably pre-Quaternary faults which were locally reactivated in the area of Gnitz Peninsula during the last glacial maximum.