Varying pressures of the ice sheets as a factor of the Pleistocene activity of the Polotsk-Kurzeme and the Smaland-Blekinge deformation zones

Abstract

Topographical maps, airphotos and satellite images suggest a remarkable linear arrangement of landforms here called lineaments. Those lineaments are often related to fault zones of the crystalline basement. A good example of this relationship is the Polotsk-Kurzeme Deformation Zone (PKDZ) nd its possible continuation across the Baltic Sea into the Småland-Blekinge Deformation Zone (SBDZ) and Bornholm Island. The influence of Mesoproterozoic faulting on the Paleozoic, Mesozoic, Cenozoic and recent evolutions of the Precambrian crust has been assessed using 3D reconstructions of paleosurfaces, GIS (=Geographical Information Systems) -models of basement-cover correlation and topolineaments identification. The key target areas of this study have been the Polotsk part of the PKDZ in northern Belarus and the eastern part of the SBDZ in southeastern Sweden. As a result of the study, two main stages of activity of the PKDZ have been identified in the Polotsk area. In the Mesoproterozoic, the major EW- and linked NS-trending fault systems developed in conjunction with orogenic processes at the southwestern margin of the EEC. In the Cenozoic, the activity of this belt was caused by both neotectonics and varying pressures of the ice sheets with attendant Pleistocene deformation of the sedimentary cover within the Polotsk area. In the eastern part of the SBDZ key area the Mesoproterozoic-Phanerozoic activity has been identified.