Paleozoic rocks structure versus Cenozoic cuesta relief along the Baltic Shield–East European Platform transect

Abstract

Based on structural maps, the bedrock structure on the southern slope of the Baltic Shield is analysed. Gently southerly dipping (0.1–0.2°) Paleozoic layers from Estonia to the Swedish east coast form the Baltic Homocline (BH). Numerous monoclinal folds, forced by basement faulting, induce slight variations in bedrock attitude across the BH. Studies on faults exposed in Southern Finland suggest that many monoclinal folds inducing basement faults within the BH are of Precambrian origin and have been active in pulses. The present monoclines were shaped by the Caledonian Orogeny. Submeridional tectonic hinge-lines induce minor regional-scale changes in the structural setting and control trends/styles of the forced folds. From the west, the BH bounds with the Baltic–Bothnian mobile zone that has been intermittently active since Mesoproterozoic times. The evolving Baltic Syneclise in the Silurian rearranged the structural setting typical for the Ordovician Baltic Basin. The Cenozoic uplift of Scandinavia created a SE-to-E-dipping bedrock sequence around the Gotland–Öland area. As the latter area had a different attitude than the BH, two Cenozoic cuesta-sets started to evolve around the northern Baltic Proper. They both had an outlet to the N–S-flowing Eridanos River around the Gotska Sandön area, creating thus two independent sections of the Baltic Klint.