Glacial Erosion/Sedimentation of the Baltic Region and the Effect on the Postglacial Uplift

Plio-Pleistocene erosion and sedimentation significantly impact postglacial uplift. We estimate in the last glacial cycle sedimentation could produce up to 155 m of subsidence and erosion 32 m of uplift. To show this we determine the changes in surface load caused by glacial and postglacial erosion and sedimentation over 1,000 year time intervals (coarser intervals before 50,000 years) utilizing a largely automated interpretation of regional geological and geomorphological observations that is constrained by plausible bounds on the rate of erosion of various lithologies and the known general pattern and behavior of glacial ice (ice boundaries over time, the dendritic pattern of ice movement, geometry of fast-flowing ice streams, plausible changes in frozen-bed conditions, etc.). Mass balance between erosion and deposition is enforced at all times. The analysis is regional and obliged to agree with all known geological constraints. Although the focus is on the last glacial cycle, all previous cycles are considered. The analysis suggests that the first glaciations probably shaped the major overdeepened troughs, although it is possible that the deepening was distributed evenly over all the cycles. Younger glaciations mainly removed sediments left by their predecessors, decreasing the thickness of the Quaternary succession and only locally incising and changing the dip of the bedrock surface. Over the last glacial cycle, similar to 20-90 m of sediments (and locally more) was removed in the zones of most active erosion.