Facies and preservation of glaciogenic sequences from the varanger ice age in Scandinavia and other parts of the north Atlantic region
Abstract Thickness and facies variations and state of preservation of Varangerian glacial sequences are related to the geotectonic settings of the depositional environments. From stable continental platform sites, only thin remnants of a single glacial advance-retreat sequence are preserved. In fault basins, thickness and lithofacies vary in response to fault movements. In the continental platform to shelf region the sequence ranges from thin beds of one single glacial event on the craton to up to some hundred meterswith several glacial advance-retreat cycles from shelf sites. The stable and slowly subsiding shelf environment has given rise mainly to a thin sequence of diamictite overlain by mudstone. In more rapidly subsiding shelves, several glacial advance-retreat units are preserved together with interstadial and interglacial sediments, with total thickness up to several hundred meters. The shelf slope environment is probably represented by up to 3000-m thick diamictites. The preservation potential during the glacial epoch is primarily controlled by the property of glacier ice sheets to be either erosive or depositional. The long-term preservation is determined by various factors controlling relative sea level changes. The state of preservation during orogenic processes generally decreases from sequences on platform sites to those on distal shelves and shelf slopes.