Cenozoic reshaping of the Barents-Kara Shelf: Influence of erosion, sedimentation, and glaciation

The morphological evolution of the Barents-Kara Shelf is a graphic example of how erosion and glaciation reshape the Earth's surface. Decades of petroleum exploration sparked longstanding debates on the shelf's obscured Cenozoic history. As a result, the Barents-Kara shelf has almost become a benchmark of erosion models and techniques. Several studies along the edges of the Barents shelf focus on the local relationship between sediments accumulated off-shelf and the amount of erosion in the adjacent areas. However, there are no studies of the entire Barents-Kara region. To address this issue and test the regional estimations of erosion, we first compiled an up-to-date map of erosional products accumulated off-shelf and separated them into Quaternary (glacial) and pre-glacial successions. Mass balance between erosion and sedimentation coupled with numerical analysis of morphology of the Barents-Kara realm demonstrates that the dominant part of Quaternary erosion is expressed within modern cross-shelf troughs and fjords. This analysis also shows that at the beginning of the Quaternary the shelf was submarine, with average water depths of ca. 40–90 m. Using recently acquired borehole data and published thermo-chronological and morphological studies, we developed a new map of Cenozoic erosion of the Barents-Kara shelf. The predicted erosion of our new model is smaller than previously published. However, even reduced, our estimate of erosion volume is almost 50 % larger than the amount of off-shelf sediment. Generally, sub-sea erosion estimates are based on seismic methods and well logs reflecting compaction of sedimentary rocks caused by (now partly removed) load from above. This missing load, however, may comprise not only erosion, but also glaciation, as the shelf was repeatedly covered by thick ice caps. A reduction of erosional estimates by accounting for ice load may provide a balance between accumulated sediments and erosion estimates.