BREEROSJON

A regional view of large-scale glacial processes and ice-sheet dynamics on the mid-Norwegian continental shelf during the Weichselian are presented on the basis of a regional digital bathymetric dataset. At times, ice flow was mainly channellised through ice streams located in bathymetric depressions on the shelf areas. Glacial sedimentary processes are discussed with focus on the marine-based part of the Scandinavian ice sheet during the last glaciation (the Weichselian). Ice sheets that grounded on the shelf edge are throught to have been responsible for depositing complex prograding sequences reaching a maximum thickness of 1500 m on the shelf edge during several glaciations from Late Pliocene time. During interglacials, the shelf areas were sediment starved with little or no clastic sedimentation. Situated above these prograding units, several sediments packages (mainly till of Weichselian age) show a more aggradational pattern.

A three-phase conceptual glacial geological model for the Late Pliocene and entire Pleistocene period has been developed. The model explains variations in erosion in the Barents Sea in space and time and shows:
The first phase (until ca. 1.5mill. years) was characterized by glacial erosion over the present land areas of Svalbard and Norway. Minimal, if any, erosion over present shelf areas.
A transition phase (ca. 1.5 - ca. 0.5 mill. years) with glacial erosion over restricted areas. In the Norwegian sector glacial erosion was active from Svalbard down to the Bear Island Trough. Little, if any, glacial erosion south of the Bear Island Trough.
The last phase (ca. 0.5 mill. years - present) is characterized by glaciations covering the entire shelf areas. This seems to be the only period when repeated glaciations eroded in the southwestern Barents Sea shelf, i.e. in the areas of petroleum prospecting.
The three-phase glacial erosion model is supported by data on climate change over the period, by modelled change in topography, and by glacial geological data, especially from the Barents Sea. The approach and data also show that there is a great potential to test and refine the model to make it applicable to erosion estimates.