Late Cenozoic paleoenvironment of the south-western Barents Sea continental margin

Category Tectonic & Seismotectonic
Group GSI.IR
Location International Geological Congress,oslo 2008
Author Laberg, Jan Sverre۱; Andreassen, Karin۱; Knies, Jochen۲; Vorren, Tore O.۱; Winsborrow, Monica۱
Holding Date 11 October 2008

The late Cenozoic paleoenvironment of the south-western Barents Sea continental margin (Arctic Norway) was studied using 2D and 3D seismic data as well as exploration well results in order to:
• gain additional knowledge on timing and extent of glaciations through the late Pliocene - Pleistocene
• improve our understanding and quantification of glacial depositional and erosional processes
During the late Pliocene - early Pleistocene continental slope sediments were probably mostly glacimarine and deposited from meltwater overflows and underflows. The seismic stratigraphy of the early - middle Pleistocene succession is complex due to a spatial and temporal interplay of sediment input from the ice sheet and episodes of sediment reworking on the continental slope. Sediment input was now both subglacial, i.e. subglacial deformation till, and glacimarine sediments from channelized meltwater discharge. During full glacial conditions of the middle - late Pleistocene, shelf sediments were eroded and transported subglacially as deformation till, then subsequently released and moved downslope as large debris flows. From the above results we infer a three-step evolution of the Barents Sea Ice Sheet (BSIS): 1) a temperate ice sheet during the late Pliocene - early Pleistocene, 2) a colder BSIS including paleo-ice streams in early and middle Pleistocene, and 3) polar ice conditions. The BSIS included large paleo-ice streams during the middle to late Pleistocene. A testable implication of this hypothesis relates to the evolution of the Barents Sea shelf morphology. Assuming that during the last glacial maximum subglacial erosion mainly affected the shelf areas underlying the paleo-ice streams, i.e. the troughs, and using published estimates of glacial erosion rates in nearby areas (2.1 mm/yr) and duration of the last glacial maximum (i.e. the period when the ice sheet ended at the shelf break) (3.5 ka) we find that about 1370 km3 of sediments were produced. This figure corresponds with an earlier estimate of c. 1500 km3 of sediments deposited on the slope during this period. Further implications of this hypothesis for the spatial and temporal distribution of glacial erosion of the Barents Sea shelf will be discussed.
Acknowledgement
This work is a contribution to the PETROMAKS program GlaciPet. Financial support from the Research Council of Norway and StatoilHydro is greatly acknowledged. The University of Tromsø also acknowledges Schlumberger for seismic interpretation software and StatoilHydro for providing seismic data.