Sequence Stratigraphic Analysis of Tertiary Wedges and Sediments in Sørvestsnaget Basin, SW Barents Sea

Abstract:

The Sørvestsnaget Basin is a Cenozoic depocenter in Southwestern Barents Sea formed along the North-South Senja fault. Previous research works in this area have identified a thick succession of Tertiary wedges sourced potentially from the Stappen High. This study is aimed at evaluating the evolution of the Tertiary deposits in the Sørvestsnaget Basin using sequence stratigraphic approach. Five sequences were interpreted from recently acquired high-resolution 2D seismic reflection data. Lithology and biostratigraphic information was obtained from two boreholes in the study area, 7316/5-1 and 7216/11-1S. The sequences were separated into maximum flooding surface, condensed section, and a sequence boundary that correlate from wells to seismic for hundreds of kilometers. The first sequence is the base of the Paleogene unit revealed as low and high basement configuration. This sequence is succeeded by a transgressive system tract (TST) dominated by deposition of deep marine shale after a relative sea-level rise. Biostratigraphy data from well 7216/11-1S revealed stratigraphic breaks on the Late Eocene to Miocene age condensed section. Uplift of the marginal high in Oligocene to Miocene times influenced the development of an early highstand system tract (EHST) during Neogene age. This is followed by deposition of shallow marine sediments and emergence of a late highstand system tract (LHST) in early Quaternary. The LHST developed in a glacio-marine environment. Relatively low sea-level fall during middle Quaternary forced the development of a shelf margin towards the south. The top of the shelf margin system tract (SMST) was eroded by the Upper Regional Unconformity (URU). In Late Quaternary, the Sørvestsnaget Basin witnessed a relatively sea-level rise evidenced by the back-stepping sequences above the URU on seismic section. This is the last transgressive system tract (TST). This work has shown that the Sørvestsnaget Basin has recorded fluctuating sea-level rise since approximately 34 Ma.