Triassic Seismic Sequence Stratigraphy and Paleogeography of the Norwegian Barents Sea

Evy Glorstad-Clark¹, Jan Inge Faleide¹, Tore Høy², and Bjørn A. Lundschien^2
1Department of Geoscience, University of Oslo, Oslo, Norway.
²Norwegian Petroleum Directorate, Stavanger, Norway.

A sequence stratigraphic framework of the Triassic on the Norwegian Barents shelf is presented. The Triassic succession was subdivided into 5 second-order sequences based on facies analysis of 2D seismic data constrained by well data.

The Mesozoic succession in the Barents Sea was deposited in a shallow epicontinental seaway with local basins developed on the shelf. Time-thickness maps of the Triassic sequences illustrate the changes in depocenters through time and the gradual infill of pre-existing topography in the basin. The two lower sequences exhibit an eastward thickening towards the main sediment source area with marine onlap onto highs in the basin (e.g., Loppa High, Stappen High) and thinning and pinching out of the sequences on the Svalbard Platform to the north. The main depocenter in the earliest Triassic was at the Bjarmeland Platform, with sediment thicknesses decreasing towards the west and northwest. The main focus of deposition shifted from Ladinian time, with a significant westward and northwestward thickening of sequences, indicating reduced accommodation space to the south and east and infill of accommodation space east of the Loppa High. The Loppa High controlled sediment distribution until Early Ladinian times, with one major uplift event in latest Permian and several subsequent minor events of renewed uplift and creation of local source areas as observed from aerially restricted systems prograding from the west to the east. In the Late Triassic, the Loppa High became one of the main depocenters, dominated by subsidence related to sediment loading and potentially responding to extension in the North Atlantic system to the west.

Due to gradual infill of the Barents Sea during the Triassic, progressively larger areas on the Svalbard Platform were covered by shallow shelf and paralic deposits in the Late Triassic, characterized by prograding seismic clinoforms from the south and east. Accommodation space east of Bjørnøya-Sørkapp High was filled during this time period, sourced from the east, but possibly also from the west. In the southern part of the study area the Upper Triassic east of the Loppa High exhibits a gradual shallowing upwards of the Triassic succession and infill of available accommodation space in this area and sediment bypass further northwest and west.

Within each sequence, maximum progradation and retrogradation were mapped out and discussed in terms of reservoir, seal and source rock development.

AAPG Search and Discover Article #90096©2009 AAPG 3-P Arctic Conference and Exhibition, Moscow, Russia