The Triassic – Early Jurassic of the northern Barents Shelf: a regional understanding of the Longyearbyen CO2 reservoir

Abstract

We address the spatial and temporal development during the Triassic to Middle Jurassic of the NW Barents Shelf in order to provide a regional framework for the targeted reservoir of the Longyearbyen CO2 Lab. The reservoir is Middle Triassic to Middle Jurassic stacked sandstones at a depth of 670–970 m in Adventdalen, Svalbard. The predominantly Carnian De Geerdalen Formation, the lower reservoir, is composed of immature shallow-marine, deltaic to paralic mudstones and sandstones of which over 250 m have been cored at the proposed CO2 injection site. The overlying mid-Norian to Bathonian Knorringfjellet Formation is distinctly more mature and very condensed, with a thickness of just 25 m at the same site. While Early to Mid Triassic sediment influx in Western Svalbard appears dominated by a western source, the De Geerdalen Formation is regionally linked to advancing delta systems from the Uralide mountains and Fennoscandian Shield. The Gardarbanken high hindered Early Triassic progradation and Late Triassic sediment deposition was influenced by the Edgeøya platform. The platform was structurally higher than surrounding areas and limited accommodation space combined with high sediment influx probably caused a rapid advance of the platform edge. The Upper Triassic to Middle Jurassic deposits are condensed with several hiati onshore, and thin and in places eroded offshore. This indicates a strongly linked development across the whole northern Barents Shelf related to limited accommodation space, condensation and/or sediment starvation and erosion.