Facies development of the upper triassic succession on Barentsøya, Wilhelmøya and NE Spitsbergen, Svalbard

Abstract

Field data collected from the northeasternmost Triassic exposures on the islands of Spitsbergen, Wilhelmøya and Barentsøya during 2015 are used for sedimentological facies analysis to improve our understanding of the stratigraphic development of the Upper Triassic strata. Results presented here build upon previous studies from the eastern areas of the Svalbard archipelago and seek to extend this understanding northward. Paralic deltaic sediments are recognised throughout the field area, and our analysis shows that the Upper Triassic De Geerdalen Formation is composed of three discrete units defined by the differences in gross depositional environments. The lower interval of early Carnian age is dominated by shallow-marine and delta-front/ shoreface deposits, the middle interval of mid Carnian age is dominated by delta-front to delta-top deposits, and the upper interval, corresponding to the Isfjorden Member, of a late Carnian to early Norian age, is dominated by delta-top deposits which include lagoonal and lacustrine deposits. These observations show that the De Geerdalen Formation represents a more distal depositional setting, than the depositional environments previously reported from the islands of Edgeøya and Hopen. We also document the presence of the Tschermakfjellet Formation and Isfjorden Member on Wilhelmøya, thus increasing our understanding of the northwestward development of the Upper Triassic succession in Svalbard.