Depositional history of the youngest strata of the sassendalen group (Bravaisberget formation, middle triassic-carnian) in Southern Spitsbergen, Svalbard

Abstract

The Bravaisberget Formation of southern Spitsbergen (the youngest formation of the Sassendalen Group; Middle Triassic-Carnian) comprises a succession of organic-rich and sandy phosphogenic depostts that developed in a marginal part of the Svalbard basin, in response to a high biotogtcal productivtty event in the Barents Shelf. The basin margin was bounded on the southwest by the elevated structure of the Sorkapp-Hornsund High. North of the high, the subsiding shelf bottom stretched from southern to western Spitsbergen. The organic-rich, fine-grained sedimentation that gave rise to the formation of the Passhatten Member extended southward after the Anisian transgression; it reached the topmost part of the Sorkapp-Hornsund High during the maximum floodmg of the basin in the early Ladinian. The sudden appearance of deltaic deposes of the Karen-toppen Member directly after the maximum floodmg was a consequence of short-lived tectonic activity of the Sorkapp-Hornsund High and the adjacent land area. Reworking and redistribution of the deltaic sediments during the Ladinian brought about the formation of shaltow-marine clastic facies of the Somovbreen Member. Decreasing depositional rates close to the Middle-Late Triassic boundary led to a regional hiatus and the formation of a condensed phosphorite horizon at the top of the Somovbreen Member. The sedimentation of the Bravaisberget Formation ended in the early Carnian. The youngest siliciclastic and spiculitic sedments of the Van Keulen-fjorden Member were deposited in southern and western Spitsbergen in shaltowto marginal-marine environments.