Depositional history of a condensed shallow marine reservoir succession: stratigraphy and detrital zircon geochronology of the Jurassic Stø Formation, Barents Sea

The Early to Middle Jurassic Stø Formation (Toarcian to Bajocian) was deposited in a relatively shallow (10 s of meter deep) epicontinental sea in northern Pangea and represents one of the most prolific reservoir intervals in the Barents Sea basin. It comprises a condensed, predominantly shallow marine succession characterized by long hiatuses and erosional reworking with several horizons of extraformational pebble grade conglomerate. Six distinct facies associations describe sedimentological environments ranging from transgressive, tidal, fluvial and regressive shoreface. Deposits are interpreted and correlated within three sequence stratigraphic units (SI to SIII) which reflect variations in relative sea-level during an overall transgression of the basin. Interpreted depositional systems show subtle variations in petrographic character, but provenance analyses reveal different sedimentary sources. Thirteen core samples distributed geographically and stratigraphically were analysed for detrital zircon U–Pb geochronology. Data show that the Southwestern Barents Sea Basin (SWBSB) was dominated by mixing of reworked material and coarse grained sediment supply from extrabasinal source areas including a Caledonian provenance in the southwest and a Fennoscandian provenance to the southeast. Intra-basinal erosion of underlying strata with Triassic zircon grains dominate in northern parts of the basin.