The Triassic Boreal Ocean was a shallow epicontinental basin and the sink of the World's largest delta plain known to date. Nutrient and freshwater supply from this delta have been regarded as important causes for high productivity and water mass stratification, forming Middle Triassic oil‐prone source rocks. Recent studies attribute upwelling and a productivity‐induced oxygen minimum zone as important factors. A multi‐elemental chemostratigraphic study of a Spathian–Carnian mudstone succession exposed in eastern Svalbard was performed to investigate their formation. This includes 89 samples from three localities, from which 34 elements were acquired using combustion and X‐ray fluorescence analyses. The goal is to provide a correlation framework and infer the role of productivity, redox and water mass restriction on organic matter accumulation and source rock formation. These processes had major impact on the source potential. The Spathian Vendomdalen Member suggests deposition during intermittent benthic euxinia and low productivity, corresponding with a reported deep thermocline that obstructed upwelling. The lower Anisian lower–middle Muen Member shows negligible enrichment in redox‐sensitive elements but in situ phosphate nodules, consistent with developing upwelling and moderate productivity. The middle Anisian upper Muen Member formed during high productivity and phosphogenesis and is linked with basin‐wide upwelling. Productivity, phosphate and redox proxies are all strongly enriched in the upper Anisian–Ladinian Blanknuten Member. In the south‐western Barents Sea, the pro‐deltaic environment of the emerging Triassic Boreal Ocean delta system had terminated these conditions. The upper Ladinian upper Blanknuten Member formed within intermittent euxinic bottom waters due to the shallowing sea level. The Carnian Tschermakfjellet Formation marks the dominance of the prograding delta system and the end of Triassic oil‐prone source rock formation in Svalbard.
The Tromsø - Bjørnøya composite tectono-sedimentary element in the southwestern Barents Sea comprises strata of Late Paleozoic - Paleocene age. Since the Paleozoic Caledonian orogeny, the structural evolution of the CTSE is mainly related to extension, culminating in Late Jurassic - Early Cretaceous hyperextension. Some compressive deformation observed during Late Cretaceous - Paleogene times may relate to activity in the North Atlantic prior to the Early Eocene onset of sea floor spreading between Norway and Greenland.The sedimentary succession may be up to 14 km thick. It comprises Late Paleozoic continental facies, followed by carbonates, evaporites and eventually cherts and marine clastic material. The overlying Triassic - Paleocene succession is entirely siliciclastic, reflecting Triassic - Middle Jurassic deltaic and shallow marine conditions followed by deeper marine conditions during Late Jurassic - Paleocene times.Primary reservoirs are encountered in the latest Triassic - Middle Jurassic succession, with secondary reservoirs found in Late Jurassic - Early Cretaceous syn-rift succession, and in Paleocene strata. The primary source rock for petroleum is of Late Jurassic - Early Cretaceous age. Other source rocks include strata of Triassic and Barremian age, and a recently observed unit of Cenomanian - Early Turonian age.
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