No abstract

The interpretation of an unpublished data set of shallow stratigraphic cores and deep, seismic profiles from the northern Barents Shelf has provided new information about the Middle and Late Triassic development of the Barents Shelf and Svalbard. At that time, sediment sources along the eastern and south-eastern margins of the Barents Sea controlled the infilling of a previously deeper shelf area, gradually converting it into a paralic platform. Compared with the eastern source, sediment volumes from other areas were small. In our data, there are no indications of a provenance area north of Svalbard. Progradation from the ESE resulted in diachronous lithostratigraphic boundaries. The organic-rich shales of the Botneheia and Steinkobbe formations were deposited in the remaining deeper shelf areas in the western and north-western Barents Sea shelf, from the Olenekian to the latest Ladinian, by which time the progradation from the ESE had reached eastern Svalbard. In mid-Carnian times, the area of paralic deposits extended from the eastern Barents Sea into the Svalbard Archipelago.

Seismic sequence interpretation, analysis of shallow boreholes and outcrop studies at Svalbard strongly indicate that the Triassic basin in the northern Barents Sea and eastern Svalbard was supplied by sediments from the south east by a large complex prograding delta system. The seismic facies interpretation suggests that the black Ladinian and Anisian shale (Botneheia Formation) is an integrated part of the prograding delta system and developed as the bottom sets of large pro-delta clinoforms. The clinoforms and their breaking points define a series of seismically detectable sequences at a shelf edge delta. Provenance areas are suggested to be Siberia, the Kola Peninsula and the Caledonides. Each sequence has a maximum thickness of 200–400 m and is interpreted to represent the water depth range in the basin. Seasonal flooding, stratified salinity and algal blooming are assumed to be important factors generating anoxic bottom conditions in a huge death zone in front of the prograding delta system. The folded and thrusted Triassic rocks in the western part of Svalbard are suggested to be part of an allochthonous nappe ejected from the Greenland region when Greenland moved northwards along the Hornsund Fault complex; their original position is suggested to be further south.

The interpretation of an unpublished data set of shallow stratigraphic cores and deep, seismic profiles from the northern Barents Shelf has provided new information about the Middle and Late Triassic development of the Barents Shelf and Svalbard. At that time, sediment sources along the eastern and southeastern margins of the Barents Sea controlled the infilling of a previously deeper shelf area, gradually converting it into a paralic platform. Compared with the eastern source, sediment volumes from other areas were small. In our data, there are no indications of a provenance area north of Svalbard. Progradation from the ESE resulted in diachronous lithostratigraphic boundaries. The organic-rich shales of the Botneheia and Steinkobbe formations were deposited in the remaining deeper shelf areas in the western and northwestern Barents Sea shelf, from the Olenekian to the latest Ladinian, by which time the progradation from the ESE had reached eastern Svalbard. In mid-Carnian times, the area of paralic deposits extended from the eastern Barents Sea into the Svalbard Archipelago.

No abstract