Depositional and Diagenetic Environments of the Triassic and Lower Jurassic Succession of Svalbard

Abstract Triassic and Lower Jurassic strata are found over large areas of the Svalbard archipelago. Both potential source and reservoir rocks occur within this succession, a feature of significance for petroleum exploration activities on nearby shelf areas. We will first present a revised lithostratigraphical scheme for the succession and then review the depositional and diagenetic histories of the major stratigraphic units within this framework. The entire succession is dominated by clastic sediments deposited in varying offshore to marginal marine environments on a relatively stable epicontinental platform. This lay between 45 degrees and 60 degrees N in the temperate climatic zone and facies patterns have not been influenced by any major climatic variation. Thickness variations seen (min. 250 m - max. 1200 m) can be directly related to differential downwarping over a series of NNW - SSE trending fault lineaments; facies patterns show a similar but more complex pattern. Lower and Middle Triassic units were deposited in a generally transgressive sequence with intermittent coastal progradation from the west. Middle and Upper Triassic sequences indicate deltaic progradations from both west and east, while the Rhaetoliassic is characterised by condensed and incomplete sequences throughout the archipelago; eastern areas do however show most complete remains of Rhaetoliassic sedimentation. Diagenetic and organic geochemical studies of the entire succession are in progress and results are discussed in terms of our sedimentational models.