Lithological description of subcropping Lower and Middle Triasic rocks from the Svalis Dome, Barents Sea

Abstract

Eleven shallow cores display 315 m of the >700 m thick Lower and Middle Triasic successional of the Svalis Dome, a Salt diapir in the central south‐western Barents Sea. The Svalis Dome was uplifted in the late Mesozoic. and Trisassic rocks suherop below Quaternary till around the Upper Palaeozoic core of the dome. Deposition of the Triassic succession took place in deep shelf to basinal environments below storm wave base. The succession is dated by macrofossils and palynomorphs and can be assigned to four formations. The basal beds of the shaly greenish grey Havert Formation (Griesbachian) occur above Permian bioclastic carbonate. The Klappmyss Formation (Smithian) in the lower part contains gravity flow sands deposited as submarine fans pussible triggered by tectonic movements along the adjacent ault zones overlian by silty claystones. An organic‐rich dark shale unit is here formally defined as the Steinkobbe overlain by silty claystones. An organic‐rich dark shale unit is here formally defined as the Steinkobbe Formation, and was deposited in a large bight by restricted water circulation. The Snadd Formation. on top, representes a marine shelf unit deposited in front of an emerging land area in the north‐east. A minimum of six higher order transgressive‐regressive sequences are recognized at the Svalis Dome and these are correlated with other Arctic areas.

Triassic seismic sequence stratigraphy and paleogeography of the western Barents Sea area

“…11). Shallow cores at the flanks of the Svalis Dome encountered deeper water deposits assigned to the Steinkobbe Formation, representing a setting on a distal outer shelf with restricted circulation (Bugge and Fanavoll, 1995;Mørk and Elvebakk, 1999). Our time-thickness map and paleogeographic reconstruction support a distal development of this sequence in this area.…”

“…In the Early to Middle Triassic, the presence of several marine paleo-basins bounded by Late Paleozoic highs may have given rise to local development of anoxic bottom conditions. Moreover, previous authors have suggested general anoxic conditions for the Triassic due to the ancient paleo-Loppa High and generally limited circulation of the basin (Bugge and Fanavoll, 1995;Leith et al, 1993;Mørk and Elvebakk, 1999;. Well 7321/7-1 showed good source rock potential in the Kapp Toscana Group, indicating anoxic water conditions throughout Ladinian to Carnian time in the Barents Sea area (www.npd.no).…”

“…Several publications have dealt with regional aspects of the Triassic in the Barents Sea (Berglund et al, 1986;Embry and Mørk, 2006;Jacobsen and van Veen, 1984;Johansen et al, 1993;Mørk et al, , 1982Mørk et al, , 1993Mørk and Elvebakk, 1999;Skjold et al, 1998;, but this study includes more data on a regional scale compared to the other studies, particularly in the northern part of the study area.…”

“…The Barents Sea was part of a large epicontinental seaway in the Mesozoic, and Triassic rocks are widely distributed in the Norwegian Barents Sea as interpreted from seismic and borehole data (Bugge et al, 2002;Faleide et al, 1984;Jacobsen and van Veen, 1984;Johansen et al, 1993;Mørk and Elvebakk, 1999;Rasmussen et al, 1993;Riis et al, 2008;Rønnevik et al, 1982;Rønnevik, 1981;Skjold et al, 1998;. Exploration wells drilled the last 30 years and regional seismic studies have revealed a complex structural and stratigraphic development of the area (Dengo and Røssland, 1992;Faleide et al, 1984;Jacobsen and van Veen, 1984;Johansen et al, 1993;Rønnevik et al, 1982;Rønnevik and Jacobsen, 1984;Rønnevik, 1981;Worsley et al, 2001;Worsely, 2008).…”

Thermal maturity, hydrocarbon potential and kerogen type of some Triassic–Lower Cretaceous sediments from the SW Barents Sea and Svalbard

“…For paper 1, a total of 144 samples covering the Triassic to the Early Cretaceous age were (Bugge et al, 2002;Mørk and Elvebakk, 1999), mainly from the Svalis Dome and the Nordkapp Basin. In paper 1, such samples are referred to as ''shallow core samples'' and have sample depth between 27 m and 120 m below the seabed (see Table 2 In terms of lithology, most samples studied in paper 1 represent shale or mudstone or claystone.…”