Sedimentary provenance of Triassic sandstones from southern Spitsbergen

Uneven palaeotopography is a feature of the western Barents Shelf in the early Triassic. Structural highs either inhibited sediment dispersal or acted as a sediment source. The variable facies the highs introduce potentially altered sand properties and composition in addition to sand distribution.

The spectacularly exposed Triassic succession around the Sørkapp-Hornsund High in southern Spitsbergen presents an opportunity to investigate these factors in the field, and, possibly reduce exploration risk for analogous submerged systems.

Field and multi-proxy sedimentary provenance data (petrography, QEMSCAN, heavy mineral analysis, garnet geochemistry, K feldspar Pb isotopic data, U-Pb zircon geochronology and combined U-Pb geochronology and trace element geochemistry on apatite and rutile) have helped define four sand types (HST1-4).

The HST1 sand type, which occurs widely in the Early Triassic and intermittently throughout the Triassic to the west of the Sørkapp-Hornsund High, was sourced proximally from regions with a similar geology to the High or from the High itself. The HST2 Sand Type, which includes most of the Middle Triassic strata, was probably sourced from areas affected by the Caledonian orogeny within northeast Greenland. The HST3 Sand Type is confined to Carnian strata to the east of the High. It was sourced from magmatically active and rapidly exhuming regions that was possibly located within the Arctic Uralides near Taimyr. The Snadd Formation of the southern Barents Shelf had a different Uralian source region. The HST4 sand type comprises post-early Norian units across the High and is thickest to the west. Deposited after an inferred drainage reorganisation and basin inversion, it is interpreted to be the result of reworked Palaeozoic-Mesozoic successions located to the north and west.

The distribution of these sand types suggest deposition was strongly influenced by the local Sørkapp-Hornsund structural high. The westward progradation of Carnian Uralian deltaic units appears to have stalled across the high. In addition, the high itself acted as a sediment source, locally delivering lithologically mature sediments. These sandstone relationships may be analogous to the subsurface hydrocarbon-bearing Triassic succession within exploration areas around the Loppa and Stappen highs. This has implications for the occurrence and quality of sandstone reservoir units encountered in these areas, especially since provenance results indicate that the varied depositional environments introduced by the presence of the high played a lesser role on the sandstone compositional maturity than provenance.