Mesozoic rocks are known from most of the major islands of Svalbard, namely, Spitsbergen, Nordaustlandet, Barentsoya, Edgeoya, Kong Karls Land, Hopen, and Bjornoya.

Sedimentary rocks range in age from Triassic (early Scythian) through Early Cretaceous (Albian) and comprise three lithostratigraphic units: Sassendalen Group (Griesbachian to Anisian), Kapp Toscana Formation (Ladinian to Toarcian), and Adventdalen Group (Bathonian to middle Albian). The facies are mostly drab shale, siltstone, and sandstone (generally marine shales and continental sandstones), which contrast markedly with the underlying Permian cherty carbonate rocks, and not so obviously with the resistant overlying Tertiary coal measures. The marine strata are characterized by the presence of ammonites, bivalves, and saurians; the continental strata contain plant beds and thin coal seams, some bivalves, and vertebrates. The succession and the facies are very similar to those of Arc ic Canada. The most conspicuous rocks in the older part of the sequence are the cliff-forming marie igneous sills and flows of latest Jurassic and/or Early Cretaceous age.

The Mesozoic tectonic activity followed a relatively stable late Paleozoic history, producing a marked change of facies but conformable strata. The maximum known thickness of Mesozoic strata is about 3 km (10,000 ft). The first distinguishable disturbance (warping and faulting) accompanied basic igneous activity but caused little change in sedimentary facies. The principal unconformity represents a hiatus which lasted from late Albian to early Paleocene(?) time. There is local overstep of Tertiary rocks onto the lowermost Triassic, but generally only the uppermost Albian members are missing. These minor disturbances may be related to (1) movements that culminated in the West Spitsbergen orogeny in early to mid-Tertiary time and (2) the mainly Tertiary Arctic Ocean spreading. Svalbard robably was moved from subtropical to temperate latitudes in Mesozoic time, and Arctic latitudes were not reached until later.

Petroleum propects in the Arctic are enhanced by the presence of Mesozoic rocks which provide source and reservoir rocks and caprocks.