Mesozoic Geology of Svalbard: ABSTRACT

Abstract

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), with facies mostly drab shale, siltstone, and sandstone--generally marine shale and continental sandstone--and comprise 2 lithostratigraphical units: Sassendalen Group (Griesbachian to Toarcian) and Adventdalen Group (Bathonian to mid-Albian). These units contrast markedly with the underlying Permian cherty carbonates, and not so obviously with the resistant overlying Tertiary coal measures. The marine strata are characterized by ammonites, bivalves, and saurians; the continental strata have plant beds, thin coal seams, some bivalves, and vertebrates. The succession and facies are very similar to those of Arctic Canada. The most conspicuous rocks in the older part of the sequence are the cliff-forming basic igneous sills and flows of latest Jurassic and/or Early Cretaceous age. The Mesozoic tectonic pattern followed a relatively stable late Paleozoic history with a marked change of facies but conformable strata. The maximum known thickness of Mesozoic strata is about 3 km. The first distinguishable disturbance (warping and faulting) accompanied basic igneous activity but with little change of sedimentary facies. The principal unconformity represents a hiatus which took place in late Albian to early? Paleocene time. There is local overstep of Tertiary rocks onto lowermost Triassic, but generally only the uppermost Albian members are missing. These minor disturbances may be related to movements that culminated in the West Spitsbergen Orogeny in early to mid-Tertiary time, and to the mainly Tertiary Arctic Ocean spreading. Svalbard was probably moved from subtr pical to temperate latitudes in Mesozoic time, only subsequently achieving arctic latitudes. Petroleum prospects in the Arctic must take Mesozoic rocks into account as providing source, cap, and reservoir rocks. End_of_Article - Last_Page 2484------------