Two types of craton-margin basin are recognized in the region of the Barents Sea.
The first type includes the Timan-Pechora and Svalbard basins, which formed on a craton margin reflecting the influence of adjacent fold systems. Tectonic activation and stabilization of the main structures of these basins took place in three stages during the time from the Riphean to the Paleozoic: rifting (aulacogen), sineklize (regional low), and inversion.
The second type includes the Barents Sea basin, formation of which is related directly to the effects of oceanic margin. In contrast to the first type where development was complete in the Paleozoic along with attenuation of orogenesis in the adjacent fold systems, the Barents Sea basin continued intensive development reflecting processes taking place in the oceanic depressions of the Atlantic and Arctic Oceans. As a result this basin has two parts - a lower, corresponding with the first type, and an upper, superimposed part. Shall we refer to these as lower and upper mega-complexes.
A Paleozoic aulacogen is the main structural feature of the lower mega-complex of the Barents Sea basin. It extends in an east-west direction from the Norwegian Sea to Novaya Zemlya. East-west structures cutting across Novaya Zemlya have been mapped by seismic surveys. A Barents-Yamal downwarp is recognized at the site of the modern South Barents depression crossing Novaya Zemlya in the zone of the Karmakul' synclinorium. This Paleozoic rift zone continues to the east into the Kara Sea and West Siberian, where similar structures are recognized in the Paleozoic section.
The relationship of this Central Barents - West Siberian zone of aulacogens and the Novaya Zemlya terrane can be explained by super- imposition of an Hercynian rifting onto an older aulacogen zone. Indicative of this hypothesis is the heterogeneity of the geologic make-up of Novaya Zemlya, where north, central, and south blocks are recognized. The south block occupies the area up to Gusinaya Zemlya. The north block extends northward from Russkaya Gaven' Bay. Both these blocks bound the central block along systems of east-west deep faults. The north and central blocks consist of sedimentary rocks of Riphean - Early Devonian age. The central block is composed of highly carbonaceous rocks of Paleozoic age, including Middle-Upper Devonian, Carboniferous, and Lower Devonian rocks.
The central part of Novaya Zemlya thus differs in its history from the north and south blocks. It appears to represent a branch of an Hercynian rift zone that was subjected to folding only during the Triassic Kimmerian orogenesis. Sedimentation in the central part of of Novaya Zemlya took place under shallow-water conditions throughout all of the Paleozoic. The north and south blocks have a different nature.
In summary, the Barents Sea basin may be regarded as an aulacogen structure that developed on a planetary rift, which apparemtly continues into the Kara Shelf and West Siberia. (Taken from Stupakova, 2000; digested in Petroleum Geology, vol, 35, no. 1, p. 49-58, 2001, in preparation; 2 maps, 2 stratigraphic columns, and 1 cross section)
Copyright 2000 James Clarke. You are encouraged to print out this News Letter and to forward it to others, Earlier News Letters are available at http://geocities.com/internetgeology/ This News Letter is distributed without charge in the interest of our science. To be added to the distribution list, please send your e-mail address to: jamesclarke@erols.com