Mezen sineklize (regional low) occupies the area between the Baltic Shield on the west and the Timan Ridge on the east, beyond which is the Timan-Pechora oil-gas province. It opens into the White and Barents Seas on the north. Area is 300,000 sq km. This region has been unjustifiably "offended" with respect to petroleum possibilities. This misconcept goes back to the Forties when this feature was regarded as a Mesozoic downwarp filled largely by continental redbeds. New geological and geophysical information, however, has been the basis for assessing undiscovered resources of Mezen Basin at not less than 600 million tons of oil (4.2 billion barrels) and 100 billion cubic meters of gas (3.5 tcf).
The sedimentary cover consists of three structural stages: syn-rift (Riphean), sineklize (Vendian and Cambrian), and platform (Paleozoic and Mesozoic).
During the Riphean the region of Mezen sineklize was broken up into a series of horsts and grabens with deposition mainly in the grabens. This segment of lithosphere lay in a tropical zone of the Southern Hemisphere. The lower part of the graben fills consists of dark gray argillite some 2.5 km thick. Overlying are variegated alluvial sandstones up to 1400 m thick.
In Vendian-Cambrian time a sineklize covered the entire East European continent. The sediments of this basin rest transgressively on eroded Riphean rocks and are persistent in thickness and composition.
After a break of 120-160 million years deposition of platform sediments began in a sea that transgressed from the east. This section includes Middle-Upper Devonian clastics and Carboniferous-Lower Permian carbonate-sulfate deposits. Accumulation of redbeds in Late Permian and Triassic time is explained by collision in the Ural region. This section tops out with thin continental-marine sediments of the Jurassic, Cretaceous, and Anthropogene.
Numerous oil and gas shows were recorded for these Riphean rocks back in the Thirties. Smears of oil, asphalt, and solid bitumen were described on Yarega structure of Ukhta overthrust. Oil shows were found to depths of 300 m below the top of the Riphean. At the beginning of the Forties a flow of gas at 21,000 cubic meters a day was recovered in Vodnyy area. Since then numerous shows have been recorded for both Riphean and Vendian rocks. It has been noted repeatedly that all the oil shows in Vendian rocks are in areas where Riphean rocks are present, indicating possible migration of oil from the Riphean into the Vendian.
Seismic surveys that were begun in the Seventies in the western part of the Mezen sineklize have recognized reflecting horizons K and L, which are at the top and within the Riphean complex, respectively. These surveys have disclosed several structures as well as some 70 anticlinal flexures. Twelve structures with closure of 80-150 m and areas of 20-250 sq km have been prepared for deep drilling. The exceptionally small amount of geological-geophysical study of Mezen sineklize suggests that additional work must be accomplished there. (From Gavrilov, Rudnev, Dvoretskiy, and Ponomarev, 1998; digested in Petroleum Geology, vol. 33, no. 1, p. 40-52, five maps and one cross section.)
Copyright 2000 James Clarke. You are encouraged to print out this News
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