Kama-Kinel System of Downwarps

Internet Geology News Letter No, 11, September 20, 1999

During the Late Devonian a system of downwarps developed between large broad arches on the Volga-Ural regional high of the eastern margin of the East European craton. These downwarps became troughs in which dark to black bituminous argillaceous carbonates collected under uncompensated conditions, while at the same time light-colored limestones were deposited as platforms on the broad arches. Barrier reefs formed along the margins of these carbonate platforms in direct juxtaposition to the bituminous carbonates in the troughs. These features are designated as the Kama-Kinel system of downwarps. Other solitary reefs formed out in the troughs. As a forerunner to development of these downwarps the region became geomorphologically subdued and tectonically quiet. A bitumen-rich argillaceous carbonate, the Domanik Formation, was deposited as a blanket over the entire region. It can be compared with the Chattanooga Shale and the Bakken Shale of the United States. Following deposition of the Domanik, the broad arches were rejuvinated with deposition of "clean" limestone platforms, whereas Domanik-type deposition continued in the troughs between the arches. Extensive barrier reefs on the margins of the carbonate platforms migrated gradually toward the troughs to close them out completely in the Early Carboniferous. The Domanik-type facies is high in sapropelic organic matter and has been an excellent source bed. Where these bituminous rocks were in juxtaposition to barrier reefs, they fed oil into reef reservoirs and into clastics that drape the reefs. These reefs and draping clastics have been prolific oil producers. The Kama-Kinel system of downwarps extends some 1000 km in a north-south direction, and the individual downwarps are 20-90 km wide. On the north they extend into the Timan-Pechora oil-gas province, where they are known as the Pechora system. On the south they extend to the North Caspian depression, which I think is a continuation of the system. I would even like to designate this as the Kama-Kinel-North Caspian system of downwarps. A similar reef system has recently been described in the southwest part of the North Caspian depression in the vicinity of the Karpinskiy ridge (Petroleum Geology, vol. 34, no. 1, p. 53, 2000 - in press). Much oil is yet to be discovered in association with these reefs, particularly in the Samara and Orenburg Regions of Russia and in northwestern Kazakstan. Extensive treatment of these uncompensated downwarps is to be found in Petroleum Geology, vol. 31, no. 1, p. 1-82, 1997. Copyright 1999 James Clarke. You are encouraged to print out this and all other News Letters and to forward them to others. KamaKinel