Upper Devonian-Tournaisian Facies and Oil Resources of the Russian Craton's Eastern Margin

摘要

Upper Devonian-Tournaisian facies on the Russian craton's eastern margin indicate deposition in two distinct paleomorphic environments: bathimetrically expressed basins and shallow platforms. Shallow-water carbonate sedimentation persisted on the platforms, and black, thin-bedded, organic-rich shales and limestones of the Domanik facies were deposited in stagnant basins that stretched more than 2000 km from the Arctic Ocean to the Caspian Sea. Intermittently introduced clastic material and detrital carbonates formed progradational shelves. Barrier reefs along platform edges, atolls and reef mounds on basin margins, and smaller patch reefs on platforms were abundant. The basins were finally filled with Tournaisian (in the Timan-Pechora province) or basal Visean (in the Volga-Ural province) clastics. The North Caspian deep-water basin survived until the end of Early Permian time when it was filled with a thick salt formation. The organic-rich Domanik facies is the major source rock in the Volga-Ural, Timam-Pechora, and North Caspian petroleum provinces. About one-third of oil reserves occurs predominantly in structural traps in Middle Devonian-lower Frasnian clastics that directly underlie Domanik rocks. Most of the remaining two-thirds is found in reefs, especially in drape structures over the reefs in Tournaisian carbonates and basal Visean clastics. 61 refs., 16 figs. (ERA citation 13:010775)