Main Features of Geologic Structure and History of North-Central Siberia: Regional Arctic Geology of the USSR

The post-Archean history of north-central Siberia is essentially the history of the reconstruction of the North Asiatic craton and its associated mobile belts. The formation of the craton dates back to the early Proterozoic (1,900 m.y.). The craton was bordered on the east by the Olenek fold system and on the west by the geosynclinal belts which were developed as a result of Baykalian, Caledonian, and Hercynian movements. The oldest Archean rocks (charnockite rocks) are exposed on the Anabar shield; the youngest rocks of the craton are the Taymyr-Kara gneisses. During the Proterozoic, a sedimentary cover was deposited across the craton; this sedimentary platform is broken into plates by troughs containing eugeosynclinal strata (presumably of the Grenville series). The overlying rocks are composed of unmetamorphosed terrigenous and marine carbonate deposits of Riphean age. Within the craton the Cambrian-Devonian rocks represent a platform regime. Troughs within the platform are filled with black shale and terrigenous-carbonate marine formations, including gypsiferous sequences. Mottled terrigenous and gypsiferous strata of a lagoonal facies and marine limestones and sandstones were deposited in the pericratonic trough in Severnaya Zemlya. The Carboniferous-Triassic was marked by intensive movements of the Pacific orogenic cycle, which also affected extensive areas beyond the geosynclinal belts. These movements rejuvenated the craton structures and those of the Caledonian and Hercynian systems bordering it. The linear zones of arcogenesis and the associated parageosynclinal trough formed the Taymyr-Severnaya Zemlya fold system on the periphery of the craton. The Tungusska synclinorium and the Anabar anti-clinorium developed in the center of the craton. In the eastern part of the region the active area joined the Verkhoyansk-Chukotsk geosyncline. The Tungusska synclinorium, the Taymyr trough, and the Verkhoyansk geosyncline formed a single system of troughs filled with continental coal-bearing, paralic coal-bearing, and marine terrigenous sediments, respectively. Plateau basalts also occur in the epicratonic troughs, and granitic magmatism is evident in the zones of arco-genesis. The Jurassic-Paleogene was characterized by the return of a platform regime to areas that were formerly active. The age of the basal layer of cover ranges from Liassic in the west to Cenomanian in the east, and there is an eastward reduction in folding. Terrigenous Meso-Cenozoic marine and paralic formations fill isometric and linear troughs and swells. Two sedimentary basins representing the Kara and Laptev Sea shelves were formed on the platform basement during the Neogene-Quaternary. Although the structural framework of these basins differs, their formation is thought to be connected with the development of the Arctic Ocean basin.