Abstract
The post-Archean history of north-central Siberia is essentially the reconstruction of the history of the North Asian craton in relation to the evolution of the surrounding mobile belts. The formation of the craton dates to the early Proterozoic (1,900 m.y. ago). It was bordered by the Olenek fold system on the east and in the west by geosynclinal belts, which completed their development through a succession of Baikalian, Caledonian, and Hercynian movements. The most ancient Archean rocks (charnokite) are exposed on the Anabar shield; the youngest rocks of the craton are represented by the Taimyr Kara gneisses. During the Proterozoic a sedimentary platform cover was deposited across the craton; this platform is broken into plates by troughs with eugeosynclinal formations (presumably-Grenville). The sedimentary cover rocks are unmetamorphosed-terrigenous and marine-carbonate deposits of Riphean age. Within the craton the Cambrian to Devonian is characterized by 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 limestone and sandstone were deposited in the pericraton trough in Severnaya Zemlya. The Carboniferous to Triassic was marked by intensive movements of the Pacific orogenic cycle which also affected many areas outside of the geosynclinal belts. Pacific-cycle 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 Taimyr-Severnaya Zemlya fold system on the periphery of the craton. The Tunguska synclinorium and the Anabar anticlinorium formed in the center of the craton. In the eastern part of the region the area of activization joined the Verkhoyansk-Chukotsk geosyncline. The Tunguska synclinorium, the Taimyr 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 are present in the epicraton troughs; granitic magmatism is displayed in arcogenesis zones. The Jurassic to Paleogene was characterized by the return of a platform regime in former areas of activization. The basal layer of sedimentary cover becomes younger from west (Liassic) to east (Cenomanian) as the folding decreased. Terrigenous Mesozoic-Cenozoic marine and paralic formations filled isometric and linear troughs and swells. Two sedimentary basins representing the Kara and Laptev sea shelves formed on the platform basement during the Neogene-Quaternary stage. The structural framework of these basins differs; their formation is connected with the development of the Arctic Ocean basin. End_of_Article - Last_Page 2511------------
Published Version
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