Reefs and geodynamics
|Category||Paleontology and Stratigraphy|
|Location||International Geological Congress,oslo 2008|
|Author||Sobolev, Nikolai; Zadorozhnaya, Ninel; Leontjev, Denis|
|Holding Date||08 October 2008|
After the "Map of reef formations in the territory of Russia" at scale 1:5,000,000 compiled at VSEGEI, the regularities of spatial and time distribution and confinement to paleogeodynamic environments of reef formations, developed in the Russian territory from ε1 to N, are revealed. Reef formations distribute centrifugally from more ancient to more young. PZ1, ε formations are found in the Siberian Platform and in the Caledonian, Altai-Sayan, Baikal, Amur folded regions. On platform, carbonate reef formations are confined to barrier system (2,000 km), which separated lagoon, and deep-water environments. In fold systems, volcanogenic-terrigenic reef formations form in volcanic arc environments and on intraoceanic uplifts; carbonate, on microcontinents. PZ2-3 (Hercynian) formations are located symmetrically with respect to PZ1: in the west, the Uralian folded region, East European and Timan-Pechora platforms, in the east, in fold systems of the Pacific folded belt. Reef systems of spatially associated paleobasins of the East European, Timan-Pechora platforms and the Uralian Ocean can serve as a model of the Hercynian reef development. Reef formations of an oceanic paleobasin record all stages of its development. For a passive margin, thick carbonate reef formation (O2-D2), which fragmentary stretches over 3,000 km, is characteristic. In environments of island arc stage (S2 -D2ef), terrigenous-volcanogenic reef formations, to which bauxite deposits are confined, formed. Carbonate bioherm formations is associated with the pre-continental stage (C1-2). During the continental stage (P1), reef development continued in the Uralian Marginal Depression and the platforms. In the intercontinental paleobasins, reef development took place in zones of activation and destruction of the plate cover associated with the Uralian adjacent paleoocean development. During the convergent and pre-continental stages of ocean development, in the pericratonic shelf of the Timan-Pechora and East European basins (D3-C1), a system of regressive, noncompensated depressions with reef barriers in slope scarps existed. During the continental stage of mountain development (P1), bar-like uplifts, which the reefs developed in the outer shelf of the Timan-Pechora transgressive basin due to the activation of tectonic zones. Oil-and-gas deposits are associated with platform reef formations and the Uralian Marginal Depression. The MZ-KZ (Cimmerian-Alpine) reef formations (T3, J3, N1) spread in Crimean-Caucasus and Sakhalin fold systems surround the development areas of the PZ reef formations. Modern distribution of reef formations in the territory of Russia testifies that reef systems of different age, which initially develop in equatorial zones, record the time sequence of movement and convergence of formerly isolated lithosphere blocks from southern to northern latitudes and reflect geodynamic processes of successive stabilization of Eurasian Continent.