Home – Home – Jornals – Russian Geology and Geophysics 2004 number 1

The Shchuch'ya inlier, geomorphologically highlighted against the plain topography of the southwestern Yamal Peninsula near the northern subduction of the Polar Urals, is a link between the buried structures of the basement of the West Siberian geosyneclise (WSG) and geodynamically well explored Paleozoic structures of the eastern slope of the Urals. Within the entire Uralo-Mongolian Fold Belt, this inlier displays unique denudation. In addition, there are numerous quarries along the railway and automobile road from the town of Labytnangi to northern Yamal. Such a profitable situation, supplemented with data of prospecting and core drilling, makes this area a key object for studying a complete set of environmental facies, stages of development, and conditions of the formation of island-arc complexes in the geochronological range from Ordovician to Carboniferous.
Results of the complex study of the Shchuch'ya inlier by detailed biostratigraphy, structure-tectonic mapping, lithogeodynamic and facies analysis, petrology, petrogeochemistry, and organic geochemistry permitted us to reconstruct the settings and evolution stages of sedimentogenesis and petrogenesis, to corroborate the island-arc nature of structure-formational complexes of this territory, and to reveal their most important morphological, structural, facies, and petrochemical indicator characteristics, which can be efficiently used for diagnosis of geodynamic settings and interpretation of drilling and geophysical data on other areas of the WSG. The specific features of the explored complexes are regular lateral and vertical combinations of thick carbonate massifs with volcanic, terrigenous, and siliceous rocks, the presence of slope facies (thick clastic mixtites and fine-terrigenous gradational gravitites) around organogenic reefs, spatial closeness of deep- and shallow-water facies due to contrasting bathymetric differentiation of the paleobasin. We have established microfacies types of organogenic reefs, conditions of formation of zones of gravitational, hypergenic, and tectonic desintegration of rocks as potential reservoirs, molecular composition, distribution, and catagenesis of organic matter in reefs and near-reef facies as factors contributing to their oil-producing potential. Comparative analysis of geological and geophysical data on other regions of the WSG shows that the island-arc complexes with thick organogenic bodies are rather widespread in the Paleozoic stage of the WSG.