Paleozoic facies megazones in the basement of the West Siberian geosyncline

Abstract

Facies zonation of the Paleozoic basement of West Siberian geosyncline and its surroundings is presented. Facies megazones are distinguished according to types of sedimentation. Analysis of lateral and successive sedimentary sequences shows that the available data are insufficient to map the facies distribution over the whole territory of the geosyncline for short time slices. Only the Late Devonian section is supported by data sufficient for the proposed facies zonation. Five megazones, I, II, III, IV, and V, are distinguished in the westward direction. First three megazones make up a single lateral facies succession and represent sedimentary environments on and around the Siberian continent. Megazone IV includes shallow-water volcanic and sedimentary rocks that compose the Kazakhstan continent bounded by Early and Middle Carboniferous sutures in the west and east. Megazone V comprises fold-thrust (island arc) complexes of the eastern Urals. The main events in the geologic history of the region were associated with the interaction of two major crustal masses (Siberian and East European continents) and the young Kazakhstan continent in the oceanic space called the Paleoasian ocean. Only few fragments of this space occur in the present-day framework of the territory, the greatest part being sunk in subduction zones, especially in the large zone of the Main Uralian Fault. Production and accumulation of organic matter in pre-Mesozoic deposits occurred on continental shelves, which are most promising for Precambrian and Paleozoic oil and gas.

Growth rate of the preserved continental crust: II. Constraints from Hf and O isotopes in detrital zircons from Greater Russian Rivers

“…Most studies conclude that the basement is composed dominantly of Hercynian fold belt material and that the eastern part is underlain by the Siberian craton (Yolkin et al, 2007). Alternatively oceanic crust may underlie the central and northern parts of the platform (Aplonov, 1995).…”

“…The Mesozoic era in Greater Russia started with eruption of giant Siberian Traps at 250 Ma, which covered large areas of the Siberian craton, and in the Ural-Mongolia fold belt, especially on the Western Siberian platform (Yolkin et al, 2007).…”

Tectonic history of the Kolyvan–Tomsk folded zone (KTFZ), Russia: Insight from zircon U/Pb geochronology and Nd isotopes

“…The first hypothesis is less likely due to the very rare occurrence of “Siberian” zircons with ages of 2.0–1.8 Ga in the samples (four grains in the each detrital sample). The third possibility is also unlikely, because in the most proximal part of the West Siberian Basin, its folded basement mainly consists of Late Palaeozoic sediments and magmatic rocks, and there is little or no evidence for the existence of Precambrian massifs in this location (Cherepanova, Artemieva, Thybo, & Chemia, ; Isaev, ; Ivanov et al, ; Ivanov et al, ; Ivanov, Fedorov, Ronkin, & Erokhin, ; Kungurtsev et al, ; Yolkin et al, ). Hence, the most probable sources of the Neoproterozoic zircons are the Tuva–Mongolia and/or Atai–Mongolia microcontinents.…”

Нефтегазовая Гидрогеохимия Доюрских Комплексов Южных Районов Обь-Иртышского Междуречья

“…Датировки отложений девонской, каменноуголь ной и пермской систем обоснованы палеонтологи ческими данными. Выявлены тела интрузивных пород преимущественно кислого состава [46], наи более крупным их которых является Межовский гранитоидный массив. На его склонах происходит постепенное выклинивание юрских отложений [47].…”

“…Первый из них развит на территории Туйско Барабинского структурно фа циального района в западной части изучаемой тер ритории, а второй -Нюрольского в восточной [45]. Особенность эффузивно терригенной последова тельности пород заключается в направленности изменения во времени состава вулканитов от сред не основных к средне кислым [46]. Вулканиты среднего состава туйской толщи установлены в разрезах скважин Красногорская 1 и Пахомов ская 1.…”