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Stratigraphy and sedimentary environments for cretaceous deposits in the southern part of the Var’egansk Megabar (Western Siberia) 总被引：1，自引：0，他引：1
G. N. Aleksandrova V. A. Kosmynin A. V. Postnikov 《Stratigraphy and Geological Correlation》2010,18(4):411-435
Results of comprehensive studies of the Var’egansk Megabar sections in boreholes which penetrated the upper part of the Pokur
Formation and the lower part of the Kuznetsovo Formation are presented. The stratigraphic range of the studied deposits spans
the upper Albian-lower Turonian. Palynological and lithofacies studies resulted in the refinement of sedimentary paleoenvironments
in the region under study. It has been confirmed that the upper part of the Pokur Formation was formed under coastal-marine
conditions; it characterizes mainly different deltaic facies. Sandy rocks of the Pokur Formation upper part mostly formed
in delta channels, whereas silty-clayey rocks, in marshy-swamp environments. Deposition of the Kuznetsovo Formation is confined
to a major sea transgression, and it proceeded under normal sea conditions. 相似文献
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Abstract The Oka Belt, composed of clastic rocks and greenschists, extends for approximately 600 km in the South-Siberian Sayan region and adjacent northern Mongolia. For a long time the Oka Belt's age and tectonic setting were the most controversial problem in the region. We argue that the belt was formed in Late Neoproterozoic as an accretionary prism. The Oka Belt shows imbricated thrust structure, which had originally seaward vergence and reflected the Neoproterozoic accretion process. The Early Paleozoic orogeny had minor effect on its structural style. The belt contains tectonic slivers of mid-ocean ridge basalts, some oceanic-island basalts and possible pelagic sediments. In several localities they are associated with gabbro and serpentinite. All these rocks represent the oceanic lithosphere subducting beneath the Oka prism and trapped within it. In the inner zone of the Oka Belt are the blueschists exhumed from the deeper prism level. The northern Oka Belt includes mafic intrusions geochemically similar to normal mid-oceanic ridge basalt and felsic volcaniclastic rocks. This segment of the belt is very similar to the Tertiary portion of northern Shimanto Belt, in Japan, and has also experienced the subduction of orthogonal oceanic ridge beneath the prism. This event dates back to 753 ± 16 Ma (the U-Pb zircon discordia). The Oka prism started accreting in Mid-Neoproterozoic after the subduction had initiated under the Japan-like South-Siberian continental terrain. The prism existed through the second half of Neoproterozoic and accumulated a huge volume of sialic material to enlarge the nearby continent. Currently, the Oka Belt remains poorly studied and is very promising for further investigation and discoveries. 相似文献
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K. S. Alekseeva L. P. Popova A. V. Postnikov O. V. Postnikova 《Doklady Earth Sciences》2016,470(2):1014-1018
The Lower Cambrian Usol’e Formation in the Kamov arch of the Baikit anteclise includes stratiform intrusions confined to several levels. According to isotopic?geochronological investigations, the age of stratiform intrusions composed of olivine dolerites is estimated to be 256.0 ± 3.2 Ma. 相似文献
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Fedotova A. A. Bogdanova S. V. Claesson S. Anosova M. O. Postnikov A. V. Fugzan M. M. Kirnozova T. I. 《Doklady Earth Sciences》2019,488(1):1123-1127
Doklady Earth Sciences - This data on the age of metamorphism of rocks of the Yelabuga zone and the geochronological data on detrital zircon from paragneisses of the same zone are presented, and... 相似文献