Tectonic evolution of the Anadyr Basin,northeastern Eurasia,and its petroleum resource potential |
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| Authors: | M P Antipov G E Bondarenko T O Bordovskaya E V Shipilov |
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| Institution: | (1) Faculty of Geology Leninskie Gory, Lomonosov Moscow State University, 119992 Moskva, Moscow, Russia |
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| Abstract: | The published data on the sedimentation conditions, structure, and tectonic evolution of the Anadyr Basin in the Mesozoic
and Cenozoic are reviewed. These data are re-examined in the context of modern tectonic concepts concerning the evolution
of the northwestern Circum-Pacific Belt. The re-examination allows us not only to specify the regional geology and tectonic
history, but also to forecast of the petroleum resource potential of the sedimentary cover based on a new concept. The sedimentary
cover formation in the Anadyr Basin is inseparably linked with the regional tectonic evolution. The considered portion of
the Chukchi Peninsula developed in the Late Mesozoic at the junction of the ocean-type South Anyui Basin, the Asian continental
margin, and convergent zones of various ages extending along the Asia-Pacific interface. Strike-slip faulting and pulses of
extension dominated in the Cenozoic largely in connection with oroclinal bending of structural elements pertaining to northeastern
Eurasia and northwestern North America against the background of accretion of terranes along the zone of convergence with
the Pacific oceanic plates. Three main stages are recognized in the formation of the sedimentary cover in the Anadyr Basin.
(1) The lower portion of the cover was formed in the Late Cretaceous-Early Eocene under conditions of alternating settings
of passive and active continental margins. The Cenomanian-lower Eocene transitional sedimentary complex is located largely
in the southern Anadyr Basin (Main River and Lagoonal troughs). (2) In the middle Eocene and Oligocene, sedimentation proceeded
against the background of extension and rifting in the northern part of the paleobasin and compression in its southern part.
The compression was caused by northward migration of the foredeep in front of the accretionary Koryak Orogen. The maximum
thickness of the Eocene-Oligocene sedimentary complex is noted mainly in the southern part of the basin and in the Central
and East Anadyr troughs. (3) The middle Miocene resumption of sedimentation was largely related to strike-slip faulting and
rifting. In the Miocene to Quaternary, sedimentation was the most intense in the central and northern parts of the Anadyr
Basin, as well as in local strike-slip fault-line depressions of the Central Trough. Geological and geophysical data corroborate
thrusting in the southern Anadyr Basin. The amplitude of thrusting over the Main River Trough reaches a few tens of kilometers.
The vertical thickness of the tectonically screened Paleogene and Neogene rocks in the southern Main River Trough exceeds
10 km. The quantitative forecast of hydrocarbon emigration from Cretaceous and Paleogene source rocks testifies to the disbalance
between hydrocarbons emigrated and accumulated in traps of petroleum fields discovered in the Anadyr Basin. The southern portion
of the Anadyr Basin is the most promising for the discovery of new petroleum fields in the Upper Cretaceous, Eocene, and Upper
Oligocene-Miocene porous and fracture-porous reservoir rocks in subthrust structural and lithological traps. |
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