The area of the Laptev Sea is a continental margin platform. The borders are of various ages and genesis. On the west is the Taymyr-Severnaya Zemlya fold system; on the south is the Siberian craton, Lena Delta, and mountainous structures of the Northeast Russian Mesozoids; and on the east are block uplifts of Kimmerian age, which extend on up to the North Siberian Archipelago and Lomonosov Ridge. Within the area of the sea are numerous structural highs and lows.
The most complete sedimentary section in the Laptev basin is in the South Lapterv downwarp. A 185-kilometer refraction profile was run in1979 northeastward from the mouth of Anabar River. Three refraction horizons were recognized.
The upper of these horizons has an interface velocity of 3.9-4.0 kmps and is at the boundary between Lower Triassic clays and Middle Triassic sands. The Lower Triassic also contains pyroclastic material from the basaltic volcanism of northern Siberia of this time.
The middle of these horizons with an interface velocity of 4.6-5.0 kmps correlates with the boundary between Upper Paleozoic clastics and Middle Paleozoic carbonates. This boundary is actually between Middle and Lower Carboniferous.
The lower horizon with an interface velocity of 6.0-6.8 kmps appears to be within the basement at the boundary between Lower Proterozoic schists and Archean gneisses.
The sedimentary cover and basement of the South Laptev downwarp appears to be identical to the cover and basement of the Siberian craton.
Four stratigraphic complexes are recognized on the Laptev platform: Upper Cretaceous-Cenozoic, Upper Paleozoic-Lower Cretaceous, Vendian-Middle Paleozoic, and Riphean.
The Upper Cretaceous-Cenozoic complex is estimated to be 3.0-3.5 km thick in the Ust'-Lena trough. On a basis of onshore observations it is assumed to be clastics, which contain plant fragments. The Upper Cretaceous part of this section is up to 1 km thick.
The Upper Paleozoic-Lower Cretaceous complex consists of marine and continental sandstone, siltstone, argillite, and coal. It is not more than 3 km thick.
The Vendian-Middle Paleozoic complex in the Laptev basin is expected to consist of marine and lagoonal clay-carbonates and evaporites (Lower and Middle Devonian). Bituminous rocks of Domanik facies should be present in the Vendian and Middle Devonian. Thickness of this complex is estimated at 3 km.
The Riphean, which is known onshore, may or may not extend offshore. It is not recognizable there on the seismic profiles, but this may be due to merging with the Vendian. If present offshore, it should consist of clastic-carbonates with reef limestones. Thickness should be not more than 1 km.
Taken from V. A. Vinogradov,1986, one trctonic map and one
cross section; digested in Petroleum Geology, Vol. 23, No. 5/6.
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