PROBLEMS OF OXFORDIAN AND KIMMERIDGIAN STRATIGRAPHY IN NORTHERN CENTRAL SIBERIA ( Nordvik Peninsula section )
B.L. Nikitenkoa, V.G. Knyazevb, N.K. Lebedevaa, E.B. Peshchevitskayaa, and R.V. Kutyginb
aA.A. Trofimuk Institute of Petroleum Geology and Geophysics, Siberian Branch of the Russian Academy of Sciences, pr. Akademika Koptyuga 3, Novosibirsk, 630090, Russia
bDiamond and Precious Metal Geology Institute, Yakutsk Scientific Center, Siberian Branch of the Russian Academy of Sciences, pr. Lenina 39, Yakutsk, 677891, Russia
Keywords: Oxfordian, Kimmeridgian, reference section, stratigraphy, ammonites, foraminifers, dinocysts, zonal scales, Nordvik Peninsula, Central and East Siberia
Pages: 963-978
Abstract
The Oxfordian-Lower Hauterivian section of the Nordvik Peninsula (northern Central Siberia) is a reference for developing zonal scales for various fossil groups and improving the Boreal zonal standard. In the middle 1950s-late 1980s, it was studied extensively by geologists, stratigraphers, lithologists, and experts on various fossil groups. These studies yielded rich fossil and microfossil collections and a set of parallel zonal scales for various faunal groups. Recently, a new detailed ammonite zoning of the Oxfordian and Kimmeridgian units of this section has been proposed. These results contradict the previous biostratigraphic data on ammonites, foraminifers, and palynomorphs. In the present paper, all the biostratigraphic data on the Oxfordian and Kimmeridgian units of the Nordvik Peninsula (Cape Urdyuk-Khaya) and northern Central Siberia undergo a comprehensive analysis and comparison with those on the Boreal Realm. The ammonite-constrained stratigraphic position of the lower Upper Jurassic in the Cape Urdyuk-Khaya section is interpreted as Upper Oxfordian or Middle Oxfordian. In our view, this difference in the understanding is due to the misidentification of some Oxfordian ammonite forms. The zones based on other fossil groups (foraminifers, dinocysts) which were distinguished in the Upper Oxfordian and Kimmeridgian sections of the Nordvik Peninsula are well traceable circumarctically. Their stratigraphic position in various regions of the Northern Hemisphere is constrained by ammonites and bivalves. However, if we use the last alternative ammonite zoning of this part of the section, hardly explicable contradictions will appear in interregional foraminifer and dinocyst correlations.
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