Berriasian-aptian deposits of the West Siberian Yenisei-Khatanga region: stratigraphy, correlation, and zoning

The authors discuss topical issues of stratigraphy, correlation, and structural and facies zoning of the Berriasian-Aptian deposits in the north-eastern regions of the West-Siberian Petroleum Basin. Based upon the model of the Neocomian clinoform architecture in Western Siberia, recommendations to update the structural and facies zoning and stratigraphic chart for the Yenisei-Khatanga region are made. Selection of section types is taken as a basis for structural and facies zoning of the West Siberian Berriasian-Aptian deposits. Accordingly, it is proposed that subregion boundaries within the Yenisei-Khatanga region should be drawn along the lines of transition from the Lower Cretaceous shallow-marine horizontally stratified to clinoform deposits. The new stratigraphic chart of the Berriasian-Aptian deposits is presented for the Yenisei-Khatanga region. It differs from the chart approved in 2005 by the Interagency Commission on Stratigraphy in the fact that position of the Lower Cretaceous formations’ boundaries are updated, as well as the section breakdown is more detailed. Regional clay units are added to the chart, and separate beds or their groups are shown in the Malokhetsky and Baikalovsky formations. Moreover, similar to the Berriasian-Aptian stratigraphic charts for the West Siberian Basin, the proposed chart shows the sub-Achimov, Achimov, and above-Achimov series