The Jurassic–Cretaceous terrigenous complex of the Laptev and East Siberian Seas is of considerable interest as a potential exploration target. However, the key Jurassic and Cretaceous sections of the New Siberian Islands have been poorly studied. The results of this study were used to provide a detailed micropaleontological description of these sections and substantiation of the previous lithostratigraphic subdivision. We first identified a series of Boreal standard zones in the Jurassic and Cretaceous sections, based on the foraminifers, ostracods, dinocysts, and terrestrial palynomorphs. Our results, along with the published data on ammonites, bivalves, and terrestrial palynomorphs and the results of radiometric dating, provide more precise constraints on the stratigraphic position of the identified lithostratigraphic units. The results of this study can be corroborated by seismic data to explore offshore areas of the Laptev and East Siberian Seas. We also present detailed data on the geochemistry of organic matter from the Pestsovaya Formation (Hettangian–lowermost Upper Pliensbachian).

Mesozoic sections in the New Siberian Archipelago are important for understanding of the geology of underexplored shelf areas in the east of the Laptev Sea and in the west of the East Siberian Sea. They are reference sections for interpretation of seismic data in these regions. However, there are still many unresolved problems concerning the lithology, lateral extent, and age of Mesozoic deposits, as the sections have a complex structure and are heavily deformed. The performed research makes a basis for the first facies zoning of Jurassic and Cretaceous deposits in the New Siberian Islands and adjacent landmasses of continental Siberia at the junction of the Laptev and East Siberian Seas. The lithostratigraphic division of the Jurassic and Cretaceous is refined, being proposed for the first time for some stratigraphic intervals, and allows updating their lithostratigraphic division (or undertaking it for the first time for some stratigraphic intervals). Facies features of Jurassic and Cretaceous deposits allow the definition of three depositional series.

We present organic geochemical data (vanadyl and Ni‐porphyrin contents, pristane/phytane ratios and n‐alkane compositions) relating to oils from Palaeozoic reservoirs in the SE West Siberian Basin. Analogous data from organic material in Palaeozoic and overlying Jurassic source rocks is also presented. The Jurassic succession here consists of siliciclastic units deposited during alternating marine transgressions and regressions. Our results indicate that vanadyl and Ni‐porphyrins occur predominantly in transgressive units, and that pristane/phytane ratios increase progressively up through the Jurassic section. However, for Jurassic sediments in which vanadyl porphyrins are present, the Pr/Ph ratio is strongly facies dependent and is relatively high in transgressive units and lower in regressive units. By contrast, (C21+C23+C25)/3C20 n‐alkane ratios are relatively low in transgressive deposits and higher in regressive deposits. There is a close relationship between this parameter and Pr/Ph ratio. Oils from weathered Palaeozoic reservoirs have variable compositions. In most cases, these compositions appear to be influenced by the depositional characteristics of the overlying Jurassic source intervals. Our data point to a mainly Jurassic origin for the oils in SE Western Siberia. However there is some evidence that a Palaeozoic source may be significant in the south of the studied area.

The study of Triassic paleontology and stratigraphy of various regions of northeastern Russia and adjacent Arctic shelf is essential not only for improving and refining zonal biostratigraphic schemes, interregional and global correlation of Triassic deposits, and resolving problems of stratigraphic boundaries but also for developing and substantiating a new generation of Triassic stratigraphic schemes, which could serve as the stratigraphic basis for different regional and detailed geological investigations of the Arctic. The results of the study were used to improve existing zonal scales based on various groups of fauna and palynomorphs, develop a more detailed biostratigraphic subdivision of the Triassic, and characterize individual horizons using both terrestrial and marine palynomorphs. The zonal scales are calibrated to each other and to the regional zonal scale of the Triassic of Siberia and northeastern Russia, which provides the subsequent correlation with the International Chronostratigraphic Chart of the Triassic System. The set of coeval zonal scales for the Triassic of Kotelny Island sections based on ammonoids, nautiloids, coleoids, bivalves, brachiopods, and foraminifers and the analysis of microphytoplankton and terrestrial palynomorph assemblages are a useful tool for detailed subdivision and correlation of the eastern part of the Laptev Sea shelf and adjacent regions of northeastern Russia.