Biostratigraphy, Lithology and Geochemistry of the Lower and Middle Cambrian Rocks in the Kyulenke River Basin: First Results of Borehole Core Study

Abstract —We have studied biostratigraphy, lithology and geochemistry of drill cores from the Kyulenke River basin. The study of fossil remains and rock compositions, the analysis of trilobite distributions and changes in the lithological and geochemical characteristics of the sediments made it possible to identify structural features of the marker horizons, to correlate borehole sections and outcrops, to compare individual Cambrian intervals and the regional zones of the Yudoma–Olenek facies region of the Siberian Platform. The study has shown rocks of the Kuonamka Fomation to be enriched in uranium (U) and revealed a direct relationship between the contents of U and organic carbon (Corg) in the analyzed rocks, typical for the lower and middle Cambrian black shale deposits sampled from the outcrops in the eastern parts of the Siberian Platform. For the first time, a relationship of rock radioactivity by gamma-ray logging with the contents of U and Corg in Cambrian rocks was established.