The structure of cambrian deposits of the Vilyui hemisyneclise, based on an integrated analysis of drilling and seismic data

We present a model of the stratigraphic and lateral distribution of Cambrian deposits in the Vilyui hemisyneclise, based on an analysis of drilling data and interpretation of seismic data. The study shows a series of formations and sequences penetrated by wells (Syugdzher saddle, Khorgochum monocline, Ygyatta depression, Tyukyan–Chybyda monocline, Arbai–Sinyaya megaswell, etc.). In the areas where the Cambrian was not penetrated by wells, the distribution of Cambrian deposit was inferred based on the available seismic data. The distribution of the Kuonamka Horizon formed by Cambrian organic-rich rocks is characterized in detail. These are the Kumakh and Sinyaya–Kutorgina sequences and the Inikan and Kuonamka formations. It has been found that the Kuonamka Horizon was deposited during two stages, Botomian and Toyonian–early Mayan. The horizon is overlain by younger deposits of the Mayan Stage, with character-istic cross-bedding structures. Schemes of facies zoning of the Cambrian for Botomian, Toyonian–early Mayan, and middle Mayan times were constructed based on the most recent geological and geophysical understanding of the Vilyui hemisyneclise.