Depression Deposits of the Osinsky Horizon as a Potential Source Rocks of the Baykit High Province (East Siberia)

The purpose of this publication is to present the new geological and geochemical data on Potential source rocks of the Osinsky horizon of the Lena-Tunguska province. The Osinsky horizon of the Lower Cambrian within the Siberian craton has a complex facies structure and is represented by three main types of sections: shallow (arched), reef and depression. When drilling a new exploration and evaluation well at the Salair area (the southern part of the Kamov arch), from the depression-type section of the Osinsky horizon, continuous core sampling was performed, and for the first time for the Baykit High Province, detailed characteristics of potential source rocks were obtained. In the exposed section, the Osinsky horizon has a reduced thickness (12.5 m), and three members are identified in its composition. Weakly porous microbial dolomites with signs of oil saturation were identified in the middle member. The upper member is composed of dark gray and almost black limestones with characteristic signs of condensed anoxic sedimentation (micrite structure, micro-layered texture, absence of remains of benthic organisms, abundance of pyrite framboids, etc.). Numerous spherical remains of calcareous microplankton are found in it. Geochemical methods proved the rocks of the Osinsky horizon depression section are mainly oil-generating. According to the results of geochemical studies, it has been established that the Osinsky petroleum system in the research area is isolated from the underlying Vendian and Riphean deposits. The presented results are highly relevant, as they provide new information about poorly studied depression-type deposits of the Osinsky horizon of the Baykit High Province.

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