Regional stratigraphic units are identified in accordance with the 1983 Chart, where the cyclic structure of Vendian deposits is documented, and regional nondepositional unconformities are shown. These criteria allowed substantiating large sedimentation phases, which gained the status of regional cyclothems formed as a result of eustatic warping movements. There were three stages of building a stratigraphic chart of Vendian deposits. In the first of them, a set of correlation lines across the wells is created. Each of the correlation lines demonstrates formation-by-formation, member-by-member, and layer-by-layer stratigraphic structure of each of the wells. In the second stage, interpretation of these composite logs is carried out. A set of charts describe the areas with different completeness of member-by-member and layer-by-layer architecture of the Vendian cross-sections. In the last stage, the detailed stratigraphic chart is created, where lithological and stratigraphic intervals with different structure of Vendian sequence are delineated. For the territory of the Katangsky Petroleum Region, differences in member-by-member architecture of the Vilyuchansky, Nepsky, Tirsky, and Danilovsky horizons, formations, and regional cyclothems are shown. Changes in duration of regional hiatuses between the horizon’s formation are described. As a result, six regional cyclothems are identified in Vilyuchansky, Nepsky, Tirsky, and Danilovsky horizons, namely: Upper Vilyuchansky, Lower and Upper Nepsky, Lower and Upper Tirsky, and Lower Danilovsky. A sequential eastward succession of regional cyclothem formation stages separated by nonsequences is observed in the Katanga Petroleum Province. The cross-sections clearly demonstrate two regional hiatuses, they are: pre-Danilovsky and pre-Vendian-pre-Nepsky. Intra-Nepsky and intra-Tirsky hiatuses separate the Nepsky and Tirsky regional cyclothems. Many members of Oskobinsky and Vanavarsky formations are separated by short-term breaks in sedimentation.

Nikolai V. Mel’nikov
Doctor of Geological and Mineralogical Sciences, Professor
Chief Expert
Siberian Research Institute of Geology, Geophysics and Mineral
Raw Materials,
67, prospect Krasnyi, Novosibirsk, 630091, Russia

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