Structure and genesis of the Achimov olistostromic strata of Western Siberia

The question of the genesis of the anomalous Bazhen-Achimov zones remains to be one of the most controversial problems in Western Siberia. By now, about dozen hypotheses of the sedimentary environment of this specific formation have been proposed. However, none of these hypotheses is generally accepted. All hypotheses have been classified by genesis and their critical analysis is given in the article. The solution is closely related with experience of the geological exploration works, since the prospects of oil and gas are associated with these deposits. The article highlights the key features of the structure of the anomalous section’s zones based on drilling and seismic data. The classification of the hypotheses is given and the features of sedimentation in the Bazhenov and Achimov times are highlighted. An accumulated data has allowed us to substantiate the olistostromous genesis of the anomalous section. Based on a set of data, including paleogeographic, sedimentological, paleotectonic reconstructions, a principal detailed model of the sedimentary environment of olistostromes is proposed for the first time. The proposed model seems to be the most logical, supported by the actual data known to date, is the most universal and fits into the paleogeographic situation and tectonic regime that prevailed in the Achimov time.