The influence of late cimmerian folding upon stratification of early neocomian deposits in West Siberia

The article reviews consistent pattern of thickness variation of Berriasian-Lower Valanginian in West Siberia. The paper specifies expansion zones related to palaeodepressions of Late Cimmerian deposition. The presence of such depressions became crucial in perception of Neocomian sedimentation trends. It resulted in justification of Achimov formation variative ages (deep-sea Neocomian sands) and reiterated validity of Neocomian structure clinoform model for West Siberia.
Materials and methods
Authors employed CDP seismic reflection data - regional to high-density 3D, processed via advanced software and hardware packages along with well records, and sequence stratigraphy analysis practices.
Results
Geoseismic review by the authors of structural features and thickness variationof Early Neocomian deposits within West Siberian Basin revealed the presenceof peculiar tectonic paleostructures of Late Cimmerian deposition affecting said thicknesses. These structures exhibit intricate history of tectonic movements,initial downwarping to be replaced - in selected areas - by active uplift accompanied by washing-out of earlier sediments. Distribution analysis confirmed that the structures congregate as a linear zone subparallel to the Ural fold system and its northern extension including Novaya Zemlya and Taimyr Peninsula [10]. The existence of such zone gives way to fresh interpretation of certain structural features of Neocomian deposits within West Siberian Basin.
Сonclusions
Updating the morphology of Early Neocomian deposits within West Siberian Basin permitted: More reasonable mapping of deep-seaNeocomian sands of Achimov formation and associated traps and reservoirs based on geoseismic data. Confirmation of Neocomian structure clinoform model for West Siberia proposed by A.L Naumov validityfor Achimov formation whose sand beds in the east of West Siberian Basin are of Berriasian age, while central and western sands are Hauterivian- Barremian. Occurrence of tectonic Late Cimmerian depressions with substantial Berriasian-Lower Valanginian deposits (up to 300 m thick) and bitumenosity lead to assume internal generation and related REE.