--> --> The Post-Neocomian Fill History of the North Chukchi Basin

2018 AAPG International Conference and Exhibition

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The Post-Neocomian Fill History of the North Chukchi Basin


The North Chukchi Basin fill represents an up to 18-20 km thick prism of Cretaceous-Tertiary sediments overlying folded pre-Aptian rocks. Multiple stacked clinoforms making up the cover were studied with the objective to map deltaic sequences and understand their interaction with regional tectonic events. The practical outcome included identification of stratigraphic levels of petroleum play fairways and mapping their elements. Regional seismic 2D dataset was utilized for sequence stratigraphic interpretation. The following workflow was used to study the entire sedimentary section. Initially clinoform topset breaks were marked and joined to define their dynamics, stacking patterns and likely distribution of deltaic sands. Secondly, key surfaces were noted from observations of the stacking patterns to identify sequence boundaries and flooding surfaces. Thirdly, positions of the evolving clinoform breaks indicating episodes of delta outbuilding were used to identify main sediment entry points and location of depocenters in time. The accommodation space in the North Chukchi Basin was produced by multiple tectonic events. The pre-Aptian Chukotkian (Brookian) compression took place to the south of the basin. The uplifted area served as a provenance for the northerly sediment supply to the basin. The following extension/transtension in the basin led to rotational listric faulting creating accommodation space within their hanging walls. The Cretaceous-Tertiary (Mid-Brookian) compression in the Wrangel-Herald Arch area resulted in an oblique north-easterly sediment dispersal relative to the uplifted area. A later event formed extensional rollover anticlines with associated growth strata filled by sediments derived from the south-east which were subsequently overlain by post-kinematic northward prograding deltaics. Thus, the sediments in the basin had diverse origin implying variable sand mineralogy at different levels. A number of possible play fairway scenarios can be established on the interplay between tectonically driven regions of erosion and sediment supply and shifting character of basin fill described above. Areas of deltaic progrades in the south-west, center and south-east of the basin favor prospective play fairways within the delta topsets and seismically bright coals as feasible gas-prone source. The northerly areas feature more marine settings with play fairways related to lowstand bottomsets and downlap surfaces as potential oil-prone sources.