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Basement-Driven Deformation of the Sedimentary Sequence in North-Central Oklahoma


Structures rooted in the crystalline basement may control the faulting and folding within the overlying sedimentary cover. Due to the difference in mechanical properties and structural evolution between the basement and the sedimentary rocks, the deformation styles of the two domains may vary with profound implications for fluid migration, reservoir properties, and seismic activity. This study focuses on the understanding of the structure of the deeply-buried (~2 km of sedimentary cover) Precambrian basement in north-central Oklahoma. We analyze 3-D seismic reflection data in an area of 820 km2 and characterize the basement-rooted faults in both the sedimentary and basement sections and discuss their evolution. The analysis shows that 1) the major faults, >10 km long, in the study area are dominantly steeply-dipping; 2) the basement-rooted major faults offset both intra-basement igneous sills and parts of the overlying sedimentary sequence; 3) the throw of the basement faults (using the sills as strain markers) are larger than those in the sedimentary cover; 4) fault-related deformation in the sedimentary sequence is characterized by vertical and lateral offsets and flexure that gradually decrease up-section; and 5) the offset along a fault varies at the proximity of other major faults. The vertical and lateral distribution of offsets along the mapped basement-rooted faults suggest that these faults are likely strike-slip faults that developed during the Precambrian and were reactivated during the Phanerozoic. Finally, we suggest that this reactivation was facilitated by the mechanical coupling between the basement and the lower parts of the sedimentary sequence that allowed for the upward fault propagation.