ABSTRACT

Despite awareness of the importance of continental extension during rifting, there are few quantitative studies that show the influence of crustal extension on basin architecture, the distribution of salt, and Late Jurassic sedimentation in the DeSoto Canyon Salt basin, northeastern Gulf of Mexico. Application of simplified isostatic principles using a lithospheric buoyancy model allow quantification of total tectonic subsidence, crust thickness, crustal extension, and crust type. Interpretation of over 4800 km of migrated multifold seismic reflection profiles and well data, integrated with computed isostatic relations, provide the basis to characterize Middle Jurassic (Callovian-age) salt halokinetic processes and to describe the structural development of overlying Upper Jurassic strata.

An average crustal thickness of 25 km and crustal extension values between 1.4 and 1.8 suggest the sedimentary succession is underlain by moderately stretched and attenuated continental crust. The widespread distribution and geometry of dipping subsalt reflectors, particularly in the shelfal areas, provide evidence for a Late Triassic-Early Jurassic phase of rifting prior to deposition of Middle Jurassic salt. The distribution of autochthonous salt and the overlying Upper Jurassic sediments reflect the presalt structural imprint and suggest that the basic architecture of the basin was established by the Middle Jurassic following significant attenuation of the crust. Although deposition occurred in a slowly subsiding, stable marginal setting, salt movement and associated growth faulting are the most significant tectonic elements affecting the stratigraphic and structural development of the overlying strata, Faults related to growth of salt structures root at the base of salt in what appears to be a common detachment or decollement for salt movement. The original distribution of salt is widespread and sheetlike with an estimated minimum thickness of 760 m. Progressive basinward subsidence of the margin and differential sediment loading by the overburden are the primary mechanisms initiating mobilization of salt and subsequent deformation of sediments during the Late Jurassic and from the Late Cretaceous through the early Cenozoic.

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