No Abstract Avaliable

Structural and stratigraphic relationships indicated by seismic reflection data suggest that uplift of the Destin Dome anticline resulted mainly from salt movement during Late Cretaceous to Early Cenozoic time. A thick succession of Lower Cretaceous sediment was deposited in the central part of the basin seaward of the present day Destin Dome. Sediment loading squeezed the salt both updip onto the shelf and downdip into the basin. A step in the pre-salt basement limited movement of salt and controlled the location of the dome. Vertical movement of salt was accommodated by extensional faulting. During the Early Cenozoic, sediment touchdown onto the pre-salt basement formed a salt weld between the anticline and the De Soto Canyon diapir field, cut off the supply of salt and stopped growth of the structure. The minimum accumulation thickness of the 'mother'salt is estimated to be 760 m and the original volume of salt deposited at the present day location of the Destin Dome anticline on the Florida shelf is estimated to be 1000 km3. The volume of salt in place today is in excess of 2300 kM3.

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 beta 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

Multifold seismic reflection data provide the basis for recognition of an offshore Late Triassic-Early Jurassic half graben complex beneath the DeSoto Canyon salt basin (DSCSB) along the northeastern Gulf Of Mexico margin. The base of salt or equivalent (BSE) surface is a prominent unconformity recognized throughout the DSCSB that is mostly overlain and onlapped by extensive Middle Jurassic (Callovian age?) premarine evaporites (Louann salt and equivalents) and younger sedimentary rocks. Widespread dipping subsalt reflectors, truncated by the BSE, are the seismic expression of an interpreted thick section of synrift strata deposited within a half graben. The half graben probably overlies older prerift Paleozoic (and Precambrian?) sedimentary, igneous, and metamorphic rocks and widens basinward about a NE-SW axis. Stratigraphic onlap relationships of subsalt reflectors close to the BSE surface suggest a lacustrine sequence may be present in the uppermost section of the rift fill; similar deposits occur within synrift strata below Aptian salt along the rifted West African margin. A NE-ENE striking normal slip boundary fault beneath the Mississippi-Alabama-Florida (MAFLA) shelf area and the inferred NW-SE oriented Florida-Bahamas transfer fault along the eastern margin of the DSCSB approximate the updip limit of rift fill. Trends of these structural lineaments and overall half graben morphology ate similar to those of the South Georgia basin, a buried onshore early Mesozoic graben complex in northern Florida and southern Georgia, and the trend of exposed Triassic-Jurassic continental rife basins along eastern North America. Structural architecture of the DSCSB half graben is consistent with NW-SE rift phase extension during the early Mesozoic opening of the Gulf of Mexico.