Use of T-R Sequence Methodology in the Analysis of the Onshore Interior Salt Basins of the Gulf of Mexico

Mancini, Ernest A.¹ (1) University of Alabama, Tuscaloosa, AL

Stratigraphic analysis is critical in the reconstruction of the geohistory of a sedimentary basin. For the onshore interior salt basins of the northern Gulf of Mexico, where the stratigraphic section is characterized primarily by non-marine and coastal sediments deposited in shelfal areas and where stratal architecture is affected by changes in sediment supply, climate and tectonics, in addition to sea level changes, a T-R sequence approach is the preferred methodology for basin geohistory reconstruction. The T-R sequence method provides a reasonable means for recognizing changes in stratigraphic base level, which is the key factor affecting stratal architecture in these non-marine and coastal deposits. T-R sequences, their inherent systems tracts and subdivisions (transgressive aggrading and backstepping and regressive infilling and forestepping) and their bounding and defining surfaces (subaerial unconformities, ravinement surfaces, transgressive surfaces, surfaces of maximum transgression and surfaces of maximum regression) provide an improved means for stratal correlation and for the establishment of a chronostratigraphic framework. These systems tracts and their subdivisions are recognizable by characteristic well log signatures and seismic reflection configurations and terminations. The bounding and defining surfaces have chronostratigaphic significance and provide time lines for the analysis of the depositional, tectonic, burial and thermal maturation histories of a given basin. The T-R sequence concept has application in designing enhanced exploration strategies in the recognition of specific continental and coastal facies that have reservoir potential and in the identification and delineation of potential stratigraphic traps.