ABSTRACT

The stratigraphic framework of the Mississippi Interior Salt Basin (MISB) was studied to determine the burial and thermal history of the basin. Wireline logs, predominantly SP and resistivity but supplemented by gamma ray, sonic, and neutron/density logs, and lithologic and sample logs from 48 wells comprise the information base. Five cross sections were generated, including a strike section and four dip sections. The geographic extent of the dip sections allows tracking formational changes in the basin, particularly the change from predominantly siliciclastic to carbonate sediments which most of the formations display, and the diachroneity of the formational contacts.

Figure 1. Time-stratigraphic cross section of Mississippi Interior Salt Basin along generalized line from Yazoo County to the Wiggins Arch in George County, Mississippi.

The change from siliciclastic to carbonate sediments presents special problems when correlating from onshore to offshore regions of the Gulf of Mexico. Typically, formational boundaries in onshore areas can be recognized on the basis of characteristic wireline log signatures that reflect lithologic disparities. South of the Wiggins Arch, where much of the Mesozoic section is carbonate, biostratigraphy is increasingly used to define formational boundaries. Although the presence of microfossils is reported in sample and lithologic logs from many wells and formations in the MISB, very little of this paleontological information has been published and remains an area of future study.

Tectonic subsidence of the MISB occurred largely during the Jurassic and Early Cretaceous, as variances of the thicknesses of these two systems are much greater than that of the Upper Cretaceous System. The literature indicates that other salt basins occurring on thick transitional crust have analogous depositional systems, suggesting that stratigraphic models developed in one basin can be applied to other, less studied salt basins.

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