ABSTRACT

Three prominent periods of Mesozoic carbonate shelf development in the Gulf Coast are represented by the Smackover-Haynesville, the Hosston-Sligo and the Glen Rose-Edwards-Georgetown. In spite of obvious differences in character of shelves of these three intervals, certain similarities of depositional pattern should be helpful in predicting stratigraphic trends in unexplored areas or at untested depths. The most useful parameters for mapping were found to be percentages of the carbonate section having (1) dolomite and (2) oolites. Regionally the depositional patterns and consequent porosity patterns were dependent on climate and supply of clastics as well as on water depths and the distribution of the Louann salt. Smackover depositional and structural patterns were affected by faults involving the pre-Mesozoic rocks. Reefs and shellbanks became more important in determining depositional patterns in the Cretaceous. Reef distribution appears to be related to the extent of the salt dome basins.

As additional subsurface control becomes available, patterns of reefing will be found to be more complex than can be demonstrated at present, with a possibility of echelon arrangement of some barrier reefs, and with more of the reefing demonstrably related to salt movement. There is also a possibility that some of the earliest salt movement may be related to loading by growth of thick carbonate shelves, as well as to triggering by movement on major faults.

The present economic limitations in some of the carbonate trends will be overcome by improved deep drilling techniques, more effective seismic methods, particularly at great depths and in the salt dome basins, and by new knowledge of the regional geology as a factor in determining porosity patterns.