THE WEST GULF COAST STRATIGRAPHIC RECONCILIATION PROJECT: MAKING SENSE OF INTERSTATE NOMENCLATURE DIFFERENCES

The Geological Survey of Alabama, in cooperation with the Arkansas Office of the State Geologist, the Louisiana Geological Survey, the Mississippi Geological Survey, the Tennessee Geological Survey, and the Texas Bureau of Economic Geology, through funding from the U.S. Geological Survey, is conducting a two-year project to reconcile interstate stratigraphic nomenclature across the west Gulf Coastal Plain (WGCP) and adjacent offshore areas in the southern United States. Mesozoic and Cenozoic stratigraphic units in the WGCP extend from southern Texas to the panhandle of Florida, unconformably overlying a “basement” formed by an assembled Laurentian and Gondwanan terrane. Deposition of the WGCP sedimentary sequence began during initial opening of the Gulf of Mexico in the Triassic. Triassic and Jurassic strata, along with a bimodal suite of Cretaceous igneous rocks, are not exposed at the surface. Cretaceous strata are the oldest units that crop out across the region and these underlie a sedimentary sequence that extends through the Holocene. A working group comprised of representatives from the cooperating partners has identified more than 200 formal and informal stratigraphic units in the WGCP sequence. Geophysical logs from oil & gas and water wells reveal along strike and downdip stratigraphic facies changes that reflect both proximal and distal depositional environments associated with differences in tectonic development of the Gulf of Mexico. A new correlation chart for the region indicates that the majority of stratigraphic nomenclature differences occur in the Cenozoic where individual units can be thin and display frequent facies changes. Naming differences in the Mesozoic part of the section are not as extensive; however, long-standing exploitation of Jurassic and Cretaceous strata for petroleum resources has led to many informal names being used in this part of the section. This presentation will describe the workflow being used to reconcile interstate nomenclature differences, present preliminary results, and describe how the results correspond with an ongoing project in the east Gulf Coastal Plain (EGCP). Results from these projects will improve communication between researchers and advance understanding of temporal and spatial changes within northern Gulf of Mexico strata.