Paleoecology is the relationship between ancient organisms and their environment. Interpretation of the depositional environments of foraminiferal species in the geologic section is based largely on information calibrated from studies of the habitat of Recent Foraminifera. In Gulf Coast clastic rocks, oil and gas occur most commonly in strandline or nearshore sediments composed of interbedded transgressive shallow-marine and regressive non-marine strata. Large deltas that formed in rapidly subsiding basins are typical of this environment. In carbonate rocks, reefs with backreef bays and lagoons in brackish- and shallow-marine environments are favorable for oil and gas occurrence.

Accurate paleoecologic interpretation depends on sufficient knowledge and consideration of the associated lithologic types, sedimentation, and tectonics which are related components of stratigraphy. Gulf Coast sedimentation occurred in a mediterranean basin, and structural features, both regional and local, have affected deposition. An estimated 40,000 ft. of Cenozoic clastic sandstone and shale underlying the Texas-Louisiana coast thins eastward to a thickness of approximately 5,500 ft. under Florida where the terrigenous rocks grade into carbonate rocks. Eight major transgressive-regressive cyclic depositional units comprise Gulf Coast Cenozoic sedimentation; the units are Midway-Wilcox, lower Claiborne, upper Claiborne, Jackson, Vicksburg-Frio, Anahuac, Fleming, and Quaternary. Pal oecologic or depositional environment zones are classified as transitional, inner shelf, middle shelf, outer shelf, upper slope, lower slope, and abyssal.

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