The Suwannee basin developed in Mesozoic time as a broad syncline on a smoothly eroded Paleozoic terrane. It is in the eastern Gulf Coast area and includes parts of Florida, Alabama, and Georgia. Its axis extends northeasterly from Apalachicola, Florida, into southwestern Georgia.

Deep drilling in the eastern Gulf Coast region has penetrated the Tertiary and Mesozoic section, but wells seldom have extended very deeply into pre-Mesozoic rocks. Geophysical Service Inc. conducted a survey in the Suwannee basin consisting of reflection-seismic profiles plus gravity and magnetic readings. The seismic sections provided the basic framework for a geologic interpretation. Drilling information helped to establish control for the upper part of the sections, and also aided in verifying interval-velocity determinations. Velocity analyses were spaced one mi apart, with about 14 interval determinations at each point. These computations permitted display of the sections in depth as well as time. Models of gravity and magnetic fields were generated by computer programs which pe mitted comparison of interpreted and observed fields. Thus the geologic interpretation could be altered to test various hypotheses, and refinements continued until were reconciled.

Our interpretation shows Tertiary and Cretaceous sedimentary rocks lying upon a remarkably smooth unconformity developed across Paleozoic and Triassic rocks. The unconformity dips southward from a depth of 2,560 m near the Alabama-Florida boundary to about 3,600 m near Panama City, Florida. Below the unconformity is a folded and faulted sequence of lower Paleozoic rocks and Triassic continental strata accompanied by volcanic flows or intrusives. Paleozoic rock types appear to include volcanics, quartzite, and a sandstone-shale sequence. Individual structures are large and varied, and include broad anticlines developed above thrust faults. The Paleozoic rocks are correlated with African counterparts, and it is suggested that their hydrocarbon potential warrants further investigation. >

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