It is commonly impossible to distinguish structure due to deposition and erosion from tectonic structure. Moreover, stratigraphic agents producing trap limits are usually dependent on tectonic influences. It is thus impractical to contrast stratigraphic versus structural traps with the intention of searching for one type and not searching for the other. This is most clear in the case of carbonate traps where tectonism controls development of both erosional and depositional structure and affects depositional and diagenetic facies distribution.

In the Florida-Bahamas carbonate province, intra-platform straits and basins are sites of negative residual Bouguer gravity anomalies. A correlatable refractor near the top of Lower Cretaceous rocks is depressed in these same areas. Thus, present topographic lows overlie structural lows in the platform's foundation. Similar relations are indicated for the Tampico-Tuxpan and Scurry reef platforms and are markedly evident in the Central Basin platform and the Leduc-Rimbey trend. This relation is a potentially useful one, because the geophysical anomalies reflecting the structures which control the position of the platforms commonly exceed those stemming directly from carbonate masses.

Depositional and, to a degree, diagenetic facies have consistent topographic settings in both recent and ancient platforms. Calcarenites predominate at the edge; calcilutites and evaporites are most common in the platform interiors. Bases of platform-edge slopes are typically sites of deposition of allochthonous shallow-water sands mixed with coarse rubble containing balls of pelagic mud. Elevated edges commonly are leached and dolomitized, and dolomite is present in many places within the platform-interior evaporites. Great quantities of hydrocarbons have been found in the leached and dolomitized platform edges, in porous and permeable platform-interior dolomites, in dolomitized conglomerates bordering bases of platform slopes, and in fractured reservoir rocks in adjacent basin facie .

The requirements for an oil field are structure, reservoir, seal, and a commercial quantity of hydrocarbons. Geophysical tools are best suited to discern structure. Velocities and reflection character also provide some insight to lithologic variations. Outcrop and subsurface studies enable mapping of distribution of reservoirs and seals. Slabbed cores from ancient carbonate rocks reveal sedimentary structures identical with those observed in recent carbonate units. Thus, study of modern carbonate deposits is a valuable aid in interpretation of rocks, and slabbed cores are essential for a detailed understanding of carbonate depositional and diagenetic history. Temperature and hydrocarbon-generating history of source beds can be discerned from the nature of organic matter remaining afte oil and gas are gone. Knowledge of this relation enhances the ability to predict types of hydrocarbons to be encountered in a given region.

Prospects for testing must be chosen on the basis of areal extent of structure and the regional distributions of reservoirs, seals, and hydrocarbons. Finally, management and backers should be prepared to drill two or three evaluation wells following the completion of a successful wildcat in a carbonate reservoir.