In the western Gulf basin, the pre-Jurassic section can be subdivided into (1) foreland Paleozoic strata (Black Warrior basin), (2) orogenic geosynclinal facies (Ouachita tectonic belt), (3) late-orogenic, late Paleozoic rocks, and (4) post-orogenic, Late Triassic strata.

A good potential for future petroleum provinces of economic interest can be recognized in the Black Warrior basin, and on the Gulf of Mexico side of the Ouachita tectonic belt, in late-orogenic, late Paleozoic strata. A remote possibility is recognized for the presence of commercial accumulations of hydrocarbon in sub-thrust lower Paleozoic foreland carbonates beneath the interior part of the Ouachita fold belt. The hydrocarbon potential of geosynclinal sediments of the Ouachita tectonic belt, and of the post-orogenic Triassic section, is considered to be negligible.

The Black Warrior basin of Mississippi and Alabama contains a thick section of Paleozoic foreland rock. Although production dates back to 1909 and hydrocarbon shows have been numerous, the proved reserves are insignificant.

The deep structural configuration has been difficult to map, and this has deterred deep drilling. The basin tectonics should be comparable to those of other foreland basins, in which large, buried, normal faults are characteristic. Improved seismic techniques should reveal similar anomalies in the Black Warrior basin. Large hydrocarbon accumulations may ultimately be found in deep fault traps in lower Paleozoic carbonates, and such prospects are sparsely tested.

There is no production from pre-Jurassic rocks gulfward from the Ouachita front. However, exploration of this section has been quite limited, mainly because of the absence of attractive objectives. Most wells drilled below the Jurassic have found either tight, highly deformed, geosynclinal facies of the Paleozoic Ouachita system, or redbeds and igneous rocks of the Late Triassic Eagle Mills Formation.

Since 1960 a few highly significant, but unpublicized, wildcats have penetrated relatively undeformed, very fossiliferous, shallow-water shelf carbonates and clastics of Pennsylvanian age beneath the coastal plain. These strata, identified from fusulinids as Desmoinesian, are present on the Gulf of Mexico side of the Ouachita fold belt in wells drilled in northeast Texas and southwest Arkansas. Commercial porosities have been found in both sandstones and carbonates. Only fragmentary data are available, but the mere presence of these strata suggests that a potentially large, virtually unexplored, petroleum province may be present in late Paleozoic rocks of the Gulf coastal plain.

End_Page 1792------------------------------

A recent 20,000-ft test in Texas penetrated thick lower Paleozoic shelf carbonates on a large seismic anomaly beneath the interior zone of the Ouachita system. Although the objective carbonates were metamorphosed there, the possibility of finding favorable reservoir rock elsewhere in this trend is not necessarily eliminated.

End_of_Article - Last_Page 1793------------