Salt intrusions derived from the Louann Salt of Jurassic (?) age are abundant in the Gulf coastal plain and are found from Texas to Alabama. Evidence suggesting that the Louann Salt may extend into the western Florida Panhandle includes the following.
The Mississippi Interior Salt Dome basin strikes directly toward the western Florida Panhandle: the easternmost proved salt dome in this basin is only 32 miles away.
Small round topographic highs occur on the continental shelf off the Florida coast; some of these may be related to salt domes.
Seismic-reflection measurements reveal the presence of two anticlinal structures, one very broad, the other dome-like, on the continental shelf south of the western Florida Panhandle; there is a strong possibility (not yet proved) that these are related to salt domes or ridges. The broad structure is cut by graben faults.
A recently discovered domal structure broken by a northwest-trending graben is centered under the town of Jay in Santa Rosa County. The faults are similar to those that occur over known salt domes in Texas and Louisiana.
The faults making up the Pollard graben, which extends from Alabama into northern Santa Rosa County, Florida, are of a type that could have been caused by repeated flowage of salt resulting from sedimentary loading during subsidence of the Gulf Coast geosyncline. These faults are contemporaneous; that is, the faulting took place during deposition of the beds that are now displaced. The faults are characterized by: (a) numerous small offsets that occurred at least from Late Cretaceous through middle Oligocene time; (b) increasing throw with depth; and (c) thicker downthrown beds compared with the correlative upthrown beds. Currie (1956) has demonstrated that grabens composed of contemporaneous faults may be produced by upward-moving salt plugs.
Gravity minima which may be caused by salt domes are present in westernmost Florida and southwestern Alabama.
The three deepest oil test holes in Escambia and Santa Rosa Counties, Florida, were drilled to depths of about 12,500 feet and reached total depth in the Hosston Formation of Early Cretaceous age. An oil well in the Citronelle field, Alabama (about 38 miles northwest of Florida) reached the Louann(?) Salt at about 19,000 feet. Thus, if the salt is present in the western Florida Panhandle, it probably is at least 6,000 feet deeper than the greatest depth so far reached by drilling.