ABSTRACT

The origin of the Bahama platform and its continued subsidence to permit the accumulation of a thick carbonate cap has been a problem of middle American geology. The relation of this feature to previously published reconstructions of the late Paleozoic-early Mesozoic "fit" of North America, Africa and South America has also posed a problem. A new model incorporating the volcano-tectonic rift and ignimbrite sheet association is proposed to explain the origin of the Bahama platform as an integral part of Caribbean plate tectonics. A new North America-South America join is utilized to account for the major geologic and tectonic continuities of Paleozoic age throughout Mexico and Central America.

The clockwise rotation of North America as it separated from South America and Africa caused the counterclockwise bending of the entire peninsula of Mexico and Central America, with the newly accreted Caribbean plate into a subduction zone that was to evolve into the are-trench system of the Greater Antilles. The rotation and beginning of subduction of this Caribbean plate into the Cuban trench, in Jurassic time, triggered volcanic eruptions that provided the foundations for the Cuban volcanic arc and the usual thick and widespread ignimbrite sheet behind the arc in the area now occupied by peninsular Florida and the Bahama Banks.

Not only is evidence for this feature found in wells drilled in Florida but it also provides the foundation upon which was deposited the thick sequence of carbonate strata that forms the Bahama Banks. This interpretation eliminates the overlap of the Bahama salient onto Africa, explains the origin of the Old Bahama Channel, serves the same purpose as the sedimentary prism proposed by Dietz and others (1970) and has the volcanic character to meet the geophysical requirements indicated by Uchupi and others (1971).