The discovery through the JOIDES drilling program that the Sigsbee Knolls and domes represent intrusive salt bodies has made it necessary to review many old concepts concerning the structural evolution of the Gulf of Mexico. The debate concerning the physiography of the Gulf during the time of salt deposition is now more heated than ever. It has been suggested that, during this time, the Gulf was an ocean basin, a shallow sea, a landmass, or an ocean that had risen to shallow depths above a rising convection cell. Any one of these hypotheses must be able to explain the presence of salt, at least under part of the central basin, if it is to be considered seriously. The possibility that thick salt beds can be deposited at oceanic depths has been questioned. Although at firs thought this may discount a hypothesis that places the Gulf basin at great depth during Triassic-Jurassic time, the structure of the bordering continental slopes of the western Gulf suggests an alternate hypothesis: the Gulf is an oceanic basin along the western margins of which great amounts of salt accumulated. This salt migrated toward the basin. The distribution of salt diapirs throughout the area of subsurface salt is controlled mainly by sediment thickness and the distribution of massive carbonate sequences. The change from simple ridge structure to diapir swarms, south to north along the eastern coast of Mexico, indicates the influence of the sedimentary cover. The abrupt termination of the diapirs on the southeast in the Bay of Campeche and the position of the Sigsbee Knolls and domes indicate the important (negative?) role played by the carbonate platforms in the distribution of salt diapirs.

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