Salt Tongues in Northern Gulf of Mexico

Yun Fei Wang

Salt tongues are generally flat-lying tongue-shaped salt sheets that have been found in the deep-slope area in the northern Gulf of Mexico. These tongues, usually buried at shallow depth, are embedded in Pleistocene, possibly in Pliocene or older, sediments. Their size varies greatly from 5 to over 100 km in length, and from a few tens to over 4,500 m in thickness. Most of the salt tongues are marked by high-amplitude seismic reflectors at the top and sometimes at the base.

A typical salt tongue consists of a feeder, a bulging neck and butt, and a tapering tongue pointing downslope. The salt tongues in the northern gulf are believed to be extrusive in origin. These tongues were formed as a result of updip sedimentary loading from the shelf and upper slope.

A salt tongue probably originates from a diapiric salt dome or from a fault connecting it to the buried mother salt. As the sedimentary wedge progrades downdip toward the slope, the mother salt is mobilized and moves upward. When salt approaches the sea floor, it expands laterally and creeps gradually down-slope under the influence of gravity. The advance of the tongue is sustained by the continuing supply of salt from the feeder, which is mobilized by loading and buoyancy. The eventual cessation of the tongue advancement comes when the sedimentary cover reaches a critical thickness and/or the salt supply is depleted. In the event that the mother salt supply remains plentiful and loading continues, the salt moves vertically and the feeder will evolve into a salt dome.

AAPG Search and Discovery Article #91030©1988 AAPG Annual Convention, Houston, Texas, 20-23 March 1988.