Mechanics of Salt Tongue Formation with Examples from Louisiana Slope

Peter D'Onfro

Salt tongues up to several thousand feet thick and a few tens of miles long appear to intrude sediments along the Sigsbee Scarp and in the Mississippi fan in the Gulf of Mexico. Because salt tongues are impermeable and cover large areas of sediment, they have the potential to trap tremendous volumes of hydrocarbons.

Field observations, laboratory experiments, and in-situ measurements in salt mines indicate that salt behaves like a viscous fluid over geologic time. Consequently, the same mechanical principles used to analyze igneous dike and sill formation can be applied to salt intrusions. Evidence suggests that salt tongues, like igneous sills, intrude sedimentary strata in which both horizontal principal compressive stresses exceed the overburden stress. This stress state exists in areas of regional tectonic or localized horizontal compression (e.g., in active thrust and foldbelts, in the toe regions of active growth fault systems, and around the flanks of intruding diapirs). This model puts constraints on both the timing of emplacement and the location of salt tongues.

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