VENDEVILLE, BRUNO C.
Bureau of Economic Geology, The University of Texas at Austin, Austin, TX

Abstract: Salt Complexity Out Of Repeated Simplicity

Mature salt structures typically exhibit complex geometries that also vary rapidly along strike, a characteristic traditionally attributed to differences in rheology within the overburden sediment column. Instead, on the basis of theoretical considerations, analysis of natural examples, and physical experiments, we offer a simpler explanation for such complexity. We propose that the complexity of many mature salt structures results from superimposition of a few simple tectonic and depositional processes. Early thin-skinned extension can initiate salt ridges and diapirs by locally thinning the overburden. Likewise, regionally uneven sediment deposition causes differential loading and triggers salt movement. Salt ridges or diapirs then rise passively while adjacent depocenters, typically having circular planforms, subside. Passive diapirism stops and diapirs become dormant once most depocenters have grounded onto the subsalt basement. Subsequent episodes of regional tectonics (contractional or extensional) deform the preexisting network of "strong" depocenters and "weak" salt ridges and diapirs by jostling the depocenters along or against each other, and extending, contracting, or shearing the intervening salt ridges. Because the relative displacement between adjacent depocenters can vary along their individual perimeters, deformation of the salt ridges between them can vary from contraction, strike-slip or oblique slip, to extension along the periphery of a single depocenter. The resulting salt structures vary widely from pinched-off diapirs, vertical or oblique salt welds, fault welds, salt-cored boxfolds, thrusts, growth faults, fallen diapirs, and turtle structures.

AAPG Search and Discovery Article #90928©1999 AAPG Annual Convention, San Antonio, Texas