ABSTRACT

Considerable exploration attention has been devoted to salt-withdrawal minibasins and sub-salt traps in the offshore Gulf of Mexico (GOM) province. Investigation is inherently by geophysical and petrophysical means, utilizing sonar, seismic and gravity data, and scattered well logs, with obvious resolution limitations. Outcrop studies in Texas, Utah and Mexico provide an additional dimension, leading to an improved understanding of GOM examples.

Outcrops along I-10 between Kerrville and Sonora, Texas, provide a remarkable suite of evaporite-withdrawal (dissolution) structures, including varying exposure levels of withdrawal synclines, related secondary structures, and the primary weld surface. Paradox Basin exposures in Utah include diapirs and evaporite anticlines, revealing intense internal deformation, and various stratigraphic-structural interactions. The La Popa basin in Mexico hosts evaporite-cored anticlines, diapirs, withdrawal synclines, and a previously-recognized secondary weld.

These outcrop analogues provide excellent insight into GOM structures. For example, GOM welds form potentially important hydrocarbon pathways, but the coarse scale of seismic resolution, though revealing significant character changes, leaves many questions unanswered. The Edwards Plateau and La Popa welds exhibit remarkable diversity along their traces, even over relatively short distances. Some segments exhibit enhanced permeability through brecciation, fracturing, or sand-sand juxtaposition, whereas shale smearing or remnant salt limits fluid transmission along other portions.