Halokinetic Sequence Types and Controls within La Popa Salt Basin, Northeast Mexico

Katherine A. Giles¹, Timothy F. Lawton¹, and Mark G. Rowan²
(1) Institute of Tectonic Studies, New Mexico State University, Las Cruces, NM
(2) Rowan Structural Consulting, Inc, Boulder, CO

Halokinetic sequences are angular unconformity bounded, growth-stratal packages that form due to temporal variations in topographic relief over passively rising diapirs. Two end-member types of halokinetic sequences (Type A and Type B) have been recognized in the shelfal strata of La Popa salt basin. The types differ in depositional facies, maximum degree of internal folding, amount of fault reactivation on unconformities, overall sedimentation rate, and distance of halokinetic sequence termination from the salt/sediment interface.

Type A sequences are associated with periods of very low sediment accumulation rates during marine transgression. They contain basal debris flows encased in outer shelf black shales that shallow upward to middle shoreface sandstone. These strata are locally tightly folded with truncation angles of up to 90 degrees at sequence boundaries. Sequence boundaries show significant fault reactivation during later halokinesis and evidence of brittle shear. Type A sequences terminate directly against the diapir.

Type B sequences are associated with periods of moderately high sediment accumulation rates during marine regression. They contain a basal, lower shoreface that shallows upward to tidal and lagoonal sandstone facies. These strata display minimal folding with truncation angles that are much less 30 degrees. There is little or no reactivation of the sequence boundaries during later halokinesis. Type B diapir-proximal sequence terminations are spatially separated from the diapir by an average of 250m.

Stacks of Type A overlain by Type B sequences formcomposite sequences bounded by angular unconformities that record the interplay of shelf depositional systems and halokinesis in La Popa basin. The characteristics of the two types of sequences and their stratal arrangement into composite sequences have important implications for reservoir quality, geometry, continuity, and charge potential.

AAPG Search and Discovery Article #90039©2005 AAPG Calgary, Alberta, June 16-19, 2005