David W. Mercer¹, Katherine A. Giles²
(1) New Mexico State University Geological Sciences, Las Cruces, NM
(2) New Mexico State University, Las Cruces, NM

Abstract: The influence of passive salt diapiric rise on Upper Cretaceous to Lower Paleogene carbonate deposition, Potrerillos Fm., La Popa basin, Nuevo Leon, Mexico

Syndepositional near-surface salt diapiric rise strongly influenced depositional patterns within La Popa basin of northeastern Mexico. Basin stratigraphy is dominated by shallow marine siliciclastic deposits, which are interbedded with lenticular reefal carbonates adjacent to salt diapirs. At El Gordo diapir, four carbonate horizons (lentils) are exposed within mudstone units of the Potrerillos Fm.

Evidence for syndepositional salt rise within the Potrerillos Fm. include: 1) siliciclastic strata that onlap and thin (from 1500m to 400m) toward El Gordo diapir, 2) presence of progressive unconformities, 3) presence of isolated lenticular carbonates adjacent to the diapir, and 4) presence of diapir-derived metaigneous clasts found in debris flow deposits within carbonate lentils. Carbonate lentils are thickest (80m) near the diapir and thin rapidly away from the diapir to where they merge with encasing mudstone. The lentils are upturned and highly fractured proximal to the diapir and the amount of fracturing appears to decrease in younger lentils. The fractures are multiphase and contain early marine cement and sediment infills indicating fracture formation directly following carbonate lentil deposition. Fracturing is related to salt tectonism and deformation of rapidly cemented competent carbonate beds.

Carbonate reefal facies are underlain by carbonate clast debris flows. These debris flows were generated by near-surface diapiric rise that caused instability and failure of the slope.

AAPG Search and Discovery Article #90914©2000 AAPG Annual Convention, New Orleans, Louisiana