Differential compaction and basinward tilting of the prograding capitan reef complex, Permian, west Texas and southeast New Mexico, USA

Abstract

The Capitan Limestone (Permian) of southeast New Mexico and west Texas, U.S.A., contains a classic shelf-margin carbonate system which progrades into the Delaware basin. Geopetal structures were studied in Capitan reefal cavities in the Guadalupe Mountains to determine the effect of postdepositional tilting on stratal geometries at and near the shelf margin. Geopetal structures in the reefal part of the middle Capitan have basinward dips (average dip angle = 10° to the southeast, n = 28) which indicate that the Capitan reef was tilted basinward by approximately 10° after deposition. Backreef strata immediately above and lagoonward of the Capitan reef have basinward dips of approximately 8–9° to the southeast, similar to geopetal surfaces in the Capitan. However, backreef strata 100–150 m above the Capitan reef are nearly horizontal. Differential compaction of slope and basinal carbonate muds apparently tilted Capitan reef and lowest backreef beds shortly after deposition when dense lithified reef and shelfal carbonates prograded over highly compactable slope and basinal sediments. Differential compaction and down-to-the-basin tilting has probably increased the slope angle of many other prograding carbonate systems shortly after deposition.