Abstract

The Whiting W. A. Estes #153, located along the western edge of the Central Basin Platform, contains a sequence of late Leo-nardian carbonates identified as the late high-stand systems tract (HST) of L5, the transgressive systems tract (TST) and HST of L6, and the early TST of L7. The HST of L5 is dominantly aggradational and primarily consists of middle ramp burrowed peloidal dolopack-stones with varying amounts of mud and crinoid fragments. L5 becomes increasingly pro-gradational toward the high-frequency sequence (HFS) boundary, as shown by a gradual shift toward inner ramp facies and increasingly thin tidal flat-capped high-frequency cycles (HFC). Inner ramp facies consist of shallow subtidal coated grain-dasyclad-peloid dolopackstones, intertidal fenestral intraclast-pisoid grainstones, restricted dolomudstones, argillaceous claystones and bedded evaporites. The early TST of L6 is comprised of aggradational tidal flats with brief subtidal back-stepping events as sea-level rise and sedimentation rates compete to control accommodation space. Sea -level rise eventually outpaces sedimentation rates and a return to middle ramp burrowed peloidal dolopackstones is seen at the L6 maximum flooding surface (MFS). Following the MFS, the L6 HST is aggressively progradational, as demonstrated by a rapid return to intertidal conditions and increasingly thin HFC’s approaching the sequence boundary. Subaerial exposure at the L6 sequence boundary is considered significant in duration, as evidenced by the extensive micro-karst overprint throughout much of the L6 interval. The early TST of L7 is comprised of aggrading tidal flats with episodic shallow subtidal excursions sharply overlain by outer ramp skeletal packstones, wackestones and boundstones with a significantly more diverse faunal assemblage than that of L6. This abrupt facies contrast marks the onset of widespread flooding of the early San Andres platform.

Historically, the middle ramp facies of L5 represent the upper Clear Fork, while the peritidal inner ramp facies of L6 and early L7 represent the Glorieta, and the outer ramp facies of L7 represent the Holt limestone member of the lower San Andres. The use of this time-transgressive litho-stratigraphic nomenclature results in an inaccurate interpretation of platform development. Proper application of this modern sequence stratigraphic model provides a geologically sound depiction of time-equivalent depositional systems, subsequent flow units and overall reservoir architecture.