IS THE PERMIAN (GUADALUPAIN) REEF COMPLEX OF THE DELAWARE BASIN, SOUTHEASTERN NEW MEXICO AND WEST TEXAS, A WELL UNDERSTOOD GEOLOGICAL PROVINCE?

Various aspects of the Permian Reef Complex have undergone extensive geological study since the Capitan was first presented as a fossilized reef in 1929. Geological studies of these aspects of the Permian Reef Complex continue today, principally driven by economic interests involving the extraction of liquid and gaseous hydrocarbons from rocks of the basin and shelf. The history of geological studies in the Delaware Basin exhibits periodic swings between academic and economic interests.

Studies of the Goat Seep and Capitan Limestone have been driven chiefly by academic interests because these rocks are unproductive with respect to hydrocarbons. Prior to the 1960s, Delaware Basin workers concluded that the Goat Seep and Capitan Limestone had been deposited in reef settings, and recognized the dual facies of reef core and forereef rubble zones. A majority of workers between the late 1960s and the middle 1980s reached different conclusions, and the depositional setting of these two formations was called into question. Most studies after 1985 again concluded the Capitan Limestone was deposited in a reef setting.

Several important points must be taken into consideration when reading Permian Reef Complex literature. Relatively few of studies discussing the depositional environment of the Capitan Limestone were conducted by scientists who were principally paleontologists or paleoecologists. Most of the studies refuting deposition in a reef setting were conducted by sedimentologists or carbonate petrologists. Many of the papers concerning the Capitan Limestone reef are based upon revisitation and reinterpretation of the same set of outcrops in Eddy County, New Mexico and Guadalupe Mountains National Park, Texas. Most of these outcrops are in the late Capitan reef and broad-brushed extrapolations in the literature result in a strongly biased perception of the nature of the older reef tracts. There are very large areas of significant outcrop in the Southern Guadalupe Mountains that have not been incorporated into the literature. Our incursions into these areas provide evidence that older reef fabrics are significantly different from latest Capitan fabrics. We submit that what remains to be discovered about these two reef systems vastly outweighs that which has already been discovered.