Abstract

Philip B. King (1948) named the Goat Seep Limestone to resolve issues with previously assigned names (Chupadera Formation and Dog Canyon Limestone), and specified a type locality topographically above Goat Seep on the Western Escarpment of the southern Guadalupe Mountains, Texas. King mapped shelf-edge and shelf facies (the latter the Queen and upper Grayburg formations of modern usage) together as his concept of the Goat Seep Limestone. He based his interpretation of a reef origin for the shelf-edge portion of these rocks upon his examination of all known shelf-edge Goat Seep Limestone outcrops (Bush Mountain, Bartlett Peak, Pine Springs Canyon, North McKittrick Canyon, Patterson Hills, and the foothills of the southern Guadalupe Mountains), lithological similarities with the overlying Capitan Limestone reefs, and the depositional geometry exposed on the Western Escarpment.

Newell et al. (1953, p. 42-43) informally separated the shelf portion from the shelf-edge portion of King’s Goat Seep Limestone, stating “Because of confusion introduced by applying the name Goat Seep indiscriminatingly to shelf, reef, and forereef facies, it is proposed to restrict the name to the reef and forereef talus facies, a nomenclatural device that has served well with the Capitan formation.” King (1948, p. 85-86) used similar terminology for the overlying Capitan Limestone. Based upon their extensive studies of the Capitan Limestone and of living reef systems in the Pacific and western Atlantic oceans, Newell et al. (1953) concurred with King that the Goat Seep Limestone had been deposited in a reef setting.

Dunham (1969) cited a lack of binding organisms as compelling evidence that the Capitan Limestone was deposited as a marginal mound and not an organic reef system. Crawford (1981, p. 265) also disagreed with the reef paradigm of King (1948) and Newell et al. (1953) for the Goat Seep, stating that their results were based upon “... reconnaissance studies and general stratigraphic relationships.” He pointed out that ambiguity surrounds use of the term ‘reef’ in geology, and noted the Goat Seep Limestone failed to meet one of Lowenstam’s (1950) organic reef criteria, that of organic binding of sediments. Crawford (1981, p. 267) characterized the Goat Seep as a “... skeletal lean, submarine-cemented, carbonate mass formed along the high-relief shelf margin of the Delaware Basin ....” He Philip B. King (1948) named the Goat Seep Limestone to resolve issues with previously assigned names (Chupadera Formation and Dog Canyon Limestone), and specified a type locality topographically above Goat Seep on the Western Escarpment of the southern Guadalupe Mountains, Texas. King mapped shelf-edge and shelf facies (the latter the Queen and upper Grayburg formations of modern usage) together as his concept of the Goat Seep Limestone. He based his interpretation of a reef origin for the shelf-edge portion of these rocks upon his examination of all known shelf-edge Goat Seep Limestone outcrops (Bush Mountain, Bartlett Peak, Pine Springs Canyon, North McKittrick Canyon, Patterson Hills, and the foothills of the southern Guadalupe Mountains), lithological similarities with the overlying Capitan Limestone reefs, and the depositional geometry exposed on the Western Escarpment.

Newell et al. (1953, p. 42-43) informally separated the shelf portion from the shelf-edge portion of King’s Goat Seep Limestone, stating “Because of confusion introduced by applying the name Goat Seep indiscriminatingly to shelf, reef, and forereef facies, it is proposed to restrict the name to the reef and forereef talus facies, a nomenclatural device that has served well with the Capitan formation.” King (1948, p. 85-86) used similar terminology for the overlying Capitan Limestone. Based upon their extensive studies of the Capitan Limestone and of living reef systems in the Pacific and western Atlantic oceans, Newell et al. (1953) concurred with King that the Goat Seep Limestone had been deposited in a reef setting.

Dunham (1969) cited a lack of binding organisms as compelling evidence that the Capitan Limestone was deposited as a marginal mound and not an organic reef system. Crawford (1981, p. 265) also disagreed with the reef paradigm of King (1948) and Newell et al. (1953) for the Goat Seep, stating that their results were based upon “... reconnaissance studies and general stratigraphic relationships.” He pointed out that ambiguity surrounds use of the term ‘reef’ in geology, and noted the Goat Seep Limestone failed to meet one of Lowenstam’s (1950) organic reef criteria, that of organic binding of sediments. Crawford (1981, p. 267) characterized the Goat Seep as a “... skeletal lean, submarine-cemented, carbonate mass formed along the high-relief shelf margin of the Delaware Basin ....” He reported the shelf-edge and foreslope facies were bedded deposits, not organically bound, and that the depositional surface of the shelf-edge facies never built upward into the surf zone. Crawford (1981) further maintained the dominance of bedded deposits in shelf-edge and foreslope facies was evidence of a non-reef origin for the Goat Seep.

To address these discrepancies about the depositional setting of the Goat Seep Limestone, we undertook fieldwork in Pine Springs Canyon on the flanks of Bush Mountain and Bartlett Peak in 2004 and 2005. In 2004, we identified a preponderance of lithological types (framestones, bafflestones, bindstones) comparable to those of recognized reefs in the Lower, Middle, and Upper Capitan Limestone of west Texas and New Mexico. We also found many of the same taxonomic framework elements (Gigantospongia, Guadalupia, Archaeolithoporella) that are well known from Upper Capitan reefs. In 2005, we mapped ~600 field stations in Goat Seep outcrops in Pine Springs Canyon using GPS units to record positions, lithologies, paleontological content, and paleoecological data. We concentrated on lithological types (wackestone, rudstone, bindstone, etc.) to avoid biasing the data set with secondary interpretations of facies.

Our data support the interpretations of King (1948) and Newell et al. (1953) that the Goat Seep Limestone, as redefined by Newell et al., was deposited as a true organic reef. We agree with Newell et al. (1953, Figure 6, p. 15) that the formation includes reef and forereef talus facies. We reject Crawford’s (1981) conclusion that the Goat Seep was deposited as a fossil poor, submarine-cemented carbonate mound because our data reveal a preponderance of organic fabrics in the reef (shelf-edge) facies. We found evidence of bedding only in shelf (Queen Formation) and Goat Seep forereef facies, not in reef (shelf-edge) rocks. The latter are typified by constructional fabrics such as organic bindstones and skeletal framestones and bafflestones, and by secondary elements such as crypts, pendant epibionts, microbial micrite, isopachous cements, and late-stage blocky spar. In addition, we submit that all reef systems are dominated by bedded forereef talus deposits. Crawford’s (1981) arguments for a non-reef origin for the Goat Seep Limestone (minor organic binding, bedded deposits in shelf-edge facies, and dominance of foreslope sediments) are not valid.