Abstract: Evolution of Capitan Massive Limestone (Permian) of Guadalupe Mountains, New Mexico and West Texas

Donald A. Yurewicz

Sedimentologic, paleoecologic, and diagenetic analyses of the lower and middle Capitan massive limestone (equivalent to the Seven Rivers and Yates Formations) show that its biota, lithotypes, and inferred environment of deposition differ markedly from that of the upper Capitan massive limestone (equivalent to the Tansill Formation).

Although the lower and middle Capitan "massive" consists predominantly of silt- and sand-size skeletal packstones, it apparently formed a potentially wave-resistant structure. It was made rigid by organic boundstones and submarine cements. It formed in a relatively deep (30 to 200 m), low-turbulence, normal-marine environment. Calcareous algae, boundstones, and submarine cements are more abundant in the upper Capitan which formed in a shallower, more turbulent environment.

Organic boundstones in the lower and middle Capitan "massive" consist predominantly of Archaeolithoporella encrustations, nodules formed by alternating laminae of Archaeolithoporella and submarine cements, and Tubiphytes. Boundstones, and the cavities they permit, form 10 to 20% of the lower Capitan "massive" and 20 to 60% of the middle Capitan "massive."

Primary cavities in the lower and middle Capitan "massive" have been partly filled by two forms of submarine cement--isopachous-fibrous and radial-fibrous. Isopachous-fibrous cement also is the dominant interparticle cement. Interparticle isopachous-fibrous cement also may be of submarine origin. The predominance of suspension-feeding organisms and the absence of burrowing types are consistent with early lithification of the seafloor.

Fossil preservation suggests a relatively low-turbulence environment. Fossil zonation and geometric relations of adjacent shelf deposits suggest a moderately deep-water environment for the lower and middle Capitan "massive."

AAPG Search and Discovery Article #90968©1977 AAPG-SEPM Annual Convention and Exhibition, Washington, DC