Variations in depositional fabrics of the Middle and Upper Capitan Limestone reef (Permian; Guadalupian), west Texas and New Mexico, United States of America

The mode of origin of the Capitan Limestone reef remains the subject of debate even though numerous studies designed to answer this question were conducted over the past century. In part this is due to the inherent paleontological and lithological variability within the outcrops of the Capitan Limestone. Some of this is objective variability that is well expressed in the fabrics of these rocks; this variability can be examined and understood. Examples of objective variability include changes over time in (1) the depth of the depositional surface, (2) the level of energy in the depositional environmental, (3) the composition of the underlying paleontological community, and (4) the lithological fabrics constructed by those communities. An additional complication is present due to the perception of variability that cannot be substantiated by further detailed study. Examples of such pseudo-variability are seen in publications indicating that (1) one particular lithological fabric was volumetrically dominant over all other fabrics and (2) certain lithological fabrics were absent from these outcrops even though previous studies documented the presence of these fabrics.; The three projects of this dissertation were chosen to address issues concerning the paleontological and lithological composition of the reef. A quantitative study, based on random-sampling guidelines, was conducted to estimate the variability of the paleontological community of the Upper Capitan Limestone, Eddy County, New Mexico. Results indicated less variability than reported in the literature and confirmed that depth- and energy-zoned, shore-parallel facies of the Upper Capitan reef were continuous along depositional strike. The second study was designed to identify and map lithological fabrics exposed along portions of the Permian Reef Geology Trail, McKittrick Canyon, Guadalupe Mountains National Park, Texas. In addition to identifying several new fabrics from the Middle Capitan Limestone, the mapping demonstrated that previous estimates of fabric dominance were heavily biased toward one fabric. The final study described a new lithological fabric from the Middle Capitan Limestone in Bear Canyon, Guadalupe Mountains National Park, Texas. This sponge-framework crypt fabric was significantly different from other sponge crypts and represented the oldest-recorded occurrence of Gigantospongia discoforma.