GEOLOGIC STUDIES IN CARLSBAD CAVERNS AND GUADALUPE MOUNTAINS
NATIONAL PARKS, NEW MEXICO AND TEXAS
S. J. Mazzullo
Department of Geology
Wichita State University
Wichita, Kansas 67260
Geologic studies in the Carlsbad Caverns and Guadalupe Mountains National Parks (New Mexico and Texas) areas during the last 15 years have focused on understanding the sedimentological origin of the Upper Permian (Guadalupian) Capitan reef and equivalent platform depositional systems (Yates and Tansill formations) through time, the paleoecology of platform environments as determined from paleontological studies of microfauna, and marine diagenesis of carbonate sediments. These studies have been done by integrated field mapping and compilation of regional lithostratigraphic data, and laboratory analyses of samples utilizing normal-light and cathodoluminescence petrography and stable oxygen-carbon isotope data.
Studies indicate that shelf deposition systems in the Yates and Tansill formations, specifically those on the outer-shelf proximal to the Capitan reef, were influenced to a great extent by sea level fluctuations through time. Platform carbonate facies deposited during sea level highstands are characterized by mosaics of shallow-marine sands, sponge-algal patch reefs, and low-lying islands. These deposits, as well as those of the adjoining Capitan reef, were pervasively cemented at these times by marine aragonite cements. In contrast, platforms were exposed subaerially during periods of sea level lowstand, at which time siliciclastic sediments (sands and silts) were deposited as thin but regionally extensive "sheets" across the platforms. Platform bypassing resulted in the deposition of some of the sands and silts into the adjoining Delaware Basin. Diagenetic processes operative during lowstands include lithification by meteoric calcite cements, and extensive karsting of exposed carbonate platforms. Alternating periods of sea level highstand and lowstand resulted in a complex facies stratigraphy of interbedded carbonate and siliciclastic sediments.