Paleostratigraphic Biofacies and Lithofacies of the Owl Mountain Province, Fort Hood Military Installation, Bell and Coryell Counties, Texas

Abstract

The Owl Mountain Province is located in the eastern section of the Fort Hood Military Installation in Bell and Coryell counties within the Lampasas Cut Plain of Central Texas. This karst landscape is characterized by Cretaceous-age limestone plateaus and canyons with rock outcrops, cliffs, sinkholes, caves, springs, and rock shelters. The plateaus are capped by thick sequences of Lower Cretaceous limestone and dolostone known traditionally and informally as the “Edwards.” Although previous studies have concentrated on the southern portion of the Edwards Group and corresponding lithologies; current research is focusing on the far northern extent, beyond the previously defined Edwards system. Outliers in the northern and western extent, separated from the main reef trend, have been described as isolated mounds or shoals that developed on the Comanche Shelf near the Belton High and restricted circulation between the North Texas–Tyler Basin and the evaporitic material deposited in the Kirschberg Lagoon.

One such outlier, the Owl Mountain Province, is approximately 90 km² and is bounded by Owl Creek to the north, Lake Belton to the east, Cowhouse Creek to the south, and the military live fire impact zone to the west. Geologic formations in the study area are associated with the Moffatt Mound reef complex to the northwest and were deposited as carbonate mounds, isolated from the main Edwards reef trend.

Strata in the study area reflect a complex depositional environment consistent with restricted shallow shoals adjacent to or on the flanks of developing carbonate mounds. The delineation of heterogeneous carbonate strata, including detailed mapping and petrographic analyses, will help determine the depositional and diagenetic history of the Edwards Group, unique biozones, and the geomorphic evolution of the Owl Mountain Province. Detailed lithofacies analyses will enable the correlation of karst development to local stratigraphy by delineating zones that support the development of lateral and vertical fluid migration paths and conduit development.

AAPG Datapages/Search and Discovery Article #90219 © 2015 GCAGS, Houston, Texas, September 20-22, 2015