SPELEOGENESIS OF ORDOVICIAN CARBONATES PROXIMAL TO THE COLORADO RIVER NEAR COLORADO BEND STATE PARK, CENTRAL TEXAS

Ordovician Ellenburger carbonates exhibiting complex karst development outcrop in San Saba and Lampasas Counties, Texas, near the highly incised Colorado River. Caves in the region commonly contain morphologic features such as risers, half-tubes, ceiling channels and cupolas, which are associated with dissolution by ascending waters (hypogene processes) rather than meteoric water (epigene processes), indicating dissolution within confined or semi-confined conditions. Surficial breaching of voids has resulted in epigenic overprinting of hypogene features in these cave systems, often making it difficult to ascertain the dominant speleogenetic process in void development.

Additional karst features within the study area include numerous springs and abundant calcite spar deposits. Calcite spar is found filling solutional voids indicating an early phase of karst development that predates most of the caves found within the region. Springs show temporal and spatial variability indicating a complex hydrologic regime currently active within the region. Fluid analyses and thermal monitoring of springs indicate that most springs are associated with shallow meteoric fluid circulation; however, some springs exhibit characteristics indicative of deep circulation with little or no mixing with the immediately adjacent meteoric environment. Current studies are focused on determining the complex speleogenetic evolution of karst development within the Ellenburger Formation in this study area which will account for the multiple phases of karsting observed.