Fracture-controlled ground-water distribution adjacent to Los Esteros Reservoir, Guadalupe County, New Meixco

The Triassic Santa Rosa Sandstone occurs at shallow depths over much of northeastern New Mexico. Approximately 11 km north of Santa Rosa, New Mexico, bitumen-impregnated Santa Rosa Sandstone is visible at the surface. These outcrops of bitumen-impregnated sandstone are known as the Santa Rosa tar sands. They were mined in the 1930’s for an asphalt-like road material, but are not currently produced. In 1982 and 1983, an evaluation of the bitumen reserves was undertaken for SOLV-EX Corporation, on its Riley Ranch lease adjacent to Los Esteros Reservoir, an irrigation and flood-control reservoir (Fig. 1). As part of the resource-evaluation program, 18 exploratory core-holes were cased and used for geohydrologic evaluation of the lease. Data collected indicate that structure features modified by solution/collapse processes in the Santa Rosa region strongly influence ground-water distribution and occurrence.