THE GEOLOGIC FRAMEWORK AND HYDROSTRATIGRAPHY OF GUADALUPE RIVER STATE PARK AND HONEY CREEK NATURAL AREA, KENDALL AND COMAL COUNTIES, TEXAS

This report describes the geologic map and hydrostratigraphy of the Hammett Shale, Hensel Sand, Cow Creek Limestone, and the lower member of the Glen Rose Limestone that outcrops in Guadalupe River State Park and Honey Creek Natural Area, Kendall and Comal Counties, Texas. The Trinity Group hydrostratigraphic units have been mapped and described based on porosity types. The naming of these hydrostratigraphic units is based on topographic or historical features that occur in outcrop. The Doeppenschmidt informal hydrostratigraphic member is stratigraphically the highest hydrostratigraphic interval in the study area. The Doeppenschmidt member contains interparticle, moldic, burrowed, bedding plane, fracture and cave porosity. The underlying Turkey sink informal hydrostratigraphic member has interparticle, fracture and cave porosity. This unit appears to be an aquitard with springs/seep issuing near the contact with the overlying Doeppenschmidt informal member. The Honey creek informal hydrostratigraphic member contains interparticle, moldic, burrowed, bedding plane, fracture, channel, and cave porosity. The Honey creek informal member is an aquifer in the subsurface and contains well developed porosity and permeability. The Baxter informal hydrostratigraphic member contains primarily interparticle porosity, but also exhibits some moldic and cave porosity in its upper parts. Within the vicinity of the outcrop, the unit likely acts as a groundwater storage unit because of its lithology. The Guadalupe river informal hydrostratigraphic member contains interparticle, moldic, vug, burrowed, fracture, bedding plane, and channel and cave porosity. The Guadalupe River informal hydrostratigraphic member is an aquifer-bearing unit in the subsurface and is the primary target for water well drilling in the area. The Curry creek informal hydrostratigraphic member is not exposed in the study area, but is thought to underlie parts of the Guadalupe river hydrostratigraphic unit based on mapping of the overlying units and comparisons with subsurface thicknesses. The Curry creek informal hydrostratigraphic member restricts the downward migration of groundwater, resulting in springs that discharge at the base of the Guadalupe river unit.