122 Stratigraphy

Monday, 10 October 2011
1:30 PM - 5:30 PM
Room 211CD

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

Paper number: 122-12
Program: Technical Sessions
Time: 4:15 PM – 4:30 PM

Authors

Abstract

This study involves the hydrostratigraphic mapping of the upper and middle Trinity aquifer exposed within the Guadalupe River State Park and Honey Creek State Natural Area of south-central Texas form part of the recharge zone to the upper and middle Trinity aquifers. Hydrostratigraphic mapping is the mapping of the geology and structure of an area based on groundwater transmitting capabilities and the resulting maps may or may not reflect the same boundaries as a traditional geologic map. This is because similar porosity and permeability characteristics may extend into adjoining rock strata, or alternatively, the boundaries of similar porosity and permeability characteristics may not be constant throughout a given strata, and therefore, may not extend to the geologic boundaries of that strata.

The methods involved with hydrostratigraphic mapping include field observation and measuring the outcrop and describing the geology, porosity types, and structural features. The outcrop mapping is supplemented with borehole (i.e., well) data and geophysical data from the area of outcrop to better understand the surface and subsurface boundaries of the rock strata’s porosity and permeability characteristics.

Mapping the geology, structure and hydrostratigraphy in the area of the two parks involves an effort is to verify if the hydrostratigraphic subdivisions of the middle Trinity aquifer identified from cores and geophysical logs in northern Bexar County, Texas are mappable in surface outcrops at an extended distance. If surface correlations can be identified the resulting hydrostratigraphic map will depict the geologic features that control the infiltration and movement of ground water, such as porosity and permeability; whether they exist naturally in the rock strata or they result from the external affects of changes in the geologic structure such as diagenesis, dissolution, fracturing and faulting.