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Abstract: Thermal-Infrared Surveys for Uranium Exploration in South Texas

Terry W. Offield, Timothy E. Townsend

Day and night aerial thermal-infrared surveys were made of about 2,200 sq km in the Catahoula Tuff-Oakville Sandstone belt of the Texas coastal plain between Freer and Ray Point. The thermal images provide new and interesting geologic detail in an area of poor outcrops, extensive vegetation cover, and difficult land access. Where 1:24,000-scale geologic maps exist for control, a comparison with the thermal data shows that the night images clearly delineate conglomeratic channel-fill material of the Soledad Member within the generally clayey Catahoula Tuff. Most of the belt is covered only by 1:250,000-scale geologic maps, and the night images add useful detail to improve the delineation of the Oakville-Catahoula contact and to discriminate probable unmapped outliers of Oa ville upon the Catahoula as well as channel-fill deposits that may be of interest in uranium exploration.

The channel fills remain relatively warm at night, indicating higher thermal inertia than the enclosing clayey materials. The thermal inertia of the conglomeratic materials was increased and the contrast with surroundings was enhanced by near saturation of the porous channel fill during heavy rains a few days before the aerial survey. At some locations, both water-rich and silicified fault zones show as warm zones in the night images. Further analysis toward remote determination of differences in physical properties among the geologic materials is achieved by registration of day and night images to make a day-night temperature-difference map. Such a map permits inference as to conglomerate and sandstone proportions in the channel fills and perhaps subtle lithologic variations in the C tahoula. The thermal images provide information to interpret aeroradioactivity maps of the area, and the aeroradioactivity data in turn solve the problem of whether warm areas within the Catahoula are channel fills or Oakville Sandstone outliers. By delineating possible exploration targets such as fluvial channel fills and fault lines, the thermal images show their utility in uranium exploration in the coastal plain setting.

AAPG Search and Discovery Article #90969©1977 AAPG-SEPM Rocky Mountain Sections Meeting, Denver, Colorado