Landsat-Based Lineament Analysis, East Texas Basin and Sabine Uplift Area

Lineament analysis was used to study the relationship between subsurface structure and surficial features in East Texas, southeastern Oklahoma, southwestern Arkansas, and northwestern Louisiana-areas of low topographic relief, moderate vegetation cover, and diverse land use. More than 2,200 lineaments were mapped from four standard 1:250,000-scale Landsat Thematic Mapper images. Operator error and data-base variation were evaluated in areas of sidelap between adjacent images. Because no significant difference (at p = .05 level) in lineament orientations or mean lineament length was detected in these areas, mapping error and differences between images were judged inconsequential. Vector sums of greater-than-average values of length-weighted frequency (F) were used to define significant peaks of lineament orientation. Regional orientation for all lineaments is bimodal, peaks being 325° and 21° azimuth. The northwest regional peak coincides with mean azimuth of borehole elongations in 50 wells located throughout East Texas. Within the salt structure province of the East Texas Basin, the azimuth of the vector sum for lineaments (16°) is not significantly different from that for underlying, elongated salt-related structures (29°) (salt diapirs, salt pillows, turtle structures). These observations suggest that lineaments and subsurface structures result from like-oriented stresses. Lineament density (length/unit area) was measured in 100-km2 grid cells throughout the study area to delineate some large structural features. An arcuate trend of high values (220 km/100 km2) demarcates the Mexia-Talco Fault Zone. Other density highs occur near the Angelina Flexure and the South Arkansas and Elkhart-Mt. Enterprise Fault Zones. Lineament density values have no consistent spatial relationship with salt-related structures, but their relatively small size probably makes these structures difficult to detect. These results indicate that high lineament density coincides with most major surface and subsurface structures in the study area. Furthermore, statistically significant lineament orientations coincide with azirnuths of elongated boreholes and deeply buried structures and may be diagnostic of regional and basinwide stress regimes.