Abstract
Optical analysis of Landsat imagery is a valuable preliminary step for exploration in areas where a detailed geologic base is lacking, logistics are difficult, or the political situation is insecure. Two maps of Iraq produced by such analysis elucidate structural and lithologic relations across a broad oil-producing region. The Landsat map of Iraq is divided into units based on drainage patterns, surface textures, relative resistance to erosion, and color. These units tentatively correlate to the broadly generalized geologic map of Iraq. The Landsat map clearly delineates Iraq’s 3 major geotectonic zones: (1) desert and alluvial plains, (2) simply folded, and (3) overthrust. The lineament and anomaly map, derived from optically enhanced imagery, shows noncultural lineaments and 5 types of anomalies: (1) linear, (2) circular, (3) structural, (4) textural, and (5) shade. Conjugate shear sets form lineaments oblique to the regional and local compression directions. Lineaments also reflect normal faults, tear faults, thrust fronts, structural control of wadis, and wind-direction features. The intersection of 3 or more lineaments defines a linear anomaly. Circular anomalies can be attributed to structural domes or basins, dia-pirs, calderas, or astroblemes. Appreciable deviations from local defor-mational style are considered structural anomalies. Textural anomalies are abrupt changes in texture unrelated to lithologic changes. Shade anomalies, mapped from band 5 enhancements, reflect a shade change from light to dark, usually across a lineament. Comparison of oil field locations to Landsat-mapped units, lineaments, and anomalies can indicate exploration targets for more detailed ground-based geologic and seismic investigation.
