Lineaments interpreted from Landsat images mark the location and trend of basement faults observed on seismic lines in the eastern Denver basin.

Linear features mapped as tone and texture patterns on multispectral scanner images in northeastern Colorado and southwestern Nebraska are used to interpret regional lineaments. Individual linear features up to 25 mi (40 km) long and visible on both bands 5 and 7 define a grid of regional lineaments trending northeast and northwest. Comparisons of lineaments with aeromagnetic and gravity maps and with interpretations of basement geology suggest that lineaments are the boundaries of basement blocks with areas of about 1,000 mi² (2,590 km²). Constituent linear features within the lineament zone probably mark boundaries of smaller blocks of about 50 mi² (130 km²).

Seismic lines in northeastern Sedgwick County in extreme northeastern Colorado cross linear features that are components of a broad regional lineament that trends northeast and parallels the South Platte River. Seismic data consist of a grid of about 100 mi (160 km) of multifold Vibroseis lines. Basement faults, generally with offsets of less than 100 ft (30 m), are observed in seismic lines that cross some individual linear features. Monoclines and faults are present in Pennsylvanian to Tertiary strata that overlie basement. A time-structure map on the Precambrian and an isochron map of Wolfcamp (Lower Permian) to Precambrian show that the lineament is a 7-mi (11-km) wide zone of small, downdropped basement blocks. Thickening of Permian-Pennsylvanian strata on the down-thrown side of faults suggests tectonic activity. Further tectonic activity is indicated by listric faulting in the Cretaceous Niobrara Formation.

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