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Gravity survey in the San Luis Valley area, Colorado

January 1, 1994

During the summers of 1963 and 1964, a regional gravity survey covering 6,000 square miles of the San Luis Valley and surrounding areas was made to determine subsurface basement configurations and to guide future crustal studies. The San Luis Valley, a large intermontane basin, is a segment of the Rio Grande trough, a reef system characterized by volcanism, normal faulting, and tilted fault blocks.

The gravity data, accurate to about 0.5 mgal, were reduced to complete-Bouguer anomaly values. The Bouguer-anomaly gravity map delineates a series of en-echelon gravity highs in the central and western San Luis Valley. These gravity highs are interpreted as horsts of Precambrian rock buried by basin fill. A series of en-echelon gravity lows along the eastern edge of the Valley is interpreted as a graben filled with sedimentary and igneous rock estimated to be up to 30,000 ft thick. The relatively high regional gravity over the Sangre de Cristo Mountains suggests that these mountains are locally uncompensated. A subcircular gravity low in the Bonanza area is interpreted as an indication of low-density volcanic rocks within a caldera structure.

Citation Information

Publication Year 1965
Title Gravity survey in the San Luis Valley area, Colorado
DOI 10.3133/ofr6646
Authors J. Robert Gaca, Daniel E. Karig
Publication Type Report
Publication Subtype USGS Numbered Series
Series Title Open-File Report
Series Number 66-46
Index ID ofr6646
Record Source USGS Publications Warehouse
USGS Organization