Geophysics of the Rio Grande Basins
San Luis Basin Geophysics
Preliminary Interpretation of High-Resolution Aeromagnetic Data Collected Near Taos, New Mexico
ABSTRACT.—High-resolution aeromagnetic data were recently collected in an area surrounding the Town of Taos to improve the regional geologic understanding of the subsurface. Qualitative and quantitative analyses of the data were integrated to obtain a preliminary interpretation. The primary sources of aeromagnetic anomalies are interpreted as Servilleta Basalt with dominantly reversed-polarity remanent magnetization, weakly to moderately magnetic Precambrian crystalline basement, and magnetic Tertiary intrusions. In the western part of the survey area, we interpret an area of shallow Servilleta Basalt cut by north-striking faults, which are related to the Los Cordovas faults. The area of shallow basalt is faulted down to the east on the eastern side, and is truncated by northeast-striking faults near the Rio Pueblo de Taos on the southern side. A basement structural bench under the Town of Taos, which appears to be bounded by some of the northeast-striking faults, likely continues into a structurally complex area underlying the Buffalo Pasture area, but the configuration is unclear. In the northeastern part of the survey area, we interpret rift-related and pre-rift faults that strike north and northwest, respectively. The north-striking faults align with the Rio Lucero, supporting the premise that the drainage is tectonically controlled. Faults of both orientations appear to bound basement structural benches that step down to the south and west. In the southern and east-central parts of the area, aeromagnetically inferred faults parallel major variations in orientation of the Embudo, Sangre de Cristo and Picuris-Pecos fault systems. The parallel faults occur within a 2- to 7-km-wide zone from the range front into the basin. We interpret high amplitude aeromagnetic anomalies along the northern and northeastern survey perimeters to represent Tertiary plutons, which are partially exposed and intrude Precambrian rocks in the north. Similar anomalies just north of Rio Pueblo de Taos are likely caused by a related Tertiary pluton that is buried beneath Paleozoic sedimentary rocks.
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