Subsurface structure of Valles Caldera; a resurgent cauldron in northern New Mexico. [Abstract only]
Valles Caldera is a 1.1 My old silicic cauldron lying at the intersection of the Rio Grande rift and northeast-trending Jemez Lineament. Geothermal exploration in the caldera region during the last 10 years provides subsurface data which refine our knowledge of deep caldera structure, but raise some questions concerning current models of resurgent cauldrons. For example, a detailed gravity investigation using 730 stations (Segar, 1974) shows a circular negative gravity anomaly centered over the caldera (as expected) but also indicates a strong northeast-trending grain of fault blocks in pre-caldera rocks, that are generally down-faulted to the southeast toward the Rift. Gravity data do not define a diapir structure beneath the resurgent dome attributable to tumescent magma; instead of a northeast-trending horst underlies the Redondo Peak segment of the dome. Interpretation of stratigraphy from many geothermal wells suggests that the caldera and resurgent dome are floored by untilted fault blocks (Hulen and Nielson, 1982). In addition, drilling to Precambrian basement and depths of 3.2 km has not encountered a large intrusive rhyolite that might logically produce tumescence of the dome. The new data indicate that the subsurface structural configuration of Valles Caldera is controlled by pre-caldera tectonics and that a more complicated mechanism is required to explain the resurgent dome standing high inside the caldera. A refined mechanism of resurgence might be one result of CSDP drilling at Valles Caldera.
- Research Organization:
- Los Alamos National Lab., NM
- OSTI ID:
- 6020332
- Journal Information:
- Geol. Soc. Am., Abstr. Programs; (United States), Vol. 15:5
- Country of Publication:
- United States
- Language:
- English
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