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Rocky Mountain (53rd) and South-Central (35th) Sections, GSA, Joint Annual Meeting (April 29–May 2, 2001)

Paper No. 0
Presentation Time: 8:45 AM

GEOLOGIC FRAMEWORK OF THE NORTHERN SANTO DOMINGO BASIN: STRUCTURAL OVERLAP OF THE LA BAJADA AND PAJARITO FAULT ZONES


SAWYER, David A., U.S. Geol Survey, MS 913, Box 25046, Denver, CO 80225-0046, GRAUCH, V.J.S., U.S. Geol Survey, MS 964, PO Box 25046, Denver, CO 80225-0046, MINOR, Scott A., U.S. Geol Survey, MS 913, PO Box 25046, Denver, CO 80225-0046, DETHIER, David P., Geosciences, Williams College, 947 Main St, Williamstown, MA 01267 and SMITH, Gary A., Department of Earth and Planetary Sciences, Univ of New Mexico, Northrop Hall, Albuquerque, NM 87131, dsawyer@usgs.gov

Recent detailed geologic mapping and aeromagnetic data in the vicinity of Cochiti Pueblo elucidate the structural relationship of the La Bajada and Pajarito fault zones in the northern Santo Domingo basin, Rio Grande rift, New Mexico. The La Bajada fault is the principal down-to-the west boundary structure along the NE margin of the Santo Domingo accommodation basin. To the NW, the down-to-east Pajarito fault zone forms the principal western boundary of the asymmetric Española basin. An eastern branch fault splays SE from the Pajarito fault zone near St. Peters Dome. This east Pajarito branch continues for 20 km to the SE where it lies adjacent to and parallels the northern 16 km of the La Bajada fault zone. At the surface these overlapping fault zones offset the Cerros del Rio basalts (2.7-2.2 Ma) and the upper Bandelier Tuff (1.22 Ma), but may represent only the latest displacements on these fault systems. The region of fault zone overlap is characterized by inward-arcing, oblique-slip, fault segments and splays that suggest coeval propagation and mechanical interaction of the Pajarito and La Bajada fault zones. Based on detailed aeromagnetic data, we interpret the east Pajarito fault zone to project at least 10 km south parallel to the northern La Bajada fault in the subsurface of Santo Domingo basin. This projected fault segment displaces Cerros del Rio basalts at shallow depth down to the east to form a narrow (3 km) graben adjoining the La Bajada escarpment. Recognition of the east Pajarito fault zone allows subdivision of the northern Santo Domingo basin into three Pliocene-Quaternary tectonic and stratigraphic domains: a western graben, between the main Pajarito fault zone exposed at Tent Rocks and the Cochiti fault; a central horst exhibiting shallow Cerros del Rio basalts between the Cochiti and east Pajarito faults; and the narrow eastern graben adjoining the La Bajada fault described above.

Session No. 16

S3. Geologic Framework of the Middle Rio Grande Basin
Wednesday, 2 May 2001: 8:10 AM-12:00 PM
Geological Society of America Abstracts with Programs. Vol. 33, No. 5, April 2001, p.48
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