New Mexico Geological Society Annual Spring Meeting — Abstracts

A new 1:12,000 geologic map of Redondo Peak quadrangle (RPQ) has been completed for the New Mexico State Map Program. RPQ overlies the southern boundary between the Valles caldera (ca. 1.25Ma) and precaldera volcanic rocks of the Jemez Mountains. Three geologic domains make up the quadrangle: the southern resurgent dome, the southern moat, and the southern caldera margin. The resurgent dome consists of upper Bandelier Tuff, earliest post-caldera eruptives and interbedded debris flows, fluvial deposits and lacustrine rocks. Uplift is at least 1000 m and the resurgent dome is broken into a multitude of fault blocks. The southern moat consists of latest post-caldera rhyolite domes, flows, and tuffs interbedded with fluvial and minor lacustrine deposits. Very little faulting is observed in the southern moat. The southern caldera margin consists of mafic to silicic domes and flows (Keres Group, 6 to 13 Ma), partially covered with lower Bandelier Tuff (1.62 Ma) and extensively manteled with fall deposits of El Cajete Pumice (50 to 60 Ma). This zone is broken into a series of north-trending fault blocks (Canada de Cochiti fault zone) are primarily down to the east toward the Rio Grande rift. The western fault blocks are underlain by the Santa Fe Group (roughly 10 to 17 Ma) and by the upper Abiquiu Formation (21 Ma). The eastern fault blocks display extensive hydrothermal alteration (quartz-calcite-smectite ± illite ± chlorite ± zeolite ± pyrite ± epidote) mostly caused by intrusive activity related to the Bearhead Rhyolite (6 to 7 Ma).