The time between the tuffs: Deposits of the Cerro Toledo interval in Bandelier National Monument, New Mexico
Elaine P. Jacobs and Shari A. Kelley
The Cerro Toledo Rhyolite and associated tuffs and sediments are products of volcanic activity centered on a series of high-silica rhyolite domes located along the eastern rim of the Valles caldera. These domes were active between 1.65 and 1.21 Ma during a 380 kyr interval (Spell et al., 1996) between the caldera-forming eruptions of the upper (Tshirege) and lower (Otowi) members of the Bandelier Tuff. Volcaniclastic sequences exposed in Bandelier National Monument (BNM) record a period of dynamic geomorphologic change coupled with continued eruptive activity. Rabbit Mountain and Paseo del Norte, located 10 -15 km west of exposures in BNM, are the most likely source areas for these sequences. Outcrops in BNM consist of braided stream and hyperconcentrated flow deposits, tephras, and a pyroclastic collapse deposit. Comparison of units exposed in BNM to those exposed to the north, in the vicinity of Los Alamos, illustrates the importance of provenance in determining the nature of Cerro Toledo volcaniclastic deposits. Thick sequences of Cerro Toledo deposits fill an east-trending post-Otowi paleodrainage; these deposits, in turn, are incised by an east-trending drainage system that formed just prior to eruption of the Tshirege Member of the Bandelier Tuff.
- Jacobs, Elaine P.; Kelley, Shari A., 2007, The time between the tuffs: Deposits of the Cerro Toledo interval in Bandelier National Monument, New Mexico, in: Geology of the Jemez Region II, Kues, Barry S.; Kelley, Shari A.; Lueth, Virgil W., New Mexico Geological Society, Guidebook, 58th Field Conference, pp. 308-315.