The youngest silicic eruptions from the Valles Caldera and volcanic hazard potential in north-central New Mexico

Abstract

New Mexico Geology May 2016, Volume 38, Number 2 Sporadic mafic and felsic eruptions, representing at least five major and several smaller pulses of effusive and explosive volcanic products that range in age from 25.5 Ma to 68.3 ka, crop out within the Jemez volcanic field and the surrounding areas in north-central New Mexico (Kelley et al., 2014 and references therein). The youngest pyroclastic and lava flows erupted from the southern moat of the Valles caldera. These volcanic products belong to the El Cajete Pyroclastic Beds and co-erupted Battleship Rock Ignimbrite, which are locally overlain by the Banco Bonito obsidian flow (Gardner et al, 2010). Based on detailed field mapping, Wolff et al. (2011) suggested that more than 10 km3 of silicic magma was erupted to form the fallout and ash-flow deposits of the lower and upper units of the El Cajete Pyroclastic Beds and the Battleship Rock Ignimbrite, whereas the volume of the Banco Bonito obsidian lava flow was estimated at 4 km3. The mostly Plinian eruptions of the El Cajete Pyroclastic Beds were distributed over much of the Valles caldera, the southern Jemez Mountains, and the Rio Grande rift, including considerable ash deposited in the Santa Fe area and in eastern New Mexico (Wolff et al., 2011). As shown in Figure 1, recent field studies identified >4 m thick of proximal and ≥1 m thick of distal primary pumice deposit near the vent (A) and in the Cerros Gallery of Geology