Spatial and temporal trends in pre-caldera Jemez Mountains volcanic and fault activity Shari A. Kelley1, William C. McIntosh1, Fraser Goff 2, Kirt A. Kempter3, John A. Wolff 4, Richard Esser5, Suzanne Braschayko6, David Love1, and Jamie N. Gardner7 1New Mexico Bureau of Geology and Mineral Resources, New Mexico Institute of Mining and Technology, 801 Leroy Place, Socorro, New Mexico 87801, USA 2Earth and Environmental Science, New Mexico Institute of Mining and Technology, 801 Leroy Place, Socorro, New Mexico 87801, USA 32623 Via Caballero del Norte, Santa Fe, New Mexico 87505, USA 4School of the Environment, Washington State University, Pullman, Washington 99164, USA 5Energy and Geoscience Institute, University of Utah, Salt Lake City, Utah 84108, USA 6Noble Energy, Inc., 100 Glenborough Drive, Suite 100, Houston, Texas 77067, USA 714170 Hwy 4, Jemez Springs, New Mexico 87025, USA ABSTRACT 7.8 Ma rhyolitic volcanism that occurred rift preceded caldera formation. The volcanic in the central part of the JMVF between fi eld has been the subject of intense geologic New 40Ar/39Ar dates from the Jemez Moun- 12–8 Ma Canovas Canyon Rhyolite and study, as well as geothermal and mineral explo- tain volcanic fi eld (JMVF) reveal formerly 7–6 Ma peak Bearhead Rhyolite volcanism. ration, for several decades. Recently, the JMVF unrecognized shifts in the loci of pre-caldera Younger Bearhead Rhyolite intrusions (7.1– was mapped at a 1:24,000 scale between 1998 volcanic centers across the northern Jemez 6.5 Ma) are more widespread than previously and 2006 as part of the STATEMAP program Mountains; these shifts are interpreted to documented, extending into the northeastern to create updated versions of the classic Smith coincide with episodes of Rio Grande rift JMVF. Tschicoma Formation dacite erupted et al. (1970) geologic map of the area (e.g., Goff faulting. Early activity in the fi eld includes at 5 Ma in the Sierra de los Valles and then et al., 2011). During the course of this mapping, two eruptive pulses: 10.8–9.2 Ma basaltic erupted throughout the northeastern JMVF a number of previously unrecognized volcanic to dacitic volcanism on Lobato Mesa in the 5–2 Ma. The more refi ned geochronology of units and stratigraphic relationships were found. northeastern JMVF and 12–9 Ma mafi c to the JMVF indicates that pre-caldera volcanic A program of 40Ar/39Ar dating accompanied the silicic volcanism in the southwestern JMVF. centers were characterized by geographi- mapping effort. Sampling for geochronology While 9–7 Ma eruptions persisted in the cally and chemically distinct, relatively was primarily focused in the northern Jemez southern JMVF, a new eruptive center devel- short-lived, episodes of activity. Volcanism Mountains, a portion of the JMVF that has not oped on the La Grulla Plateau in the north- generally migrated eastward through time received as much attention as the eastern and western JMVF (8.7–7.2 Ma), corresponding in the southern JMVF, but the pattern in the southern sections. In this paper, we combine the with a period of rift widening caused by northern JMVF had a more complex east new 40Ar/39Ar dates on volcanic rocks with fi eld re acti va tion of Laramide faults in this area. (10–9 Ma) to west (9–7 Ma) to east (5–2 Ma) observations and some recently acquired geo- The older 8.7–7.8 Ma mafi c lavas emitted pattern that refl ects the timing of motion on chemical data to highlight important insights from Encino Point and the younger 7.7– faults. The new ages, coupled with detailed into the development of this much-studied vol- 7.2 Ma trachyandesite and dacite erupted on mapping of both volcanic rocks and the canic fi eld. the La Grulla Plateau are assigned to a new Santa Fe Group, document signifi cant pulses The general history of volcanism in the Jemez unit called the La Grulla Formation. The of faulting, erosion, and deposition during Mountains region is well established (e.g., Doell chemical composition of a 640 m stack of lava middle Miocene time and during late Mio- et al., 1968; Bailey et al., 1969; Smith et al., fl ows exposed in the northern margin of the cene time across the Cañones fault zone in 1970; Gardner et al., 1986). Basaltic eruptions Valles caldera changes from dacite to ande- the northern JMVF. began at ca. 25 Ma in the southeastern part of the site, then back to dacite upsection, becom- Jemez Mountains, with sporadic basaltic activ- ing slightly more alkalic upward. The shift INTRODUCTION ity continuing between 21 and 11 Ma (Wolde- to more alkalic compositions occurs across a Gabriel et al., 2006, 2007). Signifi cant eruptions sedimentary break, marking a subtle change The Jemez Mountains volcanic fi eld (JMVF) of basaltic and rhyolitic lavas and rhyolitic tuffs in magma source for the older Paliza Canyon in north-central New Mexico (Fig. 1) is the site in the southern mountains and basaltic to dacitic Formation and the younger La Grulla For- of the Valles caldera, the type example of a con- lavas in the northeastern mountains began at mation lavas. New age constraints from a tinental resurgent caldera (Smith and Bailey, ca.10 Ma (Bailey et al., 1969; Gardner et al., rhyolite intrusion in the southern JMVF and 1968). More than 20 million years of volcanic 1986). Intermediate to felsic composition erup- pumiceous rhyolite deposits in the northern and associated hydrothermal activity in the tions in the southern, central, northwestern, and JMVF suggest an episode of localized, 7.6– JMVF on the western margin of the Rio Grande northeastern parts of the fi eld continued after Geosphere; June 2013; v. 9; no. 3; p. 614–646; doi:10.1130/GES00897.1; 12 fi gures; 3 tables; 1 supplemental fi le. Received 1 January 2013 ♦ Revision received 5 March 2013 ♦ Accepted 11 March 2013 ♦ Published online 7 May 2013 614 For permission to copy, contact [email protected] © 2013 Geological Society of America Downloaded from http://pubs.geoscienceworld.org/gsa/geosphere/article-pdf/9/3/614/3345249/614.pdf by guest on 29 September 2021 Spatial and temporal trends in pre-caldera Jemez Mountains volcanic and fault activity 106°00′ 105°30′ Colorado 107°00 W′ N SJVF SAN LUIS 36°30′ LVF TusasTusas MountainsMountains JL Taos Plateau Taos New Mexico BASIN Rio Grande Rift COLORADO MAP AREA MOUNTAINS PLATEAU ne ZoneZzoneo ult FaultFfaulta do bu EmbudoEm ESPAÑOLA CRISTO Toledo Santa NACIMIENTO Clara f.z. 36°00′ MOUNTAINSembayment ′ = 36°00 ======== === == == = == = = Española = Valles = = = = zone = = JEMEZ = = = = = = = = = = = = = Caldera = = = DE = = = = = = fault = = = = = = Los Alamos = = = = = = = SIERRA Pajarito Santa Fe SANGRE SANTO DOMINGO BASIN BASIN . La Bajada fault zone Jemez f.z zone Cenozoic volcanic rocks Cenozoic sedimentary rocks ALBUQUERQUE fault Paleozoic to Mesozoic BASIN sedimentary rocks o Proterozoic rocks MOUNTAINS Albuquerque SCALE SANDIA Tijeras-Canoncit 02550 km 35°00′ 35°00′N ′ ′ 107°00 106°00′ 105°30 Figure 1. Regional location map of Jemez Mountains region and adjacent Rio Grande rift, New Mexico. SJVF—San Juan volcanic fi eld, LVF—Latir volcanic fi eld, JL—Jemez lineament. Geosphere, June 2013 615 Downloaded from http://pubs.geoscienceworld.org/gsa/geosphere/article-pdf/9/3/614/3345249/614.pdf by guest on 29 September 2021 Kelley et al. 10 Ma until caldera-forming eruptions occurred volcanic rocks in the JMVF to the Keres Group rift consists of a series of en-echelon basins; at 1.61 Ma (Izett and Obradovich, 1994) and and applying the name La Grulla Formation in the vicinity of the Jemez Mountains, the 1.25 Ma (Phillips et al., 2007) in the middle of to 7.3–8.7 Ma andesitic to dacitic centers in right-stepping transition between the northern the fi eld. Subsequent rhyolitic eruptions were the northwestern Jemez Mountains previously Albuquerque Basin and the Española Basin is concentrated within the Valles caldera, fi rst mapped as Lobato Basalt and Tschicoma For- accommodated by northeast-striking faults in on the resurgent dome and then along the ring mation by Smith et al. (1970). The Polvadera the Santo Domingo Basin along the southeast fracture zone (Gardner et al., 2010). The young- Group name is abandoned. margin of the volcanic field (Figs. 1 and 3; est unit in the JMVF is the ca. 37–45 ka Banco In addition to formulating a slightly revised Smith et al., 2001; Chamberlin, 2007; Cham- Bonito fl ow (Ogoh et al., 1993; Phillips et al., volcanic stratigraphy for the JMVF, the new berlin and McIntosh, 2007; Smith and Lynch, 1997), which was erupted along the southwest- dates, coupled with detailed mapping of both 2007). The right-stepping transition between the ern ring fracture of the caldera. the volcanic rocks and the underlying Santa Fe southern San Luis Basin and the Española Basin Bailey et al. (1969) and Smith et al. (1970), Group, are used to constrain the timing of move- is accommodated by the northeast-striking using K-Ar geochronologic data available at the ment of major Rio Grande rift faults crossing Embudo–Santa Clara fault system near the mid- time, divided the pre-caldera volcanic rocks into the volcanic fi eld. Although the link between dle of the fi eld (Fig. 1; Aldrich, 1986). two groups, the older Keres Group rocks located volcanic and fault activity in the JMVF has been Major rift-bounding normal fault systems mainly in the southern Jemez Mountains and the discussed previously, the earlier studies focused along the southern margin of the fi eld in the slightly younger Polvadera Group rocks of the only on the southern part of the fi eld (Gardner northern Albuquerque Basin and the Santo northern Jemez Mountains.