Spatial and Temporal Trends in Pre-Caldera Jemez Mountains Volcanic and Fault Activity

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

106°00′ 105°30′ Colorado

107°00 W′ N SJVF SAN LUIS 36°30′ LVF TusasTusas MountainsMountains

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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 =

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= DE

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= Los Alamos

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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.

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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. Bailey et al. (1969) et al., 1986) or a small portion of the northern Domingo Basin project northward beneath the further subdivided the Polvadera Group in the fi eld (Baldridge et al., 1994). Here we present volcanic fi eld; from west to east, these systems northern JMVF into an older unit called Lobato the fi rst comprehensive analysis of the inter- are the Sierrita, Jemez, Cat Mesa, Jose, Cañada Basalt and younger units called the Tschicoma play between nearly continuous eruptions in the de Cochiti, Camada, and Pajarito (Fig. 3). The Formation and the El Rechuelos Rhyolite. JMVF during the past 10 Ma and faulting across close relationship between volcanism and Smith et al. (1970) mapped Lobato Basalt (later the entire JMVF. These data are used to docu- normal faulting in the fi eld has long been rec- changed to Lobato Formation by Goff et al., ment pulses of middle Miocene and late Mio- ognized (e.g., Gardner et al., 1986). Eruptive 1989), which is predominantly composed of cene faulting and sedimentation. We describe in centers generally are located at intersections of basalt fl ows, on Lobato Mesa, Clara Peak, and some detail the temporal and spatial distribution northeast-striking and north-striking fault sys- Cerro Roman to the east, on the La Grulla Pla- of pre-caldera volcanic centers through the his- tems or are aligned along fault strands (Gardner teau to the west, and on several mesas on the tory of the JMVF and discuss the connections et al., 1986; Lynch et al., 2004). Lava fl ows com- northern edge of the Jemez Mountains volcanic between the eruptive history and structural monly thicken adjacent to faults, demonstrat- fi eld (e.g., Escoba Mesa and Polvadera Mesa, evolution of the area. Generally, basins in the ing syneruptive displacement along these fault Fig. 2). Smith et al. (1970) mapped Tschi- Rio Grande rift have narrowed and deepened systems (Gardner et al., 1986; Kempter et al., coma Formation, which is composed mainly as rifting has progressed (Chapin and Cather, 2004). Fault activity has clearly migrated east- of coarsely porphyritic dacite to rhyodacite, in 1994), and such a pattern has been recognized ward through time in the southern Jemez Moun- the Sierra de los Valles east of the caldera, on in the southern JMVF (Gardner et al., 1986). tains. For example, the Cat Mesa fault zone in the La Grulla Plateau northwest of the caldera, However, the new dates record a late Miocene the southwestern Jemez Mountains (Fig. 3) off- and in the highlands in between (Fig. 2). The (7.3–8.7 Ma) episode of rift widening along sets Permian Yeso Formation down to the east El Rechuelos Rhyolite includes a young group reactivated Laramide faults in the northwest- ~240 m; but ca. 9 Ma Keres Group andesite is of domes (ca. 2 Ma, Bailey et al., 1969) in the ern Jemez Mountains. During this time frame, offset <10 m, and 1.25 Ma Tshirege Member northeastern part of the fi eld and an older set of a break in activity prior to 7.6 Ma and a subtle of the Bandelier Tuff is displaced <2 m (Kelley domes (5.6–7.0 Ma; Gardner et al., 1986; Loef- shift to more alkalic compositions are recorded et al., 2003, 2007b). Thus, the Cat Mesa fault fl er et al., 1988) in the headwaters of Cañoncito in the major-element geochemistry of 640 m of zone is primarily an early rift fault. In contrast, Seco (Fig. 2). andesitic to dacitic lava exposed in the northern the Pajarito fault zone in the southeastern Jemez We use the new 40Ar/39Ar dates presented wall of the Valles caldera. Mountains (Fig. 3) displaces Keres Group rocks here, as well as other recently published by as much as 300 m (Goff et al., 1990) and 40Ar/39Ar dates (McIntosh and Quade, 1995; STRUCTURAL SETTING 1.25 Ma Bandelier Tuff by 90 m (Lynch et al., Smith, 2001; Justet, 2003; WoldeGabriel et al., 2004). The Pajarito fault zone in the south- 2006, 2007; Broxton et al., 2007), to demon- The JMVF straddles the boundary between eastern Jemez Mountains also cuts middle strate that the age distinction between the the mildly deformed Colorado Plateau and the Pleistocene terrace gravel (Lynch et al., 2004). Polvadera Group in the northern Jemez Moun- basement-cored Laramide uplift of the Sierra Displacement of the Bandelier Tuff along the tains and Keres Group in the southern Jemez Nacimiento to the west and the Neogene Rio Pajarito fault is ~200 m near Los Alamos , where Mountains is blurred (Gardner et al., 1986). Grande rift to the east (Fig. 1). The volcanic Holocene displacements associated with three The new data have been instrumental in iden- fi eld is part of a northeast-striking alignment inferred M7 earthquakes have been documented tifying previously unrecognized temporal erup- of <10 Ma volcanic centers that extends from (Lewis et al., 2009). tion patterns across the JMVF, particularly in east-central Arizona to southeastern Colorado, Signifi cant rift-bounding structures along the northern Jemez Mountains (Kelley et al., referred to as the Jemez lineament (e.g., Aldrich, the northern margin of the fi eld across the 2007a; Kempter et al., 2007). We document the 1986). This alignment of volcanic centers Colorado Plateau–Rio Grande rift boundary westward migration of volcanism between 9 appears to coincide with a broad Proterozoic between the Laramide Chama Basin on the and 8 Ma across the northern JMVF, followed suture zone separating the 1.8–1.7 Ga southern west and the rift-related Abiquiu embayment by eastward migration between 7 and 5 Ma. In Yavapai terrane from the 1.7–1.6 Ga Mazatzal and Española Basin to the east include the this paper, we propose assigning all pre-caldera terrane (Karlstrom et al., 2004). The Rio Grande Coyote, Largo, Gonzales, Cañones, Garcia,

616 Geosphere, June 2013

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Figure 2. Index digital elevation model of the Jemez Mountains showing the location of geographic features mentioned in the text. AC— Alamo Canyon; AdlF—Arroyo de la Frijoles; BB—Bodega Butte; BD—Borrego Dome; BSP—Bear Springs Peak; CdP—Cerro del Pino; CdlG—Cerro de la Garita; CdlV—Cerrito de la Ventana; CP—Cerro Pedernal; CP(e) —Cerro Pelón (east); CP(w)—Cerro Pelón (west); CPel—Cerro Pelado; CY—Cerrito Yelo; EP—Encino Point; GC—Guacamalla Canyo; HC—Hondo Canyon; LC—Los Conchas; LCe— Los Cerritos; LG—Los Griegos; MdM—Mesa del Medio; PD—Ponderosa; PP—Polvadera Peak; PS—Pine Springs; RB—Redondo Border ; RC—Redondo Creek; RM—Rabbit Mountain; RWC—Red Wash Canyon; TC—Tres Cerros; TchP—Tschicoma Peak.

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107°W 106°50′W 106°40′W 106°30′W 106°20′W 106°10′W 106°W N ′ El Rito

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Figure 3. Fault map for the Jemez Mountains based on recent mapping. The heavy lines highlight major Rio Grande rift structures. The blue area highlights the gravity low beneath the northern Jemez Mountains and the Valles caldera (–260 mgal contour from Ferguson et al., 1995). The red line is the cross section shown in Figure 7.

Cerrito Blanco, Madera Canyon, Pajarito, and in the northeastern JMVF are down to the west. toward the western border faults of the Albu- Santa Clara (Fig. 3). These structures likely A prominent gravity low underlies the north- querque basin, probably as relatively continu- project southward beneath the volcanic ﬁ eld. ern Jemez Mountains south of Abiquiu (Fig. 3; ous structures (Fig. 3; Koning et al., 2007a). Some of these faults, including the Coyote, Ferguson et al., 1995). Steep gravity gradients Largo, and Cañones fault systems, were coincide with the east-down Coyote fault zone METHODS reverse faults or monoclines during Laramide on the west, the southeast-down Gonzalez and deformation and have been reactivated as nor- Cañones fault zones on the northwest, and Geochronology mal faults by rift extension (Lawrence, 1979; west-down faults on Lobato Mesa (Koning Smith, 1995; Kelley et al., 2005a, 2005b). et al., 2007a). The gravity gradients associated The 40Ar/39Ar dates were determined at the Most of the faults in the northwestern JMVF with the Coyote, Cañones, and Gonzales fault New Mexico Geochronology Research Labora- are down to the east, but faults on Lobato Mesa zones project south under the Valles caldera tory using methods similar to those described

618 Geosphere, June 2013

in McIntosh and Chapin (2004). An age of laser-fusion ages on sanidine, biotite, and horn- new dates are summarized in Table 1, and pre- 28.02 Ma for the Fish Canyon Tuff (Renne et al., blende. Analytical uncertainties for individual viously published 40Ar/39Ar dates are compiled 1998) was used in age calibration and to adjust samples are reported to two standard deviations in Table 2. The dates are plotted in map form on previously published dates. Many of the dates (95% conﬁ dence level). Detailed procedures Figure 4. Table 1 is organized temporally, from are incremental-heating plateau ages for bio- are described in the Supplemental File1. The oldest to youngest, and geographically. The tite, hornblende, and plagioclase phenocrysts and for groundmass concentrates from rocks 1Supplemental File. Description and interpretation of 40Ar/39Ar dates collected within the Valles caldera. If lacking datable phenocryst phases. The rhyolite you are viewing the PDF of this paper or reading it ofﬂ ine, please visit http://dx.doi.org/10.1130/GES00897.S1 or tuff and ash-fall tephra dates are single-crystal the full-text article on www.gsapubs.org to view the Supplemental File.

TABLE 1. SUMMARY OF 40Ar/39Ar STEP-HEATING AND FUSION RESULTS—JEMEZ MOUNTAINS ID Sample Laboratory Latitude Age number name number Unit (WGS83) Longitude Mineral (Ma) ± 2σ 1 P-20 55561-01 Volcanic clast in Hernandez Member 36.1157 –106.491 gm 29.29 ± 0.50 Northern Jemez—old intrusions 2 CM27 56729-02 Dike, NE of Cañones Mesa 36.217 –106.378 gm 19.72 ± 0.33 3 04Y09 56149-01 Basalt intrusion, Encino Point 36.133 –106.540 gm 18.94 ± 0.33 3 04Y09 56149-02 Basalt intrusion, Encino Point 36.133 –106.540 gm 19.00 ± 0.35 Southwestern and southern Jemez 4 01-PON-11a 53099-01 Lowest basalt, Borrego Mesa 35.669 –106.635 gm 9.39 ± 0.31 5 01-PON-12 53100-01 Lowest basalt, Borrego Mesa 35.668 –106.635 gm 9.45 ± 0.22 6 05BSP01 55553-01 Lower basalt, Paliza Canyon 35.732 –106.595 gm 9.43 ± 0.14 7 05BSP02 55540-01 Upper basaltic andesite, Paliza Canyon 35.732 –106.596 gm 9.37 ± 0.12 8 F04-13 55537-01 Basalt in San Juan Canyon 35.754 –106.613 gm 9.45 ± 0.07 9 05BSP03 55534 Canovas Canyon Rhyolite tuff 35.731 –106.599 hd 9.22 ± 0.36 10a 01-PON-1 53114-01 Canovas Canyon Rhyolite plug 35.670 –106.635 bi 9.47 ± 0.13 10b 01-PON-2 53115-01 Canovas Canyon Rhyolite plug 35.670 –106.635 bi 9.49 ± 0.18 11 01-PON-4 53116-21 Canovas Canyon Rhyolite tephra 35.668 –106.634 bi 9.80 ± 0.51 12 02-B66 54117-01 Canovas Canyon Rhyolite 35.650 –106.574 bi 9.79 ± 0.09 13 K-7-5 54047-01 Canovas Canyon Rhyolite 35.677 –106.528 bi 9.54 ± 0.16 14 K-8-2 54121-01 Bodego Butte basalt 35.665 –106.602 gm 9.11 ± 0.13 15 02-B45 54120-01 Oldest basalt fl ow in Hondo Canyon 35.694 –106.573 gm 9.58 ± 0.08 16 F04-19 55532-01 Los Griegos hornblende dacite 35.794 –106.557 hb 8.53 ± 0.63 17 F05-81 56301-01 Dacite dome SW Rabbit Mountain 35.827 –106.473 hb 8.66 ± 0.22 18 Ancha 6049 Pumice Ancha Canyon 35.811 –106.154 hb 8.48 ± 0.14 Northeastern Jemez—Lobato Formation 19 V-9 55550-01 Los Cerritos dacite 36.032 –106.280 gm 9.80 ± 0.15 20 V-11 55533 Lobato Formation dacite, Rio del Oso 36.038 –106.299 bi 10.45 ± 0.05 21 V-3 55551-01 Basalt S. of San Lorenzo 36.040 –106.285 gm 9.57 ± 0.07 22 V-17 55497-01 Sill and dike in Tesuque Formation 36.075 –106.256 gm 9.73 ± 0.21 23 04CM14 56790-01 Basalt fl ow, Arroyo Frijoles 36.169 –106.376 gm 10.08 ± 0.16 Pajarito Plateau 24 05GM05 55886-01 Paliza Canyon dacite, Guaje Canyon 35.934 –106.292 gm 9.46 ± 0.07 24 05GM05 55887-01 Paliza Canyon dacite, Guaje Canyon 35.934 –106.292 pl 9.50 ± 0.09 25 05GM13 56021-01 Pumice in Puye, Guaje Canyon 35.932 –106.301 hb 4.01 ± 0.21 Western Jemez 26 FJ-430 54457-01 Basalt clast in Paliza Canyon Formation 35.879 –106.661 gm 9.00 ± 0.13 27 FJ-403 54458-01 Paliza Canyon basalt 35.887 –106.671 gm 8.99 ± 0.09 28 FJ-434 54459-01 Basalt clast in Paliza Canyon Formation 35.880 –106.662 gm 8.99 ± 0.12 29 FJ-697-A 55178-01 Paliza Canyon basalt, Highway 126 35.886 –106.662 gm 8.98 ± 0.28 30 SS-6-12-03-5 54460-01 Paliza Canyon andesite 35.886 –106.677 pl 8.26 ± 0.09 31 SS-6-12-03-4 54446-25 Dacite on Paliza Canyon andesite 35.886 –106.677 bi 4.36 ± 0.07 Encino Point 32 04Y10 55837-01 Andesite dike, Encino Point 36.134 –106.551 gm 7.99 ± 0.10 32 04Y10 56791-01 Andesite dike, Encino Point 36.134 –106.551 gm 7.94 ± 0.10 33 04C5 56725-01 Basalt base, Mesa Escoba 36.140 –106.499 gm 7.74 ± 0.21 34 04C3 56724-01 Basalt in bottom of Cañones Canyon 36.128 –106.484 gm 7.79 ± 0.03 35 04C10-Top 56726-01 Top flow, Mesa Escoba 36.148 –106.467 gm 7.90 ± 0.08 36 CM21 56727-01 Basalt near base, Polvadera Mesa 36.157 –106.422 gm 7.89 ± 0.04 37 04CM23 55835-01 Basalt near top, Polvadera Mesa 36.157 –106.423 gm 8.33 ± 0.11 38 CM24 56728-01 Uppermost basalt, Polvadera Mesa 36.157 –106.423 gm 8.22 ± 0.13 39 9-17-03-1 55095-01 Lower basalt, Cañones Canyon 36.103 –106.502 gm 8.75 ± 0.06 40 9-17-03-2 55097-01 Upper andesite, Cañones Canyon 36.103 –106.502 gm 7.42 ± 0.13 41 P-25 55483-01 Basalt in Cañones Canyon 36.110 –106.497 gm 8.11 ± 0.11 42 9-19-03-1 55096-01 Basalt in Cañones Canyon 36.077 –106.502 gm 8.17 ± 0.08 43 P-27 55552-01 Topmost basalt, E side Cañones 36.116 –106.490 gm 8.10 ± 0.13 Flows south of Cerro Pelón (west) 44 06VSA01 57204-01 Andesite, NW wall caldera 35.999 –106.597 gm 7.70 ± 0.07 45 06VSA02 57155-01 Basalt below VSA01 35.998 –106.597 gm 7.80 ± 0.13 46 CdG06-003 57167-01 Basalt, S Cerro Pelón 36.004 –106.593 gm 7.79 ± 0.09 (continued)

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samples are numbered sequentially. Table 2 is of the Valles Caldera National Preserve (Goff the Geoanalytical Laboratory at Washington also arranged temporally and geographically; et al., 2011; Fig. 4) are also included in the State University using the methods of John- sample numbers for these published data are Supplemental File (see footnote 1). These data son et al. (1999). Rare-earth and other trace preceded by a “P.” are not discussed in detail in the main body of elements were analyzed in the same labora- The analytical age data, age spectra, qual- the paper but are described and interpreted in the tory using an Agilent model 4500 quadru- ity of the analyses, and probability plots for Supplemental File (see footnote 1). pole inductively coupled mass spectrometer pre-caldera rocks, which are the focus of this (ICP-MS); method description is available at paper, are presented in the Supplemental File Geochemistry http://www.sees.wsu.edu/Geolab/note/icpms (DRIntro , Figs. DR1–DR4, and Tables DR1 .html). In addition, one sample of pumice was and DR2 [see footnote 1]). Analytical data, age Major elements and selected trace elements analyzed using the electron microprobe at the spectra, and probability plots for 15 caldera and for seven lavas and one dike (Table 3) were New Mexico Institute of Mining and Technol- postcaldera samples collected during mapping analyzed by X-ray fluorescence (XRF) in ogy (Table 3).

TABLE 1. SUMMARY OF 40Ar/39Ar STEP-HEATING AND FUSION RESULTS—JEMEZ MOUNTAINS (continued) ID Sample Laboratory Latitude Age number name number Unit (WGS83) Longitude Mineral (Ma) ± 2σ La Grulla Plateau 47 9-15-3-2 55098-02 Trachyandesite, Four Hills 36.080 –106.519 pl 7.36 ± 0.16 48 04CDG04 55161-01 Fine-grained rhyolite/trachyte, Four Hills 36.060 –106.536 gm 6.51 ± 0.21 49 03CDG-03 55091-01 Trachyandesite, Cerro del Grant 36.025 –106.540 hd 7.68 ± 0.04 50 Tophill 33 55088-01 Dacite, Hill 33 36.008 –106.516 bi 7.27 ± 0.06 51 04CDG5 55179-01 Andesite, western base Hill 33 36.008 –106.524 gm 7.81 ± 0.09 52 F05-194 56302-01 Porphyritic dacite, Cerro de la Garita 35.994 –106.530 bi 7.61 ± 0.07 53 F06-21 57201-01 Dacite, Cerro de la Garita 35.996 –106.531 bi 7.34 ± 0.14 54 F05-171 56297-01 Middle dacite 35.991 –106.477 bi 7.66 ± 0.04 55 JG05-9 supp 56306-01 Rhyodacite (same unit as F05-171) 35.987 –106.476 bi 7.78 ± 0.10 56 F05-178 56298-01 Upper rhyodacite, N caldera wall 36.000 –106.488 bi 7.42 ± 0.05 Bearhead intrusions 57 K-10-3 54116-01 Bearhead Rhyolite dome 35.737 –106.597 bi 6.51 ± 0.48 58 K-7-31 54118 Rhyolite east of Tres Cerros 35.693 –106.529 san 6.86 ± 0.28 59 F04-31 55538-01 Rhyolite, Cerro Pelado 35.775 –106.545 obs 7.62 ± 0.44 60 F04-32 55539-01 Rhyolite, Cerro Pelado 35.773 –106.547 gm 7.83 ± 0.26 61 Povp 2 55185 Cañon de la Mora rhyolite 36.015 –106.488 san 7.09 ± 0.13 62 JG05-14 56305-01 Bearhead Rhyolite (?) dike 35.982 –106.478 bi 4.81 ± 0.04 Northern Tschicoma domes 63 P-13 55487-01 Dacite, Cañoncito Seco 36.074 –106.483 bi 3.26 ± 0.04 64 P-39 55486-01 Dacite lower Chihuahueños Canyon 36.121 –106.465 gm 3.34 ± 0.09 64 P-39 55562-01 Dacite lower Chihuahueños Canyon 36.121 –106.465 pl 3.76 ± 0.19 65 P3-11 55563-01 Enclave in Tchicoma dacite 36.030 –106.466 gm 3.37 ± 0.05 66 Povp 1 55184-01 Andesite, W fork, Polvadera Creek 36.085 –106.465 bi 3.36 ± 0.06 67 V-39 55490-01 Gallina flow 36.042 –106.341 bi 4.49 ± 0.21 68 V-36 55485-01 Dacite below Gallina fl ow 36.046 –106.336 gm 3.66 ± 0.09 68 V-36 55491-01 “ 36.046 –106.336 pl 4.04 ± 0.18 69 B04-10-25 55846-01 Dacite, Cerro Pelón (east) 36.145 –106.405 bi 3.64 ± 0.03 70 B04-10-22 55847-01 Dacite, Cañones Mesa 36.146 –106.410 bi 3.61 ± 0.05 71 V-14 55496-01 El Alto Basalt, Mesa de Abiquiu 36.103 –106.361 gm 2.87 ± 0.02 Northeastern Tschicoma domes 72 F05-185 56300-01 Rhyodacite dome N. of Cerro Rubio 35.953 –106.400 bi 4.21 ± 0.12 73 F05-156 56309-01 Rendija Canyon rhyodacite 35.910 –106.384 pl 3.50 ± 0.23 74 F05-118 56303-02 Sawyer dome dacite 35.846 –106.439 hd 3.44 ± 0.30 75 F08-68 58993-01 Upper Quemazon Canyon Dacite 35.926 –106.386 gm 2.92 ± 0.03 76 F03-04 54474-01 Tschicoma dacite megabreccia 35.880 –106.544 gm 2.01 ± 0.02 76 F03-04-2 54475-01 Tschicoma dacite megabreccia 35.880 –106.544 pl 2.20 ± 0.05 77 F01-54 53296-01 El Rechuelos Rhyolite 36.049 –106.422 2.09 ± 0.02 Toledo and Valles caldera ignimbrites, fl ows, and intrusions (discussed in GSA Data Repository Item 4 [see text footnote 1]) A1 V-13 55489 Otowi on Mesa de Abiquiu 36.113 –106.360 san 1.55 ± 0.03 A2 V15 56005 Otowi on Mesa de Abiquiu 36.077 –106.259 san 1.66 ± 0.03 A3 F05-133 56413 Otowi beneath Rabbit Mountain debris fl ow 35.794 –106.448 san 1.59 ± 0.04 A4 F05-123 56261 Otowi beneath Rabbit Mountain debris fl ow 35.806 –106.401 san 1.68 ± 0.03 A5 F05-135 56414 Cerro Toledo in upper Frijoles Canyon 35.833 –106.415 san 1.40 ± 0.06 A6 F05-150 56264 Otowi from NW caldera 35.967 –106.610 san 1.59 ± 0.03 Rabbit Mountain A7 obsidian 53930-02 Rabbit Mountain obsidian, Obsidian Ridge 35.828 –106.455 obs 1.44 ± 0.01 A8 F05-177 56262 Cerro Toledo dike 36.000 –106.486 san 1.61 ± 0.03 A9 Cerrito Negro 9486 Tshirege blocks on Cerrito Negro 35.571 –106.725 san 1.26 ± 0.02 A10 F03-14b 54479 Deer Canyon lava 35.869 –106.605 san 1.25 ± 0.03 A11 F03-52 54477 Redondo Creek Rhyolite 35.914 –106.592 san 1.23 ± 0.02 A12 F03-53 54478 Redondo Creek Rhyolite type locality 35.900 –106.564 san 1.24 ± 0.03 A13 F03-50 54476 Cerro Santa Rosa ignimbrite 35.954 –106.525 san 0.91 ± 0.03 A14 JG05-15C 56304 Cerro Seco hydromagmatic tuff 35.965 –106.592 san 0.78 ± 0.04 A15 F05-137 56412 Pumice in Cerro Seco ignimbrite 35.965 –106.592 san 0.77 ± 0.03 Note: gm—groundmass; san—sanidine ; obs—obsidian; pl—plagioclase; hd—hornblende; bi—biotite.

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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 ) 3 0 6 2 0 3 5 5 4 3 3 0 9 6 6 4 3 8 2 0 1 4 9 6 9 3 8 9 5 1 9 5 1 4 8 9 6 0 9 4 0 3 4 6 4 8 7 6 1 9 4 8 5 5 1 1 9 3 0 2 9 8 7 9 5 5 0 4 ...... 9 8 8 8 8 9 9 9 8 8 8 5 9 8 8 9 9 8 5 9 0 9 9 7 8 8 9 8 9 0 8 1 9 9 1 2 1 2 1 1 Adjusted age (Ma) continued ( 3 5 1 7 7 0 5 0 1 4 0 7 9 4 6 4 0 6 2 4 0 5 0 1 1 6 7 5 0 9 3 4 0 4 0 6 8 4 7 0 3 σ 2 1 0 2 7 2 1 8 3 2 1 8 1 0 1 0 3 2 1 8 2 3 7 0 2 6 2 1 1 2 6 1 1 1 3 4 2 6 4 0 1 ...... 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± 4 8 9 7 0 8 5 3 7 1 8 2 5 2 9 8 2 3 7 4 6 5 9 5 6 4 8 6 3 4 0 0 3 2 8 3 5 9 2 1 7 5 2 1 9 6 8 8 3 6 7 9 3 7 9 0 4 9 7 4 8 4 3 1 0 4 5 5 7 6 9 8 0 2 8 6 8 4 2 3 3 ...... 9 8 8 8 9 9 8 9 9 8 8 9 8 8 8 9 8 5 9 0 8 8 5 0 9 9 9 7 0 9 8 9 9 8 9 8 9 9 8 0 9 2 1 1 1 1 1 1 2 1 Age (Ma) ± 2 Reported n r i l l l l l l l l l l l i l i l l l m m m m m m m m m m m m m m m m m m m m m a b p p p p p p p p p p p p b p p b p w g g g g g g g g g g g g g g g g g g g g g s 5 6 8 7 0 3 2 6 8 2 6 0 4 0 7 6 8 7 3 4 3 4 4 7 9 9 2 5 7 3 3 3 6 7 8 4 7 8 7 1 5 1 0 7 1 0 3 0 7 7 5 5 1 6 7 3 4 4 9 6 0 9 4 7 3 5 9 8 8 2 3 3 3 6 3 0 3 7 9 6 6 1 6 8 7 3 4 8 9 2 9 7 0 6 8 8 4 1 1 9 6 7 4 2 9 6 5 8 9 8 9 3 2 8 3 8 7 7 2 1 6 1 6 8 8 6 6 6 6 6 8 9 6 0 1 1 3 7 7 6 6 9 7 5 4 0 8 7 3 9 9 4 6 1 8 6 9 4 9 8 6 9 9 0 3 2 5 5 5 5 3 3 5 2 2 5 5 6 2 6 5 3 2 3 5 5 5 5 3 5 3 3 5 3 2 6 3 4 5 2 3 5 3 3 5 ...... 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – 4 3 2 7 7 0 3 0 7 4 0 0 0 7 9 4 7 4 8 1 3 3 9 6 3 0 3 8 6 7 3 1 0 8 3 3 1 7 7 1 7 9 8 2 1 4 6 0 2 5 6 3 0 0 6 3 0 9 8 9 6 0 8 3 5 3 5 4 0 3 2 1 0 3 7 6 6 3 1 1 1 6 1 6 0 6 5 8 7 5 1 4 9 5 1 8 9 0 3 0 6 8 0 6 1 5 3 5 9 5 3 7 6 3 0 5 4 8 4 8 4 4 1 3 1 3 4 4 0 2 3 7 9 8 6 5 5 8 5 2 3 8 6 4 6 6 4 2 3 1 6 7 3 5 7 6 3 0 2 5 2 1 1 1 7 0 7 1 7 7 7 1 7 1 7 7 7 5 7 7 7 7 6 7 6 7 5 5 7 0 7 2 6 6 6 7 7 7 6 6 0 2 7 6 7 ...... 5 6 5 5 5 5 5 5 5 6 5 5 6 6 5 6 5 5 6 5 5 5 5 5 5 5 5 6 5 5 5 5 6 5 5 5 5 5 6 5 5 Latitude 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 (WGS83) Longitude Mineral e t i l Ar RESULTS—JEMEZ MOUNTAINS Ar RESULTS—JEMEZ o e e 39 t t y i i h s s r e e Ar/ d d n 40 n n o y a a e e e e e e e e y y n t t t t t t t t i i i i i i i i h h a t s s s s s s s s l e e e c c a C t t t e e e e e e e e a i i i a a t n i r r e e e e d d d s d d d c d d c c s t t n t t t t a a a a n i i i i n n n n n a n a n a n a t a l l l l o s s s c c U v a a a a a a b a d d a d n i i o o o o y e e e t t t t f y y y y y y y y y y y y o l l l l e y y y y e e f n t t h h M h h h h h h M M h h h h n i a a i a a h h h h V u a r r r t r c c c c c c c c c c c c c s s c s s a l a a a C a a a a a a a a a a a a a a a a a a a n n n n n C s s s r r r r r r r r r r r r e i i i t t t b t t t t t b b t d t d t b t t h o o o o o , i e s y y y y y m s m m e n n n n n n n n n n n n n n n n n n d a n n n n n a e a a o o o o o o o o o o o o o o o o o o e m o a a a a a h d h h t y y y y y y y y y y y y y y y y y y t W i o i n n n n n n n n n n n n n n n n n n n C C C C C r C C C c D d r a a a a a a a a a a a a a a a a a a a f f f a s s s s s e e o o o d o C e C c C C C C e C C C C e C C C C C C C e C a a a a a i t t t t R C y t t i i t t t t t t i i g v v v v v l l l l l l l l e e a a a a a a a a a a a a a a a a a a t t , , h n n n n e o o o o o i i a a a i a a a i i a a i z z z z z z z z z z z z z z z z z z r c i i i i i i i i i i i i i i i i i i e e n n n c n c n s l l l l s l l s s s s s s s s s l l l r l l l l l l l l s l k k a a a a a a i a a i a a a a a a a a a a a a a a a a a a a a a a a o a a a a a a a r P B P B B C B B P P P P D C P B B P P B P P T C B P B C D B P P B D P C P P D B P ) ) ) ) ) 7 7 7 7 7 ) ) 0 0 0 0 0 7 7 0 0 0 0 0 0 0 2 2 2 2 2 0 0 ( ( ( ( ( ) ) ) ) 2 2 ( ( h h h h h 6 6 6 6 s s s s s 0 0 0 0 s s o o o o o 0 0 0 0 n n t t t t t i i 2 2 2 2 n n n n n TABLE 2. SUMMARY OF PREVIOUS PUBLISHED 2. SUMMARY TABLE e g g ( ( ( ( I I I I I c g g . . . . c c c c c i i l l l l n a a a a M M M M M e M M r t t t t d d d d d e d d e e e e f n n n n n l l l l n n e ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) a a a a a e e e e a a i i i i 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 R r r r r n n n n n o o 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 i i i i i b b b b l l l l l d d 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 r r r r r a a a a a a 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 e e e e e ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( G G G G n n b b b b b t t t t t t t t t t t t t t t t t t t t t t t t t t t t t t e e e e o o m m m m m e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e d d d d d d t t t t t t t t t t t t t t t t t t t t t t t t t t t t t t l l l l l l a a a a a s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s o o o o a a h h h h h u u u u u u u u u u u u u u u u u u u u u u u u u u u u u u J J J J J C W J J J J J J J J J J J J W W J C J J J J J C J J C J M C J J J M J W e 0 m 3 4 8 7 8 3 3 2 1 1 a 0 2 1 F - - - 1 1 5 6 0 4 2 1 7 1 1 7 3 3 - - 5 n 1 8 4 2 9 2 3 1 C C 5 1 M M 3 8 8 8 5 3 D D d a 2 1 1 1 1 1 1 1 - C - M P 8 8 P S P a a - d a d d b - - - 9 9 9 6 2 e P o b a D a a P B M M M 1 M M l 9 9 B k - - p c c c c s B S A S C M B B B B D k k c - - c c A A B 8 B p S S B T T T L T T T S S T C C C B B B L T L E W W L L T T T T T C C W F W L S S L L m R R L L R a S r e b 0 1 7 1 4 2 5 8 7 2 4 1 3 5 4 0 2 9 9 1 8 8 3 5 6 6 5 7 2 6 3 9 7 4 5 2 0 6 4 3 3 1 2 5 3 5 2 5 1 2 3 5 2 3 5 2 1 1 1 2 1 2 5 2 1 1 2 1 1 3 2 3 3 P P P P P P P P P ID m P P P P P P P37 LC-98-31 Chamberlin and McIntosh (2007) Paliza Canyon Formation, Mesita Cocida 35.62306 –106.55913 gm 7.16 ± 0.13 P P P P P P P P P P36 LC-98-13 Chamberlin and McIntosh (2007) Paliza Canyon Formation, Mesita Cocida 35.62016 –106.56117 gm 6.79 0.24 P P P P P P P P P P P P40 LC-99-2 Chamberlin and McIntosh (2007) Paliza Canyon Formation trachydacite 35.60796 –106.60028 bi 9.44 ± 0.16 P51 Section D/E Lavine et al. (1996) Paliza Canyon Formation dacite tuff 35.76667 –106.41250 bi 9.11 ± 0.05 9.16 P P P P38P39 GSZ-431C 6.13.98.1 Chamberlin and McIntosh (2007) Chamberlin and McIntosh (2007) Paliza Canyon Formation, Mesita Cocida Paliza Canyon Formation trachydacite 35.59739 –106.55596 35.60288 –106.60105 gm hb 7.18 ± 9.23 0.26 ± 0.96 P47P48P49P50 LC-98-32A Section Section B Section C Chamberlin and McIntosh (2007) Lavine et al. (1996) et al. (1996) Lavine Paliza Canyon Formation volcanic sediments et al. (1996) Lavine 35.62084 –106.55947 Paliza Canyon Formation dacite tephra Paliza Canyon Formation dacite tuff obs Paliza Canyon Formation dacite block and ash 35.70833 35.77917 –106.39583 9.38 –106.36250 35.72917 ± –106.37917 bi 0.06 bi bi 9.53 9.47 ± 9.18 ± 0.02 0.06 ± 9.59 9.53 0.02 9.24 P P P P43P44P45 LC-98-5 LC-98-2 LC-98-11 Chamberlin and McIntosh (2007) Chamberlin and McIntosh (2007) Chamberlin and McIntosh (2007) Paliza Canyon Formation, Bodego Butte Paliza Canyon Formation, Bodego Butte Paliza Canyon Formation volcanic sediments 35.58923 35.62208 35.55335 –106.55740 –106.61584 –106.61291 ad gm gm 5.31 9.17 9.25 ± ± ± 0.08 0.10 0.13 P41P42 GSZ-493 LC-98-4 Chamberlin and McIntosh (2007) Chamberlin and McIntosh (2007) Paliza Canyon Formation, Bodego Butte Paliza Canyon Formation, Bodego Butte 35.61415 35.56681 –106.55672 –106.60051 gm gm 9.04 9.04 ± 0.18 ± 0.12 u n Northern Jemez—old intrusions Northeastern Jemez—Lobato Formation Southwestern and southern Jemez

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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. ) 1 9 6 3 2 6 5 8 5 0 8 9 3 0 8 0 4 5 1 8 3 5 6 0 4 4 5 1 0 6 8 6 7 2 5 8 8 2 9 8 1 8 0 9 9 7 7 7 8 9 1 8 2 9 2 0 6 2 0 4 8 1 8 9 7 4 ...... 3 2 6 6 6 6 7 6 6 6 6 6 6 6 6 6 0 7 7 1 6 6 7 6 7 6 6 7 1 6 6 6 7 1 1 1 1 Adjusted age (Ma) continued ( 1 4 6 8 6 4 5 5 6 6 3 9 2 1 4 6 2 7 3 3 6 1 3 0 3 0 0 7 4 9 2 6 8 3 4 7 3 4 σ 5 3 0 0 0 0 0 0 0 0 0 0 0 1 0 1 0 0 2 2 2 1 0 1 0 0 0 1 0 1 1 0 5 1 0 0 0 1 ...... t 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 s e ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± 1 9 3 9 2 2 4 9 8 4 6 8 5 4 7 1 1 7 1 0 1 1 4 7 6 6 6 0 4 9 6 7 2 7 1 2 3 1 5 1 8 2 1 7 7 7 8 9 8 8 8 0 5 8 9 6 0 1 8 0 8 1 0 1 1 7 8 8 9 8 6 9 4 1 7 4 7 ...... 2 3 6 6 6 7 1 6 6 6 6 0 6 6 6 6 7 9 1 6 7 6 6 6 6 6 7 6 0 7 6 9 7 4 6 6 7 6 6 1 1 1 1 1 1 Age (Ma) ± 2 Reported n n n n n n n n n n n n n n n n n n n n n n n n n n l l l m m m m m m m m m m a a a a a a a a a a a a a a a a a a a a a a a a a a p p p g g g g g g g g g g s s s s s s s s s s s s s s s s s s s s s s s s s s ) 3 3 7 6 6 0 4 0 7 0 9 0 0 8 9 9 7 7 2 2 5 0 6 8 8 3 1 8 1 5 0 5 1 5 5 4 3 5 0 0 1 4 7 2 5 8 1 4 0 2 2 7 3 1 3 9 3 2 3 2 4 5 0 9 1 2 0 4 8 4 9 1 8 7 7 4 1 7 0 7 3 9 9 4 3 8 7 5 9 1 6 1111 san 7.06 ± 0.04 7.10 2 6 0 3 0 1 8 7 3 3 2 0 7 8 2 9 3 2 2 5 4 3 2 5 2 5 4 5 4 4 1 3 5 5 5 5 3 5 6 3 4 4 5 4 5 ...... 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 continued 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 – – – – – – – – – – – – – – – – – – – – – – – – – – – – 7 3 4 6 3 7 1 3 0 7 8 4 0 0 7 7 9 4 8 8 2 6 4 4 3 6 6 1 1 2 3 4 5 6 6 5 3 0 1 2 4 0 1 9 6 8 2 7 2 4 0 0 1 4 5 5 8 8 7 4 0 6 8 5 9 1 9 8 5 9 5 9 9 3 2 8 7 0 4 8 9 7 0 5 5 0 0 4 2 5 5 0 7 0 0 8 7 8 7 0 5 3 0 2 2 4 5 9 3 3 0 2 — — — — — — — — — — — 5 0 0 7 7 7 6 7 7 9 6 7 0 6 0 7 7 7 1 2 0 7 8 7 0 1 0 7 ...... 6 5 6 5 5 5 5 6 5 5 5 5 5 6 5 5 5 6 6 5 6 5 5 6 5 6 6 5 Latitude 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 (WGS83) Longitude Mineral r e b m e r r r Ar RESULTS—JEMEZ MOUNTAINS ( MOUNTAINS Ar RESULTS—JEMEZ n M e e e o 39 f f b b b y u k n n n o m m m n l Ar/ T a s a o o e e e o e 40 e e o y k y a t y C r t Y i t M M M i n a n l P r t t t n e s l l l n e a f f f t n a e a o a k e a a a f f f t r t e a a a o d r l g o i a d d P U C C a u u u C s s s y o r l d a C e a d r h l r e a a i a a r i T T T a a a n n e r n o N c s P a n o o d w c e c e P l l a R h e H m m B B B l e A d J a e a a a , o n n o n r t t t e r C e P t b a a e r p l l l z c n C e y i d i i a a a n n n n a r a a f i Y T Y l r s r d r r a a a c o l n C C b u m i o o o o e i s a d r r r r r L P f o l A i i i i a e B A o a o b e e t t t t H e s o h e n a a e e e t B o R t a a a t t d m i a i o h h w i i a a a a a t e e h h C a r t t t t t r r r n d d B C B P P P o M u l t t M s s o r s r r r r s r s s r s l R u u a a , , , , , , m m m m o f p M e t e e l l l B e e e e e e f a l r r r r l l l o a a o f f a o o n n l e e e s d d d u d o o o o a C a a a n e C e s w P n o s C W o C e h k k k a a o e r f f f i i i n n t e T e , F F F F e d d d e e e e e e e e e e e e e e e e e C C C a a u k e e e e t t t t P t t t t t t t t t t t t t W a r i i i i i i i i i i i i i i i i i y y o o o o t t t d t f f f o l l l l l l l l l l l l l l l l l t l l l l c c c c t t t t f l i i i i o h h a o o o o s o o o o o o o o o o o o o o o o o a a a a a a a a o r a c c v f f f f y y w y y r y y y y y y y y y y y y y m r m m m s s s l s f f f f b b b b f a a f h h h e h h h h h h e h h h h h h h h u e u u a a u a o a u u r u u r o o o o u P R R L L P P R L R T T T P P R T R B R R R C B T B L R t R P R R R R R B R T R ) 7 ) ) ) 0 7 7 7 0 0 0 0 ) ) ) ) ) 2 0 0 0 ( 1 1 1 1 1 ) ) ) ) 2 2 2 9 9 9 9 9 ( ( ( h 6 6 6 6 9 9 9 9 9 s ) ) 0 0 0 0 s s s ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) 1 1 1 1 1 o 3 3 0 0 0 0 n n n t ( ( ( ( ( 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 i i i 1 1 2 2 2 2 n e 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 g g g ( ( ( ( I n n n n n 0 0 c 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 g g g . . . . c a a a a a i i i 2 2 l l l l l l l l l n ) ) ) ) ) 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 ( ( r r r r r a a a a ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( M e 1 1 1 1 1 M M M . . a a a a a r l l l l l l l l l l l l l l l l l t t t t 0 0 0 0 0 l l l l l l l l l l l l l l l d e d d d a a e e e e H H H H H TABLE 2. SUMMARY OF PREVIOUS PUBLISHED 2. SUMMARY TABLE 0 0 0 0 0 f e e e e e e e e e e e e e e e n l l l l t n t n n 2 2 2 2 2 e p p p p p p p p p p p p p p p ) ) ) ) ) d d d d d a e e e e ( ( ( ( ( e a a e a i i i i 3 3 3 3 3 n n n n n S S S S S S S S S S S S S S S R r r r r . . . . . ) n l l l l l o o o o o 0 0 0 0 0 i a a a a a b b b b l d d d d d d d d d d d d d d d a a a a a d d d d d 0 0 0 0 0 r a a a a h h h h h n n n n n n n n n n n n n n n t t t t t a a a a a 2 2 2 2 2 e s s s s s a ( a a ( a a ( a ( a a ( a a a a a a a e e e e e G G G G n n n n n b o o o o o t t t t t t t t t t t t t t t t t t t t e e e e t t o t o o t t o o h h h h h m e e e e e e e e e e e e e e e e e e e e t t t t t d d d d n n n d d d n d d n t t t t t t t t t t t t t t t t t t t t i i i i i l l l l l l l l l I I I I I a s s s s s s s s s s s s s s s s s s s s o o o o c c c a a a c a a c h m m m m m u u u u u u u u u u u u u u u u u u u u continued C J S W W S W M M S S W J J J M J J J J J J J M J M S J M M M J J J M J M J J J 2 1 4 e - - - 1 1 5 3 3 2 1 2 m 3 0 1 0 2 0 1 2 1 a 8 4 3 4 2 1 5 - - - 6 6 6 7 6 P 8 P 4 0 - - - - 0 4 - - n 1 6 7 F P P t t t t t C 8 9 0 9 9 9 9 9 9 9 9 C 3 T - J R 2 2 1 8 P 1 1 F Y H - - - H N C p p p p p 5 4 9 e Y A R 4 B R P P P P P A 1 2 l 9 P 2 1 1 1 C S D B D T C B C P s s s s s R I - ows, and fall deposits W 8 A A A 0 E C p N E S N C C C C C 0 0 0 A A L T T B E 8 G G G G G C F S S S S S C C C m L a P P P G G G G G S S S S r e b 0 4 3 6 0 1 5 4 2 0 4 6 9 8 9 8 6 5 0 7 2 6 7 6 3 2 9 8 5 4 1 5 3 8 4 3 9 9 2 0 1 6 6 6 0 0 0 0 5 7 8 0 7 0 8 6 8 9 6 6 8 9 0 0 5 0 0 6 8 7 7 9 7 6 8 9 9 7 7 6 ID m 1 1 1 1 1 1 1 1 1 1 1 P P P P87 9202P Justet and Spell (2001) Rhyolite east of Cerro Pelado 35.79278 –106.56889 san 6.82 ± 0.04 6.86 P P71 SPC01-9-21-3 et al. (2006) WoldeGabriel Santa Clara Canyon andesite 35.99050 –106.31883 gm 7.78 ± 0.04 7.83 P P P P P P P P P97P98P99 GBR SHC NECY Justet and Spell (2001) Justet and Spell (2001) Justet and Spell (2001)Yelo Rhyolite northwest Cerrito Rhyolite south Hondo CanyonYelo Rhyolite northeast Cerrito 35.67556 35.70917 35.67500 –106.53639 –106.55472 –106.51000 san san san 7.92 11.09 8.92 ± ± 0.32 ± 1.57 0.98 7.97 11.16 8.97 P P85 SM Justet and Spell (2001) Rhyolite San Miguel Mountain 35.75639 –106.39028 san 6.8 ± 0.04 6.84 P P77P78 NHC WBHP and Spell (2001) Justet Justet and Spell (2001) Rhyolite north Hondo Canyon Rhyolite west Bearhead Peak 35.70917 35.72472 –106.55056 –106.48944 san san 6.57 6.52 ± ± 0.05 0.03 6.61 6.56 P P P P P P P P P P91 DB and Spell (2001) Justet Rhyolite west Bearhead Peak 35.72472 –106.48944 san 6.91 ± 0.03 6.95 P P P P62 SPC01-9-20-1 et al. (2006) WoldeGabriel Santa Clara Canyon Trachybasalt, 36.00950 –106.29517 gm 10.16 ± 0.06 10.22 P P P80P81 CB SEAP Justet and Spell (2001) and Spell (2001) Justet Aspen Peak Rhyolite southeast Rhyolite west of Cerro Belitas 35.75806 35.74000 –106.49444 –106.40833 san san 6.71 6.69 ± ± 0.27 0.03 6.75 6.73 P P93 31B Justet and Spell (2001) Rhyolite southwest Peralta Canyon 35.69139 –106.48750 san 6.97 ± 0.09 7.01 u P111 GSZ-404B Chamberlin and McIntosh (2007) MemberTuff Sedimentary unit, Peralta 35.54070 –106.57714 san 6.79 ± 0.09 P P112 5.18.98 Chamberlin and McIntosh (2007) MemberTuff Sedimentary unit, Peralta 35.54890 –106.59242 san 6.80 ± 0.02 P P P P P P P P P P n Northeastern Jemez—Lobato Formation ( La Grulla Plateau Bearhead intrusions, ﬂ Encino Point

622 Geosphere, June 2013

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 ) Adjusted age (Ma) continued ( σ Age (Ma) ± 2 Reported ) continued Latitude (WGS83) Longitude Mineral Ar RESULTS—JEMEZ MOUNTAINS ( MOUNTAINS Ar RESULTS—JEMEZ 39 Ar/ 40 ) TABLE 2. SUMMARY OF PREVIOUS PUBLISHED 2. SUMMARY TABLE continued ID P113P114P115P116P117P118 LC-98-36P119 LC-99-11 GSZ-429C LC-99-4 LC-99-10 and McIntosh (2007) Chamberlin LC-99-9 and McIntosh (2007) Chamberlin LC-99-5A Chamberlin and McIntosh (2007) MemberTuff Sedimentary unit, Peralta Chamberlin and McIntosh (2007) MemberTuff Sedimentary unit, Peralta and McIntosh (2007) Chamberlin MemberTuff Sedimentary unit, Peralta Chamberlin and McIntosh (2007) and McIntosh (2007) Chamberlin MemberTuff Sedimentary unit, Peralta MemberTuff Sedimentary unit, Peralta 35.54161 MemberTuff Sedimentary unit, Peralta MemberTuff Peralta 35.60640 35.59450 –106.59842 –106.58020 –106.58019 35.58399 35.60363 san –106.59656 35.59967 –106.57149 san san –106.58379 san san 6.81 6.90 pl 6.92 ± 35.58739 ± 6.93 0.08 ± 7.02 0.06 –106.54252 0.02 ± 7.03 ± 0.06 0.12 san ± 0.54 6.89 ± 0.14 P120P121P122P123 LC-98-25BP124 LC-98-28P125 Chamberlin and McIntosh (2007)P126 TDI0P127 TD13 and McIntosh (2007) Chamberlin P128 LB13 MemberTuff Peralta P129 A-219P130 SPC01-9-20-2 Cochiti FormationP131 SPC01-9-12-5 Justet (2003)P132 Justet (2003)P133 F01-55 Justet (2003) et al. (2006)P134 WoldeGabriel F01-56 Maldonado et al. (2013) et al. (2006)P135 WoldeGabriel F01-57P136 5-25-83-1P137 5-25-83-2P138 6-22-83-3 et al. (2006) WoldeGabriel P139 6-22-83-5 Santa Clara Canyon Dacite, et al. (2006) WoldeGabriel P140 6-22-83-9 Santa Clara Canyon Dacite, Dacite et al. (2006) 6-22-83-12 WoldeGabriel et al. (2007) Broxton 35.59057P141 et al. (2007) Broxton P142 10-8-90-4 Dacite –106.55008 et al. (2007) Broxton DaciteP143 8-21-88-1 LAPC-98-13 35.56301 et al. (2007) Broxton FormationP144Tschicoma Rhyodacite, Andesite SPC01-9-20-2 et al. (2007) Broxton FormationTschicoma Dacite, SPC01-9-12-5 Broxton et al. (2007) –106.54785 san FormationTschicoma Dacite, LAPC98-13P145 et al. (2007) Broxton P146 et al. (2006) WoldeGabriel et al. (2007) Broxton 11-19-84-1 et al. (2006) WoldeGabriel Formation, Sawyer Dome Tschicoma obs 36.00367P147 DEB1-91-7 et al. (2006) WoldeGabriel Formation, Sawyer Dome Tschicoma 36.00183P148 Formation, Cerro Grande Tschicoma –106.29133 6.73 36.05440 Broxton et al. (2007) Formation, Pajarito Mountain Tschicoma –106.29183 Formation, Pajarito Mountain Tschicoma et al. (2007) Broxton P149 ER4 Formation, Pajarito Mountain –106.41043 Tschicoma Formation, Rendija Canyon ± Tschicoma Formation Dacite et al. (2007) Broxton Tschicoma 6.35 ER6 36.03615 bi 35.83700 Formation Dacite 0.38 Formation, Pipeline Road Tschicoma Tschicoma ER8 36.02170 biP150 35.83350 F01-54 Formation, Caballo Mountain Tschicoma –106.40373 ± 35.88183 –106.44012P151 hd 35.87363 –106.37792 35.88931 0.20 –106.43895P152 35.87602 –106.40814P153 –106.41076 35.88833 A13 Formation, North Mesa Justet (2003) Tschicoma –106.40261 3.79P154 –106.39933 pl hd — Justet (2003) 36.08889 Formation, Rendija Canyon Tschicoma 35.95356 –106.30000 3.88P155 hd 35.92737 7-1-83-1 hd et al. (2006) WoldeGabriel 36.17500 Justet (2003) 36.20722 Formation, Guaje Canyon Tschicoma SLR93-1MP156 hd 3.21 gm ± –106.38917 –106.36467 gm –106.38167P157 DN97-16 36.00367 –106.37167 ± gm –106.43000 0.17P158 san DN97-16 36.00183 ± 0.09P159 –106.29133 DN97-07 3.67 5.34 Maldonado and Miggins (2007) 0.35 RWTB4-B8 3.81 35.90300 gm 4.46P160 pl –106.29183 3.18 Broxton et al. (2007) 35.89319 hd et al. (1996) WoldeGabriel hd Rechuelos Rhyolite El gm 3.92 DN97-17B 3.35P161 3.07 35.86729 ± ± 3.09 –106.34830 3.23 DN97-19AP162 et al. (2001) WoldeGabriel –106.29579 2.93 ± bi ±Alto Basalt El 0.29 0.36 4.98P163 et al. (2001) WoldeGabriel –106.19392 ± 0.58 ± bi El Rechuelos Rhyolite 0.20 Frij-1 et al. (2001) WoldeGabriel et al. (2001) WoldeGabriel ± 0.17 ± 3.06 0.11 El Rechuelos Rhyolite Frij-2 san 5.37 2.97 ± 4.66 0.08 san et al. (2001) WoldeGabriel 4.9 3.79 Canyon Formation trachybasalt Paliza El Rechuelos Rhyolite 4.49 0.06 Frij-8 0.05 san et al. (2001) WoldeGabriel Frij-10 ± Canyon basalt Bayo ± 3.79 ±Alamos Canyon Paliza Canyon Formation, Los Frij-7 ± Ancho-1 0.15 Canyon basalt Bayo ± 5.01 0.22 4.39 0.17 0.21 Canyon basalt Bayo pumice Puye et al. (2006) WoldeGabriel 0.7 5.04 35.88406 4.98 ± et al. (2006) WoldeGabriel Tb3 (subsurface basalt) 2.99 ± 5.36 0.17 3.81 et al. (2006) WoldeGabriel 2.35 Tb3 (subsurface basalt) –106.35319 ± et al. (2006) WoldeGabriel 36.04855 4.93 0.13 ± 0.03 et al. (2006) WoldeGabriel 3.81 et al. (2006) WoldeGabriel ± 0.05 ± –106.42168 4.42 0.02 del Rio basalt Cerros gm est. 36.08528 del Rio basalt Cerros 36.09611 del Rio basalt Cerros –106.42972 obs 36.02389 del Rio basalt Cerros 36.20471 –106.40361 del Rio basalt Cerros del Rio basalt Cerros –106.47444 –106.30115 35.88200 8.71 san 35.88200 –106.21720 35.87540 pl 35.91250 2.09 ± san –106.21720 gm 35.91170 0.10 –106.21190 –106.22340 gm 35.87990 ± –106.23310 gm 2.21 0.02 pl –106.15510 gm 2.9 35.75500 hd 1.18 ± 2.86 2.10 35.75500 pl 0.01 –106.25833 35.75667 9.30 35.75667 san ± 8.86 –106.25833 ± ± 35.77917 0.04 –106.25667 35.75667 0.7 2.22 8.49 0.05 –106.25667 8.78 ± 4.76 gm ± –106.24217 –106.25667 0.20 1.19 gm 0.05 4.17 ± 2.92 gm ± 5.31 ± gm 0.24 9.36 0.09 8.91 0.13 ± gm gm ± 2.68 0.29 8.54 8.83 4.79 2.66 0.02 2.68 4.20 ± 3.03 5.34 ± 0.08 3.04 2.9 ± 0.1 ± 0.2 2.70 0.2 ± ± 2.68 0.5 1.6 2.70 3.05 3.06 2.92 number Sample name Reference Unit Bearhead intrusions, ﬂows, and fall deposits ( domes Northern Tschicoma domes Northeastern Tschicoma El Rechuelos Rhyolite El Alto Basalt Pajarito Plateau surface and drill-hole samples

Geosphere, June 2013 623

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. ) 2 0 8 9 6 0 7 3 2 7 7 7 2 9 6 7 6 0 7 1 1 2 9 7 0 4 6 4 7 6 2 0 6 2 6 1 0 0 5 2 9 1 8 6 5 8 4 3 0 5 3 6 7 5 5 0 2 5 7 5 4 4 2 5 5 0 4 7 7 5 5 8 5 5 4 6 5 2 4 4 3 5 5 9 9 6 2 4 ...... 2 2 2 2 3 2 3 2 9 3 2 2 9 2 2 2 2 2 2 2 3 2 2 2 2 2 2 2 8 2 2 2 5 3 2 2 4 2 3 8 2 4 2 1 1 1 1 1 1 1 Adjusted age (Ma) continued ( 2 6 6 8 4 2 6 2 9 7 2 3 2 8 6 4 2 6 8 4 3 2 2 3 9 8 2 8 9 5 6 8 0 2 4 3 3 1 7 4 6 3 8 5 4 2 6 2 σ 0 0 1 0 0 0 2 5 0 0 0 0 4 0 3 2 2 0 2 0 0 2 1 0 0 0 1 0 0 1 1 2 3 2 0 0 0 0 4 0 5 0 0 0 8 5 2 7 ...... 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± 0 1 8 8 5 2 9 0 7 6 5 6 1 9 6 9 0 7 3 5 0 8 9 1 2 4 5 9 0 3 0 7 8 4 9 3 9 6 8 0 9 5 7 9 4 5 5 7 8 4 2 6 5 0 3 5 1 7 5 4 4 9 5 4 4 4 5 5 7 7 8 1 5 5 4 7 5 5 4 5 4 5 4 3 9 8 3 3 3 1 5 2 ...... 2 3 2 2 2 3 9 2 2 2 8 2 2 2 3 2 2 2 2 2 2 2 2 5 2 2 2 2 8 3 2 2 2 2 2 2 2 2 2 2 2 3 2 8 4 4 1 3 1 1 1 1 1 1 Age (Ma) ± 2 Reported n r r r r r r r m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m a w w w w w w w g g g g g g g g g g g g g g g g g g g g g g g g g g g g g g g g g g g g g g g g s ) 0 3 0 7 7 3 3 7 8 3 3 7 7 3 7 7 7 7 7 7 3 7 0 3 0 9 0 3 8 1 5 4 8 3 8 0 3 8 1 3 9 9 0 5 1 4 4 4 6 4 7 8 0 3 4 1 7 0 1 4 3 5 1 3 1 0 1 4 1 3 8 6 5 7 0 3 1 5 3 8 8 8 1 9 4 7 8 4 2 0 0 7 8 0 0 4 8 1 9 7 5 7 4 0 8 0 7 5 9 8 9 5 5 9 5 7 0 3 6 2 4 6 9 3 6 8 3 7 4 1 1 7 6 9 7 3 4 4 6 6 0 6 0 7 1 6 1 0 0 9 0 6 1 6 4 1 5 1 0 6 3 1 2 2 2 1 2 2 2 2 2 1 3 1 2 2 2 2 2 2 2 2 3 1 2 2 1 2 2 1 3 2 2 3 2 2 2 2 2 2 2 1 3 2 2 ...... 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 continued 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – 0 0 0 6 3 8 9 0 9 2 0 7 3 5 2 9 0 0 3 9 3 3 8 0 7 5 0 5 2 2 8 8 6 7 4 0 5 5 8 9 5 6 6 2 6 1 9 7 7 8 9 2 2 2 0 5 8 0 8 5 2 1 6 9 9 4 8 9 0 6 0 9 2 8 2 0 4 0 8 0 0 9 3 3 8 8 2 4 8 0 0 2 0 4 7 8 6 5 8 0 4 1 4 8 0 8 0 0 8 2 8 2 5 0 1 3 4 5 1 0 4 7 1 0 8 2 5 5 5 6 8 6 7 7 6 5 7 6 5 8 1 7 5 7 7 1 2 8 6 7 6 4 7 7 7 7 8 7 0 5 — — 8 8 8 7 9 7 8 8 8 8 8 8 8 8 7 7 7 8 8 7 8 7 7 8 8 8 8 8 8 9 8 8 8 8 8 9 8 8 8 7 8 8 8 8 8 ...... 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 Latitude 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 (WGS83) Longitude Mineral Ar RESULTS—JEMEZ MOUNTAINS ( MOUNTAINS Ar RESULTS—JEMEZ e 39 k i , d 6 6 5 5 Ar/ ) e e e t t t t t t t t t t t t t t 1 1 5 5 l l l l l l l l l l l i 40 i i o - - - - a a a a a a a a a a a t c c c e s i A A A A e t t t t t t s s s s s s s s s s s k a a a l l l l l l n t n i i T T T T a a a a a a a a a a a d d d e a a a a a a r o 6 d , , , , t U f b b b b b b b b b b b i s s s s s s a 1 t i t t t t t t t t t t t t t t t t n n n n n n n l e y y y y y y y y y y y l l l l l l l l l l l l l l l l - t t t a a a a a a e a l l l o o o o o o o a d h h h h h h h h h h h a a a a a a a a a a a a a a a a i i i i i i i A b b b b b b l g a a a t t t t t t t s I c c c c c c c c c c c s s w s s s s s s s s s s s s s s T u s s s a a a a a a a a n n n n n n a a a a a a a a a a a a a a a a a a a a a a a a a a a a , n r r r r r r r r r r r a a a b o o o o o o b b t t h b t b t t b t b t b b b t t b m t t b b b b b b i i i i i i n m m m m m m m a b b b t t t t t t r r r r r r r o n o o o o o o o o o o o o o o o o o o o o o o o o o o o o o S i a a a a a a o o o o o o o i i i i i i i i i i i i i i i i i i i i i i i i i i i i i n n n t ( o F F F F F F F o o o a R R R R R R R R R R R R R R R R R R R R R R R R R R R R R m m m m m m y a r r r r r r y y y l l l l l l l l l l l l l l l l l l l l l l l l l l l l l n a a a a a a a s m o o o o o o n n n e e e e e e e e e e e e e e e e e e e e e e e e e e e e e r a e F F F F F F m m m m m m m a a a d d d d d d d d d d d d d d d d d d d d d d d d d d d d d o C o o o o o o o M C C F C o o o o o o s s s s s s s s s s s s s s s s s s s s s s s s s s s s s c c c c c c c t t t t t t a i i i i i i i k o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o e o a a a a a a z r r r r r r r r r r r r r r r r r r r r r r r r r r r r r h h h h h h h c i r r r r r r r r r r r r r r r r r r r r r r r r r r r r r y l y y y b b b b b b c c c c c c c a e e e e e e e e e e e e e e e e e e e e e e e e e e e e e a l a u a a o o o o o o s s s s s s s T T T C C C B C C C C L C L C C B C C C L C C T C C C C C C C L C B T C L B C L C C P T C P T C ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) 6 6 6 6 1 6 6 6 1 6 6 6 6 1 6 6 6 6 6 6 1 6 6 6 1 1 6 1 1 6 6 6 6 6 1 6 6 6 6 1 6 6 6 0 9 9 0 0 0 0 9 0 0 0 9 9 0 9 0 0 9 0 9 9 9 9 9 0 9 9 9 0 9 0 0 9 9 9 0 0 0 0 9 0 0 0 0 9 9 9 0 0 0 0 9 0 9 0 0 0 0 9 9 9 0 9 0 9 9 9 0 9 0 9 9 0 0 9 9 0 0 9 0 9 0 0 9 0 0 2 1 1 2 2 2 2 1 2 1 1 2 2 2 2 2 2 1 1 2 1 1 2 1 1 1 2 1 2 1 2 2 1 1 2 1 1 2 2 1 2 1 2 e ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ) ) ) ) ) c ...... 7 7 7 7 7 l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l n 0 0 0 0 0 a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a ) e 0 0 0 0 0 r t t t t t t t t t t t t t t t t t t t t t t t t t t t t t t t t t t t t t t t t t t t 2 2 2 2 2 e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e TABLE 2. SUMMARY OF PREVIOUS PUBLISHED 2. SUMMARY TABLE ( ( ( ( ( f l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l . . . . . e l l l l l e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i R a a a a a r r r r r r r r r r r r r r r r r r r r r r r r r r r r r r r r r r r r r r r r r r r t t t t t b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b e e e e e a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a continued n n n n n G G G G G G G G G G G G G G G G G G G G G G G G G G G G G G G G G G G G G G G G G G G o o o o o e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e t t t t t d d d d d d d d d d d d d d d d d d d d d d d d d d d d d d d d d d d d d d d d d d d x x x x x l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o r r r r r W B B W W W W W W B W W W W W W W W W W W W W W W W B W W W W W W W W W W W W W W W W W W W B W 7 5 9 8 7 - 9 0 0 0 - 3 9 0 e 0 0 0 0 9 0 1 T M 2 B M M m 2 9 4 6 1 8 T T H 1 7 2 2 2 1 1 / 0 0 0 - c - / 0 T T T T 0 0 6 b 0 a m H H 9 6 b a M M C 5 9 0 0 4 3 1 T 9 0 0 1 2 2 8 9 6 M - 1 3 3 2 0 2 7 2 8 1 8 3 7 1 0 0 4 2 7 0 a H 5 0 9 - 7 6 5 4 ------5 6 6 9 5 1 1 4 5 2 5 1 2 J 8 5 2 2 2 4 9 9 2 ; 2 1 2 2 2 2 2 2 8 8 n - - I ; a 2 4 0 4 2 4 1 0 0 0 0 - 0 0 4 ; ; / 7 9 1 1 4 4 ) - - - - 1 - - - - 1 1 1 9 1 9 2 1 2 2 1 2 2 5 I - 3 - - - 3 1 0 - 1 1 9 1 0 1 3 8 0 1 1 1 R 5 - - - e - 3 3 3 3 ------( - - 5 3 - 3 3 - l 1 4 4 - - - 8 5 5 9 1 4 1 5 8 9 6 6 9 2 3 5 4 1 4 3 F 5 9 9 9 9 4 1 4 1 1 1 3 5 6 8 9 5 9 9 5 p - ; 5 1 8 8 - B T T 8 - 2 H H 1 N N 1 M M 8 N 1 T 8 T T T T T 5 5 4 R R R 8 8 N N N N - 4 5 8 M N N - 3 N N 6 - E N N m B B N 5 O O D P P D 5 N 4 2 D T N 9 N O N O O O O O V P D D D D G G G 1 M M M N D D a D D - R D D D S S D - T M D - F M D O D D D P P P D S R V P V O P C d d C C r e b 8 7 8 7 9 8 2 6 4 0 3 3 2 3 4 2 8 9 5 0 8 7 5 3 2 4 5 8 7 1 1 1 1 4 6 4 5 7 6 5 0 1 0 6 2 6 9 3 1 7 0 9 8 0 8 8 7 9 1 9 1 7 0 7 6 6 6 0 8 8 6 7 1 1 0 7 9 7 8 9 9 8 8 6 1 0 1 2 7 7 0 1 7 8 1 6 ID m 2 1 1 2 1 1 2 1 1 1 2 1 2 1 1 1 2 1 2 1 1 1 1 2 1 1 1 1 1 1 1 1 1 1 2 2 2 2 1 2 2 2 1 1 1 1 2 2 u P P P P P P P P P P P197 GR1-1440 et al. (2006) WoldeGabriel Lobato Formation basaltic andesite 35.91850 –106.23433 wr 12.90 ± 0.22 12.98 P P220 R-8; 95-95.1 Broxton et al. (2007)Alamos Canyon Puye Formation, Los 35.87167 –106.24697 gm 1.99 ± 0.05 2.00 P P P P199P200 GR4-590 GR4-1090 et al. (2006) WoldeGabriel et al. (2006) WoldeGabriel Lobato Formation basaltic andesite Lobato Formation basaltic andesite 35.91167 35.91167 –106.22600 –106.22600 wr wr 11.55 12.57 ± ± 0.09 0.16 11.62 12.65 P195P196 GR1-840 GR1-1170 et al. (2006) WoldeGabriel et al. (2006) WoldeGabriel Lobato Formation basaltic andesite Lobato Formation basaltic andesite 35.91850 35.91850 –106.23433 –106.23433 wr wr 12.17 12.67 ± ± 0.1 0.08 12.24 12.75 P P P219 R-22; 628-638 Broxton et al. (2007) Formation, Pajarito Canyon Tschicoma 35.82922 –106.23286 gm 2.42 ± 0.12 2.43 P P P P P P P P P P P P202 GR3-890 et al. (2006) WoldeGabriel Lobato Formation Basaltic andesite 35.91017 –106.21817 wr 12.39 ± 0.12 12.46 P P P P189 OT1-90-100 et al. (2006) WoldeGabriel Cerros del Rio basaltic andesite 35.87083 –106.21917 gm 2.77 ± 0.03 2.79 P P P P P204 GR2-1070 et al. (2006) WoldeGabriel Lobato Formation trachybasalt 35.90900 –106.21033 wr 12.78 ± 0.07 12.86 P P P P P P P P P P P P P P n Drill-hole samples Pajarito Plateau surface and drill-hole samples (

624 Geosphere, June 2013

DISTRIBUTION OF VOLCANIC Fig. 2) intrudes a north-striking fault splay east 9 8 2 9 9 3 4 5 8 4 6 7 5 6 ...... 2 3 2 2 2 2 2 CENTERS THROUGH TIME IN of the main Cañones fault zone, cutting the Adjusted age (Ma) THE JMVF upper Oligocene to lower Miocene Abiquiu 6 3 2 8 2 4 3 5 Formation (Kelley et al., 2005b). Dated at σ 0 0 0 0 0 2 0 1 ...... 0 0 0 0 0 0 0 0 Late Oligocene to Early Miocene Maﬁ c 19.72 ± 0.33 Ma (2, Table 1), this dike is not ± ± ± ± ± ± ± ± Activity (25–15 Ma) deformed by subsequent faulting. Related dikes near Abiquiu ~3.2 km north and 4 km east, Late Oligocene to early Miocene maﬁ c lavas respectively, of the Arroyo de Frijoles dike were 7 7 6 1 7 6 2 1 6 8 5 4 5 4 7 6 ...... 2 3 2 2 2 2 2 2 and intrusions in the southeastern and north- dated by Maldonado and Miggins (2007); these Age (Ma) ± 2 Reported western Jemez Mountains are associated with authors determined that a north-striking dike in a widespread, long-lived record of sporadic, nearby Red Wash Canyon (RWC, Fig. 2; P2, alkaline to tholeiitic small-volume magma- Table 2) has a 40Ar/39Ar age of 19.63 ± 0.40 Ma i m m m m m m m tism that occurred during early extension in the and the Cerrito de la Ventana (CdlV, Fig. 2; P1, b g g g g g g g Española Basin. Many of the lavas are primi- Table 2) dike near Abiquiu has a 40Ar/39Ar age tive, with up to 16% MgO, and are composi- of 19.22 ± 0.30 Ma. The similarity of age and )

9 tionally related; these lavas are interpreted to be phenocryst content implies a genetic relation- 5

7 from a common mantle source or set of sources ship among the three dike splays. Another early 5 5 — — — — — — .

6 (Gibson et al., 1993; Wolff et al., 2000, 2005). Miocene intrusion is exposed for ~1 km along continued 0 1

– The most well-known outcrops of these older the east side of Encino Point (EP, Fig. 2) within

h—no data available. lavas include three or four small-volume maﬁ c the Cañones fault zone (Fig. 3). Splays of the 6

9 lava ﬂ ows that are discontinuously exposed in Cañones fault zone cut this equigranular to por- 3 4 — — — — — — the southeastern JMVF east and southeast of phyritic intrusion, which has a sill-like geom- 5 . 5 Latitude 3

(WGS83) Longitude Mineral Boundary Peak in the footwall of the Pajarito etry. This intrusion was dated twice (3, Table 1) fault zone (Goff et al., 1990; Figs. 2 and 3). because the 40Ar/39Ar age results of 18.94 ± These ﬂ ows are intercalated with volcaniclas- 0.33–19.00 ± 0.35 Ma were unexpectedly old tic conglomeratic sandstone containing clasts in this area where 7.0–8.5 Ma ages prevail. The e

t derived from local and distal volcanic sources 60–90-m-thick intrusion is within the Chama– i c

a (Kelley et al., 2013). Typically, the maﬁ c lavas El Rito Member of the Tesuque Formation of D Ar RESULTS—JEMEZ MOUNTAINS ( MOUNTAINS Ar RESULTS—JEMEZ n are nephelinite to basanite that, in places, are the Santa Fe Group (Fig. 5; Lawrence et al., o 39 i t a

Ar/ deeply altered to a green color. Several attempts 2004). The Abiquiu area and Encino Point dikes m 40 r t i o have been made to determine the age of these and sills are likely related to middle Miocene n F U a ﬂ ows. Early efforts to date the basanite in volcanic centers of similar age (ca.14–26 Ma) m o c

i Medio Canyon (Fig. 2) resulted in K-Ar and in the northern Española Basin near El Rito and e t h i c s 40 39 t t t s l l l e t t Ar/ Ar ages of 16.5 ± 1.4 Ma and 15.44 ± Ojo Caliente (Fig. 3; Baldridge et al., 1980; l l T a a a d a a l s s s l n s s i a a a 0.30 Ma (Gardner et al., 1986; Justet, 2003; May, 1980, 1984; Manley and Mehnert, 1981; a a a H b b b b b c i n y y t t e e e l l P6, Table 2). More recently WoldeGabriel et al. Ekas et al., 1984; Gibson et al., 1993; Koning o h h n n n a a t i i i c c s s v v v n i i i a a l l l a a

e (2006) measured an age of 18.79 ± 0.64 Ma for et al., 2011). r r O O T B T B F O this same basanite (P3, Table 2). In addition, WoldeGabriel et al. (2006) determined 20.95 ± Middle to Late Miocene Activity (14–9 Ma)

) 40 39

7 0.63 Ma and 25.63 ± 0.87 Ma Ar/ Ar ages 0 0

2 on two basanites east of Boundary Peak ~2 km Small volumes of lava or tuff of maﬁ c to (

h north of the Medio Canyon locality (P4 and P5, dacitic to rhyolitic composition erupted from s o t n e Table 2). These basanites are the oldest ﬂ ows in three distinct areas in the Jemez Mountains I c c n ) ) ) ) ) ) M e 1 1 1 1 1 1 the immediate vicinity of the Jemez Mountains. between 14 and 9.7 Ma. First, 14–11 Ma maﬁ c r 0 0 0 0 0 0 d e TABLE 2. SUMMARY OF PREVIOUS PUBLISHED 2. SUMMARY TABLE 0 0 0 0 0 0 f n 2 2 2 2 2 2

e Modeling of geochemical data from this area lava ﬂ ows are preserved in the vicinity of Santa ) a ( ( ( ( ( ( 3 R ...... n l l l l l l 0 i

l suggests that the magma that generated these Clara Canyon and in drill holes on the Pajarito a a a a a a 0 r t t t t t t 2 e ( e e e e e e b

t lavas is chemically linked to <10 Ma basalts Plateau on the northeast side of the JMVF h h h h h h m e t t t t t t t i i i i i i a s in the main JMVF (Wolff et al., 2000, 2005). (Fig 2; Aldrich, 1986; Wolde Gabriel et al., h m m m m m m u S S S C S S S J Alternatively, the upper Oligocene to lower 2006). Second, a buried 11–13 Ma dacitic cen- Miocene mafi c fl ows in the southeastern JMVF ter may underlie younger volcanic rocks of may have come from eruptive centers in the the northeastern JMVF (Koning et al., 2007b). 0 0 e 3 6 5 southern and eastern Española Basin near La Westward increase in the thickness of ash beds 7 7 m 1 8 6 - 5 9 1 - - 6 a - 0 1 3 0 0 3 n Cienega and Santa Fe (Smith, 2004; Myers and in the Chamita Formation of the Santa Fe Group 8 2 6 4 5 D D 9 7 e 9 l 6 8 - S S T p T T N Smith, 2006). (Fig. 5) near Española, the distribution of dacitic C S S S S S L D m G C G a C C During this study, early Miocene mafi c intru- lag gravel beneath the ca. 9–10 Ma Lobato For- S S S S sive rocks were identifi ed west of the village mation, and tuffaceous volcaniclastic sediments of Abiquiu in the northern and northwestern below a 10.16 ± 0.06 Ma Lobato Formation gm—groundmass; san—sanidine ; obs—obsidian; pl—plagioclase; hd—hornblende; bi—biotite; wr—whole rock; est—no error report; das

r Jemez Mountains near the Cañones fault zone ﬂ ow in Santa Clara Canyon (P62, Wolde Gabriel e b 2 3 4 8 7 9 5 5 2 2 2 2 2 2 2 2 (Figs. 2 and 4). One dike and associated plug et al., 2006, 2007) all point to a now-buried ID m Note: 2 2 2 2 2 2 2 2 u 40 39 P P P P P P P P n Western Jemez Western Santa Ana Mesa on the west side of Arroyo de Frijoles (AdlF, dacitic center. Third, recent Ar/ Ar dating of

Geosphere, June 2013 625

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.

Ar data, this study 19.72 Age (Ma) 0.00–1.20 1.21–1.80 1.81–3.00 8.33 3.01–5.00 18.94 10.08 7.89 5.01–7.00 18.38 7.01–8.00 19 8.22 7.74 7.90 8.01–9.00 7.99 3.64 9.01–12.00 7.79 12.01–20.00 8.10 3.61 7.94 29.29 1.55 Ar data, published 3.34 Corrected Age (Ma) 8.11 3.76 7.42 2.87 0.00–1.20 8.75 3.36 1.21–1.80 7.36 1.66 1.81–3.00 9.73 3.01–5.00 6.51 3.26 4.14 5.01–7.00 8.17 3.21 7.01–8.00 7.81 2.09 3.66 9.57 8.01–9.00 5.34 4.49 3.37 9.01–12.00 7.68 7.79 4.46 12.01–26.00 7.09 10.45 9.80 7.7 7.27 7.42 7.8 7.34 1.61 7.66 7.61 0.78 7.78 4.81 0.77 4.21 0.91 2.95 1.59

9.46 4.01 1.23 9.50 8.98 3.50

1.24 9.00 4.36 2.01 8.26 8.99 1.25 8.99 3.44

1.4 8.66

7.20 1.68 8.53 1.59

7.38

9.45 6.48

9.22 6.51 9.37

9.43

9.58 10.94

9.47 9.54 9.49 9.11 Kilometers 9.39 9.8 9.79 0246810 9.45

Figure 4. Location of the dated samples in the Jemez Mountains color coded according to age, with warmer colors assigned to younger ages. Samples from this study are shown as circles and are labeled with the date on the map, tied to Table 1. The squares are previously dated samples reported in Table 2.

626 Geosphere, June 2013

TABLE 3. GEOCHEMICAL DATA FROM CERRO DE LA GARITA, THE TOLEDO EMBAYMENT, AND POLVADERA MESA Cerro de la Garita Toledo Polvadera Paliza Paliza Paliza Paliza Paliza Embayment Mesa La Grulla La Grulla Canyon Canyon Canyon Canyon Canyon Sample number F06-21 F06-22 F06-23 F06-24 F06-26 F06-27 F06-29 JG05-14 04CM-22 Date 14-07-08 14-07-08 14-07-08 14-07-08 14-07-08 14-07-08 14-07-08 14-07-08 20-07-05 Rock name Dacite Dacite Andesite Andesite Andesite Andesite Andesite Rhyolite Pumice Unnormalized major elements (wt%)

SiO2 66.22 62.93 60.45 61.29 57.35 60.20 63.16 74.63 TiO2 0.628 0.720 0.894 0.849 1.026 0.928 0.612 0.255 Al2O3 15.83 15.52 16.08 15.93 16.31 16.15 14.85 12.69 FeO* 3.48 4.14 5.25 5.07 6.07 4.92 3.44 1.55 MnO 0.049 0.073 0.103 0.090 0.094 0.079 0.071 0.025 MgO 0.74 2.23 2.81 2.90 3.47 2.97 1.59 0.24 CaO 3.46 4.24 5.39 5.07 5.76 4.92 3.96 0.83

Na2O 4.28 3.70 3.48 3.69 3.17 3.42 2.67 3.30 K2O 3.00 3.30 2.98 2.93 2.30 2.56 3.63 4.69 P2O5 0.202 0.281 0.323 0.286 0.346 0.371 0.224 0.046 Sum 97.90 97.15 97.75 98.11 95.91 96.51 94.21 98.25 ≥ SO3 ( ) 0.01 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Standard Normalized major elements (wt%) deviation

SiO2 67.64 64.78 61.84 62.47 59.80 62.37 67.05 75.96 SiO2 72.74 1.40 TiO2 0.641 0.741 0.915 0.866 1.070 0.962 0.650 0.259 TiO2 0.43 0.09 Al2O3 16.17 15.97 16.45 16.24 17.01 16.74 15.76 12.91 Al2O3 14.21 0.92 FeO* 3.56 4.26 5.37 5.16 6.33 5.10 3.66 1.57 FeO 1.91 0.37 MnO 0.050 0.075 0.105 0.092 0.098 0.082 0.076 0.026 MgO 0.50 0.13 MgO 0.76 2.30 2.88 2.96 3.62 3.07 1.69 0.25 MnO 0.05 0.03 CaO 3.54 4.37 5.51 5.17 6.01 5.10 4.20 0.85 CaO 1.88 0.43

Na2O 4.37 3.81 3.56 3.76 3.31 3.55 2.84 3.35 Na2O3.940.25 K2O 3.06 3.40 3.05 2.98 2.39 2.65 3.85 4.78 K2O3.840.38 P2O5 0.206 0.289 0.331 0.291 0.361 0.384 0.238 0.046 P2O5 0.08 0.05 Total 100.00 100.00 100.00 100.00 100.00 100.00 100.00 100.00 SO2 0.08 0.03 F 0.08 0.07 Cl 0.26 0.15 Total 100 Unnormalized trace elements (ppm) Ni 7 22 26 31 35 32 11 2 Cr 19 22 35 37 40 54 16 10 Sc 8 11 14 14 17 13 9 3 V 55 86 116 106 130 115 63 18 Ba 1562 1177 1120 1078 1017 1363 1090 406 Rb 61 69 56 59 59 134 108 153 Sr 577 653 675 661 715 721 818 110 Zr 222 191 190 190 181 200 231 121 Y 20 19 22 21 24 21 22 17 Nb 12.5 19.4 18.9 19.1 19.4 21.7 21.1 36.6 (continued)

Canovas Canyon rhyolites in the southwest- Southern Jemez Mountains dated using both K-Ar and 40Ar/39Ar methods, ern Jemez Mountains suggests activity began The oldest succession of mafi c fl ows in the and the results vary over a fairly wide range there at ca. 12 Ma (Padmore and Spell, 2008). southwestern Jemez Mountains is exposed on of 9.02 ± 0.78 to 13.2 ± 1.2 Ma (Luedke and Although a previous K-Ar date for Canovas Chamisa Mesa and on Borrego Mesa (Fig. 2). Smith, 1978; Gardner et al., 1986; Chamber- Canyon rhyolite lava in Sanchez Canyon (Fig. 2) The basalt of Chamisa Mesa (Bailey et al., lin et al., 1999; Justet, 2003; Chamberlin and suggested ca. 12 Ma activity in the southeastern 1969) consists of sparsely porphyritic Paliza McIntosh, 2007; e.g., P7–P9, Table 2). Cham- JMVF, more recent 40Ar/39Ar dating on the same Canyon Formation basalt fl ows with a distinc- berlin and McIntosh (2007) determined an aver- outcrop yielded a 9.69 ± 0.12 Ma age (P15, tive ophitic texture. The fl ows overlie the Mio- age 40Ar/39Ar age of 9.9 ± 0.9 Ma for the basalt WoldeGabriel et al., 2006). cene eolian and fl uvial Chamisa Mesa Member of Chamisa Mesa. The basalt of Chamisa Mesa Following 14–9.7 Ma localized eruptions in of the Zia Formation or a conglomeratic sand- samples analyzed during this study are from the northeastern and southwestern quadrants of stone with Proterozoic pebbles that is likely the middle of a stack of fl ows on Borrego Mesa the Jemez Mountains, more voluminous erup- correlative to Cerro Conejos Formation of the sitting above Zia Formation near the Jose fault tions in the JMVF started at ca. 10 Ma. Early Santa Fe Group (Fig. 5). The basalt of Chamisa zone (4, Table 1; Fig. 4), and from the lowest activity was focused in the southwestern and Mesa consists of extensive fl ows that are pres- fl ow in the mesa escarpment south of the Jose southern Jemez Mountains between Borrego ent as far east as Borrego Dome, as far south fault (5, Table 1). The 40Ar/39Ar ages of these Mesa and Boundary Peak (Paliza Canyon For- as the south end of Borrego Mesa, and as far two samples are 9.45 ± 0.22 Ma and 9.39 ± mation and Canovas Canyon Rhyolite) and in north as Paliza Canyon (Fig. 2). A fl ow that is 0.31 Ma, respectively. A basalt fl ow in Paliza the northeastern Jemez Mountains on Lobato texturally similar to the basalt of Chamisa Mesa Canyon that probably correlates with the basalt Mesa (Lobato Formation; Figs. 2 and 5). The sits on Abiquiu Formation in Church Canyon of Chamisa Mesa, dated by K/Ar at 13.2 ± next sections discuss the 9–10 Ma volcanism northeast of Jemez Springs (Kelley et al., 2003; 1.2 (Gardner et al., 1986), gave a groundmass in detail. Fig. 2). The basalt of Chamisa Mesa has been 40Ar/39Ar age of 9.43 ± 0.14 Ma (6, Table 1).

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TABLE 3. GEOCHEMICAL DATA FROM CERRO DE LA GARITA, THE TOLEDO EMBAYMENT, AND POLVADERA MESA (continued) Cerro de la Garita Toledo Paliza Paliza Paliza Paliza Paliza Embayment La Grulla La Grulla Canyon Canyon Canyon Canyon Canyon Sample number F06-21 F06-22 F06-23 F06-24 F06-26 F06-27 F06-29 JG05-14 Date 14-07-08 14-07-08 14-07-08 14-07-08 14-07-08 14-07-08 14-07-08 14-07-08 Rock name Dacite Dacite Andesite Andesite Andesite Andesite Andesite Rhyolite Unnormalized trace elements (ppm) (continued) Ga 18 16 18 16 17 17 16 15 Cu 15 7 23 19 35 9 14 2 Zn 57 56 62 61 71 122 54 23 Pb 16 16 15 14 10 14 18 20 La 52 40 40 38 39 39 41 40 Ce 86 71 66 68 66 72 81 58 Th 6 7 5 5 5 5 8 25 Nd 36 29 30 29 30 32 31 19 U 2 4 4 2 3 4 4 10 Sum trace 2830 2515 2534 2466 2510 2987 2654 1087 (%) 0.28 0.25 0.25 0.25 0.25 0.30 0.27 0.11 Sum (m + tr) 98.18 97.40 98.00 98.35 96.16 96.81 94.47 98.36 Major and 98.23 97.45 98.05 98.40 96.21 96.86 94.52 98.38 Trace oxides NiO 8.6 28.5 33.0 40.0 44.5 41.1 13.9 3.1

Cr2O3 27.0 32.0 50.4 53.6 58.0 78.8 22.7 15.2 Sc2O3 12.6 16.4 21.0 20.9 25.5 20.6 13.2 3.8 V2O3 81.1 126.7 170.2 155.8 190.5 169.0 92.7 26.9 BaO 1744.3 1314.5 1250.6 1203.9 1135.1 1521.2 1216.5 452.7

Rb2O 66.7 75.1 61.1 64.1 64.6 146.1 117.7 166.8 SrO 682.8 771.9 798.7 781.7 845.3 852.8 967.8 129.6

ZrO2 299.5 258.5 256.0 256.8 244.5 269.6 311.9 163.4 Y2O3 24.9 23.9 28.3 26.3 30.6 26.8 28.3 21.5 Nb2O5 17.9 27.8 27.0 27.3 27.8 31.0 30.2 52.4 Ga2O3 23.7 21.4 23.9 21.9 22.2 22.2 22.0 19.8 CuO 18.9 9.0 28.9 23.3 43.6 11.5 17.3 2.8 ZnO 71.6 70.0 77.0 76.0 88.3 153.2 67.6 28.8 PbO 16.7 17.0 15.6 14.8 10.9 14.7 18.9 21.2

La2O3 60.9 47.3 47.3 44.1 45.2 45.6 48.0 47.3 CeO2 106.1 87.6 80.8 83.5 81.1 88.1 99.2 71.2 ThO2 6.1 7.4 5.7 5.5 5.2 5.7 9.3 27.5 Nd2O3 41.8 34.1 34.9 34.1 35.5 37.3 36.5 21.9 U2O3 2.3 4.0 4.4 1.9 3.1 3.9 4.0 10.6 Bi2O5 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 Cs2O 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 As2O5 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 W2O3 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 Sum trace 3313 2973 3015 2935 3001 3539 3138 1286 (%) 0.33 0.30 0.30 0.29 0.30 0.35 0.31 0.13 Note: Major elements are normalized on a volatile-free basis, with total Fe expressed as FeO. “R” denotes a duplicate bead made from the same rock powder.

Another Paliza Canyon Formation basalt fl ow 9.37 ± 0.12 Ma; 6 and 7, Table 1) and the ages Peak is another signifi cant Canovas Canyon cen- exposed on the east side of San Juan Canyon of the dated basalts on Borrego Mesa. ter. Several Canovas Canyon rhyolite domes in just southwest of Cerro del Pino that overlies A Canovas Canyon plug intruding Zia Forma- the southern Jemez Mountains have been dated the Abiquiu Formation (CdP, Fig. 2) gave a tion and an associated fl ow of dacitic to rhyolitic at 12.4–8.2 Ma by Padmore and Spell (2008), groundmass age of 9.45 ± 0.07 Ma (8, Table 1). composition form a prominent knob east of the with the ages clustering in the 9.9 to 9.2 Ma Canovas Canyon rhyolitic tuffs and inter- village of Ponderosa (PD, Fig. 2). The dominant range. Justet (2003) determined an age of 9.36 calated volcaniclastic and eolian sediment gen- lithology is a crystal-rich, biotite-hornblende ± 0.05 Ma for Borrego Dome (P14, Table 2). We erally lie above the basalt of Chamisa Mesa; dacite with no quartz that grades into crystal- determined that a rhyolite fl ow from the Bear however, one Canovas Canyon ash-fall bed poor rhyolite with small quartz phenocrysts. A Springs Peak center exposed in Canovas Canyon does crop out below basalt sample 4 (Table 1) chilled glassy margin is present at the base of the has a biotite age of 9.79 ± 0.09 Ma (12, Table 1), on Borrego Mesa. One of the tuffs above the rhyolite fl ow on the east side of the knob. Two compared to 8.70 ± 0.35 Ma for a fl ow on the basalt of Chamisa Mesa, an ignimbrite with 40Ar/39Ar ages of 9.49 ± 0.18 and 9.47 ± 0.13 Ma northwest side of the Bear Springs Peak center ~10% lithic fragments of fl ow-banded rhyolite were determined for the intrusion (10b, Table 1) (P13, Table 2) and 8.05 ± 0.60 Ma for a fl ow on and obsidian, is similar to tuffs between basalt and glassy margin (10a, Table 1), respectively. the southeast side of the peak (P19) determined fl ows in Paliza Canyon (9, Table 1), in upper The locus of felsic Canovas Canyon eruptive by Justet (2003). A thick, crystal-poor rhyolite Peralta Canyon, and beneath Boundary Peak activity in the southeastern Jemez Mountains fl ow from a center west of Tres Cerros is 9.54 ± (Gardner et al., 1986; Goff et al., 1990; Goff is located at Bear Springs Peak and in the area 0.16 Ma (13, Table 1). et al., 2005a). The tuff in Paliza Canyon yielded south and west of Tres Cerros (TC, Fig. 2). A The Canovas Canyon Rhyolite on Borrego a hornblende 40Ar/39Ar age of 9.22 ± 0.36 Ma (9, dacite vent cluster that trends SW-NE is located Mesa is overlain by an olivine basalt in the Table 1), within error of the ages of the basalt near Cerrito Yelo (Fig. 2; Kempter et al., 2003). Paliza Canyon Formation that contains up to fl ows just below and above it (9.43 ± 0.14 and Borrego Dome to the southwest of Bear Springs 6% olivine altered to iddingsite. The basalt has

628 Geosphere, June 2013

Tewa Keres Group Group Puye Fm. Puye Lobato Fm. e–Jemez lavas under wa Group wa Group old alluvium volcaniclastic deposits and Pajarito Plateau El Alto Basalt

Chama El Rito Mbr.

Hernandez Mbr.

Ojo Caliente Ss. Mbr. El Rechuelos Rhyolite Chamita Fm. Chamita Fm. Tesuque Tschicoma Fm. Tschicoma

Otowi Member of the Bandelier Tuff Otowi Member of the Bandelier Santa Fe Group Fe Santa

and mafic lavas mafic and older basanite older

volcaniclastic deposits

monzonite Bland Cochiti Fm. Galisteo Fm. Chamita Tesuque Formation Formation

El Cajete Pyroclastic Bed Santa Fe Group Fe Santa Cerros del Rio lavas Paliza Canyon Fm. Bearhead Rhyolite - Peralta Tuff Bearhead Rhyolite - Peralta Valles Rhyolite Valles Tschicoma Fm. Tschicoma Abiquiu Fm. Chamita Formation Tesuque Formation Tesuque

Paliza Canyon Fm.

Santa Fe Group Fe Santa

Rhyolite

Canyon

Canovas Canovas

Fm.

Canyon

Paliza

deposits clastic

Valles Rhyolite Valles volcani- basalt of Chamisa Mesa Piedra Parada Mbr. East Fork Member, Chamisa Mesa Mbr. Tschicoma Fm. Tschicoma Abiquiu Fm. Galisteo Fm. Cañada Pilares Mbr.?

Tshirege Member, Bandelier Tuff Bandelier Member, Tshirege

La Cueva Member, Bandelier Tuff Bandelier La Cueva Member, Zia Fm. Zia Cerro Conejo Fm. Conejo Cerro

Gilman Conglomerate debris avalanche of Virgin Mesa debris avalanche of Virgin Group Fe Santa eld (JMVF) lavas, and the dashed red line illustrates the possible temporal range of these lavas. The unlabeled areas The unlabeled areas line illustrates the possible temporal range of these lavas. eld (JMVF) lavas, and the dashed red mafic intrusives unnamed fluvial unit El Rito Fm. Abiquiu Fm. Pedernal chert

La Grulla Plateau Formation Chama El Rito Mbr.

Hernandez Mbr.

Ojo Caliente Ss. Mbr. Cerro Toledo Formation Cerro Toledo Chamita Fm. Chamita NW Jemez Mtns. SW Jemez Mtns. Caldera Valles SE Jemez Mtns.Fm. NE Jemez Mtns. Tesuque

Ritito Conglomerate Ritito Conglomerate Figure 5. Stratigraphy of the Cenozoic units in the Jemez Mountains. The units highlighted in orange and labeled in blue are Te The units highlighted in orange and labeled blue are 5. Stratigraphy of the Cenozoic units in Jemez Mountains. Figure pr labels are The units with the red volcanic rocks. Group Keres et al., 2010), and those in purple are (Gardner volcanic rocks Mountain volcanic ﬁ erosion. intervals of no deposition or represent Santa Fe Group Fe Santa

Miocene Oligocene Eocene Pliocene Pleistocene

0 5 10 15 20 25 30 35 Age (Ma) Age

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a distinctive red speckled appearance on weath- sive hydrothermal alteration, particularly during mined ages of 8.82 ± 0.19–10.59 ± 0.10 Ma for ered surfaces and is aerially extensive, cover- emplacement of 6.5–7.2 Ma Bearhead Rhyolite, Lobato Formation basalts and dacites (P52–P57, ing an area from Church Canyon near Jemez have affected most of the volcanic rocks in this Table 2). Outcrops of basalt fl ows in Arroyo de Springs to Bodega Butte on Zia Pueblo (Fig. 2). part of the Jemez Mountains (WoldeGabriel and los Frijoles (23, Table 1; 10.08 ± 0.16 Ma) and This unit likely originated from a north-trending Goff, 1989; Goff et al., 2005b). Despite the fact in the vicinity of Abiquiu (P58, Table 2; 9.51 ± line of vents on the west fl ank of Bear Springs that the monzonite is challenging to date, fi eld 0.21 Ma; Maldonado and Miggins, 2007) mark Peak (Kempter et al., 2003). The olivine basalt relationships clearly demonstrate that the stock the northwestern and northern extent of the also caps a series of buttes and small mesas to is younger than older successions in the Paliza Lobato Formation. WoldeGabriel et al. (2006) the south and was informally named the basalt Canyon Formation (Goff et al., 2005b). Basalt, assign the less voluminous older (11–14 Ma) of Bodega Butte by Chamberlin and McIntosh trachyandesite, and volcaniclastic rocks (oldest basaltic fl ows interbedded with Chama–El Rito (2007). Chamberlin and McIntosh (2007) deter- to youngest) that belong to the Paliza Canyon Formation exposed in Santa Clara Canyon to the mined an average age of 9.14 ± 0.12 Ma from Formation are intruded by monzonite and quartz Lobato Formation based on geochemical simi- four samples of the basalt of Bodega Butte col- monzonite of the Bland stock in Colle Canyon larities (Aldrich and Dethier, 1990). lected on the Loma Creston quadrangle (P41– (Fig. 2; Goff et al., 2005b). Miocene basalts, andesites, and dacites that P44, Table 2). The groundmass 40Ar/39Ar date were erupted between 9.5 and 13.2 Ma are pres- from a sample of olivine basalt collected for this Northeastern Jemez Mountains ent in the subsurface and in canyon bottoms of study at the confl uence of Hondo and West Fork The oldest voluminous lavas erupted in the the northern Pajarito Plateau. A dacite (Samuels Canyons is 9.11 ± 0.13 Ma (14, Table 1). A stack northeastern Jemez Mountains belong to et al., 2007) outcrop located in the bottom of of at least four 1–2-m-thick, south-southwest– the Lobato Formation, which is well exposed Guaje Canyon has a groundmass age of 9.46 ± dipping trachyandesite and trachybasalt fl ows on Lobato Mesa. Eruptions in the northeastern 0.07 Ma (24, Table 1), and an 11.25 ± 0.13 Ma intercalated with volcaniclastic sediment and Jemez Mountains were primarily basaltic with (P66, Table 2) andesite is exposed at Pine rhyolitic tephra are exposed in Hondo Canyon minor trachyandesite and dacite (Bailey et al., Springs in Garcia Canyon (WoldeGabriel et al., below the basalt of Bodega Butte. The oldest 1969; Goff et al., 1989; Justet, 2003; Wolff et al., 2006). The Guaje Canyon exposure can be tied lava in this stack is 9.58 ± 0.08 Ma (15, Table 1), 2005), in contrast to the broad spectrum of felsic temporally and chemically to the Lobato Forma- and a wide E-striking Canovas Canyon Rhyolite to mafi c eruptions that occurred during the same tion, but the affi nity of the Pine Springs fl ow is intrusion cuts the basal part of this section. time frame in the southern Jemez Mountains. less certain. WoldeGabriel et al. (2006) note that Most of the 9–10 Ma volcanic rocks in the The 9–10 Ma volcanic deposits in the south- the 11.62 ± 0.09 Ma to 13.30 ± 0.22 Ma basalt southern Jemez Mountains are basalt, basal- western JMVF contain signifi cant amounts and basaltic andesite fl ows encountered in drill tic trachyandesite, andesite, trachyandesite, or of volcaniclastic sediments interbedded with holes in Guaje Canyon (P195–P204, Table 2; rhyolite in composition (Rowe et al., 2007), but the lavas, whereas the Lobato Formation con- Fig. 2) on the Pajarito Plateau are chemically dis- units with dacitic compositions also erupted dur- tains very little sediment. The few <1-m-thick tinct from Lobato Formation mafi c fl ows. ing this time frame, especially in upper La Jara deposits intercalated with the Lobato Forma- Canyon (Kempter et al., 2003). Justet (2003) tion are hydromagmatic or eolian in origin. The Late Miocene Activity (9–7 Ma) determined 40Ar/39Ar ages of 8.96 ± 0.06 Ma Lobato basalts were erupted from broad shield and 9.16 ± 0.07 Ma (P20 and P30, Table 2) for volcanoes (Baldridge in Goff et al., 1989). Volcanic activity in the southern Jemez an aerially extensive Paliza Canyon Formation The dacite of the Lobato Formation is variably Mountains shifted toward the southeast between trachyandesite fl ow between Paliza Canyon crystal-rich porphyritic to fi ne-grained aphyric 9 and 7 Ma. In contrast, volcanic activity in the and Hondo Canyon that caps southwest-dip- lava. The crystal-rich dacite exposed along the northern Jemez Mountains shifted toward the ping Paliza Canyon Formation basalt fl ows Rio del Oso and on the north side of Los Cer- northwest during this same time frame. Ande- and intercalated volcaniclastic sediments. This ritos along Forest Road 144 (LCe, Fig. 2) con- sitic to dacitic composition lavas were erupted fl ow thickens dramatically on the downthrown tains plagioclase laths 1–2 cm across and quartz from multiple centers in the southern and cen- side of a north-striking fault on the NW side of phenocrysts, superfi cially resembling lavas of tral Jemez Mountains (Paliza Canyon Forma- Guacamalla Canyon (Fig. 2), indicating ca. 9 Ma the younger Tschicoma Formation (Bailey et al., tion) and from centers on the La Grulla Plateau motion on this particular fault (Kempter et al., 1969; Goff et al., 1989); however, the Rio del (lavas of Encino Point and La Grulla Plateau) 2003). A porphyritic biotite-hornblende dacite Oso fl ows are chemically and chronologically between 9 and 7 Ma. Miocene mafi c fl ows in that fl owed east from the Cerro del Pino cen- more similar to Lobato Formation (Rowe et al., the subsurface beneath the Pajarito Plateau ter (CdP, Fig. 2) has a 40Ar/39Ar age of 9.48 ± 2007; Kelley et al., 2007a). We determined a bio- between Bayo Canyon on the north to Ancho 0.22 Ma (P18, Table 2, Justet, 2003). tite fusion 40Ar/39Ar age of 10.45 ± 0.05 Ma (20, Canyon on the south (Fig. 2) range in age The Bland monzonite stock in the southern Table 1) for coarsely porphyritic dacite in the from 8.4 to 9.3 Ma, and a trachyandesite fl ow JMVF stock is notable because this stock is the Lobato Formation in Rio del Oso and a 9.80 ± in upper Los Alamos Canyon is 8.71 ± 0.1 Ma only exposure of a pluton that sourced early 0.15 Ma (19, Table 1) groundmass age for a (Broxton and Vaniman, 2005; WoldeGabriel JMVF lavas. The Bland stock, which is discern- dacite fl ow that emanated from Los Cerritos on et al., 2006; Broxton et al., 2007). able through a combination of structural uplift the southern end of the Lobato Mesa. Ground- in a horst block and erosion, was originally mass ages of 9.57 ± 0.07 Ma (21, Table 1) and Southern and Central Jemez Mountains assigned an Eocene age (Smith et al., 1970). 9.73 ± 0.21 Ma (22, Table 1) for basalt fl ows The younger porphyritic to fi ne-grained Stein (1983) later determined a K-Ar age of and dikes in the vicinity of Rio del Oso confi rm trachy andesites and dacites of the Paliza Can- 11.3 ± 0.3 Ma from the monzonite; however, earlier observations that the bulk of the Lobato yon Formation in the southern Jemez Mountains subsequent attempts to date the intrusive using Formation erupted during a short time interval were not extensively sampled during this study K-Ar and 40Ar/39Ar methods have yielded com- between 9.2 ± 0.2 and 10.8 ± 0.3 Ma (Gardner, because these rocks have been the focus of pre- plex results. Multiple intrusive events and perva- 1985; Goff et al., 1989). Justet (2003) deter- vious work (Gardner, 1985; Gardner et al., 1986;

630 Geosphere, June 2013

Goff et al., 1990; Justet, 2003). Justet (2003) cut into the older fl ows. This paleovalley, which an andesite fl ow overlying the south side of the sampled the extensive fl ows of black porphyritic roughly parallels modern San Antonio Creek, dome. Thus, the Encino Point volcanic cen- trachyandesite along the crests of Cerro Pelado has been backfi lled by lava and tuff and sub- ter had at least two episodes of activity—one and Peralta Ridge that were probably vented sequently excavated many times (Kelley et al., andesitic phase ca. 7.8–8.0 Ma and a younger in the vicinity of Cerro Pelado (CPel, Fig. 2; 2004). The vent for the dacite is not exposed and dacitic phase of uncertain age. Goff et al., 2005a). Two samples from the ridge may have collapsed into the caldera. The fl ow Basalt and andesite flows that cap Cerro crests have 40Ar/39Ar dates of 8.83 ± 0.14 (P28, was dated previously by Gardner et al. (1986; Pedernal , Mesa Escoba, and Polvadera Mesa to Table 2) and 8.90 ± 0.17 Ma (P22, Table 2); K-Ar, 4.21 ± 1.3 Ma) and Justet (2003; P229, the east of Encino Point have previously been platy basaltic trachyandesite midway down west 3.86 ± 0.08 Ma). A biotite age of 4.36 ± 0.07 Ma assigned to the Lobato Formation (Smith et al., fl ank of Cerro Pelado is dated at 9.50 ± 0.21 Ma (31, Table 1) was determined for the dacite dur- 1970), but the origin of the fl ows has never been (P29, Table 2, Justet, 2003). ing this investigation. discussed. Based on available age and geo- We obtained new 40Ar/39Ar hornblende ages chemical data (Singer, 1985; Justet, 2003; Rowe of 8.53 ± 0.63 Ma (16, Table 1) for a porphyritic Northwestern Jemez Mountains et al., 2007), the fl ows likely originated from hornblende dacite fl ow capping the summits A 7.3–8.7 Ma intermediate composition vol- Encino Point. The fl ows preserved on these of Las Conchas and Los Griegos (LC and LG, canic highland forms the La Grulla Plateau in mesas were erupted within a short time interval Fig. 2) and 8.66 ± 0.22 Ma (17, Table 1) for a the northwestern to north-central Jemez Moun- between 7.7 and 7.9 Ma, based on K-Ar ages of porphyritic hornblende-biotite dacite dome and tains. The Cañones fault zone, one of the west- Manley and Mehnert (1981) and 40Ar/39Ar ages fl ow south of Rabbit Mountain (RM, Figs. 2 and ern border faults of the Rio Grande rift (Figs. 3 (P67–P68, Table 2) of Justet (2003) and Mal- 4). Justet (2003) determined a 40Ar/39Ar age of and 6), controlled the location of volcanic vents donado and Miggins (2007). The mesa-capping 7.91 ± 0.14 Ma for a hornblende dacite dome in the northwestern Jemez Mountains, and the basalt ages are within the age range of fl ows and at the head of Sanchez Canyon (P26, Table 2). fault zone continued to be active after the older dikes at Encino Point. Previous workers (Man- A dacitic ash bed in the Pojoaque Member of volcanic units were emplaced. As mentioned ley and Mehnert, 1981; Baldridge et al., 1994; the Santa Fe Group (Koning and Maldonado, earlier, Smith et al. (1970) assigned the older, and Gonzalez, 1995) have documented ~670 m 2001) in Ancho Canyon on the southeast side of more mafi c volcanic rocks in the northwestern of down-to-the-east faulting of the 7.7–7.9 Ma the Jemez Mountains that probably was derived Jemez Mountains to the Lobato Basalt and the lava fl ows across the Cañones fault zone. from a Paliza Canyon Formation dacite dome younger, more silica-rich rocks to the Tschi- Flows on Mesa Escoba and Polvadera Mesa yielded an age of 8.48 ± 0.14 Ma (18, Table 1). coma Formation. (Figs. 2 and 7) were sampled to clarify the prior We also acquired a relatively young 40Ar/39Ar Encino Point. Encino Point is located on results. A previously undocumented tephra fall age of 7.20 ± 0.68 Ma for a porphyritic biotite- the northern tip of the La Grulla Plateau (Figs. bed is poorly exposed between the mafi c lava dacite fl ow capping a hill east of Aspen Ridge, 2 and 6). As many as eight andesite to basaltic- fl ows (between CM21 and CM23 on Polvadera but the latter date may be affected by hydro- andesite lava fl ows are exposed in the escarpment Mesa on Fig. 7). In addition, we mapped the thermal alteration (because of the large error, on the west side of Encino Point (Lawrence , thickness of synrift Santa Fe Group sediments this data is not reported in Table 1). These dates 1979; Singer, 1985; Singer and Kudo, 1986). A between the top of the upper Oligocene to lower lie within the typical range of 7 to 10 Ma for the deposit preserving a transition from a phreato- Miocene Abiquiu Formation and Miocene grav- Paliza Canyon Formation in the southern Jemez magmatic to a strombolian style of eruption is els preserved on top of the lava fl ows. The mesa- Mountains. present at the base of the fl ow sequence above capping basalts dated during this study range the Ojo Caliente Sandstone at the north end from 7.74 ± 0.21 to 8.33 ± 0.11 Ma (33–38, Western Jemez Mountains of the mesa (Kelley et al., 2007c). The fl ows Table 1). Pumice from the interbedded tephra Paliza Canyon Formation basaltic andesite were likely derived from an eroded volcanic within the succession on Polvadera Mesa, which and trachyandesitic lava fl ows fi lling paleo- center that occupied the low-lying area known contains phenocrysts of biotite and hornblende,

valleys cut into the Ojo Caliente Sandstone of as Banco Largo to the west of Encino Point is low-silica rhyolite (72.7% SiO2; Table 3) and the Tesuque Formation are preserved on Fenton (Fig. 6). Rubbly debris to the west of Encino is 7.7–7.9 Ma, based on the ages of the basalt Hill on the western topographic rim of the Valles Point was originally mapped as a landslide fl ows above and below. This age is older than caldera (Fig. 5). Four samples of basaltic ande- deposit by Smith et al. (1970); however, intact most Bearhead Rhyolite ages (see below), and site, two from outcrops and two clasts from the deposits of interbedded andesite lava and ande- Bearhead Rhyolite is generally a high-silica overlying volcaniclastic deposit, gave consis- sitic pyroclastic material, as well as northeast- rhyolite; thus, the source of this ash-fall tephra tent groundmass 40Ar/39Ar ages of 8.98 ± 0.28– striking andesitic to dacitic dikes, were mapped is unknown. 9.00 ± 0.13 Ma (26–29, Table 1). A basalt dike by Lawrence (1979), Singer (1985), Lawrence Sandy conglomerate that includes rounded that presumably was the source vent for some et al. (2004), and Kelley et al. (2005a), and are clasts of andesite, dacite, and Amalia Tuff of the mafi c fl ows is exposed along Forest Road interpreted to be the remnants of an eroded underlies the 7–8 Ma basalt and overlies the 376 south of San Antonio Hot Spring (Kelley cone. One andesitic dike yields groundmass Ojo Caliente Sandstone on Mesa del Medio on et al., 2004). Porphyritic trachyandesite that lies 40Ar/39Ar ages of 7.99 ± 0.10 and 7.94 ± 0.10 Ma the east side of Cañones Canyon. One of the above the basaltic andesite and is intercalated (32, Table 1). The western escarpment at Encino andesite clasts gives a 40Ar/39Ar age of 29.29 ± with volcaniclastic sediments has a plagioclase Point exposes a dacite cryptodome (fi rst recog- 0.50 Ma (1, Table 1), suggestive of a source in 40Ar/39Ar age of 8.26 ± 0.09 Ma (30, Table 1). nized by Singer, 1985) and overlying andesite the San Juan volcanic fi eld to the north (Fig. 1). A biotite-hornblende dacite fl ow that has fl ows, fl ow breccia, and pyroclastic beds that The age of the clast is older than the oldest ages been assigned to the Tschicoma Formation were deformed as the dome was emplaced. The of 22.7–28.5 Ma volcanic rocks in the Latir vol- (Smith et al., 1970) rests on and is inset against margin of the dome is glassy, and the core has an canic fi eld to the northeast (Fig. 1; Zimmerer and the Paliza Canyon Formation on the west side of equigranular crystalline texture. Singer (1985) McIntosh, 2012). Consequently, the presence the caldera because the dacite fi lls a paleovalley determined a K-Ar age of 7.85 ± 0.22 Ma for of clasts with a San Juan source suggests these

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CerroCerro 7.89±0.047.89±0.04 Ma PPedernaledernal zone lt 8.22±8.22± f 0.130.13 MMaa ez Escoba

n saa MesaM Escoba GonzalezGo fault zone7.90±0.087.90±0.08 MMaa a 8.33±8.33±

a 7.74±0.217.74±0.21 MaMa s 0.11Ma0.11Ma

7.99±0.107.99±0.10 Ma lvaderalvader Me 18.42±0.371818.428 42 Ma Po 2±037M2±0.37 Ma t zone BancoBanco Largo TiTi 7.79±0.037. 79±0.03 Ma nesn fault z 7.85±0.2277.7.8 85±085±55±0±0±0 222 2 MaMa o ? 36°7.5′N

EncinoE k CañonesCaño fault zone PointPoint

Cree

es 8.10±0.138. 10±0.13 MaM ne

oneso Creek

Cañ 7.42±0.137.42±0.13 Ma 8.75±0.068.75±0.06 MaMa 8.11±0.118.11±0.11M1 Ma BarranconesBarrancones Hill dacite of La Grulla Plateau

Four Hills andesite of La 7.357737.33355± ±0.16±0.10116M6 MMaa 8.17±0.088.17±0.08 Ma Grulla Plateau

7.357.35±0.±0.0.21 Maa

Grullrulla Plateau basaltic andesite of Encino Point La GGrulla Plateau

? basalt of La Grulla Plateau

CCerroerro Pavo volcanic center Cerro Pelon 1 km Cerrroo 7.68±0.68±0.04.04 Ma del 7.27.27±0.7±0.07 Ma Grant 1 mile 7.81±7.81± 7.43±0.14 Ma 0.090.09 MaMa Hill 33 ? 7.77.70±00±0.09 Ma

′ 77.80±0.13.80±0.13 MaMa 36°0.0 N 7.34±0.147.34±0.14 Ma 7.70±0.077.70±0.07 MaMa 7.42±0.057.42±0.05 MMaa 7.61±0.077.61±0.07 MaMa CerroCerro de llaa GGaritaarita travetraverserse

106°30′W Figure 6. Geologic map of the La Grulla Plateau highlighting 7.3–8.7 Ma lava ﬂ ows. Modiﬁ ed from Lawrence et al. (2004), Kelley et al. (2005a, 2005b), Kempter et al. (2004), Gardner et al. (2006), and Goff et al. (2006).

gravels most likely belong to the Hernandez thicken dramatically across the Cañones fault ﬂ uvial unit, is particularly pronounced (Kelley Member of the Chamita Formation, an ancestral zone from ~90 m on Cerro Pedernal to >300 m and Koning, 2007; Koning et al., 2007b). For Rio Chama deposit (Koning et al., 2005). on Polvadera Mesa (Fig. 7). Thickening of example, the Ojo Caliente Sandstone Member Detailed mapping of the Santa Fe Group the 19–13.5 Ma Tesuque Formation, which appears to be absent on Cerro Pedernal, but is below the basalts has provided new insights includes, from oldest to youngest, the ﬂ u- on average ~120 m thick on Mesa Escoba in into the evolution of the western margin of vial Chama–El Rito Member, the eolian Ojo the hanging wall of the Gonzales fault, a splay the rift in this area. Santa Fe Group sediments Caliente Sandstone Member, and an unnamed in the Cañones fault zone (Figs. 6 and 7). The

632 Geosphere, June 2013

Bend in Section

NW SE

Cerro Pedernal 10,000 ft. Mesa Escoba Tb + Ta 7.83 ± 0.07 Ma (Maldonado and Miggins, 2007) Tstc Tb+Ta 04C5 7.74 ± 0.21 Ma 9000 7.90 ± 0.08Ma Tab 04C10 7.71 ± 0.18 Ma (Justet, 2003) Tr Tsch Tr Te CM24 8.22 ± 0.13 Ma Te Tsto Ta Polvadera Mesa CM23 8.33 ± 0.11 Ma 8000 Kd Te Trt Kd Tstc Tsch Ta Tstf CM21 7.89 ± 0.04 Ma Tsch? Tsto 7000 Tab Tb (projected) 2000 ft. 04C3 7.79 ± 0.03 Ma Tstc Gonzalez fault zone Cañones fault zone 6000

V.E. = 2 Miocene Santa Fe Group Chamita Formation Hernandez Member Tsch Miocene Abiquiu Fm. Ta Miocene La Grulla Tab Fm. andesite Oligocene Ritito Tesuque Formation Tr Miocene rhyolite tephra Conglomerate Trt interbedded with Hernandez Tstf unnamed fluvial unit Miocene La Grulla Te Eocene El Rito Fm. Tb Fm. basalt Tsto Ojo Caliente Sandstone Kd Cretaceous Dakota Fm. Tstc Chama-El Rito Member

Figure 7. Geologic cross section showing thickness variations in the Santa Fe Group (shaded units) across the Gonzalez and Cañones fault zones, based on the geologic map of Kelley et al. (2005b). The age data are from Table 1 (Justet, 2003; Maldonado and Miggins, 2007). Line of section shown on Figure 3.

7–8 Ma basalt and andesite lava fl ows rest on by the Hernandez Formation overlapped in time Canyon. At least three other thin (1–2.5 m) fl ows the Chama–El Rito Member on Cerro Pedernal, with eruption of lavas from Encino Point that of basalt and andesite are present in the bottom on the Ojo Caliente Sandstone and younger fl u- fl owed into a low spot in the area now occupied of the Cañones Canyon east of Encino Point vial Hernandez Member (Chamita Formation; by Cerro Pedernal, Mesa Escoba, and Polvadera (Figs. 2 and 6). These fl ows are interbedded 13.5–7.5 Ma) on Mesa Escoba, and solely on Mesa. The lava flows were then disrupted with poorly exposed Santa Fe Group sandstone Hernandez Member farther east on Polvadera by faulting sometime between 7.8 and 3 Ma and conglomerate that include rounded clasts Mesa (Fig. 7). The unnamed fl uvial unit is only (Baldridge et al., 1994; Gonzalez, 1995). of Proterozoic granite and quartzite. An 8.75 ± found on Polvadera Mesa. The ca. 7.8 Ma lava Another basalt fl ow (34, Table 1; 7.79 ± 0.06 Ma (39, Table 1) basalt fl ow is separated fl ow on Mesa Escoba is capped by Hernandez 0.03 Ma) lies in the bottom of Cañones Canyon from a younger (40, Table 1, 7.42 ± 0.13 Ma) Member gravel. Thus prior to eruption of the between Mesa Escoba and Polvadera Mesa. overlying andesite fl ow by ~15 m of poorly lava, the Ojo Caliente Member was completely Manley and Mehnert (1981) determined a K-Ar exposed Santa Fe Group (Fig. 6; Lawrence et al., eroded from Cerro Pedernal and was partially age of 7.6 ± 0.4 Ma for this same fl ow. Reddish 2004). Other basaltic fl ows inter calated with stripped from Mesa Escoba. Some of the eolian sedimentary rocks that appear to be Hernandez Santa Fe Group sediments in Cañones Canyon sand from the Ojo Caliente was redeposited as Formation overlie the thick fl ow. The age and yield 40Ar/39Ar ages of 8.10 ± 0.13 Ma to 8.17 ± a local fl uvial unit now preserved on Polvadera geometry of this fl ow relative to the fl ows on the 0.08 Ma (Fig. 6; 41–43, Table 1; Kempter et al., Mesa. Consequently, some of the erosion and mesas to the north and south suggest that (1) the 2004; Lawrence et al., 2004). The spatial distri- associated faulting had to take place prior to fl ow is downdropped along a narrow graben bution of the basalts in the bottom of the canyon, the deposition of the 13.5–7.5 Ma Hernandez within the Cañones fault zone, as illustrated in which are not aligned along the Cañones fault Formation during middle Miocene time. Some Fig. 7, or (2) the fl ow fi lled a narrow valley that zone, appears to favor a paleotopographic rather of the ancestral Rio Chama deposition recorded occupied the general position of modern Cañones than a structural explanation for the relative

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vertical position of the fl ows in the vicinity of 40Ar/39Ar age of 7.47 ± 0.14 Ma (P70, Table 2; de la Garita (CdlG) along the northern margin Cañones Canyon. Justet, 2003). The Cerro del Grant center is of the Valles caldera (Figs. 2 and 6). A stack Flows south of Cerro Pelón (west). (Note: composed mainly of porphyritic dacite overly- of fl ows separated by basal glassy fl ow brec- Two widely separated hills in the northern ing trachyandesite on the south side of the hill. cias and vesicular fl ow tops with little sediment Jemez Mountains are named Cerro Pelón on The 40Ar/39Ar biotite age of the older trachy- between the fl ows underlies the lower half of the topographic maps [Fig. 4]. We distinguish the andesite from the north side of Cerro del Grant ridge (Fig. 8). The lowest fl ow in the sequence hills by adding the terms “west” and “east.”) is 7.68 ± 0.04 Ma (49, Table 1). The crystal-rich is a biotite-bearing dacite, and the overlying Flows just to the south of Cerro Pelón (west), a dacite of “Hill 33,” so named because the top fl ows are porphyritic andesite (Figs. 8 and 9). younger andesitic center on the southwest edge of the dome lies near the center of section 33 The character of the fl ows changes in the upper of the La Grulla Plateau (Figs. 2 and 6), include (T. 21 N., R. 4 E.), yields a 40Ar/39Ar biotite half of the ridge above an elevation of ~2990 m a basal basalt fl ow, an overlying crystal-rich age of 7.27 ± 0.07 Ma (50, Table 1). Andesite (Fig. 8). Tan, very fi ne-grained sandstone that andesite with sparse biotite (Goff et al., 2006), from the base of the west side of Hill 33 has a is <3 m thick separates the lower sequence and a capping weakly porphyritic basalt. These groundmass 40Ar/39Ar age of 7.81 ± 0.09 Ma from the upper sequence. Flows are increas- fl ows, exposed on the northwest rim of the cal- (51, Table 1); this age suggests a correlation of ingly mafi c upsection below the break and dera, yield 40Ar/39Ar groundmass ages of 7.70 ± this andesite with the older fl ows to the south of increasingly felsic upsection above the break. 0.07–7.80 ± 0.08 Ma (44–46, Table 1). Based Cerro Pelón (west) in the northwestern margin The fl ows below the sandstone are intruded by on the age and mafi c composition of the units, of the caldera. Justet (2003; P69, Table 2) deter- an altered, undated rhyolite dike interpreted to these fl ows may correlate to fl ows on Encino mined a 40Ar/39Ar age of 7.21 ± 0.12 Ma for a be Bearhead Rhyolite (Goff et al., 2006). The Point. Alternatively, these mafi c fl ows may have trachyandesite at the southeast base of Hill 33. fl ow just above the sandstone is crystal-rich come from a center that was active at the same Cerro de la Garita traverse, northern rim andesite porphyry with trace biotite, which in time as the Encino Point center, and has since of the Valles caldera. Approximately 640 m of turn is overlain by a porphyritic two-pyroxene collapsed into the Valles caldera. andesitic to dacitic fl ows that span the transi- andesite. A rhyolite pumice-covered slope that La Grulla Plateau. The dark-colored ande- tion between lavas mapped as Paliza Canyon may include ~70 m of pumiceous volcaniclastic site and basalt lavas of Encino Point are overlain Formation and lavas mapped as La Grulla For- sediment or ash-fall deposits lies upslope of the by lighter-colored, porphyritic to fi ne-grained mation are exposed on the south side of Cerro two-pyroxene fl ow. All fl ows below the pumice- trachyandesite, dacite, and trachyte. Generally, the trachyandesites on the La Grulla Plateau are stratigraphically older than the dacites in the Rock unit Sample # Age same area. These fl ows originated from north- La Grulla Fm. hornblende dacite F06-21 7.34±0.14 Ma F06-22 7.61±0.07 Ma erly-aligned volcanic centers on the plateau that 3200 La Grulla Fm. biotite dacite parallel the projection of the Cañones fault zone Pumice (rhyolitic) covered into this area (Lawrence, 1979). The centers slope are, from north to south: Barrancones Hill, Four Paliza Canyon Fm. andesite F06-23 Hills, Cerro Pavo, Cerro del Grant, Cerro Pelón 3100 (west), Hill 33, and Cerro de la Garita (Fig. 6). Barrancones Hill is a hornblende-biotite– Paliza Canyon Fm. andesite, F06-24 crystal-rich with trace bearing trachyte to dacite (Lawrence, 1979; biotite Lawrence et al., 2004; Rowe et al., 2007). No 3000 age data are available for this dome. Three Paliza Canyon Fm. sandstone

domes, two of dacitic composition and one of Paliza Canyon Fm. andesite trachyandesitic composition, are clustered at opaline alteration the Four Hills center. The K-Ar age of 7.35 ± Paliza Canyon Fm. flow-banded andesite F06-26 0.21 Ma for one of the hornblende-biotite dacite 2900 domes (Singer, 1985; Fig. 6) is indistinguishable 40 39 from the 7.36 ± 0.16 Ma plagioclase Ar/ Ar Elevation (m) hydrothermally altered age of the crystal-rich trachyandesite dome Bearhead rhyolite F06-20a intrusion (47, Table 1). A light-gray, fi ne-grained rhyo- 2800 lite to trachyte that shares chemical affi nity to Paliza Canyon Fm. andesite the Bearhead Rhyolite (Rowe et al., 2007) laps F06-27 onto the south side of the Four Hills andesite. This unit from an unknown vent yields a 6.51 ± 0.21 Ma 40Ar/39Ar groundmass age, although the 2700 Paliza Canyon Fm. andesite F06-28 spectrum is discordant and the error is large (48, Table 1). The undated trachyte to dacite of Cerro Pavo is a fl ow-banded, weakly porphyritic lava 2600 with a few mafi c enclaves (Lawrence, 1979; Paliza Canyon Fm. dacite F06-29 Justet, 2003; Rowe et al., 2007). The two-pyroxene trachyandesite to trachyte of Cerro Pelón Figure 8. Schematic diagram of lava fl ows on Cerro de la Garita. (west) also contains mafi c enclaves (Lawrence, Dating was attempted on samples F06-29 and F06-24, but the ground 1979; Justet, 2003; Rowe et al., 2007) and has a mass yielded discordant age spectra because of alteration.

634 Geosphere, June 2013

Cerro de la Garita higher than the range for both the Paliza Canyon and La Grulla Plateau lavas (Fig. 10E). Sample 16 F06-23, the highest of the lavas assigned to the Paliza Canyon Formation, has the highest U/Nb (0.21), but the underlying Paliza Canyon Formation fl ow (F06-24) has the lowest U/Nb (0.09) of the whole sequence. The Zr contents 12 of both the Paliza Canyon Formation fl ows and the La Grulla fl ows on CdlG are positively cor-

related with SiO2 and the CdlG La Grulla lavas trachyte have slightly lower Zr concentrations (Fig 10F). O wt %

2 trachy- 06-21 In summary, despite erosional breaks and dif- 8 basaltic andesite 06-22 ferences in the mineralogy and major-element trachy- 06-24 rhyolite andesite 06-23 concentrations of the ﬂ ows upsection, trace-ele-

O + K trachy- 06-27 06-29 ment distinctions between the older fl ows and 2 basalt 06-26 the younger fl ows along the Cerro de la Garita Na traverse are not clear, with the exception of a 06-20a 4 small decrease in Zr content and perturbations in U concentration at the top of the Paliza Can- basaltic yon Formation. In some respects, the geochemi- basalt andesite andesite dacite cal affi nity of the whole succession is like that of the Paliza Canyon Formation (TiO ), but in 0 2 40 50 60 70 80 other respects, the trace-element data suggest that all of the lavas in the CdlG may be closely SiO2 related, with an affi nity that is more similar to La Grulla Plateau lavas (MgO and U/Pb). Figure 9. Total alkali-silica diagram for samples from Cerro de la Northeastern caldera. Several dacitic fl ows Garita. The International Union of Geological Sciences (IUGS) clas- in the northeastern part of the caldera that had sifi cation of volcanic rocks (after LeBas et al., 1986) is plotted for been previously mapped as Paliza Canyon For- reference. White squares are La Grulla Formation; the black dia- mation and Tschicoma Formation may, in fact, monds are Paliza Canyon Formation. Black square is interpreted to correlate to La Grulla Plateau fl ows. These be Bearhead Rhyolite. dacite fl ows have biotite 40Ar/39Ar ages 7.66 ± 0.04 Ma and 7.78 ± 0.10 Ma (54–55, Table 1) and appear to be interlayered with Santa Fe covered slope are interpreted to be Paliza Can- ridge leading to CdlG and to further test our Group sandstone (Gardner et al., 2006), as is the yon Formation andesite and dacite, although the unit assignments. The CdlG samples do not case with the La Grulla mafi c fl ows in the Cerro subtle shift toward more alkaline compositions have unusually high Ba concentrations, and Pedernal area (e.g., Fig. 7). The fl ows are to the occurs at the sedimentary break (Figs. 8 and 9). the Ba values overlap those of both the Paliza east of a signifi cant E-side-down fault that jux- The pumiceous interval is overlain by a crystal- Canyon Formation and the La Grulla Plateau taposes the Paliza Canyon Formation andesite rich, two-pyroxene, hornblende-biotite dacite. lavas (Fig. 10A). Nb concentrations of all CdlG and the dacites of the La Grulla Plateau on CdlG This dacite to trachyandesite (Justet, 2003) samples are similar to concentrations in the La against the Santa Fe Group sandstones (dotted fl ow yields a biotite 40Ar/39Ar age of 7.61 ± Grulla Plateau lavas, but Nb for the CdlG units and queried projection of Cañones fault zone on 0.07 Ma (52, Table 1). The sequence is capped assigned to Paliza Canyon remains constant Fig. 6). The fault in the northeast caldera wall is

by a sparsely porphyritic dacite that is derived with increasing SiO2, while Nb in the CdlG La covered by colluvium. Interestingly, the capping from a vent on Cerro de la Garita, which is the Grulla Plateau fl ows decreases (Fig. 10B). In 7.42 ± 0.05 Ma (56, Table 1) porphyritic biotite- southernmost of the preserved La Grulla Plateau contrast to the pronounced increase in Nb with hornblende dacite fl ow is not obviously affected centers. The biotite 40Ar/39Ar age of the CdlG increasing silica content measured in the Paliza by the fault, and Bandelier Tuff to the north is dacite fl ow is 7.34 ± 0.14 Ma (53, Table 1). The Canyon Formation elsewhere in the JMVF, the unaffected by the fault. pumice , which is older than 7.61 Ma, is older Nb in the CdlG Paliza Canyon fl ows does not than typical Bearhead Rhyolite and may corre- increase with increasing silica content (Fig. Latest Miocene Activity (7–6 Ma) late to the pumice on Polvadera Mesa. 10B). All CdlG samples, except for the high- Rowe et al. (2007) found that La Grulla est sample on the traverse, have MgO contents Bearhead Rhyolite Plateau lavas are geochemically distinct from that are more similar to La Grulla Plateau lavas The intimately associated Bearhead Rhyolite both Paliza Canyon Formation lavas from the than Paliza Canyon Formation lavas (Fig. 10C). and Peralta Tuff were mainly emplaced dur-

southern Jemez Mountains and younger Tschi- The TiO2 concentrations for all of the CdlG ing an episode of intense rhyolitic volcanism coma Formation lavas to the east (Fig. 10). samples overlap both Paliza Canyon Formation peaking between 6.5 and 7 Ma (McIntosh We analyzed the trace-element data from the and La Grulla Plateau values (Fig. 10D). The and Harlan, 1991; Justet and Spell, 2001) and La Garita section (Fig. 8 and Table 3) to see Pb/Ce ratios for the CdlG samples lie within a located primarily in the southeastern Jemez if sharp breaks or gradational trends in chemi- relatively narrow range (0.15 to 0.22), and the Mountains. At least 20 vents that extruded cal evolution are preserved in the ﬂ ows on the U/Nb ratios are 0.14–0.21, which are generally rhyolite domes, ﬂ ows, and pyroclastic deposits

Geosphere, June 2013 635

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. F Tshicoma La Grulla Plateau Encino Point Paliza Canyon Paliza Canyon CdlG La Grulla CdlG et (wt. %) (wt.%) 2 2 dioxide versus SiO SiO Tschicoma La Grulla Plateau Encino Point Paliza Canyon Paliza Canyon CdlG La Grulla CdlG C 45 50 55 60 65 70 75

45 50 55 60 65 70 75

8 6 4 2 0

MgO (wt. %) (wt. MgO 500 400 300 200 100 Zr (ppm) Zr E BC Tschicoma La Grulla Plateau Encino Point Paliza Canyon Paliza Canyon CdlG La Grulla CdlG (wt. %) Pb/Ce 2 SiO Tschicoma La Grulla Plateau Encino Point Paliza Canyon Paliza Canyon CdlG La Grulla CdlG 0 0.1 0.2 0.3 0.4 0.5 45 50 55 60 65 70 75 0

0.2 0.1 80 60 40 20

Nb (ppm) Nb 0.25 0.15 0.05 U/Nb A D (wt. %) (wt. %) 2 2 SiO SiO Tschicoma La Grulla Plateau Encino Point Paliza Canyon Paliza Canyon CdlG La Grulla CdlG Tschicoma La Grulla Plateau Encino Point Paliza Canyon Paliza Canyon CdlG La Grulla CdlG silica; (E) uranium-niobium ratio versus lead-cerium ratio; and (F) zirconium versus silica. silica; (E) uranium-niobium ratio versus lead-cerium ratio; and (F) zirconium Figure 10. New geochemical data from Cerro de la Garita (CdlG—red symbols) plotted with geochemical data of Singer (1985), Just symbols) plotted with geochemical data of Singer de la Garita (CdlG—red Cerro 10. New geochemical data from Figure (2003), and Rowe et al. (2007). (A) Barium versus silica; (B) niobium (C) magnesium (D) titanium 45 50 55 60 65 70 75 45 50 55 60 65 70 75 0

1.6 1.2 0.8 0.4

2 2 (wt. %) (wt. 5000 4000 3000 2000 1000 TiO Ba (ppm) Ba

636 Geosphere, June 2013

of Bearhead Rhyolite are aligned along north- also discovered in the northeastern wall of the the rhyodacite of Rendija Canyon (low-silica and northeast-striking structures in the southern Valles caldera (Gardner et al., 2006); however, rhyolite) in the Los Alamos area are less clear; Jemez Mountains (Smith and Lynch, 2007). one north-striking rhyolite dike has a 4.81 ± the vents have been partially or totally destroyed The rhyolite lavas and associated lithic-rich 0.04 Ma biotite 40Ar/39Ar age (62, Table 1). This by the formation of the Toledo and Valles cal- pyroclastic deposits are typically crystal poor rhyolite is petrographically similar to the Cañon deras. Tschicoma Formation fl ows are commonly (<3%), with sparse phenocrysts of quartz, sani- de la Mora rhyolite located ~4 km to the north, coarsely porphyritic with plagioclase and sanidine dine, biotite, ± plagioclase. We identifi ed one but both the U and Th content of this rhyolite phenocrysts up to 2–3 cm. Pink quartz pheno- more Bearhead vent in the southeastern Jemez (JG05-14; Table 3) and the age are more simi- crysts are found in one of the older fl ows in Mountains during this project. An unnamed hill lar to the low-silica rhyolite of Rendija Canyon the Los Alamos area, the rhyodacite of Rendija north of Paliza Canyon in the southern Jemez (Tschicoma Formation; Broxton et al., 2007) Canyon (low- silica rhyolite). Mafi c enclaves are Mountains that was previously mapped as a discussed in the next section. The exact affi nity common. Variable amounts of hornblende, bio- Canovas Canyon Rhyolite dome gave a biotite of this young dike remains unclear. tite, green pyroxene, and quartz may be present; 40Ar/39Ar age of 6.51 ± 0.48 Ma (57, Table 1). the presence or absence of these phenocrysts In addition, a rhyolite lava located east of Tres Pliocene (5.3–2.6 Ma) can be used to distinguish among the fl ows and Cerros has a sanidine age of 6.86 ± 0.28 Ma eruptive centers in the fi eld. Geochemically, the (58, Table 1). A faulted, aphyric rhyolite intru- Tschicoma Formation Tschicoma Formation lavas are predominantly sion that was previously mapped as Paliza Can- Tschicoma Formation dacitic eruptive centers dacite (Fig. 11); andesite and low-silica rhyolite yon andesite (Smith et al., 1970) was found just are most prevalent in the northeastern and east- fl ows are relatively rare in the Tschicoma For- southeast of Cerro Pelado. An obsidian sample ern part of the fi eld, ranging in age from 5.6 to mation (Broxton et al., 2007; Rowe et al., 2007). from the intrusion yielded a glass 40Ar/39Ar age 2.7 Ma (Goff et al., 1989; Broxton et al., 2007; The eruption of signifi cant volumes of dacite in of 7.62 ± 0.44 Ma (59, Table 1), and a sample of Samuels et al., 2007). Most centers correspond a short amount of time led to the deposition of devitrifi ed rhyolite yielded a groundmass age of to the prominent peaks that form Sierra de los voluminous debris fl ows and fl uvial sedimen- 7.83 ± 0.26 Ma (60, Table 1; see quality assign- Valles in the northern and eastern Jemez Moun- tary rocks composed of Tschicoma Formation ment in Supplemental File [footnote 1]). The tains, including Tschicoma Peak, Polvadera clasts. These deposits form the Puye Formation rhyolite petrographically resembles Bearhead Peak, Cerro Pelón (east), Caballo Mountain, in the northeastern part of the JMVF. Rhyolite intrusive rocks in the southern Jemez Pajarito Mountain, and Sawyer Dome (Fig. 2). Northern Jemez Mountains. Tschicoma For- Mountains, but the ages are older than the typi- The sources of a few of the large fl ows such as mation dacites in the north-central Jemez Moun- cal Bearhead Rhyolite age range (P72–P121, Table 2). 16 An important outcome of this investigation is the observation that the geographic distribution Tschicoma Fm. La Grulla “Tschicoma” of Bearhead Rhyolite is greater than has been Lobato Fm. previously described. Several rhyolite vents of La Grulla “Lobato” Bearhead Rhyolite age have been mapped in 12 the northern Jemez Mountains (Smith et al., 1970; Gardner et al., 1986; Loeffl er et al., 1988; Kempter et al., 2004). Loeffl er et al. (1988) determined K-Ar ages of 5.6–7.0 Ma for a clus- O wt % trachyte ter of domes near the northern caldera margin. 2 trachy- 8 basaltic andesite We found another small, previously unmapped, trachy- rhyolite rhyolite outcrop in nearby Cañon de la Mora. andesite O + K trachy- 2 This rhyolite, which has a typical Bearhead basalt phenocryst assemblage, yielded a sanidine Na 40Ar/39Ar age of 7.09 ± 0.13 Ma (61, Table 1). 4 Thus the Bearhead Rhyolite appears to have erupted along a northerly striking zone on the basaltic east-central side of the volcanic fi eld. The Bear- basalt andesite andesite dacite head Rhyolite footprint is therefore comparable in extent to the Quaternary Valles and Toledo 0 calderas, suggesting a rhyolitic magma system 40 50 60 70 80 similar in size to the system that produced the SiO Bandelier Tuff (Justet and Spell, 2001). Justet 2 and Spell (2001) speculate that a caldera did Figure 11. Total alkali-silica diagram showing the geochemistry of not form in late Miocene time because exten- Lobato Formation and Tschicoma Formation in the northeastern sional faulting associated with the Rio Grande Jemez Mountains compared to the basaltic andesite of the “Lobato” rift may have kept the system frequently vented, and the andesite and dacite of the “Tschicoma” on the La Grulla Pla- preventing the buildup of fl uid and gas pressure teau. The International Union of Geological Sciences (IUGS) classifi ca- that often triggers caldera eruptions. tion of volcanic rocks (after LeBas et al., 1986) is plotted for reference. Several intrusive bodies and dikes interpreted Data from Lawrence (1979), Singer (1985), Gardner et al. (1986), Goff to be composed of Bearhead Rhyolite were et al. (1989), Justet (2003), Wolff et al. (2005), and Rowe et al. (2007).

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tains appear to have fl owed from the northwestern of at least two fl ows separated by basal brec- voluminous Tschicoma Formation lava fl ows rim of the Toledo embayment toward the north cia, and is platy in outcrop. Previous mappers east of Los Alamos include dacites from Cerro and may have originated from vents within the have distinguished a different fl ow, in addition Rubio (2.18 ± 0.09–3.59 ± 0.36 Ma; Stix et al., embayment prior to its collapse and formation to Tschicoma Formation lava, at the northwest 1988), the dacite of Caballo Mountain (3.06 ± of the Toledo caldera (Gardner and Goff, 1996). end of the mesa. Smith et al. (1970) assigned the 0.15–4.66 ± 0.17 Ma), the low-silica rhyolite of The 40Ar/39Ar dates for three samples of porphy- fl ow to the Lobato Basalt, and Manley (1982) Rendija Canyon (4.98 ± 0.05–5.36 ± 0.02 Ma), ritic dacite between Cañoncito Seco to the south assigned the fl ow to El Alto Basalt; however, the dacite of Pajarito Mountain (2.93 ± 0.06– and lower Chihuahueños Canyon to the north we did not fi nd this fl ow to be distinctly differ- 3.09 ± 0.08 Ma), the dacite of Cerro Grande yielded nearly identical ages (3.26 ± 0.04–3.37 ± ent than the basaltic andesite of Cañones Mesa (2.88 ± 0.02 Ma–3.35 ± 0.17 Ma), and the 0.05 Ma; 63–65, Table 1). Consequently, these (Kelley et al., 2005b). Manley and Mehnert dacite of Sawyer Dome (3.18 ± 0.20–3.67 ± three samples may represent a single dacite (1981) and Manley (1982) obtained two K-Ar 0.29 Ma). By comparing our results discussed fl ow that extends almost 7 km from the rim ages of 2.8 Ma on this fl ow. above with those of Broxton et al. (2007), we of the Toledo embayment to the distal edge of Several key stratigraphic relationships are note that the older domes and fl ows (3.1–5.4 Ma Mesa del Medio. Biotite-bearing andesite along preserved on the north side of Cerro Pelón (east) Rendija Canyon, Tschicoma Peak, and Caballo the west fork of Polvadera Creek (66, Table 1; (Fig. 4). The ca. 2.8 Ma basaltic andesite of Mountain) are the most voluminous and are clus- 3.36 ± 0.06 Ma) and a rhyodacite southwest of Cañones Mesa overlies the ca. 3.6 Ma dacite of tered along the northeastern side of the Jemez Polvadera Peak (P128, Table 2; 3.23 ± 0.35 Ma; Cerro Pelón (east) and underlies a fl ow that is Mountains. Broxton et al. (2007) also pointed WoldeGabriel et al., 2006) may also be related to clearly El Alto basalt that erupted from a vent out that the oldest fl ow (Rendija Canyon) is the this eruptive episode. on the north side of Cerro Pelón (east). The most silicic. The remaining domes and fl ows in The Tschicoma Peak, Polvadera Peak, and basaltic andesite of Cañones Mesa may have the northern and northeastern Jemez Mountains Cerro Pelón (east) centers are part of a north- come from the same general vent area as the are in the 2.2 to 3.8 Ma age range. trending line of eruptive vents. These centers El Alto Basalt (Kelley et al., 2005b). A cone of A few additional samples of Tschicoma produced viscous, voluminous fl ows with steep- El Alto Basalt on El Alto Mesa just east-south- Formation dacite were analyzed as part of this sided fl ow lobes. The oldest unit along the main east of Cerro Pelón has a 40Ar/39Ar age of 2.87 ± study. A rhyodacite dome north of Cerro Rubio Tschicoma axis, a dacite located ~1 km south 0.02 Ma (71, Table 1), comparable to the age overlaps in age with the older cluster of domes of Polvadera Peak, has a 40Ar/39Ar date of 5.37 ± of 2.86 ± 0.05 Ma determined by Maldonado and fl ows (40Ar/39Ar age of 4.21 ± 0.12 Ma; 72, 0.36 Ma (P129, Table 2; WoldeGabriel et al., and Miggins (2007) for basalt samples farther Table 1). The 4.81 ± 0.04 Ma rhyolite dike in 2006). Lavas from the Tschicoma Peak center, north. A second, small-volume Tschicoma For- the northeastern wall of the caldera described including the massive Gallina fl ow, yield K-Ar mation dacite vent is exposed at the south end earlier could be associated with this phase of ages between 3.2 ± 0.1 and 4.46 ± 0.58 Ma of Cañones Mesa. The dacite of Cañones Mesa Tschicoma Formation eruptions. The plagio- (Goff et al., 1989). The Gallina fl ow, which cov- has a biotite 40Ar/39Ar age of 3.61 ± 0.05 Ma clase age of 3.50 ± 0.23 Ma (73, Table 1) for the ers an area of ~10 km2, is a fl ow-banded, crystal- (70, Table 1), which is virtually the same age as low silica rhyolite of Rendija Canyon is much rich, porphyritic lava (Kempter et al., 2005) that Cerro Pelón (east). younger than the ages determined by Broxton preserves impressive lobe morphology where it Another eruptive crater, El Lagunito Palo et al. (2007), but the sample was collected from spilled over Puye Formation deposits, fl owing Quemador, is located ~1.5 km southwest of the highest (youngest) fl ow at the vent. The more than 3 km from its source vent high on the Cerro Pelón (east). Pumice covers the fl oor of hornblende age of 3.44 ± 0.30 for the dacite of eastern fl ank of Tschicoma Peak. Age estimates the crater, which has previously been mapped Sawyer Dome (74, Table 1), which is from the for the Gallina fl ow range from 3.90 ± 0.15 Ma as part of the El Rechuelos Rhyolite (Smith summit of the dome, is within the range of ages (K-Ar, Goff et al., 1989) to 4.49 ± 0.21 Ma (67, et al., 1970; Kempter et al., 2004). This pumice determined by Broxton et al. (2007) for this lava. Table 1). A fl ow that is topographically below has been dated with poor agreement at 5.21 ± Broxton et al. (2007) describe a new unit called the Gallina fl ow has a groundmass 40Ar/39Ar age 0.25 Ma (K-Ar, Loeffl er et al., 1988) and 2.92 ± the dacite of upper Quemazon Canyon, a fl ow- of 3.66 ± 0.09 Ma (68, Table 1). Younger lavas 0.70 Ma (40Ar/39Ar; P146, Table 2, Justet, 2003). banded sparsely porphyritic dacite that sits on and domes form Polvadera Peak (ca. 3.13 ± Nonetheless, these ages, along with geochemi- the low-silica rhyolite of Rendija Canyon. The 0.07 Ma; K-Ar, Goff et al., 1989). cal data presented by Loeffl er (1984) suggest groundmass age of the sample collected for this Cerro Pelón (east; Fig. 4) is composed of a that pumices from this vent are more closely investigation is 2.92 ± 0.03 Ma (75, Table 1). porphyritic dacite. In general, craters and col- related to the Tschicoma Formation than to the lapse features are rare in Tschicoma Formation El Rechuelos Rhyolite. Pleistocene (<2.6 Ma) landforms, but a summit crater, breached to the A dacite dome east of Arroyo de la Frijoles south, is still preserved on Cerro Pelón (east). and west of Agua Caliente Spring has a 40Ar/39Ar El Rechuelos Rhyolite The biotite 40Ar/39Ar age of Cerro Pelón (east) is date of 3.81 ± 0.21 Ma (P123, Table 2, Justet, Three rhyolitic domes of El Rechuelos Rhyo- 3.64 ± 0.03 Ma (69, Table 1), much older than 2003). Interestingly, this fl ow is faulted down to lite that were emplaced at ca. 2.1 Ma (Dalrymple the K-Ar age of 2.96 ± 0.27 Ma determined by the east ~80 m by the Garcia fault zone (Kelley et al., 1967; Loeffl er et al., 1988; Justet, 2003) Goff et al. (1989) for this unit. et al., 2007c; Maldonado, 2008), in contrast to are located just west of Polvadera Peak. These Cañones Mesa is a broad mesa located to the the basaltic andesite of Cañones Mesa, which is domes erupted along a north-south–striking northwest of Cerro Pelón (east). Smith et al. not cut by the Cañones fault system. fracture system west of Polvadera Peak onto the (1970) and Manley (1982) mapped the lava Northeastern Jemez Mountains. Broxton underlying Tschicoma Formation surface. The capping Cañones Mesa as Tschicoma Forma- et al. (2007) summarized 40Ar/39Ar dates, the rhyolite is generally aphyric, contains obsidian tion. This lava contains olivine and is generally geochemistry, and the spatial distribution of horizons that are light gray because of numer- more crystal poor (<5%) than typical Tschi- Tschicoma Formation lava fl ows in the Sierra ous small bubbles in the glass, and is commonly coma Formation lavas. The lava is composed del los Valles of the northeastern JMVF. The brecciated along its margins. The northernmost

638 Geosphere, June 2013

dome, ~1.5 km northwest of Polvadera Peak, data, as well as geochemical data (Fig. 11), to “Lobato” Formation, are basaltic andesites, has landslide scarps along its northwestern fl ank, reveal a pattern of migrating volcanism across basalts, and andesites (Fig. 12) that erupted and two satellite outcrops of rhyolite in Cañada the northern Jemez Mountains that is not cap- from a center at Encino Point and a possible de Ojitos Creek may represent the detached rem- tured by the current stratigraphic nomenclature center near the northwestern Valles caldera nants from the original dome. The middle dome for the Polvadera Group, as revised by Gard- margin. The more mafi c lavas erupted from is the most voluminous and produced a short ner et al. (1986). The Lobato Mesa volcanic Encino Point generally fl owed northeastward. lava fl ow. The southernmost dome lies ~1.5 km center in the northeastern part of the JMVF Remnants of these fl ows cap Cerro Pedernal, southwest of Polvadera Peak, where the ground consists mainly of basaltic shield volcanoes Mesa Escoba, and Polvadera Mesa. The early surface is littered with obsidian and crystalline that were active 10.8–9.2 Ma (Fig. 12; Goff mafi c lavas are overlain by 7.7–7.3 Ma trachy- lava fragments. This dome has a 40Ar/39Ar age of et al., 1989; this study). Dacitic fl ows inter- andesite and dacite erupted from N-S aligned 2.09 ± 0.02 Ma (77, Table 1). bedded with basalt fl ows are more common at centers south of Encino Point along projected the south end of Lobato Mesa and are present strands of the Cañones fault zone; these rocks DISCUSSION high in the sequence of fl ows. Following erup- had been assigned to the “Tschicoma” Forma- tions on Lobato Mesa, the locus of volcanism tion by Smith et al. (1970). Rhyolitic domes Trends in Volcanic and Fault Activity shifted to the northwestern part of the JMVF, in the Cañoncito Seco area were emplaced across the Northern Jemez Mountains where volcanic centers on La Grulla Plateau 7.1–5.6 Ma along the eastern margin of the La were active between 8.75 and 7.30 Ma along Grulla Plateau volcanic center in the vicinity of Published (Manley and Mehnert, 1981; reactivated Laramide structures (Largo and the projected main strand of the Cañones fault Singer, 1985; Gardner et al., 1986; Goff et al., Cañones faults). Older (8.7–7.8 Ma) fl ows on zone (dotted line, Figs. 3 and 6). This rhyolitic 1989; Justet, 2003) and new geochronology La Grulla Plateau, which had been assigned volcanism is, for the most part, temporally

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Figure 12 (on this and following three pages). Maps showing the Miocene and Pliocene evolution N 36°10 of the Jemez Mountains volcanic ′ N 36°10 ﬁ eld through time. (A) 7–10 Ma ′ Lobato, Paliza Canyon, and Canovas Canyon centers. N35°50 ′ N35°50 ′ N35°40 ′ N35°40 ′ 35°30

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equivalent to Bearhead Rhyolite volcanism in Revisions to the Stratigraphic Jemez Mountains and the Tschicoma Formation the southeastern Jemez Mountains (Justet and Nomenclature of the Northern of the northeastern Jemez Mountains. Spell, 2001). Eastward migration of volcanism Jemez Mountains We formally propose applying the name La continued with the eruption of the voluminous Grulla Formation to the mafi c and intermediate dacitic to rhyodacitic domes of the Tschicoma Here, we argue that the terms “Lobato” and composition lava fl ows and volcanic centers on Formation in the northeastern Jemez Moun- “Tschicoma” should no longer be applied to the the La Grulla Plateau and in the northwestern tains between ca. 2.2 and 5.4 Ma. Some of volcanic rocks of the La Grulla Plateau because JMVF as far east as Polvadera Mesa. Infor- the youngest Tschicoma Formation dacites these rocks are temporally and geochemically dis- mal member-level names will be attached to (2.47 ± 0.14 Ma to 2.56 ± 0.06 Ma; Samuels tinct from volcanic rock units exposed to the east. each volcanic center associated with the La et al., 2007) lie beneath the Pajarito Plateau. Mafi c rocks on the La Grulla Plateau are younger Grulla Formation (e.g., andesite of Cerro Pelón Eruption of the 2.8 Ma (Manley and Mehnert, and are more siliceous than mafi c rocks on Lobato (west), dacite of Cerro Pavo, and andesite of 1981) El Alto basalt, the basaltic andesite of Mesa (Figs. 4 and 11). Andesitic and dacitic rocks Encino Point). We suggest using the name La Cañones Mesa, and the 2.1 Ma El Rechuelos of the La Grulla Plateau are older and are more Grulla Plateau volcanic complex for the entire Rhyolite (Loeffl er et al., 1988; Justet, 2003) alkalic than Tschicoma Formation to the east (Fig. succession of volcanic rocks in the northwest- marks migration of volcanism that is more 11). Furthermore, Tschicoma Formation dacites ern Jemez Mountains. The term El Rechuelos bimodal in nature into the northern margin of are signifi cantly more alkalic than Lobato Forma- Rhyolite should be restricted to the ca. 2.1 Ma the fi eld along the projections of fault splays tion dacites (Fig. 11). Singer and Kudo (1986), domes in the northeast part of the volcanic fi eld between the Garcia fault, which was active Justet et al. (2002), and Rowe et al. (2007) also (e.g., Loeffl er et al., 1988), and the name Bear- <3.8 Ma, and the Cerrito Blanco fault beneath noticed the temporal and geochemical differences head Rhyolite should be applied to the older the JMVF. between the “Tschicoma” in the northwestern 5.6–7.0 Ma rhyolites in Cañoncito Seco.

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Figure 12 (continued). (B) 7–8 Ma N 36°10 ′ N 36°10 La Grulla centers. ′ N35°50 ′ N35°50 ′ N35°40 ′ N35°40 ′ 35°30

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Based on the large number of geochronologic and radiogenic isotope ratios (Justet, 2003; of Proterozoic crust and solidifi ed Miocene to and geochemical data now available for the Wolff et al., 2005; Rowe et al., 2007). This Pliocene magma chambers (Rowe et al., 2007). Jemez Mountains, we propose formally aban- variation is thought to refl ect partial melting of Regional and temporal chemical differ- doning the name the Polvadera Group because a heterogeneous lithospheric mantle to produce ences within the JMVF are due partly to dif- the spatial and temporal patterns of pre-caldera parental basalts that then interacted with hetero- ferent styles of magma-crust interaction. For volcanic activity are complex. The age group- geneous crust (Wolff et al., 2000, 2005; Rowe example, Tschicoma Formation dacites of the ings do not separate cleanly into younger north- et al., 2007). The volcanic fi eld is constructed northeastern Jemez Mountains and mafi c-inter- ern JMVF versus older southern JMVF activity, on a complex Proterozoic lithosphere that was mediate lavas of the Cerros del Rio volcanic which was the basis for the original designation. formed during the assembly of North America fi eld (Fig. 4) appear to be related by magma All post–14 Ma, pre-Bandelier Tuff (as defi ned by collision of the Yavapai and Mazatzal prov- mixing between basalt and silicic crustal melt, by Gardner et al., 2010) volcanic and volcani- inces between 1.6 and 1.7 Ga (Shaw and Karl- whereas Paliza Canyon Formation intermediate clastic rocks in the JMVF are assigned to the strom, 1999; Karlstrom et al., 2004) and partly and silicic rocks are the products of fractional Keres Group (Fig. 5), and all Bandelier Tuff and overprinted by intrusion of granitoid plutons crystallization, assimilation-fractional crystal- younger volcanic and volcaniclastic units in the at 1.4 Ga. Proterozoic oceanic lithosphere is lization, and simple mixing between basalts JMVF belong to the Tewa Group. the likely source of primitive magmas that are and crustal melts, possibly in numerous magma represented among the pre-JMVF Santa Fe chambers (Rowe et al., 2007). An additional key Geochemical Patterns Group lavas and intrusions and is inferred to be observation is that the chemistry of the crustal parental to the main volcanic fi eld (Wolff et al., component is geographically distinguishable Rocks of the JMVF display a wide varia- 2005). As the fi eld evolved, the crust beneath the (Wolff et al., 2005; Rowe et al., 2007). Thus, tion in major- and trace-element abundances JMVF became an increasingly hybridized mix each major stratigraphic grouping dominated

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Figure 12 (continued). (C) 6–7 Ma N 36°10 ′ N 36°10 Bearhead centers. ′ N35°50 ′ N35°50 ′ N35°40 ′ N35°40 ′ 35°30

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by intermediate and silicic rocks as defi ned in from east to west, then east, through time, caus- volcanism was localized and focused on the site this paper (Paliza Canyon, La Grulla, and Tschi- ing the establishment of new magma systems of the future JMVF by ca. 14 Ma, coinciding coma) has its own geochemical signature. and geographically controlled changes in lava temporally with the 14 to 16 Ma deepening of The new major- and trace-element data pre- chemistry. More detailed sampling and analysis basins elsewhere in the rift (Chapin and Cather, sented in this paper from an approximately of lavas exposed in the northern wall of the cal- 1994). Olivine basalts erupted in the northeast 600-m-thick stack of intermediate-composition dera is needed to assess the importance of this JMVF in the vicinity of Guaje and Santa Clara lava fl ows on Cerro de la Garita reveal a subtle particular transition for our overall understand- canyons at 11–14 Ma (WoldeGabriel et al., shift in chemistry through time across the ing of the development of the volcanic fi eld. 2006). This mafi c volcanism was followed by Paliza Canyon Formation to La Grulla Forma- a short-lived, voluminous pulse of basaltic to tion transition. The La Grulla Formation lavas VOLCANISM, FAULTING, AND dacitic volcanism on Lobato Mesa that started have higher total alkalis (Fig. 9) and lower Sr, SEDIMENTATION HISTORY at ca. 10.8 Ma and continued to 9.2 Ma (Goff Y, Zr (Fig. 10F), and Nb (Fig. 10B) contents OF THE JMVF et al., 1989; this study). The oldest mafi c fl ows than the underlying Paliza Canyon lavas, with on Lobato Mesa are olivine basalt, but younger the two uppermost Paliza Canyon Formation This section integrates new and previously fl ows are composed of trachybasalt (Goff et al., samples (above the sandstone, Fig. 8) exhibiting published observations of patterns of Keres 1989). Coarse- to fi ne-grained dacites erupted transitional chemistry. These data are signifi cant Group volcanic activity, fault movement, and at the south end of the Lobato volcanic center in light of Rowe et al.’s (2007) conclusion that sedimentation history in the JMVF; new obser- between 10.4 and 9.8 Ma. This activity was shifts in JMVF chemistry are associated with the vations concerning the Tewa Group are sum- focused along down-to-the-west faults that establishment of new magma systems. Based on marized by Gardner et al. (2010). Sporadic, but coincide with the eastern margin of a gravity our mapping, the locus of faulting has migrated widespread, small-volume early Miocene mafi c low in the northern Jemez Mountains (Fig. 3).

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Figure 12 (continued). (D) 1.5– 5 Ma Tschicoma, Cerros del N 36°10 ′ N 36°10 Rio, El Rechuelos Rhyolite, and ′ El Alto Basalt centers. N35°50 ′ N35°50 ′ N35°40 ′ N35°40 ′ 35°30

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At virtually the same time, mafi c to felsic exposed a spectacular section of this volcani- the older Lobato Formation center along reac- centers were active in the southwestern Jemez clastic material northwest of Boundary Peak. tivated Laramide faults, including the Cañones Mountains, as noted by Bailey et al. (1969), Here, the beds, which are underlain by Santa Fe fault zone. Both the Cañones fault zone in the Gardner et al. (1986), and many subsequent Group and an 11.3 Ma basalt fl ow, lap onto a north-central Jemez Mountains and the Jemez researchers. The initial eruptions in the south- dacite dome and fl ow complex dated at 9.5 Ma fault zone in the southwestern Jemez Mountains western Jemez Mountains were basalt, trachy- (K-Ar, Goff et al., 1990; Goff et al., 2006). The (Fig. 2) are old rift-bounding structures that basalt, and rhyolite, but as the system evolved, upper part of the sequence is interlayered with were active starting ca. 25–30 Ma, although the trachyandesite, trachydacite, and dacite became and overlain by two-pyroxene andesite fl ows, Oligocene offset was modest (<100 m; Aldrich, the dominant lava compositions. Most of the including the fl ow capping St. Peter’s Dome 1986; Smith et al., 2002; Kelley et al., 2013). Paliza Canyon Formation and Canovas Can- (8.7 Ma, K-Ar; Goff et al., 1990). Layers of The NE-striking Cañones fault zone curves to yon Rhyolite centers in the southwestern Jemez dacitic ash collected from the volcaniclastic a more N-S orientation beneath the JMVF, so Mountains are located to the east of the Jose fault beds from all three of the above-mentioned can- that the Cañones fault zone, which at some (Fig. 3; Kelley, 1977), a signifi cant NE-striking yons are dated at 9.2–9.6 Ma (P48–P51; Lavine point in its history may have connected to the rift structure that separates Santa Fe Group sedi- et al., 1996). Jemez fault zone, now aligns with the Cañada ments (Zia Formation) to the southeast from Tri- In the southeastern Jemez Mountains, deep de Cochiti fault zone in the southern Jemez assic sedimentary rocks to the northwest; fault canyons and ravines cut a faulted, north-trend- Mountains . slivers of steeply-dipping Jurassic units are ing horst of Keres Group rocks exposed by The Cañones fault zone was an east-side- caught up in the fault zone (Osburn et al., 2002). the Cañada de Cochiti fault system (Goff et up reverse fault during Laramide deformation The Jose fault zone appears to have infl uenced al., 2005b, Fig. 3). Within the Cochiti Mining (Smith, 1995). Smith et al. (2002) determined the location of the dated ca. 9.4 Ma Canovas District, medium-grained monzonite to quartz that the reverse fault experienced east-side- Canyon rhyolite to dacite plug on the western monzonite of the Bland stock intrudes lower down normal faulting in late Oligocene time edge of Borrego Mesa east of Ponderosa. The Paliza Canyon Formation fl ows and volcani- (28–25 Ma). Deformation across the rift mar- Jose fault can be traced to the north-northeast clastic beds, and <100 m of white to pale-pink, gin continued during Miocene deposition of the where Triassic and remnants of Jurassic rocks well-sorted sandstone tentatively assigned to the Santa Fe Group and into Pliocene time. East- are found on the east side of San Juan Canyon Santa Fe Group (Bundy, 1958; Stein, 1983; Goff ward thickening of the Tesuque Formation of just west of the Cerro del Pino dome (Goff et al., et al., 2005b). All layered units dip 5°–15° to the the Santa Fe Group (19–13.5 Ma) beneath the 2005a), which may have also vented along this east and are altered to epidote rank. The well- La Grulla Formation is particularly pronounced. fault. The Canovas Canyon Rhyolite plug at sorted quartzose sandstone, which superfi cially Lavas on the La Grulla Plateau in the north- Ponderosa and a younger Paliza Canyon For- resembles a roof pendant, is locally metamor- western JMVF erupted over a relatively short mation dacite that laps across the Jose fault are phosed to quartzite and is cut by several dikes interval of time, starting at 8.75 Ma with thin not deformed by the fault (Osburn et al., 2002; related to the Bland stock. The sandstone was fl ows intercalated with Santa Fe Group sedi- Kempter et al., 2004). apparently deposited at ca. 10 Ma in a small ments. The activity evolved to more voluminous Many of the oldest Paliza Canyon Formation basin in the evolving Rio Grande rift. The white basaltic to andesitic eruptions at Encino Point basalt and trachyandesite fl ows in the south- sandstone, which deserves considerably more with most of the lava fl owing to the northeast. western Jemez Mountains between Borrego scrutiny, disappears to the east across the down- Subsequent eruptions were south and east of the Mesa, Bear Springs Peak, and Paliza Canyon to-the east Bland fault and other north-trending older La Grulla Plateau centers, giving rise to are thin (<3 m) and are separated by 5–10 m faults. The Bland stock consists of multiple more andesitic to dacitic eruptions between 7.7 of locally-derived, volcaniclastic conglomer- intrusions and dikes that were likely the source and 7.4 Ma. Although the La Grulla Formation atic sandstone and sandy conglomerate con- of the upper Paliza Canyon Formation trachy- is offset 670 m down-to-the-east, 2.8–3.0 Ma taining well-rounded boulders and <1-m-thick andesite to dacite fl ows exposed on surrounding basaltic andesite and dacite lavas that fl owed Canovas Canyon pyroclastic-fall deposits. The ridge crests. North of the Bland stock, a series of across the Cañones fault zone are generally not thick volcaniclastic succession is interpreted to E-W–trending monzonite dikes cuts Paliza Can- offset. The Garcia fault located 3 km east of the represent a persistent 9–10 Ma fl uvial system yon basalt in upper Bland Canyon. The source Cañones fault zone displaces a 3.8 Ma dacite by on the west side of the Bear Spring Peak–Tres of these dikes is not known, but they probably 80 m, and the Madera fault 10 km to the east Cerros–Canovas Canyon Rhyolite centers that originate from an igneous center down-faulted to offsets 5.6 Ma basalt by 11 m (Fig. 3; Koning was periodically disrupted by lava fl ows erupted the east, and now covered by the Bandelier Tuff. et al., 2007a). Variations in the thickness of rift- from unidentifi ed vents to the north. The sedi- In southern Medio Dia Canyon, yet another set fi ll sediments and offset of lava fl ows of differ- ments and fl ows were subsequently tilted to the of monzonite dikes cuts Paliza Canyon mafi c to ent ages imply high displacement rates across southwest, and then the sequence was capped intermediate composition rocks, and apparently this fault zone in middle and late Miocene time by relatively flat-lying 8.9–9.1 Ma (Justet, radiates from a small, shallow monzonite plug and a progressive decrease in displacement rates 2003) Paliza Canyon Formation trachyandesite exposed west of the canyon (Goff et al., 2005b). during late Miocene to Pliocene time. (Kempter et al., 2003). While eruptions of intermediate to silicic Evidence for an episode of rhyolitic volcanism At about the same time, small basins with lavas (Rowe et al., 2007) continued in the that postdates the Canovas Canyon Rhyolite and southeast-fl owing fl uvial systems were develop- south-central to southeastern Jemez Moun- predates the peak of Bearhead Rhyolite activity ing in the area of what are now upper Cochiti, tains between 9 and 7 Ma, a new volcanic cen- was found during this investigation. A rhyolite Sanchez, and Capulin canyons (Fig. 4). The ter developed on the La Grulla Plateau on the dome dated at 7.6–7.8 Ma was mapped in the rocks consist mainly of debris, block and northwestern side of the JMVF. In contrast to south-central Jemez Mountains (Goff et al., ash, and hyperconcentrated fl ows and locally the volcanism along the southern margin of the 2005b). Rhyolitic pumice deposits that are 7.8– reworked ash beds (Lavine et al., 1996). Struc- fi eld that is generally younger to the east, the 7.9 Ma and >7.6 Ma were found in the north- tural uplift of St. Peter’s Dome since 6 Ma has La Grulla volcanic center formed to the west of ern Jemez Mountains on Polvadera Mesa and

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on Cerro de la Garita, respectively. Although mostly dacitic volcaniclastic deposits that con- distinct, with locations and durations that are a few scattered Bearhead Rhyolite domes are tain interbedded 8.4–9 Ma basalt fl ows (Brox- likely controlled by relatively short-lived epi- located throughout the southwestern and south- ton and Vaniman, 2005; Broxton et al., 2012). A sodes of fault activity. The 40Ar/39Ar dates, when central JMVF, including the two domes discov- signifi cant unconformity separates the Miocene coupled with detailed mapping of both JMVF ered during this study, the locus of Bearhead fan deposits from the overlying Pliocene Puye rocks and the Santa Fe Group, document at least Rhyolite activity was in the southeastern Jemez Formation in drill holes on the Pajarito Plateau. two signifi cant pulses of faulting, erosion, and Mountains, occurring primarily between 6.5 The fi nal phase of volcanic activity just prior deposition across the Cañones fault zone in the and 7.1 Ma (Justet and Spell, 2001). Erosion of to and slightly overlapping eruption of the Ban- northern JMVF during middle Miocene time the Bearhead Rhyolite domes is recorded in the delier Tuff occurred on the northern, southeast- and late Miocene time. As a consequence, the volcaniclastic Cochiti Formation in the southern, and southern margins of the fi eld along Santa Fe Group is ~300 m thicker on the hang- ern Jemez Mountains. Bearhead-age eruptions north- to northeast-striking faults. Bimodal ing wall on the east side of the zone compared to also occurred in the northern Jemez Mountains, volcanism migrated to the northern margin of the footwall to the west. including numerous dikes interpreted to be Bear- the fi eld with the eruption 2.8–2.9 Ma El Alto ACKNOWLEDGMENTS head Rhyolite in the northeastern margin of the basalt, 2.8 basaltic andesite of Cañones Mesa, Valles caldera (Gardner et al., 2006), a rhyolite and 2.1 Ma El Rechuelos Rhyolite (Bailey et al., This paper would not be possible without the efforts dome found in Cañon de la Mora, and a rhyolite 1969; Gardner et al., 1986; this study). The of the members of the mapping team who worked in to trachyte with a poorly constrained age of Cerros del Rio volcanic fi eld on the southeast- the Jemez Mountains during the STATEMAP proj- 6.51 Ma south of the Four Hills Center on the ern periphery of the JMVF is chemically related ect. We thank Steven Reneau, Cathy Goff, G. Robert Osburn, Charles Ferguson, Mike Rampey, Rick Law- La Grulla Plateau. Bearhead volcanism gener- to the Tschicoma Formation and overlaps the rence, Gary Smith, Scott Lynch, and Dan Koning for ally migrated eastward in both the southern and dacite in age (Thompson et al., 2006; Rowe their help in collecting the samples and discussing the northern Jemez Mountains along projections of et al., 2007). Thompson et al. (2006) found three interpretation of the results. Nelia Dunbar evaluated the Cañones–Canada de Cochiti fault systems. distinct pulses of activity in the Cerros del Rio the pumice chemistry using the electron microprobe. Conversations with David Broxton and David Sawyer A brief lull in volcanic activity occurred volcanic fi eld: (1) an early, large-volume, phase are gratefully acknowledged. Thanks to Richard Kelley between 6.5 and 5 Ma. Dacitic volcanism incor- that consists of 2.8–2.6 Ma fl ows of basalt, and Shannon Williams for their help with the maps porating a large crustal component (Rowe et al., basaltic andesite, and minor dacite, (2) a middle, presented in this paper. This work was done as part of 2007) migrated into the northeastern JMVF at smaller-volume phase composed of 2.5–2.2 Ma the New Mexico component of the STATEMAP Pro- ca. 5 Ma. The oldest Tschicoma Formation cen- basalt and andesite; and (3) a late phase that gram of the National Cooperative Geologic Mapping Program of 1992, and was jointly funded by the State ters are in the Sierra de los Valles, and then this erupted 1.5–1.1 Ma basaltic andesite and minor of New Mexico and the U.S. Geological Survey. We activity became more widespread at 3.5–2.2 Ma dacite that is intercalated with the Bandelier appreciate the support of Paul Bauer and J. Michael across the northeastern Jemez Mountains, Tuff. The Santa Ana Mesa volcanic fi eld on Timmons, program managers at the New Mexico stretching from west of Abiquiu to the Pajarito the southern periphery of the JMVF consists Bureau of Geology and Mineral Resources. We also thank the Valles Caldera National Preserve for allow- Plateau. Rowe et al. (2007) noted that the “east- of basalts erupted from structurally controlled ing us access to research the geologic history of this 40 39 ern dacites” of the Tschicoma Formation (Paja- shield volcanoes and cinder cones. Ar/ Ar special place. Thanks also to Lisa Peters, Matt Heizler, rito Mountain and Cerro Rubio) have lower Nb, ages of 2.6–2.4 Ma for the basalts have been and students who participated in age determinations 143Nd/144Nd, and 206Pb/204Pb compositions com- determined by Smith and Kuhle (1998a, 1998b) and mineral separations at the New Mexico Geo- pared to the “northern dacites” of the Tschicoma and Smith et al. (2001). chronology Research Laboratory at the New Mexico Bureau of Geology and Mineral Resources. David Formation (Tschicoma Peak, Mesa Gallina, and Broxton and an anonymous reviewer shared construc- Polvadera Peak). The lack of correlation of age SUMMARY tive comments that improved the quality of the paper. with chemistry and other factors suggests the dif- ference is due to the composition of the melted New fi eld data, geochemistry, and geochro- REFERENCES CITED crustal component (Rowe et al., 2007). 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