Document 10907270
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NEW MEXICO BUREAU OF GEOLOGY AND MINERAL RESOURCES A DIVISION OF NEW MEXICO INSTITUTE OF MINING AND TECHNOLOGY 107°0'0"W 106°57'30"W 315000 316000 317000 318000 106°55'0"W 319000 320000 321000 322000 af 106°52'30"W 323000 324000 325000 326000 3750000 3750 000 Tpfn Qa Qa u Qp Qa Tpfn Qvn4 o Tb Qvn5 Qvn4 fn Tp Qvn4 Qv n 4 Qc Qvn3 Qvn4 af Qvn2 Qvn3 Tpfb Tm Qa QTsp? Qvof Qv n3 QTsp af QTsf Qa 3748000 Qc Qa 3 vn Q af af Qv n2 Disturbed 3 Qa Qpu Qv n Tm Qvn3 Gravel pit Qv n3 QTsf n Qv Qc Qvn3 Qvn2 Qvn 3 3747000 QTsf 3748 000 Qvn4 Qc QTsf Qv n Qv n Qv n4 Qvn2 Qc Qpu Qa Qa Qvn3 QTsf af Qa Tm Qpu QTsf n Qv af 1 11 5 21- 25 28-99 09 34- 1 30- 11 0 11 3 33- 94 26-96 11 0 12- 8-1 01 11-1 05 120 - 12 15 -1 33 13-100 111 20- 30-10 11 4 1 20- 11 4 13- 92 10 -1 31 12 0-90 26 -1 23 0 7-11 31 16- 94 16-90 24 -1 05 10-1 14 20 8-1 -1 11 2 6-1 19 6-1 02 Qvn 19- 7 Tp e 3741 000 53 9-87 6-1 04 af 6 8-1 01 12- 11- 1 09 12 11-96 11 -1 25 11 6 15- 4 26-10 12- 94 4-278 10 -1 24 13-1 11 -1 27 t3 13-93 Tp 111 15- 5 29- 94 9 - 11 11 4 13- 05 t2 Tp 18-90 23- s Tp 22 31 -1 15 2 af Tpa Qae 33°47'30"N 31 -1 1 13 4 10 Qae 9- 3740 000 af 3-3 56 Qae Qvof? Tpa e Qvs2 7-1 66 Tpa Tpa Tp e Qt af Tp a a Qt Tp Qt QTsp Tpe Tp Qae Tpa Qae Tpa af Qae QTsf s Qv 2 QTsf QTsp 46 Tpa Tpa Qvs2 Tp s s2 vo Q Qv Qc f Qc QTsf Qvof Qc 1 Qvs 3 - 15 Tps 0 10 Qc Qvof Qa Qvof Tps Qa Qc Tps af Tps Qc Qf Qae 4 -1 5 3739 000 Qae 5-1 Qc 2-1 01 23 7-1 0 26-10 11 4 Tp i 11 4 19- 26- t1 Tp 12- 94 11 0 19- 6 1611 - 11 9 13-96 20-78 a 25 af 3-5 -1 25 Tp Qa e a 13 BDA NWR HQ 4 11 5 Qa -5 16 10- 66 06 Qf 18- 12- 86 27-1 47 14-80 0 e Qa 1 5- 16-81 Qa e Tp 2 24-10 s 5-87 Qvof 1122 Qc 3738 000 Qa QTsf Qa Qa Qvof of Qa o Qv Qvot af af 2 af Qa c vs Q 1 3736 Q Qvof Qai af af Qvof Qvof 3737 000 Qpu Qpu Qa Irrigation ditch Qf Qc Qvof Qv of Qa Qpu af af Qvof Qpu Gravel pit Qai Qai Disturbed alluvium Qa af af Qai af Qai Qai 2 af Qvof Q vs Qai ai Q Qv s2 af s Qv Qa Qa af Qvs2 af Qa t af Qc 2 Qvs2 Qa af Qv s Qvof Tpa Qa Qvs2 Qt f o Qv Qv o af af af af af a Q af f Qvof Qc Qa Qc Qvof Qc af 2 Qvs Qvof Qvof 3737000 af af f Qc Qvot Qa Qv af af af Tpe Qvs2 vo Qc Qc Qvof Q QTsf Qc a Q 1 Qvs1 Qa Qvof Qvof s Qv af Qvof Qvof Qvot Qvot Qvot Qc af 33°45'0"N000 3742 000 Qvof QTsp QTsf 2 Qvot Qvn3 af Qae QTsf QTsf Qvot Qa af Qvof? QTsp Qa Tp 5 a Qc af QTsf Qa 18- QTsf af 3738000 5 59 50 19- -5 QTsf 0 14 9- Tps QTsp Tpt1 Qv s 4 2- 7- 14 Qvs2 17-80 32-10 fs 16-78 s Qv QTsp af 1 QTsf 69 Tp Qa Qa Qa QTsf s1 Qv 1 Qc 09 QTsf 1 Qvs Qv s 2 - 62 26- 1 Qvs1 Q vs fs Qa Tp fs Qae af Td 16 6 a QTsp 3743 000 Qc Qvn3 Tpe Tp e 6-2 6-1 Tpa Tpt1? af -2 19 Qvn3 Qae 5 Qvn QTsf 56 QTsf Qvn2 Tpfs 12 4 5 8-1 -4 42 Qae Tp Tps Tp Tpe Qae QTsp 8-1 31 13 5- Qc Qa Q vs 4 QTsp Qa 3739000 -5 Tpt Tpt3 Tank af af Qa Tpt1 Tpe Qae QTsp 7-7 9 Tpt2 s Qv s1 Qv 4 -5 51 af QTsp -4 11-83 Qvs2 Tpt2 Tpt2 5-3 Qc QTsp TspTpfs Qvn2-3 8-7 QTsp QTsf 36 -1 11 Qa 0 QTsp QTsf 8-2 65 Tps Tpt1? 18 8- af af - 62 5 14 - 15 11 QTsf Tpfs 11 -4 4 Tpe 10-1 11 Tpt1 Tpt1? af 24 Tpt1 af af Qa Tpt2 Tpt3 8 Tps - 14 s1 Qv Qt Tpt3 Tm 5 af QTsp 24-183 25-7 0 14 Qvn 4 Qt Qt Tps Tps Tps Tpfs Tbt Tsp Tpfs Qvn3 Tps Tsp ps Qvn2-3 T 27-78 Qt - 61 af Qt af 3740000 15 5 11- Tp s Qt af Tpt1 af 18 1 Qvs Qa s2 Qv Tpt1 Tpt1 5 14 Tpt3 af 3741000 Td 3 -1 14 af Qvn3 Qvn3 Qvn3 Qvn4 Tpt1 Tpt1 33°47'30"N Tp Qvn4 s QTsp Tpt1 67 Tpt1 Td Qvs1 af Tpt2 af 1 Tpt1 Tpt1 Qvs1 - 60 Tpt1 Tpt1 fs 5 42 Td i t1 Qa 13 29- 14 17 Tp 9 Tsp Qvn3 Qt 3744 000 Qvn4 Qvn2 Tp 3 -1 19- 86 fs 2 18- 7 Tp Qvs2 3742000 Tp af Tpt1 Qt Qvn2 Tbt s Tp Tsp Qvn2 T Qvn2 Tp pfs fs 26- 7 3 Tps 61 12- 1 Td Qvn3 Tps -5 3743000 Ts QTsp QTsf Qt 13 Qvn2Tpi QTsp QTsp Qvn3 Qvn3 17 n4 Qv Tpt1 af 3 Tpfs 34-77 21-81 2 Qvs Tpt1 QTsp Tp Tps Qvn3 fs 37 -1 10 - 589 2139 Tpt3 Qv Qvn af Qvn1 3 n2 Qvn4 Qt Qvn2 Tp Tps 3745 000 Qvn5? QTsf p Tp i Qt Qvn2 Tsp Tpfs Qvn Tps QTsf Qt T afpfs af Qvn3 QTsp QvnTsp 2 Tpfs Tpfs Qvn1 Qt Qvs2? Tpt2 Tp s Qt Qa Td 33°50'0"N QTsf Tpfs Tpt3 Qvn2-3 Qvn1 Tpt3 17-81 3744000 Qvn3 Tpt3 QTsf Tsp Qa Tpfsaf Tpfs Qvn3Qa af 29-84 Tpt1 Qvs 1 3 3 22- 7 t3 Qpu Qvn5 QTsf -1 3 -1 Qvn1 Qvn1 Tpt2 QTsf QTsp 36 28 Qvn1 Qvn2 Qvn1 Tp t 39-90 23 Qvn3? Tm Tp Qvn1 44- 85 n2 Qv Qpu Qv n Qa Ts Qvn3 49 QTsp? Qa Ts Qvn3 af Tpt1 -1 23 Qvn1 3746 000 QTsf QTsf Qpu Tm Qvn1 Qv Qa n5 Qvn4 QTsp Ts Ts Qvn2-3 Qvof Qvn 5 Qvn3 QTsf Qa Tm Qvn4 Qvn5 4 Qvn QTsf 3746000 3745000 3747 000 Qvn4 Qvn4 QTsf Qpu Qa Qvn5 QTsf 33°50'0"N Qf Qvn4 QTsf Qc QTsf QTsf Qa 4 Qvn5? QTsf Qa Tm 2 af 4 Qa 3749 000 Qvof Qvn 3 QTsf Qc af Qt Qa Gravel pit QTsf Qvn2? Qvn5? Qvof Qvof Qvof Qvn3 Tbo Gravel pit Qvn 3 af Qa Qvof Qa Disturbed 3749000 pTu Qa QTsp Qvn5 pTu Tank af QTsp Tm 33°52'30"N Qa QTsf Tm Tm Qa Qai Tank Qvn3 Qf Tpfn af Qa Qai 3736 000 33°45'0"N 315000 316000 317000 107°0'0"W 318000 319000 320000 321000 322000 106°57'30"W 323000 Base map from U.S. Geological Survey 1981, from photographs taken 1972, field checked in 1975, edited in 1981. 1927 North American datum, UTM projection -- zone 13N 1000-meter Universal Transverse Mercator grid, zone 13, shown in red 1:24,000 1 MOLINO PEAK LUIS LOPEZ 0.5 FORT CRAIG 0 1 MILE SAN ANTONIO 1000 CIENEGA RANCH Indian Well Wilderness 324000 325000 0 1000 2000 3000 4000 5000 6000 106°52'30"W Geologic map of the Indian Well Wilderness quadrangle, Socorro County, New Mexico. 7000 FEET June 2010 SAN ANTONIO SE 1 Magnetic Declination August, 2007 9º 38' East At Map Center SAN MARCIAL 0.5 0 1 KILOMETER CONTOUR INTERVAL 20 FEET This draft geologic map is preliminary and will undergo revision. It was produced from either scans of hand-drafted originals or from digitally drafted original maps and figures using a wide variety of software, and is currently in cartographic production. It is being distributed in this draft form as part of the bureau's Open-file map series (OFGM), due to high demand for current geologic map data in these areas where STATEMAP quadrangles are located, and it is the bureau's policy to disseminate geologic data to the public as soon as possible. After this map has undergone scientific peer review, editing, and final cartographic production adhering to bureau map standards, it will be released in our Geologic Map (GM) series. This final version will receive a new GM number and will supercede this preliminary open-file geologic map. DRAFT by Richard M. Chamberlin 1 and Colin T. Cikoski 2 1 New Mexico Bureau of Geology and Mineral Resources 801 Leroy Place, Socorro, New Mexico, 87801-4796 http://geoinfo.nmt.edu NATIONAL GEODETIC VERTICAL DATUM OF 1929 New Mexico Bureau of Geology and Mineral Resources QUADRANGLE LOCATION 326000 106°55'0"W Open-file Geologic Map 201 2 Earth and Environmental Science Dept, New Mexico Tech 801 Leroy Place, Socorro, New Mexico, 87801 ccikoski@nmt.edu COMMENTS TO MAP USERS Mapping of this quadrangle was funded by a matching-funds grant from the STATEMAP program of the National Cooperative Geologic Mapping Act, administered by the U. S. Geological Survey, and by the New Mexico Bureau of Geology and Mineral Resources, (Dr. Peter A. Scholle, Director and State Geologist, Dr. J. Michael Timmons, Geologic Mapping Program Manager). New Mexico Bureau of Geology and Mineral Resources New Mexico Tech 801 Leroy Place Socorro, New Mexico 87801-4796 [505] 835-5490 http://geoinfo.nmt.edu This and other STATEMAP quadrangles are (or soon will be) available for free download in both PDF and ArcGIS formats at: http://geoinfo.nmt.edu/publications/maps/geologic/ofgm/home.html NMBGMR Open-file Geologic Map 201 Last Modified 21 June 2010 Tpe Popotosa Formation, eolian sandstone facies (middle to upper Miocene)— Poorly cemented, poorly to well exposed, light gray to buff, high-angle cross bedded, fine-grained sandstones; locally interlayered with minor planar bedded, pebbly (fluvial) sandstones (Tps-type) and some DATIL GROUP channel-shaped conglomerates (Tpa-type). Eolian beds are 1-10 m thick and steepest cross beds (slip faces) generally dip easterly. Fine sand grains Datil Group is all volcanic formations in lower part of the Mogollon-Datil volcanic pile that range from 32 to about 37 Ma (Cather et. al., 1994). Formation nomenclature is from Osburn and Chapin, 1983. QfYounger valley fill, axial-fluvial facies (Holocene to uppermost Pleistocene)— Floodplain and channel deposits of Rio Grande; consists consist mostly of aphyric cryptocrystalline rhyolite, fine-grained porphyry and oscillatory zoned plagioclase. Exposed thickness is 100 m. mostly of clay to sand. Near San Acacia this unit grades down to well sorted gravel at basal scour surface as much as 30 m below floodplain (McGrath (Oligocene)— Thw is comprised by densely to partially and Hawley, 1987). Intertongues with Qa. Thickness 0–30 m. Tpa Popotosa Formation, andesite-dominated conglomeratic facies (upper Miocene) — Light- to medium-brownish gray, conglomerates, con- Thw/Thb Hells Mesa Tuff, caldera wall facies (Thw) with megabreccia slabs (Thb) glomeratic sandstones, sandstones (Tps type) and rare thin bedded mudstones; along with a few intercalated eolian sandstone beds (Tpe type). The welded, light-gray to pale red, locally xenolith-rich to xenolith-poor, phenocryst-rich, quartz-rich, rhyolite ignimbrite. It locally contains abundant ancontain mostly angular to desite, schist and granite xenoliths. Spears-type conglomeratic megabreccia slabs (Thb), as much as 20 m thick, are present at the base. Lower half is Qa Younger valley alluvium, piedmont facies (Holocene to uppermost Pleistocene)— Active channel, low terrace and alluvial-fan deposits of latter are often exposed on steep sided cuestas, where difficult to show at map scale (e.g. Canyon Trail area). Conglomerates tributary arroyos; poorly sorted, non-indurated, gravel, sand, silt, and clay. Formed during last major episode of valley entrenchment and backfilling. subrounded pebbles to cobbles of varicolored andesitic lavas (porphyries), with moderately abundant orangish brown, finely vesicular, andesitic scoria strongly bleached and hydrothermally altered. Just north of the quadrangle boundary, a slightly altered, lithic-poor zone at the top of the unit yields a Thickness 0–30 m. single-crystal laser-fusion 40Ar/ 39Ar sanidine age of 32.06 ± 0.17 Ma (Chamberlin et al, 2004), which agrees (within analytical precision) with a mean and sparse rhyolitic tuffs. Rare red siltstone pebbles, occasionally with white reduction spots, were almost certainly derived from exposures of the Per40 Ar/ 39Ar age of 32.27 ± 0.20 Ma from 4 bulk sanidine determinations of the Hells Mesa Tuff (McIntosh et.al., 1991). Thw unconformably overlies mian Abo Formation, now found east of the Rio Grande. Andesitic boulders are locally present near Elmendorf. Paleocurrents are northwesterly. Mesa Tuff that overlapped Basal contact is generally gradational into Tpe. A latest Clarendonian depositional age (ca. 9-11 Ma) for Tpa is provided by a partial fossilized skele- Proterozoic schists and felsic porphyry at Chupadera Spring. Thw is interpreted as relatively thin (270 m) intracaldera Hells Qae Eolian sands and alluvium undivided (Holocene to uppermost Pleistocene)— Thin, fine-grained, sand sheets locally cover, or are mixed with, young alluvium in area near Canyon Trail. Found downwind of sandstone-rich bedrock (Tpe). Eolian sands also accumulate on the lee side of ton of an oreodont (Merchyus major major) found embedded in this unit about 500 m north of the Canyon Trail (Morgan et al., 2009). Maximum ex- an inner collar of the caldera formed by large volume removal and scarp retreat of precaldera rocks, through mass wasting, during eruption and colof Chupadera Spring. ridges. Thickness is 0 to 5 meters. posed thickness is 120 m. lapse of the Socorro caldera. Thw wedges out against Proterozoic schist at the inner (32.3 Ma) caldera wall about 1 km south South of the 32.3-Ma caldera wall, the Hells Mesa Tuff is absent throughout the southern Chupadera Mountains. Qai Incised alluvium (Holocene to uppermost Pleistocene)— Mapped where deep gullies (~3 m) are cut in young valley fills near the mouths of Tpt2 Popotosa Formation, medial tuff-dominated conglomerate facies with pumiceous sandstones (middle Miocene) — Medium to light gray Tw/Tws andesite of Willow Springs, porphyritic lava (Tw) and volcaniclastic sedimentary (Tws) facies (new name) (Eocene)— A 200-300 mtributary arroyos. Found near Elmendorf, in an area of ongoing uplift (CC’). Exposed thickness 0 -4 m. and light brownish gray conglomerates, conglomeratic sandstones, and minor reddish mudstones . Four discontinuously exposed pumiceous sandstone pur- pile of medium to dark gray, grayish red and dusky red, plagioclase-pyroxene andesite porphyry lavas (Tw) and locally interlayered, composibeds locally define the top and basal depositional contacts of this facies. Pebble to cobble conglomerates are dominated by subangular to rounded, thick Qc Colluvium (Holocene to Pleistocene)— Talus, colluvium, rock-fall deposits and some debris-flow deposits on steep to moderate slopes in plish to light grey, mostly crystal-poor, rhyolitic tuffs, with rare andesitic lava pebbles, rounded scoria clasts, and traces of basalt. Non-volcanic clasts tionally similar, volcaniclastic rocks (Tws) exposed near Willow Springs are here informally named the “andesite of Willow Springs” The volumetrithe Chupadera Mountains. A notable 25m-long train of large (3x3m) jumbled blocks derived from the Blue Canyon Tuff apparently represents a rock-are absent. Basal contact is conformable with Tpt1. Sanidine crystals from rhyolitic pumice, collected near crossing of I-25 and the Chupadera Peak cally minor volcaniclastic sedimentary facies (Tws) includes bouldery monolithic laharic breccias, varicolored debris flows, yellowish brown lithicavalanche deposit that must have recently crossed the Chupadera Peak trail area from north to south (train trends 350 at 0320406E/3745952N). In- trail, yield a 40Ar/ 39Ar age of 14.59 ± 0.05 Ma (Table 1). Field relationships and age spectra suggest this is the approximate depositional age of the rich andesitic tuffs and reddish argillized ash beds. As mapped, Tw consists entirely of porphyritic lava flows and Tws is comprised by porphyritic shown where colluvium pumiceous sandstone bed. Thickness ranges from 50 to 70 m . volcaniclastic rocks, with or without interbedded lava flows. Together these facies (and a nearby andesite dike, Tia) suggest het“andesite of Willow cludes gravelly slope wash on erosion surfaces cut in poorly consolidated upper Cenozoic deposits in Socorro Basin. Primarily masks underlying map units. Widespread colluvial veneers on dissected piedmont slopes (QTsp) are generally not delineated. Usually–3 0.3m thick, Springs” was emplaced on the intermediate to distal slopes an andesitic volcanic center (e.g. composite volcano). Two referen ce sections are recomas much as 10 m thick. Tpt1 Popotosa Formation, basal tuff-dominated conglomerate facies (middle Miocene) — Light gray to brownish gray pebble to boulder con- mended for Tw. At 1.2 km west of Willow Springs, about 60 m of porphyritic lavas conformably overlie fluviatile andesitic conglomeratic sandstones glomerates with few interbedded pebbly sandstones and rare thin mudstones; generally poorly cemented and poorly exposed. Conglomerates are of the Spears Formation (Ts) and conformably underlie the Blue Canyon Tuff (Tb) with another 5 m of lavas above Tb, then truncated by a fault (from 0315800E/3742540N to 0315940E/3742960N). At 1.7 km SSE of Chupadera Peak approximately 230m of SE dipping andesite porphyry lavas are Qls Landslide blocks (Holocene to Pleistocene)— Large blocks of basalt lava, down slope from and apparently derived from a basalt-capped poorly to moderately sorted, with angular to rounded clasts, medium to thick bedding and rare cross-stratification. Crystal poor and moderately crystalrich, light gray to grayish red, welded tuffs derived from regional ignimbrite sheets (Osburn and Chapin, 1983) dominate the clast suite. Rare clast well exposed along a north-facing hillside and drainage line from 0320570E/3745290N to 0320990E/3745250N. Here Tw lavas conformably overlie cuesta (Tbo) east of Chupdera Spring. 0-10 m thick. types, such as basaltic andesite with sparse iddingsite, occur near the base of this unit and andesitic porphyry to scoria are present toward the top. Boulthe Chupadera Wilderness Tuff and are paraconformably to disconformably overlain by the La Jencia Tuff. In both reference sections the andesitic to 20der beds are well exposed about 300m south of the Chupadera Peak trail (0321231E/3745059N). Basal contact is generally poorly exposed and in- lavas tend to become more phenocryst rich and coarser grained up section. Coarse grained porphyries near the top of the section contain up40 Qt Terrace alluvium, undivided (latest Pleistocene to Holocene)— Narrow terrace gravels along some larger arroyos at approximately 2, 3, and 6 meters above the active channel. Thin deposits (0-3m) consist of poorly sorted, angular to rounded, cobbly gravels to pebbly sands with clast ferred to be a disconformity with tens of meters of erosional relief at the base near Chupadera Spring and the Chupadera Peak trail. Exposed thickness phenocrysts dominated by clear to whitish tabular plagioclase (3-7mm) and moderately abundant prismatic black pyroxene of similar size. Flows are lithologies from upstream sources. is 200 -380 m. about 3-20m thick and locally vesicular (or amygdaloidal). A reference area for Tws is located along both sides of a drainage and subdivision road about 2.4 km NW of Willow Springs (from 0345880E/3744850N to 0316040E/3745360N). Laharic breccias, debris flows and lithic tuffs are well exposed here and unconformably overlain by La Jencia Tuff, and the base of Tws is not exposed here. The andesite of Willow Springs contains the 33.9 Qvn Older valley alluvium, piedmont facies, north (middle to upper Pleistocene)— Inset terrace and alluvial-fan deposits of east flowing tribuBasalt Flows in Popotosa Formation tary arroyos associated with five episodes of valley entrenchment and backfilling (Qnv1 to Qvn5, oldest to youngest respectively); mapped only northTbt Basalt of Broken Tank (upper Miocene)— Moderately widespread (San Antonio to Socorro) aphyric trachybasalt flows interbedded in upperMa Blue Canyon Tuff, suggesting it is mostly of upper Eocene age (ca. 35-33 Ma). Age determinations that are pending may provide additional conblack to dark red- straints. The andesite of Willow Springs may be coeval with the lithologically similar Rubio Peak Formation in the Hillsboro area (Clemons, 1979) or of the BDA fault. Poorly sorted, angular to rounded, bouldery to pebbly gravels, gravelly sand and muddy silts were derived from the Chupadera Popotosa Formation on flanks of the Chupadera Mountains. Singular flow about 1.5 km NW of the BDA visitors center ranges from dish brown, aphyric to very phenocryst poor olivine basalt with a distinctive ophitic texture, as viewed in thin sections. Outcrops are mostly massive the andesite of Dry Legget Canyon near Reserve (Ratté, 1989), but lateral continuity with these remote lava piles seems unlikely Mountains. Sparse schist clasts are notable east of Chupadera Spring and red rhyolite clasts are abundant east of Chupadera Peak. Mostly reddish and –240m. with sugary diabasic cores and local vesicular zones; some propylitic alteration occurs at south end of outcrop belt. Groundmass concentrate from this non-indurated, but uppermost beds are locally cemented by pedogenic carbonate horizons 0.1 m to 0.6 m thick. Thickness Tbt outcrop yields a 40Ar/ 39Ar plateau age of 8.57 ± 0.26 Ma (Table1). Thickness is 0- 8 m. Tc tuff of Chupadera Wilderness (new name) (Eocene) — A 20-30m thick, pale red, poorly to moderately welded, moderately phenocrystQvs Older valley alluvium, piedmont facies, south (middle to upper Pleistocene)— Inset terrace and alluvial-fan deposits of tributary arroyos rich, relatively biotite rich, moderately lithic rich, dacitic ignimbrite is here informally named for key marker exposures in the Chupadera Wilderness 1 percent, small to medium size about 2 km SE of Chupadera Peak. A reference section, about 500m north of the Chupadera Peak trail (0321418E/3745694N), exposes about 25 m of Basalt of Olney Ranch (upper Miocene). Medium to dark gray, phenocryst-poor, trachybasalt with about–4 associated with two apparent episodes of valley entrenchment and backfilling; mapped only south of the BDA fault. Poorly to oderately m sorted, angu- Tbo Yo unger deposits south- phenocrysts (1–4 mm) of plagioclase and greenish olivine; latter is locally altered to red iddingsite. Porphyritic basal zone is 6-10 m thick and grades medium reddish brown weathering dacitic ignimbrite conformably overlying a pale orangish gray, poorly welded zone in the top of the Blue Canyon lar to rounded, sandy to bouldery deposits associated with graded surfaces that project well above the Rio Grande floodplain. east of Willow Springs (Qvs2) contain a mix of light grey tuffs and dark gray andesites. Older fan deposits near Tiffany Canyon (Qvs1) contain crystal upwards into dense core of fine-grained diabase with rare phenocrysts of plagioclase. Two samples of Tbo collected in the Luis Lopez quadrangle, just Tuff (Tb) and conformably underlying a massive, grayish red, phenocryst-rich andesite porphyry lava typical of the andesite of Willow Springs (Tw). About 3-4 m of section below the dacitic tuff is covered. Tc is characterized by moderately abundant phenocrysts (5-10%) of whitish plagioclase (1-rich tuff clasts from the southeastern Magdalena Mountains. Exposed thickness 0-6 m. north of the IWW quadrangle, yield 40Ar/ 39Ar plateau ages of 9.64 ±0.12 and 9.71 ± 0.14 Ma (Chamberlin et. al, 2002). Mean eruption age is 9.67 ± 0.04 Ma (n=2). Cuesta-forming outcrop east of Chupadera Spring is about 6-18 m thick and locally underlain by red scoriaceous sandstone, suggesting 2mm) and 2-3% black biotite (1-2mm) with a trace of very fine (<0.5 mm) sanidine in a well indurated, partially welded, pale red matrix mottled with poor, pink pumice fiamme the presence of a nearby vent. sparse varicolored small andesitic lithics and scoria fragments. Sparse (2-3%) slightly to moderately flattened, phenocrystQvof Older valley fill, axial fluvial facies, Rio Grande terrace deposits (middle to upper Pleistocene)— Light gray to light yellowish brown, define a subtle compaction foliation. South of the Chupadera Peak trail, Tc is locally truncated by overlying andesite lavas and also locally truncated well sorted sand and gravel. Well rounded to subrounded quartzite, mottled chert, granite, schist and moderately abundant volcanic pebbles (latter mostly well rounded) are typical of the axial-river deposits. Locally contains rare obsidian pebbles that are generally not seen in older river beds by the 28.9 Ma buttress unconformity associated with the late-stage wall of the Socorro caldera. Tc is discontinuously exposed above the Blue Canyon MOGOLLON GROUP (QTsf). 0-2m thick where unconformable on Popotosa Fm.; appears to thicken southward. Mogollon Group is all volcanic formations in upper part of the Mogollon-Datil volcanic pile that range from 29 to 24 Ma (Cather et. al., 1994). Forma- Tuff in the area west of Willow Springs. Tc is presently undated, but must be somewhat younger than the 33.9 Ma Blue Canyon Tuff; thus suggesting it is of late Eocene age. The tuff of Chupadera Wilderness is probably a minor volume local ash-flow tuff; it is not presently recognized outside the tion nomenclature is from Osburn and Chapin, 1983. southern Chupadera Mountains. Thickness is 0-30m. Qvot Older valley fill, piedmont to axial river transitional facies (middle to upper Pleistocene)— Reddish-orange muddy sands and sands flanking deposits of Qvof near Tiffany Canyon, locally gypsiferous. Basal contact not exposed, about 0-20m thick. Tlp La Jara Peak Basaltic Andesite, uppermost tongue (Oligocene)— Medium to dark gray basaltic andesite lava flows with sparse small phenocrysts of olivine altered to reddish iddingsite. Locally fills paleovalley cut in South Canyon Tuff. Tentatively correlatedwith the “basalt of Tb Blue Canyon Tuff (Eocene)— Basal zone about 30 m thick consists of light gray to light brownish gray, densely welded, moderately lithic Qpu Piedmont deposits undifferentiated (upper to lower Pleistocene)— Coarse debris flows and poorly sorted gravels, sand and mud deposited Madera Canyon” (Osburn et.al., 1981), dated at 27.1 ± 0.2 Ma (McIntosh and Chamberlin, unpublished data). Thickness 0– 20 m. rich (1-5%), moderately phenocryst-rich (15-20%) sanidine-rich, very quartz poor, rhyolite ignimbrite typically with sparse coppery biotite and cleaved glassy sanidine crystal faces as much as 5 mm long. Soft scoria fragments in the ledge-forming densely welded zone commonly weather out to on small-catchment, high-gradient alluvial fans at east flank of Chupadera Mountains. Contains buried soils similar to those in QTsp; but not demon-5 mm) strongly flattened crystal-rich pumice are strated to intertongue with QTsf. Probably represents locally continuous aggradation, equivalent to QTsp and older Qvn and Qvs deposits. Base not Tsc South Canyon Tuff (Oligocene)— Partially to densely welded, light gray, phenocryst-poor to moderately phenocryst-rich, pumiceous, rhyo-form 2-3cm wide “swiss-cheese” holes that lead to the false impression of poor welding. Small (2 exposed; locally 30-60 m thick. lite ignimbrite. Medium grained (1–3 mm) phenocrysts of subequal quartz and sanidine, with traces of biotite and plagioclase, increase upwards fromdifficult to see in the densely welded basal zone, especially where it has weathered to a dark brown to black patina, which can give it the false appearance of a mafic lava outcrop. Where well exposed north of the Chupadera Peak trail, the partially welded upper zone is about 30 m thick and weath5% near partially welded base to as much as 25% near densely welded top. Moderately crystal rich upper zone is absent south of Chupadera Peak trail, 40 Ar/ 39Ar age of 3 bulk sanidine separates is 27.55 ± 0.14 ers to a medium grayish orange; here it contains about 5-7% phenocrysts of sanidine (also up to 5 mm across) and sparse coppery biotite in a pinkish where it has been removed by Miocene erosion. Erupted from Mt. Withington caldera; mean Santa Fe Group gray matrix mottled with rare small andesitic lithics and medium gray aphyric pumice (or mafic magma clots?). The upper poorly welded zone is genIntermontane basin fill of the Rio Grande rift; regionally ranges from latest Oligocene to early Pleistocene (Chapin and Cather, 1994). As redefined by Ma (McIntosh et.al., 1991). Thickness 0- 30 m. erally absent near Willow Springs. Tentative correlation here is based on distinctive size and abundance of sanidine phenocrysts (Ratté et al, 1990) and Machette, 1978, includes the Pliocene and Pleistocene valley fill of the Sierra Ladrones Formation (of Machette, 1978), and latest Oligocene to late Miocene bolson fill of the Popotosa Formation in the central Rio Grande rift (Denny, 1940). Intercalated volcanic units are usually given formation Tlu/Tll Lemitar Tuff, upper and lower members (Oligocene) — Compositionally zoned ignimbrite (77–65 wt% SiO2) divided into a lower member lithologic similarity to well dated 33.9-Ma sanidine-rhyolite clasts in the Luis Lopez Formation moat fill about 5 km north of Chupadera Peak status (Osburn and Chapin, 1983). (Chamberlin et al., 2004). Source of widespread Blue Canyon Tuff is unknown; mean 40Ar/ 39Ar age of 2 bulk sanidine separates is 33.88 ± 0.06 Ma (Tll) of partially to densely welded, light gray, lithic-poor, phenocryst-poor (5–15%), high-silica rhyolite, and an upper member (Tlu) of densely –4 mm) phenocrysts of quartz, sanidine, plagioclase (McIntosh et.al., 1991). Thickness 0-60m; appears to be absent in southernmost Chupadera Mountains (south of 03741000N). welded, dark red, phenocryst-rich (30–45%), rhyodacite to rhyolite. Contains medium-grained (1 and minor biotite. Small (1–3 cm) phenocryst-poor pumice is moderately abundant–5%) (3 in lower member and phenocryst-rich pumice is sparse in Upper Santa Fe Group 20 Ts Spears Formation (Eocene) — Light gray to greenish gray andesitic fluviatile conglomerates and conglomeratic sandstones dominated by QTs Sierra Ladrones Formation (lower Pleistocene to lower Pliocene)— Late-stage basin fill of the Rio Grande valley characterized by an axial upper member. Lower member fills paleovalley cut through Vicks Peak Tuff and La Jencia Tuff near the Chupadera Peak trail. A thin interval (0m) of poorly exposed tuffaceous conglomerates and sandstones is present at the base of Tll near Chupadera Spring. Erupted from Hardy Ridge caldera varicolored andesitic clasts. Sparse, but widespread, light-gray crystal-rich hornblende-plagioclase dacitic clasts, with abundant large (2-4 mm) black -fluvial facies (ancestral Rio Grande) and intertonguing piedmont facies (large alluvial fans) derived from adjacent mountain ranges. Axial-river deposits are as much as 330 m thick in a municipal water well near Socorro (Chamberlin, 1999). (Chamberlin et. al, 2004); mean 40Ar/ 39Ar age of 2 bulk sanidine separates is 28.18 ± 0.16 Ma (McIntosh et.al., 1991). Thickness 0-60 m. hornblende crystals, are distinctive of Spears conglomerate beds in the southern Chupadera Mountains. Imbricated clasts indicate southwesterly to southeasterly paleocurrent directions. Thin to thick beds are dominantly clast supported, in contrast to the matrix supported debris flows and laharic Tv Vicks Peak Tuff (Oligocene) — Light gray to pale red, pumiceous, phenocryst-poor, densely welded rhyolite ignimbrite. Large, moderately breccias in the volcaniclastic sedimentary facies in the andesite of Willow Springs. Rare red laminated siltstone clasts in lower beds SE of Coyote QTsf Sierra Ladrones Formation, axial fluvial facies (lower Pleistocene to lower Pliocene)— Mostly well sorted, light-gray to pale yellowish abundant (5-10%), strongly flattened pumice fiamme, as much as 20 cm long, are distinctive. Sugary looking vapor phase minerals also commonly Springs suggest unit may unconformably overlie the Permian Abo Formation near here. Spears sandstones unconformably overlie Pennsylvanian brown, sand and well rounded pebbly gravel lenses; locally showing southerly paleocurrent directions. Gravel lenses containll-rounded we to 3 phenocrysts of sanidine, sparse quartz, and traces of biotite. Mafic acci- Madera Group limestones near Chupadera Peak, and may conformably overlie a thin limestone cobble conglomerate unit tentatively correlated with subrounded clasts of quartzite, mottled chert (Pedernal type), granite, schist and variety of volcanic rocks (most of latter are commonly well rounded).form a light gray rim around the flattened pumice fragments. Contains–5% Rare exposures of greenish mud (overbank deposits or abandoned channel fills) and reddish-orange muddy sands (distal fan deposits) are present. dental lithics are small and rare to absent. As much as 10m of tuffaceous sandstones are present at the base of the map near unit Chupadera Spring. Tv the Baca Formation. Maximum exposed thickness south of Coyote Springs is 190m. Age of Ts is locally bracketed between 33.9 MaBl ue Canyon Tuff Poorly exposed and often mantled by thin colluvium. Near Burro Well, approximately 2 m of uppermost QTsf beds lie in slight angular unconformity is 30-70 m thick on footwall of the Chupadera fault and at least 120 m thick on the hanging wall block, which implies fault was active prior to 28.7 and middle Eocene (?) Baca conglomerate beds. on Popotosa Fm. A 0.5º southward tectonic tilt on the river beds implies they are preserved in a southward thickening wedge, at about 8m /km (Section Ma. Erupted from Nogal Canyon caldera; mean40Ar/ 39Ar age of 3 bulk sanidine separates is 28.70 ± 0.06 Ma (McIntosh et.al., 1991). 0-120 m thick. C- C’). North of the BDA fault, QTsf may be as thick as 330 m. Cenozoic Intrusive Rocks Tj La Jencia Tuff (Oligocene) — Light gray, pale red and dusky red, phenocryst poor, densely welded to rheomorphic, rhyolite ignimbrite. Tj QTsp Sierra Ladrones Formation, piedmont facies (lower Pleistocene to upper Pliocene)— Reddish orange to reddish brown, poorly consolicontains sparse (3–5%) small (1-3 mm) phenocrysts of sanidine and quartz with traces of plagioclase and rare biotite. The basal densely welded zone isTim Mafic dikes (Oligocene) — Mostly dark gray to greenish gray, phenocryst-poor basaltic andesite dikes with sparse small phenocrysts of dated , volcanic-rich, angular to subrounded, conglomerates, conglomeratic sandstones, muddy sandstones, silty mudstones and unconsolidated equivacharacterized by medium sized (2-5cm), moderately abundant (5-10%) strongly flattened pumice fiamme. The upper half of La Jencia Tuff is typicallypyroxene in a fine-grained (diabasic) groundmass. Basaltic andesite dikes are 3-6m wide, strike NW and cut the La Jencia and Vicks Peak Tuffs. Tim includes one NW-striking, moderately phenocryst- rich minette dike (at 0316020E/3747520N) with about 10% phenocrysts of biotite and pyroxene in lents (e.g. gravels); generally fining to the east. Cobble to rare boulder gravels show lateral variation in clast lithologies indicating eastward transport a very densely welded zone of finely flow banded (rheomorphic) ignimbrite. Thin (1-2mm) white bands of smeared out pumice form a strong lineation from the Chupadera Mountains. Uppermost QTsp beds form a gently south tilted veneer (0-15 m thick), unconformable on Popotosa Fm., west of on the foliation plane. Secondary flow folds are common in the rheomorphic zone. On some paleotopographically high blocks, laminated fall deposits a black fine-grained matrix. These undated mafic dikes are compositionally similar to some well dated dikes of the Magdalena radial dike swarm 2438E/3745603N, re(MRDS; Chamberlin et al., 2009) and may be a relatively near source equivalent of the MRDS. Burro Well. Locally contains buried pedogenic carbonate horizons in area north of the BDA fault, where it is as much as 330m thick. (1.5 m thick) and light gray to beige partially welded zones are locally present at the base of Tj (0320182E/3745322N and 031 spectively). Erupted from Sawmill Canyon caldera; mean40Ar/ 39Ar bulk sanidine age is 29.04 ± 0.08 Ma (McIntosh et al, 1991), but a precisely dated pre-La Jencia lava dome suggests eruptive age is closer to 28.89 ± 0.06 Ma (Chamberlin et al, 2004). The La Jencia Tuff is as much as 400m thick Tia Andesite porphyry dike (Eocene)— Greenish gray, phenocryst-rich, andesite porphyry dike contains about 25% medium grained (2-4mm) Tsp Middle Santa Fe Group, piedmont deposits, unnamed transition unit (latest Miocene to earliest Pliocene?)— Poorly exposed, pebble northwest of a buttress unconformity (locally marked by a thin black vitrophyre) that defines a late-stage (28.9 Ma) topographic wall of the Socorro plagioclase laths and sparse large (4-5 mm) black pyroxene crystals in a very fine-grained lithoidal (cryptocrystalline) matrix. Near vertical dike is 15conglomerates, sandstones and rare mudstones. Conglomerates contain moderately-well sorted, subangular to rounded clasts of dominantly light gray welded tuffs mixed with rare rounded basalts and traces of vein quartz. Pebble imbrications indicate southeasterly paleocurrent directions. Sandstone caldera near Chupadera Peak and Willow Springs. On the 28.9-Ma caldera rim, southeast of the buttress unconformity, the La Jencia tuff is no more 20m wide and strikes ENE (080). Dike cuts Spears conglomeratic sandstone beds (Ts). Andesite porphyry dike is very similar tophenocryst–rich andeand mudstone beds found only at southeast end of the outcrop belt (in narrow graben on the footwall of BDA fault). Basal cont act not exposed, but is than 50-100 m thick and commonly fills narrow NW-trending paleovalleys. At Chupadera Peak and along its flanks, 60 m-high craggy cliffs mark an site porphyry lavas in the andesite of Willow Springs, which suggests they are coeval. acent Popotosa con- unusually thick and laterally restricted dusky red lithophysal zone in the basal densely welded La Jencia Tuff. The lithophysal zone occurs only where probably an unconformity on underlying Popotosa Fm. May represent a lower Sierra Ladrones piedmont facies, recycled from subj glomerates. Mapped separately from nearby QTsp beds due to distinctly different clast suite. Exposed thickness ~ 95 m. Tj overlies poorly welded moat-fill tuff (Tzt), which may have been water saturated in La Jencia time. Laramide Orogenic Deposit Qfh Younger valley fill, axial fluvial facies, historic channels (Recent) — River channels active prior to ca. 1950 (pre-conveyance channel) flowed along the west side of the floodplain. Present-day channels are forced to flow east of the conveyance channel. 33°52'30"N Qpu Post Santa Fe Group: Post-Santa Fe Group includes all surficial deposits inset into the Sierra Ladrones Formation and intermontaneTpfi Popotosa Formation, interbedded clast suite facies (middle Miocene)- — Narrow, down faulted (almost horse like) outcrop belts of consurficial deposits of middle Pleistocene to Holocene age. glomerate and conglomeratic sandstone show distinct interbedding of tuff-dominated and andesite-dominated clast suites. Tuff-rich conglomerate beds are more poorly sorted and coarser (cobbly) compared to interlayered, pebbly andesite-rich and scoria-rich beds. Paleocurrent directions are to southwest and to southeast. Basal contact is conformable with underlying Tps. Minimum exposed thickness is 95 m. Artificial fill (Recent) — Compacted fill, as roadway subgrades along Interstate 25. Thickness –6 0 m. A geologic map displays information on the distribution, nature, orientation, and age relationships of rock and deposits and the occurrence of structural features. Geologic and fault contacts are irregular surfaces that form boundaries between different types or ages of units. Data depicted on this geologic quadrangle map may be based on any of the following: reconnaissance field geologic mapping, compilation of published and unpublished work, and photogeologic interpretation. Locations of contacts are not surveyed, but are plotted by interpretation of the position of a given contact onto a topographic base map; therefore, the accuracy of contact locations depends on the scale of mapping and the interpretation of the geologist(s). Any enlargement of this map could cause misunderstanding in the detail of mapping and may result in erroneous interpretations. Site-specific conditions should be verified by detailed surface mapping or subsurface exploration. Topographic and cultural changes associated with recent development may not be shown. Cross sections are constructed based upon the interpretations of the author made from geologic mapping, and available geophysical, and subsurface (drillhole) data. Cross-sections should be used as an aid to understanding the general geologic framework of the map area, and not be the sole source of information for use in locating or designing wells, buildings, roads, or other man-made structures. The map has not been reviewed according to New Mexico Bureau of Geology and Mineral Resources standards. The contents of the report and map should not be considered final and complete until reviewed and published by the New Mexico Bureau of Geology and Mineral Resources. The views and conclusions contained in this document are those of the authors and should not be interpreted as necessarily representing the official policies, either expressed or implied, of the State of New Mexico, or the U.S. Government. Lower Santa Fe Group Tp Popotosa Formation (locally middle Miocene to upper Miocene)— Bolson fill of the Miocene “Bosque del Apache” Basin (east -tilted half graben) of the central Rio Grande rift. Locally subdivided into facies/members based on clast suites of volcanic-rich conglomerates, bulk grain size and bedforms that reflect depositional environments, general paleocurrent domains, and general stratigraphic position. Conglomer ates in the “upper Popotosa Formation” (informally defined) contain sparse to rare non -volcanic clasts derived from Paleozoic formations now exposed east of the Rio Grande. Maximum total thickness in Bosque Basin is about 2 km, near the Canyon Trail (A-A’). A corresponding total thickness within Chupadera uplift (Tptu below 9.7 Ma Tbo, near Chupadera Spring) is about 250 m. Tpfb Popotosa Formation, basaltic boulder bed (upper Miocene) — Boulder bed contains medium gray to black, massive to vesicular, subrounded basaltic boulders, as much as 0.5 m across, mixed with minor tuff cobbles and rare andesitic pebbles. Sparsely phyric olivine basalt boulders imply derivation from a nearby fault scarp of Miocene age that offset Tbo. Base not exposed, inferred conformable with underlying Tptu. Maximum thickness about 10m. Tz Luis Lopez Formation (Oligocene) — Heterogeneous post-collapse intracaldera fill of the Socorro caldera consisting of volcaniclastic sedi- Tba Baca Formation (Eocene?)— Gray limestone cobble conglomerates about 20 m thick; locally well exposed about 600m SW of Chupadera mentary rocks, pumiceous rhyolitic ignimbrites, basaltic to intermediate lavas and rhyolitic lava domes. Locally erupted vol canic units range from Peak. Unconformably overlie Madera Group limestones. Tentative correlation with Baca Formation suggests Chupadera Peak area was a Laramide highland in early Tertiary time. 0-20m thick. 30.2 Ma to 28.9 Ma (Chamberlin et al, 2004). Tzbr Luis Lopez Formation, upper rhyolite member (Oligocene) — Light brown, phenocryst-poor, flow-banded, lithoidal rhyolite lava with PALEOZOIC STRATA minor spherulitic zones. Contains sparse phenocrysts of plagioclase, sanidine and minor biotite with traces of hornblende sphene. and Steep flow foliations suggest a local vent near Table Mountain Tank. Exposed thickness is 100 m. A similar lava dome at Nogal Canyon is datedat 28.9 Ma IPm Madera Group (Pennsylvanian)— Gray, micritic, cherty limestone and minor shale beds; fossiliferous thin to thick bedded limestones are (Chamberlin et al, 2004). Derryian (Kottlowski,1960). Beds SE of Chupadera Peak are hydrothermally altered (silicified) and appear to be folded. 0-60m thick. Tzt Luis Lopez Formation, medial pumiceous tuff member (Oligocene)— Light gray, poorly welded, pumiceous, phenocryst-poor, rhyolite Mkc Kelly and Caloso Formations, undivided (Mississipian) — Basal pale red arkosic ignimbrite. Contains lithic-rich lenses dominated by andesitic fragments, Small rare fragments of crystal-rich quartz-rich Hells Mesa Tuff are also lo- sandstones of Caloso formation (~ 10m thick) overlain by gray to buff, micritic to bioclastic limestones and shales of the Kelly Formation (~10-20m cally present. Small (1–3 cm) aphyric to very crystal poor, white pumice lapilli form 15 to 30 % of rock. Pumice contains rare phenocrysts of plagio- thick). Basal sandstones are locally silicified. clase, sanidine and quartz and is commonly altered to clay. Medial Luis Lopez tuffs were erupted from Black Canyon vent area in northern Chupadera Tptu Popotosa Formation undivided, lower to upper, tuff-dominated facies (middle to upper Miocene)— Pebble to cobble conglomerates and Mountains (Chamberlin et.al, 2004). Mean 40Ar/ 39Ar age from two “single-crystal” sanidine determinations is 30.23 ± 0.05 Ma (Chamberlin et al, PROTEROZOIC ROCKS 2004). As much as 60m thick under Chupadera Peak; Tzt appears to wedge out against north-facing topographic wall (intermediate-stage caldera wall) sandstones within the Chupadera uplift near Chupadera Spring; locally capped by the 9.7 Ma basalt of Olney and cobbles of about 1 km south of Chupadera Peak. Small outcrop of Tzt, 3 km NW of Willow Springs, marks southern limit of Luis Lopez moat-fill deposits, which Proterozoic schists, amphibolites, felsic porphyry and granite are shown as mapped by S.C. Kent, 1982, with minor modifications. Thin aplite, pegmaRanch (Tbo). Light brownish gray conglomerate and conglomeratic sandstone beds contain abundant subangular to rounded pebbles rhyolitic tuffs with minor andesitic porphyries; tuff boulders are locally present. Gravel sizes generally fine upwards; paleocurrent directions are west-may represent a moderately permeable local aquifer (M. J. Darr, oral commun., 2007). Tzt is absent south of 28.9 Ma buttress unconformity. tite and carbonatite(?) dikes are not shown. Transposed lithologic units are highly variable in apparent thickness, and original bedding is not preserved (Bowring et al., 1983). Feldspathic and pelitic schists are interpreted to represent regionally metamorphosed (and essentially coeval) arkosic sanderly. Rare clasts of red siltstone (Abo type) can be found in float and poorly exposed upper Popotosa beds about 30 m below the basalt capped cuesta about 250m. Tzs Luis Lopez Formation, basal sedimentary member (Oligocene) —Purplish gray to medium gray andesitic debris flow deposits, andesite- stones and muddy siltstones, with minor interbedded mafic to silicic volcanics or shallow intrusives; all of which predate the locally foliated granite (Tbo) near Chupadera Spring. Basal contact is generally poorly exposed. Total thickness near Chupadera Spring (below Tbo) is porphyry (Bowring et al., 1983). rich conglomerates, sandstones and reddish mudstones derived from the southern topographic wall of the Socorro caldera. Rare sanidine-rhyolite clasts Tpft1 Popotosa Formation, upper, tuff-dominated conglomerates and sandstones (upper Miocene)- — Poorly exposed conglomerates, sandin Tzs conglomerates help distinguish them from andesitic conglomerates of the Spears Formation. Near Nogal Canyon, conglomeratic sandstones at 40 Ar/ 39Ar ages of 33.96 ± 0.10 and 33.90 ± 0.15 Ma (Chamberlin et. al, stones and rare mudstones on footwall of the BDA fault. Conglomerate beds are poorly sorted with angular to subrounded clasts of dominantly rhyoli- the top of this unit contain spherulitic sanidine-rhyolite cobbles that yield Xgn Gneiss (Proterozoic)— Quartz-mica gneiss and minor mica schists; forms relatively massive outcrops adjacent to granite porphyry west of tic tuff, sparse andesite porphyries and rare non-volcanic clasts. Paleocurrent directions are southwesterly. Uppermost beds are intercalated with the2004), demonstrating they are age equivalent to the Blue Canyon Tuff. Spherulitic clasts were previously interpreted as derived from rhyolite lavas Chupadera Peak. Gneiss may represent a syn-kinematic, contact metamorphic aureole adjacent to the granite. (Chamberlin et al, 2004). However, new map data imply they are actually clasts of densely welded Blue Canyon Tuff derived from the caldera wall basalt of Broken Tank (Tbt). Exposed thickness is 280 m. and rim, as now delineated southeast of Chupadera Peak. Andesitic conglomerates SW of Chupadera Peak contain rare clasts of Hells Mesa Tuff. Peb-Xg Granite (Proterozoic)— Pink to red, microcline-rich, massive to locally foliated, megacrystic granite porphyry. Zircons from exposure west Tpft2 Popotosa Formation, upper, tuff-dominated conglomerates and conglomeratic sandstones (upper Miocene) — Similar to Tpft1, but this ble imbrications in andesitic conglomeratic sandstones about 3 km NW of Willow Springs indicate northerly paleocurrents, suggesting correlation with of Chupadera Peak yield a U-Pb age of 1659 ± 3 Ma (Bowring et al., 1983), indicating a Paleoproterozoic age for the granite and older metasediments. unit is somewhat coarser (more cobbly) with greater proportion of andesitic and non-volcanic clasts. Exposed thickness is 70 m. Tzs. Near Chupadera Spring, Tzs wedges out southward against Proterozoic schists at the inner (oldest) topographic wall of the Socorro caldera (Eggleston, 1982). The top of Tzs is also truncated by a Miocene erosional unconformity here (base of Tptu). East of Chupadera Spring, the maximumXa Amphibolite (Proterozoic) — Amphibolite and mafic schist, may represent metamorphosed dikes where crosscutting felsic schists. Tps Popotosa Formation, fluvial sandstone facies (middle to upper Miocene)— Moderately to poorly cemented, massive (planar?) to trough preserved thickness is 180m. Xp Felsic Porphyry (Proterozoic) — Light colored rhyolitic porphyry, with 5-30% mesocrysts of alkali feldspar and minor quartz. cross bedded sandstones and rare channel-shaped conglomerates. Thin mudstones, with desiccation cracks, are locally common near the south end of outcrop belt. Conglomerates contain poorly sorted, subangular to rounded pebbles with a clast suites that range between tuff-dominated (with sparse Tze Luiz Lopez Formation, exotic blocks of Blue Canyon Tuff (Oligocene)-— Stratigraphically incoherent blocks of Blue Canyon Tuff at the andesite) and andesite dominated with abundant scoria (with sparse tuffs). Non-volcanic clasts are absent near the base but become notably present28.9-Ma (~1 Quartzo-feldspathic schist (Proterozoic) — Reddish quartz-feldspar schists ( 75-90% quartz and 0-25% feldspar) with minor muscovite, caldera wall, near the Chupadera Peak trail, are interpreted as ancient landslide deposits coeval with the upper Luis Lopez Formation. South Xq ones. Basal and upper of the trail, a 60 x 70 m wide slab (0320920E/ 3745440N) and 3x4 m block of Blue Canyon Tuff rest on andesite porphyry lavas (Tw). The strati-2%) in conglomeratic beds near the top. Paleocurrents are dominantly southwesterly. Locally contains a few thin eolian sandst biotite and chlorite. contacts are conformable. Exposed thickness is 320 m. graphically misplaced (anomalously above Tc) slab and block of Blue Canyon ignimbrite also clearly occur stratigraphically below a thin sheet of La Jencia Tuff , which marks the 28.9-Ma caldera rim. Slab is about 10 -20 m thick. Xm Mica schist (Proterozoic) — Gray muscovite-quartz-biotite schists; locally with minor garnet and staurolite(?).
