117º 00’ 00” 116º 52’ 30” 116º 45’ 00” 116º 37’ 30” CAETANO CALDERA AND RELATED ROCKS Ts? ��� Tbm? �s 35 Pzrm CORRELATION OF MAP UNITS ������ Pzrm ���� 45 s Tcic Carico Lake pluton (Eocene)—Carico Lake pluton consists of 50–60%, 1–5 mm � � � T Pzrm � � 35 L phenocrysts of smoky quartz, sanidine, plagioclase and 2–3% biotite and � � Pzrm Pzrm ��� U s� � A Pzrm Qp Qal Qaf QUATERNARY hornblende in a microcrystalline quartz-feldspar groundmass. Scattered sanidine Tcs ��� Qaf Y � F � � � Tad � 45 s Tbm? Ts E � phenocrysts are as much as 2 cm long. Small miarolitic cavities are common. � � � � � L Tad Pzlc � 40 39 Tad � PLIOCENE 40 � � L Locally flow banded. Intrudes and deforms Caetano Tuff. Sanidine Ar/ Ar � � � s � � � � � Figure 14 � s � � cross-sections only � Greystone QTs �������� Horse A 30 x mine age is 33.78 ± 0.05 Ma (John et al., 2008). l l Tad 06DJ13 E V Mountain N l l l Tcir Redrock Canyon pluton (Eocene)—Strongly altered fine- to medium-grained l 35 Tct? O l Tad l Pzlc T Tbm? Qaf Pipeline pits l l S granite porphyry containing about 30% phenocrysts of rounded smoky quartz Wilson 26 Y l and dumps 21 l 50 Pass NEOGENE Tcb E (2006) and altered sanidine and plagioclase in a felsite groundmass now altered to R Ts R Tob 44 MIOCENE Tmr Qaf Qaf G Gold kaolinite and quartz. Undated but presumed to be late Eocene. Intrudes and 70 E Acres 35 T Tcm 40º 15’ 00” hydrothermally alters Caetano Tuff. D Tcl 33 Tcs CJV2 40º 15’ 00” Tcs 13 Barite N Pzrm Tb Tci R Caetano intrusive rocks, undivided (Eocene)—Small ring-fracture intrusion in Tad Tbm pit E Tcl T O northwestern Carico Lake Valley is a fine- to medium-grained porphyry with Tcs Tad L Qaf C U C T Qaf Unconformity A sparse white K-feldspar phenocrysts as much as 1 cm long. It consists of about A Tad L Qaf S F U K E A 45% phenocrysts of plagioclase, K-feldspar, and dark-gray quartz and 3% biotite F Tad Tcs d R Qaf W K 24 Ts and sparse hornblende in a microcrystalline groundmass. Small intrusion 2 km i E Ts l C Tcs s l l l l E o l Tbm c OLIGOCENE northwest of Carico Lake is fine-grained granite porphyry containing about l C ? n Qal R l l C A Tcu 25–30%, 0.1–3 mm phenocrysts of rounded smoky quartz, sanidine, and b 44 42 66 Tcs N plagioclase, and 1-2% biotite and hornblende in an aphanitic groundmass Tcu 40 l 40 S l N CENOZOIC CT120 Y S containing abundant miarolitic cavities. Both intrusions are undated but 46 O Tcs l 67 l Tbm O Tcs CT107O Y Tcb M N 40 presumed to be late Eocene. 50 30 Tci A N 46 CT116 C Y 05DJ27 Pzrm Tct Caetano Tuff, outflow sheet (Eocene)—Densely welded, crystal-rich rhyolite CT121 68 Tcu Qaf 46 C E 30 an Tad CAETANO CALDERA ash-flow tuff identical in composition and age to intracaldera Caetano Tuff (unit Tad y Ts? o Qal n � � Tcl 55 65 � A’ 60 36 � L Qaf � Tcc). Forms densely welded, reddish weathering ledges with up to 250 m Tcl s Tad H03-94 18 62 Cortez Tog Tog � Tcu 40 39 V A L L E Y � L � Ts? 50 PALEOGENE composite thickness. Black vitrophyric zones locally present. Sanidine Ar/ Ar � � l l l 60 47 �� Tcu �� Tcs 40 Tcu 30 � A s ages are 33.83 ± 0.05 and 33.75 ± 0.06 Ma (John et al., 2008). CT108 K Tcl � Tcs C Tbm 40 V 43 O Tcb Caetano Tuff, breccia (Eocene)—Mesobreccia and megabreccia dominated by 28 Tcl Pzlc R 53 Tcir 77 Tcb 41 Tcs D Tcir Tct coarse clasts of quartzite and chert. Mesobreccia is massive to thick bedded, E Tcu 15 Cortez R 70 Tcs? T EOCENE B Qal L quartzite-dominated breccia containing clasts up to 2 m in diameter, mostly 37 AU 31 Tcl Qp F MILL CANYON STOCK 62 61 75 25 Tcl matrix supported. Matrix varies from tuffaceous to finely ground quartzite. Also 45 Tcu Rocky 15 44 ? Figure 15 77 51 Pass � Tcic includes matrix-supported, quartzite-argillite pebble layers and sparse interbeds � T � Tci � Tbm L Ts Tcic � 25 Jgr � 64 Tog? Qaf T Tor � Tcu U Qaf � of volcanic sandstone and tuff. Probably deposited by rock falls and debris N 6 Tad? Tbm? H05-62 Ts � E � A s C 20 F 24 Pzlc Tcic � 21 Tcic S � flows, and possibly by fluvial processes. Megabreccia is composed of individual 45 � Tcm 49 20 � Tcic � E � Tcu � R Tor � Tb 05DJ27 blocks up to 50 m in diameter, mostly of chert or quartzite, but also Eocene R Cortez � Tcc � 45 55 10 C s Tbm Tcir Tci 41 39 Hills 30 � H03-96 H03-84 20 � (35 Ma) rhyolite in the northeastern part of the caldera (probably equivalent to E Pzrm � � l � 40 l Tbm � T � 37 Tor Tob l � L l � 30 20 � Tor), and composite areas of blocks up to ~1 km across, locally with a E V Tcir U � Tbm Mount � 75 l l Pediment l l � l 60 A l N l l Horse l x I Tcl l � F 35 � Tenabo � O tuffaceous matrix. Tcu � Canyon � � T 87 Tcu 73 � � 63 R s Tcu l DC99-15 S Unconformity 47 Tcb l Tcu Tcl Caetano Tuff, upper intracaldera unit (Eocene)—Multiple, thin, cooling units of Qaf � 47 Y 15 � H03-82 � S 334m � � 30 Tcic E 37 � S 40 � 30 � Tmr � Tcu Tcic poorly welded to moderately or (rarely) densely welded ash-flow tuffs locally s MESOZOIC R A l Tcic l 00DJ34 37 P � G Tbm Tcir � JURASSIC � Ts 20 45 � Jgr interbedded with coarse conglomerate, sandstone, and fine, platy tuffaceous 40 � � 6 35 Tbm � � ? Ts Tcl � Qaf Tbm � l s B’ Tbm 25 siltstone. Generally forms pale or banded slopes punctuated by thin ledges of l Y 40 � 30 � Tcir K � � 25 � more resistant welded tuff. Tuffs commonly contain angular fragments of 25 Tor C � 35 Tcs? � Pzh Tcl � 21 O � Tcu l s 45 l 20 R Ts densely welded lower Caetano Tuff up to 1.4 m in diameter and locally contain 85 � 47 Pzlc Qaf � Tbm 80 45 T T � 31 30 � 90 64 �����s���������s� L � L � hornblende-pyroxene andesite and Paleozoic fragments to 15 cm. Poorly to l GOLCONDA THRUST � 25 l U � U 40 � 30 Tcc � A s Qaf 20 A 80 99DJ80 moderately welded tuffs are characterized by distinctive orange pumice F 69 � F Tcc 25 � 23 Tcl 38 50 45 l Tcl � l Pzo � Carico 30 15 � Qaf Tcl � 33 fragments. Up to 1000 m thick; base of unit defined as a prominent welding � 62 45 Ts � T Tbm C Lake � L 40 s CT101 Pzrm H 37 U Tcc Tcu 20 10 l l 25 � PALEOZOIC break at the top of the lower unit (Tcc), which generally forms a conspicuous � C A Tcl CT102 35 � Unconformity F 38 Figure 19 50 25 � 40º 07’ 30” 37 � Tcu Qaf N 26 25 l � 40º 07’ 30” 72 Tad l 60 25 � � slope break marked by a vitrophyre or several meters of conglomerate or A � 44 Z T 75 35 � s L Tcc 41 15 30 R 39 E Tcs 5 43 43 30 � U Elephant l sandstone. � l 45 9 45 T Pzrm x � A Tct Tcc 29 � E Tbm F 32 H03-88B � Head R � Tcl � l 40 30 52 42 Compound cooling unit of l � Caetano Tuff, lower intracaldera unit (Eocene)— 37 50 O � 27 O l 25 32 s D 35 l 30 S Tct Qal N 25 Qp A 40 40 �����s���������s� C � 50 l A ROBERTS MOUNTAIN THRUST l l l Tbm? � k l E 30 Qal densely welded, crystal-rich, rhyolite ash-flow tuff, containing about 35–50 50 l n � i T 40 � 30 50 E E H s Tub Spring � 25 E � Tog a 50 25 � E T � l l B A l volume % phenocrysts as much as 5 mm in maximum dimension. Quartz, � 34 L 40 25 l R � Tcu s Pzlc 55 C E Tcu U 30 Tcl C � A 60 � sanidine, and plagioclase form >90% total phenocrysts. Distinctive quartz Tcu Ts Caetano n Tbm � i F � 37 Tcl 45 40 � R 16 T b � x 70 Ranch � 46 a l Ts 50 � Qaf 35 N l � phenocrysts are dark gray to black (smoky) and partly resorbed. Total mafic N 48 s C S I 10 35 50 A Qaf T 35 l l � S 50 A 40 � H l L A K E L Mount l Pzo x � T l l T mineral content generally <4 volume %, consisting mainly of biotite with minor � 40 G O � U P L 60 � l Tbm N l � l Tad Caetano l Tcl � Pzrm E A M � U U � C’ 29 e 35 40 L s F opaque minerals and locally trace hornblende. Euhedral allanite crystals as much n Pzrm A O 28 R H03-89 E 23 o 70 F 11 M t 35 Tcu 45 35 48 l S as 1 mm long, apatite, and zircon are common accessory phenocryst phases. Qaf 80 l E 27 R D 21 9 A 60 Tcu? 45 Tct 48 42 28 20 l l Tad Strongly flattened pumice fragments generally are crystal rich and contain Pzrm N 28 30 60 I S l l 30 Tcl 40 l B Tad l l 37 l l l phenocryst assemblages similar to the matrix.