Stratigraphyandstructure ol the Klondike Hills, southwesternNew Mexico byMichael G. Rupert,State of ldaho,Division ot EnvironmentalQuality, Boise, lD, 83720,and Eusse// E. Clemons,New Mexico State Universi$, LasCruces. NM 88003 Introduction (scale1:62,500) of the CedarMountains (now One sample of the weathered granite yielded The Klondike Hills are in southwestem New called Cedar Mountain Range). Armstrong an Rb/Sr age of 1390* Ma (M. Shafiqullah, Mexico approximately 30 mi (48 km) south- (1970)focused on the stratigraphy of the Mis- written communication, 1983). west of Deming, at the northwestem end of sissippian rocks that form the northwestern the Cedar Mountain Range(Fig. 1). They are end of the Klondike Hills. Attracted by the Bliss Sandstone characterized by low relief and complexly structural complexity of the area, Corbitt et An incomplete section of Bliss Sandstone faulted Paleozoiccarbonate rocks, although al. (1978)mapped (scale1.:50,000) the south- crops out south of the granite in the west- brecciation, dolomitization, and silicification ern two-thirds of the Klondike Hills. Thor- central part of sec.22,T265, R13W(Fig. 2). locally obscure primary lithologies. The man and Drewes (1981)mapped the Klondike The base is not exposedand the uppermost stratigraphic section includes Precambrian Hills as part of the Gage SW quadrangle at beds are faulted against the overlying El Paso granite, Upper Cambrian to Pennsylvanian a scaleof l:24,00f. The objectiveof this re- Formation. The Bliss includes about 10 m of carbonate and subordinate clastic rocks, lo- port, based on the work of Rupert (1985)is dark reddish-brown, fine- to medium-grained, cally derived Upper Cretaceous/lowerTer- to illustrate the complex structural relations crossbedded quartz arenite in this outcrop. tiary conglomerate, Oligocene ash-flow tuff exposed in the Klondike Hills at an even more Many of the grains are frosted and the sand and rhyolite, and Quaternary colluvial and detailed scale (1:8,000).With this, elucida- is cementedby silica, calcite,and minorhem- alluvial deposits. Laramide-style structural tion of Laramide structural history is some- atite. r? features include a high-angle fault with dip- what better. slip and probable strike-slip offset, low-angle faults with both elimination and repetition Shatigraphy of stratigraphic units, small-scalefolds, and Alsoin thisissue localized extensive brecciation. Precambrian Darton's (1916) geologic map of Luna Medium-crystallinegranite occurs in the PajaritoY-Zr deposit,Otero County was one of the first to show Paleozoic west-centralp art of sec.22, T265, R13W(Fig. County p.21 rocks in the Klondike Hills. Bromfield and 2). The rock is intensely shattered, deeply Background perspectives Wrucke (1961)further defined the agesof the weathered, mostly coveredby alluvium, and and Paleozoicrocks in their reconnaissancemap forms topographically low poor exposures. on the PajaritoY-Zl deposit p.22 Stratigraphyand structureof the KlondikeHills p.23 TenthNew Mexico Mineral SymposiumAbstracts p. 30 NMBMMRMineral Museum Lord.burg notes p.33 Legendand correlationlor stategeologic map p. 34 Thompsonand Callaghan memorials p.37 SugariteCanyon State Park p. 38 1990NMGS fall field conference p. 43 Galleryof Geology-Toothof Time p. 43 Columbus Secondtransfer of cephalopods p.44 Upcomingmeetings p.45 NMMNHmineralexhibits p. 45 zo ml ServiceiNews p. 46 Staffnotes p. o 1o 2okm 48 Gomingsoon Commercialtravertine in NewMexico CimarronCanyon State Park Mineralsol NewMexico FIGURE l-Location map of southwest New Mexico showing location of Klondike Hills area of Fig. 2 Nan Mexico Geology May 1990 D El Paso Formation cludes all four membersas defined by Hayes interbedded wackestone, packstone, and (1975)and Clemons (1988b,in press a, b). grainstone. Allochems present in approxi- The El Paso Formation crops out exten- The basal Hitt Canvon Member is thin- to mate order of decreasingabundance are in- sively in the southern part of the Klondike medium-bedded, hifhly bioturbated, silty, traclasts, peloids, echinoderms, hilobites, Hills. As a result of intense faulting, a com- light- to medium-grey limestone or dolo- Naia, spicules, gastropods,and brachio- plete El Paso section is not preserved but stone. The silt and fine sand content de- pods. Massive stromatolite mounds are com- partial sections were measured by Rupert creasesupward. The dolostone is believed to mon in the upper part of the Hitt Canyon. (1986).His sections indicate that the unit is be mostly if not completely of hydrothermal These mounds are complexesof narrow, col- a minimum of 300 m thick (Fig. 3) and in- origin (Clemons, 1988a).The limestonesare umnar, stacked hemispheroidal heads (Fig. @o Q: alluvlum,colluvlum Ta: ash-flow tuff \zt Kr: Ringbone Fm \Mk Mh Ph: Horqullla Ls -n -.a Mp: Paradlse Fm \'t Mh: Hachlta Fm \MK N Mk: Keatlng Fm I.. Dp: Percha Sh I 28\ I Sf: FusselmanDol Oem rl Om: Montoya Fm Op: Padre Mbr Oem: McKelllgonMbr Oh: Hltt Cenyon Mbr €b: Bllss Ss pg: granlte It l6 uu r-/ lt / 'l t'z 1+tl lts ,t l< , lzr tlzt ilto l2s 1 20 23 trult oh T26S R13W, ts I cage SW Qradrangle .-,-)lon >t oh IP ''.7 26 A FIGURE 2-Geologic map of Klondike Hills generalizedfrom Rupert (1985). May 1990 Nar Metico Geology 4) separatedby distinctive channels. Oncol- frosted, monocrystalline quartz grains, with SYSTEM STRATIGRAPHIC UNIT TH ICKNESS ites (0.5 to 1..5cm diameter) are locally abun- (n) (ft) undulose extinction and thin hematite rims, dant in the Hitt Canyon. TERTIARY Ash-f]ow luff 30 98 in variable amounts of silicaand/or carbonate The overlyinglose Member is mostly thin- CRET.? Rlngbone Fn 50 cement. Member is a very dark gray, bedded, dark-gray to black, silty to sandy, PENN. Horouilla Ls 20 67 The Upham massive dolostone, black oolitic limestone with a few interbeds of me- Paladise Fn 220 coarsely crystalline, dium-gray limestone and orangish-gray do- MISS Escabrosa Gp to dark reddish-brown on fresh surface. It dacnata !m 90 295 lostone. Most of the limestone is lithoclastic KeatiDo Fn 700 has much quartz sand at the base, but the and bioclastic grainstones. Dedolomit2ed DEV Percha Sh 30 98 sand fraction rapidly decreasesupsection as ooids with baroque and saddle-shapedcal- SIL. FuEselman Dol t52 500 the unit grades to a featurelessand rather cite are quite common and locally concentric Montoya Fm homogeneousdark-gray, coarselycrystalline Cutter Mbr 66 grains in the ooids are present. Bioclasts are mostly tri- Afeman Mbr 18 59 dolostone. A few of the quartz lobites and echinoderms with minor gastro- I 26 Cable Canyon Member and lower Upham cable canyon Mbr 3-6 t4 pods and Nuia. Allare rounded and typically ORD. bl Paso !m exhibit a characteristic blue tint when ex- Padre Mbr a2 267 lens. No fossils were have thick micritized rims. V^r6lli-^n Mhr t0'7 350 amined with a hand The Member is overlain conformably Jose Mbr 9 30 found in the Upham Member in the Klondike Jose Hitt Canyon Mbr 100 328 by the McKelligon Member which is me- Hills. CAMB. ? BtlSS 5 30 98 dium- to thick-bedded, light- to medium-gray The Aleman Member consists of light- PRECA.I"IB. qtanlce limestone or dolostone. The dolostone is brown to medium-gray, finely crystalline do- probably a product of hydrothermal altera- FIGURE3-Rock units exposedin the Klondike lostone with abundant medium-gray chert as tion common in the Klondike Hills. The lime- Hills. elongate nodules and lenticular beds. The stones are interbedded wackestone, chert constitutes 30 to 40Voof the rock and packstone,and grainstone.Allochems in the weathers in a very characteristiccontrasting McKelligon beds include all those found in Otherwise the Padrewackestones, pack- relief. No fossils were observed in the Ale- stones, and grainstonescontain the sameal- the Hitt Canyon and |ose Members except man Member exposedin the Klondike Hills. for the ooids, and siliciclasticdetritus is no- lochems as the lower strata. The contact with the overlying Cutter Mem- tably absent even at the base of the Mc- ber is gradational over approximately 1 m Kelligon. Silicified cephalopod siphuncles Montoya Formation and is characterized by a decreasein chert appear to be more abundant in the Mc- The best exposures of the Montoya For- and a change to the massivelight-brown do- Kelligon beds. A few, small (1 m high, 1-2 mation are in the west-central part of sec. lomite of the Cutter Member. m long) sponge-Calathium mounds are inter- L6, T255, R13W (Fig. 2). The Montoya also The lower three-fourths of the Cutter bedded in the lower McKelligon strata. The crops out on SheepMountain and along the Member is chert-poor, medium-bedded, light- mound rock is predominantly spicular crest of the long ridge south of SheepMoun- brown, tinely crystalline dolostone with a few wackestone whereas the enclosing beds in- tain but is extremely faulted and fractured in small, broken brachiopod fragments. The clude packstone and grainstone. the latter fwo areas. upper part of the Cutter Member is a slightly The Padre Member conformably overlies The basal Cable Canyon Member is a light darker light-brown, finely crystalline dolo- the McKelligon Member in the Klondike Hills. reddish-brown, crossbedded, fine- to me- stone with increasing amounts of nodular Padre beds contain traces of siliciclastic silt dium-grained, moderately sorted quartz ar- chert up-section, although the chert rarely and very fine sand, but the sandstone and enite, which typically forms prominent ledges. exceeds2\Voby volume. The uppermostbeds sandy dolostone beds characteristicof lower The contactwith the underlying PadreMem- are essentially chert-free, finely crystalline, Padre strata at Bishop Cap and in the Frank- ber of the El PasoFormation is very sharp. light-brown dolostone. The contact with the lin Mountains (LeMone, 1969;Clemons, in The contactwith the overlying Upham Mem- overlying Fusselman Dolomite is an ero- press b) are absent.