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Home , Florida Mountains, Little Hatchet Mountains, Pyramid Mountains, Rubio Peak Formation, Victorio

KlondikeBasin-late Laramide depocenter insouthern New by TimothyF. Lawton and Busse// E. Clemons, Departmentof Earth Sciences, State University, Las Cruces, NM 88003

Abstract It was deposited in alluvial-fan, fluvial, Basinis thusa memberof a groupof late and plava environments adiacent to the Laramidebasins developed in and ad- The Klondike Basindefined in this pa- Lund uftift. Conglomerates'inthe lower iacentto theforeland in Paleogenetime. per occurs mostly in the subsurfaceof part of the section were derived from southwestem New Mexico, north of the nearby sedimentary shata of the uplift; Introduction Cedar Mountain Range and southwest volcanic arenites in the middle and up- Mexico and of Deming. The basin is asymmetric, per part of the section were derived from In southwestern New thickening from a northern zero edge in older volcanic rocks, including the Hi- southeastern , the Laramide the vicinity of Interstate 10 to a maxi- dalgo Formation, lying to the west and orogeny created a broad belt of north- mum preservedthickness of2,750 ft (840 northwest, and possibly to the north as west-trending faults and folds during the m) of sedimentary strata about 3 mi (5 well. approximate time span of 75-55 Ma (Da- km) north of the sbuthembasin margin. The age of the Lobo Formation and vis, 1979;Drewes, 1988).In contrast with The southem basin margin is a reverse development of the Klondike Basin are Laramide deformation of the Rocky fault or fault complex that bounds the bracketedas early to middle .The Mountain region, extensivevolcanism ac- Laramide Luna uplift, alsodefined here. asdasts Hidalgo Formation, which occurs companied shortening in Arizona and New The uplift consists of Paleozoic strata in the Lobo, has an upper fission-track has been inter- overlain unconformably by mid- ageof 54.9+2.7Ma (Marvinetal.,1978\. Mexico. This volcanism ash-flow tuffs and andesitic volcanics. The overlying Rubio Peak Formation in preted as subduction related (Coney and The principal sedimentary unit of the the Victorio Mountains is 41.7Ma (Thor- Reynolds, 1977;Keith, 1979).The defor- Klondike Basin is the Lobo Formation. man and Drewes, 1980).The Klondike mation itself has been attributed to un- derthrusting of the Farallon plate beneath North America (Seagerand Mack, 1985). Sedimentary basins formed in associa- tion with Laramide deformation. Laram-

Alsoin thisissue Upcomingmeetings p.7 NMGSspring meeting p. 7 Albuquerque'swater tabl* Winter1988-89 p.8 Eocenemammal from the BobcalHill Conglomerate, PeloncilloMountains, VV Rhyolite southwestemNew Mexico p. I ., Tuff v Galleryof Geology p. 13 Geothermalresources in Cabullona Group NewMexico p. 14 Summaryof chargesfor naturalresources other than oil and gas on New Mexico state lands p. 16 NMGS1992 abstracts p.17 Service/News p.22 Topographicmaps p.23 Staffnotes p.24 ide sedimentary units include an and Love RanchBasins (Seager and Mack, FIGURE 3-Conelation of stratigraphy of the assemblageof strata that range in age from 1985).The late Laramide basins of the Pa- Victorio Mountains and subsurfaceunits en- Late Cretaceousto middle(?) Eocene(Fig. leogene developed on the North Ameri- countered in the Saltys, Cockrell, and Bisbee 1), although agesof the Paleogeneunits can craton, whereas the early Laramide Hills wells, shown as projected onto a section are as yet poorly constrained. Improved basins of the Cretaceousdeveloped within trending N20"8 through the Victorio Moun- Fig. 2 interpretation of the timing and style of the tains. See for well locations. Explanation: region of the older BisbeeBasin and Bliss Formation; Oe, El Paso Formation; Laramide deformation hinges Ob, on our un- trough, which formed by Om, Montoya Group; Sf, Fusselman Forma- derstandingof the agesand dishibution crustal extensionin Early Cretaceoustime tion; Dp, Percha Shale; Mk, Keating Forma- of these syntectonic units. The obiective (Dickinson, 1981;Bilodeaq 1982;Mack et tion; Mh, Hachita Formation; Mp, Paradise of this report is to describe the evidence al., 1986;Dckinson et al., 1989). Formation; Ph, Horquilla Formation; Pe, Earp for a newly discovered Laramide basin, Formation; Kl, undifferentiated Lower Creta- here named the Klondike Basin, in south- Methods ceous; Kh, Hell-to-Finish Formation; Ku, U- westem New Mexico and to discuss its Bar Formation; Kn, Mojado Formation; Tl, Lobo significance.The Klondike Basin takes its The Klondike Basin was defined largely Formation; Tr, Rubio PeakFormation; Tv, mid- name from a small range known as the through subsurfaceanalysis (Clemons and Tertiary tuffs. Klondike Hills immediately north of the Lawton, 1991).Cuttings from three wells (Fig. Cedar Mountain Range(Pearce, 1955). 2) wereprepared as thin sectionsand examined pehographically. Stratigraphic correlations of sedimen- Gamma-ray are overlain by conglomeratewith clasts and logs tary formations deposited as a result of sonic of the wells were corre- derived dominantly from Lower Creta- lated, l^aramidedeformation suggestthat at least and formation tops picked from ceous strata. The conglomerate and Pa- two generations of Laramide basins exist cuttings were depth adjusted to match leozoic strata are overlain by mid-Tertiary (Fig. 1). The older generation,ranging in lithologic changes indicated by the well ash-flow tuffs (Bromfield and Wrucke, logs. age from Campanian through late Maas- Surface sections of Paleozoic,Mes- 1961);no Lower Cretaceousrocks are ex- hichtian, encompassesthe Fort Critten- ozoic, and Tertiary strata were examined posed in the range. Southeastward,along in den Formation in Arizona, the Cabullona the Victorio Mountains, Cedar Moun- the general trend of the northem flank of tain Range, Group in , and the Ringbone and Klondike Hills, and West Lime the Cedar Mountain Range, the West Lime McRae Formations in New Mexico (Dick- Hills in order to compare lithologies seen Hills contain a seriesof northeast-vergent in inson et a1.,7989;Basabilvazo, l99l; G1l- cuttings with the variability of in- reverse faults, the southwesternmost of terbedded lette et al., 1986).Ages of the formations lithic types observed in out- which emplaces carbonates are understood largely from interpreta- crops. The thicknessesof units depicted (Thompson, 1982) above conglomerate tions of the biostratigraphic significance in Fig. 3 were reconstructed using dips composed of Paleozoiccarbonate clasts. indicated of dinosaur fossils (Miller, 1964;Lucas et by dipmeter logs for the Saltys and Bisbee al., 19%);Lucas and Gonzalez-Leon, in Hills wells. Fig. 3 was con- press).The younger generationof basins structed by projecting the sections on to is probably late Paleoceneto Eoceneand a line of azimuth 20olocated midway be- is represented by the Love Ranch, Lobo, tween the Saltys and BisbeeHills wells. New AAexfic@ and Skunk RanchFormations (Seagerand Mack, 1986;Seager et al., L986;Wilson et Geologic setting GEOLOGV al., 7989; Wilson, 1991). Representative In the Cedar Mountain Range south of late-Laramide basins include the Potrillo the BisbeeHills well, lower Paleozoicstrata . Scienceand Serrice ISSiN 0196-944X Volume 14, No. 1, February 1992

Erlitor: Carol A. Hjellming Publishedquarterly by New Mexico Bureau of Mine and Mineral Resourcs a division of New Mexico lnstitute of Mining & Tehnology

BOARD OF REGENTS Ex-Officio Bruce King, Gwor ol Nm Mulm Alan Morgan, Supeilfltendentol Public Instrution Appointed Lt. Cen. L@ Marquez, Prq., 1 9-7995,Albu4wque Charfes Zimmerly, Se.lTrus., 7997-19E7,S@to Diane D. Denish, 7992-19E7,Albuquaqw z J. Michaet Kelly, 7992-1997, Rogwll Steve Tores, 1967-1997,Albu4uerqw New Mexico Institute of Mining & Tehnology Columbus Pr6iddl. .... lnurenceH.tattman N New Mexico Bureau of Mines & Minenl Resoures Directu Md State Gnwist . . . Chades E. Chapin o ? Sub*riptirc: lssued qwterly, Februry, (E May, August, 0 20mi November; subffi iption prie 96.0(Velendar year. q\ Editorial rcttq: Articles submitted for oublication should be in the editor's hands a minimm of five 0 30 km (5) months before date of publication (Februry, Mat Augut, or November) and should be no longer than 20 typewritten, double-spacedpages. All scientific papers will be rwiewed by at least two peopl€ in the apprcpriate field of study. Address inquiriG to Carcl A. Hielmh& Editor of Nru Manlco Crolqy, New Mexi@ Bureau of Mines & Mineral Rercurces, Sqono. NM 87U74796. Published.as publicdoruin, thq4ore rcpldrcible without _t pmision. Sowe crcdit rcquested. Circul^tion:\,ffi FIGURE 2-Selected physiographic features of southwestem New Mexico and locations of wells P/ifltfl: University of New Mexico Printing Servies studied for this report.

February 7992 New Metico Geology Northeast Sonthwest

4. SALTYS UNIT #1 (33-25s-15w)

SURFACE

3. COCKRELL STATE #1 (14-2sS-16W)

Fault zone in llmestone

2. BISBEEHILLS UNIT #1 (11-26S-11W)

SUFFACE 1. VICTORIOMTNS. 'r"ll (FROMKOTTLOWSKI, La'l 1960) 't'4

SILICICASH-FLOW TUFFS OUATERNARY DEPOSITS Palgoiolc rock6 laull6d ov€r Lobo lormation

Plnchout ol Lobo in RUBIOPEAK FORMATION viclnitY ol l-10 onto Laramido gurro uPlilt / of Seeger and Meck , (1986)

1

LOBO FORMATION

Nar Meria Gmlogy February The conglomerate may be Hell-to-Finish Formation (Lower )or Lobo. The conglomerateis faulted againstmet- amorphosed and overtumed through Mississippian strata, which are in turn thrust over the Hell-to-Finish For- mation. This system of faults trends northwestward toward the Cedar Moun- tain Range and illustrates the structural complexity created by Laramide defor- mation in the area. In the Victorio Mountains, a thin (790 ff;240 m) Lower Cretaceoussection (Kot- tlowski, L950)overlies Ordovician and Si- lurian strata.The Lower Cretaceoussection is overlain unconformably by 690 ft (210 m) of reddish-brown conglomerate,sand- stone, and siltstone(Kottlowski, 1950)that we consider to be Lobo Formation. The Lobo in the Victorio Mountains is overlain concordantlvby homblende-andesiteflows and brecciai of the Rubio PeakFormation.

breccia in the Victorio Mountains (Thor- man and Drewes, 1980).

Subsurface relations Three wells southwest of Deming pen- etrated thick sections of Lobo. The thick- ness of the unit is 2,750 ft (840m) in the BisbeeHills Unit #1, 7,800ft (550m) in the CockrellState #1, and 1,050ft (320m) in the Saltys Unit #1 (thicknessesof in- trusive rocks have been removed from the sections). In the Saltvs well, the Lobo is truncatedbeneath a re.rersefault with Or- dovician through Permian strata in the hanging wall (Fig. 3). In the Saltys and Cockrell wells the Lobo rests on a sequenceof glauconitic marine sandstones and shales that we interpret as the upper part of the Mojado Forma- tion (Albian-Cenomanian?). These ma- rine bedsat the top of the Mojado overlie a thick inverval of nonmarine strata con- sisting of fine-grained sandstone, sili- ceous siltstone, and silty mudstone. Palynomorphs from this nonmarine in- terval in the Cockrell well include Cica- tricosisporites spp. and Quadripollis krempii, which are both long-ranging Cretaceousforms (S. N. Nelson, written communication |une L4, 1990). The basal contact of the Lobo is some- what anomalous in the BisbeeHills well. Although the unit appearsto contain a basal conglomeraticinterval, the Lower Cretaceoussection is absentand the Lobo directly overlies FusselmanDol- omite (Clemonsand Lawton, 1991).In the other two wells, Lower Cretaceousstrata overlie the Fusselman. Two possible in- terpretations are: 1.)the Lower Cretaceous section was eroded prior to Lobo depo- sition in the BisbeeHills well; 2) the Lower Cretaceoussection is absentin the Bisbee Hills well as a result of faulting. Presently

February 7992 New Mexico Geology FIGURE 4-Silty mudstone, muddy siltstone, and calcareousfine-grained sandstone with very rich in volcanic lithic grains. A lower Lobo angular to subangular quartz and plagioclase.Lobo Formation, Saltys well, 5,500ft. Plane-polar- lacking in volcanic grains is absent in the : ized light; bar 0.5 mm. Victorio Mountains. These observations indicate that the volcanic influence was FIGURE S-Poorly sorted, fine-grained, calcareousvolcanic arenite with angular to subangular quartz, plagioclase,biotite, magnetite, and andesitefragments. Lobo Formation, BisbeeHiIIs well, greater to the north than to the south dur- 3,7il ft. Crossed nicols; bar = 0.5 mm. ing Lobo deposition or that Lobo deposits did not onlap the area of the Victorio FIGURE 6-Silty calcareousmudstone with spar-filled globigerinids. Conglomeratein lower part Mountains until late in the historv of the of Lobo Formation, Saltys well, 5,830ft. Plane polarized light; bar = 0.1 mm. basin. Volcanicarenites occur in th-eupper part of the Lobo north of the Laramide Burro uplift (FiS. 4 and likewise indicate available data do not permit us to reject probably represent Mojado lithologies. the importance of a volcanic provenance either of these possibilities; however, the Lower Paleozoicdasts are alsopresent and to the north of the study area (Mack and Lobo sectionis thickest in the BisbeeHills, may have been derived from both lower Clemons, 1988). indicating that subsidence was greater Paleozoic strata and the Hell-to-Finish In the Victorio Mountains, the Rubio there than at the other studied localities. Formation, which contains abundant lower Peak Formation is 1,4fi) ft (430m) thick. This observation favors omission by fault- Paleozoic clasts elsewhere in the region In the BisbeeHills well, Rubio Peakflows, ing becauseit obviates the need for major (Macket al., 1986).Sandstones of all three breccias, and volcaniclasticsare 1,800 ft post-Early Cretaceousuplift and erosion wells likewise indicate a sedimentary (5a9 m) thick. In the Cockrell well, 1,9(X) followed by major Paleogenesubsidence. source terrane, although the volcanic ar- ft (549 m) of Rubio Peak are truncated The Lobo Formation in the BisbeeHills enites of the BisbeeHills well suggestan beneath basin-fill gravel (Clemons and well consistsof interbedded reddish-brown increasingly important volcanic prove- Lawton, 1991).Thus, the Rubio PeakFor- silty mudstone, siltstone, and verv fine to nancewith time. Mack and Clemons(1988) mation, like the Lobo, thickens somewhat medium-grained calcareous sandsto.te noted a similar upsection increasein vol- from north to south in the areasstudied. (Fig. 4; Clemons and Lawton, 1991).The canic arenites in the Lobo Formation at basal 140 ft (43 m) is conglomerate con- fwo localities in the . Klondike Basin-a late taining clastsof silty shaleand mudstone, The northward-fining trends demon- Laramide depocenter calcareous fine-grained sandstone, silty strated between the Saltys and Cockrell The Lobo Formation between the Vic- limestone, dolostone, chert, and lower wells suggestthat the sedimentary source torio Mountains and the Cedar Mountain Paleozoic limestone. Angular to suban- terranelay to the south. Rangeforms a southwestward-thickening gular quartz grains, carbonate and vol- wedge of nonmarine clastic strata. The canic rock fragments, chert, plagioclase, Victorio Mountains wedge is bounded to the southwest by a potassium feldspar, and traces of biotite The Lobo Formation of the Victorio dominantly reverse fault that emplaced are present in the sandstonebeds. Sand- Mountains consists of conglomerate, Paleozoicunits above the Lobo. The Lobo stones of the middle and upper parts of sandstone, and reddish-brown siltstone. overlies Lower Cretaceousstrata with only the Lobo section are dominant$ volcanic It rests upon a sequenceof siltstone and slight discordance. In the BisbeeHills well, arenites(Fig. 5). subordinate fine-grained sandstone sim- Lower Cretaceousstrata are missing be- In the Cockrell well, the lower 40 ft (12 ilar to the nonmarine strata of the Moiado neath the Lobo becauseof either faulting m) of the Lobo Formation is conglomerate encountered in the subsurface.The basal or erosion. Conglomerates with Lower with clasts that contain globigerinid{ike conglomerate is poorly sorted boulder and Cretaceous clasts that overlie Paleozoic forams (Fig. 6). Other lithologies present cobble conglomerate with clasts of sand- strata and underlie mid-Tertiary volcanic as clasts are shale, mudstone, and sili- stone, limestone attributable to the Lower units in the Cedar Mountain Range may ceous medium-grained sandstone with Cretaceous U-Bar Formation, and silt- indicate that Lobo strata lapped onto the quartz overgrowths. Above the conglom- stone. In addition to these sedimentary southem uplifted block; however, the cor- erate are 740 ft (226 m) of interbedded clast types, the basal conglomerate con- relation of the conglomerateof the Cedar reddish-brown mudstone, shale, calcar- tains clasts that resemble ande- Mountain Rangeremains uncertain. North eous fine- to medium-grained sandstone, site of the Hidalgo Formation of the Little of the Victorio Mountains, the Lobo thins and siliceousmedium-grained sandstone. Hatchet and . These and pinches out onto Precambrian rocks Like the sandstone of the lower part of volcanic clastsbecome increasingly abun- of the Laramide Burro uplift (Seagerand the Lobo in the Bisbee Hills well, sand- dant upsection in the Lobo. Mack, 1986).To the southeast, we spec- stone in the Cockrell well contains an- The conglomerates and sandstones of ulate that the Lobo continues south of the gular to subrounded grains of quaft4 the Lobo are arranged in severalupward- Florida Mountains, as depicted by Seager chert, plagioclase,minor potassium feld- fining sequences several hundred feet and Mack (1986). spar, biotite, and carbonate rock frag- thick. Conglomeratesare crudely bedded The uplifted region that lies south of ments. The upper 1,110ft (339m) of the to flat bedded, with angular, poorly sorted the Lobo depocenter consists of com- formation in the Cockrell well is fine clasts.They grade to flat-bedded reddish- plexly faulted and elevated Paleozoicand grained and consists of interbedded red- brown sandstonesoverlain in tum by in- subordinate Mesozoic strata. The uplift is dish-brown mudstone, shale, calcareous terbedded red-brown siltstone and sand- partly exposedin the West Lime Hills, the siltstone, and claystone. The Lobo in the stone that form intervals several tens of Cedar Mountain Range,and the Klondike SalWs well is very similar to that in the feet thick. We interpret these associated Hills immediately northeast of the Cedar Cockrell well, buf it contains more sand- facies as alluvial fan-braided fluvial-playa Mountain Range. A northwestward ex- stone. The lower 180 ft (55m) of Lobo in depositional environments arranged in tension of the uplifted terrane was pen- the Saltys well is probably conglomerate retrogradational sequences. The upper- etrated in the Saltys well. This uplift is with mixed lithologies that include glo- most siltstone and sandstone interval of termed the Luna uplift (Fig. 7) becauseof bigerinid{ike forams and mollusc frag- the Lobo is overlain by flow breccia of its extensive presencein Luna County. ments. altered hornblende andesite. We regard The Klondike Basin (Fig. 7), defined by Interpretation of cuttings indicates that this breccia as the base of the Rubio Peak the thick wedge of Lobo, was initiated by the basal conglomerate of the Lobo con- Formation. deposition of conglomerates dominated tains abundant clastsof Lower Cretaceous Like the upper sandstone in the Lobo by Lower Cretaceousand Paleozoicclasts. strata. The siliceous sandstones, globi- of the BisbeeHills well, the sandstonesof Volcanic clasts were present at northern gerinid-bearing clasts, and silty shales the Lobo in the Victorio Mountains are 13

New Metico Gmlogy February 1992 5 the has recently yielded an age of 72.14+0.1,8Ma by the {ArfeAr method (W. C. Mclntosh, writ- ten communication, November 25, L99L); in the Pyramid Mountains, the Hidalgo has a minimum fission-track age of 9.9-+2.7 Ma (Marvin et al., 1978).There- fore, basin development might have be- gun at any time during that interval, although the volcaniccomponent of basin fill would probably have been much greater than observed if Hidalgo volcanism had been synchronous with formation of the Klondike Basin. Basin developmentwas largely complete before emplacement of the volcanic pile of the Rubio Peak For- MEXICO mation in middle to late Eocenetime. Ac

LaramideBasin Kluth, S. N. Nelson, and Chevron Over- I seas Production, Incorporated, for paly- Uplift composed mainly nomorph analyses of samples from of Pal€ozoic and Mesozoic Cockrell State #1 and Tom Bruce of Mar- sedlm€ntaryrocks shall Young Oil Company for supplying Uplllt composed mainly us with dipmeter logs of the BisbeeHills of besementrocks Unit #1 and SaltysUnit #1 wells. We also are grateful to Frank Kottlowski and the MEXTCO N.M. Bureau of Mines and Mineral Re- : sources for financial support to do the 0 30 km petrographicanalyses. Reviews by S. M. FIGURE7-Paleogeographic reconstruction of KlondikeBasin and other Laramidebasins and Cather, G. H. Mack, and W. R. Seager upliftsof southryellem Nglv Mexico.Margins of the Hidalgoand LaramideBuno upliftsmodified substantially improved the manuscript. from Seagerand Mack (1986).The HidalgoBasin depictedhere was termedRing-bone Basin by TheresaCall assistedwith drafting of the Seagerand Mack (1986)but containsLaramide deposits, including the SkunkRaich Formation, figures. in addition to the RingboneFormation (Wilson, 191). The namechange is suggestedto avoid conJusionregarding distribution of Laramideunits. IUB is inha-upliftbas-in of Miik and Clemons (1988),which contains a thin Lobosection of lessthan 600 ft (200m) restingdirectly on Precambrian References to Ordovicianrocks. Adjacent south Florida Mountains fault (SFMF)hai both riverseand right- Eambilvazo, C. T., 79D1,Stratigraphy, depositional lateralcomponents of offset(Brown and Clemons,1983). Left-lateral offset inferred on north"ern environments, and sedimentdispersal pathways of structuralb-o11dary of Luna uplift is basedon leftlateral strike-slipfaulting in KlondikeHills the Upper CretaceousRingbone Formation in the (Rupertand Clemons,-190). Left Little Hatchet Mountains of southwestern New stepsinferred on structuraltrendi reflectc6mplex structure in Mexico: MS thesis, I-as Cruces, New Mexico State southem_Partof FloridaMountains (Mack and Clemons,1988) and WestLime Hills (discussedin University, 158pp. text).RiSht{ateral offset hgs been interpreted on the north flank of the Hidalgouplift at Hatchet Berggren, W. A., Kent, D. V., Flynn, J. J., and Van Gap(HG; Seager and Mack. 1986). The seemingly conflicting displacements arE didicult to explain Couvering, J. A., 1985, Cenozoic geochronology: with simplekinernatic models and requirefuriher study. Geological Society of America, Bulletin, v.%, pp. 7N7-7478. Bilodeau, W. L.,1982, Tectonicmodels {or Early Cre- localities.The sedimentaryrock types volcanic grains are taceous rifting in southeastem Arizona: Geology, that the CretaceouFPale- v. 10, pp. ffi-470. contributed to the conglomerateare pres- ocenevolcanics of the Hidalgo Formation Bromfield, C. S., and Wrucke, C. T., 1951, Recon- ent in modem ranges along the Luna up- and its correlatives. naissancegeologic map of the Cedar Mountains, lifb known sources for volcanic clasts lie The Klondike Basin probably formed in Grant and Luna Counties, New Mexico: U.S. Ge- to the southwest in the Little Hatchet early to middle ological Suruey, MiscellaneousField Studies Map Eocene time and thus is MF-159. scale1 :52.500. Mountains (Zeller, 1970)and to the west an example of a Iate Laramide basin. It Brown, G. A., and Clemons, R. E., 1983, Florida and northwest in the Coyote Hills (Thor- formed at the edge of the former Bisbee Mountains section of southwest New Mexico ov- man, 1977) and Pyramid Mountains Basin,where thick sectionsof Lower Cre- erthrust{ reevaluation: New Mexico Gmlogy, v. (Thormanand Drewes, 1978).Dominance taceous strata 5, pp.26-29. thin northward in a short Clemons, R. E., 1982, Geology of of sedimentary Srain types in sandstones distance and pinch out above older strata quadrangle, Luna County, New Mexico:New Mex- of the wells and volcanic grain types in of the craton (Mack et al., 1985).The Klon- ico Bureau of Mines and Mineral Resources,Geo- the Lobo of the Victorio Mountains indi- dike Basin lacks the phase of Late Cre- logic Map 51, scale7:24,400. cate that the sedimentary source re- taceous deposition, Clemons, R. E., and Lawton, T. F, 1D1, Pehographic recorded by the and well log analysis of four exploration wells in mained important throughout deposition Ringbone Formation, that occurred in the southwesternNew Mexico: New Mexico Bureauof of the Lobo, but that volcanic detrifus next depocenter to the southwest (Seager Mines and Mineral Resources,Open-file Report 381, probably did not come from the south. and Mack, 1986;Basabilvazo, 199L). Fur- 97 PP. The Luna uplift was probably the domi- ther evidence Coney, P. J., and Reynolds, S. J., Dn, Cordilleran of the youth of the Klondike Benioff zones: Nature, v. 270, pp. 403-405. nant source for clastic detritus in the Basin is the presenceof Hidalgo clasts in Davis,G. H.,7979, Laramidefolding and faultingin southwest-ernpart of the basin. The asym- the Lobo Formation. The Hidalgo For- southeastemArizona: American foumal of Science, metry and southwest thickening of the mation overlies the Ringbone in the Little v. 279, pp.513-569. basin may be due to loading by the uplift. Hatchet Mountains Dckinson, W. R., 1981,Plate tectonic evolution of the ana may be in part southem Cordilloa; in Dickinson, W. R., md Payne, Analogous load asymmehy is present in equivalent with the Paleocene-Eocene W. D. (eds.), ReLationsof tectonicsto ore deposits Laramide basins of the Rocky Mountain Skunk Ranch Formation there (Wilson, in the southem Cordillera: Arizona Geological So- province (Hagen et al., 1985). We infer 1991).Reported ages on the Hidalgo For- ciety, Digest, v. 14, pp. 113-f36. that dispersalsystems parallel to the basin mation and its possible equivalentarange Dckinson, W R., Fiorillo, A. R., Hall, D. L., Monreal, axis carried volcanic R., Potochnik, A. R., and Swift, P N., 1989,Cre- detritus from the widely: a hornblende and-esiteflow at the taceousstrata of southem Arizona; in fenney, J. P northwest. The most likely sourcesof the base of the unit in the northem part of and Reynolds, S. J. (eds.), Geologic evolution of

February 1992 New Metico Geology Arizona: Arizona GeologicalSociety, Dgest, v. 17, Cretaceous Research, v. 11, pp 343--&9 Ryan, R. G ,79136,Laramide basement-coreduPlift pp 447-461.. Lucas, S. G, and GonzAlez-Le6n,C., in press, Re- and basinsin south-centralNew Mexico:New Mex- Drewes, H., 1971,Geologic map of the Mount Wright- porte preliminar sobre dinosarios del CretacioTar- ico Geological Society, Guidebook to the 37th Field son quadrangle. southeast of Tucson, Santa Cruz dio de la cuencade Cabullona,Sonora: Universidad Conference,pp. 123-130. and Pima Counties, Arizona: U S. GeologicalSur- de Sonora, Depto. Geologia Boletin, v 7 Thompson, S , il, 1982,Oil and gasexploration wells vey, MiscellaneousGeologic Investigations Map I- Mack, G H., and Clemons, R. E., 1988, Structural in southwestem New Mexicn; m Powers, R. B (ed.), 514. scale1:48.000. and shatigraphic evidence for the Laramide (early Geologic studie of the Cordillenn thrust belt Roclcy Drewes, H., 1988,Development of the foreland zone Tertiary) Buno uplift in southwestem New Mexico: Mountain Associationof Geologists, pp. 521-53,6. and adiacent tenanes of the Cordilleran orogenic New Mexjco Geological Society, Guidebook to the Thorman, C- H., lEn, Geologic map of the Coyote belt near the U.S -Mexican border; in Schmidt. C 39th Field Conference,pp 59-65 Peak and Brcckman quadmgles, Hidalgo and Gmnt J. and Perry, W. J., fr (eds ), Interaction of the Rocky Mack,G. H., Kolins,W 8., and Galemore,| 4., 19fX, Counties, New Mexico: U.S. Geological Survey, Mountain foreland and the Cordilleran thrust belt: Inwer Cretaceousstratigraphy, depositional envi- Miscellaneous Field Studies Map MF-924, scale C,eologicalSociety of America, Memoir 171, pp 447- ronments. and sediment dispersalin southwestem t24,Offi. 463 New Mexico: American fouhal of Science,v. 286, Thoman, C. H., and Drewes,H 7978,Geologic map Gillette,D. D, Wolberg,D L., andHunt, A.P.,798f, pp. 309J31 of the Gary and Lordsburg quadrangles, Hidalgo Tyrannosaurus rex from the McRae Formation Marvin, R G., Naeser, C. W., and Mehnert, H. H., County, New Mexico: U.S. GeologicalSuruey, Mis- (Lancian, Upper Cretaceous),Elephant Bufte Res- 1978, Tabulation and radiometric ages-including cell,aneousC,eologic Investigations Map I-1151, scale eruoir, Siena County, New Mexico: New Mexico unpublished K-Ar and fission-trackages-for rocks L24,0AO Geological Society, Guidebook to the 37th Field in southeastem Arizona and southwestern New Thorman, C H., and Drewes, H., 1980,Geologic map Conference, pp. 235-238 Mexico: New Mexico Geological Society, Guide- of the Victorio Mountains, Luna County, south- Hagen, E S, Shuster,M W, and Furlong, K. P, book to 2fth Field Conference,pp 243-252. westem New Mexico: U S. GeologicalSuwey, Mis- 1985,Tectonic loading and subsidenceof intermon- Miller, H W , 79f.4,Cretaceous dinosaurian remains cellaneousField Studies Map MF-l175, scale tane basins: Wyoming foreland province: Geology, from southem Arizona: Joumal of Paleontology,v. L24,AOO. v 13, pp 585-588 38, pp. 378-384 Wilson, D A,1991, Depositionalenvironments, Keith, S. B, 7979, Paleosubductiongeometries in- Pearce,T M.,1965, New Meico place names-a ge- provenance, and age of the Skunk Ranch Foma- fened from Cretaceousand Tertiary magmatic pat- ographical dictionary: Albuquerque, University of tion, Little Hatchet Mountains, southwestem New terns in southwestem North America: Geology, v New Mexico Press, 187pp. Mexico: MS thesis, [as Cruces, New Mexico State 6, pp 516-527. Rupert, M. G , and Clemons,R. 8., 1990,StratigraPhy University, 87 pp. Kottlowski, F E, 1960, Surnmary of Pennsylvanian and structure of the Klondike Hills, southwestem Wilson, D. A., Lawton, T. F., and Basabilvazo,G T., sections in southwestem New Mexico and south- New Mexico: New Mexico Geology, v. 12, pp 23- 1989,Stratigraphy and depositional environments eastem Arizona: New Mexico Bureauof Mines and 30 of the Skunk Ranch Formation, Little Hatchet Mineral Resources,Bulletin 66,187 pp Seager,W. R., and Mack, G H., 1986,Laramide pa- Mountains, southwestem New Mexico (abs ): New Loring, A K, and Loring, R B , 1980,lJAr agesof leotectonicsof southem New Mexico; in Peterson, Mexico Gmlogy, v. 11, p. 63. middle Tertiary igneous rocks from southem New J. A (ed ), Paleotectonicsand sedimentationin the Zeller, R. A., Jt , 1970,Geology of the Little Hatchet Mexico: lsochron/West,no 28, pp 77-79. Rocky Mountain region, :American Mountains, Hidalgo and Grant Counties, New Lucas, S G , Basabilvazo,G T, and Lawton, T. F, Association of Petroleum Geologists, Memoir 41, Mexico: New Mexico Bureau of Mines and Mineral 1990,Late Cretacmus dinosaursfrom the Ringbone pp 669-685. Resources,Bulletin 96, 22 pp. ! Formation, southwestern New Mexico, U S A : Seager,W. R, Mack, G H, Raimonde,M S, and

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Nm Mexico Gmlogy February 1992