Uplift, Erosion, and Burial of Laramide Fault Blocks, Salado Mountains

Home , Love Ranch Formation, Rubio Peak Formation

Uplift,erosion, and burial ol Laramidefault blocks, Salado Mountains, SierraCounty, New Mexico byWiltiam R. Seager,New Mexico State University, Las Cruces, NM 88003, and Anton B. Mayer,Leggette, Brashears, and Graham, Inc , 423Sixth St., NW, Albuquerque,NM87102

Introduction In south-centralNew Mexico, uplifts and mentary basins,the Love Ranchand Potrillo In recent years Laramide deformation in basins trend north-no south-central New Mexico has been com- west, highly oblique pared to that of the central Rockies of Wy- of late Tertiary fault bl oming (Seagerand Mack, 1986;Seager and rift. Thus, the Larami< others, 1986).The structuralstyle in both areas and segmentedby the is distinguished by basement-cored block fragmentsof the Laran uplifts separatedby broad basins filled with revealedin crosssectio synorogenic to post-orogenic sedimentary Such fragments,expos rocks. Thrust or ieverse fiults border uplift- from the CaballoMbuntains south to the East probably indicate an extension of the uplift basin margins, at leaston one side, and these, Potrillo Mountains, constrain the location, appear at various places in the Black lange as well as associatedtight, overturnedfolds, trend, and geometry of the Laramide Rio area. For example,near Lake Valley (Fig. 1) indicatesubstantial crustal shortening. Grandeuplift (Fig.1) and its two comple- nTTff,:*:T il"il.t:t:.[:ij:#?",3; headwater region of North Percha Creek 107' Laramide erosion exposed Precambrian I granite.The most instructiveoutcrops, how- Cristobal Mts. ever, are in the SaladoMountains, located l j Alsoin thisissue

Oil and gas discoverywells drilledin New Mexicoin 1987 p.54 Chargesfor naturalresources on StateLands as of 1988 p. 60 Ore-testingcapabilities at the NewMexico Bureau of Minesand Mineral Resources p. 61 ChicosaLake State Park p.62 Abstractsfrom NMGS 1988 springmeeting p. 64 Upcomingmeetings and fieldtrios p. 69 Service/News p.70 Statfnotes p.72 NEW MEXICO Gomingsoon Typeand referencesections of Lower Cretaceousstrata Kit CarsonState Park Geomorphicdevelopment of Cityof rocks,Grant County FIGURE l-Location map. Shaded area shows extent of Laramide Rio Grande uplift as interpreted by Seager et al. (1986). 15 km nearly due west of Truth or Conse- thrown to the west, the whole fault block is group. Because of erosion during or follow- quences (Fig. 1; Lamarre, 1974;Mayer, L987\. tilted eastward (Fig. 2). In the Salado Moun- ing the Laramide or faulting during the late In this area not only is the Laramide fault- tains the easterly dip ranges from approxi- Tertiary, parts of the El Paso, Montoya, and block structure revealed, but also the manner mately 15 to 25 degrees, and strata dip Abo sections either are not exposed or are in which the fault blocks were eroded and eastward beneath gravels of the Palomas missing altogether. In spite of this, a thick- eventually buried by younger volcanic rocks. Basin. ness of approximately 500 m of Paleozoic rock Rocks ranging in age from Precambrian to crops out (Mayer, 7987). General feafures and stratigraphy of the Quaternary crop out in the Salado Moun- Middle Tertiary volcanic and clastic rocks Salado Mountains tains (Fig. 3). Precambrian rocks include overlie Paleozoic strata, the contact being an The Salado Mountains are a relatively small granite, muscovite phyllite and schist, and angular unconformity of modest (10 to 15 (approximately 20 km'?) group of hills and metadiorite, all exposed in the core of a Lar- degrees) discordance. Middle Tertiary strata peaks located near the center of the eastern- amide fault-blocli uplift. Paleozoic strata have an uneven thickness because lower parts most, outlying fault block of the Black Range. nonconformably overlie the Precambrian and of the section are inset against or onlap Lar- To the north, the fault block is known as range in age from Cambrian-Ordovician to amide topography whereas somewhat Sierra Cuchillo, to the south it goes by the Permian. Largely marine limestone, dolo- younger rocks overlap completely and bury name Animas Mountains. Bordered on the mite, shale, and sandstone, these rocks form the older terrane. Among the oldest of the west by a late Tertiary normal fault, down- the highest hills and peaks in the mountain Tertiary rocks are post-orogenic boulder con- glomerate and breccia beds, only a few me-

-n ters thick, derived from an adjacent Laramide 1 L1< Tb' uplift. Clasts are as much as several meters I ^( IT in diameter and include Paleozoic strata as l old as the Bliss Formation. Conglomerates probablv are correlative with the Love Ranch Formati,on of the CaballeSan Andres Moun- \'8 tains area (Kottlowski et al., 1956).The Love tP/ Ranch strata grade upward into or are inter- bedded with intermediate-composition flows and volcaniclastic strata of the Rubio Peak Formation (Palm Park, Spears, or Datil Group equivalent; Elston 1957; Kelley and Silver, 1952; Seager and Hawley, 1973; Cather et al., 1987). Much of the formation is laharic in orp, origin. As much as 1,075 m thick, the formation thins dramatically both because its lower beds pinch out by onlap onto Lar- New AAexnc@

Tba GEOLOGV -t o o Scienceand Seryice g) c\ /Ts Volume 1O, No. 3, August 1988 \-nl4 Editor:Carol A \ L'\ Hjellming \J/ Drafting assistaflce:Rebecca Titus Published quarterly by q) QTp New Mexico Bureau of Mines and Mineral Resources to"R a diviskrn of Nry Mqi(! Ir6titute of Mining & firhdotJt BOARD OF REGENTS Ex Officio Gany Camthes, Gmmor of Nru Mexico Alan Morgan, Surytintend.entof Publiclnstruction x Appointed (t Irnton Malry, Pra ,1985-1991,Ahuqurque Robert O Anderuon, Se llrus , 1987-1993, RruII Gilbert L Cano, 19&5-1%9,Afuunque Donald W Monis, 1983-19'119,Ins Alamq Steve Tores, 1967-1991, S6oto M-'€F New Mexico lnstitute of Mining & Tahnology Tba't5 F. Pr$iddl laurene H littman New Mexico Bureau of Mines & Mineral Resurces T3 I Dietor Frank E Kottlowski F' i\ Deputy Director fames M Robertsn 4*a Subrriptions: Issued quarterly, February, o Mat Autust, November; subsiption price $6 00/calendaryear o Editqial mttq: Articles submitted for publication should 9) be in the editor's hands a minimum of five (5) months (D 'o before date of publietion (February,May, August, or f"o. November) and should be no longer than 20 typewriF ten, double-spacedpages A-Urientific papere will be reviewed by at leasttwo people in the appropriate field km of study Addressinquiries to CarolA Hiellming, Editor ol Nru Metiu Geology,New Mexico Bwau of Mines & 2-Generalized geologic IfCURf map of the SaladoMountains, modified after Mayer (lggn. pe, Mineral Rercuces, Saorc, NM 87801 l'recambrianrocks; Pl, lower Paleozoicrocks; DM, Devonianand Mississippianrocks; P, pennsylvanian Publishedre public domin, thoefore reprdrcible uithout Wr- rocks; Pa, PermianAbo Formation;Tlr, Love Ranch Formation;Trp,'ft.ubio peai Formatidn; Ttur, mission, Sourceqedit rcqrcted unnamed lithic ash-flow tuff; Ttu, unnamed crystal ash-flow tuff; iba, basalticandesite flows; Ts, Cirillation:1,ffi Fe Group;,Tb, basalt.flows; palomas P/iflra: University of New Mexico Printint Plant l:1"^' ?ylt erp, Formation;Tai, biotite andesitedike; Tiu, lgneouslntruslons/ undifferentiated.

August 1988 New MexicoCeology amide topography and becauseits upper beds tains and buried on the east by post-Lar- thrown on the south side. Precambrianand are truncated by an unconformity. Radio- amide volcanic and sedimentary rocks. In lowest Paleozoicrocks in the uplifted block metric dates from elsewhere in the Black between, the Laramide geology is well ex- are juxtaposed against Ordovician to Penn- Rangeand south-centralNew Mexico region posed, particularly in the Chavez Canyon sylvanian strata in the down-faulted block to indicate the Rubio Peak Formation is late area (Fig. 2). the north. Stratigraphicseparation is as much Eoceneto earliestOligocene in age(e.g. Kott- The central Laramide structure is the as 400 m. Unfortunately, the dip of the fault lowski et al., 1969;Marvin and Cole, 1978; Chavez Canyon fault (Fig. 2), movement on is not known precisely because the fault is Clemons, 1"982;Loring and Loring, 1980). which raised a Laramide fault block of mod- intruded throughout its length by a 50-m- Unconformably above the Rubio Peak For- est relief. The fault trends N85'W and is up- thick biotite andesite dike. The trace of the mation, two ash-flow tuffs of probable mid- Thickness dle Oligocene age crop out along the eastern tIo riloGene \ o ! o v c -v fl and southern flanks mountains. The t c 0 -10m of the Helstocene Palomas Fm. 0-, ,_r Oco r tl. lower tuff, lithic rich and 100 to 200m thick, Pliocene bagalt ,.{' 35i-7Om has not been correlated with other tuffs of the region. The upper tuff, 30 to 60 m thick, !ower Santa is crystal rich and also has not been corre- Mlocene Fe GP. 150+m lated with other tuffs. Scatteredremnants of basaltic andesite flows, inferred to be correlative with BearSprings basalt (Elston, 1957) basaltlc endeslte 15i0+m or basalticandesite of PovertyCreek (Elston unnamed et al., 1973),unconformably overlie the tuffs crystal tulf m or Rubio Peak Formation. RecentK-Ar dat- Oligocen e 0-200 ing indicates these units are approximately unnamed 11; 28 Ma old (Seageret al., 1984). tlthlc tulf i,\?".'ii' Unconformably overlying various parts of o l,:, tr ^ Ara the middle Tertiary volcanicsection is a se- o : _!l..-_i' -- I quence of "earIy rift" fanglomerate, sand- o o :>' stone, and siltstone assignedto the lower ot 3ao-..fva l, Santa Fe Group. A thousand meters or more >. o >/ ' tu >^'1 thick in along Salado the _.'- rjv \ outcrops Creek, \._/ \ .\.l formation was derived primarily from mid- .E --: _ ,),o Lo' dle Tertiary volcanic rocks. It may be correl- b --- Q' Rubio Peak Fm. \.ct L g 0- 1075m ative with all or part of the Miocene Hayner I , -\.-- Ranch and Rincon Valley Formations of the o '-:-./ '\t ' ,.',.n' E o /' CaballoMountains-Hatch Valley area(Seager --l ^t I v-qY- I o ^o rt and Hawley, 1973) and with the Popotosa o \.--: 'r 6! e ut Formation of the Socorroarea (Denny, 1940; ^ :^ 9A-':.^Y/<1 Bruning, 1973;Chapin and Seager,1975). The o v -L/ unit 15 25 degrees was o dips eastward to and r>^a 4o, \oa clearly rotated along with older strata as the -\<_ 1 Salado Mountains block was uplifted and Love Ranch Fm. r:-qce-e--r:L \* ".i tilted eastwardin late Tertiary time. sflfprypa{inq]q dFm o-10m Essentiallyundeformed basalt flows and piedmont-slopegravels unconformably overlie older rock units. The basalt issued from vents to the west of the SaladoMoun- Bar B Fm. 165m tains, then flowed eastward down ancestral drainageways suchas Salado Creek. Locally, d Itl 6 (, the flows may be offset a few meters by tr movement on range-boundaryfaults. The 6 6 c Fm. I illl flows now cap geomorphically high-level o Nakaye 123m mesasor ridge tops. judging from dated flows o 6 tr It in similar geomorphic positions near Hills- tr ol o o I _r_r r _l boro, the flows may be approximately 4 to o- = --f-l 4.5 Ma (Seageret al., 1984).Piedmont-slope t _l 91m gravels assigned to the Palomas Formation House Fm. Red ' -1 | f t I (Lozinski and Hawlev 1986)of latest Pli- I L I ]_--t ocene and Pleistoceneage bury the basalt Mlssle sipplan 47m flows and overlapolder rock units. LateQua- Lake Valley Fm. /rir'l\ ternary and Holocene alluvium in arroyos or Devonlan Percha Fm. 45m shallow drainageways are the youngest de- 8m(?) Fusselman Dol.; ./ _Z-__,' ' posits in the area. . (?) Montova Fm. 1100m Laramide structure Ordovlcian El Paso Fm. 'r 1-,-i tr 100m -Cambrlan- Erosion of the late Tertiary Salado Moun- Bllss Fm, 47m tains fault block has revealed a fragment of an older fault-block uplift of probable Lar- ,'):,',)\r\\,i),\\\ amide age. Becausethe Laramide uplift and Precambrlan ,';- i-'i\..]1.)i.rr its boundary fault trend nearly east-west, they are truncated on the west by the north- trending boundary fault of the SaladoMoun- FIGURE 3-Columnar section of sedimentary and volcanic rocks exposed in Salado Mountains.

Nap Mexko Geology August 1988 dike across topography suggests a steep parts of the PalomasBasin. Perhapsthe Lar- lowest parts of the paleopiedmont slope. southerly dip for both dike and fault. If so, amide Love Ranch Basin, well exposed in Younger Rubio Peak laharic strata progres- the fault is reverse.Bedding attitudes in beds western parts of the Jornadadel Muerto, ex- sively onlap the piedmont slope, eventually of the downthrown block adiacentto the dike tends northwestward beneath the Palomas burying the dike in the ChavezCanyon fault. are steep but not overturned, suggesting Basin and contains erosional debris from the Perhaps the Rubio Peak Formation also bur- predominantly vertical movementrather than Chavez Canyon fault blocks (Fig. 4). Pres- ied the hanging-wall block of the Chavez low- or even moderate-anglethrusting. ervation of Cretaceousrocks in the Palomas Canyon fault; this is not entirely clear be- If 15 to 25 degreesof late Tertiary tilting Basinin the Summmit L Mims and Gartland causeerosion locally removed part of the up- are removed, Paleozoicrocks are restored to 1 Brister wells supports this (Foster,1978). per beds of the Rubio PeakFormation before their Laramide attitude. The operation shows Bv middle Tertiarv time Laramide fault emplacement of the overlying tuffs. At any that, exceptfor the steepdrag nearthe Chavez bloiks in the Saladolv{ountains were buried rate, the Rubio PeakFormation thins by dep- Canyon fault, footwall rocks generally had a by volcanic rocks. If one views the geologic osition as it onlaps the Laramide fault blocks northeast shike and l0-degree-northwestdip map (Fig. 2) from the west looking eastward and thickens to the north. Clearly, the Rubio prior to emplacementof the Tertiary volcanic down dip, the map takes on the aspectsof Peak strata leveled the former topography. section. Uplifted hanging-wall rocks appear a cross section, and the manner in which the Succeedingsheets of ash-flow tuff over- to be broadly domed along an east-west axis, uplift was buried becomesclear. lapped the eroded Rubio Peak strata as well although so few Paleozoicstrata remain that Figure 5, a diagrammatic cross section de- as the structurally highest parts of the Lar- this is not entirely clear.The Chavez Canyon rived from the "down plunge" view of the amide uplift south of Chavez Canyon fault; fault remains a steep, probably south-dip- geologicmap, showsthe important relation- finally the ash-flow tuffs buried the uplift ping fault after late Tertiary tilting is re- ships. A pediment cut on the downthrown completely. Emplacement of basaltic andes- moved. block of the Chavez Canyon fault is covered ite flows and deposition of Santa Fe fan- discontinuously by bouldery debris of the glomerate further concealed the Laramide Age of Laramide deformation Love Ranch Formation derived from the up- fault block. The age of Laramide deformation in the thrown block. Thesebeds also interfinger with Regional relationships SaladoMountains is poorly constrained.The basal beds of the Rubio Peak Formation. An- only direct evidence we have for the age of desite lava flows of the Rubio Peak fill some Figure 4 illustrates that the Laramide fault the Chavez Canyon fault is a K-Ar date from of the deepest drainageways incised into blocks in the Salado Mountains may be in- the andesite dike that intrudes the fault. La- marre (1974)dated biotite from this dike at 'i'" 43.7+L.7 Ma. The fault is thereforeolder. Regional relationships suggest Laramide T deformation in the Truth or Consequences Kor Pso region may have occurred in two pulses (Chapin and Cather, 1981):an earlierone in latest Cretaceous to Paleocenetime related to deposition of the McRae Formation (Hunter, 1985),and a later one in early to middle Eocenetime relatedto emplacement of the Love Ranch Formation (Seagea1983; Seagerand Mack, 1985).Little is known about the earlier phase. The SaladoMountains deformation may be a product of the younger event becauseLove Ranch-typeclastic strata Truthor Concequences derived from the hanging wall of the Chavez Canyon fault are present in the basalparts of the Rubio Peak Formation. 4

Erosion and burial of the Laramide uplifts Before Laramide deformation began, Pa- leozoic and Mesozoic strata approximately 2,000m thick covered the SaladoMountains area (Kottlowski, 1963).This approximation includes estimates of the thickness of Per- mian and Upper Cretaceousrocks that are missing in the SaladoMountains but are preserved in the Sierra Cuchillo (Jahns, 1955) and Truth or Consequencesarea. Almost the entire Phanerozoicsection was eroded from the hanging wall of the Chavez Canyon fault during or following Laramide deformation, and all but 700 m were removed from the footwall. Both blocks were structurally high relative to some unknown adjacent basin, and presumablythat basin containsthe de- tritus derived from the uplifts. No thick ac- cumulations of l,aramide synorogenic or post- FIGURE4-Interpreted extensionof Laramide Rio Grande uplift and Love Ranch Basininto BlackRange orogenic deposits are known in the Black area. Dotted areas are parts of Black Range where pre-Laramide rocks are exposed. Symbols T/?e,Tl Range or Sierra Cuchillo so it seems likely Pl,TllP, T/Pa, T/Psa, T/K refer to areas where Tertiary volcanic or clastic rocks overlie Precambrian, that the Laramide Basin is hidden beneath lower Paleozoic,Pennsylvanian, Abo, San Andres Limestone, or Cretaceousrocks respectively.

August 1988 New Mexico Geology terpreted as a westward extension of north- much broader uplift of early Tertiary age- sertation, New Mexico Institute of Mining and Tech- ern parts of the Rio Grande uplift of the the Rio Grande uplift-that encompassed nology, Socorro, New Mexico 732 pp.; New Mexico Bureau of Mines and Mineral Resources,Open-file Re- Caballo Mountains area. The easterly trend much of the central and southem Black Range port 38, 142 pp. of the ChavezCanyon fault blocksis nearly as well as broad areasto the eastand south. Cather,S. M., Mclntosh,W. C., andChapin,C.E.,1987, parallel to westernmost exposuresof the Rio The Salado Mountains structure trends Stratigraphy, age, and rates of deposition of the Datil Grande uplift-margin structures in the cen- N85'W in approximate conformity with Lar- Group (Upper Eocene-LowerOligocene), west-central New Mexico: New Mexico Geology, v. 9, pp. 50-54. tral Caballo Mountains. Also, the northward amide trends in other parts of the Rio Grande Chapin, C. E., and Cather, S. M., 1981,Eocene tectonics downstepping of faults is consistentin both uplift but at high angles to younger Rio and sedimentation in the Colorado Plateau-Rocky areas. Grande rift faults. Erosion of 1500to nearlv Mountain area, in Dickinson, W. R., and Payne,W. B. The Rio Grande uplift of the Caballo 2,0fi) m of Paleozoicand Mesozoicstrata frorir (eds.), Relations of tectonics to ore deposits in the southem Cordillera: Arizona Geologicai Society, D- Mountainrsouthern Rio Grande area is a the SaladoMountains area is an index of the gest, v. 74, pp. 173-198. huge structure,consisting of at leasttwo ma- magnitude of Laramide uplift in the region. Chapin, C. E., and Seager,W. R.,7975,Evolution of the jor blocks and several smaller ones (Seager Except for very thin post-orogenicpediment Rio Grande rift in the Socorro and Las Cruces areas: et al., 1986).Consequently, it is unlikely that veneers,sedimentary deposits resulting from New Mexico C,eologicalSociety, Guidebook to 26th Field Conference, pp. 297-321. the relativ€ly small fault blocks of the Salado this erosion are missing, even on the struc- Clemons, R. E., 1982, Geology of MassacrePeak quad- Mountains represent the full extent of the turally lowest blocks.They must have been rangle, Luna County, New Mexico:New Mexico Bureau Rio Grande uplift in the Black Rangearea. transported across the uplift into adjacent of Mines md Mineral Resources,Geologic Map 51, scale They probably are intra-uplift blocks or ele- basins that now lie 7:24,ffiO. hidden beneath the late Denny, Tertiary ments of a much broader uplift that probably C. 5., 1940, Seology of the San Acacia Tertiary PalomasBasin. By late Eocenetime area, New Mexico: Journal of Geology, v.48, pp.73- extends southward to Lake Valley or bevond considerable topographic relief still existed 106. as well as westwardand northwird. Paitsof across Laramide fault blocks. Subsequent Elston,W. 8.,1957,C*ology and mineraldeposits of Dwyer this inferred broad uplift were raised suffi- deposition of upper Eoceneto lower Oligo- quadrangle, Grant, Luna and Siena Counties, New Mexico: New Mexico Bureauof Mines and Mineral Re- ciently high so that erosion cut into broad cene lavas and volcaniclastic rocks leveled sources,Bulletin 38, 86 pp. areasof Precambrianor lower Paleozoicrocks the landscape,and lower Oligoceneash-flow Elston,W. E., Damon,P. E., Coney,P J., Rhodes,R. C., prior to late Eocene time (Fig. 4). For ex- tuffs finally buried the highest, most deeply Smith, E. I., and Bikerman,M.,1973, Tertiary volcanic ample, in and adjacentto North PerchaCreek eroded fault blocks. Such onlap and overlap rocks, Mogollon-Datil province, New Mexico, and sur- rounding regiort-K-Ar dates, pattems of eruption, md in the east-central Black Range, the Rubio relationshipsof middle Tertiary volcanicsonto periods of mineralization: GeologicalSociety of Amer- PeakFormation thins onto Larlmide uplifts, eroded Laramide uplifts can be seenin many ica, Bulletin, v.U, pp.2259-2274. and Precambrian granite is overlapped by parts of southem New Mexico, but are per- Ericksen,G. E., Wedow, H., Jr., Eaton,G. P, and Leland, sheets of younger ash-flow tuff (Ericksen et haps nowhere more clearly revealed than in G. R., 1970,Mineral resourcesof the BlackRange Prin- al., 1970; itive Area, Grant, Siena, and Catron Counties, New Seageret aL, L982).These are the the Salado Mountains. Mexico: U.S. Geological Suruey, Bulletin 1379-8, 762 same onlap and overlap relationships dis- AcxNowupcurrurs-Mapping in the Sa- PP. played so strikingly in the Salado Moun- lado Mountains was done by Seagerin the Foster, R. W., 7978, Selected data for deep drill holes tains. Only locally are rocks as young as early 1970sand in 1987.Mayer mapped the along Rio Grande rift in New Mexico: New Mexico Bu- reau of Mines and Mineral Resources,Circular 153,pp. Permian preserved beneath Tertiary volcan- area as part of his M.S. geology degree in 236-237. ics in the central and southern Black Range 1985and 1987. We appreciatethe helpful re- Huntet J. C., 1986,Laramide synorogenicsedimentation area; these must represent local intra-uplift views of SteveCather, RichardHarrison, Tim in south-central New Mexicepetrostratigraphic evo- sags or synclines in the broader uplift. Lawton, and Greg Mack. lution of the McRae Basin: Unpublished M.S. thesis, Colorado School of Mines, Golden, Colorado. Jahns, R. H., 7955,Geology of the Siena Cuchillo, New Conclusions References Mexico: New Mexico Geological Society, Guidebook to 5th Field Conference, pp. 1,58-774. The Laramide uplift in the Salado Moun- Bruning, I. W., 1973,Origin of the PopotosaFormation, tains is probably only a small element of a north-central Socono Countv, New Mexico: Ph.D. dis- (continuedon page60) North South Santa Fe GP. unnemed crystaf tutf basalticandesite

Y:?-4:2 qrt unnamed fithic .A/ l-\ tuff v, rr\/ I - t-\ Rubio Peak Fm. ) r'-r, Love Ranch Fm. -4--+ lower Paleozoicrocks Permianrocks Precambrianrock s \.

FIGURE S-Diagrammatic section showing onlap and overlap relationship of Tertiary volcanic rocks to Laramide fault blocks

Nao MexicoGeology August 1988 (continuedfrom page53) United States:Unoublished M S thesis. UniversiW of R E., 1982, Geology of northwest part of Las Cruces Kelley, V C , and Silver, C , 1952, Geology of the Caballo WesternOntario, London, 134pp 1" x 2' sheet: New Mexico Bureau of Mines and Mineral Mountains with special reference to regional stratig- Loring, A K., and Loring, R 8., 1980,I(Ar agesof mid- Resources,Geologic Map 53, 3 sheets,scale 1:125,000 raphy and structure and to mineral resources, including dle Tertiary igneous rocks from southem New Mexico: Seager,W. R. and Hawley, J. W ., 1.973, Gmlogy of Rincon oil and gas: University of New Mexico Publications in Isochron/West,no 28, pp 77-19 quadrangle, New Mexico: New Mexico Bureau Mines ,12 Geology, no 4,286 pp Lozinski, R. P , and Hawley, J W., 7986,Upper Cenozoic and Mineral Resources,Bulletin 101, pp. Kottlowski, F E.,1963, Paleozoic and Mesozoic strata of PalomasFomation of south-centralNew Mexico: New Seager,W. R., and Mack, G H., 1986,Laramide paleo- southwestern and south-central New Mexico: New Mexico Geological Society, Guidebook to 37th Field tectonics of southern New Mexico; in Peterson, I A. Mexico Bureau of Mines and Mineral Resources, Bul- Conference, pp.239)47 (ed ), Paleotmtonicsand sedimentation in the Rocky letin 79, 100 pp. Maruin, R F., and Cole, I C ,7978, Radiometric ages- Mountain region: American Association of Petroleum Kottlowski, F E., Flower, R. H, Thompson, M. L., and compilation A, U.S GeologicalSuruey: IsochrorVWest, Geologists, Memoir 41, pp. 659-685 Foster R W, 1956, Shatigraphic studies of the San no 22, pp 3-14 Seager,W. R , Mack, G H., Raimonde,M. S., and Ryan, Andres Mountains, New Mexico: New Mexico Bureau Mayer, A. B ,1987, Structural and volcanicgeology of the R G , 1985,Laramide basement-cored uplift and basins Mines and Mineral Resources, Memoir 7, 732 pp Salado Mountains-Cucia Peak area, Siena County, New in south-central New Mexico: New Mexico Geological Kottlowski,F E, Weber, R H, andWillard,M E,1969, Mexico: Unpublished M S thesis, New Mexico State Society,Guidebook to 37th Field Conference,pp.123- Tertiary intrusive-volcanic mineralization episodes .in University, Las Cruces, 61 p 130 the New Mexico region (abs ;: Geological Society of Seager,W R, 1983,Laramide wrench faults, basement- Seager,W R., Shafiqullah, M., Hawley, J W, and Mar- America, Abstracts with Programs, pt,7, p 278 cored uplifts, and complementary basins in southern vin, R, 1984, New K-Ar dates from basalts and the Lamane, A L , 1974, Fluorite in iasperoid of the Salado New Mexico: New Mexico Geology, v. 5, pp 69J5 evolution of the southern Rio Grande rift: Geological Mountains-significance to metallogeny of the western Seager,W R., Clemons, R E , Hawley, J W, and Kelley, Society of America, Bulletin, v 95, pp. 87-99. n

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