Oil and Gas Exploration Wells in Southwestern New Mexico

.. ” *. ‘L

New Mexico Bureauof Mines and Mineral Resources Open File Report No. OF 181

OIL AND GAS EXPLORATIONWELLS IN SOUTHWESTERN NEW MEXICO

by Sam Thompson I11 New Mexico Bureau of Mines and Mineral Resources

Socorro, NM 87801

October, 1982

Reprinted from - Drewes, Harald, ed., Cordilleran overthrust belt, Texas to Arizona: Rocky Mountain Association of Geologists 1982 guidebook, p.’ 137-153. OIL AND GAS EXPLORATION WELLS * 137

OIL AND GAS EXPLORATION WELLS IN SOUTHWESTERN NEW MEXICO

Sam Thompson 111 New Mexico Bureau of Mines and Mineral Resources - Socorro,New Mexico 87801 -

ABSTRACT In Hidalgo. Grant, Luna, and Doaa Ana Counties01 Southwestern New Mexico, 64 oil and gas exploration wells have been drilled through 1980. In the 22 key wells drilled to Mesozoic, Paleozoic, or Precambrian rocks, shows of oil or gas have been reported in 11, but no commercial produclion has been established as yet. Several favorable source and reservoir units are indicated in the Paleozoic section, whichis analogous to that ol the productive Permian basin. and in the Mesozoic section. which is analogousto that of Ihe western Gulf basin. ' Lithoslraligraphicand biostraligraphic studies 01 thesubsorlace sections in fhe key wells provide significant dala lorbothlocalandregionaiinterpretations. in the Humble No.1 Slate BA. Ordovician conodonts were identilied in the bottom of the well, negating a previous Ihrust interpretation. In the Grimm No. 1 Mobil 32, lower Tertiary palynomorphs were idenlilied below the Lobo[?], providing a critical maximum age for that formation; Lower Cretaceous and Jurassic index lossiis document a norlhward exlensicn of the Chihuahua trough. A regional isopach map of the Paleozoic shows thickening up to 15,000 It in the Pedregosa basin area, thinning to less than 4,000 it in theBurro.Moyo1e.s uplift area, and thickening to over 8,000 11 in the Orogrande basin area. A map of the Mesozoic shows soulhward thickening ol the Bisbee Group (Lower Cretaceous) IO over 15,000 It. northward onlap, and possible continuity of the upper part with the Sarten. Upper Cretaceous Sfrata are less than2,000 It lhick and exhibit soulhwestward onlap. Laramide uplilt and erosion stripped Mesozoic and older rocks from muchol the Burro and olher posilive areas. Upon the Laramide unconformity, conglomerates and redbeds were deposited, followed by andesitic volcanic rocks; their decreasing eges to the northeast reflect Ihe migration 01 the Cordilleran magmatic arc. Some Laramide thrusls may have formed by upward and outward movement lrom wrench zones. In the lower piate of a major lhrusl, fhermal alteration of kerogens has exceeded the iimilof oil preservation, and gas may not bepreserved in older units.

iNTRODUCTlON south, including ailof Hidalgo and Luna Counties and the Oil and gas exploration wells drilled to Paleozoic or southern parts of Grant, Sierra, and Dona Ana Counties in Precambrian'rocks in the Pedregosa basin area of south- New Mexico. The northern partof Chihuahua, Mexico and eastern Arizona, southwestern New Mexico, and northern the western part of El Paso County, Texas also are included Mexico were discussed by Thompson and others (1978). in the map rectangle. The present investigation focuses on the wells in south- Table 1 is a generalized correlation chart of stratigraphic western New Mexico and it: (1) includes those drilled to units in southwestern New Mexico. Separate columns of Mesozoic, Paleozoic, or Precambrian rocks: (2) provides an formation names are listed for the Pedregosa basin (after update of formationtops and other basicwell information: Zeller, 1965 and 1970), Burro uplift (after Jicha, 1954), and and (3) presents isopach maps of Paleozoic and Mesozoic the 0rogr.ande basin (after Kottlowski and others. 1956). strata. Those strata contain the significant petroleum These basins are areas of subsidence where Pennsylvanian source and reservoir rocksof the region. rocks are 2000 ft thick or more (Kottiowski, 1960a). Only Figure 1 shows the locations,names, total depths,and wells which reached units beneath the Laramide uncon- oldest formations penetratedby exploration wells drilled formity are discussed in this paper. Main rock types and to documented Mesozoic or older rocks in southwestern depositionalenvironments are grossly generalized. New Mexico prior to 1982. The map area covers about Petroleum source and reservoir evaluations are based 156 miles from west to east and about 100 miles north to 'on current work in the Hidalgo County area (Thompson, 138 SAM THOMPSON 111

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E2EN-rnE v~~~,~v"" "" """""""""1

140 SAM THOMPSON 111

1981) that is being extended to other parts of the region. in the following sections, wells in southwestern New Lying within the Basin and Range province, this area Mexico are discussed under the counties. Information on is one of the active frontiers of petroleum exploration. wells drilled in northern Chihuahua, Mexico was provided Because of the stratigraphic similarities of the Paleozoic by J.C. Tovar R. of Petroleos Mexicanos in Thompson and section with that of the Permian basin, and of the Lower others (1978); no wells have been drilled in thatarea since Cretaceous section with that of the western Gulf basin, that time(Just0 Mesa D., personal communications, 1982). this area has a high potential(Greenwood and others, 1977). In the part of El Paso County, Texas, shown on the map Projections of the Cordilleran fold and thrust belt have (Fig. l), none of the exploration wellshave reacheddefinite encouraged structural exploration(Corbitt and Woodward, Mesozoic or older rocks accordingto Cooky (1958) and 1973; Drewes, 1978); however, several contrasts are noted Harbour (1972, p. 78.80). For information on wells drilled in comparison with the productive overthrust belt of in adjacent parts of western Texas, see Pearson and Under- .Wyoming and Utah (Woodward, ,1980; Thompson, 1980; wood (1975), Uphoff (1978), and Pearson (1980). Information Woodward and DuChene, 1981). Tectonic and igneous on wells drilled in southeasternArizona was provided by complexities, including Tertiary volcanism, local meta- J.N. Conley in Thompson and others (1978); since that time, morphism, and extensive Basin and Range faulting, add two deep tests have been drilled by the Phillips Petroleum to the risks of frontier exploration(Thompson, 1976, 1980). co. EXPLORATION WELLS HIDALGO COUNTY Table 2 presents the basic data on the 22 wells drilled A total of 28 petroleum-exploration wells have been to pre-Laramide stratigraphic units in Hidalgo, Grant, drilled in Hidalgo County. Of these, 9 have been drilled to Luna, and Doria Ana Counties, New Mexico (Fig. 1). These prelaramide units. All 9 key wells are discussed in a recent data generally were taken or derived from scout tickets, report documenting petroleum-source units in the Hidalgo cuttings, logs, and other information available in the New County area (Thompson, 1981). Data for Table 2 were taken MexicoLibrary of SubsurfaceData, supervised by from thatreference. R.A. Bieberman at the New Mexico Bureau of Mines and The Cockreil No. 1 Pyramid Federal well was drilled in Mineral Resources. Locations, names, and completion the Animas Valley on the west side of the Pyramid Moun- dates were taken directly fromthe scout tickets or reports tains. Below the unconformity at the base of the Tertiary by ober.ators. Locations are given by township, range, volcanic rocks is a Paleozoic section from Escabrosa section, and footage from northlsouth and eastlwest lines (Mississippian) to Bliss (Cambrian-Ordovicien). Each of the section. Elevations ofthe kelly bushing (KB), derrick Paleozoic unit was intruded by Tertiary diorites. Elston floor (DF), surface-casing flange (SC), or ground level (GL) and others (1979) show this area as lying near one of theit are of the points from which depths were measured in volcanic cauldrons. the individual wells. In the northern part of the Playas Valley, the Powers Formation tops were derived from a synthesis of pre- well was drilled near the Coyote Hills. C.H. Thorman previous reports, spot checks of lithostratigraphicboundaries pared an unpublished sample description and determined using cuttings and logs, and available biostratigraphic that this well penetrated Mojado (Lower Cretaceous) in- control. Generally used publications included Kottiowski truded by Tertiary granodiorites (Thorman, 1977). R.F. Broad- and others (1956. 1969), Thompson and Bieberman (1973, head prepared an unpublished sample description on the Thompson and others (1978), and Thompson (1981); specific KCM No. 1 Cochise StateA which was drilled inthe Playas references will be discussed under the counties. Where Valley on the east side of the Animas Mountains. Kerogens available, descriptions and logs prepared by the Permian in the Mojado have been subjected to a high degree of Basin Sample Laboratory and reports by the Paleonto- thermal alteration, and the section in this well is believed logical Laboratory (both of Midland, Texas)were useful. to have beenburied beneath the major thrust whose present R.W. Foster (formerly with New Mexico Bureau of Mines erosional limit is exposed in the northern Animas Moun- and Mineral Resources) described cuttings and determined tains (Thompson, 1981, p. 41). formation tops on several wells in the region. Although In the Hachita Valley, the Hachita Dome Inc. No. 1 Tid- the tops reported onTable 2 are considered to be the best ball-Berry Federal well encountered shallow Precambrian that can be presented with current knowledge, they are on the upper plate of'themajor thrust mapped in the Sierra subject to revision as more detailed studies are made of Rica (Zeller, 1965, and 1975). The Graham well was drilled individual wells. recently only 1,500 ft northwest of the Hachita Dome well; Total depths generally are those measured by wire-line tops were determined by Fred Dumas (Permian Basin logs. The formation at totaldepth is indicated for each well; Sample Laboratory). Near this area, the Beal No. 1 Beal if a well bottomed in Tertiary intrusive rock, the host Federal well (29s-15W-28)reportedly drilled valley fill from formation is indicated in parentheses. Shows of oil and the surface to310 ft and Permianrocks from that depth to gas reported in wells drilled prior to 1958 may not be 414 ft; however, no cuttings or logs are available to verify reliable; those listed forwells drilled thatyear or later are the Permian designation. considered reliable, and many have been documented by In the southern part of the Playas Valley, the Cockrell hydrocarbon logs. Results from geochemical analyses are No. 1 Playas State drilled through2,480 ft of valley fill, en- not included. Although no commercial quantities of oil countered a Paleozoic section from Horquilla (Pennsyl- or gas have been found to date, the shows encourage vanian.Permian) to Bliss, and may have bottomed in Pre- further exploration. cambrian. The Cockrell No. 1 State-1, 225 drilled through yell Cmpletion Lacation -name date Elevation Formation tops (Ti - Bertiary intrusive rock) lbtal depth Oil, gas shows HIDALLO COUNTY: 24s-19W-31 Cockrell No. 1 9-30-69 4.244' KB Surface-Quaternary; 385'-Gila?;l,890'-Tertiary 7.404' mne 1,980'N: 660.E Pyramid Fed. volcanic rocks (Til; 5.795'-Escabrosa (Ti); Precambrian 6,68O'-Percha (Ti): 6,86O'-mntoya (Til; 6,980'- El Paso (Ti): 7.130"Bl:ss (Ti); 7,340"Precm- briar,

265-1711-4 powers No. 1 12-3-724,377' KB Surface-Quaternary, aMve 920"Tertiaey (or 4.007' mne 330'5: 1.980'E sea te Cretaceous).volcanic rocks; 1,19O'-mjado; Tert.intrur. 3,93O'-Tertiary intrusive rocks (mjadol

285-1711" KCM No. 1 3-22-754.416' KB Surface-Quaternary; above 70"Gila;2,370"5.916' Gas: 2.050'8 1,980'N:1,980'E Cochise St. A Ho jado m jado 2,220':2,650'

305-1511-12 Hachita Done No. 1 5-23-57 4.349' DF Surface-Quaternary; 224"EscabbTOSa; 800" 2,726' cas: 1,500'i 1.655'5; 2,012;W Tidball-Berry Fed. Percha1,395'"ontoya; Paso:(Ti); 1.653"El Precambrian 2,310':2.430*; 2,590a-81iss;oil: 2,723'-Precambrian 2.590' 0 r 30.5-15W-12 Graham No. 1 11-21-78 4.331' GL Surface-Quaternary2 540"E~cabrosa (Ti): 960" 2,455' None 1,980'S: 660'W 1,980'S: Hatchet Fed. Percha; 1,24O'-Hontoya; 1.710"El Paso El Pas0 a: 305-17W-14 Cockrell No. 1 6-11-70 4.455' KB surface-Quaternary; 100'-GIlai2.480'-Horquillar 7,086' Dead oil: G) 600.N; 1.980'E Playas state 5,192'-4,127'-Escabrosa;3,836'-Paradise; Prec:a*rian?5,780' Percha: 5,568'-Montoya: 5,89O'-El Paso; % 6.764'-81iss: 7,03O'-Precambrian? rn .. x 31s-17W-12 Cockrell11-24-70 No. 1 4.480' KB Surface-Quaternary:150'-Gila; 2.465'-Teertiary 4,005' None W 1,980'N: 660.E State-1,225 volcanic (and sedimentary?) rocks; 2,595'- Colina 5 Epitaph; 3,77O*-Colina a 315-18W-3 KCH No. 1 1-22-755,156' KB Surface-~arp255'-Horquilla (Ti); 2,225'-(Ti): 4,464' mne . 1,494'N: 1,753.E Forest Fed. mtanorphosed Horquilla and Tertiary intrusiveintrus. Tert. z0 rocks. (Horquillal Z 325-16W-25 Humble No. 1 12-24-58 4,587' KB Surface-Quaternary: 230"U-Bar; 648*-Hell-t0 14.585' Gas: 4,190.- 2rn 990'N; 1,980'E 990'N; state Ea Finish; 995"Concha;El 1.522"Scherrer:1,532.- Pas0 4,219' t- Epi;aph: 3.310'-reverse fault, Epitaph re- r Fated; 4,45O'-Colina; 5.258"Earp; 6,265'- 0) Horquilla; l0,995'-Paradise: 11r425'-Escabrosa: 12,50O'-Percha; 12,83O'-Hontoya: 13.214"El Pa90

GRANT CouNTi : 255-16W-14 Cockrell NO. 1 8-24-694.354' KB Surface-Quaternary; above 36O'-Tertiary (or 9,282' Oil: 4,140' 700'5; 700'W coyote state Cretaceous1 volcanic rocks: 1,790-Hojado (Til: Precambrian 'e 6,400'-U-Bar (Ti); 7.100'-Hell-to-Finish; 7,24O'-Montoya: 7.720'-El Paso: 8,360'-81iss: 8,58O'-Prec&rian

275-16W-16 Wininger and 9-13-43 4.675' GL Surface-Quaternary; 28*-Ringbone?; 580'-Hojado?1.500' Oil: 610'-620': 1,600'S: 850'E Berry No. 1 State ' Hojado? oil.gas:1.270'- 1,330': gas: 1,415'-1,430'

Table 2. Basic data on exploration wells drilled lo Mesozoic, Paleozoic. or Precambrian rocks in south, western New Mexico (see text for sourcesof information). 4 P N

~~ ~~~ well Completion Location Natm? dateElevation ForMtiop'tops (Ti = Tertiaryintrusive rock1 Total depth Oil, gas shows

LUllA COUNTY: 235-1OW-7 Cockrell No. 1 11-6-69 4.534' KB Surface-Quaternary;230'-Tertiary volcanic and 7,375' None 1.500'N: 700'W state-1.349 sedimntary rocks; l,3lO'-Lobo;6,550'-E1 Precambrian Paso:7,03O'-B1iss; 7.240-Precambrian

235-11W-10 WvtonSywz No. 1 10-22-74 4.556' KB Surface-Quaternary:2W"hertiary volcanic and 10,090' Oil: 6,670'- 660's: 330'W St. L-6,350 sedimentary rocks?;7,612'- above6.720.;Preoambria? 2,0OO'-Lob;6,530'- H ontoya; 7,160"ElHontoya; Paso: 7,630'-81isn:7,632'7.775'- Precambrian

~__~~~ 23s-llW-16 Guest and Wolfson 3-21-73 4,548. m Surface-Quaternary;9O"Tertiary volcanic7.927' and None 1,980.N: lr980'H No.rocks;sedirentary 1 Diana 2.680'-Lobo:Paso; 6,590"El Bliss 7.835*-Bliss:

28s-5W-19 Skelly No. 1-R 1-13-64 4,029' KB Surface-Quaternary;700'-hrtiary Volcanic9,437. and None 560.S; 1,980.E state c andsedimentary rocks; 3,90O~-lCbo?:5,130'- Pcecantxian Tertiary-Cretaceousvolcanic ro-zks; 8,388'- Hontoya; 8.622"El PaPo;8.786"faUlt. PreCm- brian v) 9 28s-5H-27 Hid-Cant.Sunray 3-24-62 4.097' XB Surface-Quaternary8550'-Tertiary 6,626'volcanicrocks; Gas: 5,582'- z 1,980'Ni 1,980'W No. 1 Federal R 2.886'-Fussehn3,536'-mntoyalPzecmbeian (Ti):4,354'- 5,619' --I SimpsM; 4,730"El Pais0 (Ti);6.396'-Bliss (Ti); 6,569'-Precambrian .x z0 miiA An4 couurf: U v) 22s-1U-27 Sinclair No. 1 4-7-62 4.684' GL Surface-Quaternary; 60"Santa28O'-Tertiary 6,519'Fei None 0 660.N: 66O'W660.N: msa Ana Fed. 18 2,846"fault.Hagdalenarocks;(Ti);volcanic hrt. intrus. z 3,654"Lake Valley:3,922"Percha (Ti); 4.304" IBliSSI - Fusselwn; 4,580"Hontoya;4,970"El Paso(Ti): - 6,330"Bliss(Ti)

~~ - ~~ ~ 225-2114 cities service NO.1 7-24-71 . 4.786' KB Surface-hrtiaryvolcanic and sedilnentary rooks; 5,129' None 1,980'N; 1,98O*W Corralitos Fed. A 1.055'-upper HY~CO;1,734'-&0; 2,094'-louer Bliss meCo: 2,222'-mgdalena;2,986'-~ake valley: 3,26O'-Percha;3,58O'-Fusselman; 3,89O'-Ebntoya: 4,240"ElPaso; 5,06O'-Bliss

23s-In-15 Picacho No. 1 5-15-414.480' GL surface-Quaternary;200*-santa ~e:265"Tertiary 3.196' Gas: 2.435': 660'N;1,980.E volcanicARn~tron9 reeks: 1,67Os-Teztiaryred mudstones lake Valley? 2.620' (Lobo?); 1,806"Tertiarytuffaceous sandstones andgray mudstones; 2,34O'-Hueco;2,76O'-M9&- lena?: 3,lOO'-Lake Valley?

235-2E-36 Snowden and Clary 11-1-49 4.240' GL Surface-SantaFe; 526'-Hueco: 2.475'-Hqdalena? 2.585' Gas deadand 106'N:41'H NO. 1 State mgdalena? oil: 553"573': oil: 573.: 1,025' -1,035';1,161': oil and gas: 1,492'-1,518'; 2,540"2,560' OIL AND GAS143 EXPLORATION WELLS

2.595 ft of valley fill and #iary volcanic rocks and encountered theEpitaphColina (Permian). On the Winkler anticline in the central Animas Moun- tains, the KCM No. 1 Forest Federal well drilled relatively unaltered Earp (Permian) and upper Horquiila down to 2,225 ft. Below that depth, the well penetrated meta- morphosed Horquilla and a Tertiary intrusive complex of quartz monzonites. This location fails between two volcanic cauldrons (Thompson and others, 1977; Elston andothers, 1979); The Humble Oil & Refining Co. (Exxon) No. 1 State BA was drilled on the Alamo.Hueco anticline along the east side of the Playas Valley. It penetrated the lower partof the Lower Cretaceous section and a nearly complete Paleozoic section down to the total depth of 14,585 ft. With the ex- cellent set of cuttings and logs, the formation tops could be determined accurately. Several lithologic and log marke,rs were used to document a repeated section of Epitaph-below a reverse fault at 3,310 ft. Less evident was a reverse fault at 14,120 ft where Escabrosa (Mississippian) was believed to lie below El Paso (Ordovician) (Thompson inZeller, 1965, p. 116). During the present investigation, small samples were selected above and below 14,120 ft to get biostratigraphic determinations. A.C. Seiby of ARCO Exploration Co. submitted the samples to the research department where T.R. Carr identified Ordovician cono. donts and D.E. Potter identified graptolites bothabove and below 14,120 ft. This evidence indicates that the section from 13,214 ft to totaldepth is in the Ei Paso and that the previous interpretation of a reverse fault at 14,120 ft is erroneous. Appreciation is expressed to ARCO and the individuals involved for clearance to publish this significant information.

GRANT COUNTY A total of 7 Detro1eum:expioration wells have been drilled in Grant County (one was located north of the map area of Fig. 1). Of these, only two have been drilled to pre- Laramide units. They also were included in the recent report on petroleum.source units (Thompson, 1981). The Cockrell No. 1 Coyote State was drilled inthe northern part of the Hachita Valley. Valley fill and Tertiary volcanic rocks were penetrated down lo 7,790 ft..Below the unconformity at that depth, a complete section of the Bisbee Group (Lower Cretaceous) was penetrated down to 7,240 it. Below the unconformity at that depth, Only lower Paleozoic strata are preserved. A slight show of oil was found in Mojado sandstones by the mudlogger; however, on two drill-stem testsonly fresh water (chloride contents 150 and 120 ppm) was recovered, indicating fiush- ing by meteoric water from the Burro uplift area to the north. Only a drilierk log is available on the Wininger and Berry well. Previous reports of Mississippian rocks at the surface and Ordovician rocks at the total depth of only 1,500 it are considered erroneous. Near that location in the Litfle Hatchet Mountains the Ringbone Formation (uppermost Cretaceous) crops out. The reported shows of oil and gas are probably in the Mojado. 144 e.SAM THOMPSON 111 e South of the RobledoMountains, the Sinclair No. 1 LUNA COUNTY Dona Ana Federal 18 drilled valley fill and Tertiaryvolcanic Of the 17 wells drilled in Luna County, five definitely rocks downto 2,846 ft. At that depth, a fault contact with have reached pre.Laramide units, and one recent well may the underlying Magdalena (Pennsylvanian) was inferred by have. Others which have been drilled to 2,000 ft or more Kottlowski andothers (1969, p. 192); however, it may be an in the northern and eastern part of the county appear lo unconformity on the Robledo uplift. A nearly complete have reached red beds of the Lobo Formation (uppermost section of Paleozoic strata was penetrated down to the Cretaceous to lowermost Tertiary), which overlies the Bliss (Cambrian-Ordovician), but several units were in- Laramide unconformity. truded byTertiarydiorites. All five of thekey wells were checked in an earlier study On the east side of !he Mason Draw anticline, the Cities (Thompson and others, 1978). In the present investigation, Service No. 1 Corralitos Federal (Government) A drilled formation topswere rechecked with available cuttings and Tertiary volcanic and sedimentary rocks down to 1,055 ft logs and some revisions were made. Further revisions Selow the inferred unconformity at thatdepth, the interval may be necessary after each well is studied in detail and down to 1,250 ft consists of greenish gray mudstones and biostratigraphic control isadded. tan cherts (concretions?) which may be as young as Upper In the Mimbres Valley area northwest of Deming, the Cretaceous. The dolostonellimestone section from 1,250- Cockrell, Sycor Newton, and Guest and Wolfson wells 1,734 ft resembles the EpitaphlCoiina of Hidalgo County encountered iower'Paleozoic strata beneath the Laramide and may be a Yeso equivalent. However, the interval be- unconformity. Individual units should be documented tween 1.,055.1,734 ft is designatedupper Hueco following with conodonts or other index fossils. Nevertheless, the the stratigraphic column for the Robledo Mountains shown lithostratigraphic evidence confirms the fact that younger by Kottlowski (1960b). Beneath the Abo and lower Hueco, Paleozoic and Mesozoic strata have been eroded off this a Paleozoic section similar to that in the Sinciair wellwas subsurface portion of the Burro uplift. Above the uncon- penetrated, but no Tertiary intrusive rocks were en- formity, the Lobo is about 4,000.5,OOO ft thick and may be countered. Several porosity zones were detected in the filling a narrow LaramideJrough trending northwest- Paleozoic carbonates. Low-chloride waters recovered on southeast (parallel to the San Vicente Arroyo). The Lobo drill-stem testswere considered previously to be products is only 500 ft thick in the Florida Mountains southeast of flushing by meteoric water (Thompson and Bieberman, of'Deming (R.E;Clemons, personal communication, 1982). 1975,p. 171). However, large negative deflections on the Near Deming, two recent wellswere drilled by the Seviile spontaneous-potential curve indicate that the formation Trident Corp. Their No. 1 City of Deming (24s-8W.8) was waters are salty (even at depths as shallow as 3,000 ft), drilled in 1981 to a total depth of 4,225 ft and probably did and the small volumes of water recovered on the tests are notreach pre-Laramide units. Their No. 1 McSherry now interpreted as filtrates fromthe drilling mud. (24s-8W-4)was drilled in 1981-1982 toa.total depth.of 12,495 The Picacho No. 1 Armstrong was drilled 3 mi south- ft and probably went into Precambrian. Because these west of Picacho Mountain, a prominent Tertiary intrusion wells were drilled tight, no cuttings or logs were available west of Las Cruces. Previously, the interval from 1,670- for use in the present investigation. Shows of gas have 2,340 ft was placed in the Love Ranch Formation (Thomp. been tested in bothwells. son and Bieberman, 1975, p. 173 and Uphoff, 1978, p. 62). North of Camel Mountain, in the southeastern part As a result of the present study of the cuttings, the red of the county, the other two key wells also encountered mudstones from 1,670.1,806 ft were correlated tentatively lower Paleozoic strata beneath the unconformity on that with the Lobo (= Love Ranch), and the tuffaceous sand- portion of the Burro uplift. Cuttings in the Skelly well are stones and mudstones from 1,806.2,340 ft were designated of poor quality; however, a.normal fault with at least as an unnamed unit ofprobable Tertiary age. Cuttings are 1,675 ft of stratigraphic throw appears to have beencrossed of poor quality below 2,340 ft, and they are lacking below at the El Paso/Precambrian contact. The total throw may 2,688 ft. Formation tops of the Hueco, Magdalena, and be nearly 4,000 ft because the top of the El Paso is 3,960 ft Lake Valley were determined tentatively from descriptions higher in the Sunray well (3 mi tothe southeast). A red-bed on the sample log by Geological Service (Permian Basin section between 3,900-5,130 ft in the Skelly well is corre. Sample Laboratory). lated tentatively with the Lobo Formation. It overlies an The Snowden and Clary No. 1 State was drilled one mile andesitic-volcanic section which may be as old as upper- south of Tortugas Mountain, an isolated exposure of most Cretaceous. Normally, the Lobo and its correlatives Hueco(?)-Bursum (Permian) limestones (King and Kelley, underlie a Cretaceousor Tertiary volcanic section. 1980). Subsurface information is meager and cuttings are available only from 1.420-1,865 ft. Tops of the Hueco DONA ANA COUNTY and Magdalena (including Bursum) were determined tenta- The 14 wells drilled inDona Ana County were discussed tively from the descriptions by Kottlowski and others by Thompson and Bieberman(1975). That work was based (1956, p. 82). on reported information. Other references on these Wells include: Kottlowski and others (1956, 1969), Kottlowski The J.F. Grimm, N.B. Hunt, G.R. Brown, and Am Arctic (1973), Foster (1978a, and 1978b), and Uphoff (1978). In the Ltd. No. 1 Mobil 32 was drilled in the Mesilla Bolson on present investigation, formation tops were checked with the La Mesa surface. This well set a depth record for the available cuttings and logs on the 6 key wells drilled IO region of 21,759 ft; it penetrated thick sectionsof Cenozoic, pre-Laramide units. Mesozoic, and Paleozoic strata. An extensive operator's GAS EXPLORATION WELLS 145 0- report by J.F. Grimm was published in Thompson and present investigation, cuttings and logs were used to Bieberman (1975, p. 173.174). A thorough study of this well determine the stratigraphic boundaries, but these results .was made by Uphoff (1978). For the present investigation, are preliminary. Because much of the well was drilled with the sample log by Fred Dumas (Permian Basin Sample air, the cuttings generally are too small for definitive litho- Laboratory) provided the basic lithostratigraphic control, stratigraphic analysis. Some of the larger chips could be and the generally good cuttings were used to spot check the results of sloughing and may not be representative formation tops. Unfortunately, the wire-line logs have not of the drilled intervals. A few core chips are available. been released yet. The Purewell appears to have beenspudded in the oldest Biostratigraphic.determinations in the Grimm wellwere Lower Cretaceous unit mapped by Bowers (1960). He also obtained recently fromA.S. Murer and R.A. Wetherhead of mapped Hueco(?) limestones along the Basin and Range Mobil Producing Texas & New Mexico, Inc. Tertiary, Cre- boundary fault: The interval from 625.3,850 ft appears to taceous. and Jurassic determinations with palynomorphs contain limestones, dolostones, cherts, and mudstones; were made by J.E. Gerhard and those with foraminifers it isdesignated as Permian? to Mississippian? undifferen- and other microfossilswere made by D.J. Gauger, both of tiated. Fortunately, casing was set at 3,831 ft, and the Mobil Field Research Laboratory. Permian and Pennsylvan- cuttings down to 4,400 ft are relatively good. Dark, highly ian determinations with fusulinids were made by R.V. radioactive mudstones between 3,850.4,060 ft are inferred Hollingsworth of the Paleontological Laboratory. Appre- to bePercha, and the light, coarsely crystalline dolostones ciation is expressed to Mobil and the individuals involved between 4,060-4,405 ft are inferred to be Fusselman. Both for permission lo publish this important information. determinations should be checked with biostratigraphic The interval between 5,880-12,100 ft in the Grimm well evidence. contains reddish brownmudstones, sandstones, and con- A reverse fault is inferred at 4,405 11 where circulation glomerates; it i+ correlated tentatively with the Lobo. The was lost in a possible fractured zone, and where the dip- interval between 12,100-13,000 ft contains brownish gray meter shows an abrupt reversal from southeast above to mudstones, sandstones, and carbonaceous material with northwest below. Cuttings again are poor below 4,600 ft, palynomorphs dated as Late Paleocene to Early Eocene. but the dominant carbonatesection appears to be a repeti- This age determination provides the first'evidence thatthe tion of the Permian? to Mississippian? undifferentiated Lobo.( = Love Ranch) may be no older than Early Tertiary unit. The abundance of clear calcite crystals beginning in the Doha Ana Countyarea. at 6,240 ft indicates that the lower part of the sedimentary The intetval beiween 13,300-14,100 ft contains sand- section has been marbleized in contact with the Tertiary stones and gray to black mudstones; it is designated as intrusivediorite below6,815 11. Sarten (Lower Cretaceous). Paiynomorphs, foraminifers, A slight show of gas in the drilling mud was recorded and ostracods indicate an Albian to Cenomanian age. between 4,380.4,400 ft. A drill-stem test from 4,354.4,412 ft An unnamed Jurassic section is designated between recovered 3,480 It of mud-cut water with a chloride content 14,100.15,550 ft; it contains black mudstones, dark lime- of 4,000 ppm. The spontaneous-potential curve shows a stones, and sandstones in the upper part. Palynomorphs pronounced positive deflection through this Interval, in- indicate an Oxfordian-Callovianage between 14,100-14,250 dicating invasion of meteoric water into the fault zone. ff, and arenaceous foraminifers indicate a Jurassic age This Pure well is another case illustrating the point that, between 14,120-14,450 11 and at 15,130 ft. The dark aspect in the Basin and Range province, uplifted areas tend to be of these rocks, and the lack of a distinct lithostratigraphic flushed withfresh water. break across the subtle unconformity (where the lowermost Cretaceous and uppermost Jurassic are missing), suggest REGIONAL ISOPACH MAPS that they were deposited in a deep.marine environment Kottlowski (1963) presented a series of regional isopach within the Chihuahuatrough. maps showing thicknesses of individual Paleozoic and A tentative top of the Hueco is placed at15,550 ft, but it Mesozoic units across southwestern and south-central may be as high as 15,270 ft at the.top of the crinoidallime. New Mexico. Greenwood and others (1977) presented a stones. Wolfcampian fusulinids were determined between similar series of maps covering southeastern Arizona. 15,680-19,080 ft. Magdalena (Pennsylvanian) 'is desig- southern New Mexico, western Texas, and northern Mexico. nated between 19,080-20,560 ft and consists of limestone, Such overviews of stratigraphic units, especially if com- chert, sandstone. and mudstone. Missourian (Canyon), bined with delineations of depositional facies, are useful Desrnoinesian, and Derryan (Atokan) fusulinids were de- in regional projections of petroleum source and reservoir termined between 19,120-20,510 ft. Tops of older Paleozoic objectives. units were based solely on lithostratigraphy. The well In this short paper, only two isopach maps of south- bottomed in Montoya (Ordovician) dolostones. Several western New Mexico are presented one each for the shows of oil and gas were described by the mudlogger. - Paleozoic and Mesozoic. They provide the most basic step Seven drill-stem tests were attempted, but none was in analysis of the two most general stratigraphic units completed. containing the significant petroleum source and reservoir The Pure No. 1 Federal H was drilled on the northeast objectives in the region. Exploration geologists may find side of the East Potrillo Mountains. Previous interpretations them useful for gross estimates of: 1) burial history of are discussed by Kottlowski and others (1969, p. 190-192) source units, 2) distribution of source and reservoir units, and by Thompson and Bieberman (1975, p. 174). In the and 3) drilling depths to test complete sections. They also - 146 SAM THOMPSON 111 a- e reflect generally the cumulative effects of tectonic uplift between the basal Paleozoic unconformity and the basal and subsidence. Mesozoic unconformity. At most places, both boundaries Thicknesses of the Paleozoic and Mesozoic at-the well are considered lo be accurately determined within 100 It locations in southwestern New Mexico were determined of section. In undisturbed sections, the only problemswith directly from the drilled intervals given in Table 2. True the lower boundary are at locations where the basal Bliss stratigraphic thicknesses of these gross units may be sandstones are arkosic and differentiation with underlying considerably less, especially where dips are appreciable. Precambrian granite is difficult,especially in well cuttings. However, such corrections wouldbe feasible in onlythose In the southeastern part of the map area, the upper few wells where dipmeter surveys are available. Thick- boundary was determined with some difficulty within nesses of sills or other minor Tertiary intrusions generally 200-300 ft of section because dark carbonates or mud- were not discounted. Values shown at locations of Pemex stones of the Jurassic are superposed on similar-rocks wells in Chihuahua, Mexico were calculated from data in of the Permian. Thompson and others(1978, Table 4). Small areas of erosion Thicknesses shown,atsurface locationson this isopach sketched around wellsites are rough estimates in most map were determined from several sources. In Hidalgo cases and are shown to emphasize the fact that the unit County, they are Zeller (1965;measured 11,489 ft), Soule is only locally thinor absent at that control point. (1972;reported incomplete section of 3,465 ft), and Giiler- Thicknesses at surface sections were determined from man (1958; measured 5,643 ft). In Grant County. they are publications and other sources listed under the Paleozoic Cunningham (1974;measured 1,945 ft) and Pratt (1967; and Mesozoic headings. Data range in qualityfrom precise measured and estimated 3,269ft). in Luna County, they are measurements to gross field estimates as reported by Jicha (1954;measured 2,274 It), Kottlowski (1960a PI. 13; different workers. Most are totals of composite sections measured incomplete section of 1,735 It), Thorman and located in separate parts of a given mountain range. in Drewes (1981,estimated 2,430 ft), and RE. Clemons (current some cases,’such stacking of even precisely measured study; measured 1,565 It and 3,720 ft). In southern Sierra sections may result in a composite thickness that is not County, the one is Jicha (1954;measured and estimated as representative of a single location as the uncorrected 1,824 ft). In Doria Ana County, they are Keiley and Silver drilled interval in a well bore. Where a range of thick. (1952; measured 4,300 ft). Seagei and others (1971;meas- nesses was reported for a given unit, the maximum was ured 425 ft). Kottlowski and others (1956;measured 7,130 chosen as long as it appeared reasonable in comparison ft), Kottlowski (1960b;measured and estimated 4,300 It), with nearby control. Locations were placed at the top of and Seager (1973;measured incomplete section of 3,075 the Paleozoic or Mesozoic sections to indicate where the ft). In El Paso County, Texas, the one is Harbour (1972; reported thicknesses should be present in the subsurface. measured 8,426 It). in Chihuahua, Mexico, the one is Diaz Some of the previously published sections contain errors and Navarro (1964;measured and estimated 10,675 ft). of omission or duplication resulting from low-angle Estimated thicknesses are of nearly complete sections thrusts, which have been discovered in recent mapping with additions from the nearest control. (H. Drewes, personal commun., 1982). Most of the formations in the Paleozoic are shallow- The extent of local Quaternary erosion around the surface marine carbonate deposits.They generally were deposited locations was not shown to avoid a cluttering effect on over the entire region andare missing in most cases as a these small-scale maps, but it may be observed at the result of subsequent erosion. Unconformities within the outcrops of Precambrian, Paleozoic, and Mesozoic rocks Paleozoic are recognized at the bases of the Montoya, indicated on the geologic map of New Mexico by Dane Percha,Horquilia-Magdalena, Earp-Abo.Hueco, and and Bachman (1965). This map and others were used for Scherrer-Glorieta. In this area, most exhibit low relief, regional control todetermine key surface locationswhere and the hiatuses normally include only parts of the under- the Paleozoic or Mesozoic are present or absent by non- lying units. However, at the basal unconformity of theEarp- deposition or erosion priorto Quaternary time. Abo-Hueco, the entire Horquilla-Magdalena and older Thickness data from other wells and surface Sections units locally have been eroded. Nevertheless, the depo- immediately surrounding the map area were used to sitional extent and preservation are documented by the control the contour trends. The contour interval of 1,000 ft fact that each key well drilled below the Mesozoic has en- is considered small enough to show significant regional countered at least some part ofthe Paleozoic. features and large enough to smooth over minor local Where the Paleozoic thickness is greater than 5,000 It, variations. more complete Pennsylvanian-Permian sections are preserved. In the southern partof the map area, the Paleozoic PALEOZOIC attains a thickness of 15,000ft, and the Pennsylvanian- Figure 2 is aregional isopach map of Paleozoic Strata in Permian part is over 12,000 It. Part of that thickening is attributed to the Pedregosa basin, a Pennsylvanian basin southwestern New Mexico. It confirmsmany of the regional thickness trends shown in the earlier version by Kottlowski of subsidence (Kottlowski, 1960a). Similarly, in the eastern part of the map area, the Orogrande basin, another Penn- (1963,Fig. 2). With the addition of several subsurface sec- sylvanian basin of subsidence, contributed to the thick- tions from more recently drilled wells, and of additional or better documented surfacesections, the major features ening of thetotal Paleozoic to over 8,000 ft. are more sharply delineated. On the Moyotes ridge, uplift and erosion in mid-Wolf- This isopach map includes all the units shown on Table 1 campian time formed a boundary between these tWO UIL ANU CiAS tXYLUHAI IUN VVCLL3 e a 148 e SAM THOMPSON Iii Pennsylvanian basins. In the southeastern part of the stones, limestones, and cherts resembled the Epitaph Florida Mountains, Hueco rests unconformabiy on Lake (Permian). A.C. Selby of ARCO Exploration Co. collected Vaiiey, and in the Pemex No. 1 Moyotes, Abo-Hueco rests a sample andsent it to T.R. Carr who identified conodonts unconformably on Precambrian. On the Burro uplift, in of Early Leonardian age. Appreciation is expressed to the northwestern part of the map area, the Paleozoic was ARCO and the individuals involved for clearance to publish completely eroded in Mesozoic time, as Beartooth (Cre- this important information. taceous) rests unconformably on Precambrian (Elston, Inferred depositional limits of ihe undifferentiated 1958). Laramide uplift and erosion, possibly along Pre- Jurassic, Bisbee Group (Lower Cretaceous), Sarten (Lower cambrian shearzones, appears to beresponsible for linear Cretaceous), and undifferentiated Upper Cretaceous are thinning of the Paleozoic on the San Vicente (to Moyotes) shown on the isopach. These limits provide explanations and Robledo ridges, as Lobo (or Love Ranch) rests uncon- for some of the regional thickness patterns. formabiy on rocks as oia as Lower Paleozoic. On the in the southeastern part of the map area, the depo- complex Florida uplift, at the intersection of the ridges, sitional limit of the Jurassic lies within the Chihuahua Lobo rests unconformabiyon Precambrian (R.E. Clemons, trough of Navarro and Tovar (1975). In this trough, subsi- current study). On,the San Diego uplift, Love Ranch rests dence probably was more rapid than sedimentation, as unconformabiy on Lower Paleozoic rocks (Seager and the Jurassic black mudstones, dark limestones, and sand- others, 1971); it appears to be a local anomaly. On the Lake stones appear to have been deposited in a deep-marine Vaiiey uplift, Tertiary volcanic rocks rest unconformably environment. These basin-filling strata may oniap the on Lake Valley (Mississippian) (Jicha. 1954). bottom of the trough. The Jurassic ranges in thickness An isopach of the Bliss by Thom'pson and Potter (1981, from 1,400 ft in the Grimm weii to at least 4,800 ft in the Fig. 1) shows the paleotopography on top of the Pre- Pemex No. 1 Sapallo, and possibly over 13,500 ft in the Cambrian. The most strikingfeature is the northeast-south- Pemex No. 1 Presidio. west trending crest of the ancestral continental divide ex- The northern limit of the Bisbee Group trends nearly tendingacross southwestern New Mexico (passing east-west across themiddle of the map area. As described through the Hatch-Florida area). it ais0 may follow a Pre. by Zelier (1965) in the Big Hatchet Mountains of Hidalgo Cambrian shear zone. Because this feature is not evident County, the Bisbee is 9.969 ft thick and consists of three 'on'the total Paleozoic isopach, it apparently was not re- units: 1) Hell-to-Finish conglomerates and redbeds, 2) U-Bar juvenaied in post-Blisstime. limestones containingthe distinctive orbitolinid foraminifers and rudist pelecypods in the upper part, and 3) Mojado sandstones and mudstones.These units generally MESOZOIC are recognizable from the type area of the Bisbee Groupin Figure 3 is a regional isopach map of Mesozoic strata southeastern Arizona to western Texas where the succes- in southwestern New Mexico. it 'includes all the units on sion corresponds approximately to the Trinity, Fredricks- Table 1 betweenthe basal Mesozoic unconformity and burg, and Washita of the Comanchean. A regional uncon- the Laramide unconformity. it excludes some nonmarine formity is evident at the base, but none has been docu- sedimentary rocks and volcanic rocks of the uppermost mented withinthe Bisbee. Cretaceous. in the Hidalgo County area, the 10,000 ft or more in the Thicknesses shown at surface locations on this isopach Bisbee basin is projected from control in southeastern map were determined from several references. in Hidalgo Arizona, as is the thin section on the Chiricahua ridge. The County, they are Zelier (1985; measured 9,969 ft), Zelier and Little Hatchet basin may not contain the entire 15,000 ft Aiper (1965; measured 7,619 ft), Gilierman (1958; meas- estimated by Zeiier (1965), but at least 10,000 ft are present. ured and estimated 2,500 ft), and Elston (1960; measured Regional thinning tothe north appears to be mainly at the 860 ft). in Grant County, they are Zeiler (1970; measured expense of the U-Bar, although the entire Bisbee appears and estimated 15,000 ft), Hewitt (1959; measured 1,160 ft), to oniapan earlier Mesozoic highland. Edwards in Gilierman (1964, measured incomplete section In southern Doha Ana County and northern Chihuahua, of 273 ft), Cunningham (1974; measured 1,555 It), and Pratt different nomenclatures are applied to the Bisbee equiva- , (1967; measured 1,755 ft). in Luna County, they are Jicha lents described by Bowers (1960) in the East Potrillo Moun- (1954, estimated 600 ft), and Kottlowski (1960a.PI. 13; tains, by Lovejoy (1976) in the Cerro de Cristo Rey, and measured incomplete section of 800 ft). in. Doiia Ana by Lovejoy and others (1980) in the Sierra de Juarez. This County, they are Kottiowski and others (1956; measured Lower Cretaceous section thickens to over 12,000 ft in 707 ft), Bowers (1960; measured incomplete section of the Pemex No. 1 Sapaiio, after which the Sapallo basin is 1,585 ft), and Lovejoy (1976; measured incomplete section named. of 1,361 ft). In Chihuahua, Mexico the one is Lovejoy and others (1980; measured incomplete sectionof 5,665 ft). The southern limit of the Sarten appears to trend north- Note that Mesozoic rocks are shown as absent at the west-southeast across the northern part of the map area locality in the Tres Hermanas Mountains (northwest of (Fig. 3). At the type section in the Cooke's Range, the Sarten Columbus). Kottlowski and Foster (1962) measured an in- is about 300 ft thick and consists mostly of sandstone complete section of 1,530 ft which they designated as (Jicha, 1954, p. 26). it is late Albian to early Cenomanian Lower Cretaceous on the basis of a few poorly preSeNed in age (S.C.Hook, personal communication, 1982). The pelecypods. At that stopon the 1981 field tripof the Ei Paso Sarten has been recognized also in the southern part Of Geological Society, some of us observed that the dolo- the San Andres Mountains (Kottiowski and others, 1956, OIL ANU tiAS tXVLUliHI IUIV'VVCLLJ

r 150 SAM THOMPSON 111 e 0 p. 62.66; Seager, 1981, p. 33) and in the lower part of the (late Cenomanian-Turonian), positions reversed from land Beartooth (unrestricted) in the Silver City area (Pratt, 1967, on the northand sea on the south to landon the southwest p. 42-44; S.C. Hook, personal communication, 1982). . and sea on the northeast. The uplift of the southwestern The southern limit of the Sarten may represent oniap area probably was associated with the northeastward ..: on the northern sideof an earlier Mesozoic highland trend- migration of the Cordilleran magmatic arc (Damon and ing west-northwest to east-southeast through the Deming others, 1981). During continued migration in Laramide time, area. Alternatively, the Sarten maybe a northernextension the sea finally withdrew from the region. of the upper Mojado; they are similar in lithofacies and Laramide upliftand erosion stripped Mesozoicand older both containthe diagnostic foraminifer Haplosfiche ft?Xana rocks from much ofthe Burro andother uplifts shownon (Zeller, 1965, p. 68. and S.C. Hook, personal communica- Figure 3. The remainder was eroded in Cenozoic time. tion, 1982). As such, the Sarten would represent the last Upon fhe Laramide unconformity,. conglomerates and unit ina northward onlappingLower Cretaceous succession redbeds were deposited, followed by andesitic volcanic of Hell-to-Finish, U-Bar, and lower Mojado. The northern rocks. The Ringbone.Hidalgo succession in Hidalgo-Grant limit of the Sarten iies around .the northern boundary of Counties is uppermost Cretaceous (Campanian-Maestrictian) the map area (Fig. 3). Its absence in the Deming area would in age (Hayes, 1970, Fig.5; Marvin and others, 1978, Table 1, then beexplained as a resultof subsequent erosion. sample A); the Lobo-Rubio Peak and Love Ranch-Palm Park Recognition of Sarten in the Grimm well extends its successions in Luna-DoRa AnaCounties are lower Tertiary previous usage to the south and lends support to the al- (PaleoceneEocene) in age (this paper, Grimm well; Seager ternative interpretation of an upper Mojado extension. If and others, 1975, Table 1; and R.E. Clemons, personal later evidence confirms this relationship, the southern communication, 1982). These relationships of decreasing limit of the Sarten would not be a depositional limit but age to the northeast also reflect the migration of theCor- only an arbit.rary cutoff between Sarten and Mojado (Bisbee dilleran magmatic arc in Laramide time (Damon and others. Group). 1981). The southern limitof undifferentiated'upper Cretaceous also trends generally northwest-southeast across the CONCLUSIONS AND RECOMMENDATIONS northern, part of the map area (Fig. 3). included are deltaic- Paleozoic and Mesozoic strata of southwestern New marine, sandstonemudstone units called Beartooth (re- Mexico and adjoining areas contain several petroleum stricted)Colorado (Pratt, 1967, p. 42-44) or Dakota-Mancos source and reservoir units. In Hidalgo-Grant Counties, (Kottlowski and others, 1956, p. 66-68; Seager, 1981, the source units appear to have generated abundant gas p. 33-34); they are equivalent to the Woodbine. Eagle Ford and moderate amounts of oil (Thompson, 1981). The best of Texas (Hayes, 1970, Fig. 5). The upper part of the reservoir objective in that area is the upper Horquilla (Pen-. Colorado contains nonmarinesandstones and mudstones nsylvanian-Permian), which contains thick porous dolo- which probably are equivalent to the Mesaverde. The un- stones at the margin of the Alamo Hueco basin, a deep- conformity between the Sarten and Beartooth (or Dakota) marine basin lying within the Pedregosa basin (Thompson occurs within the Cenomanian; other unconformities are and Jacka, 1961). Documentation of source and reservoir documented within the Turonian part of the Colorado (Hook units is continuing inthat area and adjacent parts of south- and Cobban, 1981; and S.C. Hook, personal communication, western New Mexico. Projection of these objectives into 1982). Together, the Sarten and the Upper Cretaceous subsurface prospects is directly dependent upon the units are less than 2,000 ft thick in the northern part of accuracy ofthe stratigraphic.sedimentologic framework. the maparea. Documentation of lithostratigraphic and biostratigraphic The Upper Cretaceous limit curves southward as a result boundaries in the Paleozoic and Mesozoic has progressed of absence in the Grimm welland presence in the Cerro de well, but some surface sections and many subsurface sep Cristo Rey and Sierra de Juarez. In those two surface tions need additional control before detailed isopach- sections, the Upper Cretaceous is called Boquiilas For- facies maps of individual units can be made with a high level mation and consistsof 360 ft of dark mudstones and thin of confidence. Continuing studies of biostratigraphy, limestones; it isCenomanian to probably Turonian in age paleoecology, and microfacies by D.V. LeMone and his (Lovejoy, 1976, p. 20; Lovejoy and others, 1980, p. 27). students, at the University of Texas at El Paso, are adding These Upper Cretaceous rocks are absent over a large much of theneeded control. area covering southwestern New Mexico, southeastern In the Paleozoic, the Cambrian-Ordovician-Silurian units Arizona, and northern Mexico (Hayes, 1970, Fig. 5). The were deposited over a broad shelf, so their regional facies southern limit shown on Figure 3 may represent a depo. problems are minimai. Some changes are evident in the sitional boundary with southwestward onlap onto a low- Devonian, but the Mississippian shows major differentia- relief land area. Alternatively, this limit may represent an tion into shelf, margin, and basin facies which need ac- erosional boundary with the onlap boundary lying originally curate delineation. Similar major facies changes are an unknown distance to the southwest; however, it is evident in the upper Pennsylvanian-lower Permian; their likely that such a distance was less than 100 mi, because regional delineation has important economic significance at least one remnant section should have been preserved regarding projection of the porous dolostones in the margin ifthe distance hadbeen greater. facies. Additional documentation of the deep-marine de- In any case, between the time of U-Bar deposition posits in the Pedregosa and Orogrande basins is needed; (Aptianearly Albian) and that of the Upper Cretaceous units the 'southern terminations of these basins may form a O IL AND GAS EXPLORATION WELLSGAS AND OIL 13 I

rift-rift-rift triplejunction relationship withthe Marfa basin, Detroleum beneath either tyb es of thrusts amears slim.In similar tothat shown byElam (1982)for the Marfa-Deiaware- ihe KCM No. 1 Cochise Siate A, kerogens.in the Mojado Valverde basins in westernTexas have reached a high degree of thermal alteration beyond ' In the Mesozoic, the recently discovered Jurassic unit the limits of oil preservation, and in older units even gas in the Grimmwell prompts re-examination of other sections may not be preserved. This section probably was buriedby in the region which containthe Paleozoic-Mesozoic boun- the major thrust fault seen in the Hidalgo- County area dary lo see if equivalent units are present elsewhere. The (Thompson, 1981,p. 41). concept that the Jurassic is confined to deepmarine de. Studies of theCenozoic rocks alsoare useful topetrole- posits in the Chihuahua trough should be examined um exploration. An isopach map of all the unitsabove the critically. The Lower Cretaceous of the Little Hatchet Laramide unconformity, in combination with those ofthe Mountains (discussed by Zeiler, 1970) needs to be meas- Mesozoic and Paleozoic, would give a complete summary ured and described in detail, but the problem is complicated of the burial history of the region and provide a means by multiple thrusting. Northward onlap of the Bisbee Group of estimating drilling depths to Precambrian basement. should be documented with seismic sections. Especially Locations of volcanic centers,ash.fiow tuff cauldrons, and important is the relationship between the upper Mojado the thicknesses of outflow units inthe Tertiary andQuater- and Sarten; were they separated by a barrier, or were they nary are important considerations. Volcanologists working a continuous part of the northward onlap? Analyses of in southwestern New Mexico include: 1) in the Hidalgo- depositional environments and paleocurrents may help Grant Counties area, W.E. Eiston and students at the resolve this question. Similar studies may document the University of New Mexico; 2) in the Luna-Doria Ana Counties southwestward onlap of the Upper Cretaceous. Results area, R.E. Clemons and W.R. Seager, at,New Mexico State of these studies wiii be useful to exploration by delineating University, and 3) in the southern parts of Luna County, Doha unconformity traps along the onlapping edges of these Ana County, and adjacentTexas, J.M. Hoffer and students sandstones. Stiatigraphic-sedimentologic work on selected at the University of Texasat El Paso, who also are analyzing Cretaceous units is being done by H.S. Chafetz at the drill cuttings and cores of volcanic rocks in several wells. University of Houston, G.H. Mack at New Mexico State . Structure-contour maps on tops of the Precambrian, University, and their students. Paleozoic, and Mesozoic would complement the set of Important aspects of Laramide history may be de- isopach maps and provide basic data for a regional ciphered by investigation of: 1) Precambrian, Paleozoic, tectonic-stratigraphic synthesis. With continuing improve- and Mesozoic trends; 2) the Laramide unconforrnity itself, ments over the entire spectrum from surface mapping to and 3) the Lobo and correlative units overlying the uncon- subsurface analysis, a comprehensive geologic framework formity. As shown on the Bliss isopach (Thompson and can be developed for increased proficiency of petroleum Potter, 1981, Fig. l), the northeast-southwest trending crest exploration in southwestern New Mexico. of the ancestral continental divide formed on top of Pre- Within the next few years, several operators pian to drill Cambrian basement is relatively continuous across south- additional exploration wells. For thorough evaluation Of western New Mexico.Thiscontinuity constrains the amount the prospects, adequate drilling programs should be of any subsequent lateral offsetby tear or wrenchfaulting planned to: 1) obtain good cuttings for iithostratigraphic to a few tens of miles or less. Other depositional or (and biostratigraphic) analyses over the entire section erosional trends in Paleozoic and Mesozoic rocks also drilled; 2) employ hydrocarbon loggers to watch for oiland appear to be relatively continuous. Some workers have gas shows around the clock; 3) collect canned cuttings for ignored such.evidence in their tectonic interpretations source.rock analyses; 4) cut cores of major source and involving offsets of man tens to hundreds of miles. On reservoir units: 5) run drill-stem tests on any reservoir en- the regionalisopach malprepared for thispaper, no major countered, with or without a show of oil or gas, to measure lateral offsetsare indicated, but some may be documented subsurface pressures and provide samples of hydrocarbons with moredetailed study. or formation waters for analyses; and 6) run a full Suite Subcrop and supercrop maps of the Laramide uncon- of first-class wire.line logs. Such a complete program is formity would show the extent of erosional truncation expensive, but considering the great sums of money cur- below and the depositional relief above that important rently being spent on leasing, geophysics, and the basic surface. A narrow trough several thousand feet deep filled drilling costs themselves, the acquisition of essential with conglomerates and redbeds of the Lobo appears to subsurface data should begiven adequate consideration trend east-southeast from the three key wells west of within the total investment plan. Not only will such pro- Deming at least to the Grimm well. This trough may be a grams provide every chance for success on individual graben alongthe crest of a Laramide uplift, or i! may mark prospects, but also they collectively may determine whether the down (north) side of a major fault - reverse, normal, or ,lot southwestern New Mexico will become a productive or mainiystrikeslip. petroleum province. Laramide thrusting is evident at many localities in the region. Interpretations of regional overthrusts with hun- ACKNOWLEDGEMENTS dreds of miles of displacement remain controversiai. The In addition to specific acknowledgements mentioned alternative explanation of thrusts rising upward and out- in the main body of the text, I wish to express my thanks ward fromwrench zones should be considered (Thompson, to the reviewers of the manuscript, RE. Clemons andA.C. 1980, p. 210). Moreover, the potential for preservation of Selby, who have made several suggestions for improve- 152 SAM THOMPSON 111

ment. This paper is published with permission of F.E. Greenwood, Eugene, Kottlowski, F.E., and Thompson, Kottlowski, Director of the New Mexico Bureau of Mines Sam 111, 197.7, Petroleum potential and stratigraphy of and MineralResources. Pedregosa Basin: comparison with Permjan and Oro- grande Basins: American Association of Petroleum Geologists, Bull., v. 61, no. 9, p. 1448-1469. Harbour, R.L., 1972, Geology of the northern Franklin REFERENCES Mountains, Texas and New Mexico: U.S. Geological Bowers, W.E., 1980, Geology of the East Potrilio Hills, Doha Survey, Bull. 1298,129 p. 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