Paleozoic Sedimentary Rocks of Southwestern New Mexico Rousseau H

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Paleozoic sedimentary rocks of southwestern New Mexico Rousseau H. Flower, 1953, pp. 106-112 in: Southwestern New Mexico, Kottlowski, F. E.; [ed.], New Mexico Geological Society 4th Annual Fall Field Conference Guidebook, 153 p.

This is one of many related papers that were included in the 1953 NMGS Fall Field Conference Guidebook.

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PALEOZOIC SEDIMENTARY ROCKS were deposited the sands and silts which contain the OF SOUTHWESTERN NEW MEXICO most prolific successionaf trilobites in North America. by If the Bad Axe beds were consolidated and subjected Rousseau H. Flower to the weathering conditions of an arid, instead of a moist climate, they would look very muchlike the Bliss sandstone Bliss sandstone. The Bliss may be considered a "Bad Axe facies" laid downin the center of a basin. The Bliss sandstone(type section in the southern The marginal sediments to the west, in southern Franklin Mountains,near Ft. Bliss, whereit is 250 Arizona, contain a succession of Upper Cambrian feet thick) forms characteristic dark, often black faunas, beginning, as a matter of fact, in the Dres- weathering ledges which contrast strongly with the bachian which precedes the Franconian. Any red weathering Precambriangranites beneath, and marginal sediments to the north were removedby the overlying grey-brown weathering EI Paso lime- erosion and to the east were deeply covered. stone. The Bliss is dominantly a sandstone, with abundantglauconite and hematite, but also with a El Paso limestone considerable amountof dolornitic material in certain layers. The Bliss was originally considered Cambrian The El Paso formation consists of a group of on the basis of Lingulepis, which unfortunately is a limestones, with minor amountsof dolomite in New long ranging type and is not necessarily diagnostic. Mexico, with more abundant dolomite and somede- The discovery of Ordovician (Gasconade)fossils finitely sandy beds in the sections in western Texas. the northern end of BeachMountain in Texas raised Deposition extended throughout Canadiantime (often a controversy, someinsisting that the wholeBliss called Beekmantawnexcept by those who have seen was Ordovician, others that the lower part was Cam- the type section at Beekmantown,which is miserable). brian in Texas, and that the entire unit was Cambrian At the southern end of the Franklin Mountainsthe in NewMexico. Until recently, the fossils known lowest sediments are of Gasconadeage, lower from the Bliss sandstone in NewMexico were not Canadian0and the highest are equivalent to the Black diagnostic types, but did suggest an age of either Rock formation of Missouri and the Odenville lime- late Trempealeauor earliest Ordovician. stone of Alabama. In New Mexico the El Paso is generally considerably thinner than the 1590 feet Three recent discoveries indicate three different measuredat El Paso by Cloud and Barnes (1946), ages. Thefirst, of Ptychaspis striata and Chario- and post-Canadian erosion has removed variable cephalus, indicates middle Franconia age. The second, amountsof the upper limestones in different places. of Briscoia and Prosaukia, indicates late Franconia age. The third, the discovery of Bellefontia in association Kelley and Silver (1952) have treated the El Paso with l inguloids, ribbed brachiopods,and the graptolite as a group and separated it into two formations: Dictyonema,indicates earliest Ordovician, and is possibly the correlative of zone I of Rossin the Sierrite limestone - Generally thin-bedded lime- GardenCity formation of Utah (Flower, 1953, p. 2055). stones, sometimesslightly dolomitic0 and extensively dolomitized in the Hatchet Mountains. Bedding planes The Bliss represents~plainly, very slow and fre- are undulant or crinkled, and often highly styolitic. quently intermittent deposition which began, from our There are beds of limestone pebbles, and of.small present evidence, in the middle of the UpperCambrian, algal masseswsome spherical, sometubular and and continued into early Ordovician time. The diag- branched, but massive stromatolite beds are wanting. nostic fossils, all from zonesof 6 inches or less in The fauna indicates a correlation with the Gasconade, thickness, represent infrequent periods of morerapid though the top of the formation mayextend slightly deposition, higher than the Gasconadeand its equivalents in the east. The fauna is sparse. Clarkeaceras, Ophileta, The Bad Axe "formation" of Wisconsin and Symphysurina,and Histricurus have been collected, Minnesotawhich consists of glauconitic and ferruginous and a zone in the HatchetMountains has yielded sands, has been interpreted as representing an environ- Kainella and Leiostegium. ment of very slow deposition. Along the edgeof the basin, deposition was too slow for the preservation The Sierrite limestone ranges between100 to 175 of fossils in general, but in the center of the basin feet in thickness. About 100 feet of the basal dolo-

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LOWER PALEOZOIC STRATIGRAPHY OF SOUTHERNNEW MEXICO

Standardsectign f~9~M~ic 9 ~9~tign Percho Connewongoon

Choutoquon UPPER z Contodro ’~ Senecon Sly Gap O \\\\\\\\\\\ > Onote uJ Erieon o M I DDLE ~.~"~~’~ Ulsterion Oriskonian LOWER Helderbergion

Woterlirne CAYUGAN Solino Guelph N IAGARAN Racine Clinton

ALEXANDRIAN Medina ~~ ? Cutter "’ Richmond Alemon CINCINNATIAN Moysville ~\\~\~ Covington .... ~ Montoyo ~: Eden ~~ I Z Uphom Cable ~, Con. <~ Trenton MOHAWKIAN ~ > Block River O o C H AZYAN Chozy n- ~~ O Block Rock Smithville U. lowell Cotter _~ o CANADIAN Jefferson City o Bat Cove M. Roubidoux uJ Gosconode Sier rite Von Buren Trempeoleou BI i s s CR 0 I X I A N DFronconiores och A,.ERA W AUCOBIAN ~,,~~’~

mite at El Pasois the equivalentof this formation. Rockequivalents. The successionof the El Paso in NewMexico and western Texas is providing a Bat Cave formation - The Bat Cave contains more link betweenthe eastern sectionsin whichthe faunal massiveI~ds~ and is morepmminentlycliff-forming succession is based primarily upon the molluscs, thanthe Sierrite limestone.It is characterizedby a and the Utah sections in whichthe successionis widevariety of sedimentary typese but chiefly by based primarily uponthe trilobites. thick layers of stromatoliticlimestone, and, often in associationwith the sh’omatolite reefs, layers of The faunas of the Bat Cave limestones are largely coarsedetrital limestone.Many of the bedsare thin undescribed.The most conspicuouselements are the layers of lime mud, containing algal pellets and small siphuncles of endocemid and piloceroid cephalo~ds, gastropods,The Bat Caveformation contains a suc- whichare often silicified and weatherred on expos- cessionof faunas ranging in age from the Middle ures; them are abundant sponges, and a considerable Canadian(Gorman and Roubidouxequivalents) variety of gastropods,brachiopods, and trilobites. beds of Powell or possibly your~er age. At El Paso The New Mexico-succession in the Bat Cave interval the highest bedsinclude the Smithville and Black is briefly as follows:

107 NEW MEXICO GEOLOGICAL SOCIETY * FOURTH FIELD CONFERENCE* SOUTHWESTERNNEW MEXICO

1. A fauna in stromatolitic and detrital limestones Kelley and Silver(1952) divided the Montoyainto abovethe Sierrite limestone, characterized by the four formations; the Cable Canyonsandstone, the first (lowest) encloceroids, someprimitive pliomerid Uphamdolomite, the Alemanformation, and the Cutter trilobites, and abundant gastropods¯ The most common formation. The Cable Canyonsandstone, at the base, form is a small, low, broad, conical gastropodcalled ranges up to 35 feet in thickness, and contains some Rhaphistomatrochoides Meek. This fauna is present dolomite cement. T he meagrefauna so far obtained throughout in the lowest beds and is the only fauna showsnothing which has not been found in the over- which persists into the Dos Cabezasregion of Arizona. lying Uphamformation.

2. Beds with more massive algal reefs, and with The Uphamdolomite is massive with a maximum a striking fauna of large piloceroids, occasional thickness of 80 feet. It contains somechert in the coiled cephalopods, and abundant sponges, upper portion, but the fauna is not silicified, and is therefore obscure. At El Paso the lower beds have a 3. Dark weathering limestones, dark-grey to black characteristic mottled appearancenat generally found whenfresh, with abundantpebbles, largely algal pel- in the New Mexico sections. Most sections in New lets, which producea mottled weathering. In the Mexico have abundant coarse sand grains in the lower middle are several beds of black oolitic IJmestone part, and the basal beds contain reworkedmaterial containing a characteristic fauna, largely of asaphid from the underlying Cable Canyonsandstone. The trilobites and low-spired gastropods, fauna contains Maclurites, Receptaculites, Halysites, Actinoceras, and a variety of other forms. The fauna 4. Massive algal reefs with abundant sponges suggests a correlation with the late Trenton rather and otherwise a meagrefauna, but characterized by than with the Richmond. a large Orospira. The Aleman formation consists of thinner-bedded 5. Thin- beddedblue- weathering I ira,stones, with cherty dolomite, often white weathering and broken, algal fragments and hoards of small gastropods, and with an abundantfauna of silicified brachiopods. The lower layers contain abundant Dalmanella, 6. Massive beds, usually dark and with someblack Zygospira, and Cornulites, above which appears a oolite in stringers, containing the secondpiloceroid more varied fauna with Rafinesquina, Rhynchotrema fauna, cap, x, and an abundanceof arthoid and strophomenoid brachiopods. This is the fauna which has been con- 7. Thin-beddedlimestones, again with algal s idered Richmond. pellets and gastropods, but with an admixture of brachiapodsand trilobites. It is an anomalousfact that west of the Mississippi River and north from central Canadato northern Green- S. More massive beds, with a reappearanceof land~ late Ordovician strata occur with a mixture of stromatolite layers, alternating with thin-bedded Black River, Late Trenton, and Richmondtypes. Also, limestones. Characterized by an abundanceof west of the Mississippia there have been recognized echinodermfragments, and a varied fauna of small beds of late Trenton age and beds of Richmondage, brachiopodsand trilobites. Various sections through- but never beds of the intermediate Covington (Lower out southern NewMexico extend upwardto various Cincinnatian - Eden and Maysville) age. A’time break points in this column.All units are found in the is suggestedwhich if it exists lies, irritatingly, in Cooks Range. The section in the Hatchet Mountains New Mexico between the Uphamand Aleman formations, extends up to the top of bed 6. At MudSprings Moun- where no sharp contact is evident. The recent discov- tain, the uppermostbeds are in the middle of bed 5¯ ery of manysupposedly Richmondiantypes in late Trenton beds in Quebec,indicates that the faunal Montoyagroup criteria formerly used are not yet adequately knownas to range¯ Thedifficulty is largely due to the fact that The Montoyagroup is dominantly dolomites, is as from Chazyanto the Richmond, Ordovician faunas muchas 250 feet thick, and on the basis of a .promS- are madeup of complexly intertonguing faunal realms, nent fauna of silicified brachiopods,is generally perhaps geographic and climatic rather than ecological considered Richmond,latest Ordovician, in age. in the sense that this term is usually employedfor

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faunas confined to specific facies, from the ledge-forming limestones of the Mississippian above. Various formations have been recognized, and The Cutter formation consists of about 160 feet of it is knownthat together they embracea time interval generally thin-bedded, fine-grained, light-colored ranging from late Middle Devonianto the very latest dolomite, with somelayers of limestone, clay shale, Devonian. The formations are briefly summarizedas and lenses of chert. Thesebeds were originally in- follows (Stevenson, 1945). cluded with the Silurian Fusselmandolomite by Darton, but they have yielded a fauna which is clearly Canutillo formation - Recognizedonly in the late Ordovician, and probably late Richmond.The Franklin Mountains. See El Pasosection for a brief fauna contains somebrachiopods apparently similar discussion. to those of the underlying Alemanformation. In addition, it contains abundantbut poorly preserved Onateformation - 87 feet thick with the type section pelecypods (Whitella? and Ctenndonta?), gastropods, in the San AndresMountains; consists of shalee silt- and cephalopods.There are favositid corals and stone, and somefine-grained grey-brown weathering Beatricea. The fauna, as yet inadequately known, sandstones. The fauna is regarded as late Middle suggestsa possible correlation with the Whitewater- Devonian. The most characteristic forms are a Elkhorn portion of the Richmond.In somesections Leio~ynchus and Sulcoretopora anomalotruncata, the contact with the Alemanis sharp, while that and a bryozoanwith broad, flat, dichotomouslybranch- with the Fusselmancannot be determinedaccurately, ing colonies. In other sections the reverse has beenfound. Sly Gapformation - 114 feet thick; type section in Fusselmandolomite San Andres Mountains. The formation consists of thin-bedded shales, limestones, and siltstones, tan The Silurian is represented in NewMexico by the to light yellow weathering;in generalit is lighter Fusselmandolomite, a massive grey dolomite, which weathering and has less massive beds than the Onate attains a thickness of as muchas 1000feet in some formation. Thefauna, allied to that of the Hackberry places. Dolomitization is advance~producing local of Iowa, indicates an early UpperDevonian age. brecciation, and the dolomite often weatherswith mottled surfaces which, in someinstances at least, Contaderoformation - 66 feet thick, type section are shadowsof almost completely destroyed fossils, in central San Andres Mountains. Carbonaceousshales The knownfossils are those which were replaced by and thin-bedded limestones, with a basal grey lime- silica prior to dolomitization. Thefaunas are spotty stone. Except for an undescribed Ambeceellacommon geographically, and the associations vary consider- in the basal beds, the knownfauna is not different ably from place to place. The most abundantforms from that of the underlying Sly Gap. I-ithologye how- are several species and probably several genera of ever, is strikingly different. pentameroidbrachiopods, the large atremate, Monomerella,and corals including Heliolites, Favo- Perchashale - 178 feet of shale, divided into sites, and Halysites. two portions. The lower ReadyPay memberconsists of about 130 feet of calcareous shale, containing With its great thickness~it is quite possible that calcareous and often fossiliferous nodules. The Box the Fusselmandolomite represents a considerable memberconsists of blackfissileshale, but contains part of Middle Silurian time, but the isolated faunules somelayers of limestone. The calcareous content are not adequateas a basis far precise correlation, increases westwardand near Silver City one limestone and no accurate zonotion is possible. Bowsherhas mayattain a thickness of 16 feet. The knownbrachio- regarded a fauna from the SacramentoMountains as pod fauna is largely confined to the lower ReadyPay possibly Alexandrian in age. member.It is allied to the fauna of the Ouraylime- stone of Coloradoand that of the Martin limestone of Devonian Arizona.

The Devonian of NewMexico consists dominantly The distribution of the Devonianformations varies of shales, with relatively thin-bedded siltstones, widely. In the Franklin Mountainsonly the Canutillo sandstones,and limestones. As a unit, it is readily formation is recognized. The Onate, Sly Gap, and differentiated from the resistant dolomites below, and Canutiilo formations are best developedin the Sacra-

109 NEW MEXICO GEOLOGICAL SOCIETY * FOURTH FIELD CONFERENCE* SOUTHWESTERNNEW MEXICO

mento and San Andres Mountains. At Hermosathe Nunn member- Namedfrom the Nunn ranch, near On,re was found overlaid by the Perch, shale. At Lake Valley. This consists of soft, non-resistant, Percha Creek, and in the regions west and south, blue-grey marls and limestones. It contains an a- only the Percha shale has been recognized. At some bundantfauna of brachiopods, bryozoa and other forms, places its base contains a layer which has yielded and is the main source of the Lake Valley crinoids. fragmentaryfish plates and teeth. Maximumthickness is 100 feet; 50 feet at Percha Creek. The Devonian of NewMexico appears to consist of three distinct periods of deposition, one of Middle Tierra Blanca member- Grey to brown, thin-bedded Devonian(Onate) age, the second, including the Sly lime-sands, madeup largely of crinoid and bryozoan Gapand Canutillo, of early UpperDevonian, and the fragments. It grades downwardinto the Nunn member third, the Perchashale, of very late UpperDevonian. without any clear break. The upper portion becomes There has been somediscussion as to whether the cherty. A total of 40 feet measuredat Percha Creek. Perchashale is latest Devonianor earliest Mississip- Type section is along the Tierra Blanca Creek be- pian. The late Devonianage is indicated in particular tween Lake Valley and Hillsboro. This is the highest by the occurrence in NewMexico of a clymenid Mississippian which will be seen in the trip. ammonite,one of the three occurrences in North Amer- ica, the others being the upper Devonianof NewYork The Sacramento and San Andres mountains contain and the Three Forks shale of Montana. Clymenids in addition two other members,the Arcente member have served as a basis of elaborate zonation of the 230 feet thick at maximum,of calcareous siltstone UpperDevonian in Europeand North Africa, and are interbedded with soft grey shale, and the Dana Ana unknownin the Mississippian. member,175 feet at maximumof medium-to massive- bedded,grey to black, cherty, crinoidal limestone. Mississippian Uppermost Mississippian beds at Perch, Creek and Caballero formation - Strata of Kinderhookage, near Silver City have been identified by Laudonand confined to the Sacramento,San Andres, and Lake Bowsher as the Kelly limestone. These are massive, Valley regions. It is highly variable in thickness slightly crinoidal limestones containing white chert, and lithology. In the SacramentoMountains it is 60 and attaining 60 feet in thickness at North Percha feet thick and is composedof nodular limestones in Creek. The identity of these beds with the type Kelly shale. In the Lake Valley region it is thin, and con- limestone requires substantiation, and the age of the sists largely of thin, silty limestonesat the base, with type Kelly is still uncertain. somethin-bedded nodular limestone above. It is absent near Hillsboro and regions west. Middle and Upper Mississippian beds - The southern end of the SacramentoMountains and the Franklin Lake Valley formation - This has been divided Mountains contains the Middle Mississippian Las into a number of membersby Laudon and Bowsher Cruces and R ancheria formations, discussed briefly (1949), of varying lithologies and faunas, in the El Paso section. Aboveis the Upper Mississip- plan Helmsformation, a unit of Chester age. Andrecito member-Highly variable in lithology and fauna. In the Lake Valley and Perch, Creek The Mississippian sequenceof the Hatchet Moun- sections there are about 15 feet of thin, silty fossili- tains is anomalous,but contains an upper unit of ferous limestones. The maximumreported thickness definitely Chester age, closely allied faunally and of 75 feet is found in the SanAndres Mountains. lithologically to the calcareous Paradise formation Locally, thin silty bedsare replete with the trail of Arizona, rather than to the dominantly shaly Helms called Taonurus. formation of the Franklin Mountains.

Alamogordomember - Typically, the Alamogordo Mississippian rocks have generally been regarded consists of massiveblack limestones, weathering as confined to southern NewMexico. The discovery grey, with abundantlarge chert nodules; 12 feet thick by A. K. Armstrong of a Meremacfauna, closely at Percha Creek. In the SacramentoMountains, the allied to that of the Leadville limestone of Colorado, large bioherms, composedlargely of crinoidal flag- in isolated limestone remnants formerly mappedas ments, have their base in the Alamogordomember, the lower grey limestone of the Pennsylvanian Sandia

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uPPER PALEOZOIC STRATIGRAPHY OF SOUTHERNNEW MEXICO In north central NewMexico, the Pennsylvanianis roughly o North--South section N readily divisible into the upper Maderalimestone and the underlying clastic Sandiaformation. However, woR D ~~ whenthis unit is traced southward,the clastics in , \ the base of the Pennsylvaniandisappear, and the z entire sequenceis mappedas "Magdalena’, though n n r including the lateral equivalents of the Sandiabeds. =~n- LEONARD Yeso A good practical solution has beenobtained by the Abo ~..~ Gym use in mappingof lithological units. FromAlbuquerque WOLFCAMP~ -. Hueco to Socorroabove the Sandiaformation are recognized Red Tanks Bursum a lower grey limestone, and an upperclastic lime- VIRGIL stone. Still higher, is the Bursum,which is of shaly Upper clastic limestones with fusulines indicating Wolfcampage. In the Lucero uplift abovethe Sandia, are recognized ~_z MISSOUm z the Grey Mesamember, A~rasado member,and Red Grey limestone J> Tanks member.The Red Tanks is very possibly the (n>- DES MOINES MAGDALENA LIMESTONE z Bursumequivalent, but differs from it lithologically n... ATOKA and faunally. At Las Cruces, the Pennsylvanianis divisible into a lower, relatively thin-beddedunit MORROW 240 feet thick, and an upper, moremassive limestone CHESTER ~~~~ ~~~ Hde~’s~S - unit 425 feet thick. Above that is 190 feet of limestones attributed to the Bursumformation. z Leaoville rem’nontS~ ~ \ ~ ~ X~_.~-- o. MEREMAC ~ ~ ~ ~ ~ \ Las Cruces = \ \ \ ~_X~\ ~---~-.---~-~- In the Franklin Mountainsthe La Tuna, Berino, and Bishops Capmembers are recognized, but the upper ~ OSAGE part of the Pennsylvanianis not exposedin the sec- =E ~~~~~~- t ion studied by Nelson (1940). KINDERHOOK ~~~~ Pennsylvanian-Permian boundary formation, showsthat as far south as Albuquerque In northern NewMexico a logical base for the there are remnantsof Middle Mississippian, which Permianis provided by the base of the red Abo sand- elsewhere was removedby erosion, stone. However,beneath it lies the Bursumformation which, by faunal indication, is equivalent to the Pennsylvanian Huecolimestone of Wolfcampagee generally accepted as lower Permian.It is perhapsfutile to worry about The Pennsylvanian of southern NewMexico con- a systematic break betweenthe Pennsylvanian and sists of a great thickness of limestones. They are Permian~for this is a part of the world wherePenn- not easily divisible into stratigraphic units on the sylvanian-Permian deposition was essentially basis of lithology or megafossils, and as a result, continuous. As a result, an apparentparadox results. there is no general agreementas to howto treat this In NewMexico the (Pennsylvanian) Magclalena lime- part of the section. Thompson(1942) proposeda re- stone is consideredas extending up to the top of the vision basedalmost completely on the succession of last marine bed. In east-central Arizona, marine beds fusulines, but while his work was of the greatest abovethe first red bedsare consideredas part of the significance in indicating correlation with the mid- Permian. This anomalydoes not imply as serious continent divisions, it requires a knowledgeof controversy as to the age as wouldat first appear. fusulines not possessedby the averagefield geolo- As Needham(G.C. not C.C.) puts it: "When gist. The general reaction~ the wisdomof which is want to think, we scratch our heads; whenthe Chinese doubtful, has beento ignore his formation names wantsto think, he scratches his foot. Whois there completely# and to employothers, amongus who can say which produces the better result?"

111 NEW MEXICO GEOLOGICAL SOCIETY * FOURTH FIELD CONFERENCE* SOUTHWESTERNNEW MEXICO

Permian the Black Rangeand the SacramentoMountains, extends into portions of Lincoln and Otero counties. The Permianof central NewMexico consists of the shaly Bursumformation, the red sandstones, The Mogollon Plateau is almost exclusively cover- largely continental, of the Aboformation, the gypsi- ed by Tertiary intrusives and extrusives. The Basin ferous Yeso formation, and the massive San Andres and Rangesection consists of a series of tilted limestone. The Abo is considered Wolfcampin age, fault-block mountains separated from one another by the Yeso and San Andres together as equivalent to the flat-floored desert valleys called bolsons. the Leonard. But the formational boundaries are not clear time lines. The Bursumhas been found to in- The pre-Mississippian sedimentary beds thin terfinger with the lower Abe in the Sacramento depositionally and erosionally northward to the Mountains. Readhas reported a flora from the upper Mogollon Plateau on the west and to the approximate Aboindicative that in someplaces, at least, the Aba location of San Antonio (Socorro County) on the east. deposition continued on into Leonardtime. Lateral Epeirogenic downwarpingtook place to the south gradation of part of the Glorieta sandstoneinto beds during lower Paleozoic time. Mississippian sediments of Yeso lithology has been demonstrated, appearto overlap onto the margins of the erosional surface but were subsequently eroded in central New The problem becomesmore complex in southern Mexico. This late Mississippian-early Pennsylvanian NewMexico, where Bursumand Abo beds grade lat- erosion was followed by the invasion of widespread erally into lower Permianlimestones, and becomethe Pennsylvanian seas. The Wolfcamp, basal Permian, Hueco limestones in Texas. The little knownGym seemsto follow the sedimentation pattern originated limestone of southern NewMexico is apparently of in Pennsylvaniantime, with the Abo representing a lower Permianage, and its fauna indicates that it is regressive facies. A prolonged period of erosion the equivalent, at least in part, of the Huecolime- followed the deposition of the San Andres formation. stone. In the Hatchet Mountainsa thick Permian section is found, clearly extendingfarther up in the The Permian-Cretaceous unconformity is overlain section than any beds knownin the south-central in someregions by thick conglomerates. Cretaceous region, and moreclosely allied to the higher Permian seas appear to have advancedover an irregularly beds of Arizona, than to anything in the southeast developed land-mass of which local islands remained region of NewMexico. during at least a portion of Mesaverdetime.

History of petroleum exploration THE HISTORY OF PETROLEUM EXPLORATION IN SOUTHWESTERNNEW MEXICO The search for oil and gas in southwestern New Mexico began more than thirty years ago. Although by more than a hundred wells have beendrilled in this William M. Sandeen* region, the Laing No. 1 Sanchez, Socorro County, approximately eight miles southwest of Scholle, is Introduction the only one that encounteredsignificant showsof oil or gas. This test, which was completedin The southwestern one quarter of NewMexico in- January of 1952, recovered 200 MCFGPDfron~ the cludes Catron, DonaAna, Grant, Hidalgo, Luna, Pennsylvanianat a depth of 836 feet. T he offset to Sierra, and Socorrocounties, this test, the No. 2 Sanchez,reportedly shut down due to financial difficulties. This region maybe divided into three separate physiographic divisions. The Mogollon Plateau com- Although showsof oil and gas have been reported prises the northwestern portion of the region. The in the twenty-seven wells listed in the accompanying Basin and Rangeprovince includes the southern table, there is a reasonabledoubt as to the validity portion of the area, the eastern portion of whichis of manyof the shows. the southern Rio GrandeValley. This area between Approximately 35%of the wells drilled in the area ¯ Standard Oil Companyof Texas, El Paso, Texas were started in the twenties. The year 1926 was a

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