Carlsbad Gaverns, New Mexico by Douglas W. Kirkland, Mobil Research and Development Corporation, Dallas, TX. Abstract. Gypsum within the Big Room of ...
in 0riginofgypsum deposits Carlsbad NewMexico Gaverns,
surfacechannelswhere,uponcooling,gypsum precipitated. The gypsumof CarlsbadCavernsmusthave beenderivedfrom a sulfideformed by microbial reductionof a sulfate.No other mechanism is known that could reasonablyaccount byDouglas W. Kirkland, MobilResearch TX Dallas, andDevelopment Corporation, for the unusualisotopicsignatureof the mass of gypsumwithin the caverns.Microbial reacAbstract which repdata are reportedin termsof d3oS, tion leadsto enrichmentof sulfur-34in residresentsthe deviationof the S3o-td-S"ratio in Gypsum within the Big Room of Carlsbad Cavual sulfate and to depletion,commonly subparts per thousand (o/o.) from the value erns is greatly depleted in sulfur-34. This fact stantial, of sulfur-34 in diageneticsulfide precludes most previously hypothesized origins for 0.0450045,this value being the S34-to-Sil (Thodeand others, 1954;Jonesand Starkey, the gypsum and indicates that microbial agents ratio of sulfur in a standardtroilite (FeS)in 1957). played a part in its origin. The gypsum apparently iron meteoritesfrom Canyon Diablo, Ariresulted from reaction of calcium carbonate with zona; the deltaconventionindicatesthat sam- TABLE l-Suuun rsoropE VALUES FoRcypsuM sAMsulfuric acid, which may have resulted from oxidaples; sample localities are shown in fig. l. ples are enriched (positive d3oSvalues) or tion of pyrite in sandstoneand siltstone of the Yates depleted(negatived'nS values) in sulfur-34 o/o Formation (a mechanism proposed by Jagnow, d t'S o Samplenumber with respectto the standard.l 1979). An alternate explanation is that ground water 1 8 . 9 1 Upper Permian marine evaporites from bearing hydrogen sulfide moved from the Castile -15.2 Formation into the phreatic zone of the cavern westTexasand from other areasof the world 2 where the hydrogen sulfide was oxidized to yield - 18.3 have d'nSvalueswith a mode of about + I I 3 elemental sulfur; with a lowering of the ground7"" (Thode and Monster, 1965;Holser and -19.3 4 water table, the sulfur, in turn, was oxidized to Kaplan, 1966;Claypooland others,1980);the -22.0 5 sulfuric acid within the vadose zone. range for Upper Permian marine evaporites -15.0 6 worldwideis +9 7oo to + 13 o/o", n : 200 Introduction (Claypooland others,fig. 5). Thus, the sulfur Origin of gypsum The sourceof large quantitiesof gypsum isotopiccompositionof gypsumsamplesfrom within Carlsbad Caverns and within some Two hypothesized origins for the gypsum the cave are markedly impoverishedin sulothercavesof the GuadalupeMountainsis not Big Room deposits of the of CarlsbadCaverns fur-34as comparedto nearbybeddedgypsum fully understood.Various origins have been units of Permian age (Tansill, Yates,Castile, are in accord with the sulfur isotopic data proposed(Bretz, 19491'Black, 1954; Good, (table l). Both hypotheses involvereactionof and SaladoFormations). 1957;Moore, 1960;Bullington,1968;Palmer calcium carbonate with sulfuric acid. Thls A popular explanationfor the gypsumof and others, 1977; Jagnow, 1979).Measure- the cavernshas beenthat it is derivedfrom acid apparentlyresultedfrom eitheroxidation pyrite (as proposedby Jagnow, 1979)or ments of the sulfur isotopic compositionof bedded marine evaporitesnearbyby dissolu- of gypsumfrom CarlsbadCavernsindicatethat from oxidationof elementalsulfur. tion, transportation, and reprecipitation mostof thesehypothesized originsareinvalid. (Bretz, 1949;Black, The YatesFormationgradesinto and over1954;Bullington, 1968). lies the Capitan Limestonein the vicinity of The sulfur isotopicdata presentedin table I The gypsummasses preclude this possibility. The data also CarlsbadCaverns(Hayes,1964,fig.27). MiSeveralchamberswithin CarlsbadCaverns preclude crystalsof pyrite Good's (1957)proposal that warm croscopicand disseminated pyrite occur within contain gypsum; the greatestvolume occurs water within a shallow, calcium-sulfate- and large concretionsof within the Big Room. In this chamber,tabular and siltstone.Within 3 km saturatedlake enteredthe cavethrough sub- the Yatessandstone bodies of unstratified gypsum, up to l0 m of the Capitan Limestone,the siltstoneand thick, are sporadically distributed (Cood, sandstonebeds of the Yates locally contain 1957). Within the gypsum blocks, vertical numerousnodules,up to approximately5 cm tubes, some with lengthsin excessof 3.7 m in diameter,of limonite or goethitepseudoand with diametersrangingfrom 2.5 cm to 30 morphsafter pyrite (Hayes,1964,p. 35). The pyrite of the Yates, like most sedimentary cm, have formed by dripping water; some pyrite, probably resultedfrom diageneticreaclargeblockshavelost more than 5090of their bulk by this action (Bretz, 1949).Those gyptions involving sulfate-reducing bacteria; sum blocksthat remainin the room usuallylie hencethe sulfur-34concentrationof the pyrite in protectedalcovesor underoverhangingceilshould be impoverishedas comparedto Perings (Black, 1954),and locally the blocksare mian marinegypsumand shouldbe of approxI covered by flowstone and by stalagmites imately the samemagnitudeas the sulfur-34 I (Bretz,1949;Good, 1957). ( concentrationof the gypsumdepositof CarlsThe gypsum massesof Carlsbad Caverns bad Caverns(table l). Oxidationof the pyrite are thoughtby Palmerand others(1977)to be would generatesulfuric acid (Lindgren, 1933, direct replacementof limestone-the Capitan p. 60 and p. 829)and, subsequently, reaction Limestoneof LatePermian(Guadalupian)age of the acid with the CapitanLimestonewould -with someblocksof gypsumdisplayingpetresult in gypsum,someof which might have rographicfeaturesof the carbonatessuch as accumulatedwithin CarlsbadCaverns.A simpisolites,fossils,breccias,and primary pores. ilar origin has beenproposedfor sulfate minJagnow(1979,p. 45), on the other hand, reerals within cavesof central Kentucky (Pohl .aA ports that the gypsumaccumulatedduring a and white, 1965). period of thousandsof yearsby precipitation Another origin for sulfuric acid is oxidation and sedimentation within pondedwaters. of elementalsulfur, a reaction that may have played a part in the formation of the gypsum Sulfur isotopicdata depositsof CarlsbadCaverns. Six samplesof gypsumwereobtained(with In Late Tertiary and Holocenetimes,a mipermission)from the Big Room (fig. l). The crobially aided reaction between hydrocarsampleshave an averaged"S value of -18.1 FIGURE l-SnNlpr-e LocALtrrESln Brc Roov or bons and calcium sulfate resulted in the partsper thousand( o/oo) and a rangeof - I 5.0 generation of great quantities of hydrogen Cnnlssnp CnvEnx$ dashedline is trail (after map o/ooto -22.0 "/"" (table l.) [Sulfur isotopic byJagnow,1979). sulfide within ground waters of the Castile May 1982
New Mexico Geology
Formation (Davis and Kirkland, 1970; Hinds and Cunningham, 1970; Smith, 1978, 1980)' Hydrogen-sulfide-rich ground waters may have moved through breccia zones within the Castile (Anderson and others, 1972; Anderson and others, 1978), through fractures, and through solution channels for distances of several kilometers or more into the Capitan Limestone, a major aquifer (Motts, 1968; Hiss, 1975), and hence into a cavern system of which the early Carlsbad Caverns were a part. Oxidation of hydrogen sulfide within the phreatic zone of the caverns would result in precipitation of sulfur and in accumulation of sulfur within the cave. With a decrease in elevation of the ground-water table, the accumulation of sulfur would be exposed to moist, oxidizing conditions. Oxygen, sulfur, and vadose water, aided by the bacterium Thiobacillus sp., would react to form sulfuric acid. Transported into the phreatic zone by descendingvadose waters, this acid would diffuse and would react with the limestone wall rock to form gypsum. Becauseof their elevation and their distance from the reef front, movement of hydrogensulfide-bearing waters into other caves of the Guadalupe Mountains in which gypsum has accumulated may be hydrodynamically improbable. If so, Jagnow's (1979) explanation for the gypsum deposits of Carlsbad Caverns should receive additional support. Conceivably, pyrite within sandstone and siltstone of the Yates originated during the hypothesized influx of hydrogen-sulfide-bearing waters from the Castile into the cavern systemsof the Guadalupe Mountains. If this were true, the diagenetic age of the pyrite, which is unestablished. would be late.
Holser, W. T., and Kaplan, I. R , 1966, Isotope geochemistry of sedimentary sulfates: Chemical Geology, v' I' p'
93-r35 Jagnow, D. H., 1979, Cavern development in the Guadalupe Mountains: Albuquerque, Adobe Press (publication of Cave ResearchFoundation), 55 P Jones, G. 8., and Starkey, R. L., 1957, Fractionation of stable isotopes of sulfur by microorganisms and their role in deposition of native sulfur: Applied Microbiolo g y , v . 5 , p .l l l - l l 8 Lindgren, Waldemar, 1933, Mineral deposits: New York, McGraw-Hill Book ComPanY, 930 P. Moore, G. W., 1960, Geology of Carlsbad Caverns, New Mexico: National Speleological Society, Guidebook for the 1960Convention, p. l0-17 Motts. W S., 1968, The control of ground-water occurrence by lithofacies in the Guadalupian reef complex near Carlsbad, New Mexico: Geological Society of America, B u l l . ,v . 7 0 , p . 1 , 7 3 7 Palmer. A. N., Palmer, M. V., and Queen, J Nd'' 1977' Speleogenesisin the Guadalupe Mountains, New Mexico -gypsum replacement of carbonate by brine mixing: Shelfield, International SpeleologicalCongress, Proc., p' 333-336 Pohl. E. R.. and White, W B., 1965, Sulfate mineralstheir origin in the central Kentucky karst: American M i n e r a l o g i s t ,v . 5 0 , n o . 9 , p . 1 , 4 6 1 - l , 4 6 5 Smith. A. R., 1978, Sulfur deposits in Ochoan rocks of southeastern New Mexico and west Texas: New Mexico Bureau of Mines and Mineral Resources, Circ 159' p' 7t-77
.-,
1980, Sulfur deposits in Ochoan rocks of the Gypsum Plain, southeastern New Mexico and west Texas: New Mexico Geological Society, Guidebook 3lst field conference, P 271-283 Thode, H. G., Wanless, R. K., and Wallouch, R ' 1954' The origin of native sulfur deposits from fractionation studies: Geochimica et Cosmochimica Acta, v. 5' p. 286298 Thode, H. G., and Monster, Jan, 1965, Sulfur-isotope geochemistry of petroleum, evaporites, and ancient seas: American Association of Petroleum Geologists, Mem' 4,
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copper NewbookonPorPhYrY deposits Published The University of Arizona Press recently announcedpublication of a 580-pagebook Advances in geology oJ the porphyry copper deposits-soulh' westernNorth America, editedby SpencerR' Titley. The cloth-boundbook, which sellsfor $35.fi)' presents findings of lecent geologic studies.Part one of ore genof manyaspects containsinterpretations esisbasedon field and laboratory studiesin accordmadefrom 1960to 1980'while ancewith advances part two describesspecificdepositsin detail. The book is available from the University of Arizona Press,Box 3698,Tucson,AZ 85722.
References D. W , and R. Y., Dean,W. E., Kirkland, Anderson, Snider. H. I., 1972, Permian Castile varved evaporite sequence, west Texas and New Mexico: Geological Society ofAmerica, Bull., v.83, P 59-86 A n d e r s o n . R . Y . , K i e t z k e , K . K . , a n d R h o d e s ,D . J , 1 9 1 8 ' Development of dissolution breccias, northern Delaware Basin, New Mexico and Texas: New Mexico Bureau of Mines and Mineral Resources,Cir c. 159, p. 47- 52 Black, T H., 1954, The origin and development of the Carlsbad Caverns: New Mexico Geological Society, Guidebook 5th field conference, p. 136-142 Bretz, J. H., 1949, Carlsbad Caverns and other cavesof the Guadalupe Block, New Mexico: Journal of Geology, v 57 , p. 441 -463 Bullington, N R., I968, Geology of the Carlsbad Caverns, irl Delaware Basin exploration: West Texas Geological Society, Guidebook, p 20-23 Claypool, G. E'., Holser, W. T , Kaplan, I. R., Sakai, Hitoshi, and Zak, Israel, 1980, The age curves of sulfur and oxygen isotopes in marine sulfate and their mutual interpretation: Chemical Geology, v 28, p. t99-260 Davis, J. B and Kirkland, D. W , l9?0, Native sulfur deposition in the Castile Formation, Culberson County, Texas: Economic Geology, v. 65, p 107-l2l Good, J. M., 195?, Noncarbonate deposits of Carlsbad Caverns: National Speleological Society, Bull., v. 19, p.
|-23 Hayes,P. T., 1964,Geologyof the GuadalupeMountains, New Mexico:U.S. GeologicalSurvey,Prof. Paper446, 69 p. Hinds, J. S., and Cunningham,R. R., 1970,Elemental sulfur in Eddy County, New Mexico: U.S' Geological S u r v e yC, i r c . 6 2 8 l,3 p . hydrolHiss, W. L , 1975,Stratigraphyand ground-water New Mexico ogy of the Capitan aquifer, southeastern and westernTexas:Ph.D thesis,Universityof Colorado (Boulder),396p.
Phoro by Glenn R, Osbun
Socorro Peak, a well known landmark in central New Mexico, is complex and interesting geologically. The mountain block is uplifted along normal faults that separatethe low piedmont surfacesin the foreground from the steep slopes of the mountain. The most prominent features on the mountain are Miocene-age rhyolite domes and flows that cap "M" Mountain and the northern ridge ending in steep cliffs, and form Strawberry Peak (the pointed hill at the right edge of the photograph). Also prominent are very well indurated Miocene alluvial fan and mudflow deposits that form the large vertically striated cliffs just below the "M." Pennsylvanian sedimentaryrocks of the Sandia and Madera Formations crop out further down the slope around the prominent white area. Note the well-bedded nature of theseoutcrops. These sedimentary rocks are truncated on the south by the northeast topographic margin of the Oligocene-ageSocorro cauldron (an ash-flow cauldron similar to the young Valles cauldron in northern New Mexico). This topographic margin lies approximately in the gully that trends
diagonally 45 degreesdownward to the left from the "M." Cauldron topographic margins often form very large and abrupt erosional unconformities. South of this unconformity, the cauldron-related rocks are thought to be more than 6,000 ft thick' whereas they are only 800 ft thick above the Paleozoic rocks on Socorro Peak. Here, these rocks form the gentle slope and lower cliff between the bedded Paleozoic rocks and the big cliffs of well-indurated fanglomerates.The cauldron-related rocks pinch out within a short distance to the north. A detailed description of the volcanic geology of the Socorro Peak area has been presentedby R. M. Chamberlin in New Mexico Bureau of Mines and Mineral Resources Open-file Rept. ll8 and in New Mexico C e o l o g y , M a y 1 9 8 1 ,v . 3 , n o . 2 . S e v e r a lm i n e s p r o duced silver from veins in a fault block of Miocene rhyolitic rocks during the late 1800's. These mines were located in the small dark rounded hill above and to the left of the large white water tank. -Glenn R. Osburn
AN INVITATION TO OUR READERS descriptionabove,we woutd like to invite our readersto submittheir With the photo and accompanying own work ro the Gsllery of Ctology, excellint quality black-and-whitephotographsof a geologicfeatureor geololic description(l-1Vz pagesin length)shouldbe submittedto Marla D. areaand an accompanying Adkins-Heljeson,Editor, iew tlexico Giology, New Mexico Bureau of Mines and Mineral Resources, Socorro.NM E7E0l.We look forward to seeinga wide selectionof photographsof New Mexico'sscenic geology.
New Mexico GeologY
May 1982
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