Stratigraphicnomenclature ol proterozoic rocks, northern NewMexico-revisions, redefinitions, andformalization byPaul W' Bauer, New MexicoBureau ol Minesancl Mineral Resources, Socono, NM 87801 , and Michaet L. Wiltiams,Department of Geology and Geography, Universityof Massachusetts, Amherst, MA 01003

Abstract lithotectonic nomenclature for the supra- Much of the exposed Proterozoic rock in crustal Precambrianrocks exposed in north- This paper proposes formal northern New Mexico can be assignedto one revisions of ern New Mexico. the lithostratigraphicnomenclature for some of four major lithologic assemblages:1) se- Early Proterozoic rocks in northern New quencesdominated by metamorphosedmafic volcanicrocks, ca 1,755-I,720 Ma in age;2) sequencesdominated by metamorphosed felsic volcanic rocks and immature clastic sedimentaryrocks, ca 1,700Ma and ca 1,500- tains, the Truchas Peaksarea, the Rio Mora- 1,650Ma in age;3)massive clean quartzite(s) and sequencesof interlayered pelitic schist and quartzite, 1,700-1,650Ma; and 4) intru- sive rocks that range widely in age and com- position (Robertsonet al., in press).Each of these is discussed separately.Table L sum- marizes both existing and proposed new no- Kiowa Mountain in the Tusas Mountains. menclature for stratified units. Several distinctive units are designated as of northern and central New Mexico, and formations: Big Rock Formation, Burned perhaps in parts of Arizona and southern Mafic metavolcanic sequences Mountain Formation, Marquenas Forma- Colorado (Burns and Wobus, 1.983;Wobus, tion, Clenwoody Formation. Extensive terrains dominated by amphi- The metase- 1985;Bauer and Williams, 1985;Grambling dimentary sequencepreviously bolite and mafic schist of igneous parenfage called the and Williams, 1985;Williams, Ortega Group is,renamedthe Hondo 1987). and immature metasediments Group, In have been and a principal referencesection is pro- the following sections,changes in no- posed in the Hondo Canyon area of'the menclature are proposed for many of the ma- northern PicurisMountains. Formations in jor and minor lithotectonic assemblages the unit include the Ortega Formation, Rin- currently recognized in northern New Mex- Alsoin thisissue conada Formation, Pilar Formation, and Piedra Lumbre Formation. The name Em- NMGS1990 fallfield budo Granite is abandoned in the picuris conference p.52 Mountains but provisionally retained in the Geologybeneath and around SantaFe Range.Nomenclaiure for all other plutonic rocks is provisionally retained the WestPotrilb names and rankings has not been changed pgndjlg further research.These proposals basalts p. 53 should provide a foundation for the devel- dramatically.Wher"e the nomenclatureis'un- opment of a consistent,coherent, inte- changed or-where proposed changesare mi- NMGS1989 spring meeting grated nomenclature for the Precambrian nor, appropriate referencesare given in lieu abstracts p. 59 rocks of New Mexico. of details of unit descriptions.All proposed NMGS1989 fallfield changes conform to the guidelines outlined by the North American conference p. 60 Introduction Commission on Galleryof geology-Navajo The stratigraphic nomenclature proter- of p. ozoiq rocks in northern New Mexico has de- Church 69 veloped gradually over the past fifty years. Donationsto NMBMMRand Consequently, the literature ii burderiei with Museum p.62 conflicting_and obsolete stratigraphic names, Service/News p. most of which do not conform io the pub- 66 lished rules of the North American iom- Upcomingmeetings p. 67 Staffnotes p. 68 Gomingsoon Oil andgas discovery wells drilled in NewMexico in 1988 northern New Mexico now make well-con- sistentyet flexiblenomenclature that canserve SugariteCanyon State Park strained regional correlations possible. The as a common basisfor further discussionand purpose of this paper is to propose a unified analysis. FentonHill granodiorite identified in several uplifts in northern New Iiminary U-Pb zircon isotopic age Moppin Complex (formerly Moppin Mexico (Fig. 1). The three best-documented determinations suggestthat although the in- Metavolcanics)-Tusas Mountains terrains are the Moppin Metavolcanicsof the dividual sequencesmay be as old as 1,765 The mafic metavolcanic sequence of the northern Tusas Mountains (Barker, 1958; Ma, all are older than about 1,710Ma (Wil- northern Tusas Mountains was named the Wobus, 1985), the Pecos greenstone belt of liams, 1982).We suggestthat they informally Moppin metavolcanicseries by Barker (1958) the Santa Fe Range (Robertsonand Moench, be designated mafic metavolcanic se- and renamed the Moppin Metavolcanicsby L979;Robertson and Condie, 1989),and a quences. Wobus (1985).The geographicname Moppin + sequence of layered amphibolite biotite Major- and trace-elementanalyses of the is appropriate for this successionof rocks gneiss in the Taos Range (Condie and Moppin sequence(Barkerand Friedman, 1974; and need not be changed. However, series McCrink, 1982;Reed, 1984; Lipmanand Reed, Binglea 1974;Boadi, 1986;Smith, 1986;Ga- designation (chronostratigraphic category) 1989)south of Questa.An assemblageof am- belman, 1988), the Pecos greenstone belt is inappropriate and Metavolcanicsdoes not phibolite and schist in the southern Picuris (Robertson and Moench, 1979;Klich, 1983; accurately reflect the diverse volcanic, vol- Mountains may represent a similar lithotec- Robertsonand Condie, 1989),and mafic rocks caniclastic,and epiclasticlithologies present. tonic sequence(Bauer, 1988).Each of these of the TaosRange (Condie and McCrink, 1982) Although this unit does contain local se- mafic-dominatedsequences is associatedwith suggestthat these mafic suites are geochem- quences of rock with distinctive character- a diverse suite of metaplutonic rocks. In all ically similar to modern tholeiitic and/or calc- istics that are individually mappable, these uplifts, the mafic-dominated rocks are inter- alkaline rocks found in arc or back-arc vol- sequencesare not regionally correlable. In preted to be the oldest exposed units. Pre- canicassemblages. addition, the unit is metamorphosed and multiply deformed and contains intrusive TABLE l-Stratigraphic nomenclature of supracrustal Proterozoicrocks in northem New Mexico. rocks. We therefore suggest the lithodemic rank of complex for the Moppin. Stratotype or Previous The Moppin Complex is exposed in the Proposed nomenclature reference section(s) nomenclature Age (Ma) northern Tusas Mountains in a northwest- trending belt extending from American Creek HONDO GROUP Picuris Mtns Ortega Group Younger than (southwestem Mule Canyon 7tlz-min quad- Hondo Canyon (Long, 1976) 7,700 rangle, T28N, R8E) to Hopewell Lake and Placer Creek (northeasternEast Gavilan Piedra Lumbre Formation Picuris Mtns Piedra Lumbre Formation Hondo Canyon (Long,1976) Canyon 7rlz-min quadrangle, T29N, R6E), and along the easternside of |awbone Mountain. Pilar Formation Picuris Mtns Pilar Formation Its exposed primary thickness, though dif- Hondo Canyon (Long, 1976) ficult to determine due to structural com- plexities, is probably at least several thousand Rinconada Formation Picuris Mtns RinconadaFormation feet (Barker, 1958). Hondo Canyon (Nielsen, 1972) The Moppin Complex is dominated by chlorite schist and./oramphibolite with lesser Ortega Formation Picuris Mtns Ortega Quartzite 1) Hondo Canyon (Nielsen, 1972) 2) Pilar cliffs 3) Copper Hill AAexfic@ TusasMtns New 1) Ortega Mtns 2) fawbone Syndine GEOLOGY o $Gienceand Senice Volume 11, No. 3, August 1989 VADITO GROUP Tusas Mtns Vadito Group ca 1,700 Mesa la Jarita (Williams et al., 1986) Etlitor: Ctol A. Hjellming Dralting resistance: Rebecca Titus, Michael Wmldridge Published ouatslv bv Big Rock Formation TusasMtns Big Rock Conglomerate New Mexico Breau of Mins and Mineml Remrc Mesa la Jarita (Barkea 1958) a divisin of New Mqb InstitrrF of Mining & Tedrndog1f BOARD OF REGENTS Bumed Mtn Formation TusasMtns Bumed Mtn Metarhyolite Ex Officio Burned Mtn (Barker, Garey Caruthers, Cwmr ol Nru Mtxia 1958) Alan Morgan, Superintendentol Pilblic Instruction Appointed Marquenas Formation Picuris Mtns Marquenas Quartzite Lenton Malry, Pr6., lq!5-1991, Abuqwqre Cerro de los (Long,1976) Robert O. Andemn, tu.|Irrc., 187-1993, Rwll Lt. Gen. Leo Marquez,7989-7995,Albuquaqw Marquenas Carcl A. Rymer. M.D. 1989-195, Albuqwqw Steve Torcs, 1967-1991, Albuqunqw Glenwoody Formation Picuris Mtns Felsicschist at Pilar New Mexico lnstitute of Mining & Tchnology Pilar cli-ffs (Bauer, Pr6illent-...... laurcneH.lattman 1988) New Msico B@au of Min6 & Minsal Rsm Dir6tu ...... FrankE.Kotdowski As#inte Dirttor . . . Jam6 M. Robqtrcir MAFrC METAVOLCANTC SEQUENCES Sufuriptims: Issued quarterly, Febmry, May, August, Novembe4 subscription prie 96.00elendar year. PECOS COMPLEX Pecosgreenstone belt ca L,720 Aittrial Mttd: Arlicle submitted for publietion should be in the edito/s hands a minimm of five (5) months (Robertsonand Moench, before date of publi@tion (Februry, May, AuSust, or 1979) November) and should be no longer than m tyFuit- ten, doublespaced pat6. All rientific papen will be GOLD HILL COMPLEX Taos Range reviewed by at least two p@ple in the apprcpriate field Unnamed ca 1,765 of study. Address inquirie to Carcl A. Hiellming, Editor Gold Hill (Reed, 19&t) ot Nru Mcxio Gedogy,New Mqico Breau of Mine & Mnenl Rercrc, Srcrc, NM E7801 MOPPIN COMPLEX TusasMtns Moppin Metavolcanics older than Publishd re pulnic dmin, thnelue reprdrcible uirrou, per- 1) Brazos Box (Wobus, 1985) t,755 nission. fuure dedit reCwld. 2) Iron Mtn Cirahtim:7,ffi 3) Cleveland Gulch Prif,rt; Univsity of New Mexio Printint Plant

August 1989 Nan Mextco Geology components of feldspathic schist and gneiss, longer conform entirely to the Law of Su- terpreted for the Pecos Complex based on muscovite ( + biotite) schist, metaconglom- perposition. It is, therefore, best categorized U-Pb zircon dating of metavolcanic rocks and erate, and banded iron formation. Locally as a lithodemic unit rather than a lithostra- subvolcanic intrusive rocks (Bowring and exposed primary volcanic and sedimentary tigraphic unit. Becausethis terrain consists Condie, 1982;Robertson and Condie, 1989) structures include pillows, graded beds, and of two or more genetic classesof rocks (vol- and on model lead ages of galenasfrom ge- relict phenocrysts. The Moppin Complex is canic, plutonic, sedimentary), it is proposed netically related volcanogenic massive sul- associatedwith (intruded by?) several gran- that the rank be designatedas complex, thus fide deposits(Stacy et al.,1976). odiorite bodies collectively called the Ma- Pecos Complex. At some future time, as quinita Granodiorite (Barker, 1.958;Barker and mappingpermits, this complex could be sub- Gold Hill Complex-Taos Range Friedman, t974; Wobus and Manley, 1982a) divided into supersuites and suites. A mafic/felsic layered gneiss successionin and with a 50+ km' (20+ mi'?)pluton of The PecosComplex occupies approxi- the TaosRange south of Questa (Condie and trondhjemite/granite informally called the mately 550 km'(250 mi'?)in the headwaters McCrink, 1982;Reed, 1984; Lipmanand Reed, trondhjemite of Rio Brazos (Barker et al., of the Pecos River, northeast of Santa Fe. 1989) has not previously been named for- trondhjemite has an Rb-Sr whole- Robertson and Condie (1989)and Robertson 1974).The '1.,654+34 mally. As in the PecosComplex, these rocks rock isotopic age of Ma recalcu- and Moench (1979)distinguish four assem- contain a significant intrusive comPonent, are lated from Barker et al. (1974)using the decay blages of Precambrianrock types within the metamorphosed and multiply deformed, and constant of Steiger and Jager (7977). Al- complex: 1) metavolcanic rocks with minor may be categorized best as a comPlex. We though contactsbetween mafic supracrustal interbedded volcaniclasticrocks and iron for- propose the name Gold Hill Complex after rocks and most metaplutonic rocks are in- mation; 2) metasedimentary rocks including ixposures at Gold Hill, 7 km (4 mi) north of tensely deformed, trondhiemite aPPearsto feldspathic sandstone, shale, volcaniclastic T*ining, New Mexico (southwestern Red intrude the Moppin Complex in the Rio Bra- graywacke, carbonate, and distal iron for- River 7rlz-min quadrangle). zos gorge area (Gabelman, 1988).Although mation; 3) intrusive felsic and mafic rocks of Reed (1984)described a layered gneiss se- rocks of the Moppin Complex have not been a subvolcanic complex; and 4) younger gra- quencein the Gold Hill areaas consistingof dated directly, Barker (1958)and Wobus and nitic rocks.An age of 1,720Ma has been in- cbmplexly interlayered feldspathic gneiss, Hedge (1982) concluded that the Moppin Complex was intruded by the Maquinita Granodiorite (dated at L,755Ma by U-Pb zir- conmethodbyL. T. Silver,pers. comm. 1987). If the contact is not intrusive, then the Mop- q pin Complex could be considerablyyounger. - Due to the lithologically complex nature of ,{ the Moppin Complex, we propose three dif- t ferent exposures as reference sections. Ex- a\ cellent exposures on Iron Mountain (informal \ name), southwest of fawbone Mountain quadrangle, sec. (Bumed Mountain 7llz-min Cimarron 30, T29N, R7E), are distinctive due to su- Range perbly preserved primary sedimentary and volcanic structures and to the occurrenceof banded iron formation (Smith, 1986).The second referencesection is in the BrazosBox area of the Rio Brazos(southwestern Lagun- itas Creek 7tlz-min quadrangle, T29N, R5- 6E). Relict volcanic textures and structures a PryJ "----{ A Ao occur in the northern (lower?)portion of this PRECAMBRIANROCKS ({II .? thick (apparently up to 10,000ft) exposure PLUTONICROCKS 7 r-A\> o'c (Gabelman, 1988). Middle-Early Proterozoic %il of the Moppin Complex (<17OOMa) -"'g- p ' Although outcrop is more or lesscontinuous u/\' in this area, Moppin Complex rocks are highly Early Proterozoic TruchasPeaks Riot tectonized and primary thicknessesand (>16O0 Ma) area MOra stratigraphic relationships are complicated 1*--1 Early Proterozoic \/l_(17211-1160 Ma)_ Qtu by folding. The third referencesection is in li _ _ SUPRACRUSTALROCKS Cleveland Gulch, south of Tusas Mountain li.fiil 9611onCanvon succession (southeastern Burned Mountain 7llz-min [i;:-:''::l and simitai rocks in N. SantaFe Ranqe & quadrangle, T28N, R7-8E). In this area, ex- t:.Et Hondo posures of Moppin Complex consistof chlor- l1_l Group rI ite-hornblende phyllite, schist, and gneiss, PECOSCOMPLEX plus subordinate hornblendite, metapelite, Vadito Group o mafic breccia, hematite-quartz iron forma- U) Santa tion, and magnetitequartz ironstone (Kent, Undivided Fe' 1980). @ Maf ic-dominated sequences PecosComplex (formerly Pecos melavolcanrc greenstone belt)-Santa Fe Range Dalton Canyon Robertson and Moench (1979)named this succession package of rocks after the nearby town of Pecos.The area of outcrop contains a signif- icant amount (approximately 507o)of intru- sive rock, is metamorphosed, multiply FIGURE l-Generalized map showing the distribution of Precambrian rocks in north-central New deformed, and poorly exposed, and may no Mexico. Modified from unpublished maps by I. M. Robertson and f. A' Grambling.

Nar Mexicn Geology Angust 1989 biotite-homblende gneiss,homblende gneiss, in the Picuris Mountains is dominated by tic sediments. Rocksinterpreted to belong to and amphibolite. He interpreted this se- large amphibolitebodies that host horizons the Vadito Group havebeen identified in most quence as metamorphosed volcaniclasticrocks of quartz-muscovite-biotite schist, cross- of the major Precambrian-cored uplifts in interlayered with flows, tuffs, and sedimen- bedded impure quartzite, and metaconglom- northern New Mexico. In addition to the ref- tary rocks. Geologic relationships within the erate. Although relative proportions differ, erence section in the cenhal Tusas Moun- layeredgneiss sequence, and betweenit and all of these rock types can also be found in tains, Vadito Group rocks are exposed adjacentfelsic volcaniclastic rocks to the north, the Vadito Group reference section of the throughout the eastern half of La Madera are unknown. Preliminary U-Pb zircon data TusasMountains. At least some of the am- quadrangle (Bingler, 1974), east of Ojo Ca- from a felsic metatuff near Gold Hill have phibolites are intruded by granitic plutons. liente in the Ojo Caliente quadrangle (Trei- yielded an isotopic age of 1,755Ma (S. A. Such intrusive relationships, however, are tnan, t977; Williams, 1987), and in the Bowring, pers. comm. 1986). not found elsewhere in the Vadito Group. It northern part of Cafron Plaza quadrangle is possible that bedding-parallel shear zones (Barker and Friedman, 1974; WiIliams, 1987). Vadito Group (Bauer, 1988) and/or unconformities (Bell, In the Picuris Mountains, Vadito Group units The names Vadito group and Vadito for- 1985)may exist within the original type sec- crop out along the southem flank of the range mation have been used in various ways in tion, such that some of these amphibolites (Montgomery, L953; Long, 1974; McCarty, New Mexicoduring the past 30years. Mont- may be related to the older mafic-dominated 1983;Bauer, 1988)and in the cliffs near Pilar gomery (1953)originally proposed the name metavolcanic sequences,rather than to the in the northwestern part of the range (Gre- Vadito formation for a sequenceof mafic and Vadito Group proper. sensand Stensrud,1974;Bauer,1988). Vadito felsic metavolcanicrocks in the southern Pi- The northern part of the Vadito Group in Group rocks have been found in the Truchas curis Mountains.Long (1976)suggested rais- the southwestern Picuris Mountains consists Range and Rio Mora area (Grambling, 1979; ing its status to Vadito group. This sequence of quartz-muscovite-biotite schists, meta- Grambling and Codding, 1982),in the Rin- has been correlated with various metavol- conglomeratesand impure quartzites of the con Mountains and northern Taos Range at canic and metasedimentary rocks in other Marquenas Formation, and subordinate Cedro Canyon (Gramblinget al., 1989),and uplifts (Robertsonand Moench, 1979).Both feldspathic schists, calc-silicates,aluminous in the northern TaosRange near Costilla Res- felsic and mafic metavolcanicsequences have schists, and mafic schists and amphibolites. ervoir (J. A. Grambling, pers. comm. 1989) been included previously within the general To the east, the Vadito Group also contains and along Costilla Creek (J. C. Reed,Jr., pers. group name (Soegaardand Eriksson, 1986). locallyabundant feldspathic quartz-eye schists comm. 1989).Although Vadito Group rocks Williams et al. (1986)informally proposed interpreted as metarhyolites (Bauer, 1988). have not yet been recognized in the Santa that the name Vadito Group be applied to a All of these rock types are characteristic of Fe Range, Cimarron Mountains, or southern sequence of immature quartzofeldspathic the Vadito Group in the Tusas Mountains Taos Range (J. A. Grambling, pers. comm. metasediments and dominantly felsic meta- and elsewhere. However, what the original 1989),similar rock types have beenreported volcanicrocks that stratigraphiiallyunderlie type locality in the southern Picuris Moun- in the Cimarron Mountains (Wobus,1989). (Holcombeand Callender,7982) the Ortega tains appears to lack is the voluminous feld- The most distinctive component of the Formationin a number of placesin northein spathic schist (metarhyolite) commonly found Vadito Group is quartz-muscovite-feldspar New Mexico. These rocks are lithologically, elsewhereat the top of the Vadito Group just schist containing quartz megacrysts, inter- geochemicallt and tectonically distinct from below the contact with the Ortega Forma- preted to be phenocrystic felsic metatuff. the older (7,765-I,720Ma) mafic metavol- tion. In the southern Picuris Mountains, a These schists are interlayered with massive canic sequencesand can be correlatedamong north-verging ductile fault separatesVadito metarhyolite, vitreous quartzite, muscovitic isolated mountain ranges over much of Group from the younger Hondo Group rocks quartzite, meta-arkose, biotite-muscovite northem New Mexico. We propose that the (Holcombe and Callender, 1,982;McCarty, schist, pelitic schist, amphibolite, and chlor- name Vadito Group be formally adopted un- 1983;Holcombe et al., 1985;Bauer, 1988). ite schist. Mafic lithologies make up only a der the definition of Williams et al. (1985). This fault has removed an unknown amount small part (generallyless than 10%) of the Although applying the name Vadito to this of the upper part of the Vadito Group and Vadito Group. Textural and cornpositional more broadly exposed packageof rocks is in iuxtaposed an inverted Vadito Group against heterogeneity, characteristic of the Vadito some ways unsatisfactory,as discussedbe- an upright Hondo Group. Possibly,the thick Group at all scales,results from a combina- low, the name is ingrained in the literature section of feldspathic schist below the Or- tion of primary lithologic variation, local pre- to the extent that, in our iudgement, any tega Formation in the cliffs near Pilar is metamorphic hydrothermal alteration, and redefinition would only furtheiconfuse th'e equivalent to part of the missing uppermost the effects of metamorphism and deforma- nomenclature. Vadito Group in the southern Picuris Moun- tion. Metavolcanic rocks from several local- Although the Vadito Formation (and sub- tains type locality (Bauea 1988). ities within the Vadito Group have yielded sequently, Group) was originally described Until more is known about the southern U-Pb zircon isotopic ages of approximately in the southwestern Picuris Mountains Picuris Mountains section, we recommend 1,700Ma (L. T. Silver,pers. comm. L984). (Montgomery, 1953)and that place therefore continued application of the Vadito Group Although it is not currently feasibleto sub- remains the original type locality, we believe name for all of the supracrustal rocks ex- divide all of the Vadito Group, several units that the southern Picuris Mountains is not posed in the southernmost Picuris Moun- are sufficiently distinctive and/or Iaterally the best placeto characterizethis newly de- tains. continuous to be formally designatedas for- fined, complexsection of regionallyexposed Becausestratigraphic relationships within mations. These include the Big Rock and rock. Older mafic metavolcanicrocks inother the redefined Vadito Group and between the Burned Mountain Formations in the Tusas areas have been included within the Vadito redefined Vadito Group and younger rocks Mountains, and the Marquenas and Glen- Group partly becausethe type locality near are clearly exposed and most easily accessi- woody Formations in the Picuris Mountains. the Harding mine in the southwestern Pi- ble in the TusasMountains (Williams, 1987), curis Mountains contains abundant amphi- we propose that a Vadito Group principal bolites. Although the Vadito Group of-the referencesection be designatedin the central Vadito Group principal reference section southern Picuris Mountains (as desciibed by TusasMountains, south of Kiowa Mountain near Kiowa Mountain "1975) Long, differs in significant ways from between Mesa de la Jaritaand TusasBox (Las The Vadito Group in the central Tusas the proposed Vadito Group of the Tusas Tablas71lz-min quadrangle, all sections, T27N, Mountains is dominated by felsic metavol- Mountains and elsewhere, most of the dif- R8E). canic rocks and feldspathic metasediments. ferences can be attributed to a combination The Vadito Group, as defined herein, is a The most characteristic rocks are quartz- of original stratigraphic variation and su- regionally extensive sequenceof supracrus- muscovite-feldspar schists, which contain perimposed structural complexities. tal rocks dominated by feldspathic schist, Iarge (to severalmm in diameter) quartz and The southemmost part of the Vadito Group feldspathic gneiss,and metamorphosedclas- feldspar crystals interpreted as relict phe-

August 1989 Nm Mexico Geology nocrysts. These rocks range from highly mation for the composite package,and sug- northern and southeastem Picuris Moun- schistoseto massiveboth along and across gest a stratotype in the Las Tablas 7llz-min tains, the Rincon Mountains, and the Rio strike, and are interlayered with amphibol- quadrangle(secs. 22 and29,T27N, R8E). The Mora area. All of these sections contain ap- ite, crossbedded muscovitic quartzite, feld- Big Rock Formation is the principal marker preciable thicknesses of well-layered, quartz- spathic quartzite, biotite-muscovite schist, unit within the Vadito Group reference sec- muscovite-feldspar schists with megacrysts conglomerate,and pelitic schist (Gresensand tion south of Kiowa Mountain (Barker, L958; of quartz. Stensrud, 1974;r{obus and Manley, 1982b; Wobus, 1985;Williams, 7987)and has been Williams, 1987). traced along strike for more than 10 km (6 (formerly The Vadito Group-.Hondo Group contact mi). Metaconglomeratelayers are character- Marquenas Formation at Kiowa Mountain (originally spelledKiawa, ized by elongate cobbles, 1 to 20 cm in di- Marquenas Quartzite)-Picuris Mountains but changed to Kiowa by the Forest Service ameter, of vein quartz, quartzite, schist, and The Marquenas Formation of the southem in 1960's,according to F.Barker, pers. comm. metarhyolite in a matrix of quartz-muscovite Picuris Mountains was originally called the 1989)is distinctive in that it may have been schist or quartzite. Locally, a thin impure conglomerate member of the Vadito forma- only minimally affected by the regional de- quartzite is present below the main meta- tion by Montgomery (1953).It was renamed formation. Apparently much of the regional conglomerate horizon. Average thickness of the Marquenas quartzite of the Vadito Group shear and shortening was partitioned struc- the formation is approximately 60 m (200ft). by Long (1976),and subdivided into four in- turally abovethese rocks along a ductile thrust Metaconglomeraie layers of the Big Rock formal members by Scott (1980).Because the fault to the southwest (Williams, 1987).Be- Formation are lithologically similar to those Marquenas quartzite actually consistsof ap- cause of their relatively low strain, rocks at of the Marquenas Formation of the Picuris proximately equal amounts of metaconglom- Kiowa Mountain may preserve the primary Mountains. The averageclast size is greater, erate and quartzite, the name Marquenas characterof the Vadito Group-Hondo Group and the metaconglomeratesare thicker in the Formation is more appropriate than either contact. Here, feldspathic Vadito Group Marquenas Formation. The most notewor- Marquenas Conglomerateor Marquenas schists grade from impure feldspathic sedi- thy difference between the two formations Quartzite. The proposed type section is in ments and metarhyolite through impure is the large volume of impure quartzite in- the southern Picuris Range at Cerro de las metasediments(feldspathic schist and mus- terlayered with metaconglomeratein the Marquenasin secs.19 and 30, T23N, R11E. covitic quartzite) to the clean Ortega For- MarquenasFormation. In this area the Marquenas Formation is ap- mation quartzite of the Hondo Group proximately 500 m (1650ft) thick and can be (Williams, 1987).The upper contact of the traced laterally for 14 km (9 mi). Crossbeds Vadito Group is chosenas the lowermostex- Burned Mountain Formation throughout the unit indicate that it lacks ma- posure of the vitreous Ortega Formation.The (formerly Burned Mountain jor intemal folding and that stratigraphictops lower stratigraphic boundary of the Vadito Metarhyolite)-Tusas Mountains are to the north. Group has not been formally recognized in The Burned Mountain metarhvolite (Bar- Soegaard and Eriksson (1986) suggested the Tusas Mountains or elsewhere in north- ker, 1958),originally named th; Vallecitos that the Marquenas Formation is the young- ern New Mexico. However, the Burned Rhyolite by Just (7937),is a massive, quartz- est unit exposed in the Proterozoicof north- Mountain Formation and associatedmeta- feldspar rock characterized by distinctive ern New Mexico, and that the quartzite clasts conglomeratesin the northern TusasMoun- quartz and feldspar eyes in a fine-grained, were derived from the Ortega Formation of tains may be low in the original stratigraphy laminated matrix. The quartz eyesrange from the Hondo Group. We disagree with these (Gibson, 1981;Gabelman, 1988). Ductile or gray to deep red and display remarkably well conclusions. Although the Ortega Quartzite brittle faults mark the presentlyexposed lower preserved primary features including hex- contains abundant aluminum silicate min- Vadito Group contact throughout the Tusas agonal crystal shapes and resorption em- erals, we have found no Marquenas For- Mountains. bayments. Wobus (1985)proposed that the mation quartzite clasts that contain such Iust (1934 and Barker (1958)have distin- entire Vadito Group of the central Tusas minerals. Furthermore, even though the Or- guished a lithologic but not stratigraphic unit Mountains be included under the Burned tega Formation is thoroughly crossbedded, called Petacaschist, which occurs mainly in Mountain Metarhyolite name. This sugges- less than 1 percent of quartzite clasts in the the southeasternpart of the Vadito Group tion is unsatisfactory because of the great Marquenas Formation contain crossbedrem- reference section at Kiowa Mountain. They variety of rock fypes within the Vadito Group, nants (|. A. Grambling, pers. comm. 1.987). interpreted these rocks to representhydro- of which quartz-eye-bearing metamor- If the Marquenas Formation is the youngest thermally altered equivalentsof severalother phosed rhyolites are only a relatively minor unit in the Picuris Mountains, then both con- units, including rocks now assigned to the part. tactswith the Hondo Group andVadito Group Vadito Group and overlying Hondo Group. The metarhyolite can be followed along a must be faults or shear zones. Although the Wobus (1985)noted that many of the Petaca northwest-trending belt for approximately32 northern contact between the Marquenas schist rocks are actually typical Vadito Group km (20 mi) in the northern TusasMountains, Formation and the Hondo Group is a ductile lithologies, and Williams (1987)concluded where it ranges in thickness from 4.5 to 30 shearzone (Bauer,1988), there existsno field that the eastemmostexposures of Petacaschist m (15 to 100 ft) and represents a significant evidence to suggest that the southem Mar- are actually TresPiedras Granite. We support portion of the entire thickness of the Vadito quenas Formation contact with schist of the the suggestionof Wobus (1985)that the name Group there. We propose that this distinctive Vadito Group is a fault. Furthermore, dis- Petacaschist be abandoned. unit be formally designated as a formation continuous lensesof metaconglomerateand of the Vadito Group and 4amed Burned impure quartzite within the Vadito Group, Mountain Formation for exposures on the south and east of the Marquenas Formation (formerly Big Rock Formation Big Rock northwest side of Burned Mountain (Barker, type section, consistently contain crossbeds Conglomerate)-Tusas Mountains 1958). Detailed descriptions of the unit can indicating that stratigraphic tops are to the Barker(1958) originally mapped and named be found in fust (1,937),Barker (1958),Smith north. Thus, the Marquenas Formation is lo- the Big Rock conglomerate as a member of (L986),and Williams (1987). cated stratigraphically within the upper part the Kiowa Mountain formation of the central The age of the Burned Mountain Forma- of the Vadito Group. Each of the clast lith- Tusas Mountains. The unit can be divided tion, based on U/Pb ratios in zircon, is ap- ologies found in the Marquenas Formation into a lower member dominated by conglom- proximately 1,700 Ma (L. T. Silver, pers. metaconglomeratecould have been derived erate with minor interlayered micaceous comm. 1984). The Burned Mountain For- reasonablyfrom units within the adjacent quartzite and an upper member dominated mation is interpreted to be broadly equiva- Vadito Group. Given its lithology and strati- by micaceousand feldspathic quartzite. Be- lent to Vadito Group metarhyolites and graphic position, the Marquenas Formation causeof the lithologicalheterogeneity of these feldspathic,quartz-eye schists exposed in the is roughly equivalent to the Big Rock For- rocks, we propose the name Big Rock For- central and southern Tusas Mountains, the mation of the TusasMountains.

Nan Mexico Geology Augrst 1989 Glenwoody Formation-northern mian) in southeastern New Mexico (Lang, well constrained because no unequivocal Picuris Mountains 1937).Kelley (1971)recommended that the Precambrian igneous crosscutting relation- Approximately 300 m (1000 ft) of feld- term Hondo be dropped from usagebecause ships have been described.However, near spathic schist containing quartz and feldspar the Hondo sandstonememberof Lang(1937) Pecos Baldy in the Truchas Range, a felsic megacrystsare exposedbelow the Ortega is clearly a tongue of the Glorieta sandstone, stock appears to intrude metapelites of the Formation in the cliffs near Pilar in the north- and the original terminology has been com- Hondo Group (Grambling, 1986).If this stock ern Picuris Mountains. The base of this unit pletely replaced by the name Glorieta sand- does intrude the metapelites, then its U-Pb is nowhere exposed.Although originally in- stone. Just (1937) originally named a zircon isotopic age of approximately L,691 cluded as part of the Ortega Formation by Precambriary black, carbonaceousslate in the Ma provides a minimum age for deposition Montgomery (1953),it is dominantly meta- Picuris Mountains the Hondo slate.This unit of the Hondo Group (f. A. Grambling and volcanic (Gresensand Stensrud, 1974; Gram- was later renamed the Pilar Phyllite (Mont- S. A. Bowring/ pers. comm. 1986)in that bling and Williams, 1985;Bauer, 1988)and is gomery, 1953). The term Hondo slate has place. In the northern Sangre de Cristo here treated separately from the metasedi- since been recommended for abandonment Mountains, pegmatite dikes spatially related mentary quartzite. Previously,this schistwas (Jichaand Lochman-Balk,1958, p. 62) and to a1.,644Ma quartz monzonite intrude an informally called the felsic schist at Pilar is not currently used. Ortega{ike quartzite (Bowring et al., 79U; (Bauer, 1988).We propose that this unit be The stratigraphy of the Hondo Group is Reed, 1984). If the pegmatites and quartz formally named the Glenwoody Formation well established, but it lacks a designated monzonite are genetically related and if this and that it rank as a formation of the Vadito type section. Therefore, we recommend des- quartzite is equi'valent to the Ortega For- Group. The name Glenwoody comesfrom a ignation of a principal referencesection rather mation, then the Ortega Formation must be turn-of-the-century mining camp that stood than a type locality. The most complete,well- older than 1,644)Vla.If these intrusive rela- at the base of the cliffs. exposed, easily accessiblesection of the tionships are not genuine, then the Hondo Although the Glenwoody Formation is Hondo Group occurs in the Hondo Canyon Group is only constrained to be older than similar to the 1,700 Ma Vadito Group meta- area of the north-central Picuris Mountains. regional deformation and metamorphism, rhyolites that underlie the Ortega Formation The proposed referencesection is located in which by current,evidenceoccurred between of the Hondo Group in the TusasMountains the TaosSW 7t/z-minquadrangle in secs.29- 1,5N and 1,,450Ma (Robertsonet al., in press). and to other feldspathic schists in the Rio 32, T24N, R12E. This nearly complete, up- Mora area, Truchas Peaks area, and Rincon right section occurs on the north limb of a Ortega Formation Mountains, it is generally more schistoseand large overturned syncline, the Hondo syn- (formerly Ortega Quattzite) cline. A comparable, though less-accessible, homogeneous than these probable equiva- We propose to officially changethe Ortega section occursto the south on the overturned lents. This may be due to the relatively high, of the Llondo Group to formation limb of the syncline (Bauer, 1988).The lower Quartzite simple shearing strain that the Glenwoody status. The lower boundary is at the lower- boundary shatotype is set at the lowermost Formation has experienced.The Glenwoody most massivequarrtzite, above the immature massive pure quartzite, as described above Formation also contains a regionally exposed transitional metilsediments of the Vadito for the upper boundary of the Vadito Group Mn-rich horizon near its top, suggestingthat Group. By this, the Ortega Formation then in the TusasMountains. it may occur high in the original Vadito stra- defines the lower boundary of the Hondo A regionally extensive manganiferous tigraphy. Group. The uppr:r boundary of the Ortega marker laver. which occurs near the Vadito Formation is defirnedby the uppermost mas- Group-H6ndo Group boundary, aids in cor- Hondo (formerly sive pure quartzite occurrencebelow pelitic Group Ortega Group) relating Vadito-Hondo units across the dis- schist of the Rinconada Formation. We sug- The name Ortega was first used to de- continuously exposed Proterozoic terrain of gest the following supplemental reference scribea thick quartzite, quartzoseschist, and northern New Mexico (Grambling and Wil- sections for the C)rtegaFormation: 1) Ortega minor metaconglomerate,feldspathic schist, liams, 1985;Williams, 1987).The layer, char- Mountains, Braz<>suplift, where the Ortega and metarhyolite successionexposed in the acterized by Mn-andalusite (viridine), unit was originally described; 2) Tusas and Picuris Mountains of the Brazos piemontite (Mn-epidote), and other anom- Quartzite cliffs near Pilar, northem Picuris Mountains, uplift (just, 1937).Long (1975)proposed the alous phases, is 1 to 100 m thick and can be where the base of the quartzite is superbly name Ortega Group for a sequenceof meta- traced almost continuously acrossindividual exposed;3) jawbo,neSyncline, northem Tusas sediments in the Picuris Rangethat included uplifts. The exact stratigraphic position of Mountains, where original sedimentary a thick orthoquartzite (Ortega Formation) and the manganiferous zone varies from range structures are well preserved (Soegaardand the overlying schists and quartzites of the to range. Although the actual geographicex- Eriksson, 1985);and 4) RattlesnakeCanyon, Rinconada Formation. The presence of a tent of the anomalous laver is unknown, it south end of Copper Hill, south-central Pi- group and a formation with the name Ortega is exposed in every ru.,g" in northern New curis Mountains, where the uppermost is both confusing and unacceptableaccord- Mexico in which the Vadito Group,Hondo quartzite, including the kyanite and anda- ing to the North American Commission on Group contact is exposed and may correlate lusite schisVquartzitedescribed by Williams Stratigraphic Nomenclature (1983).Further- with similar Mn-rich rocks in Colorado and (L982),is well exposed. more, none of the schists or quartzites that Arizona (Williams, 1987).The origin of the overlie the Ortega Formation in the Picuris Mn-rich horizon is unknown. Williams (1987) Mountains and elsewhereare present in the concluded that most observations are con- Rinconada, Pilar, and Piedra Lumbre Tusas Mountains. Therefore, for these rea- sistent with a model involving syngenetic Formations of the Hondo GroupPicuris sons, and becausethe name Ortega Quartz- deposition from hydrothermal solutions or Mountains, Truchas Peaks area, ite is solidly enhenched in the literature, we from a widespread manganese enrichment Rio Mora area, llaos Range propose a change of the group name to cor- of basin waters at the end of Vadito Group The remaininl; three formations of the respond with the geographical location of the volcanism. Alternately, manganese and as- Hondo Group have been thoroughly de- new group reference section. sociated elements may have been concen- scribed elsewhere (Montgomery, 1953;Miller The name Hondo for exposures in the trated during weathering of Vadito Group et al., 1,963;Nielsen, 1972;Long, L976;Gram- Hondo Canyon area of the northern Picuris schists.If either of thesehypotheses is cor- bling, 1979;Grarnbling and Codding, 1982; Rangeis an appropriate geographicname for rect, the Mn-rich layer may represent a time Bauer, 1.988).We simply propose formal des- this important sequence of rocks. We pro- marker in the Proterozoic section. ignation of the RinconadaFormation, the Pilar pose that the name Hondo Group replacethe The Hondo Group is younger than ca 1,700 Formation, and the Piedra Lumbre Forma- name Ortega Group. The name Hondo was Ma, the age of the underlying Burned Moun- tion and their inclusion in the Hondo Group. applied previously to the Hondo sandstone tain Formation and equivalent metarhyolites Stratotypes are :rs described above for the member of the San Andres Formation (Per- of the Vadito Group. The younger age is not Hondo Group with a supplementalreference

August 1989 Nao Merin Geology section for the Rinconada Formation in the tains in the complex granitic terrain of the Mexico Geological Society, Guidebook to 35th Field Trampas Ttlz-min quadrangle near the Santa Fe Range by Miller et al. (1953).In Conference,pp. 141-145. boundary between secs. much not Bell, D. A., 1985,Stnrctural and age relationships in the 19 and 20, T23N, of this area,although mapping has Embudo Granites, Picuris Mountains, New Mexico: R11E,in RattlesnakeCanyon south of Cop- delineated individual plutons, reconnais- Unpublished M.S. thesis, University of Texas,Dallas, per Hill in the southern Picuris Mountains. sancework of Moench et al. (1988)suggests 775 pp. that the range may contain several different Bell, D. A., and Nielsen, K. C., 1985,Intrusion and de- formation sequence of the Embudo Granites, north- Felsic-dominated,ca 1,660-1,650Ma rocks intrusive bodies. We suggest that, for now, central New Mexico (abs.):Geological Society of Amer- the term Embudo granite complex be used The best-documented, ca'J.,650Ma, felsic- ica, Abstracts with Programs,v. 17, no.3, p. 151. to describe this complex granitic terrain. Bingler, E. C., 1974, Precambrian rocks of the Tusas dominated sequencein northern New Mex- Mountains: New MexicoGeological Society, Guidebook ico occurs in the Dalton Canyon-Glorieta to 25th Field Conference,pp. 109-113. Baldy-Thompson Peak area of the southern Summary Boadi, I. O.,19tK, Gold rnineralization and Precambrian Sangre de Cristo Mountains. The rocks in geology of the Hopewell Lake area, Rio Arriba Counry, Several revisions and redefinitions of New Mexico: Unpublished M.S. thesis, New Mexico that areawere describedfirst by Moench and stratigraphic nomenclature in the Protero- Institute of Mining and Technology,Socono, 107 pp. Erickson (1980)in a reconnaissancestudy and zoic rocks of northern New Mexico are pro- Bowring, S. A., and Condie, K. C., 1:982,U-Pb zircon in moredetail by Fulp (1982),Renshaw (i984), posed.The two most significantsuggestions ages from northern and central New Mexico (abs.): and Wakefield (unpub. map). In general, Geological Society of America, Abstracts with Pro- J. are: 1) to adopt the name Vadito Group for v. p.3M. the sequence consists of metamorphosed grams, 14, no. 6. the extensive ca 1,700 Ma, felsic metavol- Bowring, S. A., Reed,l.C.,lr., and Condie,K. C., 1984, quartzo-feldspathic sedimentary and vol- canic/metasedimentaryrock packageex- U-Pb geochronology of Proterozoicvolcanic and plu- canic rocks intruded by pre- to syn-volcanic posed directly below the Ortega Formation tonic rocks, Sangrede Cristo Mountains, New Mexico quartz porphyry bodies with U-Pb zircon (abs.): Geological Society of America, Abstracts with of the Hondo Group, and to designatea ref- Programs,v. 15, no. 4, p.216. isotopicages determined by S.A. Bowring of erence section in the central Tusas Moun- Burns, L. K., and Wobus, R. A., 1983,Correlations and 1,550-r10 Ma (Fulp, 1982)and 1,650+ 10 Ma tains; and 2) to propose the name Hondo revisions of Precambrianstratigraphy, Needle Moun- (Renshaw, 1984). These rocks, and similar Group for the regionally extensive, metase- tains, southwest Colorado, ad TusasMountains, north- units to the north, were informally named central New Mexico (abs.):Geological Society of Amer- dimentary sequencebeginning with the Or- ica, Abstracts with Programs,v. 15, no. 5, p. 424. the Dalton Canyon successionby Robertson tega Formation that occursdirectly above the Condie, K. C., 1978,Geochemishy of Proterozoicgranitic and Condie (1989).We suggestno changes Vadito Group. These rocks were previously plutons from New Mexico, U.S.A.: Chemical Geology, to this nomenclature. called the Ortega Group. v. 21, no. 712,pp.137-149. Condie, K. C., and McCrink, T. P., 7982,Geochemishy Some workers may find these changes of Proterozoic volcanic rocks from Gold Hill-Wheeler Plutonic rocks awkward at first, but we are convinced that Peak area, northern New Mexico: Precarnbrian Re- Precambrian plutonic rocks in northern both are necessaryfor a precise exchangeof search,v. 19, no.2, pp. 141-166. scientific information. The suggestions out- Fulp, M. 5.,1982, Precambriangeology and mineraliza- New Mexico rangewidely in compositionand tion of the Dalton Canyon volcanic center, Santa Fe age (Condie, 1978).Most plutonic terrains lined in this paper are the first step toward County, New Mexico: Unpublished M.S. thesis, Uni- contain more than one generation of intru- this goal. We hope that, as investigation into versity of New Mexico, Albuquerque, 199 pp. sions, and in most areasof northern New the Precambrianhistory of New Mexico con- Gabelman,J. L., 1988,Precambrian geology of the upper tinues, the nomenclatureproposed above will BrazosBox area, Rio Amiba County, New Mexico: Un- Mexico detailed mapping, petrography, and published M.S. thesis,New Mexico Institute of Mining geochemistry are insufficient for adequately provide a consistent basis for further com- and Technology,Socorro, 171pp. delineating individual plutons or cogenetic munication and will promote a more accu- Gibson, T. E., 1981,Precambrian geology of the Bumed phases of intrusion. Many plutonic bodies rate and regionally compatible system of Mountain-Hopewell lake area, Rio Aniba County, New Medco: M.S. thesis, New Mexico Insti- carry local names. At this time we suggest nomenclature. Unpublished AcrNowreocMENrs-The New Mexico tute of Mining and Techno.logy,Socono, 105pp. only a revision of plutonic nomenclature in Grambling, J. A., 1979, Geology of Precambrianmeta- the southern Picuris Mountains, where map- Bureau of Mines and Mineral Resources morphic rocks of the TruchasPeaks area, north-central ping and geochronology are excellent. All (Frank Kottlowski, Director) provided sup- New Mexico: Unpublished Ph.D. dissertation, Prince- ton University, 269 pp. other nomenclature should be maintained port for this work. The content was influ- Grambling, I. A., 19[36,A regional gradient in the com- until additional information is available. enced and greatly improved by lively position of metamorphic fluids in pelitic schist, Pecos discussionswith famie Robertson.We thank Baldy, New Mexico: Contributions to Mineralogy and Embudo Granite fon Callender, Jeff Grambling, Chris Mawer, Petrology, v. 94, pp. 149-764. Reed, and Robertsonfor thought- Grarnbling,J. A., and Codding,D.8.,1982, Stratigraphic fack famie in deformed We propose that the name Embudo Gran- ful text reviews. Useful and supportive com- and structural relationships multiplv Pre- ite be abandoned for any and all plutonic cambrian metamorphicroiks in the Rio'Moraarea, New ments were also received from F. Barker, E. Mexico: GeologicalSociety of America, Bulletin, v. 93, rocks in the Picuris Mountains. It is now Bingler, P. Fullager, W. Muehlberger, and R. no.2, pp. 727-737. known that the granitic terrain of the south- Wobus. Grambling, J. A., and Williams, M. L., 1985,Correlation ern Picuris Mountains, originally called the of Proterozoicstratigaphy acrossnorthern New Mex- Embudo Granite or Embudo Granites (Mont- ico (abs.):Sixth International Conferenceon Basement Tectonics,Abstracts with Programs,v. 6, pp. 18-19. gomery/ 1953),actually consists of four dis- Grambling,J. A., Williams, M. L., and Mawer, C. K., tinct plutons that rangewidely in chemistry, References 1988, Proterozoic tectonic assembly of New Mexico: mineralogy, and U-Pb zircon isotopic age Barker, F., 1958,Precambrian and Tertiary geologyof las Geology, v. 15, pp. 724-727. (Long, 1974, 1975;Bell, 1985;Bell and Niel- Thblasquadrangle, New Mexico: New Mexico Bureau Grambling,J. A., Williams,M. L., Smith, R. S., and Mawer, of Mines and Mineral Resources,Bulletin 45, 104pp. C. K., 1989,The role of crustal extension in the meta- sen, 1985).These are the Puntiagudo granite Barker, F., and Friedman, 1.,1974, Precambrian meta- morphism of Proterozoicrocks in northern New Mex- porphyry (1,684+1 Ma), the Rana quartz volcanic rocks of the Tusas Mountains, New Mexico: ico: Geological Society of Arnerica, Special Paper 235, monzonite(1.,674*5 Ma), the CerroAlto me- maior elementsand orygen isotopes:New Mexico Geo- pp. 87-110. tadacite, and the Pefrascoquartz monzonite logical Society, Guidebook to 25th Field Conference, Gresens, R. L., and Stensrud, H. L., 7974,Recognition pp. 115-117. of more metarhyolite occurrencesin northern New (ca 1,450Ma). A fine-grainedplutonic body Barker, F., Peterman, Z. E., Henderson, W. T., and Hil- Mexico and a possible Precambrianshatigraphy: The exposed in the easternmost Picuris Moun- dreth, R. A., 1974,Rubidium-strontium dating of the Mountain Geologist, v. 11, no. 3, pp.109-12a. tains, on the east side of the PicurirPecos trondhiemite of Rio Brazos, New Mexico, and of the Holcombe, R. J., and Callender, J. F.,1982, Structural fault, is probably distinct and should be called Kroenke Granodiorite, Colorado: U.S. GeologicalSur- analysis and shatigraphic problems of Precambrim rocks vey, fournal of Research,v.2, no. 6, pp.705J09, of the Picuris Range, New Mexico: GeologicalSociety the granite of Alamo Canyon, following the Bauer, P. W., 1988, Precambriangeology of the Picuris of America, Bulletin, v. 93, no. 2, pp. 138-149. informal usage of Bauer (1988). The name Ran8e, north-central New Mexico: New Mexico Bureau Holcombe, R. I., Bauer,P. W-, and Callender,J. F., 1985, Embudo is therefore obsolete in the Picuris of Mines and Mineral Resources,Open-file Report 325, A kinematic model for the polyphase deformation of Mountains. 2s9pp. Proterozoic rocks, Picuris Range, northem New Mex- Bauet, P. W., and Williams, M. L., 1985,Structural rela- ico, U.S.A. (abs.): Sixth Intemational Conference on The name Embudo has also been applied tionships and mylonites in Proterozoic rocks of the BasementTectonics, Abstracts with Programs,v. 5, p. to plutonic rocks south of the Picuris Moun- northern Pedemal Hills. central New Mexico: New 20.

Nm Mexico Geolo8y August 1989 Jicha,H. L., and Lochman-Balk,C., 1958,Lexiconof New San Miguel, Mora, Rio Arriba, and Taoscounties, New Soegaard,K., and Er:iksson,K. A., 1986,Transition from Mexico geologic names: Precambrian through Paleo- Mexjco: U.S. Geolosical Society, MiscellaneousField arc volcanism to stable-shelfand consequent conver- zoic: New Mexico Bureau of Mines and Mineral Re- StudiesMap MF-1921-8,scale i:,1U,000. gent-marginsedimentation in northern New Mexico sources,Bulletin 67,137 pp. Montgomery, A., 1953, Precambriangeology of the Pi- from L.76 Ga: Journal of Geology, v. 94, no. 1, pp. 47- I.ust,E., 7937,Geology and economicfeatures of the peg- curis Range, north-central New Mexico: New Mexico 66. matites Taosand of Rio Aniba Counties, New Mexico: Bureau of Mines and Mineral Resources,Bulletin 30, Stary, ]. S., and others, 1976,Plumbotectonics II A, Pre- New Mexico Bureau of Mines and Mineral Resources, 89 Pp. cambrian massivesulfide deposits:U. S. GeologicalSur- Bulletin 13, 73 pp. Nielsen, K. C., 7972,Structural evolution of the Picuris vey, Open-file Reqort 75-476, 25 Pp. Kelley, V. C., 1977, Geology of the Pecoscountry, south- Mountains, New Mexico: Unpublished M.S. thesis, Steiger, R. H., and E., Dn, Subcommissionon easternNew Jager, Mexico: New Mexico Bureauof Mines and Universityof North Carolina,Chapel Hill, 47 pp. geochronology: Convention on the use of decay con- Mineral Resources,Memoir 24,75 pp. North American Commission on Stratigraphic Nomen- stants in geo- and cosmochronology:Earth and Pla- Kent, S. C., 79ffi, Precambrian geology of the Tusas clature, 1983, North American StratigraphicCode: netary ScienceLetters, v 36, pp.359-i62. Mountain area, Rio Arriba Counfy, New Mexico: Un- American Association of Peholeum Geologists, Bulle- L977, Precambrian geolo6y of the Ojo published M.S. thesis, New Mexico Institute of Mining Treiman, A. H., tin, v. 67, no. 5, pp. U7-875. and TaosCoturties, New and Technology,Socono, 150 pp. Caliente quadrangk, Rio Arriba Reed, C., 1984,Proterozoic rocks of the TaosRange, Ph.D. dissertation,Stanford Uni- Klich, I., 1983,Precambrian geology of the Elk Mountain- J. Jr., Mexjco: Unpublish,ed Sangrede Cristo Mountains, New Mexico:New Mexico versity, Stanford, 93 pp. Spring Mountain area, San Miguel County, New Mex- Geological Society, Guidebook to 35th Field Confer- ico: New Mexico Bureau of Mines and Mineral Re- Williams, M. L.,19U, Geology of the copper occunence ence, pp. 179-185. sources,Open-file Report 180, 17Opp. at Copper Hill, Picuris Mountains, New Mexico: Un- Renshaw, L.,1984, Precambriangeology of the Thomp- Lang, W. 8., 1937,The Permian formations of the Pecos J. published M.S. thesis, University of Arizona, Tucson, son Peak area, SantaFe New Mexico: Unpub- Valley of New Mexico and Texas:American Association County, 98 PP. lished M.S. thesis, University of New Mexico, of Petrofeum Geologists,Bulletin, v. 21, no. 7, pp. 833- Williams, M. L., 1987,, Shati$aphic, structuml, and meta- 898. Albuquerque, 197 pp. morphic relationships in Proterorcic ro&s from north- Robertson, M., and K. Geologyand Lipman, P W., and Reed, J. C., lt.,1989, Geologic map J. Condie, C.,1989, em New Mexico: Unpubtshed Ph.D. dissertation, of the Latir volcanic field and adjacentareas, northern geochemistry of Early Proterozoic volcanic and sub- University of New Mexico, Albuquerque, 138 pp. volcanic rocks of the Pecosgreenstone belt, Sangrede New Mexico: U.S. GeologicalSurvey Miscellaneousln- Williams, M. L., Grambling, I. A., and Bowring, S. A., vestigations SeriesMap I-1907, scale1:11[},000. Cristo Mountains, New Mexico: GeologicalSociety of 1985, Redefinition of the Vadito Group, an extensive Long, P. 8., 1974,Contrasting types of Precambriangra- America, SpecialPaper 235, pp.719-146. felsic volcanic-sedirnentarysequence in the Proterozoic nitic rocks in the Dixon-Penasco area, northem New Robertson,J. M., Grambling,J.A.,Mawer, C. K., Bowr- of northern New Ivlexico (abs.): Geological Society of Mexico: New Mexico GeologicalSociety, Guidebook to ing, S. A., Williams, M. L., Bauer, P W., and Silver, America, Abstractswith Programs,v. 1,8,no. 5, p. 472. L. T., (in press), Precambrianof New Mexicoi in Reed, 25th Field Conference,pp. 101-108. Wobus, R. A-, 1985, Changes in the nomenclature and (ed.), The Precambrian:Conterminous U.S.: long, P E., 1976,Precambrim granitic rocks of the Dixon- 1.C., Jr. shatigraphy of Proterozoic metamorphic rocks, Tusas Geological Society of America, DNAG Volume. Pefrascoarea, northem New Mexico: New Mexico Bu- Mountains, north-central New Mexico: U.S. Geological Pecos reau of Mines and Mineral Resources,Open-file report Robertson, J. M., and Moench, R. H., 1979,The Survey, Bulletin 15',77,19 pp. greenstoflebelt: a Proterozoicvolcano-sedimentary se- 71,557pp. Wobus, R. A., 7989, Proterozoicsupracrustal rocks and quence in the southem Sangre de Cristo Mountains, McCarty, R. M., 1983, Stmctural geology and pehogra- plutons of the Cimarron Canyon area, north-central New Mexico: New Mexico Geological Society,Guide- phy of part of the PrecambrianVadito Group, Picuris New Mexico: GeologrcalSociety of America, Special book to 30th Field Conference, pp. 155-173. Mountains, New Mexico: Unpublished M.S. thesis, Paper235, pp. 111-118. University of New Mexico, Albuquerque, 159 pp. S€ott, T. E., 1r.,19ffi, A strain analysisof the Marquenas Wobus, R. A., and Hedge, C. E., L982, Redefinition of Miller, J. P., Montgomery, A., and Sutherland,P. K., 1%3, Quartzite and contact relations of Ortega-Vadito GrcuPs: Precambrian Tusas Mountain and Tres Piedras Geology of part of the Sangre de Cristo Mountains, Unpublished M.S. thesis, University of Texas,Dallas, the north-central New Mexico:The Mountain Ge- New Mexico:New Mexico Bureauof Mines and Mineral r73 pp. granites, ologist, v. 19, no. 4, pp. 105-114. Resources,Memoir 11, 106 pp. Smith, S., 1986, Precambrian geology of the Jawbone Moench, R. H., and Erickson, M. 5., 1980, Occurrence Mountain area, Rio Arriba County, New Mexico: Un- Wobus, R. A., and N{anley, K.,1982a, Reconnaissance of tungsten in the Sangrede Cristo Range near Santa published M.S. thesis,New Mexico Institute of Mining geologic map of the Burned Mountain quadrangle,Rio Fe, New Mexico: Possible stratabound scheelite pe- of Technology,Socorro, I pp. Arriba County, Nerv Mexico: U.S. Geological Survey, ripheral to favorable settings for volcanogenic massive Soegaard,K., and Eriksson, K. A., 1985,Evidence of tide, MiscellaneousField StudiesMap MF-14{I), scale1:24,000. sulfide deposits: U.S. GeologicalSuruey, Open-file Re- storm, and wave interaction on a Precambrian silici- Wobus, R. A., and Manley, K., 7982b,Reconnaissance port 80-1125,21 pp. dastic shelf: The 1,700M.Y. Ortega Group, New Mex- geologic rnap of the Las Tablas quadrangle, Rio Arriba Moench, R. H., Grambtng, I- A., and Robertson,J. M., ico: Journal of Sedimentary Petrology,v. 55, no. 5, pp. County, New Mexico: U.S. GeologicalSuruey, Miscel- 1988,Geologic map of the PecosWilderness, Santa Fe, 672-&. laneous Field Studies Map MF-14108,scale 1:24,000.!

___ co! 9RA00 ______. Gallfor Paoers NEWMEXICO

NMGS1990 fall field conlerence

The New Mexico Geological Society chaeology, anthropology, and zoology- will visit the eastern Sangre de Cristo- botany. If you would like to contribute Moreno Valley-Cimarron Mountains area or if you know of anyone who might be of northern New Mexico on Sept. 12-15 convinced to contribute, please contact for its 41st fall field conference. Chris us as soon as possible. The submittal o Mawer and Paul Bauer are general co- deadline for reviewed papers will be chairman for the trip; the theme is tec- February 15, 1990. tonic development of the southem Rocky The guidebook editors are Chris Mountains, New Mexico. NMGS trips Mawer, Paul Bauer, and Steve Hayden; to this part of the statewere held in 1956 managing editor is Spencer Lucas. For and 196f.,but some of the route had never information and guidelines for authors, been included in an NMGS roadlog. contact either Christopher K. Mawer, We are soliciting peer-reviewed pa- Dept. of Geology, Univ. of New Mexico, pers for the guidebook. Although we Albuquerque, NM 87l3l, (505)277 -4808 6, wish to emphasize original geologic re- or Paul W. Bauer, NMBMMR, Campus o) search, we also encourage mini-paper Station, Socorro, NM 8780L,(505) 835- contributions on mining history, ar- 5106.

August 1989 New Mexieo Geology