NEW MEXJCO BUREAU OF MINES & MINERAL RESOURCES A DIVISION OF NEW MEXICO INSTITUTE OF MJNINC & TECHNOLOGY GEOLOGIC MAP 66
108° 52'30" 35u3a· 29 CORRELATION OF UNITS
Qal Q,e Qcl QUATERNARY
PLIOCENE unconform,ty
Kg, { , ,, Qal minor LJnmnform1 ty :, 3: Kg,
UPPER CRETACEOUS Km,
Kmw
T 1 5 r.J
T 1 c. r.J T 15 N T 14 N unconformity
MIDDLE JURASSIC
unconformity
DESCRIPTION OF UNITS
Al!uviaJ deposits (Quaternary]-san:J, ,ill, d ov, and ni 111u r ,iruwJ rrnd sanC,tcne bouklt:r, 11 1 Iii,; rr ,c1or dro,nages, their r'1 bll!ar1es, and floodplrnri,, lrurn several feet to more rhan 50 ft thick
Mostly eolilln deposits (Quaternary}--very f111e gra,nec w,ndl,I;.,,,,, g sand m sheet depos,r,; veroe,;r~ ull,Jv1al or collu1•1o l c'epos1ts; n::i roc og11i~ul,I., dune form~
Colluvium n 5Jopes Or.I I rl.svelnped on ,Vtc,r,c<:;s Si,ule, 1n d,Jdes torevo blocks
Upper member of Bidahochi Formation (Pliocene?)- mo:forn1cly reddish br::wn to l1gh1-brwm. poc,r!y 1ndumtec. arg,llnceo _1 1 mnd,lone with lesser amounts of ponrl·, sorted, carboncte-cerne01le!<..l :;o;; dotom;
27'30" LT?,0' Crevasse Canyon Formation (Co11iocion)----{ln mterl::edded '58- quence of sholc, mud~1ooc, ICmt1culcr sandstones, rnrbor,ncf'c.u, mur. W>n c :)r sh::ile, and m,ror Ct'>c1 1, nnrl mud ,ton"' dcwn nnle the !eci1on and vory 111 ~olor from ,ned;unl g ruy, lhruu'dl, l:m.;wrush gray, to dark grc:iy; sur1d,;t<.Jne:; ure fine to upper medium gr::i,ned. ore trough cross bedded, and vory from ycllowi.r gray to pole :,,cllov.1sh brnwn, ,..,,,th pale r,,d frmnrl npproximDtely JOO fr above the bo5e, ,n the N112 ,ec. 22 T14M Rl?W at qt. arlrnngle h-'.lun:::lo ry, thickness vcories from C, lo cpprox,mately 500 fl 1n ;ub,;ur!uuo; gc.><.Jd uutcrup> al Pun•; Rock (Torrivio Member of Gallup Sand$tone (Coniacian?)--,fo1inch""', medium to very caor.1e grni11eJ /.,lusf.)<.lthic sunds·cne. common Iv reddish b, O\,n w, rh f'''-'"'-'Lmced crossbeccing, cr~sbed sets indicc1c P::i!coflow d1rectio 0 ,s to north, northemt, :md Ramah unit of Gallup Sandstone (Turonian)-vnnnhle: ,equen:,. :)f mudstonr: . lr,nt,rnlar fluv1al-channel sandstooe, oorboricrnous mu::i sbn,e, n o1 d minor ccc,I; one cool be,(; r=d,.,, 3 5 Ft ,n trickness but IS nol r-:ers1srenl· ~nit I> a coastal plair end lo,1,cr olluv1ol-plo1n sequence that overlie~ regrcss,vc IT,ormc Gallup. ?4----150 ft th,d, 1h1n5 ec,s·ward or Tomv10 o nt d 1ne, unit " litho,1enet1cally a 1011!-,ue ul lhe Di leo Coal Member but h::i.1 beeu ,riduGollup Sandstone, main part, undivided (Turonian}-ver·, pole orange, y.,l lowi,h-siruy. ,:md grayish-orange, v::,ry i1nc to fine-groined quortwse 5an:Jstone 1n coarsening-upward sRio Salodo Tongue of Mancos Shale (Cenomanian and Tt1ron ,,J, ion}--light- b OOrk-gray s~ole and arenaceovs 5hale, base al c·nil ' / ' shorp on t::,p of 1,,/0wells fangue, platy l111 lt!s!Q r1 ,:, <.kibn, lrorn Bridge I ,:,.,..k Lirnestone Member of Gr*nhorn FormJtion foord ,n float, but net 1n curaop, in SE/,; sec 20 Tl4N R20N; top cf unit grodatic,nc,I through 20 ft into r.v,erl·,mo Go llu ,c:i Scndstooe, 350- 400 -ft thick
Twowells Tongue of Dokota Sandstone (Cenomanion)-lun umJ ver:, p:Jle ::i-Unge, lo'1'1e1-very f, ne y1uint:U Iv lv11i,,r-rnocd 1u m-gro 1n ed yuartzoo\l ,;andstone, l::ioturb:ited and burrcwcd, includrng 'Jph1amor pha and Tha/arnnc:>.'dm, rippjc> lnm,nnt>::,n~ pr~ser.ed localIv m ,rnddle por1, bcse of L1n1t " lower very fine grrnned ond flat be:dcleU; upf!"'r par1 of uriil i, f,..., lo le srussbeds; generoll1 30-35 ft thick b~t rh1n~ 10 <25 ft in SE 1/,, sec 20 T14N R20W
Whitew1;1ter Anoyo Tongue of Mancos Shale (Cenomonion)- groy to dnrk-gm)', s.lty marine 1hale; bcse of u111l , sho1p; co,-1oim ver)' Ihm, ::,,unqe-wecll1erinsi bentomte beds. 20- 40 t1 ·hick with ,he 11, """'' uut,:rops along frontage road •n SW'/4 sec. 20 Tl 4N R20W
Main body of Dakota Sandstone (Cvn0moni1;1n)-----g,ay1sh 25' 25 aronge ond very pale, a ,or-ye, fir,e- to coorsc-grrn ned conrlstor,e, con glornerulic sandstone, mu::!stanc, corboncceD1J• mudstor,e, ond cooly corbanoccovs , ~ale, brirol port ,s d flu"ol uriqiro Zuni Sandstone (Middle Jurossic)-v..,ry /we tD rned,um-g.ained, J, while 10 pmk1sh-gra'f quortmse 5ondstone characte1 1zed by meJiur, t<.J th,ck sets of pla1101 end plu11m- lu•1\,jent1al, high-angle croSl:beds; crcss bed-d1p U,r,:,,Jiun vcrnable, b·Jt soo:h, soutreost, o r,c' Joutrl we st ore ccmmon; eoli an m or1gm for most port, mnv ron1e, up to /OG ft thick locally. Zun, is th e ond ,v,ded eq u,vale,nt of lli e E11 lrmld·<.md Cow Springs Sandstones, which Genemlly are not mopp.:,ble u, sepornle c•nirs in thio area
MAP SYMBOLS T 14 N T.13 N T 14 N • T 13 N C 1 6 Mco5ured coal locd,ty wrth thickness in feet
Pu le\)tlQw d1rect1ons based an crossbed sets
foull ,l,uwir,\! sfri ~e-slip movcrnc~t
[aJditi,.mal symbols on envelope)
~ e 3" z J w !! a e f " 0 i{
APPROXIMATE iv,EAN IN[)F,X Mi\!' Of NEW MEXJCO lJfCLINATION, 1907
35' 22 30" 35 · 22'30" 109° 00' 57'30" 55' R.20W. il19W 108"52'30"" [\05e ham LI 5 Geolog,co l Su,vey Gaalog1c color separations end la~·aut by C A. Soliob•Jr',' and J . 0. Cheney {jeology by O J Anderson. 1YH5 Scale 1,24,000 Ed,1..d by J. C. Love
½ 0 1 MILE
5 0 1 KILOMETER
A Manuelito Burned Out A' Manuelito Torrivio Canyon Co11yon SW syncline anticline I
feet
7800
7400
7000 Kd Kd, Gal Kmw Kgr ...... _ Kgt, Dal ' \ K1T,r 6200 ff 'w. ~' Kd 5800
5~00 Jz Kd
5000 - 5000 Triassic
Geology and mineral resources of Manuelito quadrangle, McKinley County, New Mexico
by Orin J. Anderson, 1991
Nev.J ,7\tfexico Rurcau of Mines [t Mineral Resources, Socorro, NM 87801
V\iilli.-1ms Acres extends mlo lhe nor lheasl corner. and the alluvial-valley Ooors have a cover of bunch grasses, regional study, as well as the geology and landscape along nmthcast corner (Fig. 1), reverses structural dip to form an fenneman (1931) included this area in the Navaio Section shrubs, and scattered cactus. the mute of the Santd Fe Railroad; Sears (1925), who studied assonaled syncline on tJ1e west, and brmgs Mancos Shale of the Colorado Plateflu physiogmphic province. Topo Previous work in the area includes that of Darton (1910, and reported on the Cretaceous stratigraphy and coal re to the surface in an area surrounded by the Crevasse Can grnphically, the quadrangle consists of mesas, Luestas, Cdil 1915), who described the Zuni Basin in the course of a sources of the Gallup---Zuni Basin; Shomaker et al. (1971), yon Formc1tion. The west limb is the steeper with dips as who indllded the C:ilhip--Zuni Basin in a r('git0nal evalua much d S 21": dips on the east limb, which is Dff the quad yons, and alluvial-valley floors developed on Jurassic and 109"00' Cretaceous rocks. Local relief is approximately 600 ft; max SA ... SO~ L.SSE GA.LUI' WC51 ~~·.1-ur e•sr tion of strippable coal resuumc!S; and Muleuaar (1983), who rangle, do not exceed 7'. The anticline plunges bolh lo lhe imum relief of 920 ft exists between the low of 6,220 ft 1m established a reference section and described in detail the north and the south; however, the northward plunge is Gallup Sandstone m northwestern New Mexico. The geol more abrupt, and the structure dis.1ppe0rs 4 mi to the north. Frum Darton, 1928. the channel lloor of the Puerco River lo the high of 7,140 ( ft on small buttes capped by Tertiary sediments in the south ogy of the Huntrrs Point quadrangle, immediately north Structural rehef on the anticline is estimated at I,(J(XJ ft east corner of the quadrangle. Large l;indslide blocks nnd west of Manuelilo quadrangle, was detailed by Condon on cross sect10n A-A'. Drill-hole mformation from the SE Gallup \ co\luvium arc prevalent at the bases of the more prominent (1986). Most recently, Anderson (1989, 1990) has completed 11,._ sec. 19 TlSN R19W indicates that the depth to Precam bri,m basement from the floor of the w;itcr gilp through the Abstract cliffs and mask outcrops of lhe slope-forming Mancos Shale mapping and minefal-resource investigations in the quad and the Twowells Tongue of the Dakota Sandstone. rangles immediately to the southeast and south. anticline is 4,890 fl Tluee miles downdip lo the nodheast, The Manuelito 71 /~-min quadrangle lies in the north Mineral resour{_·es in lhe 4uadrangle are limited. Coal has The Puerco River is the major drainage for the northern AcKNOWLEDCMENTS--This geologic mapping prOject is the a drill hole m sec. 3 TlSN Rl9W encountered basement rock WC"stem part of the Zu rn Rasin in wPst-ce11trdl New Mexico. been produced in very small quantities, and a small coal Zurn Hasin amJ tiw Cc1llup-Churd1 Rock vicinity 1L is a result of encouragement from Frank Kottlowski, Director nt 6,828 ft (grotu1d level same for both holes). With a re The area is charadenzed bv mesas, canyons, and cuestas resource exists in the Ramah unit o( the Gnllup Sandstone perenrnal stn:>am, a tributa1y of the Little Colorado River, of the New Mexico Bnrcm1 ofMrnes and MinNzil Rf'smirccs, gional dip of approximately 300 ft per mile, 900- 1,000 ft of cut in the gently northeast~'ard-dipping- Jurassic and Cre Severn] tPst wells h;1ve bl:'e11 dnlled in the area, some of and flows southwestward through the Manuelito urea, to extend investigatrnns of Cretaceous rutks cmd assuoated tlus nearly 2,0CX)-ft difference in deplh lo basemenl can be taceous rocks This structural pattern is interrupted in the which bollomed m Precambnan basement. No oi l or gas .:igainst structur.::il dip, with a gradient of 17.5 ft per mile. coal resources northwestward from the Pinehaven area to accounted for; thus the 1,0C>O-ft estimate for structural relief shows were reported No aggregate pits or aggregate de northeastern corner uf the quadningle by the Tmriv10 anl1- 'Jhe waler g<1p it has cut throu~h the Torn 't'lO anltdme prn the Manuelito area The New Mexico Bureau of :\1ines and on thf' nnt1clin c. is substantinted Basemf'nt involvement in d111e, a norlh- norlhwesl-trendmg, doubly plunging: feature posits exist in the quadrangle, however, a large borrow pit v1des excellent exposu1es of lhe Gallup Sands lone. The al Mineral Resources provided the support for the field work this strudun' 1,-; also lkmunstrated. with 1000 ft of structural relief The anticline and an asso supplied fill matPrial for construction uf 1- 40, which runs luvial-valley floor along the Puerco River exceeds a mile in Special thanks go to Stephen C. Houk and C. M. Molenaar The natW"e of the controlling basement faults is not well ciated syncline on the west flank constitute thP only ap diaia;unally northeast across the quadrangle. \.Vidth at many junctures. The major trihutc1rir s nre Defiance for Lheir help in fauna! idenl1fication; to Richard M. Cham constrained, and thus they are not shown on the cross parC"nt structure in the quadrangle. Dr,nv, which enters Llw tru11k. slream in the northeasl parl berlin, Charles E. Chapin, Spencer G_ Lucas, Marvin L section. The stmctmc is different from thnt of the :,J'ntria Middle Jurassic, Uppe1 C1etaceous, and Tertiary rocks Millgate, and Donald L. \'\,'olh<'rg for reviewing and im monodine and Galestina- Atarqutc monodines described by INTRODUCTION of the quad1angle and Manue!Jto Canyon1 which enters m are exposed. The Middle Jurassic is represented by the Zuni the southwestern part. In this southwestern area, the Puerco proVIng the: map and text; and tu Lynne McNeil, who typed Anderson (1987) fa1ther south in Lhe basin. These laller Sandstone and, according to some ,111thors (Condon and Mnnuf'hto qtrndrangle is located 6 mi west- southwe~t of has cut through a homoclinf' devPlopPd on a 0;:iknta S;:ind the manuscript. A note of appreciation also goes to Chester structures are narrow, sharp flexures produced by reverse Huffman, 1984), locally by a tun)a;UI.! uf eolian Recaplure Gallup, New Mexico, in the norlhweslern part of the Zuni stone dip slope. and the rt>sultmg water g:ap provides good Nez, president ol the Manuelito chapter house, and to Lenny or thrust foulting. Thl' Torrivio is a broad intrabasinal fold Member of Morrison Formation at the top of the Zuni. The Basin (Fig. 1), Access is provided by 1-40, which crosses exposures oi the Jurassic Zurn Sandslone and overlying Parker, Ellen Parker, Jim Spencer, Jaquelin Chl'l', and otfwr lhal may reflect a different style nf b.1semenl faulting. Upper Cretaceous rocks consist of the Dakota Sandstone the quadrangle from northeast to southwest. A frontage Dakota Sandstone_ The Puerco and Manuelito Canyon residents ul the area, whu kindly penrnlled me access to (Cenomaman) at the base, Manms Shale, Callup Sand TOild parnllels the mterstatc highw;iy on the scrnth for the strmms arc rrunal water snurres For thf' ranching and livc thcu property 01 grazmg leases for the purpose of mapping STRATJGRAPHY stone, and Crevasse Canyon Formation, the last two being most part. aod the Sanla Fe Railroad t1acks parallel it on slock mduslry m lhe area. and sample collecting coal bearing. A late Tertiary basin-fill unit, the Bidahochi the north. The routes follow the vallcv of the Puerco River. No d1 y-land farmmg has been attempted in this area be fhe rnmposite stratih'Taphic column (Fi~. 2) illustrates the Formation (Pliocene?), is present over a very limited area Numerous dirt roads lead off this m'ain route and extend cause of the rugged topography and also because annual STRUCTURE relationships of JuraSSlC through Tertiary rocks exposed in in the southeast cornt:'r of the quadrangle. These erosional up the tributaries to scattered dwellings and snwll ranches. precipitation is generally less than 13 indies. The mesas the Manuelito quadrangle. The figure is based on measured renmanls of the B1dahochi are Jess than 45 ft thick but are No rncorporaled cil!es exist in the quadrangle, but the aban and upland surfaces above 6,500 fl haV€ a moderate cover Uniform northeastward dips m the range of2°-6° descnbc sections at eight loc.:ilitif's. The th1cknPsses of subsurface FIGURE I-Index map of north half of Zuni Basin showing location the structure of all but tht> northeast cornl-'r uf the Manuelito umts shown on cross section A-A' were ob tamed from two of interest because they represent the northernmost out doned villages of Manuelito and Defiance lie along the rail of pill.on and ,iuniper (Pmus ed11/is andJtmiper11s monospcrma), of .Manuelito quadrangle, surrounding quadrangles, and major drill holes located immediately north and northeast of the crops of the modern distrihnticm of the unit in New Mexirn. rood tr;icks, ;ind thf' Wf'stern edge of the' community of geologic and geographic features. quadrangle. The Torriv10 anlldine trends N20°W across the. lex/ cr;nti11ued u11 l,.;d<. 4uadrangle---{Jne in sec. 3 and one in sec. 19 of T15N R19\V. Upper Cretaceous rocks Li th ology 5ralc Squ.;sh l:~gi e Nest Li tholog~ L.\BLE l-ML·<1sun.-J co.ti SL'Cl1ons Lil Ram.ih un1l of C,allup S,rndstone (Kgr) and in Creva ~se The d rill-hole data revealed significant thickening of the l fl) Ca nyon Ca ny,m C,inyon Formation (KLT); measured A.ugu.._t 191-l"i Chinle Formation in the subcrop, from 800 ft in the Jones Dakota- Mancos sequence Ranch School quadrangle (A nderson, 1989) to 1,650- 1,900 , Coal brd ft in this area, within a d istance of 15 mi. Condon (1986) The Upper Cretaceous section is composed of shoreface 1 Location Str,1tigr,1phic po~ition th ickncss 1ft) reported a thickness of 1, 69.:i ft in the Hunters Point quad and ncarshorc sandstone, c<.mstal-plain mudstunt:' and flu £· .... ·· .. Kgt R.imah unit of Gallup Sandstone rangle adjacent to the north,.,,est. This rale ol southward vidl-channrl sandstones, and offshore mudstone and shale ,. Tl.JJ\." R2ilW NE' i-1r\E 1.: _, sec 33 Kgr: ..\0 ft ,1hovc• base 2. , thinning, ilpproximately 60 ft per mile, is local and is due deposited along tl1e v,-estern margin of the interior sedway. j c of sw·, ,:, ~ec 44 dhOVl" b.isl· to both pre-Chinle topog-raphy ,mJ pPrhc1ps some post f 2 IS Kgr: it 3.5 The shorelint:' for :he most part trended northwest but ·was with 1. S·ft rider Triassic northward lilting coupled with pre-Zuni bf..'velin)c;:. highly embayt:'d. The Dakota Sandstone (Kd) forms tht~ hc1sf' ] ll tt ,ih1.1ve The former is thought tu be the major factor in the pro· of the Upper Cretaceous st:'ctiun in we~tern Ne1-v Mexico. SW1.',NF11, ,,-., IS Kp, "i ll ft ,,buve b<1se 13 gressive southi,..ard onlap of younger members of the Chtnle 3 Excelll:'nt exposures of th" D;:,kota mc1y be found 1n sers. 1 onto the flanks of the ancestral Mogollon highland. The 29, 3U, 31, and 32 T14N R20W in the southwest corner of i\"W /1NV>,''/1 sec 13 Kgr, IO tt aboH ba~t:' I 2 1 t,I} Owl Ro<:k Mcmbl:'r of the Chinle pinches out sOuthward ;it the Manuelito quadrangle. A chert- and quartzite-pebble '5 SE' i-,S L: .: , ~"c Ill Kp: ft ,1bu1,1.; b.i~i· 1.3 .\!E 1 approximately the latitude of Mrnuelito- Furt \Vingate conglomeratic sandstont' -1- ft thick form s th(' bas;il part Jnd i1x, .~l ll d ,1,.,,,_ .11 ,I '·' ' " ''"" " .' I ,d,,, ,,, 1-11,n ,.,I 6 11SE ': -1 sec 5 Kgr, 40 ft dbnvt' base I I (35°25'). The youngest member, the Rock Point, pinches· out rests uncontormc1bly on the finer-grained Zum S,mdslone. 7 Tl.'iN IGO\\· SW ':' ,S\\'1.' -1 ~cc 1' Kgr, 40 ft below top 2 I in the subsurfa(e just south of Atarque; it is not prf'sf'nt in 5E 1 1aSF 1:, SPC 3(1 Relief on the unconformity approaches 20 ft, but locally a ----·,:.:_::__:_·:_ 6 Kgr; 40 it bdnw top 2.5 Carrizo Wash at latitude 34°3U'. rht:'se units appear to be paludal shale \Vilh carbonc1ceous zones is present .1 t th e basr Crevasse Canyon Formation conformable but prubably are unconformable on a r"gion;il of the LJakota dnd g:rades upward into sandstone. This basal T !J.\J I< ! 9\.-\' s w 1.: , s vv 1_, 1 sL'c l::!O ft above ba se 1.5 scale. fluvial and paludJl unit is as murh as 45 ft thick, ;ind it 6 Kee: 100 L311 2 \JF 1/.,S\\" '\ St' <' . Kc..:. llXJ-120 tt abuvL' b,ist.' 2.5 rnmmonly forms a darker-colored bold cliff at th " top of PunH·.. ,rnLL " t ,- the massive, highly sculptured Zuni Sandstone. 3 Sl::: 'i,N\\.":., , ::;e c '6 Kn-, ]2(1 ft dbmT ]M~l' - ••""! S,, ~,1--c ,,,,,. , nd ,.11 ; , h,•I.· m,,,,t:...,Jd,•,.I I, J ,. Tl4N l{J9W SVV ' ..'_,Nl:; 'i., sec 19 Kee llU ft above h,1SL' 1.2 Ovl'rlying this diff.forming basal sandstone ls predom· } . . · ;;•. •rn ,,l·ldl ,c'•ll"<'"''' inantly sh<1le ,ind mudstone unit that !ocallv is as much as ,_ 5 rl4N R20W NE'/1NE 1:·-1 ~l"L . 12 Ker. 12\J- 140 It Jbo\"E' bas,2 1.h ,....o.c , ~ M,aJ,,,, ,. ., a nd ,hal,•. c,rb,>nae<•oLJ, , pala,l,l · O -o' ':!"" 53 ft thick. Generallv a fluvial-channel sandstone bed 5- 20 - - 4: 6. NW '/-1N ~.'/, sec 12 Kn-: 12U- 140 tt abovt· b<1~e 12 - ~":! .:. ...._.._ '0 <:--e ft thick can be toun"d ne:.u the middle of the unit. Several l1 g,,, n.1I # " '"" ~ ~'- ' } C,ecc•• , , .,,w,, cc .oc.L,.,,. e,ff., e-,.V ~:$' '.:(;I._. .C'.?_j carbonaceous zones arl' present in the mudstone, which ~ -,::: {:'- /4.,.,"'<;' '..;: t:,,._' top of the typical "tripartite" Dakota is a I= '"" "'" wa".;" bc·.ld1r,L ·.,11h tl,,"'", l,,1;• " ,,,,I - "" A subsurface t:'xploration program tu determine or delin O\~t-'Jl. D. F. ., 1966 . .'fomt'nclature of Odkut,1 S,m cbtont' (Cwta· ~C m thinly bedded, fine-grt11ned s<1ndstonl' sequence inter ';1 ltc· m u:t>to~,·- ; ,,ndy sh, le '" "'~"'"" ,•, I,,. ;". · ', .i: .,,. - ~,>. ,nil l b,\,c" ·'. c',,rb.1~ r,1d,ni,. "r mh> rc•,trnted eatl' additional coal resources might concentrate l\n the syn Lt'(J us ) i11 Sa 11 Juan Ba~m. New Mex1n1 anologists, H11lletin . \". 50, no 5, pp }} ::::;:::;;:::::::::·., ;::;,:'.:;,::::;.,;: ~:. the conn·pt that initiiil mm't'mt'nt on sumtc uf these struc 1021-102t,; orange, quartzose sandstone. Wave-oscillation ripple marks --:z___ 1~ } ., , '" 1'· l,,f, """ ''1 -1,da l 11..1, 0 ~· ·. P1riringos, C N .. and O'Sullivan . K. ll ., 1978. Principal unron· C 'l 0 tures m,1y have- been ~)rc-Laramicle (Stricker and Anderson, ~ ~ 0 are abundant and commonly trend N40"'-SS ·W (as in N\·V R,·~rcs,"e , h ,•rt•e, .,,. ·w" s.rnd,cc•rLe , n<' arcc1. ' 0 found in the area. Small-diameter burrow casts also identifv pp 3 this interval. An 8-fHhick sandv shale and siltv sc1ndstonl' \ '<'ti' fi,,c, gramc•j •.ind,t,me ·.,·,,n ,,nd fl .a,ec Six measured coal sections from outcrop localities uf the Rl'.iga n, A. B. , 1924. Strcttigraphy of the J !opi Huttcs rnlcank fkld. t-,,ddmg. la~,.,n.,J-1'd.1J fi,,1 , Crevasse Canyon Formation are given in Table I Using .'.=: bl:'d overlies the 1;uartzose sandstone and probably rt:'pre ½ill""'"' iln.i ,an~v •ilhlo>n,·. ,.,.,,· l"-'dd,n~ Arizo n,1 . Pan·Arnenc,111 Geologist. v. 41 , pp. 155-366 > C } ~ ·c sents a minor transgression of the seaway. It is · in turn sanJy ,h,, lc; rt'slriw Mexiu1 Arneric,rn Associatirn1 of Pt'trolt'um Cco!ugisls, ()Lillelin , v 38, no . 8. pp . 1821 1826 stone that represents a regression of the seaway. It cont,iins ( h,m1i<'l sar\d,t,, r,c ~Hri~'.it.m·. mt ,,.,,11, 11 Tl3N R19W where two control points exist 0.5 mi apart. } :,·1tu r~s anJ laler,11 JCC rt'tl\'11 ,et, -2 \ B rr ' ' l"hc cakulations result in a measured resource (rna.J \Vithin Ke~,enning, C. A., Lancl.', I. F. , and Irwin. J. H. , 1'68. ·rerti My :: scattered burrow casts, including Ophwnwrpha, kKally has f,,,. .. ~,' """'d ,and,t,,r,e an.I " II) shak, I.am strM1graph y o! the '.\lc1\,1jo onmtry: New /\-kx1co G,-.olog,ral St'· 0 well·dPwlopcd hummocky crossbeds. and is fossiliferous f',,iu,h, I sh,1k (cart. , I ~''"" " "''- h,,,,ch ,,,_.,,,1,..,, ,.. alba•,·, ontcrch,tr, 0.25-mi radius of the control pomt, Wood ct <1l., 1983) in ·cc..: ·:. X , l>1n ,H·c be) 1111 ,\! le1p uety. C.rnJ,-.h!,ok to 9th Field Conferenct:, pp. 123-129 '"C -;j in the upper few feet. The fossils are dominated by the } sec 6 of 547,000 tons and .in indicated resmucl:' (coal within C '" tl f ~ , ,1, ct ,1 n,' anj ,·,,r,-• f,,w ~rain,-..J sa11J,t,,n,' t1 Jal Sears, ). 0 ., Jl)25 . Ccnlogy Jnd coal resourct's of thP G,1lh1p-Z11n1 ,i E - ovskr 1-:xogyra !1?1,is. and this sandstonl:' may bl:' thl' Jgl' the 0.25-mi-Ll.75-m, band ,,round the control point) of 3.1 1.-1.lsin, Nt>w Mexico· US. Geological Survey, lfollel111 767, 53 Pf.'· rn h~ressiv,• , l, unciose• •.. rn,l•u" "\ c ~} ~::.:-~~::·:.:-:::::::.,.,1 ..,,,,.J,1.,n e la~,~o nal i1ll million tons. In the absence of ex tensive coal-quality datu, -0 ..·: \ <'quivalent of the Paguate Tongue o( the Dakota. McgMip u;n,·,.,d Shomaker, J W, l:le.:iumont, E. C., ,md Kuttlowsk1, F. E.. 1971, C -fr fr ( "''I. 1~ u1,ho' S 1p,1 l,.,l.\l, a factor of 1750 tons per acre feet wa s usC" d in the calculc1- "' ples in il massivC'ly bedded part of this sandstone were f!,'>;J<'SSl>C sh,,r,' racc ,;a ,,dst,,~c wacsen1n~ Stripp<1bk low-sulfur roal resolHCc"S of the San Juan Bc1:;in in \ \:w c./)"' identified Ill the SV•,' 1/4Nf-: 1/,. SC( 29 ;ind in the et'ntrJI part fr ~ "''""J tions, An exploration program Lo further establish cod] re· Mexico d11d Culu raJo: New t\kxi rn Hurf'au of :\.1rnrs .ind Mineral : :: > '>c===<--• - ----~----'=~=-c< Rt•snurces. Memoir 25. 189 pp Cl. of the SE 1/1 sec. 29 Tl4N R20W. Widely scattered specimens sources in this stratigraphic interval would best be ca rried :: 7=~=7 l f- - - } "·""" "'"' out in the adjact:'nt Twin Buttes quadrangle (Millgate, in Strickn, G 11 , ,rnd Andrrson, 0 J., 1985. ['rt:·Lar.i1rndr led,rn· ~ of[. lcvis are present also at the megaripple locality. - ics--possLble control ,111 locu~ of Tu ronian-Corn.inan para lie .:oa I rn The tripartite Dakota Sandstone appears to be the hom press), where the coal Jil:'s a little Jeept:'r in the subcrop and c.) "'Cl. .-.. :. ,\ straddles the extension of the synclinal axis shmvn on the basin ~, west-central New Ml'xicu (a bs . J: /\merican ,\ssonatlCln ,if fracturv davs of Arizona and New r.-kxico three formations. They are, in ascending order, the Mesa Limited coal-quality work was undertaken for the Man· U.S . IJurt.cau of />.·lines, unPubl,~lwJ rq,ort. :l hpl.m.111,m C E"' uPlito quadrangle. At the New Ml'xirn Bureau of Mines and ,,., 0 I Rica SandstonC', the Pajarito Shale, and the Ronwroville Wood, G. 11., Kt'hn, T. .\1 ., Carter, M U., .ind Culbertson, VV . C. , 0) .'! Mineral Resources Jnalyses (co urtesy ol Fr,rnk W. Camp· 1983. Co,,J reso urce d;i~~1f1catmn sy,tt'm oi the L'.5 (;eologKaJ :l C ' Sandstone. In eastern and northeastern New Mexico the u 0 Ml'S.l Rica rnntaim a marine fauna (Kues et al. , 1985), v11hereas bell) of sJmplf' nos. 1 and _:; oi iht> locat ions in th,, Crevasse Survey ll.S Geologic,il Surn:y. Circul.u 891 , 6'i pp. 0 ~ ···i\{ 0) in the Manuelito area the basal Dakota is nonmarine. Cmyon Formation (Table 1) indicated coal of relatively good u "0) -.... ~ Cros,i;eddc·d ,and, tone C",,] c,nl•,,11. u·,,, quality. Sample 5 was slightly highl'r in overall quality; hllW· Overlying the marine Dakota with a sharp basal contact is the Whitewater Arruyu Tont-,•1.u, of the t-.fancos Shale (Kmru). ever, bolh were low ash (5-7%), lovv sulfur (0.38-0.43%) "0) u - .... Owen (1966) descnbed it as a v,ell defmed, persistent tongue roals with BTU values of 9700- 9800 on a moist, mineral· '- u 0) of marine shule sepilrating the Twowells Tongue from the matler·free basis. Most of the sulfur (711' 1/r, ) is 1n organic form 0.. FIGURE J-Measured sections 01· G,11lup Sandc..tone at Squct~h Canyon (NE 'i,tiE' /, sec. 34 Tt4N R20W) ,mJ ;it Eagle N~~l Cmyon (SW -'-1SE '":: rest of the Dakota S;:,ndstone in the southwestern pJTt of as opposed to FeS or SO,; moisture con tent is in the range 0.. 2' ec '/, sec. 2 TlJN R20\.V), approx1m.itely 2 m1 <1p<1rt along a line p,1r,,llc"I to d,op1}Slti11nal strikl' of 6-7%. :J C the San Ju,m Basin. In the M.:mudito qu.idr.:mgle it consists nf 20- 40 ft nf gray to dilrk·grily mt1rint..' shJll' \Vith thin, An additional coal sample collected in sec. 29 T 14N R19\V .c"' ,2 0 Cf) .,,.0 orange·weathf'ring benlonite beds. Selenite shet:'ts com just east of thp quildr.ingle boundc1ry in tht' Twin Buttt:'s ~ 0 quadrangle indicated much higher ash contents (28';~) and 0 -0 I monly mark the b'entnnitc beds. This shale is restricted to u 0 isolated outcrops in secs. 20, 29, and 33 T14N R20\V and Th e entire lower 205 ft of section represent deposition Crevasse Canyon Form ation lower BTU va lues (7360) C U) -;;;"' C'l Cf) secs. 4 and IO Tl3N R20\"V. and ilccumulntion along a segment of the cmst that was "' Named by All en and Balk (1954) for exposures in the Petroleum and natural gas ::e: C The \r\'hitewater Arroyo Tongue represents deposition in subject to repealed minor oscillations of the shorL"l inl'. Somt:' T(ihatchi quadrangle 20 mi to the north, the Crevasse Can a deeper-water, open-marine environment beyond the tran of the sandstones in the section are "doublets" and may i:2 yon Fom1ation (Kee) ovcrlit:'s tht:' Torrivio tv1embt:'r of the No oil or gas shows were reported from a test drilled in sition zone. Shale deposition was interrupted near the end have transgrf'ssive nnd regressive components. The sand 1 Gallup Sandstone. It is a mostly nonmarine unit (entirely th!:" S\·\/ /4 sec. 5 T14N Rl9\V in the northeast corner of thf' of Cenomanian time by the progradation of a shl'lf sand· stones are generally burrowed, including Ophi11111or11/ra, and nonmarine in the Zuni Basin) composed of shale, mud map. The hole was dnllcd in 1926 by Marian Oil Company Rr'IL1f,f' Cn•Pk I ,m<>· stone- the Twowells Tongue of the Dakota Sandstone {Kdt) . bioturbated (Fig. 3). Ripple marks ,1rt' rommon, and withm ~tonl' b,.•ds (nut,,,. stone, lenticular fluvia l-channd sandstones, and minor coal of Colorado to a T.D. of 1,390 ft. Two other tests in the ,-. Tht:' Two\vells overlies the Whitewater Arroyo Tonguf' \vith the fl.asN -bedded, ripple-bedded, lc1goon.al-tid,d-flat se poscdJ and carbonaceous mudstone. The distribution, morphol vicinity reached Precambrian basement rock ,1ftN pcnc a bilse gradational from silty shale to silty, fine-grained quences, considerable variiltion in trend c,m be found. This ogy, and grain size of the sandstone bodies, as well as the tratmg more than 6,000 ft of sedimentarv rock. One ,va<: sandstone throu1c•;"1 an int('r\'Jl of 10 ft. Abow this arf' 25 ft -0 m .. diversity in ripple-mark trend perhaps reflects the oval fact that tht:'y are encast:'d in the fine-grained sediments of drilled in 1954 in the SE',/4 sec. .1 Tl5N R 1,jw, J nd the other N } of generally flaf-bedded, upv,,ard-rnarsening quartzose elongale configuration of the lagoon ilnd contrasts with the C " thf' flood bJ.sin or b;ickswamp, sugge.st that there was an was drilled in 1967 in the Sf1.i4 sec 19 TI SI\' Rl9'v\/, U.7 mi .'! " sandstone; primary bedding feiltures hnvc been destroyed more uniform trends found in the shoreface--barrier-beach "E E 0 abrupt return to c1 meandering fluv1al system following dep north of the q1rndranglc- boundary. A dnll-stem test v,,as run C ' ... bv bioturbation in the lmver third ur lower half; however, t'IWironment. which are generally northwest ,rnd west. The osition of the Tomvio braid plam. The mudstones and sand in the sec. I9 hole but not in Lhe sl:'c. 3 lest. Neither reporh'd " sOme planar and trough crussbedding with south and sequences accumulated near a pivotal poinl Jlong th e re "' " ·,,:._;;- stone:; forming this se4uence are el1uivalent to the Dileo an oil show. § southeast dip directions are preserved in the upper beds of gressing shoreline, which swung sharply east",·ard to the > I Coal Member and Bartlett Barren Membt:'r, \Vhich are the C "' " 0 lower-med1um-graint:'d sandstone. Also, in the upper bt:'ds south of Manuelito quadrangle; southward tiw 'Ires Hl:'r -0 .ii N subdivisions used farther east where the formation is thicker Clay u'" -"' c ~ I are numerous burrows, including Ophiomorplia. Ripple-lam manos regressive-transgressive wedge was deposiled. At C Dips ,ire gently northeastv11arJ 2"-4'". Jn20, which was suitabl!! fur use mation) jusl above slream level on the west side of the mesa \ nt the bc1se of the overlying tongue of the Mancos Shale is ment that developed following withdrawal of the Gallup in the manufacture nf rommon brick, low-duty refractories, (SW 1/4NE 1/4 sec. 19 T14N R19W} No coal beds thicker than and mortar. · a light-colored fossiliferous bed contilining the oyster 11_1/(· seaway. The Cllill, howl'ver, is highly lenticular. The thickest Zorn:~ l,kdt to econ· 3 inches were found in the overlying 300 ft of section. Co<1 l nodo,i/e kellumi and forms transitional between P. kdlumi and coal bed in the unit is 46 ft above the base of the Ramah The strntigraphic interval that yields refractory clays in lain reddish-brown, also was noted in outcrop in the W 1h sec. 6 Tl3N R19W in the younger P. newberry1. P. m'u.:bc:-ry i commonly is present unit in the central part of the quadrangle in the SW 1/4 sec. the Gallup vicinity, the lower part of the Crevasse Canyon fine-grained inter- thl' southeast corner of the quadrangle. A maximum thick dun~l dt>posit~ !orally in or just below bl'ds of the Bridge Creek Limestone in west 15 Tl5N R20W. This bed is 3.5 ft thick but cannot be trared Formation, is present in the Manuelito quadrangle. Non ness of 2.5 ft was recorded for the lower of t\'-'O co<1l beds cenlrnl New Me:xi:o (Hook and Cobban, 1977). Beds of the laterally at that thickness. One half mile to the northeast mnrine wal-bearing sections, such as the Crevasse Canyon, u in tlw basal 120 ft of the Crt'Vilsse Canyon Formation in sec Bridge Creek Limestone were identified approximately 40 its thickness has decreased to 15 inches. It does not app('ilr are a natural l'rl\'ironml'nt for rdractory (high kaolin) days ·CJ)- C 6. Coal resources in this unit and in the Gallup Sandstone CJ) '" because the low-pH environment associated with the for ~ ft abm'e the top ol the Twov·.:ells Tongue m the Jones Ranch in the carbonaceous Lone at this stratigraphic intt:'rval to u 0 - .lrc discussed in a following section. mation of the peat S\vamps illso promoted J1cc1<.hing of thl' .... ~ 0 School quadrc1ngle immediately to the south (Anderson, the northwest in secs. 8 and 9, but coaly beds and a thin CJ) "' - 0 fine-grained, mineral detritus, leading lo kaolinite as the :l -0 .. . 1989), but they cannot be identifit.·d in outcrop in this qu,1d coal are prewnt in this interval J mi hl the south at the C Tertiary end product. "' rn "0 rangle. Pieces of tabular limestone containing inoceramid Squash Canyon measured section (Fig. 3). Locally, fluvial· .., 0) c./) " - ,:.~--.:..=or-~ !/ debris may be found as float above the fossiliferous bed at rh,mnel sandstones dominate the Ramah unit lithologies, An upper Tertiary (PliOCl'ne?) sedimentary unit uncon :l -Cl. REFERENCES ~ "O C :: the sec. 20 locality just described, ilnd these arc assumed each of which may be as much as 30 ft thick. ln the upper formably overlies the Crevasse Canyon Formation. [tis pre "O :: to be weathering out of a Bridge Creek interval, w hich here part of the unit the fluv1al -channel sandstones commonly served on!y on the higher surfaces in the extreme southeast N ~;-~~-\·:~ Allen, J. I:::., and Balk, R. , "19.54, Mineral resounes of Furl Defiance ·-::;;: : • .-:•. 1 is covered by colbvium. The significance of the limestone contain coarse-grained lenses, These upper Ramah sand corner of th e qundrangk bul beromes much more wide and TOhatchi quadranglt>s, Arizona and \Jew Me.,ico: :-Je1v Mex· ...... :1 is that it marks ll1c time of milximum trunsgrcssion of the stones resemble the sandstone of the ovt:'rlying Torrivio spread westward inlo Arizona. Named the Bidahochi For· irn Bureau of Mines and Mineral Resources, nul l,o tin 36, 192 pp. .:1 western interior sraway during the Grt:'enhorn cycle of sedi Member; howf'ver, Lhey do not become a& n)ars·e grained mation (T/111) by Rl'agan (1924) for exposures n"ar the village Anderson, 0 . J., 198J, Prl'limiHMY rcpurt un reddimtum of Zuni .. mentation, an early Turonian event (Hook and Cobbiln, or as thick, nnr hilvc they dl'veloped the deep reddish ol the same name, it was subsequenlly divided into three Sand~tc>ne, west-rentral New Mexico. New Mexico Geology, v ·:::. .·.·:.1 1977). . .:.- _: I brown oxidized colors of the Torriv10. A persistent 1U- tu members by Repenning and Irwin (1954). The three mem 5, no. 3, pp. 56-59 Overlying the fossiliferous bed at the top of the TwO\vells 20-ft-thick, slightly Ci"irbonaceous, locally coaly mudstone bers Wf're designiltcd: (!) thf' lower memb{'r, dominated by Anderson, 0. /., 1987, Geology and coal resources of Al.irque Lake : I 1:50,(X)(l quadrangle, New Mex1u 1: New Mexin1 llurt:'atJ of Mines . ·._ : : I Tongue is a 350-40J.ft-thick, grc1y milrine shille thilt is slightly forms the uppermost pilrt of the l~amah unit; this may have m udstone and sandstone with some lacustrine facies; (2) calcareous throughout the lovver half. The sharp basal con served as an aquatard or aquafuge and restricted the down the volcanic member composed of basalt and basaltic lapilli and Mineral Resources, Geologic Map 6L :.i Anderson, 0. L 1989, Geology ctnd minerill resourc,os of Jones tact suggests a rapid return to deep-water, open-marine vvard movement of the oxidizing water within the Torrivio. tuff from 2 to 50 ft thick; and (3) the fluviallv dominated Rilnch School quadrangle, McK.inlcv Countv, New Mex ico. New ·1 conditions following deposition of the Tvvmvells Tongue of At the top of the Torrivio anticline (topographically the upper member, c1pproximatcly 270 ft thick. The Zuni Basin ·1 Mexico Bure.tu of Mines and '.\1i11ef;il Re:;ollrn!s, Geologic Map the Dakota Sand~tunt:' . The sudden transgression app.ir feature is known as Torrivio Mesa) in the northeast corner section has been assigned to the upper member by most 65, scale 1:24,000. ·, ently was triggered by a eustatic rise in sea level and rep of the quadrangle only on e fluvial-channel sc1ndstone is authors, induding Rept:'nning et al. (1958). Anderson, 0. J., 1990, Gt>ology and coal resottrccs of Vanderwagen . :::.1 < ... resents a major and fin.JI pulse during the Greenhorn cycle present in the Ramah unit. It is c1pproximately 45 ft above Tht:' Bidahochi Formation rt'mnants in the Manuelito quadrangle, McKinley C1Ju11ty, New Mexico· New Mexico Burt>au .... :. . ··." I of sedimentation. The name Rio Salado Tongue of the Man the marine Gallup and replaces Lhe carbonaceous zone con· quadrangle consist at moderately reddish brown to li ght of Mlnes and Mineral Resomccs, Geologic M.:ip 64, ~ca] ,, 1 .24,000 cos Shale (Kmr; Hook et al., 1983) is used for this shale taining the thickest coal. This sandstone, which is from 15 brown, poorly indurated, argillaceous sandstone, with local Anderson, 0 J , and Stncker, G. D. . 1984. Stratigr,1phy and coJI occurrences of Tres Herm.inos formation am! C,1llup SanJstonP FIGURE 2- Composite stral!graphic column for Tt>rtiary and older tongue even though here the upper boundary is funned by lo 35 ft thick, is somewhat unusual in that it contains coarse· interbeds of grnyish-orange--pink (5YR 7/2), poorly sorted the Gallup Sandstone, not the Tres Hermanos Formation grain ed facies and large-diameter burrows; evidence of bur· and "banded," carbonate-cemented sandstone. The color, {Upper Crl'tau:ous), Zurn Hasm , west·centr;il .'.."ew />.texico; in rocks. Houghton, R. L., and CL,rn~cn, E. M. (eds.), SympClsi um on as is the case in the type area. The basal Gallup Sandstone rowing is not commonly seen in fluvial sa ndstones of this texture, and lithology of the Hidahochi indicate thcit the geology of Rocky Mo1111tain coal: North Dakota Ccologica! S.,1· in this part of the Zuni l3asin is stratigraphically contiguous area, The coarse-grained facies apparenlly represent early major sources of these sediments were the Permian and cicty, Publication 84-1, pp. I 15-J25 with but slightly younger than basal Tres Hermanos, thus pulses of the type of sediments that characterize the owr Triassic rocks of the Zuni uplift 14 mi to the easl with lesser Condon, S. M., 19t:\6, Geologic map of the llunters Point quad· Jurassic rocks the name Rio Salado can be applied to the underlying tongue lying "forrivio Member. A carbonaceous zone appe,JrS above amounts providt:'d by the Jurassic and Cretaceous section. rangle, Ap;iche County, Arizona, and McKinley County, New the sandstone and contains a 10-inch-thick coal bed, but Reworked Cretaceous molluscs can be found locallv in the The oldest rocks exposed in the quadrilngle c1 re those of of the Mancos Shale. In this usage Rio Salado is locally Mexico: U.S. Geulugkal Survey. Geologic Quadrangle Map GQ- equivalt:'nt to the lower Mancos Shale. this outcrop, as well as those of the overlying Torrivio Mem BidahoChi (Anderson, 1990). Good exposures of the Bida 1588, scale 1:24,000 the Zuni Sandstone (Jz), which rests unconiormably on the Exposures of the Rio Salado Tongue are limited bt- ca use ber, is just off the eastern edge of the qu.Jdrangle in sec 5 1 Condon, S. M., ,md Huffman, A. C. . t984 , Stratigr;iphy .1n d dep· Chinle Formation in the subsurface. As defined bv Ander hochi arc present in the N~\1 /4 sec. 32 Tl4N lU9W, where it is ,1 slope-forming unit and genernlly covered. However, T14N R19W. The entire Ramah unit here has thinned to 94 erosional remnants attain il maximum thickness of just over ositional environmc11ts of Jurassw rorks, Sa n Ju;in Basin, New son (1983), the Zuni consists of the undivided eqllivaknts the cJlcareous aspect of the shale is lost somewhere near ft. This is rnnsis~ent with gf'nN.:il Ci'!Stward thinning: ob 40 ft. Mexim, with emphasis on the so uth and 1vest sides; 111 Brew, D of th1c Entrnda Sandstone ilnd the you nger Cow Springs C. (ed.), P~lcotedonics--San Juan Mount~ins--Dolores Forma the middle, and the upper part becomes il darkcr-grny, non st:' rved in the unit c1nd i'!pparently is not due to any pre Sandstone (Middle Jurassic), from the Manuelito area tion-paleosols and depositional syslem~Jur.tssic deposi tiun,d calcareous sequence. The thin, fossiliferous sandstone beds Laramide growth of the anticline, southward the two units become practically indistinguish MINERAL RESOURCES system-San Ju<1n 13asin-Qua!ernary deposits and soils--Dur· within the upper 100 ft of this noncalcareous shale, ,vh ich The base of the overlying Torrivio Member (Kgt) is sharp able whereas tu the north the p resence of tht' Todilto Lime ango area: Geolog1cal Soul'ty of Amcnca, Rocky Mountain Ser· were referred to informallv as the Tres Hermanos beds (An and, a t most localities, is a slightly scoured surface devel stone and l3edabito Member of the Wanakah formation tion, Guidebook to 1984 Field Conference, pp. 93-104 derson, 1990) iminl:'diatl:'l)' to the southcilst in the \\:indcr oped on carbonacrous mudstone (.Fig. 3). The Torrivio, named Coal Darton, N. H., 1910, A reconnaissance of parts of northwestern divides them into two distinct and separate sandstones. The wagen quadrangle, are not well developed here. Those from exposures at Torrivio Mesa by Mol1::'naar (1973), is a New Mexico and northern Arizon.i: U.S . Gt'ologKal Survey, Hu l· Beclabito was formerly the Summerville .Formation. Coal resources (coal in beds >14 inches thick) arc present sandstone beds have yielded specimens of Col/igminiceras highly crosshcdded, medium tu very coarse grained, locally letin 435, fill pp. W'ithin the quadrangle, the t hickest outcrop is approxi in two stratigrnaar, C:. M , 1973. St>dimentarv f,1Lie~ ,m 14 inches thick) in this proximately 40-50 ft above the base of the Ramah 0.75 mi at that time there was no emphasis on specifying or rf'c the southern Colorado Plateau: Four Corners Gt:ologJC~l S0c1 t't _v, S) at the base of the Morrison Formation as described bv part of the Ga ll up Lnterat variability is great as is indicated tn the northeast of the quadrangle boundary in S<'C. 20 T 15N Memoir, pp. 85-110 ognizing genetic units. However, out in the basin to the Pipiringos and O'Sulliv,m (I978) is not in evidence in th"e by the two measured sections less than 2 mi apc1rt (Fig. 3). R19W of the Gallup West quadrangle. This was rcportPd JS Molt'na<1r, C. M., 1983 , Principal rc"ference ~ediun and correlation upper part of the unit mapped as the Zuni Sandstone in southwest, it is not logical to treat this sequence as a for the Myers mine by Se,irs (1925), who stated that it produced of Gallup Sambtonl', northwestern New Me>x1co; i11 Hook, S. C. mation-rank unit. this area. from two beds, each 2,5- 3.0 ft thick, separated by a shale (comp.), Contributions lo mid-Crctan:ou~ p<1ko11t(>iogy and stra· interbed that thickened westward. Production was before tigrnphy of Nt'w Vlexico, part Jl. New Mexirn Burl',1U of Mmes 1924 and was essentially the only local production from the and Mineral Resources. Circular IH~, pp. 29- 40. Gallup Sandstone,