Late Cretaceous and Tertiary Stratigraphy of the Raon Basin of New Mexico and Colorado Ross B

Home , Cuchara Formation, Pierre Shale, Poison Canyon Formation, Raton Basin, Raton Formation, Raton Mesa

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Late Cretaceous and Tertiary stratigraphy of the Raon Basin of New Mexico and Colorado Ross B. Johnson, G. H. Dixon, and A. A. Wanek, 1956, pp. 122-133 in: Southeastern Sangre de Cristo Mountains, Rosenweig, A.; [ed.], New Mexico Geological Society 7th Annual Fall Field Conference Guidebook, 151 p.

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LATE CRETACEOUS AND TERTIARY The Ratonbasin is asymmetric;the eastern limb dips STRATIGRAPHYOF THE RATON gentlywestward, whereas the westernlimb clips steeply BASIN OF NEW MEXICO AND COLORADO* eastward.Locally this western limb is verticalor over- turnedalong the basinmargin. Late Upper Cretaceous By and lowerand middleTertiary rocks occupy the deepest R. B. Johnson,G. H. Dixon,and A. A. Wonek partof the basinin the RatonMesa region and Huerfano U. S. GeologicalSurvey Park(fig. 1 ). The deepestpart of the troughis gener- allyparallel to butnot coincident with the structural ABSTRACT axisof thebasin. A thicksequence of lateUpper Cretaceous and Ter- tiarysedimentary rocks is preservedin theRaton basin. In 1948the GeologicalSurvey began a regionalinves- Thesestrata include the Pierre shale, Trinidad sand- tigationof thegeology and an evaluationof the fuel re- stone,and Vermejoformation of LateCretaceous age; sourcesof the RatonMesa region and HuerfanoPark in the Ratonformation of LateCretaceous and Paleacene Colorado.This investigation is still in progress,and re- age;the PoisonCanyon formation of Paleoceneage; portscovering most of the regionhave been released. the Cucharaand Huerfanoformations of Eoceneage; Reportspublished to dateby the GeologicalSurvey on theFarisita conglomerate of probable Oligocene age; theRaton Mesa region are given in thelist of referen- andthe DevilJsHole formation of probableMiocene cesthat concludes this paper. Investigation of the geo- age.Some of the eventsof Laramidedeformation are Iogyand fuelresources of theNew Mexicopart of the Ra- recordedin therocks of theseformations, ton Mesaregion was begunin the summerof 1955,and mostconclusions derived from work in thatarea are ten- LocallyLaramide deformation began with epeirogenic tative. movementswest of the Ratonbasin in lateMontana time. The epeirogenicmovements were followed by at least The RatonMesa region and HuerfanoPark contain the sevenorogenic episodes, as shownby angularunconform- mostcomplete stratigraphic succession of lateUpper itiesand lithologic changes in thesedimentary rocks. Cretaceousand Tertiary rocks that is exposedon the easternside of the SouthernRocky Mountains. This Sills,dikes, plugs, stocks, sole injections, and lacco- stratigraphicsuccession includes the followingforma- lithswere intruded into the sedimentary rocks of thebasin tions:the Pierre shale, the Trinidad sandstone, and the duringthe Eoceneepoch. Vermejoformation of LateCretaceous age; the Raton formationof LateCretaceous and Paleoceneage (Brown, INTRODUCTION 1943,p. 82-83);the PoisonCanyon formation of Pale- The Ratonbasin is an UpperCretaceous and Tertiary oceneage; the Cucharaand Huerfanoformations of Eocene sedimentaryand structural basin that lies in northeast- age;the Farisita conglomerate of probable Oligocene age; ern New Mexicoand southeasternColorado (fig. 1) andthe Devil’sHole formation of probableMiocene age. thewesternmost part of the GreatPlains province. The Onlythe Pierre shale, the Trinidad sandstone, and the Ver- basinis boundedon the westby thefoothills of the mejo,Raton, and PoisonCanyon formations are knownto Songrede CristoMountains and on theeast by the Sierra occurin the New Mexicopart of the RatonMesa region. Ccande-kasAnimas arch. It mergeswith faults and folds Preservedin the stratigraphicsuccession are the records in frontof theCimarron Mountains to the south.The nor- of severalpronounced episodes of the LaramideRevo- thempart of the Ratonbasin is dividedby a southward lution(fig. 2). plunginganticlinal extension of the Wet Mountains.The axisof thewestern or mainpart of thebasin is in Huer- GENERAL STRATIGRAPHY fanoPark end Wet MountainValley. The axisof the eastern or secondarybasin trends northeastward between the Cretaceousrocks The Pierreshale (Meek and Hayden,1862, p. 419,424) Wet Mountainsand the Las Animasarch and terminates to thenorth against the Apishapa arch. The principal is about1,600 feet thick in thesouthern part of theRaton Mesaregion in New Mexico,but reachesa thicknessof axisof the Ratonbasin in New Mexicotrends slightly about2,300 feet southeast of HuerfanoPark in Colorado. eastof north,but in Coloradoit hasa northwesttrend, Thelower 1,300 to 2,000feet of thePierre shale is chiefly darkgray to nearlyblack noncalcareous shale with sev- ¯ Publicationauthorized by theDirector, eralthin zones of calcareousand ironcarbonate concre- U. S. GeologicalSurvey. tions.The upper 200 to 300feet of thePierre consists of

122 Wet Mountain -WET

HUERFANO-- PARK /~

’ " ~Walsenburg ~ z @@

O ._~

i ~i~T)~i ~ I~COLO~ADO

’ " ~j~atH~tenl~.# - C~3F~ F/~T iN COLO. ~a.sao e7 PLAINS ~" O/ Eagle Nes~ / ~IL""h °Cimarror

LLJ INDEX .MAP j

EXPLANATION ///.~#

Area of outcrop of uppermost C/~/aLas Vegas /63" Cretaceous and lower and middle / Tertiaryformations. / //~c) + Axial trace of Raton basin

Fig.I. MAP OF THE STRUCTURAL RATON BASIN OF NEW MEXICO AND COLORADO

0 i0 20 30 40 50 Miles Scale I

AGE FORMATION ! THICKNESS i i I QUATERNARY ~ ""~’lluvium 0"~ 30" ~ F ~ ~ Unconformity Miocene(?) Devil’s Hole formotion 25’- 1,300’ , 1

-- I -- Unconformity

0’-I,200’ Oligocene(?) Forosito conglomerate 1

-- Unconformity~ I Huerfono formotion 0’- 2~000’

1 ~ Unconformity ~

Eocene I

TERTIARY i Cuchara formation 0’-3,000’ I i ~ Unconformity ~ I

%Z,300’ Poison Conyon formotion 0 " I Paleocene ~ Locol unconformity ~ I ~ Roton formation 0’-1,700’ 1 ’

VermeJo formotion 0’- 300’ i i 0’- 240’ Trinidad sondstone ! i

CRETACEOUS Upper Cretoceous

Pierre shole 1,600’- 2,300’

Fig.2.UPPER CRETACEOUS AND TERTIARY SEDIMENTARY FORMATIONS OF THE RATON MESA REGION AND HUERFANO PARK NEW MEXICO GEOLOGICAL SOCIETY * SEVENTH FIELD CONFERENCE

WSW ENE

Sandstone L~.~ SiJtstone ~ Shale ~Coal

Kv-Vermejoformation Kt-Trinidadsandstone Kp-Pierreshale

Fig.3. CONTACT RELATIONSHIPS OF VERMEJO FORMATION, TRINIDAD SANDSTONE, AND PIERRE SHALE BETWEEN CIMARRON AND DAWSON, NEW MEXICO.

buffto gray,thin-bedded, fine-grained sandstone inter- Thel ithologiesand stratigraphic relationships between calatedwith thin beds of grayto darkgray silty and san- thePierre shale and theTrinidad sandstone are similar to dy shale.These beds grade into and intertonguewith the thosereported for their homogenetic correlatives, the lowermostbeds of the overlyingTrinidad sandstone. Pierreshale and Fox Hillssandstone (Richardson, 1915, Tonguesof Pierreshale wedge out in a westerlydirec- p. 6) in areasnorth of the Ratonbasin; and theLewis tion,whereas tongues of the Trinidadsandstonewedge shaleand PicturedCliffs sandstone (Dane, 1948; Wood, outlaterally in northerlyand easterly directions (fig. 3). Kelley,and MacAIpin,1948; and Zapp,1949) of northwestern New Mexicoand southwesternColorado. The Trinidadsandstone (Hills, 1899; Lee, 1917, p. 48- 51~is composedof buffto gray,slightly arkosic sand- The Pierreshale accumulated as a thickmarine sequenc~ stonewith local thin interbeds of lighttan to graysilty of mud and siltwith minor amounts of limeand sandduring shale.The formationis 40 feetthick southeast of Trini- Montanatime (Eldridge, 1888, p. 93) throughoutmuch dad,Colorado and fromthis point northwestward it in- the areanow occupiedby the GreatPlains and the Rocky creasesin thicknessto 240 feeton the westernmargin of Mountains.The beginingof Laramidedeformation is re- the basinsouthwest of Walsenburg,Colorado (fig. 4). cordedin theupper 100 to 300feet of thePierre shale by Sandstonebeds are medium-to massive-beddedand the alternatingfine sandstone and shalebeds. Epeirogenic beddingstructure is mostcommonly tabular, less common- upliftforced thestrand line to retreatto thenortheast, and ly irregular,and in placeslenticular. The grainsare most- someof thefinesand eroded from the upliftedarea or areas ly quartzwith subordinate amounts of weatheredfeldspar, was depositedin the presentRaton basin. As the strand mica,and ferromagnesianminerals. The grainsize is lineshifted,the Trinidadsandstone,accumulated in the sea chieflyfine, but ranges from very fine to medium.Casts and on its marginsas regressivebeach and offshoredeposits of/]cdymenitessp. arelocally abundant. The regressionwas discontinuous,however, and the direction

125 ~’.~ "////~/~W .7"f~ ,~ ~ alsenburg

Co %

" ,," i / I I ....I...... ~ I/ ;/ .®.,..... ~, ¯ }

inidad ’~ -. \

-~J \ ,~ _- --".-

i -~\ ¯ 1 , COLORADO i. -5- % NEW MEXICO N t ¢ -.. ------,_...._~.,’

" " ~ "\ Rot°° \ - ii I " ,\ ~Von Houten

’ ’ .],"°~t

Limitof outcrop of Trinldad land~one

Ute Pyrk } IIopOehli¢~e nOCimorro

Fig.4. ISOPACHMAP OF THE TRINIDAD SANDSTONE IN THE RATON MESA REGION OF COLORADO AND NEW MEXICO " Ouro

",, "°’/ / ¯ guilor " ! I "ill"" ...... I I fX - ,~ . ¯ ~ ~ ~ \ "’-..’,,,, ’,, ,,, ",, .,, I "-.. -. ~ , ’,, ,, \ " ~’h~"-~. - ’’, ’, ", ~, ,~./ .. \, ’,, ,, :., I .’ [- ,, ..,," \ ’,, ,, , i .. . ..--- t-"-~ ~ 1 II ,-" . ~/./ ,,i / I ~ / . - ...... ~ >/ ,’ / } uth I" / } I ~- --J;----c%%>,, -’~-:~--" - ":3 b~ ""~i / ,’ " / .-- ,,. I, . .) ,,~ i;+o~& ~_.)..Io"’ ’,/", , ,"" ,"’ ;’/ /"" i’" ’" i / / , , / ~ z ¢ , / ~ ,/i ~(. /s d _z’ L //COLORADO’, -- .Z~Y-.,.,J----~_,,~.,’ .~ ~~ ~ex,co7 ,," ,.,’ ,,’ i ,: ,, / l ; ,’ ,. ,-" / h I ,,,\i Roton " \ % / I

~anHouten i / X /"" [ \ !,, ,, . ; ~-~ ’,,..,’i,, , ,’ ,, > \". ; , ~/e;~ ¢ .~’~ i+% i ,’ \ ..... ,, +, ~, # /~-" Isopochlnlervol=~O feel ; ; ~.~, Limitof o ¯ f Trlnla ~n~llon~ ~ o ! U’tePork( i / -,"~--~-/’:;1~.... / IlopQIlhIin~l / (Deehedwile,’e u/Ice.#i#) o Cimorron ,~

Fig5. ISOPACH MAP OF THE VERMEJO FORMATION IN THE RATON MESA REGION OF COLORADO AND NEW MEXICO NEW MEXICO GEOLOGICAL SOCIETY * SEVENTH FIELD CONFERENCE

of movementof the strandline was occasionallyreversed, theRaton formation is madeup of buff,gray, and olive- grayvery fine- to course-grainedarkose, graywacke, and The Vermejoformation (Lee, 1913, p. 531)of Montana quartzosesandstone beds; grey to darkgray siltstone and and Laramieage restsconformably on the Trinidadsand- siltyshale beds, and numerouscoal beds. The feldspar stoneover most of the RatonMesa region. Tongues of grainsin the arkoseandsandstone beds are usuallyweath- Vermejo~trata wedge out in easterlyand northeasterly ered,and are generally white or lightgray. directions,and tonguesof Trinidadsandstone wedge out to the westand southwest.Vermejo rocks consist of buff, In thecentral part of theRaton Mesa region the upper- gray,and dark gray siltstone; buff, gray and gray-green mastbeds of the Ratonformation regionally intertongue slightlyarkosic sandstone; nearly black carbonaceous, withand locally grade vertically and laterally into the coaly,and siltyshale; and numerouscoal beds. Sand- lowermostbeds of the PoisonCanyon formation (Hills, stonebeds vary from thin- to massive-bedded. The thin 1888,p. 148-164}.At most placesthe contactbetween sandstonebeds are chiefly parallel-stratified, butthe thetwo formations is difficult to placebecause of thegrad- thickbeds of sandstoneare commonlyirregular and lentic- ual lithologicchange between them. Usually the contact ular.Sand grains are principally quartz, but weathered may be locatedby the appearenceof unweatheredgrains of feldspar,mica, and ferromagnesianminerals occur. The pinkfeldspar in the sandstonebeds of the PoisonCanyon. grainsize varies from very fine to medium,and the cement- The sandstonebeds of the PoisonCanyon formation are ing materialsare clayand calciumcarbonate. Coal beds usuallycoarser grained than those of theRaton formation. areintercalated in shale and siltstone units which vary in In addition,the shalebeds in thePoison Canyon formation thicknessthroughout the RatonMesa region, containlesser quantities of carbonaceousmaterial, and coalis presentat onlya fewplaces near the base. Fifty The Vermejoformation is apparentlyabsent a few miles to 100 feetabove the contactbetween the PoisonCanyon eastof Raton,New Mexico,and severalmiles southeast of formationand the Ratonformation, the PoisonCanyon is Trinidad,Colorado (fig. 5), and is onlya fewfeet thick characterizedby massive buff to red arkosicsandstone the mouthof CrowCreek Canyon near Koehler, New Mexico. and conglomeratebeds and thin yellowshalebeds.The Fromnear these points the formationincreases irregularly PoisonCanyon formation ranges from a thinedge in in thicknessnorthwestward to 500 feetsouthwest of HuerfanoPark to about2,500 feet in thicknesssouth of Walsenburg,Colorado. the SpanishPeaks.

lee(1917, p. 64) believedthat the rocksof the Vermejo The upperbeds of the Ratonformation intertongue and formationin the westernpart of the RatonMesa region were gradeinto the lowerbeds of the PoisonCanyon formation removedby widespreadpost-Cretaceous erosion. However, in southerlyand westerly directions (fig. 6). On thewest- duringrecent investigations no evidence has been found of ternmargin of the RatonMesa region near the New Mexico- a regionalunconformity between the rocks of theVermejo Coloradoboundary, beds of the PoisonCanyon are several formationand the rocksof theoverlying Raton formation, hundredfeet below the stratigraphic position they occupy Reconnaissanceexamination of the areaeast of Raton,New in thecentral part of the RatonMesa region. Farther to the Mexico,and Trinidad, Colorado, indicates that the eastwardsoutha few milesnorthwest of Cimarron,New Mexico,the thinningof theVermeio formation is morelikely due to rocksdescribed by Lee (1917,p. 72-74)as beingin the nondepasitionthan to pre-Ratonerosion. Ratonformation have l ithologiescharacteristic of the PoisonCanyon formation. It is believedby the writersthat Followingthe depositionof the offshoreand beachsands in thislocality the Poison Canyon facies is dominantover thatcomprise themrinidad sandstone, the sea continuedto the Ratonfacies. In the vicinityof UtePark, NewMexico, retreat,and mud, silt, sand, and carbonaceousmaterial of rockswith lithologic characteristics of the Poison Canyon the Vermejoformation were deposited on deltas,flood restunconformably upon rocks of the Vermejoformation, the plains,and in swamps. Trinidadsandstone, and the Pierreshale. This suggests thatthe coarser facies characteristic of the Poison Canyon Cretaceousand Tertiaryrocks formationhas completely replaced the finer facies of the The Ratonformation (Lee, 1913, p. 531)crops out over Ratanformation, and thatin theextreme southwestern part mostof the RatonMesa region, and is as muchas 1,700 of the RatonMesa region the lowermostbeds of the Poison feetthick southeast of the SpanishPeaks. It consistsof Canyonformation are probablythe ageequivalents of the a thinbasal sequence of grayto darkpurple- gray siliceous basalconglomerate of the Ratonformation to the northand granuleto pebbleconglomerate or buff to graysiliceous east. conglomeraticsandstone. Above this thin basal sequence

128 NEW MEXICO GEOLOGICAL SOCIETY * SEVENTH FIELD CONFERENCE

N I WSW . ENE

I NEW MEXICO- COLORADO boundary

LOWER FACIES OF

POISON CANYON FORMATION

- ~ RATON FORMATION

"% fBasql,conglomerate of Roton f.ormatlon j VERMEJO FOR M ATION T R INIDAD I SANDSTONE ......

PIERRE SHALE

i.i ¯ lell

Fig.6.DIAGRAM SHOWING INFERRED INTERTONGUING RELATIONSHIPS OF POISON CANYON FORMATION AND RATON FORMATION BETWEEN WESTON, COLORADO AND UTE PARK, NEW MEXICO.

The upperbeds of the PoisonCanyon formation in the However,about half a milenorth of ApishapaRiver on centralpart of the RatonMesa region are mostlymeta- tl~ eastand CucharaRiver on the west,the coarsecon- morphicand igneouspebble to cobbleconglomerate. These glomeratefacies of the PoisonCanyon formation overlies coarseconglomerate beds seem to gradedownward into the an erosionsurface that cuts across the bevelededges of lowerbeds of the PoisonCanyon formation. Northwestward the uppermostbeds of the Ratonformation. Farther to the the baseof the coarseconglomerate becomes progressively norththis erosion surface cuts out the remainder of the lowerstratigraphically dueto intertonguingwith the lower Ratonformation, the Vermejo formation, the Trinidad sand - facies.Near the latitudeof the SpanishPeaks in Colorado stone,the Pierre shale, and theuppermost beds of the the uppercoarse conglomerate facies replaces the entire Niobraraformation. lowerpart of the PoisonCanyon sequence, and restswith apparentconformity on the uppermostbeds of the Raton Fieldevidence indicates that the sedimentscomprising formation(fig. 7). This conformable relationship appar- the Ratonand PoisonCanyon formations were derived from entlyprevails northward for severalmiles on boththe Precambrianor Paleozoicterranes southwest and north- westernand easternmargins of the RatonMesa region, westof the RatonMesa region.The PoisonCanyon forma-

l29 NEW MEXICO GEOLOGICAL SOCIETY * SEVENTH FIELD CONFERENCE

SSE NN.W

CUCHARAFORMAT,ON ;" :.,,°° , "-,.,o ,, ~. ;°o~j’o°::.. ~_~_ ..~.o UPPER FACIES

.._~.~.oo.¯ °.o°?.~ °. --.L_.~_.~.~,f.--.~f.o Zo" ~, ° , POISONCANYON LOWER FACIES "~--.~i.Z-~._,~.~o", °, ¯ .". ¯:o ° 5~_-~°°o. OF -’.~.~,°° ~: .,’"..... ----~--...~_P:--~-~---’-e. ~ POISON CANYON FORMATION -~-L--~-~._L~::-o.°..°.:-°o, Ooo °oo°.° ,o°o: ~o oo,-.° °°.°.. :’..: o.° ° .-:Oo ° .o-...oO o:

RATON FORMATION

VERMEJO FORMATION

TRINIDAD SANDSTONE

PIERRE SHALE NIOBRARA

Fig.?’. CONTACT RELATIONSHIPS BETWEEN POISON CANYON FORMATION AND UNDERLYING TERTIARY AND CRETACEOUS FORMATIONS FROM VICINITY OF TRINIDAD, COLORADO TO SOUTHERN PART OF HUERFANO PARK, COLORADO

tionis a piedmontfacies, and theRaton formation is a genieuplift west of theRaton basin underwent its first swampand flood plain facies laterally equivalent to the orogenicdisturbance. Mountains were formed, the extreme lowerpart of the PoisonCanyon. The yellowshale beds southwesternpart of the RatonMesa region was uplifted, in the PoisonCanyon formation suggest deposition in an and bedsof the Vermeioformation, Trinidad sandstone, oxidizingenvironment above the water table (i.e., ’~pied- and Pierreshale were subjected locally to erosion.Coarse mont");whereas the darkcarbonaceous shale and coalbeds. sandand graveleroded from these mountains were deposited in the Ratonformation suggest accumulation in a reducing in a continentalenvironment over a largepart of thepresent environment.(i.e., "swamp and floodplain"). The presenceRatonMesa region. The gravel consisted largely of detri- of manyconglomerate and conglomeraticsandstone beds tus frommetamorphic and igneousrocks of Precambrianage and the relativelyfew thinshale beds in thePoison Can- whichmay havebeen second-cycle material derived from yon :formationsuggests that Poison Canyon sediments rocksof Paleozoicage exposedto the west.The conglom- accumulatednear their sources or on relativelysteep erateat thebase of theRaton formation contains a part of gradients, the coarsesand and graveleroded from the mountains,and is theprincipal record of thisearliest orogenic phase. De- Nearthe end of LateCretaceous time the areaof epeiro-position of continentalsediments continued without inter-

130 NEW MEXICO GEOLOGICAL SOCIETY * SEVENTH FIELD CONFERENCE

ruptioninto Paleocene time, Minor orogenic disturbances stonebeds are at man:,pJaces conglomeratic and aregen- continuedintermittently in the mountains,and fine-grained erallywell consolidated. The red shalebeds are spotted sand,mud, silt, and carbonaceous material of the Raton withgreen shale lenses and irregularbodies. The thick- formationaccumulated far fromthe mountains on flood nessof the Cucharaformation ranges from a thinedge in plainsand swamps.At the sametime the coarsedetritus HuerfanoPark to at least5,000 feet in thecenter of the preservedin thelower part of the PoisonCanyon formation basinon thenorthern slope of WestSpanish Peak. accumulatedas piedmontdeposits nearer the mountains. In middlePaleocene time, while the detritus that makes up laterin earlyEocene time, orogenic movements occurred the lowerbeds of the PoisonCanyon formation was being in the mountainsto the northand west, and causedfolding and depositedin thepart of thebasin to thesouth, the north- tiltingof the sedimentaryrocks along the northwestern westernpart of theRaton basin was uplifted,and the older marginsof the RatonMesa region and in HuerfanoPark. formationswere tilted and foldedand subjected to erosion.At thistime sills of intermediateto silicic igneous rocks The lowermostbeds of the PoisonCanyon formation, the wereintruded into the sedimentary rocks along the western Ratonformation, the Verrnejoformation, the Trinidad sand- marginsof the Ratonbasin. During middle Eocene time the stone,the Pierre shale, and theupper beds of the Niobrarafine-grainedsediments of the Huerfanoformation were deformation(Meek and Hoyden,1862, pp. 419,422) were bey- positedon floodplains and borderinglowlands in the north- eledsuccessively from southeast to northwestto a local ernpart of theRaton basin. baselevel. Boulders, cobbles, pebbles, and coarsesand derivedfrom igneous and metamorphicrocks were eroded The Huerfanoformation (Hills, 1888, p. 148-164)of Eo- fromrejuvenated mountains to the westand the risingWe~ ceneage unconformablyoverlaps the Cucharaformation, Mountainsto the north.These coarse sediments were de- the PoisonCanyon formation, and thePierre shale along positedon thelocal erosion surface, and graded into the the marginsof HuerfanoPark. The formationis as muchas lowerfacies of the PoisonCanyon formation being depos- 2,000feet thick, and characteristically weathers to a bad- itedto thesouth in latePaieocene time. The coarse clas- landstopography. It consistsmainly of maroonshalebeds ticshave since been indurated to formthe upper beds of withgray and greenzones, and red,white, and tansand- the PoisonCanyon formation. They wereundoubtedly stonebeds. The shale is generallynot plastic, and con- derivedin largepart from areas of Precambrianrocks, tainsconsiderable quantities ofsilt and calcareousnod- inasmuchas the sedimentaryformations of Paleozoicand ules.The red and whitesandstone beds are shalyand Mesozoicage do.not containboulders as largeas those semiconsolidated;but the tan sandstonebeds, which occur foundlocally in the upperbeds of the PoisonCanyon nearthe baseof theformation, are ¢onalomeraticand well formation, consolidated.The principalarea of outcropof th~ Huerfano formationis in HuerfanoPark; however, an erosionalout- "[ertiaryrocks liarthat crops out on theupper slopes of WestSpanish In latePaleocene or earlyEocene time, the mountains Peakhas beententatively correlated with the Huerfano to thewest and to thenorth were again uplifted, and the formation.Hills (1901) also considered this outlier .o rocksin the northernpart of the RatonMesa region and correlativewith the Huerfanoformation in HuerfanoPark. HuerfanoPark were irregularly tilted and folded.As a result,in thispart of thebasin befls of thePoison Canyon In lateEocene time there was extensive major thrust- formationwere unevenly eroded. Most of the sedimentsof ing,normal faulting, and folding of therocks throughout theoverlying Cuchara formation were probably derived the presentmountain area of northeasternNew Mexico fromPoison Canyon rocks during this erosion cycle. The an:]southeastern Colorado. In HuerfanoPark the stra- remainingsediments were derived from rocks as old as tigraphyand structure in,dicate thatsome of theolder Precambrian.Cuchara sediments accumulated on piedmontssedimentaryrocks were locally cut out by thrustfault- andflood plains adjacent to theuplifted areas, ing andcovered by overturnedfolds. This period of majorthrusting and foldingculminated the episodesof The Cucharaformation (Hills, 1891, p. 7-9)of early Laramicledeformation; the eastern part of theSangre de Eoceneage cropsout in the troughof the Ratonbasin a few CristoMountains, the southernWet Mountains, and the milessouth of theSpanish Peaks. It extendsinto the north- structuralRaton basin of New Mexicoand Coloradowere ernpart of HuerfonoPark, and at thesurface overlaps the outlinedin general.During this last major pulsation of PoisonCanyon formation and Pierreshale with markedun- karamidedeformation, sedimentary rocks of the Raton conformity.The Cucharaconsists of massivered, pink, basinwere intruded by variouskinds of igneousrocks. andwhite sandstone interbedded with thin to thickbeds of Thearea of faulting,folding, and intrusion was then in- brightred, gray, and tan claystone.The redand pinksand- tenselyeroded in latest~ocene or earlyOligocene time,

131 NEW MEXICO GEOLOGICAL SOCIETY, SEVENTH FIELD CONFERENCE

and a greatmass of boulders,cobbles, and pebblesde- tainValley. It consistsmainly of bedsof lightgray con- rivedfrom Precambrian, Paleozoic, and Mesozoicforma- glameratictuff. The matrixis tuffaceous,and consists tionswas deposited.The onlyknown record of thisperiod generallyof angularfragments of glass,pumice, perlite, of intenseerosion and deposition in thearea, the Farisita and quartz.The coarsematerial ~s a poorlysorted mix- conglomerate,is preserved in HuerfanoPark and perhaps tureof pebblesand cobbles of pumice,perlite, and Pre- highon the slopesof WestSpanish Peak. Boulders, peb- cambriangneiss and schist.The bedsare generally bias,and cobblesof the Farisitawere deposited on an lenticularand cross ~stratified, and may be thin-to erosionsurface that truncated the oldersedlmentaryrocks massive-bedded.Local channels cut intothe tufts to the southeastand lappedagainst Precambrian metamor- arefilled with pebbles of Precambrianrocks. The for- phicrocks on the westernslopes of the Wet Mountains. mationintertongues westward with red conglomeratic sandstonederived from sedimentary rocks of Pennsyl- Bedsof buffconglomeratic sandstone of the Farisita vanianand Permianage. conglomerate(Johnson and Wood,1956, p. 718)of probable Oligoceneage unconformablyoverlie beds of the Huer- Fpeirogenicupwarping of the entireregion, accompan- fangformation and theunderlying formations of Cenozoic, led by normalfaulting, may haveoccurred in lateTertiary Mesozoic,and Precambrianage. The Farisitaconglomer- time.Erosion was followedby the depositionof sediments ate occursentirely within Huerfano Park, and rangesin of theOgallala formation over the area east of theSangre thicknessfrom a thinedge to about1,200 feet. The for- de CristoMountains during Pliocene time. Volcanoes in motionconsists of buffconglomeratic sandstone and silt- or nearthe Wet Mountainscontinued to extrudebasaltic stonebeds. The individualbeds are lenticularand highly lavaover the northern part of HuerfanoPark during later cross-laminated,and show l imonitestains on the bedding Tertiary-orQuaternary time. During Quaternary time vol- surfaces.Conglomeratic fragments range in sizefrom canoesin theeastern and southern parts of the Raton pebblesto 8- footboulders, and aresubongular to rounded basinextruded basaltic lava over large areas of the basin. and verypoorly sorted. The conglomerateis madeup most- Erosionhas continued without major interruption since ly of fragmentsof Precambrianrocks, but locally it containsthelast volcanic episode, and as a resultonly small rein- fragmentsof sedimentaryrocks of Jurassicand Permian nantsof theyounger Tertiary formations are preserved. age.Finer grains in thematrix are angular to subangular. The rocksare generallypoorly cemented, and in places REFERENCES formlandslides on steepslopes. The formationholds up a roughterrain consisting of highhills and deeply dis- Brown,R. T.,1943, Cretaceous-Tertiary boundary of the sectedvalleys. Denverbasin,. Colorado, Geol. Sac. Amer.Bull., v. 54, p. 65-86.

The Farisitaconglomerate and rocksof olderforma- Dane, C. H., 1948, Geologicmap of part of easternSan Juan tions were irregularlyeroded in lateOligocene and per- basin,Rio ArribaCounty, New Mexico,U. S. Gaol. Survey hapsin earlyMiocene time. Subsequently, in later early Oiland Gas Inv. Prelim. Map 78. or middleMiocene time, thick layers of water-laidfrag- rnentsof igneousrock and sedimentarydebris comprising Eldridge,G. H., 1888, On some stratlgraphicaland structural the Devil’sHole formation were deposited in Huerfano featuresof the countryabout Denver,Colorado, Colo. Sci. Sac. Proc.,v. 3, pt. 1, p. 86-118. Parkand in Wet MountainValley. The igneousfragments of the Devil°sHole formation may havebeen derived large- Harbour,R. L. andDixon, G. H., 1956, Geologyof theTrinidad- ly fromvolcanoes to theeast in or nearthe WetMountains, Aguilatarea, Los Anlmas and Huerfano Counties, Colorado, and the sedimentarydebris was derivedfrom the Sangrede U.S.Geol. Survey Oiland Gas Inv. Map aM 174. Cristo Mountains to thewest. Hills,R. C., 1888, Recentlydiscovered Tertiary beds of the Huerfanobasin, Colo. Sci. Sac. Proc.,v. 3, p. 148-164. The Devil’sHole formationof probableMiocene age (JohnsonandWood, 1956, p. 719)unconformably overlaps ~ 1891,Remarks on theclassification of the the Farisitaconglomerate and olderrocks of Cenozoic, HuerfanoEocene, Colo. Sci. Sac. Proc.,v. 4, p. 7-9. Mesozoic,and Paleozoicage in the HuerfanoPark area. , 1899, Elrnoro~Colorado, U. S. Geol. Survey The Devil’sHole ranges in thicknessfrom 25 to 1,300 Atlas,Folio 58, 6 pp. feet,and consistsof water-laidvolcanic rocks contain- ing pebblesof Precambriangneiss and schist.The forma- , 1901,Spanish Peaks, Colorado, U. S. Geol. tionoccurs in thenorthwestern part of HuerfanoPark, and SurveyAtlas, Folio 71, 7pp. extendsnorthward for an unknowndistance into Wet Moun- (Continuedon next page

132 NEW MEXICO GEOLOGICAL SOCIETY * SEVENTH FIELD CONFERENCE

Johnson,R. B. and Stephens,J. G., 1954, Geologyof2he La Tertiaryfossils collected in Nebraskaterritory by the Veta area, HuerfanoCounty, Colorado, U. S. Geol. Survey exploringexpedition under the commandof Capt. Win. F. Oil and Gas Inv. Map aM 146. Raynolds,U. S. Top. Fngrs. with some remarkson the rocksfrom which they wereobtained, Phil.. /~cad. Nat...... , 1954a,Coal resourcesof the La Veta area, Sci.Proc., v. 13, p. 415-447. HuerfanoCounty, Colorado, U. S. Geol. SurveyCoal Inv. Map Co20. Richardson,G. B., 1915, Castle Rock, Colorado,U. S. Geol. SurveyAtlas, Folio 198,14 pp. -~ 1955, Geologyof the Walsenburgarea, Huerfano County,Colorado, U. S. Geol. SurveyOil and Gas Inv. Woad, G. H., Johnson~R. B., Eargle~D. H., Duffner~R. T., Map aM 161. and Major,H., 1951, Geologyand cool resourcesof the Stonewall- Tercio area, Los AnimosCounty, Colorado~ Johnson,R. B. and Woods G. H.~ 1956, Stratigraphyof Upper U.S. Geol. Survey Coal Inv. Map C-4. Cretaceousand Tertiaryrocks of the Roton basin of Coloradoand New Mexico, Amer. Assoc. PetroleumGeol. Wood, G. H., Johnson,R. EL, and Dixon, G. H., 1956, Geology Bull.,v. 40, no. 4, p. 707-721. and coal resourcesof the Gulnare,Cuchara Pass, and Stonewallarea, Huerfanoand Las Anlmas Counties,Cola- Lee, W. T., 1913, Recentdiscovery of dinosaursin the rado, U. S. Geol. Survey Coal Inv. Map C-26. Tertiary,Amer. Jour.Sci., 4th ser.~v. 35, p. 531-534. Wood, G. H., Kelley,V. C., and MacAIpin,A. J., 1948, Geology , 1917, Geologyof the Raton Mesa and other regions of the southernpart of ArchuletaCounty, Colorado, U. S. in Coloradoand New Mexico,U. S. Geol. SurveyProf. Geol. SurveyOil and Gas inv. Prelim.Map 81. Paper 101, p. 1-221. Zapp, A. D., 1949, Geologyand coal resourcesof the Durango Meek, F. B., and Hoyden,F. V., 1862, Descriptionof new area, La Plata and MontezumaCounties, Colorado, U. S. lower Silurian(Primordial), Jurassic, Cretaceous, and Geol. Survey Oil and Gas inv. Prelim.Map 109.

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