Geologyand quality ol MenefeeFormation , Monero field, RioArriba Gounty, New Mexico byGretchen K.Holfnan, New Mexico Bureau of Minesand Mineral Resources, Socono, NM 87801

the Menefee Formation, the medial unit were opened during the 90-yearperiod Abstract of the Mesaverde Group. of in this area, and produc- The Monero coal field in north-central Monero field coalswere mined first to tion from 1882to 1953totaled 1.5million New Mexico, on the northeastern side supply fuel to the Denver and Fio Grande short tons (st). The estimated original of the San Juan Basin, is defined by Western Railroad built in 1881. Coal coal resource for the Monero field was Mesaverde Group outcrops that form a mining continued in the Monero field 17 million st. The remainhg demon- narrow north-south band cut by several until 1971although production greatly strated resourcefrom recent drilling in- northwest-trending faults. The coal is in decreasedafter 1959.As many as 4,0mines formation is 13.5million st (New Mexico Bureau of Mines and Mineral Resources 1990coal database).Although the Mo- I 0go nero coals are relatively thin, they were 380 Explanation valued for their high Btu value and cok- ing properties. The averagecoal analysis I Mesaverde Gp, Menefee Fm for the Monero field indicatesthese coals Crevasse Canyon Fm , Dakota Ss are low moisture (3.07o),moderate ash FruitlandFm (71.8E"),and a rank of high-volatile A ^aa Abandoned railroad bituminous. Recentexploration in this field has been minimal. A small exploration program nl978by Rochesterand Pittsburyh Coal Co. completed 11 holes northeast of the town of Monero and south of Lumber- ton. In 1987the U.S. GeologicalSurvey completed a coal-evaluationstudy of both Kl,/Kmv Area the Fruitland and Menefee Formations 1*3* ro*j -{--\ couonqoo for the ficarilla Apache Indian Reserva- . \ NEw MEXlco tion in cooperation with the Bureau of arkerCreek Indian Affairs. In 1988the New Mexico Kmv Area Bureau of Mines and Mineral Resources drilled seven holes in the northem Mo- I Hogoacr nero field as part of a larger coal-quality Kmv Field proiect funded in part by the New Mex- ico Research and Development Insti- tute. zt Data available from previous work and )^* information from recent drilling are used

Toadlena Kmfc Are

360 l;il"h"-- ChacoCanyon Alsoin thisissue /'--- KmfuArea trn'lj:{il;, BernalFormation and the ,./- v/e.]- Permian-Triassicboundary p. I -ja_'__- NMGS1990 abstracts p. 16 Upcomingmeetings p.21 Service/News p.22 Staffnotes p.24

O Albuquerque Gomingsoon Activityat the Billingsmelter FIGURE l-Coal fields of the San Juan Basin, New Mexico and railroads in northwestern New SmokeyBear State Park Mexico. Dashed line indicatesboundary of the Sanfuan Basin as defined for coal study. Modified from Shomaket Beaumont, and Kottlowski, 1971. to indicate that coals in the Monero field was not until 1922 that coal production western United States. The Monero coal were deposited in a back-barrier-swamD again exceeded16,000 st in the Monero field has been describedby Kottlowski and to lower-coastal-plain environment near field (Nickelson,1988). From7922 to 1953 Beaumont(1965) and by Shomaker(1971) the seaward extent of the Menefee For- yearly production remained above 15,000 as part of a coal-resourceand coal-quality mation. Development of these coals oc- st with a period curred in a short-lived paralic total for the of 849,270st. study of the entire SanJuan Basin. environment associated with the tran- Production in the Monero field dropped sition from a regressive to a transgres- considerablyfrom15,677 st in 1953to 3,848 Recentinvestigations sive shoreline. Although these coals are st in 1963(Nickelson, 1988). The railroad Recentcoal exDlorationhas been lim- thin, they are of relatively high rank be- was abandoned in L963,and demand for ited in the Monerofield. In 1978Rochester cause of subsequent depth of burial and coal decreasedsignificantly. ln 1970the and PittsburghCoal Company leased sev- close proximity to the lirge heat source last mine in the Monero field closedwhen eral parcelsof state-ownedcoal lands south of the San volcanic complex. Recent fuan the owner was financially unable to com- of Lumberton and north of the town of studies propose heat advection by ply with the new mine-safety laws (Nick- groundwater Monero where they drilled elevenholes. influenced the rank of the elson, 1988,p. M9). Fruitland Formation coals; it is quite Severalof the coal beds encounteredwere possible that advected heat also influ- Most mines in the Monero field were cored and analyzed.Most of the coalswere enced the Menefee Formation coals. locatednear the town of Monero and de- thin and discontinuousso the leasewas Iivered coal to the D&RGW railroad, but dropped. several Introduction mines were developed after 1921 As part of a joint project with the Bu- south of Lumberton. One of thesemines reau of Indian Affairs (BIA) in 1986, the Coal mining in New Mexico was more (Burns-Biggs) supplied coal to a spur U.S. GeologicalSurvey drilled severalholes extensivein the late 180ffsand early 1qJ0's owned jointly by the D&RGW and Bums- in the Menefee and Fruitland Formations than it is today. Most of the smaflercoal Biggs Lumber Company and built to in the northern Apache Indian fields that were active in that early period Jicarilla transport lumber from Lumberton south Thesedrill holes and are located outside the major coal-pro- Reservation. more to the company's sawmills at El Vado than 400 available oil and gas logs were ducing regions of the San or Raton Juan (Myrick, L970).Several mines in the Lum- used to evaluatethe coalresources of both Basins. The Monero coal field is a rela- berton area supplied coal to the Indian the Menefeeand Fruitland Formationsin tively small, isolatedfield among the in- agency at Dulce. From 1881 to 197Las the study area.The interagenryreport was active areas, but it is located in a maior many as 40 mines were open at various prepared by Olson and Gardner (1987)for coal-producingregion. The Monero field times in the Monero-Lumberton area;they the TicarillaTribe and the BIA. on the northeastern flank of the San Tuan produced a total of 1.5 million st of coal Basin is delineated by outcrops of the between1882 and 1963(Nickelson, 1988). MesaverdeGroup that extendsouthward from near the ColoradeNew Metco State Previous work Line for about45 mi (Iig. 1).The purpose One of the earliestdiscussions the of this paper is to combine all available of Monero field was by Gardner (1909)who coal data, including recent drilling data, New AAexfic@ mentioned the presenceof coal in the vi- for the northern Monero field and eval- cinity of Monero and noted the displace- uate both general trends of the coal-bear- GEOLOGY ment of the coal-bearing rocks by the ing sequence and characteristics of the northwest-trending Monero fault. In- o Scienceand Service coals in the northern Monero field. cludedin this report werea few measured tssN 0196-944X sectionsand coalanalyses. Campbell (1922) Volume 13, No. 1, February 1991 Mining history compared coals of severalNew Mexico Editor:Carol A. HjeUming Small underground coal mines oper- coal fields, including Monero, to other Published quarterly by ated in the Monero field from 1881.to 7977. areasin the United States.Fieldner et al.'s New Mexico Bureau of Mines and Development of the coal resources (1936)compilation Mineral Resources in this of mine-sampleanal- a division of New Mexico Instihte of area began when a market for coal was yses for New Mexico incorporated several Mining & Tehnology createdby construction of the Denver and analysesfrom the Monero field. Their re- BOARD OF REGENTS Rio Grande Western Railroad (D&RGW) port included descriptionsof the mine lo- Ex-Officio Bruce King, Gwmor ol Nn Metico through the coal field. In 1881a small rail- cations and the coal sectionsthat were Alan Morgan, Supqintendent ol Public lnstruction road, lumbet and coal camp was estab- sampled.Dane's field investigationsand APPointed lished Steve Tores, Prq., 1967-19)7, Alhuquerque at Amargo, but the center of coal subsequentmap (1948)of the northeast- Carol A. Rymer, M.D., SecJTteqs., 1989-1995, activity for this field datesfrom 1884when ern part of the SanJuan Basin encompas- Albuqurque a group of Italian miners settled the town ses the northern half of the Monero coal Robert O. Andenon, 1987-1993, Roswll (or Lenton Malry 1985-191, Albuquerque of Monero, Italian money (Nickelson, field. Dane mapped the coal-bearing Lt. Gen. L@ Marquez, 1989-195, Albu4uqque 1988).The remnantsof Amaigo arebarely MesaverdeGroup as one unit recog- New Mexico Institute of Minin8 & Technology but Presiddt . . Laurence H. lattman visible today, but the town of Monero still nized three formations, which he referred New Mexico Bureau of Mines & Mineral Resources exists although it is sparselypopulated. to, in ascendingorder, as the HostaSand- Direclol ond State G@logist . . Frank E. Kottlowski M. Coal mining in this area was difficult be- stoneMember of the Point Lookout Asniate Dirctor James Robertson Sand- Sufuriniore: Issued qurterlt February, May, August, cause of rugged terrain formed by major stone, the Menefee Formation, and La November; subsription price $6.O0/calendar year. northwest-trending faults that cut the area Ventana Sandstone Member of the Cliff Editotial ruttq: Articles submitted for publication into several fault-block mesas.Generallv. House Sandstone.To Dane's should be in the editor's hands d minimum of five date geo- (5) months before date of publication (Februry, two 3-4 ft bedswere mined, and in manv Iogic map (19a8)is the best available of May, August, or November) and should be no longer places the coal is offset by minor r""o.rd- the Monero field and subsequently was than 20 typewritten, double-spaced pages. All sientific papers will be reviewed by at least two ary faulting perpendicular to the maior used in the recentcompilation of the Az- people in the appropriate field of study. Address fault system. tec 1o x 2'by'estimated Manleyet al. (1982).Read inquiriB to Carol A. Hjelning, Editor of N@ M$ie Peakcoal production in the Monero (1950) GroloSV. New Mexico Bureau of Mines & Mineral field et al. the original bitu- Resources. Saono, NM 878014796. occurred between 1899and 1908.A total minous resources(at depths lessthan 1,000 Prblished as publi domin, ther4orc rcprodrcible uithout oI 39t,752 short tons (st) were mined, ft) in the Monero field to be 17million st. wmission. Source oedit ruuested. which essentially depleted the known re- Averitt (1966)included a short discussion Circulation: 1,6ffi serves.After an economicrecession in 1908, of the Monero field and the quality of the P/irlelr University of New Mexico Printing Seryices production dropped to 9,779st in 1909.It coals in his report on coking coals in the

February 7997 New Merico Geology In 1988the New Mexico Bureau of Mines the surfacetotal 13.5million st of coal in bedsis quite variable.The structurein the and Mineral Resources (NMBMMR) drilled the northern Monero field. northem Monero field has createda mesa- seven holes in the Monero-Lumberton area and-canyon topography, and outcrops of as part of a larger coal-quality study par- _ Geologicsetting the MesaverdeGroup are limited primar- tiallv funded bv the New Mexico Research Strucrure ily to the steepcanyon walls of thesefault- and-Developrnent Institute (NMRDI). For The Monero field is structurally com- block mesas. the larger study drill holes were com- plex, relativeto other SanJuanBasin coal pleted at approximately 150 sites through- fields.This coalfield is locatedin the east- Stratigraphy out the SanJuanBasin. Roybal etal. (1989) ern part of the Archuleta arch (F\9. 2), The Upper Cretaceousdeposits in the discussed the Monero drilling and the coal which separatesthe centralSan Juan Ba- San fuan Basin are a seriesof transgres- analyses. The primary objective of the sin from the smallerand shallowerChama sive and regressivesequences. The Mesa- NMRDI study was to obtain coal cores for Basinto the east.The ChamaBasin is gen- verdeGroup consistsof barrier-beachand analysis and to acquire stratigraphic in- erally considereda sub-basinor embay- nonmarine units from the baseof the Gal- formation about the coal-bearing se- ment of the Sanfuan Basin.The Gallina- lup Sandstoneto the top of the Cliff House quences through geophysical logging of Archuletaarch is boundedon the west by Sandstone(Fig. a). The lower Mesaverde the drill holes. To acquire the most strati- a monocline that dips into the San Juan Group is presentin the south-southwest- graphic information from drilling done in Basin (Woodward, 1987). Much of the ern San fuan Basin, but becauseof the the Monero field and elsewhere in the ba- northern Monero field is influenced by progressionof the shorelineto the north- sin, the entire coal-bearing sequence and small domes and northwest-trending east with each transgressive-regressive at least the upper 40 ft of the underlying synclines,part of the Archuletaarch (Dane, cycle, only the upper MesaverdeGroup stratigraphic unit were penetrated at each 1948).The structuraltrend in the southern was deposited in the Monero field. Al- location. With depth to the underlying Monero field parallelsthe N30'W trend of though the crosssection was constructed formation known, the coal-bearing se- the Gallina arch. There are severalmaior along the western edge of the San Juan quence can be placed within the strati- faults in the Monero field that parallelthe Basin, the northeasternpart of the sec- graphic framework of the area, and easternedge of the San fuan Basin (Fig. tion, near Durango, is considered ap- correlation between drill sites is facili- 3). Most, but not all, faulting is believed proximately equivalentto the stratigraphic tated. to be associatedwith and contempora- sequencein the Monero area.The relative Using the recent drilling data, remain- neouswith this folding (Dane,1948). Faults positions of the shoreline(Molenaar, 1.983) ing resources have been estimated in the Monero areatend to be high angle during the deposition of the Mesaverde (NMBMMR 1990 coal database). Mea- and normal with displacementsof lessthan Group (Fig. 5) support this assumption. sured (within l/+-mi radius of the mea- a hundred feet (Dane,1948). Manly et al. The MesaverdeGroup is composedof sured coal bed) and indicated (from 1/+-to (1987)indicate that most of the displace- threeformations in the northern SanJuan 3/a-mi radius) resources for coal seams ment is downdropped to the west. Be- Basin (Fig. 4). The oldest unit, the Point greater than 1.25 ft and within 500 ft of causeof structureand faulting, dip of the

Monerofield

Farmington Archuletaarc

Centra I l/l ) \ Basrn 'ttte Gallin arcn z (Cretaceousoutcrops) o

Y-a a

n orants O

24mt

FIGURE2-Tectonic map of the SanJuan Basin, New Mexico.From Beau- FIGURE 3--4eologic map of northern Monero field, New Mexico Cross mont, 1982,printed with permissionfrom AmericanAssociation of Pe- section lines for Figs 6 and 7 included. From Dane, 1948.Kl, Lewis Shale; troleum Geologists. Kmv, Mesaverde Group; Kum, upper Mancos Shale.

Nm Mexico Geology February 7991 ChuskaMtns NM Colo Durango Lookout Sandstone,is a barrier-beachto nearshore sandstone that conformablv overliesand intertongueswith the marinL I I raruoar ano ltuvtal 5O00fr Mancos Shale.The Point g | | nonmarine Lookout Sand- stonewas depositedduring a major with- 3 r--'-----t Beach and near- tJ snore mailne drawal of the Late Cretaceousseaway to 4000 the northeast. In the Monero areathe for- mation consistsof 50-200ft of predomi-

Hogback Mountarn tongue nantly massive,well-sorted, clean quartz sandstones. t> 3000 Above the Point Lookout barrier-beach lvlenelee rm I upper coal mbr sandstone,the rocks of the lower part of

lower coal mbr the MenefeeFormation representthe re- Allrson Barren Mbr I 2000 gressive back-barrier-paludalto lower- coastal-plainfacies. The sequenceconsists of silty sandstone,siltstone, mudstone, GrbsonCoa I MbJ-a, ,/ _-i_1.+;;;;"";:;;""f---:-a tan Tong ue carbonaceousmudstone, and coal. The ' Mancossh ui:Jl"il;r,"-) -.;:o-Dai,onssMbr 1000 upper part of the Menefeeis composed GallupSs. '-<22-!"latto Tongue of the back-barrier-swampand nearshore deposits developed during the subse- 0 quent transgressivecycle, so it is litho- lowerpartoltheMancosSh logically similar to the lower /DakotaFm Menefee Formation. The Menefee Formation is about 2,000ft thick in the southern San FIGURE4-Stratigraphic diagram of Cretaceousrocks, SanJuan Basin,New Mexico and Colorado. JuanBasin (Fig. a), but in the Monerofield From Beaumont, 1982.Line of section shown in Fig. 5. the Menefee is only 50 to 100 ft thick be- cause of the close proximity of this area to the maximum seawardposition of the Mesaverdeshoreline prior to the reversal of the shorelinemovement (Fig. 5). The overlying Cliff House Sandstone consistsof barrier-beachand nearshore sandstonesthat intertonguewith the up- per Menefee Formation and the overlying marine Lewis Shale.Although the depo- sitional environment of the Cliff House Sandstoneis similarto the Point Lookout. the sandstonesare not as massivein the northern Monero field, and the total thickness,30-80 ft, is lessthan the Point Lookout (Dane, 1948).

Methodology Dataon stratigraphyand coalthickness and quality were assessedby comparison with published data from Nickelson (1988) and Fieldner et al. (1936),with Dane's (1948)geologic and structural mapping, with new data from NMBMMR, and with unpublished data from Rochesterand Pittsburgh Coal Co. Most of these coal data are limited to the northern Monero field, therefore this is the principal area of investigation. Two crosssections (Figs. 6 and 7) in the northern Monero field were constructed using NMBMMR drill logs and unpub- lished Rochesterand PittsburghCoal Co. drill-hole information. Where the baseof the MesaverdeGroup was not pene- trated, Dane's (1948)structure contours (Fig. 3) were used to determine the ap- proximateposition of the baseof the unit. The accuracyof these structure contours was checkedwith the holes that did pen- etrate the underlying Mancos Shale and was found to be reliable. Correlation of units on the cross sections is limited to formation boundaries becauseof distance between drill sites and variability of the MenefeeFormation.

February 1997 Neu Mexico Geology FIGURE 6-southwest-northeast cross section from drill-hole data in northern Monero field. Line of section shown on Figure 3.

Explanation Alluvium Sandstone Siltstone Silty sandstone,siltY shale Shale Claystone Carbonaceousshale Coal

Kch - Cliff HouseSs. Kmf - MenefeeFm. Kpl - PointLookout Ss. Kmv- MesaverdeGrouP Km - MancosShale

FIGURE 7-Northwest-southeast crosssection from drill-hole data, northern Monero field. Line of section shown on Figure 3.

New Mexico Geolog! February 7991 General trends in the L{}1.{}K&Dil Mesaverde Group \* qiirr Two cross sections in the northern Mo- \ o.o nero field were constructed to determine general lithologic trends in the drill-hole \ data. The southwest-northeast cross sec- tion (Fig. 6) shows a decreasein thickness I \ of the Menefee Formation to the north- N /\ east. This section, above the Point Look- (t out (Kpl), has an increase in siltstone and *00 \ \ sandstone and a decrease in mudstone, I total coal thickness, and coal frequency to I the northeast. All the drill holes have ioal 15t \ directly on top or within a few feet of the I *o0 Point Lookout Sandstone contact. Drill- I I hole section 3 south of Lumberton -t' o5 (Fig. I .n 3), where many of the old mines weie I J^ 8\ located, has the greatest number of coals and probably the thickest nonmarine se- quence (approximately 100 ft) in this cross S7 section. c Kmv 25 13 .- o, The northwest-southeast cross section 30' \r30 (Fig. o-i t 7) has more NMBMMR drill holes 30 ?ro \ and therefore provides more control for a26 \:.r Y6r:, rI 30 the correlation of units. This cross section \, 28 originates south of the town of Monero and terminates near the Colorado border (Fig. 3), almost parallel to the Late Cre- i'i,, taceous shoreline. The Point Lookout ir:r.1ianlle Sandstone thickens to the northwest as the overlying Menefee Formation appears Number + to pinch out. The presence of mudstone of Seams and coal in the Menefee Formation is greatest just north of the town of Monero *o a3 (Fig. 7, sections B-D), and decreases to o 1 a5 V" the northwest. Coal occursdirectly on top a2 t-7 or within a few feet of the Point Lookodt contact, as shown in Figs. 6 and 7. At O 1mi many localities coal is present at what is considered to be the top of the Menefee Formation (Fig. 7). The position of these FIGURE 8-Coal thickness and contours in the northern Monero field. Data from Nickelson, 1988; coals at the top and base of the Menefee Fieldner et al., 1936;Roybal et a|.,7989; and Rochester and Pittsburgh Coal Co. unpublished data Base map Formation, iust above or below a barrier- modified from Dane, 1948 beach sandstone, tends to substantiate a back-barrier-swamp environment for these coals. The overlying Cliff House Sand- stone probably intertongues with the Me- locatable coal-thickness data are available southeast of Lumberton (Fig. 8). These nefee Formation. Some of the sandstones from mine and coal-quality sources (Nick- areas of thicker coals tend to be elongated and siltstones in the upper part of the efson, 1988; Fieldner et al.,7936; Roybal, parallel to the shoreline, characteris'iic of interval that has been designated Mene- et al., 1989).Fig. 8 shows Menefee coal- back-barrier-beach coals. fee on the cross sections may be sand- bed thickness and number of beds from Limited data west of the Mesaverde stone tongues of the Cliff House. Point drill-hole and coal-samplinginformation. outcrops (Fig. 8) does not allow coal thick- Lookout Sandstone appears to be directly The values in some casesare averages of ness to be determined; it is postulated that overlain by Cliff House Sandstone in th-e two or more coal beds at each location, Menefee Formation coals would be pres- two northernmost drill-hole sections (Fig. but several values are of individual seams, ent in the subsurface and may be as thick Z). The Cliff House sandstones are siltier generally from sections in mines. Al- or thicker than those in the Monero-Lum- and not as massive as the Point Lookout though the data is clustered in the south- berton area. This assumption is made be- sandstones in the northern Monero field. ern section of the map, a decrease in the cause a thick buildup of Point Lookout These lithologic differences between the coal thickness to the north-northwest is Sandstone represents a stillstand of the Cliff House and the Point Lookout sand- evident. The average Menefee coal bed is shoreline in the northernmost Monero stones suggest a fairly rapid rate of shore- slightly less than 3 ft in the Monerelum- field, which would allow for back-barrier line shift to the southwest, eliminating the berton area. The thin and limited extent and lower-coastal-plain swamps to de- chance for thicker buildups of sandstone of the coals shown in the cross sections velop. The total coal-thickness isopachs such as those in the Point Lookout Sand- (Figs. 6 and 7) and in the coal-thickness (Fig. 9) by Crist et al. (1989) tend to sup- stone. map (Fig. 8) indicates the swamp envi- port the idea that thicker coals were de- ronment was restricted and short lived in posited west of the defined Monero field. the northern Monero field. The Coal thickness area of greatest coal thickness (>3.5 ft) is con- The cross sections discussed above show centrated in a northwest-southeast trend, Quality the frequency and coal-thickness trends encompassing the area around the town Coal quality is an indicator of the coal in the northern Monero field. Additional of Monero and is isolated in two areas depositional environment as well as the

February 7991 Nat Mexico Geology TABLE l-Available quality analyses for the Monero and other Menefee Formation fields, San fuan Basin, New Mexico (analyseson an as-receivedbasis) . Sourceof data: NMBMMR 1990coal database.

Fixed Vol. Moisture Ash carbon mat. Sulfur Btu MMFBtu Thickness

Monero field Average 3.00 11.80 49.24 37.8r 1.89 12,562 14,46 2.t# Maximum, 8.37 30.40 55.10 40.56 5.92 13,798 t4,93 6.40 Minimum 1.50 5.30 41..6 34.00 0.40 9,114 10,694 0.M Number of samples M M3838 MM u21

All other Menefee Formation fields Average 15.38 17.27 37.85 35.48 0.96 10,777 17,602 4.M Maximum 26.73 33.80 67.73 56.17 5.17 12,385 r4,w 23.80 Minimum 4.ffi 1.30 21.9 22.22 0.10 8,132 9,2n 0.90 Number of samples 345 YS 325 325 325 343 u5 345

FIGURE9-Isopach of total coal thicknessin ter-freeBtu values (MMFBtu) that deter- Mesa, Hogback, and northern San Mateo the MenefeeFormation, northeastern San fuan mine rank (Table1) vary greatly from high- coalshave lower moisturevalues (ash-free) Basin.Modified from Crist et al.. 1989,printed volatile C bituminous to high-volatile A (10-I5Eo). Menefee coal MMFBtu values with permission from Societyof PetroleumEn- bituminous. Monero coals have the high- range from approximately 8,000Btu/lb to Srneers est rank and heatingvalue (Btu)of all Me- greater than 12,000Btu/lb. The MMFBtu nefee Formation coals (Table1). The values (Fig. 11) increasefrom southwest remaining Menefee coals in the San fuan to northeast.The northern Monero coals Basinrange from subbituminousC to high- have the highest MMFBhTvalues (>13,000 volatile A bituminous rank. Btunb). Most of the Standing Rock, Chaco degree of coalification. The average/max- Canyon, and Newcomb coals have the imum, and minimum valuesof the avail- Iowest MMFBtu values (9,000-11,000Btu/ able qualiry data for Monero and other Comparison of coal rank lb). Menefee Formation fields are presented Indicatorsof coal maturity or rank are Moisture and MMFBtu values illustrate in Table1 on an as-receivedbasis, except calorific value (Btu/lb, moist, mineral- the increase in rank or degree of coalifi- for moist, mineral-matter-free Btu matter-freebasis), moisture content (ash- cation in Menefee Formation coals from (MMFBtu) values. Locatablequality data free basis), percent volatile matter (dry, south-southwest to northeast in the San from the Monero field were plotted to de- ash-free),fixed-carbon content (dry, ash- Juan Basin.Northern Monero coalshave termine geographic trends; none were free basis), and reflectance the highest rank of the fields with anal- evident so thesediagrams have not been (American Society of Testing Materials, yses. Northern Hogback and Barker coals included. 1985;Rightmire, 1984).Different indica- may be of equivalentrank to Monero coals, Point-sourcedata for the northern Mo- tors are used to determine the degree of but supporting data is lacking. nero field do not revealany distinct geo- coalificationin lower rank coalsthan those Other studies (Shomakerand Whyte, graphic trends in the sulfur content of used for the higher rank coals. Moist, 7977; Crist et al., 1989) that have dealt Menefee coals; however, the sulfur con- mineral-matter-freeBtu values(MMFBtu) with deep Menefee Formation coalshave tent itself is variable (Table1). Average and agglomeratingproperties determine noted the increasedrank in the northern sulfur content for the northem Monero the rirnk of coals in the to high- Sanfuan Basin.This increaseis attributed field (1.89%)is the highestof all Menefee volatile B bituminous range. Rightmire in part to close proximity of the San fuan Formationfields; average forMenefee coals (1984)also indicatedash-free moisture as volcanic complex. Several studies (Reiter in other parts of the San fuan Basin is an important indicator of coalification in and Clarkson, 1983;Choate and Right- closer to lVo. The higher sulfur content of the lower coals.In the higher rank coals, mire, 1982)using heat-flow and hydro- the Monero coals and the stratigraphic high-volatile A bituminous to meta-an- carbon vitrinite-reflectancedata found the positionof many of thesecoals (just above thracite, fixed carbon (dry, ash-free),and geothermal gradient increasedtoward the or below the Point Lookout and Cliff House volatile matter (dry, ash-free)are impor- northern San fuan Basin. Some of these barrier-beachsandstones, respectively) are tant in calculatingrank. studies attribute the increased hydrocar- indicative of back-barrier-swampenvi- Most of the Menefee Formation coals bon rank in the northern part of the basin ronments where the swamp depositswere areof a subbituminousto high-volatilebi- to the closeproximity of the SanJuan vol- subjectto periodic invasionsby the sea. tuminous rank, therefore ash-free mois- canic complex, a massive heat source. Locatableash-content values of Monero ture content and MMFBtu values were Clarkson and Reiter (1987)believe con- coalsdo not show any definite geographic plotted within surface-minableMenefee ductive heat flow from Oligocene mag- trends, and the average(11.80%) is ap- coal areas in the San Juan Basin to deter- matism and depth of burial before Eocene proximately the sameas that for other Me- mine any apparent coalificationtrends. erosion are not sufficient to account for nefee coal fields (11.27V").These values Data points (Figs. 10, L1) representindi- the observed maturation pattern in the are moderately low for San Juan Basin vidual sites,but values may be averages northern San fuan Basin. They suggest coals, many of which have ash contents for several analyses from the same loca- heat advection by ground-water flow also of. l5-20Vo. The source of ash in Monero tion. The moisturecontent (ash-free basis) may be a significant influence. Regional coals could be attributed to sediment (Fig. t0) generally increasesfrom north- ground-waterflow h the northeastemPart brought into the swamp environment eastto southwest.Northern Monerocoals of the basin is from the San Juan Moun- during occasionalstorms or shifts in the have the lowest moisture content (2-5Vo) tains toward the north-central part of the fluvial-drainage pattern. while Chaco Canvon, Standing Rock, San basin (Stoneet al., 1983).This theory,es- Although the majority of Moneio coals Mateo, and La Ventana fields have the pecially with reference to the Menefee are bifuminous, the moist, mineral-mat- highest moisture content (15-20%).Chacra Formation, needs further study. rj

New Mexico Gmlogy February 7997 Explanation Explanation @ H-]-l# 1 5olo > 13.OO0 Bru,/lb 1..\\ s-roy" 1l,OOO 13,OOO ro-15% -F----j 9,OO0 1 1,000 Btu,/lb 15-2oy" vr1 Data points . Data points Field dividing lines --- Field dividing lines

\Jt-*J Standing ..v Rock 7 fi!,,f-4

La Ventana La Ventana

FIGURE 10-Moisture content (ash-free basis) of Menefee Formation coals FIGURE 11-Btu values (moist, mineral-matter-freebasis) of MenefeeFor- in designated coal fields of the San Juan Basin. Base map modified from matio_ncoals in designated coal fields of the San Juan Basin. Basemap Clemons et al., 7982, printed with permission from New Mexico Geolog- modified from Clemons et al., 1982,printed with permission from New ical Society. Mexico Geological Society.

Summary and conclusions tent of the shoreline of the Point Lookout may have contributed significantly to ma- The Monero field was an area of coal Sandstoneand MenefeeFormation (Fig. turation of the coalsin the San|uan Basin. mining from the 1880'sinto the early 1920's. 5) are supportedby availablepoint-source AcKNowLEDGMENTS-Iwould like to The impetus for this activity was the data; the Menefee probably was not de- thank several people for their reviews of building of the Denver and Rio Grande posited in the northemmost Monero field, this article. Frank Kottlowski encouraged Western Railroad through the area. Al- and the Point Lookout Sandstoneis di- me to follow through on the proposal to though the coals in the Monero area are rectly overlain by the Cliff House Sand- write this paper and made beneficialsug- relatively thin and the terrain is rugged, stone. Thinnessof the MenefeeFormation gestions on the manuscript. Marshall Rei- these are high-quality coals that proved and the coalsin the Monero field indicate ter was extremely helpful in supplying to be a valuable resource for the railroad thesenonmarine sediments and the coals material on the implications of the in- as well as domesticuse for almost90 years. in particular were depositedin short-lived, creasedrank of coal in the northem San The Monero coal field probablydoes not unstable back-barrier-swampto lower- Juan Basin. Marshall also made many havea significanteconomic-resource base coastal-plainenvironments behind the re- constructive comments on this paper, in (13.5million st, remaining demonstrated gressiveand subsequenttransgressive particular, on the comparison of coal rank resources)for coal mining today because barrier-beachenvironments. High-sulfur section.Orin Andersonalso reviewed this of the remotenessand structural com- content of thesecoals and thicknesstrends manuscript and made several helpful plexity of this area, but data from the Mo- parallel to the shoreline support the hy- comments,especially pertaining to stra- nero field may be useful in detbrmining pothesis of deposition in a back-barrier- tigraphy and depositionalenvironments. what the coal characteristicsare in the swamp environment subjectedto occa- I am appreciativeof thesecomments and MenefeeFormation at greaterdepths just sionalseawater flooding. Increasedthick- subsequentdiscussions with Orin. Many west of this areain the Sanfuan Basin. ness of the Point Lookout Sandstonein thanks to |ohn Shomaker for taking time Early geologicinvestigations in this area the northernmost Monero field may be out from his busy scheduleto review this were limited. Dane's(1948) investigations indicativeof a minor stillstandin this sec- paper and make important suggestions and s_ubsequentgeologic map including tion of the shoreline.This buildup of shore- and comments, particularly on the rail- the Monero coal field are basedon out-- margin sandstonesmay indicatethe pres- roads and the coal resourcesin the Mo- crop data and a few oil and gaswells avail- enceof a correspondinglythicker coalse- nero area.Both Ed Beaumontand Nancy able at that time. With thia information, quence in the back-barrier environment Gardner, who are very familiar with thl Dane mapped the MesaverdeGroup as west of the Monero field. area of study, had miny beneficial sug- one unit, although he recognizedthe Point The rank of Monero Menefee Forma- gestionsand commentson both the text Lookout Sandstone,Menefee Formation, tion coalsis significantlyhigher than sim- and figures that have been, along with the and Cliff HouseSandstone. Dane felt that ilar Menefeeco=als in the'sorithemSan Juan other reviewers' comments, incorporated the entire Mesaverde Group section be- Basin.The moisturecontent and Btu val- into the final product. I wish to sincerely came sandier to the north and the indi- ues in particular indicate thesecoals have thank all these reviewers for their time vidual units were not discernable. undergone a greater degree of coalifica- and effort to give such thorough critiques, Recentdrilling in the Monerofield sup- tion. Studiesby Reiterand Clarkson(1983) which hopefully has made this a more plies further evidence about the Mesi- show the northern Sanfuan Basinhydro- interesting and comprehensive article. verde Group and indicates the nonmarine carbonshave been influenced by deith of Thanks also to RebeccaTitus who drafted Menefee Formation thins and may pinch burial and heatfrom the Sanfuanvoicanic the final figures. out in the northern Monero field. Mole- complex. Clarkson and Reiter (1987)sug- naar's (1983) projectionsof maximum ex- gest heat advection by ground-water flow (R$erenceson p. 21)

February 7991 New Mexico Geology squaremiles (75.8square km) of the southern San Mateo Mountains in soutii-central Socorro Upcominggeologic C.or."-ty Thick sequencesof Tertiary lavas, ig- meetings nlmbntes, and associatedvolcaniclastic anZ sedimentary rock units are grouped from old_ Conference title Dates est to youngest as the Red Rock Ranch for_ Location Contact for more information 22nd Annual Gem and March 16-17 UNM Continuing Albuquerque Gem and Mineral Show Education Mineral Club Conference P.O. Box 13718 Center Albuquerque, NM 87192 Albuquerque, NM in the stratigraphic section. Repeated volcan- New Mexico otectonic activity related to cauidron April 5 Macey Center Richard M. Chamberlin develop- Geological Society ment has.produced complex stratigraphic Socorro, NM NMBMMR and annual spring meeting structuralrelationships in the areai.Gold and Socorro, NM 87801 silver depositsof the'SanJose and San Mateo (505)83s-s310 AAPG Mou.ntainsmining districtsoccur along a broad annual meeting April 7-10 Dallas, TX Charles F. Dodge (with northeast-trendingfault systemwithin cross_ SEPM, EMD, and DPA) 607 Meadows BIdg. cutting.fracfurezones, breccia pipes, and veins. Dallas, TX 75106 Mineralization is associatedwiti late-phasein- (2r4)'363-2937 trusive rocks. Hydrothermal alteration that 9th Annual Oil & Gas May 7-8 Albuquerque, NM Dana Escudero surrounds mineralized zones is discernible in Conference for Public Affairs, BLM enhanced satellite imagery. tr Industry & Govemment PO. Box 1rt49 SantaFe, NM 87504-1449 (505)988-6315 Grand Junction June 6-8 Colorado Bill Chenoweth Geological Society and Utah 707 BrassieDrive dinosaur quarries Grand Junction, CO field trip 81506 (303) 242-9062 trtrtrtrtrtrtrtrtrtrtrtrtrtrtrtrtrtrtrtrtrtrtrtrtrtrtrtrtrtrtrtrtrtrtrtrtrtrtrtr

(Continued t'romp. 8) A D., 1950, Coal resourcesof New Mexico: U S GeologicalSuruey, Circular 89, 24 p. Reiter,M., and Clarkson,G., 1983,Relationships be- tween heat flow, paleotemperatures,coalificition, References and petroleum maturation in the San fuan Basin, northwest New Mexico and southwest AmericanSociety of TestingMaterials, 19g5, Annual Colorado: Geothermics,v. 12, no. 4, op.323139. book of ASTM standards,gaseous fuels, coal and Rightmire,C.T.,198/., Coalbeil methane :American Society of Teiting Materials, v 05.05, resource;in p.251. Rightmire, C. T., Eddy, G. E., Kir, J. N. (eds.), Averitt, P- 1956,Coking-coal Coalbed methane resourcesof the United States: depositsof the western Gardner,J. H.,1909, The coal field betweenDurango, UrutedStates: U. S. Geological American Associationof Petroleum Ceologists, Suwey, Bulletin lZ_ Colorado and Monero, New Mexico; ln - G, p. 34. ConhiSu- Studies in Geology Series,no. 77, pp. l-1,3. tions to economicgeology: _ U.S. GeologicalSuruey, Roybal, C. H., Campbell,F. W., Beiumont, E. C., Bulletin341, pp. tSZ-3Ol. Bellis,D., Kottlowski,F E.,andCohen,A. D., 1989. Kottlowski, F. E., and B€aumont,E. C., 1965,Coal; Quality assessmentof strippablecoals in New Mex- in Mineral and water resourcesof New Mexico: New ico, Year III, Phase II, Menefee, CrevasseCanvon Mexico Bureau of Mines and Mineral Resources, and Moreno Hill Formation coals in the San liran Bulletin 87, pp. 100-116. Basinand Salt Lakecoal field: New MexicoResearch Manley, K., Scott, G. R., and Wobus, R. A., 1982, and_Developmentlnstitute, Report 2-76-5310,pp Geologicmap of the Aztec 1. x 2. quadrangle, M-50,87-90. northwestem New Mexico and southern Coloriio: Shomaker, J W , 7971,Monero Mesaverde field: ir U.S. Geological Suruey, MiscellaneousInvestiga- Shomaker,J. W, Beaumont,E C., and Kottlowski. tions Map I- 1730. F E. (eds.),Strippable low-sulfur coal resources of Molenaar,_ C. M., 1983,Maior depositionalrycles and the San Juan Basin in New Mexico and Colorado: regional conelations of uppei Cretaceousrocks, New Mexico Bureau ane potential in the Piceance,San of Mines and Mineral Re- Juan and Raton southernColorado Plateau ind adiacentareas; in sources, pp. g6-n. Basins,Colorado and New Mexicoj proceedings Memoir 25, in Reynolds,M. W, Dolly, E. D., (dds.), Mesozoic of the unconventionalgas Shomaker,J. W., Beaumbnt,E. C, and Kottlowski, recoverysymposlum, Mav paleogeographyof the west-central 1_6-18,t982, pittsburgh, pennsylvinii: United States: F. E , 1971,Strippable low-sulfur coal resourcesof Smietv Jf Rocky Mountain Sectionof the Society retrole_um_Engineers/U.S. of Economic the San fuan Basin in New Mexico and Colorado: Dept. of Energy, l0'g05, and pp. - _Paleontologists Mineralogists, pp. 207-224. New Meico Bureau of Mines and Mineral Re- 151-164. Myrick, D. F., 1970,New MexicJs railioids: Colorado sources,Memoir 25, 189 D9. Railroad Museum, Golden, Co , pp 95-770, 160- Shomaker,J. W., and Wtryie, Vf. R.,lgn, Geologic 161. appraisalof deepcoals, San Basin,New Mdx- Nickelson, Juan H. B., 1988, Monero coal field; in One ico: New Mexico Bureauof Mines and Mineral Re- hundred yearsof coalmining in the SanJuan Basin, sources,Circular 155,58 pp. New Mexico: New Mexico Bureau of Mines and Stone, W. J., Lyford, F. P., Fienzel, P F., Mizell, N Mineral Resources,Bulletin 711,,pp l7-L8, l3g- H., and Padtett, E., 1983,Hydrogeology and water 171. resourcesof the SanJuan Basin,New Mexico:New Olson, A B., and Gardnet N. K., 1982,Coal re- Medco Bureau of Mines and Mineral Resources. sourcesof the northern half of the Iicarilla Apache Hydrogeologic Report 6, 70 pp. Indian Reseruation, Rio Arriba CounW, New'Mex- Woodward, L. A., 1987, Geoi6gy and mineral re- ico: U.S. Geological Suruey, interagenry report to sources of Siena Nacimiento and viciniw, New the Bureau of lndian Atrairs,134 pi. Mexico: New Mexico Bureauof Mines and iVineral Read, C. 8., Duffner, R. T., Wood, G. H., and Zapp, Resources,Memoir 42, pp 49-53 fl

Nau Mexico Geology February 7991 27