area. The interval transit time decreases with ry may lead to better understanding of long- increasing burial depth according to a com- lived lithospheric-scale structures and their Abstracts paction curve that has to be calibrated for influence on igneous and tectonic activity. each unit examined. Rock units that are at a depth shallower than their maximum burial GEOLOGY AND GEOCHEMISTRY OF PROTEROZOIC GRANITIC AND NMGS spring meeting depth will have a lower-than-expected inter- val travel time. Approximately 50 sonic logs MAFIC ROCKS IN THE REDROCK The New Mexico Geological Society annual from southeast Colorado and northeast New AREA, NORTHERN BURRO MOUN- spring meeting was held on April 7, 2000, at Mexico have been digitized, and estimates of TAINS, GRANT COUNTY, NEW MEXI- New Mexico Institute of Mining and the amount of erosion have been determined. CO; A PROGRESS REPORT, by Virginia Technology, Socorro. Following are the The amount of erosion in southeast Colorado T. McLemore, [email protected], New abstracts from all sessions given at that meet- predicted from this analysis ranges from ~3 Mexico Bureau of Mines and Mineral ing. km along the Sangre de Cristo Mountain Resources, New Mexico Institute of Mining and Technology, Socorro, NM Index front to 0.8 km near the Colorado–Kansas State line. 87801; O. Tapani Ramö and Paula J. Kosunen, Session 1—Tectonics, geochemistry, and volcanology Geology Department, P.O. Box 11, FIN- p. 37 PROTEROZOIC EVOLUTION OF THE 00014 University Helsinki, Finland; Matt Session 2—Permian–Pennsylvanian stratigraphy and ZUNI MOUNTAINS, NEW MEXICO: Heizler, New Mexico Bureau of Mines and tectonicsp. 39 PERIDOTITES, TONALITES, RHYO- Mineral Resources, New Mexico Institute Session 3—Hydrogeology and geomorphology p. 41 LITES, SHEAR ZONES, AND A REAC- of Mining and Technology, Socorro, NM Session 4—Geology of the Santa Fe region p. 42 TIVATION HISTORY THROUGH THE 87801; Ilmari Haapala, Geology Depart- Session 5—Paleontology p. 44 PRESENT, by Diana Strickland, ariel23@ ment, P.O. Box 11, FIN-00014 University Poster session p. 47 unm.edu, Karl E. Karlstrom, and Jane Selver- Helsinki, Finland; and Christopher McKee, stone, Department of Earth and Planetary New Mexico Bureau of Mines and Mineral Sciences, University of New Mexico, Albu- Resources, New Mexico Institute of SESSION 1—TECTONICS, GEOCHEMISTRY, AND querque, NM 87131 Mining and Technology, Socorro, NM VOLCANOLOGY The Zuni Mountains offer a rare Precambrian 87801 exposure into both the Jemez lineament and A complex Proterozoic terrain in the north- the basement of the Colorado Plateau. ern Burro Mountains consists of metamor- PATTERNS OF CENOZOIC DENUDA- Proterozoic rocks of the Zuni Mountains are phic rocks (Bullard Peak and Ash Creek TION ON THE SOUTHERN HIGH dominantly meta-igneous and can be divid- Series, 1,550–1,570 Ma, U/Pb) that are PLAINS, by Marta J. Hemmerich and Shari ed into three suites: (1) tonalite/granodiorite intruded by granitic and mafic rocks. The A. Kelley, Department of Earth and Envir- with mafic enclaves, (2) peridotite that is granitic rocks include (1) Burro Mountain onmental Science, New Mexico Institute of either a crustal cumulate or an exotic slice of granite (oldest, ~1,445 Ma, U/Pb), (2) gneis- Mining and Technology, Socorro, NM mantle, (3) quartz monzonite and rhyolite sic granite/granodiorite (~1,380 Ma, K/Ar), 87801 that represent shallow-level magmatism at (3) Jack Creek rapakivi granite (1,220.9 ± 3.5, Spatial and temporal patterns of denudation ca. 1.65 Ga (Bowring and Condie, 1982). The 1,198 ± 4.7 Ma, 40Ar/39Ar), (4) Redrock gran- on the southern High Plains of northeastern peridotite occurs as an elongate lens with ite (1,210 ± 5, 1,204.8 ± 12 Ma, 40Ar/39Ar; New Mexico, southeastern Colorado, the sheared margins that was metamorphosed 1,328 ± 58 Ma, Sm/Nd isochron), (5) fine- Texas panhandle, and western Oklahoma are and hydrothermally altered. The sheared grained alkali-feldspar and biotite granite constrained using apatite fission-track (AFT) margins of the body and the absence of asso- dikes, (6) rhyodacite/dacite porphyry dikes, thermochronology, heat flow, and sonic well- ciated mafic rocks imply tectonic emplace- and (7) pegmatite dikes (youngest). The log velocity studies. AFT and modern tem- ment prior to intrusion by the quartz mon- Redrock granite consists of four textural and perature data are combined to estimate the zonite although distance of transport is compositionally distinct phases (biotite- timing and the magnitude of cooling due to unconstrained. hornblende, hornblende, K-feldspar, and denudation on the High Plains. AFT analysis The Zuni Mountains have a remarkable miarolitic biotite granites). Approximately 50 of core samples from five deep oil wells in history of igneous and tectonic activity: Arc small anorthosite xenoliths (1,216.9 ± 5.3, the area suggest that the base of the apatite magmatism (likely 1.75–1.7 Ga), tectonic 1,228.5 ± 4.5 Ma, 40Ar/39Ar; 1,326 ± 830 Ma, partial annealing zone (PAZ) is preserved in emplacement of the sheared peridotites, and Sm/Nd isochron) are scattered in a north- the subsurface in two of the wells. The depth the intrusion 1.65 Ga granites and rhyolites east-trending zone throughout the miarolitic of the base of the PAZ below the ground sur- was followed by a younger shearing event. biotite granite. K-rich minette (1,420.5 ± 4.5 face is tabulated below: This shear zone trends west–northwest for Ma, 40Ar/39Ar; 1,135 ± 71 Ma, Sm/Nd iso- ~10 km, dips 60° south, and bends to the chron) occurs as coeval isolated enclaves, <1,230 m east-central north–northeast with a southwest-plunging New Mexico swarms of enclaves, and synplutonic dikes mineral-elongation lineation. Shear sense is within the Jack Creek rapakivi granite. (1 Latigo Ranch C) extensional (top to the southwest) often with ~825 m northeastern ~2–3 km Diabase/gabbro/diorite stocks and dikes a dextral component and occurred at temper- intruded the metamorphic and granitic New Mexico denudation atures between 400° and 500°C. An unfoliat- (Logan) rocks. The age relationships of the granites ed, megacrystic granite (likely 1.4 Ga) and minettes remain unclear and will hope- <1,800 m Oklahoma panhandle intrudes this package and is bordered by dia- (Stonebraker 1-AP) fully be resolved by additional U/Pb dating base dikes (likely 1.1 Ga) along northwest- 40 39 <3,390 m Texas panhandle of zircons. The number of Ar/ Ar age trending faults. Cambrian syenites and fluo- dates clustering about 1,200 Ma strongly sug- (Hobart Ranch 1-21) rospar veins (age unknown) are also present. ~3,074 m Anadarko Basin, ~1–1.5 km gests that a heating event or uplift occurred The area was a northwest-trending uplift dur- at that time. Geochemical and isotopic data Oklahoma denudation ing the Ancestral Rocky Mountain orogeny (Payne 1) indicate that the Redrock granite, anorth- and during the Laramide orogeny, indicating osites, Jack Creek rapakivi granite, Burro long-term Phanerozoic buoyancy. Cenozoic The AFT cooling age just beneath the Mountain granite, and metamorphic rocks volcanism produced the Mt. Taylor volcanics were derived from different protoliths. The break-in-slope on the age-depth plot is ~27 and the Zuni–Bandera basaltic fields (that Ma in northeast New Mexico and ~38 Ma in anorthosites and diabase probably tapped a contain mantle xenoliths). Both belong to the moderately depleted mantle source. The Jack the Anadarko Basin. northeast-trending Jemez lineament that is The interval transit time digitized from Creek rapakivi granite was presumably underlain by low velocity, (hot) mantle. derived from a source characterized by sub- sonic logs can be used as an independent Documentation of the Zuni Mountain’s histo- measure of the amount of denudation in an tle, long-term LREE enrichment, whereas

MayMay 2000 NEW MEXICO GEOLOGY 37 that of the Redrock granite pluton was slight- TALS OF THE BISHOP AND BAN- cult scenario to physically reconcile. Clearly ly depleted. Both were clearly more juvenile DELIER MAGMA SYSTEMS, by Jeffrey the 3.70 ± 0.16 Ma age of the Bishop Tuff in (Nd model ages ~1,600 Ma) in nature than A. Winick, [email protected], Department addition to the respective 15.92 ± 0.87 Ma the metamorphic rocks of the region (Nd of Earth and Environmental Science, New and 11.41 ± 0.16 Ma ages for the lower and model ages ~1,900 Ma) and may include a Mexico Institute of Mining and upper Bandelier Tuffs are erroneous within significant Middle Proterozoic mafic lower Technology, Socorro, NM 87801; and Nelia the context of all known physical and geo- crust/subcontinental lithospheric mantle W. Dunbar and William C. McIntosh, New logical constraints on these magma systems. component. Mexico Bureau of Mines and Mineral We interpret this data as direct evidence for Resources, New Mexico Institute of 40 40 39 the presence of ArE and suggest that the AR/ AR GEOCHRONOLOGY OF THE Mining and Technology, Socorro, NM results of Van den Bogaard and Schirnick OCATE VOLCANIC FIELD, NORTH- 87801 (1995) are not geologically meaningful. As a CENTRAL NEW MEXICO, by Brian Olm- Residence timescales of silicic magma cham- result of this work, existing models of upper sted and William C. McIntosh, Department bers in the Earth's crust are poorly known. crustal magma residence times may need to of Earth and Environmental Science, New Some recent determinations of these time- be revised. Mexico Institute of Mining and Techno- scales, based on 40Ar/39Ar analysis of quartz- logy, Socorro, NM 87801 hosted melt inclusions, may be flawed due to QUARTZ XENOCRYSTS IN A HIGH-SILI- 40 39 Preliminary Ar/ Ar dating of the Ocate 40 CA RHYOLITE MELT: THE EL CAJETE the problem of excess argon ( ArE) in volcanic field along with previous K–Ar dat- trapped melt. In order to quantitatively PUMICE, JEMEZ MOUNTAINS, NEW MEXICO, by M. G. Snow, [email protected], ing reveals an eruptive history spanning assess the influence of 40Ar on estimated E and J. N. Gardner, Los Alamos National 0.8–8.2 Ma. The Ocate volcanic field lies in magma-chamber ages, we sampled melt- Laboratory, Los Alamos, NM 87545 north-central New Mexico along the Jemez inclusion-bearing quartz (MIBQ) from plin- Quartz xenocrysts with granular, green halos lineament just east of the Rio Grande depres- ian pumice deposits of the Bishop Tuff (0.76 are common in the rhyolitic El Cajete pumice, sion within the transition zone between the ± 0.01 Ma) in Long Valley, California, and the Jemez Mountains, north-central New Great Plains and the Rocky Mountain phys- lower (1.61 ± 0.01 Ma) and upper Bandelier Mexico. Compositional and textural analysis iographic provinces. The field is a series of Tuffs (1.22 ± 0.02 Ma) from the Jemez of augite in the reaction rims suggests that late Miocene–Pleistocene basaltic to dacitic Mountains west of Los Alamos, New Mexico. the quartz and augite coronas resulted from flows whose physiographic expressions Three types of glass are observed in the multiple mafic-felsic mingling events. roughly reflect their ages, where the oldest MIBQ. First, non-vesicular glass adhered to SEM examination using backscattered flows cap the highest mesas and younger the outside of the crystal; second, hourglass σ electron imaging revealed sparse-to-moder- flows cap lower mesas. Precision (at ± 2 ) on inclusions (inclusions that are not fully ate amounts of augite oriented radially with previous conventional K–Ar dates for flows enclosed within the crystal and may have respect to the fractured and “crackled” from the Ocate field are typically ± 3–9%, been in free exchange with atmosphere at the quartz grains. Quartz grains were embedded whereas the precision on individual ages time of eruption); and third, fully trapped 40 39 in a coarsely vesicular pumice halo about using the Ar/ Ar dating technique is typi- melt inclusions. Each sample was prepared 40 39 1 mm wide, which was in turn surrounded cally ± 0.5–1.5%. Thus, the Ar/ Ar dating for analysis in three ways: one aliquot of by finely vesicular pumice. Petrographic technique has the potential to resolve past sample was left untreated, a second aliquot study showed that the quartz grains were eruptive events differing in age by 100,000 was run in a mill grinder for 1 hr, and a third rounded and embayed and occasionally years or less. aliquot was treated with hydrofluoric acid polycrystalline. Augite coronas were discon- The volcanic evolution began with discrete (HF) for 1 hr. Backscattered electron imaging tinuous and separated from the quartz by a eruptive pulses focused in the northern and with the electron microprobe shows that in glassy interval but always occurred within central portions of the field from 8.2 to 5.5 the first case, all three glass populations are the coarsely vesicular halo. Individual augite Ma. From 5.5 to 2.2 Ma activity increased and present, that mill grinding removes adhered grains in the corona were generally euhedral; was less episodic throughout the field. A sec- glass, and that the HF treatment leaves only however, single crystals and patches of fine- ond stage of discrete eruptive pulses then fol- fully trapped inclusions. ly granular augite occurred in the ground- lowed from 2.2 to 0.8 Ma focused in the cen- Aliquots of MIBQ were step heated with a mass. Two varieties of feldspar phenocryst tral and southern portion of the field includ- 40 W CO laser and measured for argon iso- 2 were present; wormy and fritted sodic pla- ing the monogenetic eruption of Maxson topes at the New Mexico Geochronology gioclase, some with clear exterior rims, and crater at 1.58 ± 0.08 Ma. Four flows emanat- Research Laboratory. 40Ar/39Ar ages consis- largely pristine calcic plagioclase. Some ing from Maxson crater were stratigraphical- tantly increase with decreasing K/Qtz ratios feldspar phenocrysts had inclusions of ly sampled at the Mora/Canadian conflu- (attributed to the removal of rhyolite glass as brown glass. Groundmass minerals were ence, and all samples agree within error of observed on the electron microprobe). MIBQ pyroxene, magnesian olivine, Fe–Ti oxides, each other and within error of samples col- from the Bishop Tuff yields a plateau age as and euhedral amphibole, sometimes jacket- lected proximal to the vent. old as 3.70 ± 0.16 Ma, with the oldest ages 40 39 ing biotite. The new precise Ar/ Ar dates agree calculated from HF-treated samples, which Based on our results, we concluded that El within error with previously published K–Ar again contain only trapped melt inclusions. Cajete quartz was xenocrystic in a more dates for the same flows. Of the fifty samples Plateau ages for MIBQ from the lower and mafic magma and augite coronas grew in dated thus far, the vast majority display well- upper Bandelier Tuffs are as old as 15.92 ± response to diffusion-limited reactions in dis- behaved age spectra and minimal presence 0.87 Ma and 11.41 ± 0.16 Ma, respectively, 40 39 solution boundary layers at crystal margins. of excess Ar, Ar* loss, and ArK recoil. again with the oldest ages representing the The mafic magma provided the thermal Duplicate analyses performed on aliquots of HF-treated samples. This data suggest that energy necessary to induce partial melting of a given sample and of samples collected from significant quantities of 40Ar are present in E a granodiorite (reported by Gardner et al. separate flows proximal and distal from the trapped melt inclusions, with lesser amounts 1995, to be the parent of the El Cajete) and, as vent show excellent within-sample and hosted by the hourglass inclusions and non- limited mixing occurred, quartz xenocrysts between-samples repeatability and agree- vesicular glass coatings. ment with stratigraphy. Geochronological 40 39 and coronas were assimilated into a new, Previous studies have cited Ar/ Ar sin- more silicic, melt. During eruption of the El studies of the neighboring Raton and Taos gle-crystal laser-fusion isochron ages of 1.93 volcanic fields also show a similar range in Cajete pumice the quartz xenocrysts acted as ± 0.12 Ma on Bishop Tuff MIBQ as indepen- nucleation sites for vesiculation, and thus the age of volcanic activity and an increased dent evidence for a ~2 Ma Rb–Sr magma dif- period of activity from ~2.5 to 4.5 Ma. coarsely vesicular halo formed. Continued ferentiation event (Christensen and DePaolo, rapid vesiculation during eruption probably MELT INCLUSION HOSTED EXCESS 1993; Christensen and Halliday, 1996; Van dispersed many of the augite crystals into the 40 den Bogaard and Schirnick, 1995). Such an ARGON ( ArE) IN THE QUARTZ CRYS- groundmass. TALS OF THE BISHOP AND BAN- event necessitates a long-lived (>1 Ma) ther- mally equilibrated magma chamber; a diffi- THE CEMENTATION AND HYDROGE-

3388 NEW MEXICO GEOLOGY May 2000 OLOGY OF TWO FOSSIL GEOTHER- describes the geochemistry of CR, PR, and the earthquake on the Sandia and Rincon faults, MAL SYSTEMS HOSTED WITHIN THE underlying, unaltered host wall rock (WR). which are located adjacent to Albuquerque CAMP RICE FORMATION AT BOX The host carbonate (Permian Capitan reef and dip beneath the city. CANYON AND SAN DIEGO MOUN- complex; dominantly dolomite and calcite) We included a total of 55 late Quaternary TAIN, DOÑA ANA COUNTY, NEW contains up to 2.3% insoluble residue. The faults in the probabilistic-hazard analysis. MEXICO, by Drue E. Roberts, Department insoluble residue consists of quartz and illite. These faults were characterized in terms of of Geological Sciences/MSC 3AB, New The PR is dominantly carbonate with virtual- their rupture behavior, geometry, segmenta- Mexico State University, Las Cruces, New ly no insoluble residue. The chemical compo- tion, Mmax, and slip rates. Best estimate Mmax Mexico 88003 sition of CR is quite different. Carbonates values ranged from M 6.1 to 7.4 and slip rates Fossil geothermal systems at Box Canyon and quartz are either absent or limited, and from 0.01 to about 0.15 mm/yr. An areal and San Diego Mountain in southern New high concentrations of manganese and iron source zone and Gaussian smoothing of the Mexico are hosted within the Plio–Pleisto- are present. There is a good correlation historical seismicity were also included in the cene Camp Rice Formation. The Box Canyon between color and chemical composition: probablistic-hazard analysis to account for geothermal system is focused around an colors grade from white through pink, red- the hazard from background earthquakes (M 1 east-west trending, fractured Oligocene-age brown, to black. Iron is associated with red, ≤ 6 ⁄2). rhyolite dike, while the San Diego Mountain red-brown, brown, and black residues (40, Amplification factors were calculated to system is exposed along an arroyo escarp- 50, 80, and 25 wt% oxide, respectively). incorporate site response into the hazard ment near the Jornada fault zone. The Camp Manganese is associated with the black maps. Amplification factors were developed Rice was mapped into lithofacies using grain residues (up to 20 wt% oxide). Utilizing man- using only simple generic geologic-site cate- size, depositional environment, and sedi- ganese concentrations in host rock and corro- gories (e.g., hard rock, stiff soil, etc.) because mentary structures. The geothermal mineral- sion residues, mass balance calculations indi- very little subsurface geologic and geotechni- ization of the Camp Rice is classified into cate concentration factors of 50 times by cal data are available. Factors were calculated pore cement assemblages based on the dom- weight, but the low density of CR translates using a numerical ground-motion-modeling inant pore cement and emplacement within to a thickness of 2.2 cm of host rock required approach coupled with an equivalent–linear specific zones of the lithofacies. The Box for 1 cm of residue. The CR is too chemically methodology. This modeling approach and Canyon pore-cement assemblages are: sili- distinct from the WR insoluble residue to empirical attenuation relations appropriate cate-clay, iron oxide-calcite-silicates, calcite have formed simply through dissolution of for extensional tectonic regimes were used to dominant, and iron oxide-calcite. The major- host carbonate during cave formation or later compute the scenario and probabilistic ity of the alteration at Box Canyon is in the chemically driven processes. We propose ground motions. form of poikilotopic calcite cement in coarse- that the CR has built up over long time peri- grained fluvial sandstones. These calcite- ods through microbially assisted dissolution cemented sandstones extend up to 1.5 km and leaching of underlying host carbonate southwest from the rhyolite dike. The San and microbial oxidation of reduced iron and SESSION 2—PERMIAN–PENNSYLVANIAN Diego Mountain pore-cement assemblages manganese. STRATIGRAPHY AND TECTONICS are: minor quartz, hematite-silicate, hema- EARTHQUAKE GROUND SHAKING tite-calcite-silicates, silicate dominant, and PETROLEUM SYSTEMS IN LATE PALE- HAZARD MAPS FOR THE ALBU- potassic-silicate. The silicate cementation is OZOIC ELEVATOR BASINS, SOUTH- QUERQUE–BELEN–SANTA FE, NEW more extensive within the fault zone and ERN ANCESTRAL ROCKY MOUN- MEXICO, CORRIDOR, by I. Wong, S. extends laterally outwards within the coarse TAINS, by Ronald F. Broadhead, New Olig, M. Dober, D. Wright, P. Thomas, fluvial sandstone. The majority of the cemen- Mexico Bureau of Mines and Mineral Seismic Hazards Group, URS Greiner tation extends less than 0.5 km away from Resources, New Mexico Institute of Woodward Clyde, 500 12th Street, the fault zone. The Box Canyon and San Mining and Technology, Socorro, NM Oakland, CA 95707; and W. Silva, N. Diego Mountain geothermal systems were 87801 Gregor, and S. Li, Pacific Engineering & quite distinct in their chemistry and fluid The Tucumcari, Estancia, Carrizozo, and Analysis, El Cerrito, CA 94530 movement. The Box Canyon outflow plume Vaughn Basins are located in northeast and The majority of New Mexico’s population is was calcite saturated and spread southwest central New Mexico. These basins began to located along the Rio Grande corridor that for up to 1.5 km from the source; whereas the form during the Atokan (Early Pennsylvan- extends from Belen in the south to Española San Diego Mountain outflow plume reached ian) and saw continued tectonic develop- in the north and which includes the cities of a higher temperature and was silica-saturat- ment through the Wolfcampian (Early Albuquerque and Santa Fe. The corridor is ed, spreading less than 0.5 km from the Permian). They are tectonic elements of the situated within the Rio Grande rift, a tecton- Jornada fault. southern Ancestral Rocky Mountains and ically, volcanically, and seismically active fea- were formed along the flanks of the late GEOCHEMICAL INVESTIGATIONS AT ture in the western U.S. Although no histori- Paleozoic Sierra Grande and Pedernal uplifts CARLSBAD CAVERNS NATIONAL cal earthquake larger than M 6 has occurred, in a strike-slip setting. During the late PARK: IMPLICATIONS FOR THE paleoseismic investigations indicate that pre- 1 Paleozoic, the Precambrian cores of these ORIGIN OF CAVE CORROSION historic surface-faulting earthquakes of M 6 ⁄2 uplifts were exposed and were the source of RESIDUE, by Kathleen E. Dotson, Rachel T. and greater occurred on many faults sediments deposited in the adjoining basins. Schelble, Michael N. Spilde, and Laura J. throughout the rift. The Tucumcari, Estancia, Carrizozo, and Crossey, Department of Earth and In an effort to portray the ground-shaking Vaughn Basin areas were dominated by shal- Planetary Sciences, University of New hazards in the Albuquerque–Belen–Santa Fe low-shelf deposition. Along the boundaries Mexico, Albuquerque, NM 87131 corridor, we have developed a set of deter- of the adjoining uplifts, however, these Lechuguilla and Spider caves provide the set- ministic-earthquake-scenario and probabilis- basins have component elevator basins. ting for a multidisciplinary study of geo- tic-microzonation maps. These GIS-based Elevator basins are long, narrow, and struc- chemical and microbial interactions in an maps display color-contoured ground turally deep troughs bounded by high-angle extreme environment (dark, nutrient-limited, motion values in terms of peak horizontal faults. They are either elongate parallel to the carbon-poor). Corrosion residue (CR) is a acceleration and horizontal spectral accelera- axes of the adjoining uplifts and separate the multi-colored secondary mineral deposit tions at 0.2 and 1.0 sec periods. The maps uplifts from areas of shelf deposition or they associated with a diverse microbial commu- depict surficial ground shaking and thus cut into the flanks of these uplifts. The nity that includes iron and manganese oxidiz- incorporate the site-response effects of soils bounding faults, of Early Pennsylvanian to ers. CR occurs as coatings (up to 2 cm thick) and near-surface unconsolidated sediments. Early Permian age, have vertical offsets that overlying a layer (from 2 to ~10 cm) of altered The probabilistic maps are for the two return can exceed 5,000 ft. Basin width can range carbonate host rock (termed “punk rock” or periods of building-code relevance, 500 and from 5 to 15 mi, and basin length can range PR) on walls of the caves. This study 2,500 yrs. The scenario maps are for a M 7 from 20 to 50 mi.

MayMay 2000 NEW MEXICO GEOLOGY 39 Early to Late Pennsylvanian strata in these The large number of parasequences suggest Pennsylvanian lithostratigraphic nomencla- elevator basins contain mature petroleum relative sea-level changes on the order of ture in New Mexico has developed in piece- source rocks. Deposition was dominated by from 104 to 105 yrs. meal fashion over the past century and in shales and sandstones derived from erosion some cases is inconsistent, redundant, or oth- of Precambrian rocks exposed on the adja- erwise inappropriate. The interplay between cent uplifts. Total organic carbon (TOC) can TYPE SECTIONS OF THE UPPER PENN- paleogeography, tectonics, eustasy, and cli- exceed 9% in dark-gray to black shales. Kero- SYLVANIAN BRUTON AND BURSUM mate has produced depositional sequences of gens range from gas-prone woody types to FORMATIONS, SOCORRO COUNTY, significant variability from place to place, but oil-prone amorphous types. Greater depth of NEW MEXICO, by Spencer G. Lucas, New the occurrence of most Pennsylvanian burial in the elevator basins as compared to Mexico Museum of Natural History and sequences in isolated fault-block ranges has the adjoining uplifts and shelf areas has Science, 1801 Mountain Rd. NW, Albu- emphasized apparent differences between resulted in increased levels of thermal matu- querque, NM 87104; Barry S. Kues, Depart- local sequences rather than the broader ration within the basins. Shales within many ment of Earth and Planetary Sciences, depositional patterns that tie them together. of these elevator basins are within the oil University of New Mexico, Albuquerque, Review of Pennsylvanian stratigraphy window, and shales on the adjoining shelves NM 87131; G. L. Wilde, 5 Auburn Court, throughout New Mexico leads to the follow- are less mature. Hydrocarbons generated Midland, TX 79705; and K. Krainer, Uni- ing recommendations: (l) use of the term within the basins may be trapped within versity of Innsbruck, A-6020, Innsbruck, Magdalena Group should be discontinued, basinal sandstones but may have also Austria as it has been applied in so many contradic- migrated upward along the bounding faults Thompson (1942, NMBMMR Bulletin 17) tory ways as to be meaningless; (2) the and into strata on the adjacent shelves and named the Bruton Formation for a 35-m- Madera Formation is best regarded as a uplifts. thick section of mixed marine and nonmarine group wherever it occurs. It consists of two strata between Virgilian limestones below or three major subdivisions (formations), and Wolfcampian strata above in the north- including a lower massive cherty limestone 1 REGIONAL ANALYSIS OF THE DEPOSI- ern Oscura Mountains (SE ⁄4 sec. 32 T5S R6E). unit of Desmoinesian age, reflecting wide- TIONAL ENVIRONMENTS OF THE Although Thompson’s description met all spread carbonate shelf environments, fol- LOWER PERMIAN YESO AND GLORI- criteria for introduction of a valid lithostrati- lowed by marine environments that were ETA FORMATIONS, by Philip A. Dinter- graphic unit, Wilpolt et al. (1946, USGS OM- increasingly, though not everywhere evenly, man and Greg H. Mack, Department of Geo- Map 61), in a map legend, renamed essential- affected by influx of siliciclastic sediments logical Sciences, New Mexico State Uni- ly the same lithostratigraphic unit Bursum derived from increased tectonic activity in versity, Las Cruces, NM 88003 Formation, with a stratotype only 15 km several major local uplifts. This upper, 1 The Lower Permian (Leonardian) Yeso away (SE ⁄4 sec. 1 T6S R4E). Although Bruton Missourian-Virgilian interval is still dominat- Formation in New Mexico consists of up to Formation had priority, most subsequent ed by limestones (mainly thinner and 300 m of interbedded eolian, sabkha, lagoon- workers, especially USGS mappers, used the noncherty) but with clastic beds approaching al, and shallow-marine siliciclastic and car- name Bursum Formation. or locally surpassing the limestones in total bonate rocks arranged into transgressive and The original type sections of the Bruton thickness. Locally, at the top of the Madera overlying regressive successions. Environ- and Bursum Formations stratigraphically Group, a third formation, in which red, pur- ments change from predominantly eolian in overlap but were not exactly equivalent. The ple, and green nonmarine clastics predomi- the north to more mixed marine and eolian type Bruton Formation of Thompson, who nate over thin marine limestones, can be rec- throughout the remainder of the state. assigned it a late Virgilian age, is overlain by ognized (e.g., Red Tanks and Bursum Lagoonal gypsum beds become increasingly a 5-m-thick limestone that contains the low- Formations); (3) formal names, where need- common in the east-central part of the state. est local occurrence of the Wolfcampian ed, should be applied to these Madera Group A middle limestone member is present fusulinid Schwagerina. Thompson did not formations, to replace such informal terms as throughout most of the state and marks the assign this limestone to a formation (reflect- "lower gray limestone" and "upper arkosic time of maximum transgression. The overly- ing his emphasis on biostratigraphy in defin- limestone" members. The earliest valid for- ing Glorieta Formation consists of up to 60 m ing the Bruton Formation), but Wilpolt et al. mal names for these units are Gray Mesa and of marine and eolian quartzose sandstone included it in the uppermost Bursum Forma- Atrasado, first applied in the Lucero uplift representing the onset of another transgres- tion. Our fieldwork at the Bruton Formation area; (4) the Madera Group can be recog- sive event. The Glorieta is no longer a recog- type section has identified 28 m of mixed nized from the southeastern Sangre de Cristo nizable map unit in the southern part of the marine/nonmarine strata above the Schwa- Mountains southward along the north and state. gerina-bearing limestone and beneath the west margins of the Orogrande Basin, to the Much of the Yeso and Glorieta Formations Abo Formation base. Caballo and possibly Robledo Mountains; (5) are arranged into 2–10-m-thick parase- At Wilpolt et al.’s type section, the Bursum the Gray Mesa and Atrasado Formations can quences composed of mixed marine and Formation overlies a 29-m-thick interval of be recognized from the Sierra Nacimiento to nonmarine sediments. In the Yeso Formation, siliciclastic red beds they identified as a the Caballo Mountains; in some areas these eolian beds are characterized by orange, very tongue of the Abo Formation, an unsupport- names should replace local nomenclatures; fine grained sandstones that display climb- able correlation. We therefore redefine the (6) current formation nomenclature in the ing wind ripples deposited either on a sand Bruton and Bursum stratotypes to extend San Andres, Sacramento and Franklin sheet or on the landward side of a coastal from the first siliciclastic red beds above Mountains is appropriate; (7) some portions salina. Intertidal and supratidal dolomites Madera Group limestones to the highest of the largely ignored but validly established are characterized by fenestral fabric, desicca- marine limestone below Abo Formation red lithostratigraphic nomenclature of Thomp- tion cracks, and stromatolites, although some beds. This defines an 85–100-m-thick map- son (l942) could be usefully employed as dolomites lack these features and may be pable unit of mixed nonmarine red beds and local member names within the broadly con- lagoonal in origin. Gypsum beds consist of marine limestones and shales between the ceived formations noted above; and (8) cm-scale white and gray or black laminae Madera and Abo that should be called names for subsurface Pennsylvanian litho- and were deposited in hypersaline lagoons, Bursum Formation, in accordance with long- stratigraphic units in New Mexico should be whereas normal-marine conditions are repre- standing usage. the same as those applied to surface expo- sented by fossiliferous limestones. The Glori- sures, rather than (current practice) group eta Formation is characterized by white fine- RECOMMENDATIONS FOR REVISION names derived from unrelated sequences in grained quartzose sands. Sedimentary fea- central Texas. tures are often obscured, but the formation OF PENNSYLVANIAN LITHOSTRATI- contains eolian climbing ripples, with marine GRAPHIC NOMENCLATURE IN NEW MEXICO by Barry S. Kues, Department of conditions indicated by wave-oscillation rip- SESSION 3—HYDROGEOLOGY AND Earth and Planetary Sciences, University ples, planar bedding, and trough crossbeds. GEOMORPHOLOGY of New Mexico, Albuquerque, NM 87l3l

4400 NEW MEXICO GEOLOGY May 2000 A SOIL-GEOMORPHOLOGIC INVESTI- including 3 yrs of detailed hydrochemistry of sedimentary records were recovered from GATION OF THE UPPER TRIBUTARIES work. The Rio Calaveras aquifer is ideal for alpine lakes and bogs trapped behind OF THE RIO CEBOLLA DRAINAGE the examination of the interannual response Pinedale-age moraines within the Stewart BASIN, JEMEZ MOUNTAINS, NEW of redox processes in a dynamic near-surface Lake area using a Livingston soft-sediment MEXICO, by Tim Gere, [email protected], environment because (1) the geochemistry piston corer. These cores are typically com- Department of Earth and Planetary Scien- shows an interannual response, (2) a large posed of an upper peat-rich interval under- ces, University of New Mexico, Albuquer- geochemical and hydrological data base has lain by a thin layer of coarse detrital sand que, NM 87131 been assembled (over 60,000 data points), containing a basal charcoal horizon, followed The Rio Cebolla drainage basin is a relatively and (3) it is a pristine stream environment. by a thick sequence of lake clays that become large basin (area = 120 km2) located in the Floodplain and transect wells, along with finely laminated at the base of the record. In western part of the Jemez Mountains of surface-water collection, are the primary the deepest series of cores, a thin basal inter- northern New Mexico, between the Valles sampling sources at Rio Calaveras. These val of rock flour-rich clay is present, suggest- caldera to the east and the Sierra Nacimiento three main sampling areas add up to a com- ing deposition coincident with proximal to the west. This research focuses on the char- bined total of 54 sampling locations. The var- glacial ablation. acterization of the spatial and temporal vari- ious geochemical parameters gauged in the Radiocarbon analysis of charcoal, plant ations in the geomorphology, sedimentary field and in the laboratory include major ion macrofossils, and bulk sediments within deposits, and associated soils in the two main analysis (including iron and manganese), recovered cores provides age control on the forks of the Rio Cebolla drainage basin: pH, dissolved oxygen, and oxidation-reduc- rates of deposition in these systems. In addi- Calaveras Canyon and the upper Rio Cebolla tion potential (ORP). Geochemical parame- tion, total organic carbon, magnetic suscepti- drainage basin. These tributary basins are ters and hydrologic data (stream discharge, bility, and sedimentologic analysis are being both underlain by the Bandelier Tuff and are water-table elevation, and water-table tem- conducted on the recovered cores. Prelim- nearly identical in drainage area, orientation, perature fluctuations) are compared in this inary results show excellent correlation elevation, and vegetation type and due to the study for sitewide interannual responses. between these different proxies and the ulti- close proximity of the basins (trunk streams The water table fluctuates up to 0.7 m during mate timing of significant climatic perturba- are only about 1.5 km apart) it is reasonable an annual cycle with a maximum reached tions in this region over the last 5,000 yrs, to assume that they have been subject to the during spring snowmelt and a minimum and possibly the last 14,000 yrs. The most sig- same climate and climate changes. The during winter baseflow conditions. During nificant depositional change in the core drainage patterns and other important geo- the periods of high discharge, dissolved oxy- (peat/clay transition) is coincident with the morphic features of the basins’ valley bot- gen in the system is at a maximum (2–6 formation of the dated Neoglacial moraine toms, however, are markedly different. mg/L). Elements such as iron and man- and a notable mid-Holocene wetting period Calaveras Canyon contains at least two pre- ganese are predominantly present at this in the Estancia Basin of central New Mexico. served stream terraces and has a well-devel- time in their oxidized states and are at mini- oped dendritic drainage pattern, while the mum concentrations in the ground water ESTIMATING HYDRAULIC PARAME- upper Rio Cebolla basin contains no pre- within the aquifer system. When baseflow TERS FROM WATER-LEVEL FLUCTUA- served terrace remnants and has a much conditions occur, iron and manganese are TIONS, by Stephen G. McLin, mclins@ more linear drainage pattern with limited reduced because dissolved oxygen within lanl.gov, Los Alamos National Laboratory, tributary branching. In addition to differ- the system is at a minimum. Concurrently P.O. Box 1663, MS-K497, Los Alamos, NM ences between basins, the geomorphic fea- with these conditions, these redox sensitive 87544 tures also vary within the valley bottom of elements become mobile in the system with In October 1992, the Los Alamos National Calaveras Canyon. The valley bottom of the concentrations of iron and manganese up to Laboratory began recording hourly water ephemeral portion of Calaveras Canyon con- 15 mg/L and 2 mg/L, respectively. Under- levels in numerous test wells that are com- tains two distinct, laterally continuous geo- standing the dominant hydrologic pulse pleted into the regional aquifer below morphic surfaces. The upper surface is a flu- (snowmelt), in relation to the interannual Pajarito Plateau. Daily water-level fluctua- vial terrace, located approximately 2.5 m variability and the geochemical effects, tions typically range from 0.25 to 0.50 ft or above the channel bed, and the lower surface allows the application of this knowledge to more with an instrument measurement error is the current floodplain, located about 0.5 m anthropologically perturbed systems. of ± 0.04 ft. These data are electronically above the channel bed. Bar-and-swale topog- available on the web (http://www. raphy and many surface boulders character- A LATE QUATERNARY CLIMATE RE- esh.lanl.gov/~esh18/teams/hydrology/Well ize the modern floodplain in this portion of CORD FROM ALPINE CATCHMENTS data.htm). In the frequency domain, these the canyon. In contrast, the floodplain in the IN THE SOUTHERN SANGRE DE fluctuations can be directly related to portion of Calaveras Canyon fed by perenni- CRISTO MOUNTAINS OF NORTHERN changes in barometric pressure and solar- al springs lacks bar-and-swale topography NEW MEXICO, by Jake Armour, jar- lunar Earth tides using spectral analysis. and is underlain by finer-grained deposits; [email protected], and Peter J. Fawcett, Here the familiar horizontal time axis on a also the 2.5-m terrace is not preserved in this Department of Earth and Planetary Scien- standard water-level plot is replaced by a lin- portion of the canyon. Dendrochronological ces, University of New Mexico, Albuquer- ear transformation to frequency. The vertical methods have been implemented in order to que, NM 87131 axis represents the Fourier transform of the assign minimum ages of relative stability to The southern Sangre de Cristo Mountains of autocovariance function computed from the surfaces present in Calaveras Canyon. northern New Mexico contain evidence of water-level measurements that are uniformly Preliminary data indicate a minimum age of Quaternary glaciation, including a distinc- distributed over time. The resulting spec- 500 yrs for the 2.5-m terrace and 130 yrs for tive set of late Holocene moraines in the Lake trum represents water-level departures from the modern floodplain. Katherine cirque of the Winsor Creek the mean expressed as a function of frequen- drainage basin. Previous work by Wesling cy. If water levels are affected by barometric INTERANNUAL GEOCHEMICAL VARIA- (1988) revealed a Neoglacial-age moraine in pressure fluctuations, then strong peaks at 1 TIONS OF A SHALLOW ALLUVIAL this cirque based on a basal radiocarbon date and 2 cycles per day (cpd) will be obvious. AQUIFER, by Richard M. Ortiz, orteaser@ of 3,600 y.b.p. Moraines range in age down- These peaks mimic those in the atmospheric- unm.edu, Laura J. Crossey, and Armand basin in the Stewart Lake area from Bull Lake pressure spectrum and are related to atmos- Groffman, Department of Earth and Plan- and Pinedale to latest Pleistocene and a pos- pheric solar heating. Other strong peaks that etary Sciences, University of New Mexico, sible Triple Lakes equivalent Neoglacial are related to synoptic-scale weather patterns Albuquerque, NM 87131 moraine in the Lake Katherine cirque. will also be apparent at frequencies below 0.5 Located in the Jemez Mountains of northern Alpine catchments such as lakes and bogs cpd. If water levels are affected by solar- New Mexico, Rio Calaveras is a first order are becoming an increasingly popular source lunar Earth tides, then additional strong montane stream with a shallow alluvial for obtaining high-resolution proxy data of peaks at 0.93, 1.00, 1.93, and 2.00 cpd will be aquifer system. Over the past 6 yrs the past climate change. In this study, a number apparent in water-level spectra. These fre- hydrogeology has been well documented,

MayMay 2000 NEW MEXICO GEOLOGY 41 quencies correspond to the O1 lunar diurnal, of saturation occurs in different rock units of subsurface information will improve our the K1 solar diurnal, the M2 lunar semi-diur- making up the regional aquifer, depending understanding of basin development and nal, and S2 solar semi-diurnal frequencies, on location. aquifer potential. This presentation will respectively. These influences arise from dis- LANL’s Groundwater Protection Program focus on the results of current mapping and tortions in the Earth's crust in response to calls for the drilling of 32 deep characteriza- subsurface interpretation within the follow- revolutional and rotational periodicities in tion wells across the laboratory area. ing Santa Fe area 7.5-min quadrangles: the Earth-moon-sun system. The overlap in Observations in wells installed under this Read, A. S., Rogers, J., Ralser, S., Smith, G., solar and atmospheric-pressure frequencies program through FY99 (wells R-9, R-12, R-15, and Bauer, P. W., 2000, Geology of the Santa at 1 and 2 cpd actually provides the basis for and R-25) have already prompted revision of Fe 7.5-min quadrangle, Santa Fe County, alternative models than can be used to esti- the conceptual hydrogeologic model for the New Mexico: New Mexico Bureau of Mines mate hydraulic transmitting parameters. area. These wells not only provide for better and Mineral Resources, Open-file Geologic These water-level data are analyzed in the definition of the extent and thickness of Map OF-GM 32, scale 1:12,000. frequency domain using models developed hydrostratigraphic units, but also suggest Read, A. S., Rogers, J., Ralser, S., Ilg, B., and by Hsieh et al. (1987) and Ritzi et al. (1991). that perched ground water is a more com- Kelley, S., 1999, Geology of the Seton While type curves can be used to estimate mon element of the hydrologic system at Village 7.5-min quadrangle, Santa Fe aquifer transmissivity (T) and storage coeffi- LANL than previously thought. County, New Mexico: New Mexico Bureau cient (S), the complex vector estimation crite- All four of the new deep wells encoun- of Mines and Mineral Resources, Open-file ria suggested by Ritzi et al. (1991) is much tered perched zones of saturation. In three of Geologic Map OF-GM 23, scale 1:12,000. more robust. These analyses demonstrate the wells, located in canyons (R-9, R-12, and (also, if time permits) that field values for T can generally be esti- R-15), the perched water was found in the Koning, D., and Hallett, B., 2000, Geology of mated with the atmospheric-pressure-varia- Cerros del Rio basalt interbedded with the the Turquoise Hill 7.5-min quadrangle, tion (APV) model. Depending on water-level Puye Formation but not various shallower Santa Fe County, New Mexico: New attenuation characteristics, we are occasion- units. Such units include the alluvium at R-9, Mexico Bureau of Mines and Mineral ally forced to use the solid Earth tide (SET) the alluvium and Guaje Pumice Bed at R-12, Resources, Open-file Geologic Map OF-GM test configuration. S values are typically and the alluvium and Cerro Toledo interval 41, scale 1:24,000. insensitive in both models. However, the at R-15. Saturated zones in these materials no procedure recommended by Bredehoeft doubt occur but must be ephemeral. The lack SUBSURFACE GEOLOGY OF THE (1967) can also be used to estimate S. Finally, of shallower perched water at R-15, drilled SANTA FE EMBAYMENT, NEW MEXI- the resulting estimates for T and S are com- on the southern edge of Mortandad Canyon, CO, by Philip R. Grant, Jr., zorroplata@ pared to results obtained from traditional further suggests that such saturation may be aol.com, Grant Enterprises, Inc., 9720-D pumping tests and some general conclusions restricted to the main axis of canyons and Candelaria Road, NE, Albuquerque, NM are developed. does not spread very far laterally. Static 87112 It is interesting to note that not all wells water levels measured at various depths dur- The Santa Fe embayment is a structural ele- display barometric pressure and Earth-tide ing the drilling of R-25, a mesa-top well on ment of the Rio Grande rift-related Española effects. For example, no shallow alluvial the western edge of the laboratory, confirm a Basin. Until the advent of rifting in late wells on Pajarito Plateau show these influ- downward vertical gradient in this suspected Tertiary, the Española Basin was essentially a ences. However, intermediate and deep recharge area. synclinal sag bounded locally by remnants of observation wells show barometric influ- These findings are of special interest for the Laramide orogeny’s Sangre de Cristo ences, while only about 20% of these deep ground water modeling and environmental- Mountains on the east and the Nacimiento wells also display tidal effects. This pattern restoration efforts in that they provide a bet- Mountains on the west. During Eocene, up to suggests a possible relationship between the ter understanding of possible movement of 4,700 ft of sediments of the Galisteo regional ground-water flow field and the contaminants to the deep regional aquifer Formation were deposited between these location of the well screen. that is tapped by water-supply wells in the uplifts. The region was modified in area. Oligocene time by the production and depo- CONCEPTUAL HYDROGEOLOGIC sition of as much as 2,000 ft of volcanic mate- MODEL FOR LOS ALAMOS—SOME rial of the Espinaso Formation, associated REVISIONS SUGGESTED BY DEEP SESSION 4—GEOLOGY OF THE with emplacement of intrusives within older DRILLING, by William J. Stone, wstone SANTA FE REGION rock units and uplift of a range of hills from @lanl.gov, Los Alamos National Labor- south of Cerrillos to north of La Cienega. atory/EES-5, P.O. Box 1663, MS-F649, Los Locally, the laccolithic Cerrillos Hills were PRELIMINARY RESULTS OF RECENT Alamos, NM 87545 responsible for deforming the pre-Oligocene MAPPING IN THE SANTA FE AREA, by Los Alamos National Laboratory (LANL) is Española Basin upward in its center, forming Adam Read, New Mexico Bureau of Mines situated on the Pajarito Plateau, a deeply dis- synclines on both sides. The eastern depres- and Mineral Resources, New Mexico sected expanse of volcanic ash and underly- sion became the Santa Fe embayment, and Institute of Mining and Technology, ing fill of the Española Basin. The geologic most of the western one foundered during Socorro, NM, 87801 column includes, in descending order, the Miocene rifting into a deep northern part of Detailed and current geologic information Bandelier Tuff, the Puye Formation, and the the Albuquerque Basin. remains important for understanding the Santa Fe Group, as well as basalts and the Rifting on a regional scale through central water resources of the Santa Fe area. It has Tschicoma Formation interbedded with the New Mexico began in early Miocene time, been almost four decades since the still often- Puye and Santa Fe. Ground water has been 20–25 million years ago. This intense tectonic referenced "Geology and Water Resources of encountered beneath the Pajarito Plateau in activity resulted in a flood of Tesuque the Santa Fe Area, New Mexico" (Spiegel and shallow and intermediate-depth perched Formation clastics that filled both deep and Baldwin, 1963, USGS Water-Supply Paper- zones of saturation as well as beneath the shallow depressions in and near the rift. The 1525) was published and over a decade more regional water table. Perched ground water northern Santa Fe embayment received more since fieldwork for most of the fine geologi- occurs in and between tuff subunits in the than 4,000 ft of these sediments, but the cal maps included in that volume was done. mesas, in alluvium beneath the canyon Tesuque Formation is missing or thin in The need for more current information is floors, and in the basalts interbedded with much of the southern embayment. Distribu- made more pressing as continued develop- the Puye and Santa Fe in both settings. tion of the intrusives that constructed the ment and population growth rely more heav- Ground water associated with the deep zone Cerrillos Hills during Oligocene time ily on limited ground-water resources. New of saturation occurs in different rock units extends into the southern Santa Fe embay- geologic mapping of 7.5-min quadrangles in making up the regional aquifer, depending ment and, although there is no surface evi- the area will build on prior work and will on location. dence of doming here, their presence is form the basis of future work in the area. In LANL’s Groundwater Protection Program responsible for the absence of Tesuque sedi- addition, utilization of a considerable body

4422 NEW MEXICO GEOLOGY May 2000 ments in the western part. A thin veneer of 35.05 ± 0.53 Ma (2σ error). The plateau age is speculate that most Paleozoic clasts originat- Ancha Formation overlies the Tesuque and defined by a weighted mean of nine steps ed east of the Picuris–Pecos fault (PPF) and older rocks in the southern embayment that comprising nearly 93% of the total 39Ar suggest the following testable scenario. masks subsurface relationships beneath it. released. The plateau age is virtually indis- Middle (or early?) Oligocene inversion of More than 7,000 ft of Paleozoic and Meso- tinguishable from the total gas age of 34.5 ± Laramide compressional/transpressional zoic rocks were removed by pre-Galisteo 1.1 Ma and is thought to represent the age of structures initiated Santa Fe Group sedimen- erosion in less than 20 mi from Galisteo out- emplacement. tation. East-side-up motion on the PPF pro- crops in the southern end of the Santa Fe The unit described does not contain any vided Pennsylvanian clasts to west-flowing embayment to its northern part, where an pumice or volcanic ash. Therefore it is not an drainages; onset of tectonic inversion permit- equally thick suite of Tertiary rocks is ash-fall or ash-flow deposit. Subhorizontal ted northward progradation of volcaniclastic encountered overlying Precambrian. Includ- platy jointing is commonly associated with aprons and spread of mafic lava from the La ed in this thick Tertiary suite are 1,500 ft of slowly cooled lava flows. Thus we conclude Cienega (and Cerrillos?) areas. Significant lacustrine deposits, the La Mesa limestone, that the deposit is likely a lava flow. How- late Oligocene and later westward tilting of apparently of Eocene, upper Galisteo age ever it is impossible at this time to exclude a the Española Basin was accommodated on that have been encountered nowhere else. shallow intrusive genesis. Questions that the east by west-side-up motion on the PPF, The Tesuque Formation is the primary remain to be answered include the nature of forming the headwaters of the Pecos River aquifer in the region, so its presence or the faulting that preserved this outcrop and and abruptly terminating westward transport absence in the embayment has a profound the absence of a nearby vent for this unit. An of Paleozoic detritus to the Española Basin. effect on development in the Santa Fe region. eroded eruptive center in the southern Sangre de Cristo Mountains is a possibility. HYDROGEOLOGY AND WATER RE- LATEST EOCENE FELSIC VOLCANIC SOURCES AT ELDORADO AND THE ROCKS FROM THE SOUTHERN OLIGOCENE ONSET OF SANTA FE GREATER SAN MARCOS WATER- SANGRE DE CRISTO MOUNTAINS, GROUP SEDIMENTATION NEAR SHED, SANTA FE, NEW MEXICO, by J. NEW MEXICO, by E. A. Melis, eamelis@ SANTA FE, NEW MEXICO, by Gary A. P. Frost, New Mexico Office of the State nmt.edu, C. J. Harpel, and S. A. Kelley, Smith, [email protected], Department of Engineer Department of Earth and Environmental Earth and Planetary Sciences, University "Eldorado" describes residential subdivisions Science, New Mexico Institute of Mining of New Mexico, Albuquerque, NM 87131 created over the last 30 yrs by AMREP, also and Technology, Socorro, NM 87801; and P. STATEMAP geologic mapping northeast of the developer of Rio Rancho. This city of W. Bauer, New Mexico Bureau of Mines Santa Fe elucidates stratigraphic and struc- gold covers about 40 mi2, occupying the and Mineral Resources, New Mexico tural relationships recording extensional piedmont plain of the San Marcos watershed Institute of Mining and Technology, foundering of the local Laramide uplift by within the Santa Fe embayment of the Socorro, NM 87801 middle Oligocene. Central to this hypothesis Española Basin. To address water-supply An unnamed felsic volcanic unit located in are new data on the age and provenance of concerns, for several years the Eldorado area the southern Sangre de Cristo Mountains is the Bishop's Lodge Member (BLM) of the has been subject to a county moratorium on thought to have erupted as a lava flow dur- Tesuque Formation (Santa Fe Group rift- new subdivisions. Eldorado shares the water ing the latest Eocene. This newly recognized basin fill). The BLM consists of at least two resources with Lamy, Cañada de los Alamos, outcrop occurs in the Rosilla Peak 7.5-min volcaniclastic intervals (each 10–60 m thick) Cerrillos, and numerous rural residents. The quadrangle about 15 km north of Pecos, New within nonvolcaniclastic alluvium of the hydrogeology is complex, and abundant Mexico, and is potentially the first rift-related Nambé Member (NM). Typically interpreted ground water has not been identified. volcanic rock of this age found within the as the distal equivalent of the Abiquiu and Ground water is being mined. All residents southern Sangre de Cristo Mountains. The Picuris Formations derived from northern utilize septic tanks for liquid-waste disposal. age of the unit overlaps ages of 28–34 Ma for New Mexico and Colorado, new observa- "Downstream" ground water users rely on calc-alkaline to alkaline intrusives in the tions demonstrate that the BLM is locally through-flow within the local hydrologic sys- Ortiz Mountains 50 km to the southwest. The derived and correlates to the upper Espinaso tem. age is also nearly identical to ages obtained Formation: (1) 60-cm clasts are too large for AMREP created El Dorado Utilities, to per- for the lower Picuris Tuff in the Taos area 75 distal Abiquiu and Picuris Formations; (2) mit the creation of smaller lots. Water service km to the north (Bauer, pers. comm.). clast sizes coarsen southward; (3) clast min- to 2,300 users is provided by 15 wells, includ- The regional geology consists of Protero- eralogy is consistent with late-stage alkalic ing the Lamy well beside Galisteo Creek. The zoic tonalite, amphibolites, and granite over- Espinaso magmatism; (4) tephra with 3-cm- Lamy well has historically produced one- lain by Carboniferous limestones and shales diameter lapilli requires a local source; (5) third of the total water used and is drought of the La Posada and the Alamitos Forma- 30.45 ± 0.16 Ma tephra (40Ar/39Ar date on sensitive. Overall, ground-water production tions. The felsic lava crops out on a ledge biotite by New Mexico Geochronology grew exponentially through the 1980s and above the Pecos River and is fault bound by Research Laboratory, NMIMT) demonstrates early '90s. Also during this period hundreds coarse sandstones and limestones of the La correlation to the Espinaso Formation. of domestic wells were drilled. Posada Formation. The unit occupies an area Olivine basalt in the NM above the BLM may Ground-water recharge is relatively mod- of 0.01 km2 and has an approximate true ver- correlate to post-Espinaso mafic lava near La est in the low foothills of the Sangre de tical thickness of 25 m. In outcrop it is white Cienega. Furthermore, the BLM locally over- Cristos. However, significant stream losses and exhibits platy fracturing. Hand samples lies at least 400 m of NM, indicating signifi- and potential recharge are inferred from a are porphyritic, with abundant phenocrysts cant Oligocene deposition of rift-basin fill. watershed-wide storm water model. The of predominantly biotite and plagioclase. These lower NM strata thicken on the hang- storm water model also suggests that runoff Minor phenocryst phases include quartz, ing walls of east-facing normal faults and rest and recharge are extremely sensitive to the sanidine, and xenocrystic muscovite. In thin- on Precambrian rocks; Paleozoic strata are range condition, believed to have degraded section the rock has a groundmass of plagio- locally preserved on the footwalls, suggest- since occupation by livestock. Discharge clase, quartz, and rare biotite microlites and a ing inversion of Laramide reverse faults. The occurs by storm runoff, underflow, and trace of glass. The microlites display a lowest NM strata have abundant Paleozoic spring flow to Galisteo Creek and by pump- notable alignment in the direction of flow. clasts (25–60%, typically 50–60%) compared ing. Almost 1,000 acre ft per year is now Plagioclase phenocrysts show extensive to NM strata between BLM volcaniclastic being appropriated in the watershed. oscillatory zoning and are occasionally glom- intervals (25–35%) and NM beds above the Beneath the piedmont, the principal erocrystic. Quartz is rounded and resorbed. BLM (< 10%, typically < 1%). Although pos- aquifer is the Ancha Formation, which Muscovite xenocrysts have reaction rims of sibly recording unroofing of Paleozoic strata unconformably overlies very complex geolo- biotite. 40Ar/39Ar step heating of biotite phe- now absent from the Santa Fe Range, there gy, including volcanics and Mesozoic and nocrysts at the New Mexico Geochronology are also arguments for prior removal of Paleozoic formations. Some areas have mod- Research Laboratory yielded a plateau age of Paleozoic rocks during Laramide uplift. I est ground-water availability, and water

MayMay 2000 NEW MEXICO GEOLOGY 43 wells have been drilled to 1,000 ft. The area is stepping en echelon pattern of down-to-the- 700 ft have encountered only the red mud- being studied using geophysics and new sur- east normal faults that probably formed dur- stones of the Galisteo Formation. face geologic mapping. A conceptual model ing west- to northwest-directed extension. These formations produce potable water, of the hydrologic system places most The pattern is compatible with minor, post- although water quality varies within each ground-water flow in the shallow aquifer, Oligocene, left-lateral movement on the formation. Within the Espinaso Formation, although some interesting deep aquifer pos- adjoining Cañoncito fault system. Other geo- fluoride, barium, and copper have been sibilities are suggested. logic evidence suggests right-lateral move- detected above the EPA’s maximum contam- Future water quality and supply issues ment occurred on the Cañoncito fault system inant levels (MCLs) for drinking water. link Eldorado and its neighbors within the during Laramide to post-Eocene time and Within the Galisteo Formation, fluoride, sul- watershed. Although desirable, it is unrea- perhaps even earlier. fate, and total dissolved solids have been sonable to expect to determine a “sustainable detected above the MCLs. Further study of ground-water yield” within the watershed WHERE THE WATER MIGHT BE: water availability and regional trends within because of the geologic complexity and PROSPECTING FOR WATER IN THE these formations is needed, as continued vagaries of New Mexico climate and PRE-TESUQUE TERTIARY SEDI- development in this area will increase recharge. Ongoing studies may help extend MENTS SOUTH OF SANTA FE, NEW demands on already limited aquifers. the resource, but the equities of all users will MEXICO, by Catherine D. Ratcliff, rat- someday require a broader sharing of and [email protected], Paul G. Drakos, and HYDROGEOLOGIC FRAMEWORK FOR caring for the resource in a unified ground- Jay Lazarus, Glorieta Geoscience, Inc., P.O. REGIONAL GROUND-WATER FLOW water management scheme. Box 5727, Santa Fe, NM 87502 MODEL OF THE ELDORADO AREA, An increasing number of domestic wells are SANTA FE COUNTY, NEW MEXICO, by THE ESPINASO FORMATION RE- being drilled in and around the Galisteo Steven T. Finch, Jr., and Sharman L. VEALED IN AEROMAGNETIC DATA Basin south of Santa Fe, New Mexico. Many Carpenter, John Shomaker & Associates, SOUTH OF SANTA FE, NEW MEXICO: of these wells encounter the Espinaso Inc., 2703-D Broadbent Parkway NE, PRELIMINARY INTERPRETATIONS, by Formation and the Galisteo Formation at Albuquerque, NM 87107 V. J. S. Grauch, [email protected], U.S. Geolog- depths ranging from 20 to 100 ft below In recent years many researchers have ical Survey, MS 964, Federal Center, ground surface (bgs). In general, data worked on sorting out the geologic setting of Denver, CO 80225; Alvis L. Lisenbee, South obtained during drilling and well testing the Santa Fe embayment, particularly in an Dakota School of Mines, Rapid City, SD indicate that water production in both for- effort to evaluate water availability in the 57701; and Mark R. Hudson, U.S. mations is limited. However, water capable Eldorado area. John Shomaker & Associates, Geological Survey, MS 939, Federal Center, of sustaining limited development may be Inc., is developing a ground-water flow Denver, CO 80225 found: (1) in fractures within the Espinaso, model of the Eldorado area to evaluate and High-resolution aeromagnetic data recently (2) at the basal contact between the Espinaso predict availability of ground water. The collected over the southern Española Basin and the Galisteo, and (3) in fractured channel model area is bound to the north and west by show expressions of faults, igneous rocks, sands within the Galisteo. Water quality in the Santa Fe River, to the south and west by Precambrian crystalline rocks, and anthro- both formations is variable but adequate for the Galisteo River, and to the east by the pogenic structures. A characteristic, rough- drinking water purposes. Sangre de Cristo Mountains. textured, aeromagnetic map pattern between The Espinaso Formation is of Oligocene Most domestic and community supply the Cerrillos Hills and Lamy reveals the dis- age and consists primarily of red to gray, por- wells in the Eldorado area yield water from tribution of the volcaniclastic Espinaso For- phyritic monzonite volcanic and volcaniclas- saturated Quaternary-age alluvium, Qua- mation under a thin cover of Ancha For- tic rocks (Disbrow and Stoll, 1957; Baldridge ternary-Tertiary-age Ancha Formation, and mation. The rough aeromagnetic pattern et al., 1980). The thickness of this formation is with less success, from the Tertiary-age ends at an east-west curvilinear boundary on location-dependent and, based on well Espinaso and Galisteo Formations. This the north that probably represents an abrupt records and drilling observation, ranges from sequence of Quaternary and Tertiary rocks downward ramp of the Espinaso Formation 100 to 1,000 ft. Most wells completed in the was deposited on erosional unconformities to the north below the younger, nonmagnet- Espinaso produce less than 5 gal per min and in paleovalleys along the fringe of the ic Tesuque and Ancha Formations, the pri- (gpm), although wells located within fracture Santa Fe embayment, which creates a com- zones may produce 10 gpm or greater. mary aquifers in the Santa Fe area. This plicated setting for developing a stratigra- Limited testing data indicate that limited boundary provides a southern limit of the phy-based ground-water flow model. recharge occurs primarily through tectonic thick clastic aquifer deposits. The rough aero- The model framework is based on our cur- and/or cooling fractures. Near the intersec- magnetic pattern is also limited on the east- rent understanding of (1) the distribution ern side near the middle of the Eldorado tion of NM–14 and Santa Fe County Road 42, the contact between the Espinaso and the and saturated thickness of the geologic units housing subdivision, indicating the buried from the water table to a depth of 2,000 ft eastern limit of the Espinaso Formation. Galisteo was encountered at approximately 1,000 ft bgs. The completed well reportedly below the water table, (2) estimates and dis- High-amplitude aeromagnetic anomalies tribution of recharge along the mountain that correspond to magnetic Precambrian produced 100 gpm. The Galisteo Formation is of Eocene/ front, and (3) estimates of hydraulic proper- granite east of Eldorado extend into the east- ties for the geologic units incorporated into ern part of the subdivision where the granite Oligocene age and consists of conglomerates the model. can be inferred at depth. Delimiting the and sands interbedded with thick sequences Precambrian granite under cover may help of red and orange mudstone; the Galisteo Formation is estimated to be in excess of locate overlying Madera Limestone, a poten- SESSION 5—PALEONTOLOGY tial aquifer. 1,000 ft thick in this area (Spiegel & Baldwin, The aeromagnetic data also reveal an 1963). Fractured channel sands within the intriguing, triangular pattern located where Galisteo consist of fine- to medium-grained, DIVERSITY AND PALEOECOLOGY OF the Espinaso Formation is mostly covered angular to subangular volcanic and granitic THE PENNSYLVANIAN FISH FAUNA west of Eldorado. Where the cover is not pre- clasts and may be over 100 ft thick. Galisteo AT KINNEY BRICK QUARRY, CEN- sent at the extreme southern extent of the tri- Formation sands can produce water in excess TRAL NEW MEXICO, by Sally C. Johnson angular pattern, linear anomalies comprising of 40 gpm, but 5–10 gpm may be more typi- and Spencer G. Lucas, New Mexico Muse- the triangle correspond either to mapped cal. Transmissivity values for these sands um of Natural History and Science, 1801 faults or erosional boundaries of the range from 53.5 gpd/ft to 1,300 gpd/ft. Mountain Road NW, Albuquerque, NM Espinaso Formation. Preliminary interpreta- Where channel sands are not encountered, 87104 tion of the anomalies using these relations the Galisteo produces virtually no water and The Kinney Brick Quarry is a lagerstatte suggests a north–northwest-trending, left- consists of very fine grained, red and orange developed in the Pennsylvanian Pine Sha- stepping en echelon pattern of down-to-the- mudstones. Some wells drilled to depths of dow Member of the Wild Cow Formation

4444 NEW MEXICO GEOLOGY May 2000 located in the Manzanita Mountains near Bursum. The lowest assemblage is a hema- Dimetropus sp., Gilmoreichnus hermitanus Gil- Albuquerque, New Mexico. The fish fauna tized coquina that consists mainly of densely more, and Hyloidichnus bifurcatus Gilmore. consists of four species and six undescribed packed shells of the bivalves Septimyalina The vertebrate tracks show a distinct lack of morphotypes of Actinopterygii, one species burmai and Myalina (Orthomyalina), with low tail drags, and there is no significant inverte- of Acanthodii, six species of Chondrichthyes, abundances of Aviculopecten, Aviculopinna, brate ichnofauna at this site. The Abo Pass and two species of Sarcopterygii. The and Schizodus; the brachiopods Derbyia and tracksite is older than the Robledo Mountain actinopterygian fish encompass the largest Meekella; the snail Retispira aff. R. tenuilineata; mega-tracksite (NMMNH locality 846) in number of species in the quarry. There are and rare bryozoan and crinoid fragments. south-central New Mexico but has a similar four described species: Platysomus schultzei, This is a nearshore, probably wave-concen- tetrapod ichnofaunal diversity. However, the Amphicentrum jurgenai, Pyritocephalus trated assemblage. The unit 2l assemblage is Abo Pass tracksite shows a distinct difference lowneyae, and Schizolepis manzanitaensis. The dominated by the large (W = 75 mm) pro- in the abundance of Limnopus, the track of a remaining paleoniscoids can be divided into ductoid brachiopod Reticulatia americana, large temnospondyl amphibian. Limnopus is six morphotypes. P. schultzei is the most with fewer specimens of Composita subtilita, 1% of the census at NMMNH locality 846, abundant species in the quarry. These fish Juresania aff. J. nebrascensis, Hystriculina aff. whereas Limnopus is 50% of the census at the were autochthonous to the lagoon. They H. wabashensis, Meekella cf. M. striatocostata, Abo Pass tracksite. Factors that could were euryhaline and were feeding on crus- Derbyia, and Linoproductus. Few bivalves account for this abundance difference of taceans. The remaining actinopterygian fish (Pseudomonotis hawni, Wilingia terminale, Limnopus include facies and age differences. are represented by high diversity and rela- Aviculopinna) or other groups are present. Limnopus is rare at other sites of facies similar tively low abundance. P. schultzei outnum- The unit 29 fauna is numerically dominated to the Abo Pass tracksite, such at those near bers the rest of the species and morphotypes about equally by brachiopods (chiefly Villanueva in northern New Mexico. The of actinopterygian fishes from 6:1 to 30:1. Neochonetes transversalis, J. aff. J. nebrascensis) Abo Pass tracksite thus suggests that large Little is known about the phylogenetic rela- and by a much higher diversity of bivalves amphibians were more common in inland tionships and ecology of these paleoniscoid (Septimyalina, Aviculopinna, Permophorus, environments during the middle part of the fishes. The acanthodians are represented by Parallelodon, Aviculopecten, Schizodus, Edmon- Wolfcampian than in coastal environments one species, Acanthodes kinneyi. It is as abun- dia, and others). Unidentified small high- during the late Wolfcampian. dant as P. schultzei. These fish were also spired snails are locally abundant, often asso- autochthonous to the lagoon. The acanthodi- ciated with small knobby algal growths; the EARLY PERMIAN FLORA FROM THE ans were euryhaline and piscivorous. The nautiloid Mooreoceras is common, but ABO FORMATION, PLACITAS, SAN- Chondrichthyians are represented by high crinoid, bryozoan, and trilobite fragments DOVAL COUNTY, NEW MEXICO, by M. diversity and very low abundance. The chon- are rare. The uppermost (unit 39) fossilifer- J. Knaus, Department of Biology, South- drichthyan taxa are: Orthocanthus huberi, ous limestone is packed with small high- west Texas State University, San Marcos, Cobelodus aculeatus, Symmorium reniforme, spired snails and Permophorus steinkerns; TX 78666; and S. G. Lucas and M. J. Peripristis aff. P. semicircularis, Ctenoptychius, other bivalves (Septimyalina, Aviculopecten) Rowland, New Mexico Museum of Natural and Listracanthus. C. aculeatus is known from and snails (Retispira, Goniasma, Naticopsis) are History and Science, 1801 Mountain Road two skeletons. The remaining chondri- also present. Brachiopods, crinoid and echi- NW, Albuquerque, NM 87104 chthyans are known from isolated teeth, noid fragments, and small pieces of wood are New fossil sites near Placitas, New Mexico, spines, and braincases. The Chondrichthyes, rare. yield a diverse array of vertebrate bone, with the exception of O. huberi, were The macroinvertebrate faunas of the type teeth, footprints, insects, and other inverte- allochthonous and of marine origin. O. Bursum consist mainly of taxa identical or brate fossils, and plant macrofossils. This and huberi, a xenacanth shark, was allochthonous closely related to taxa known from the the nearly complete Lower Permian strati- from the fluvial source of the lagoon. The sar- Virgilian; little significant change in marine graphic section provide a unique opportuni- copterygians are represented by an indeter- invertebrates evidently occurred across the ty to reconstruct past climate and paleoecolo- minate coelacanth species and Proceratodus Virgilian–Wolfcampian boundary in New gy for this critical period in Earth history. hlavini. The dipnoan P. hlavini is represented Mexico. Although each of the four assem- Plant remains commonly occur in the typi- by an isolated tooth plate that washed in blages is taxonomically distinct, they gener- cally brick red to maroon sandstones of the from the fluvial source of the lagoon. The ally indicate nearshore, shallow marine, per- Lower Permian Abo Formation but consist coelacanths are moderately abundant. They haps locally restricted conditions. The least nearly exclusively of impressions of branch originated in the fluvial source of the lagoon. diverse, most mollusc-dominated assem- fragments of the early conifer Walchia. The blages (from units 6 and 39) suggest salinities monodominance of walchian conifers proba- INVERTEBRATE FAUNA OF THE BUR- that fluctuated somewhat away from normal bly reflects a taphonomic bias toward pre- SUM FORMATION (LOWER WOLF- marine values. serving these robust and heavily cutinized CAMPIAN) AT ITS TYPE SECTION, three-dimensional branch systems in a HANSONBURG HILLS, SOCORRO EARLY PERMIAN TETRAPOD ICHNO- coarse-grained sediment. The discovery of a COUNTY, NEW MEXICO, by Barry S. FAUNA AT ABO PASS, CENTRAL NEW dark-gray shale lens near the top of the Abo Kues, Department of Earth and Planetary MEXICO, by Allan J. Lerner, Sally C. Formation (NMMNH locality 3922), bearing Sciences, University of New Mexico, Johnson, and Spencer G. Lucas, New Mexico abundant plant remains, offers a rare glimpse Albuquerque, NM 87l3l; Spencer G. Lucas, Museum of Natural History and Science, of co-occurring floral elements that are not New Mexico Museum of Natural History 1801 Mountain Road NW, Albuquerque, preserved in most cases. In addition to and Science, 1801 Mountain Road NW, NM 87104 conifer branch fragments, these floral ele- Albuquerque, NM 87l04; G. L. Wilde, GLW A new tracksite in the Abo Formation, New ments include the peltasperms Rhachiphyllum International, Midland, TX 79705; K. Mexico Museum of Natural History schenkii and Autunia conferta, cordaite leaf Krainer, University of Innsbruck, A-6020, (NMMNH) locality 4394, is 2.4 km south of fragments, the seed genus Samaropsis sp. and Innsbruck, Austria the type section at Abo Pass. The tracks are small seeds of unknown affinity, pecopterid Although fusulinids from the Bursum For- found in a thinly bedded, fine-grained sand- frond fragments, and charcoalified wood. mation are well known, virtually no informa- stone unit 141 m above the basal contact of The fragmentary nature of the plant remains tion on its macroinvertebrate fauna has been the Abo Formation, so it is presumably mid- indicates that they either underwent trans- reported since the formation was first recog- dle Wolfcampian in age. The track-bearing port or experienced some biological degrada- nized in l946. The mainly nonmarine, 85-m- stratum is a 0.3–1.3-m-thick tabular sand- tion prior to burial. This allochthonous thick Bursum type section contains four thin stone with extensive ripple laminae that we assemblage provides valuable information marine limestone intervals bearing moder- interpret to represent a shallow water, flood- on overall diversity, because it may represent ately diverse invertebrate assemblages: units plain sandflat. Six vertebrate ichnotaxa are sampling over a broader geographic area and 6, 2l, 29, and 39, which are 7 m, 49 m, 67 m, present: Limnopus vagus Marsh, Dromopus possibly greater diversity of habitats. and 80 m, respectively, above the base of the agilis Marsh, Batrachichnus delicatulus Lull, Although occurring gradually in time, the

MayMay 2000 NEW MEXICO GEOLOGY 45 Permo–Carboniferous transition represents a seum of Natural History and Science, 1801 the early Paleocene (Torrejonian) Ojo Encino period of global scale climate change of Mountain Road NW, Albuquerque, NM Member, Nacimiento Formation (NMMNH unusually great overall magnitude. The 87104; and Kate E. Zeigler, Department of locality L-2701) represents a juvenile of the Wolfcampian Placitas flora, in conjunction Earth and Planetary Sciences, University pantodont mammal Pantolambda bathmodon. with the older Kinney Brick and the Carrizo of New Mexico, Albuquerque, NM 87131 The skull includes much of the upper denti- Arroyo floras, provides possibly time Intensive excavations totaling 21 days in tion (DP1?, DP2–4, M1–2), parts of both maxil- ordered documentation of unique regional May and September, 1999, vastly improved lae, portions of the skull roof (frontal and aspects of the transition to the drought toler- our understanding of NMMNH locality parietal), and the glenoid area. The preserved ant sclerophyllous floras that originated in 3845, the Snyder Quarry. This locality, situat- upper deciduous dentition is relatively the Late Carboniferous and persisted to com- ed in the Petrified Forest Formation approxi- unworn. The postcranial skeleton includes prise the dominant floras of the Permian. mately 28.5 m below the Rock Point several partial vertebrae, ribs, part of a left Formation, yields diverse and well-pre- scapula, part of the right ilium, and portions THE AETOSAUR DESMATOSUCHUS served assemblages of Upper Triassic verte- of the front and hind limbs including a near- FROM THE UPPER TRIASSIC SNYDER brates and invertebrates and is probably the ly complete manus (several carpal bones, QUARRY, NORTHERN NEW MEXICO, most important and productive Chinle partial metacarpals, and several phalanges). AND ITS BIOCHRONOLOGIC SIGNIF- Group vertebrate fossil locality discovered in This specimen is significant in that it is the ICANCE, by Kate E. Zeigler, kaerowyn@ the last half of the twentieth century. Taxa first reported juvenile specimen of P. bath- unm.edu, and Andrew B. Heckert, Depart- added to the faunal list in 1999 include modon and provides information on the ment of Earth and Planetary Sciences, unionid bivalves, as-yet-undetermined oste- deciduous dentition of Pantolambda. University of New Mexico, Albuquerque, ichthyans, metoposaurid amphibians (proba- This juvenile specimen of P. bathmodon NM 87131; and Spencer G. Lucas, New bly Buettneria perfecta), and the aetosaur Typo- allows study of certain aspects of its ontoge- Mexico Museum of Natural History and thorax coccinarum. Additional material has ny by placing constraints on the tooth erup- Science, 1801 Mountain Road NW, also made it possible to refine previous taxo- tion sequence and by providing information Albuquerque, NM 87104 nomic assignments. A complete skull of on relative times of fusion between various Recent collecting by volunteer crews from “Belodon” buceros, a Pseudopalatus-grade phy- elements. There are unfused sutures between the New Mexico Museum of Natural History tosaur, is the first generically determinate the frontals. The parietals are probably only (NMMNH) at the Snyder Quarry in the phytosaur from the quarry, although at least partially fused. The frontals are fused to the upper part of the Petrified Forest Formation, three other phytosaur skulls await prepara- parietals, but a digitating sutural contact Chinle Group, near Ghost Ranch, New tion at NMMNH. Additionally, we now have between these elements is still readily visible Mexico, has brought to light numerous significantly more cranial and postcranial between them. All the limb elements have scutes of the aetosaur Desmatosuchus haplo- material from the coelophysid theropod than unfused epiphyses, except possibly for the cerus, including a right lateral fourth cervical first reported and tentatively recognize it as a distal end of the humerus that may be only scute (NMMNH P-29045). The scutes display new species of Eucoelophysis. Both Typothorax partially fused. The distal ends of the scapu- several diagnostic characteristics of D. haplo- coccinarum and Pseudopalatus-grade phy- la and the metacarpals are unfused. The size cerus, including: prolonged thin laminae of tosaurs are index taxa of the Revueltian land- of limb articular ends approaches adult size bone issuing anteriorly from the scute’s ante- vertebrate faunachron, confirming earlier and the lengths of the ulna and radius are rior edge, lack of an anterior bar, and lithostratigraphic correlations that predicted approximately 75% of adult length (based on recurved dorsal spikes on the lateral scutes. a Revueltian age (early-mid Norian, approxi- shaft length), and so fusion of the epiphyses These scutes are found in close association mately 218 Ma) for the Snyder Quarry. evidently did not commence and the loss of with scutes and bones of the aetosaur The revised faunal list thus includes con- the deciduous dentition did not begin until Typothorax and bones of phytosaurs and chostracans, a decapod crustacean, unionid the animal had attained near-adult size. In coelophysid theropods. bivalves, cf. Semionotus, other osteichthyans, these respects, P. bathmodon resembles the Of significance is the age of these fossils. aff. Buettneria, “Belodon” buceros, aff. Pseudo- early Eocene (Wasatchian) pantodont Desmatosuchus is most abundant in upper Coryphodon. Carnian rocks, with rare occurrences in palatus, Desmatosuchus haplocerus, Typothorax Norian strata. The Snyder Quarry is strati- coccinarum, a ?cynodont, Eucoelophysis n. sp., TAXONOMIC REVISION OF THE GENUS graphically very high in the Chinle Group, a larger ceratosaur, and at least one microver- PERIPTYCHUS, A PALEOCENE “CON- approximately 60 m below the Entrada tebrate archosaur. Numerically, this is one of DYLARTH” FROM THE SAN JUAN Sandstone, and, based on tetrapod bio- the most diverse Chinle sites known. BASIN, NEW MEXICO, by S. A. Libed and chronology (aetosaur Typothorax and phy- Screenwashing of several tons of matrix from S. G. Lucas, New Mexico Museum of tosaur Pseudopalatus), the site is Revueltian the site will probably yield additional taxa. Natural History and Science, 1801 Moun- (early to mid Norian, 210–218 Ma) in age. The quality of vertebrate preservation is tain Road NW, Albuquerque, NM 87104; P. The Desmatosuchus fossils found at Snyder exceptional, and preliminary preparation E. Kondrashov, Paleontological Institute, Quarry are the youngest specimens found indicates that several ontogenetic stages of Profsoyuznaya, 123, Moscow, Russia; and and extend the range of Desmatosuchus well phytosaurs are present, as well as at least T. E. Williamson, New Mexico Museum of into the Norian. It should thus be noted that three individuals of Eucoelophysis. Continued Natural History and Science, 1801 Desmatosuchus is a poor index taxon, excavation and preparation of fossil material Mountain Road NW, Albuquerque, NM although there is a distinct possibility that from the Snyder Quarry thus presents a 87104 there are multiple, temporally successive unique opportunity to address diverse ques- In 1881, E. D. Cope first recognized and species that have gone unrecognized due to tions regarding Upper Triassic ecosystems. described the highly variable “condylarth” poor preservation. genus Periptychus, based on specimens from A JUVENILE PANTOLAMBDA BATH- the Nacimiento Formation, San Juan Basin, ADDITIONS TO THE FAUNA OF THE MODON (MAMMALIA: PANTODON- New Mexico. This archaic ungulate first UPPER TRIASSIC SNYDER QUARRY, TA) FROM THE EARLY PALEOCENE appeared during the basal Paleocene PETRIFIED FOREST FORMATION (TORREJONIAN) NACIMIENTO FOR- (Puercan 1, ~65 Ma) and persisted, in relative (REVUELTIAN: EARLY-MID NORIAN), MATION, SAN JUAN BASIN, NEW abundance, through Tiffanian 5 (~56.2 Ma). NORTH-CENTRAL NEW MEXICO, by MEXICO, by Thomas E. Williamson and Measurements of all available Periptychus Andrew B. Heckert, [email protected], Paul L. Sealey, New Mexico Museum of specimens give a mean variance generally Department of Earth and Planetary Natural History and Science, 1801 twice as great as the variance typical of Sciences, University of New Mexico, Mountain Road NW, Albuquerque, NM extant mammalian species. The 8+ million Albuquerque, NM 87131; Jerald D. Harris 87104 year generic span, excessive range of varia- and Spencer G. Lucas, New Mexico Mu- A partial skull and skeleton (NMMNH P- tion, and unusually rapid evolutionary rate seum of Natural History and Science, 1801 27844) from the Mixodectes pungens Zone of estimated for Paleogene mammals, com- Mountain Road NW, Albuquerque, NM

4466 NEW MEXICO GEOLOGY May 2000 pelled researchers to postulate several of Hemiauchenia; the small pronghorn antilo- Analysis of these rocks is important for (1) Periptychus species. Proposed phylogenies caprid Capromeryx; and two proboscideans, understanding the nature of basement reflec- involved up to two genera and eight species. Rhynchotherium falconeri and Stegomastodon tors on seismic lines across the Tucumcari In recent comparisons, these species distinc- sp. This is a fairly typical faunal assemblage Basin and (2) constraining the Proterozoic tions are controvertible. The advocated con- found in New Mexico Blancan sites, mostly history of east-central New Mexico. trasting characters continuously recur and consisting of large grazing ungulates and The gabbro is medium to coarse grained vary within the proposed divergent popula- dominated by horses of the genus Equus. and consists mainly of plagioclase, pyroxene, tions and often manifest themselves within Five of these species are restricted to Blancan and olivine. This rock has a cumulate to sub- individual specimens. faunas, including Megalonyx leptostomus, ophitic texture. Gabbro is the most abundant The early collected Periptychus specimens Equus cumminsii, E. simplicidens, the large rock type in the basement section and char- were gathered without geological maps or Camelops, and Rhynchotherium falconeri. The acteristically occurs as sill-like bodies. The accurate stratigraphic data. Without tempo- two sills at depths of 1,759–1,859 m and most biostratigraphically diagnostic of these ral correlation, species distinctions were 1,905–2,155 m are strong reflectors on seismic taxa is Rhynchotherium, a proboscidean char- reduced to arbitrary divisions based on a the- lines in the Tucumcari Basin. A number of acterized by a strongly downturned man- orized intermediacy in size, proportion, small dikes are inferred in the lower part of robusticity, etc., rather than any true dispari- dibular symphysis and the presence of lower the well. The gabbro appears to be the ty, adaptive shift, or morphological innova- tusks. Rhynchotherium became extinct in the youngest rock unit within the basement, tion. Our new analysis of recently collected late Pliocene at about 2.2 Ma, together with since it intrudes the other Precambrian rock NMMNH Periptychus specimens, procured several other characteristic genera of Blancan units. with reliable geological and stratigraphic mammals. The lower jaws of R. falconeri from The volcanic-sedimentary sequence data, has allowed temporal organization. The this site were collected near the top of the (2,155–2,664 m) consists of rhyolitic tuff, once excessively broad range of specimens local section of the Palomas Formation on the gneissic metasediment and meta-arkose. clearly differentiates into two lineages: an south side of Arroyo de la Parida, suggesting Rhyolitic tuff consists of sparsely angular to early Puercan population consistent with that the entire fauna, most of which occurs sub-rounded fragments of quartz, feldspar, Periptychus coarctatus and a subsequent, more some 40 m lower in the section, is older than and lithic fragments (igneous rocks) support- variable, Torrejonian–Tiffanian group we 2.2 Ma. An early Blancan age for the Arroyo ed by a fine-grained groundmass, which is unify as P. carinidens. These two species, in de la Parida Local Fauna is excluded by the composed by microlites of quartz, carbonate, turn, segregate into smaller temporal popu- presence of E. scotti, Camelops sp., and the chlorite, and iron oxide. This unit appears to lations that now exhibit normative mean small Hemiauchenia, all of which first appear pass to dark-green, fine- to medium-grained variance. Despite its lengthy duration, oscil- in New Mexico faunas during the medial rhyodacite. Gneissic metasediment is charac- lations in mean size, and wide geographic Blancan (2.6–3.7 Ma). The absence of South terized by a salt and pepper-sugary appear- range, we interpret P. carinidens as a single American immigrants that arrived following ance with poorly developed bands of light- evolving lineage due to continuous morpho- the Great American Interchange suggests colored minerals intercalated with bands of logical overlap and lack of evidence of local that the Arroyo de la Parida Local Fauna is medium dark minerals. The meta-arkose is endemism. Our reconstruction thus involves older than 2.7 Ma. Megalonyx is the only fine to medium grained and pink to orange a parsimonious single genus, Periptychus, mammal of South American origin in south- in color. Quartz, feldspar, and fragments of and two temporally successive species, Perip- western Blancan faunas that was not a par- igneous rocks cemented by carbonate and tychus coarctatus and P. carinidens. iron oxide characterize this rock. In its lower ticipant in the Great American Interchange. portion, fragments of underlying syenite are Megalonyx or its progenitor arrived from PLIOCENE (BLANCAN) VERTEBRATES abundant. FROM THE PALOMAS FORMATION, South America in the late Miocene, and M. The syenite (2,664–3,740 m) is medium to ARROYO DE LA PARIDA, SOCORRO leptostomus is fairly widespread in early coarse grained, pink, light orange to light BASIN, CENTRAL NEW MEXICO, by G. through late Blancan faunas. The Arroyo de gray, and is dominated by potassium S. Morgan, S. G. Lucas, and P. L. Sealey, New la Parida Local Fauna is thus interpreted to feldspar. This rock exhibits some variation in Mexico Museum of Natural History and be medial Blancan (2.7–3.7 Ma) and is similar composition, passing from syenite to quartz Science, 1801 Mountain Road NW, Albu- in age to the Belen Fauna from the “Sierra syenite downhole. Near its top, the syenite is querque, NM 87104; and S. D. Connell and Ladrones Formation” in the southern strongly altered and exhibits a red-iron col- D. W. Love, New Mexico Bureau of Mines Albuquerque Basin and the Cuchillo Negro oration. This zone, which shows up as a and Mineral Resources, New Mexico Creek Local Fauna from the Palomas reflector on seismic lines in the Tucumcari Institute of Mining and Technology, Formation in the Engle Basin near Truth or Basin, may represent an erosional contact Socorro, NM 87801 Consequences. between the arkosic unit and the syenite. Vertebrate fossils were first reported in 1936 The granite (3,740–4,100 m) has a por- from Arroyo de la Parida, about 6 km north- phyritic texture comprising large phe- east of Socorro, Socorro County, central New POSTER SESSION nocrysts of plagioclase, K-spar and quartz, Mexico. The Arroyo de la Parida Local Fauna supported by a matrix composed mostly by is derived from a 70-m-thick sequence of PRELIMINARY PETROGRAPHIC CHAR- quartz, feldspar, and mafic minerals, in sands and gravels that constitute the axial ACTERIZATION OF THE PRECAMB- decreasing order. The age relationship river (ancestral Rio Grande) facies of the RIAN BASEMENT IN MESCALERO between the granite and the other basement Palomas Formation of Gordon (1910, USGS NO. 1, GUADALUPE COUNTY, NEW units is not known. Prof. Paper 68). The strata in the vicinity of MEXICO, by J. F. A. Amarante and Shari A. Arroyo de la Parida are located at the north- PETROGRAPHIC ANALYSIS OF THE Kelley, Department of Earth and ern end of the Socorro Basin, representing SEVEN RIVERS FORMATION CAR- Environmental Science, New Mexico one of the northernmost occurrences of the BONATE RESERVOIR, FREN POOL, Institute of Mining and Technology, Palomas Formation, which has its type area EDDY COUNTY, NEW MEXICO, by Socorro, NM 87801 about 100 km farther south in Palomas Creek Dana Ulmer-Scholle, [email protected], Labrador Oil Company drilled a deep petro- near Truth or Consequences in Sierra County. Department of Earth and Environmental leum exploration well, Mescalero No.1, in the Science, New Mexico Institute of Mining The Arroyo de la Parida Local Fauna is Tucumcari Basin, Guadalupe County, east- and Technology, Socorro, NM 87801; and composed of ten species of vertebrates, central New Mexico in 1996. This well pene- Brian S. Brister, New Mexico Bureau of including the land tortoise Hesperotestudo; the trated ~2,650 m of Precambrian basement Mines and Mineral Resources, New ground sloth Megalonyx cf. M. leptostomus; consisting of gabbro at the top of the section, Mexico Institute of Mining and Tech- three species of horses, Equus cf. E. cumminsii, followed by a metavolcanic-sedimentary nology, Socorro, NM 87801 E. scotti, and E. simplicidens; two camels, a sequence, syenite, granite, and another gab- Fren (Seven Rivers) pool is areally and volu- large species of Camelops and a small species broic body at the bottom of the section.

MayMay 2000 NEW MEXICO GEOLOGY 47 metrically the largest oil field producing by less saline pore fluids migrating through States that occurred from latest Cretaceous to from the upper Seven Rivers Formation the more permeable carbonates. Eocene time. In Arizona and New Mexico, (Leonardian, Permian) on the Northwest Laramide-age structures are generally shelf of the Delaware Basin. The field has obscured by Tertiary volcanism and exten- yielded 5.4 mmbo from 1943 through 1996 EVIDENCE FOR LONG-LIVED CENO- sion. The age and style of Laramide defor- when it was abolished and integrated into ZOIC DEFORMATION ALONG THE mation is thus much more controversial than the Grayburg Jackson pool. Cores were col- MARGIN OF THE COLORADO in areas farther north. The rocks in the Little lected from two wells in the heart of the field, PLATEAU AND RIO GRANDE RIFT IN Hatchet Mountains, southwestern New representative of the entire producing inter- NORTHERN NEW MEXICO, by Jessica D. Mexico, have escaped pervasive overprint- val, to gain a better understanding of the Moore, [email protected], Department of ing by magmatism and extension and thus reservoir. Much of the cores (> 90%) are Earth and Planetary Sciences, University preserve Laramide structures. This area has anhydrite, but shale and carbonate lamina- of New Mexico, Albuquerque, NM 87131 the potential to clarify some of the remaining tions are also present. Thin (cm’s) laminated Geologic mapping astride Rio Grande rift- questions concerning this major tectonic dolomite stringers with porosity exceeding bounding normal faults near Abiquiu, New event. 20% comprise the reservoir. Field structure is Mexico, reveals evidence for structural defor- The purpose of this study is to determine an east-plunging anticline formed by drape mation persisting from at least Eocene the direction, magnitude, and timing of of Leonardian units over the Wolfcampian through Miocene, and specifically for reacti- Laramide deformation as recorded in the Abo reef of the Artesia– Vacuum trend. vation of reverse faults of inferred Paleocene Little Hatchet Mountains, and to compare Cores were examined under ultraviolet or Eocene age (probably Laramide) into structures developed at this time to other light, and 62 samples were selected for petro- Oligocene–Miocene normal faults. The Laramide structures observed in the south- graphic analysis based on ultraviolet fluores- north–northeast-trending Valdez fault (new western United States. South of the Copper cence due to oil saturation. Petrographically, name) parallels the Cañones fault, the trace Dick fault, a continuous Jurassic section of the carbonates have undergone extensive of which lies 2 km east of the Valdez, in its sedimentary rocks is exposed. Numerous dolomitization and replacement by anhy- hanging wall. Both faults dip steeply south- northeast-striking mafic dikes cut Jurassic drite. Dolomites range from very finely to east. A general pattern of sustained deforma- beds. Large-scale and small-scale folds are finely crystalline. Anhydrite occurs as dis- tion is shown by repetition through time of common, as well as thrust faults that may 2 placive crystal masses and nodules grown angular unconformities in the ~60 km region have reactivated as normal faults during syndepositionally within the algal mud- along the trace of these faults. The Eocene El Basin and Range extension. Quantitative stones and as poikolotopic, sub-hedral to Rito Formation, Oligocene–lower Miocene strain analysis of stretched pebbles, vesicles, euhedral, coarsely crystalline later replace- Abiquiu Formation, and mid-late Miocene and burrows, as well as analysis of folds and ments and pore fills. The petrographic data Lobato basalts all lie unconformably upon faults has been initiated. Field work has indicate that dolomitization was probably strata (Triassic through Miocene) that are revealed the presence of a spactacular syndepositional (evaporative pumping) con- progressively younger to the southwest. This stretched-pebble conglomerate within the tinuing into shallow burial (possibly schizo- repeated geometry suggests a roughly south- Jurassic Broken Jug Formation. The elonga- haline). Due to the high salinity of the pore ward dip pervading in this area from at least tion direction of limestone clasts within this fluids, anhydrite and/or gypsum, instead of Eocene through the Miocene. Furthermore, conglomerate ranges from N10°E to N10°W. calcite, plugged some of the surviving pri- bedding orientation of Jurassic through Long axis to short axis ratios of clasts range mary porosity (intergranular) and secondary Oligocene strata and thickness variations in from 2 to 10, and chert clasts within the same porosity. Secondary porosity within the Eocene and Oligocene strata indicate that unit appear to be pulled apart in the same dolomite stringers ranges from fracture, Oligocene–Miocene normal faults had elongation direction. As Basin and Range moldic, to intercrystalline. reverse motion before the Oligocene. In the extension directions were generally east-west Most of the primary depositional fabrics hanging wall of the Cañones fault, inferred in this region, these structures may record within the carbonate stringers were obliter- effects of fault-drag tilting are of opposite ductile deformation associated with the ated by dolomitization. Evaporative sabkha orientation within Jurassic and Oligocene Laramide event. The relationship of these conditions dominated this area, which was strata. Lower Abiquiu strata dip 21°SE near structures to large-scale thrust faults in the located 32 km back of the Capitan/Goat the fault, shallowing to 5°SE farther away, Little Hatchet Mountains has not yet been Seep reef. Preserved carbonate fabrics indi- indicating relative downward motion of the determined. Apparent new mica growth cate environments ranging from higher- hanging wall. The Jurassic Entrada Sand- within impure dolostone in the Broken Jug energy back-reef/beach to sabkha deposits stone dips steeply toward the Cañones fault Formation may provide a means of dating including bioclastic and oolitic packstones, near it (61°W) and shallows to 10°W farther this deformation more precisely. pisolitic packstones to algally laminated fen- away, indicating relative upward motion of estral mudstones. Subtle differences in the the hanging wall. (El Rito strata in places lie ORIGIN AND DEVELOPMENT OF THE paleo-topography probably played a role in unconformably between these rocks but in CAVES AT THE GILA CLIFF the deposition of the high-energy places are absent, and their role is unclear.) DWELLINGS NATIONAL MONU- beach/shoal units during periods of higher Differences in thickness of Eocene and MENT, SOUTHWESTERN NEW MEXI- sea-level stands since the field is coincident Oligocene strata across the two faults further CO, by James C. Ratté, U.S. Geological with the deep-seated Abo reef structural suggest a change from contraction to exten- Survey, P.O. Box 25046, MS 905, Denver, axis. However, depositional environment sion. Eastward thickening of the Abiquiu CO 80225 does not appear to play a large role in sec- Formation across the structures illustrates The Gila Cliff Dwellings were constructed by ondary porosity preservation. The highest their normal motion during its deposition, the Mogollon people in seven natural caves porosity intervals usually correspond to sec- and the El Rito generally thickens westward or alcoves in Gila Conglomerate about 800 tions where dolomite is the coarsest crys- across the faults, indicating reverse motion yrs ago. The caves are in a south-facing wall talline and anhydrite replacements and com- before or during its deposition. of Cliff Dweller Canyon, which is occupied paction are minimal. Secondary porosity by a small east-flowing tributary of the West QUANTITATIVE STRAIN ANALYSIS OF Fork Gila River. The cliff dwellings are the resulting from calcite dissolution after LARIMIDE DEFORMATION IN THE dolomitization may have been preserved main attraction at the Gila Cliff Dwellings LITTLE HATCHET MOUNTAINS, National Monument. They are easily accessi- from complete destruction by anhy- SOUTHWEST NEW MEXICO, by Michael drite/gypsum precipitation due to early oil ble at the main eastern portal to the Gila S. Cleary, [email protected], and Jeffrey Wilderness, about 40 mi north of Silver City. migration into the carbonate stringers, pre- M. Amato, Department of Geological venting further porosity occlusion. The caves that house the cliff dwellings are Sciences, New Mexico State University, all at about the same stratigraphic horizon, Alternately, porosity may have been resur- Las Cruces, NM 88001 rected during initial phases of oil migration along subtle weak zones in the conglomerate. The Laramide orogeny was a major moun- The conglomerate consists largely of pebbles by less saline pore fluids migrating through tain-building event in the western United

4488 NEW MEXICO GEOLOGY May 2000 and boulders of Bloodgood Canyon Rhyolite cobbly sand deposits can generally be differ- RATES FROM CORRELATED FLUVIAL Tuff and Bearwallow Mountain Andesite, entiated on the basis of landscape-topo- TERRACES, SOCORRO BASIN, NEW derived from volcanic rocks in the adjacent graphic position, inset relationships, soil MEXICO, by H. L. Goldstein, mercury@ Mogollon Mountains and deposited by rivers morphology, and height of the basal contact nmt.edu, and J. B. J. Harrison, Department similar to the present-day Gila. (above the Rio Grande) as determined from of Earth and Environmental Science, New The caves probably were initiated by later- outcrop and drillhole data. We informally Mexico Institute of Mining and Tech- al stream erosion and spring sapping about adopt three additional stratigraphic terms to nology, Socorro, NM 87801; D. Love, New 500,000 yrs ago. At that time the stream in clarify and extend Lambert’s terrace stratig- Mexico Bureau of Mines and Mineral Cliff Dweller Canyon was at the level of the raphy. The highest and presumably oldest Resources, New Mexico Institute of caves, approximately 65 m above the present preserved Rio Grande terrace is informally Mining and Technology, Socorro, NM stream. Other alcoves now being carved by called the Lomatas Negras alluvium (Qrl). 87801; and P. Mozley, Department of Earth this stream, along the lower trail in Cliff Unit Qrl is typically < 20 m thick. The top is and Environmental Science, New Mexico Dweller Canyon, are probably forming by generally eroded and projects 65–75 m above Institute of Mining and Technology, the same processes as the caves above. In the Rio Grande. The Edith formation (Qre) is Socorro, NM 87801 contrast, however, the zone of weakness a 3–12-m-thick and longitudinally extensive The Rio Grande rift is a classic continental rift localizing these new alcoves is the contact of marker along the eastern margin of the Rio system and is located in the southwestern the conglomerate with the underlying Grande valley, between Albuquerque and United States. Like many of the sub-basins of andesitic lava flows. San Felipe Pueblo. The base of Qre is about the Rio Grande rift, the Socorro Basin, locat- Once the stream in Cliff Dweller Canyon 12–24 m above the Rio Grande, contains Ran- ed in central New Mexico, is structurally con- had cut below the level of the future cliff cholabrean fossils, and is likely inset against trolled. It is characterized by “domino-style dwellings, the caves continued to be Qrl. Soils developed on gravelly to sandy rifting” where the west and east margins are enlarged mainly by roof collapse along piedmont deposits overlying Qre exhibit rotated fault blocks. planes of weakness such as joints and sedi- Stage III+ carbonate morphology, suggesting The Rio Grande became a through-flowing mentary bedding planes, aided by pressure- a middle Pleistocene age for Qre. The Los axial river system during the late Pliocene release exfoliation and gravity. Duranes formation (Qrd) is up to 52 m thick, and presently flows through many of the Pressure-release exfoliation not only con- overlain by the 98–110 ka Cat Hills basalt sub-basins of the Rio Grande rift. Aggrada- tributed to the enlargement of the caves but (Maldonado et al., 1999, NMGS Guidebook tion within the rift began during the early also modified the shape of the cave openings. 50, pp.175–188), and locally buries flows of Pliocene and continued until the middle The exfoliation process is perhaps best the 156 ± 20 ka (Peate et al., 1996, Geophys. Pleistocene when a major change in base known for shaping large domes in intrusive Jour. Int., v. 23, no. 17, pp. 2271–2274) Albu- level caused the Rio Grande to incise. granite terranes such as Yosemite National querque volcanoes basalt. Thus deposition of Tributary terraces are currently being corre- Park and, closer by, at Enchanted Rocks State Qrd ended between ca 160–100 ka. The ter- lated and used in the evaluation of the Rio Park on the Llano uplift, north of San race tread on top of unit Qrd (~42–48 m Grande’s incision history within the Socorro Antonio, Texas. The unroofing of large above the Rio Grande) is about 12–32 m high- Basin. granitic batholiths by erosion of overlying er than the top of Qre. Geologic mapping and Soil development has widely been used as rocks creates stresses that are relieved by comparison of subsurface data indicate that a correlative tool for geomorphic surfaces, fractures oriented parallel to the land surface, the base of Qre is about 20–25 m higher than and in the deserts of the southwestern or free surface, which produces large exfolia- the base of Qrd, suggesting that Qrd is inset United States, soil development is dominat- tion slabs. Thus, on a much reduced scale, against Qre. Unit Qrd represents a major ed by the accumulation of secondary calcium exfoliation is acting at all the free surfaces of aggradational episode that may have locally carbonate (CaCO3). Many studies have used the cliff dwelling caves and has produced buried Qre; however, Qre could possibly soil profile mass of CaCO3 and published some striking examples of small-scale pres- mark the base of an aggrading Qrd. The accumulation rates to calculate ages and cor- sure-release exfoliation. The most defining Menaul formation (Qrm) is a thin lens of flu- relate surfaces. However, few estimates of aspect of pressure-release exfoliation here is vial gravel that overlies piedmont deposits the variability of CaCO3 accumulation rates the way it ignores sedimentary bedding to and Qre. The base of unit Qrm is about 23–41 have been made to validate regional correla- conform to the cave openings. Also notewor- m above the Rio Grande. Soils on piedmont tion or age estimates. This study correlates thy, whether intentional or not, is the similar- deposits overlying Qrm are generally similar terrace surfaces by using elevation above the ity of the masonry of the Mogollon builders to Qrd; however, differences in parent mater- modern arroyo, then assesses the regional to the natural architectural style of the exfoli- ial texture make soil-based correlations variability of CaCO3 accumulation rates by ation, particularly where the two are juxta- somewhat ambiguous. Similarities in height comparing the CaCO3 profile mass on ter- posed. (above the Rio Grande) and soil develop- races of the same age. ment on Qrd and Qrm suggest that these two One tributary terrace surface has been STRATIGRAPHY OF RIO GRANDE TER- units may be correlative and are probably dated using Chlorine-36. This age, in con- RACE DEPOSITS BETWEEN SAN associated with the same aggradational junction with the carbonate profile mass, FELIPE PUEBLO AND LOS LUNAS, episode; however, definitive crosscutting yields a CaCO3 accumulation rate for that ALBUQUERQUE BASIN, NEW MEXI- relationships have not been demonstrated. surface. Assuming the accumulation rate has CO, by S. D. Connell and D. W. Love, New The lowest preserved terrace deposit is the been temporally constant, the ages of all ter- Mexico Bureau of Mines and Mineral Arenal alluvium (Qra), which is 3–6 m thick. races within the sequence were determined. Resources, New Mexico Institute of The top of Qra is about 15–21 m above the Correlated terraces were then assigned ages Mining and Technology, Socorro, NM Rio Grande, contains weakly developed soils based on the dated terrace sequence. Using 87801 with Stage I to II+ carbonate morphology, the correlated age and the CaCO3 profile We present stratigraphic and geomorphic and is interpreted to be inset against Qre, mass of each terrace, accumulation rates evidence to refine and update the stratigra- rather than correlative to Qre as originally were calculated for each tributary. If similar phy of post-Santa Fe Group deposits in the interpreted by Lambert. This terrace was terrace elevations in different tributaries rep- Albuquerque Basin. Terrace deposits of the probably deposited during late Pleistocene resent regional geomorphic surfaces, then it Los Duranes, Edith, and Menaul formations time (ca 71–28 ka). The inner valley flood- is clear that there is spatial variability in the were previously defined by Lambert (1968, plain (Qrp, Los Padillas alluvium), which CaCO3 accumulation rates within the UNM, PhD dissertation, 329 pp.) in the Albu- contains up to 25 m of sand and gravel with Socorro Basin. querque area. New geologic mapping delin- minor mud and clay lenses, was probably eates five terrace deposits along the Rio deposited during latest Pleistocene through Grande valley between San Felipe Pueblo Holocene time (ca 20–4 ka). ALLUVIAL AQUIFER METAL PRECIPI- and Los Lunas, New Mexico. These TATES WITHIN A MINERALIZED quartzite-dominated, rounded, pebbly to ESTIMATES OF CaCO3 ACCUMULATION REGION, NORTHERN NEW MEXICO,

MayMay 2000 NEW MEXICO GEOLOGY 49 by Joan M. Otahal, [email protected], Laura Rio lava flows. In addition, there are numer- UPPER SANTA FE GROUP AT SANDIA B. Hagan, and Laura J. Crossey, Department ous intermediate perched water zones locat- NATIONAL LABORATORIES, NEW of Earth and Planetary Sciences, ed between the alluvial and regional MEXICO (SNL/NM), by Michael F. Skelly, University of New Mexico, Albuquerque, aquifers. Hydraulic communication between [email protected], Roy F. Weston, Inc., NM 87131; and Bruce D. Allen, New units is well documented. The shallow allu- 6501 Americas Parkway, Suite 800, Mexico Bureau of Mines and Mineral vial and intermediate perched aquifers are Albuquerque, NM 87110; Sue S. Collins, Resources, 2808 Central SE, Albuquerque, recharged by infiltrating snowmelt, thunder- SNL/NM Dept. 6133, MS-1087, P.O. Box NM 87106 storm runoff, and permitted industrial and 5800, Albuquerque, NM 87185; and John P. The geochemistry of the Red River stream sanitary effluents. Infiltration below the McCord, Duke Engineering Services, Inc., system of northern New Mexico is affected mesa tops is insignificant. The predominant 1650 University Blvd. NE, Suite 300, by natural exposures of sulfide-enriched recharge area for the regional aquifer is locat- Albuquerque, NM 87102 rocks (alteration scars) and extensive waste- ed west of the Los Alamos townsite in the The Sandia North Ground-water Inves- rock dumps associated with mining activi- Sierra de los Valles region east of Valles tigation is currently studying the occurrence ties. Both environments generate acidic, caldera. This recharge area extends eastward of trichloroethene (TCE) in ground water at metal-laden water that infiltrates the ground- below the deeply cut canyons on the plateau. concentrations exceeding the EPA’s Maxi- water system discharging into the Red River, Hence, the intermediate perched aquifers mum Contaminant Level (MCL) of 5 ppb. significantly affecting the geochemistry of located below the saturated alluvial systems Studies completed include drilling/ the stream system. Geochemical analysis of act as a supplemental recharge source to the installing ground-water monitoring wells, aquifer sediments is an important compo- regional aquifer. The observed piezometric soil-vapor surveys, borehole geophysics, col- nent to environmental assessments of hydro- surface in the regional aquifer rises west- loidal borescope surveys, ground-water age logic systems like Red River. This investiga- ward from the Rio Grande in White Rock dating, and quarterly monitoring. tion explores the spatial and vertical variabil- Canyon and across the plateau towards Ground water in the study area occurs ity of the metal precipitates in the shallow Sierra de los Valles. Topographically, the land both in the regional aquifer and in a localized alluvial aquifer with respect to the (a) source surface also rises westward from 5,400 ft shallow ground-water system along the east- of acid rock drainage (ARD), (b) associated (1,645 m) at the Rio Grande to 10,400 ft (3,170 ern margin of the Albuquerque Basin. The ground-water chemistry, and (c) site-specific m) at Pajarito Mountain over a lateral dis- regional aquifer is Albuquerque’s drinking hydrology and aquifer characteristics. tance of 14 mi (23 km). Therefore, the piezo- water source and is 500–600 ft deep in uncon- The Hansen Creek locality is located along metric surface for the regional aquifer is a solidated sediments of the upper unit of the an inferred ground-water flow path below an subdued reflection of plateau topography. Tertiary Santa Fe Group. Flow direction in extensive alteration scar, a natural source of Water in the regional aquifer is under phreat- the study area is north–northwest toward ARD. The Capulin Canyon locality is located ic conditions in the western and central por- municipal well fields. along an inferred ground-water flow path tions of the plateau, and partially confined to The shallow system consists of multiple, below a mining-related waste-rock dump. fully artesian conditions near the river. There perched saturated intervals 175–275 ft above Environmentally available metals were are numerous springs in White Rock Canyon the regional aquifer. This system has been extracted from aquifer sediment by a strong that emerge from the regional aquifer where identified only in the north-central portion of acid technique and the relative concentra- an estimated 6,000 ac-ft/yr (740 ha-m/yr) is Kirtland Air Force Base and has a flow direc- tions of Al, Cu, Fe, Mn, Mo, and Zn were discharged into the river. Collectively, this tion to the southeast. This system probably is determined. Particle size analysis and limit- picture suggests a classic regional ground- controlled by fine-grained sediments within ed SEM examination were conducted on water circulation pattern originating below the alluvial-fan facies and does not appear to selected samples. Metal extraction analysis of the topographic highs on the west and mov- be hydraulically connected to the regional the < 2-mm-size fraction reveals a strong dif- ing east-southeast toward the river. aquifer in the study area. The source of the ference between the Capulin and Hansen Below Pajarito Plateau, the regional water in the shallow system is still under secondary precipitates and metal concentra- aquifer is primarily located in Santa Fe investigation, although an anthropogenic tions. For example, iron concentrations at the Group sediments. These ancestral Rio origin (such as leaking water-supply infra- shallow Capulin location range up to 27 Grande floodplain deposits fill a Miocene- structure) is currently suspected. wt%, compared to 2–7 wt% at the Hansen aged trough at the base of the Bandelier Tuff. TCE has been detected in 5 of 12 shallow- location. Copper values range from 60–680 This Miocene axial depression is a northeast system monitoring wells and exceeds the ppm in the sediment at Capulin and 20–50 to southwest trending basin extending from MCL at 3 of the 5 locations. Other chlorinat- ppm in the sediment at Hansen. Santa Clara Canyon on the north to Ancho ed compounds have been detected in some of Combined with results of previous stud- Canyon on the south. The Puye Formation is the shallow-system wells at concentrations ies, examination of metals precipitated in sandwiched between these two units, and below their respective MCLs. This low-level aquifer sediments supports differential metal portions of it (i.e., Totavi Lentil) hydraulical- contamination is laterally widespread yet mobility between the two sites. This analysis ly dominate the flow field. The aquifer trans- discontinuous. To date, investigations of sur- of the behavior of metals combined with the mitting characteristics within these sedi- face releases to identify potential ground- existing hydrochemical data adds to our ments vary due to differences in lithology water contaminant sources in the study area understanding of surface-water contamina- and formation thickness. Within high-yield- are inconclusive, but a likely candidate is an tion within the Red River valley. ing zones, lateral flow rates vary from 100 to extensive underground waste-water system. 350 ft/yr (30 to 107 m/yr); however, flow HYDROGEOLOGY OF THE GROUND- rates within lower-yielding zones are only FOCUSED GROUND-WATER RE- WATER FLOW SYSTEM NEAR LOS 20–50 ft/yr (6–15 m/yr). Separation of deep CHARGE THROUGH PIPES IN CAL- ALAMOS, NEW MEXICO, by Stephen G. ground-water circulation patterns from shal- CIC HORIZONS, by G. Rodriguez-Marin, McLin, [email protected], Los Alamos low canyon-bottom infiltration can also be J. B. J. Harrison, and J. M. H. Hendrickx, National Laboratory, P.O. Box 1663, MS- inferred from major-ion water chemistry. Department of Earth and Environmental K497, Los Alamos, NM 87544 These analyses suggest that fast-moving Science, New Mexico Institute of Mining The regional aquifer located below Pajarito recharge waters that originate near Sierra de and Technology, Socorro, NM 87801 Plateau is the only sustainable water source los Valles on the west, or that move within The soils on the La Mesa and Las Cañas sur- for municipal use. This aquifer is separated the Totavi, have a calcium-bicarbonate char- faces (New Mexico) are underlain by an from the ground surface by saturated alluvi- acter. However, slower-moving or deeply cir- indurated calcic horizon that is considered um within some large canyons and several culated waters in the lower Santa Fe have a impermeable for soil water. However, an hundred feet of unsaturated volcanics, sodium-bicarbonate character. important feature of this horizon is the pres- basalts, and sedimentary debris shed from ence of pipes that are filled with permeable the Jemez volcanic pile and the Cerros del CONTAMINATION IN A SHALLOW soil materials and, thus, may act as water Rio lava flows. In addition, there are numer- GROUND-WATER SYSTEM IN THE conduits during periods with precipitation.

5500 NEW MEXICO GEOLOGY May 2000 During the installation of a gas pipeline on tropods, echinoderms, bryozoans, calcareous central New Mexico. The Acanthoceras amphi- the La Mesa surface in October 1998 we have algae (phylloid algae, Epimastopora, rarely bolum Zone is of middle Cenomanian age. inspected more than 280 pipes along a 32- Archaeolithoporella, ?Anthracoporella, Eflugelia), km-long trench with a depth of 2.2 m. fusulinids, smaller foraminifers (mostly cal- DIPLODOCID (DINOSAURIA: SAURO- Average pipe density varies from about one civertellid forms, also Bradyina sp., B. lucida, PODA) SKULL AND JAW MATERIAL pipe in every 14–38 m2, average pipe distance B. magna, Climacammina, Diplosphaerina, FROM THE UPPER JURASSIC MORRI- from 22 to 58 m, and average pipe diameter Endothyra, Syzrania bella, Syzrania sp., SON FORMATION, CENTRAL NEW from 4.2 to 8.5 m. Approximately 15–19% of Tetrataxis, Tuberitina), ostracods, Tubiphytes, MEXICO, by Andrew B. Heckert, hecker- the total land surface is occupied by pipes. rare serpulids, and trilobite fragments. Most [email protected], Department of Earth and Generally, wetting fronts inside the pipes limestones contain a diverse biota indicating Planetary Sciences, University of New were deeper than in adjacent areas. Our a shallow, normal-marine depositional envi- Mexico, Albuquerque, NM 87131; Spencer study suggests that pipes in indurated calcic ronment within the photic zone (presence of G. Lucas, Ronald E. Peterson, Rodney E. horizons cause considerable focused algae). A few samples (e.g. sample RM 37) Peterson, and N. V. D’Andrea, New Mexico recharge in arid New Mexico. are characterized by a low diversity biota Museum of Natural History and Science, pointing to a restricted, shallow-marine envi- 1801 Mountain Road NW, Albuquerque, STRATIGRAPHY AND FACIES OF THE ronment. The dominance of muddy carbon- NM 87104 PENNSYLVANIAN–PERMIAN TRAN- ate textures (different types of wackestones) The gigantic sauropod dinosaurs are the SITION AT ROBLEDO MOUNTAIN, indicates low-energy water conditions near most commonly recorded vertebrates from DOÑA ANA COUNTY, NEW MEXICO, or just below the wave base. Grainstones, the Upper Jurassic Morrison Formation, by K. Krainer, Geology Institute, University which formed under higher-energy water including famous dinosaur quarries in of Innsbruck, Innrain 52, Innsbruck, conditions (shoal environment), are rare. Colorado, Utah, Wyoming, and Oklahoma. Austria; S. G. Lucas, New Mexico Museum However, sauropod skulls remain exceeding- of Natural History and Science, 1801 EXCEPTIONALLY PRESERVED INVERTE- ly rare. We report an incomplete skull and Mountain Road NW, Albuquerque, NM BRATE FAUNA FROM THE UPPER lower jaws (NMMNH P-26082) from 87104; and B. S. Kues, Department of Earth CRETACEOUS PAGUATE MEMBER OF NMMNH locality 3282, the Peterson Quarry, and Planetary Sciences, University of New THE DAKOTA FORMATION, RIO which is the most productive Jurassic Mexico, Albuquerque, NM 87131 PUERCO VALLEY, SANDOVAL COUN- dinosaur locality in the state. The specimen An apparently complete section that encom- TY, NEW MEXICO, by P. L. Sealey and S. was found in a float block but is clearly asso- passes the Pennsylvanian–Permian bound- G. Lucas, New Mexico Museum of Natural ciated with the numerous other specimens ary is exposed just west of Robledo History and Science, 1801 Mountain Road from the Peterson Quarry. The float block 1 Mountain (SW ⁄4 sec. 34 T21S R1W). Thomp- NW, Albuquerque, NM 87104 was found close to a quarry wall and was son (1954, Univ. Kansas Pal. Contrib.) The Acanthoceras amphibolum Zone is present probably derived from the south end of the described this section as Virgilian Fresnal in the Paguate Member of the Dakota quarry as it was worked from 1989–1995. Group overlain by Wolfcampian strata of the Formation on the western side of the Rio The partially disarticulated and crushed Bursum Formation?, Bursum Formation, and Puerco northwest of Albuquerque, New skull consists of an incomplete right premax- Hueco Limestone. Subsequent workers Mexico, at NMMNH localities 3263, 4406– illa and maxilla, incomplete left mandible, either reiterated that Bursum strata are pre- 4409, and 4429–4432. In this area, the Paguate several palatal(?) skull fragments, and 33 sent at Robledo Mountain or stated that the Member is approximately 22 m thick, and teeth, all preserved in two matrix blocks. Of Hueco rests directly on Virgilian strata. Our invertebrate fossils occur in ripple-laminated the teeth, 19 are associated with the larger detailed measured section through the sup- and concretionary calcareous sandstone, matrix block and 14 with the smaller one. posed Bursum interval at Robledo Mountain 15–16 m above its base. Diplodocid synapomorphies present in P- indicates that there is no lithologic basis for A. amphibolum is fairly common in the 26084 include the presence of slender, peg- identifying Bursum Formation there and that Paguate Member of the Dakota Formation in like teeth that lack labial grooves and a ven- most, if not all, “Bursum” strata should be the study area. Numerous specimens were trally deflected anteroventral margin of the assigned to the Hueco. Thompson’s assign- collected, including a fairly complete shell dentary. This fossil is important because it is ment of strata at Robledo Mountain to the with body chamber, several other adult spec- the only sauropod skull and jaw material Bursum was purely biostratigraphic, in imens, many partial shells, and a few inner recovered from the Jurassic of New Mexico, which “Bursum” referred to Wolfcampian whorls. A. amphibolum is characterized by and one of less than a dozen Morrison strata below the lowest local occurrence of ventrolateral horns on the later whorls and a Formation diplodocid skulls known. The the fusulinid Schwagerina. broadly arched venter with a very low mid- preserved skull is too incomplete to assign to We measured 56.5 m of strata at the base of ventral ridge. It is distinguished from a specific genus, but the numerous sauropod the Hueco, beginning on top of a several- Acanthoceras alvaradoense in possessing postcrania from the locality should, when meters-thick cliff of massive limestone. The clavate upper ventrolateral and siphonal prepared, facilitate genus-level identification lower part (0–29 m) is composed of gray, bed- tubercles on the early whorls, rather than of the sauropods at the Peterson Quarry. ded limestones, nodular limestones, and nodate ones. A lack of constrictions on the Although some of the preserved teeth were intercalated reddish, marly shale with lime- early whorls further distinguishes our speci- clearly unerupted, the presence of over 30 stone nodules. Bioclastic wackestones and mens from A. alvaradoense. teeth suggests that nearly the entire dentition bioclastic peloidal wackestones are the most A well-preserved bivalve and gastropod was preserved, and recovery of additional abundant microfacies; subordinate are fauna is associated with A. amphibolum. This sauropod teeth from the Peterson Quarry peloidal grainstones and wackestones, oncol- fauna includes Pycnodonte kellumi (Jones), suggests that more sauropod skulls might be ithic wackestones, and fusulinid wacke- Exogyra trigeri (Coquand), Avicula gastrodes? found there in the future. stones. Nodular limestones are composed of Meek (new record for Paguate), Legumen bioclastic peloidal wackestones, grainstones, ellipticum Conrad, Ostrea beloiti Logan, Grano- PRELIMINARY TAPHONOMY OF THE and fusulinid wackestones/packstones. The cardium enstromi (Bergquist), Idonearca depres- UPPER TRIASSIC SNYDER QUARRY upper part (29–56.5 m) consists of thin- to sa White (new record for Paguate), and AND SIGNIFICANT CONCENTRA- thick-bedded, gray limestones and two Turritella sp. Other than a single specimen of TIONS OF TITANIUM IN THE SPECI- nodular limestone beds. The dominant Turrilites acutus americanus Cobban & Scott, MENS, by Kate E. Zeigler, kaerowyn microfacies is again bioclastic wackestone; all ammonites collected are A. amphibolum. @unm.edu, and Andrew B. Heckert, Depart- subordinate are bioclastic grainstone/pack- The occurrence of the Acanthoceras amphi- ment of Earth and Planetary Sciences, stone, peloidal wackestone, algal wacke- bolum Zone in the Rio Puerco valley suggests University of New Mexico, Albuquerque, stone, and boundstone formed of algal correlation with the Paguate Member of the NM 87131; and Spencer G. Lucas, New crusts. The limestones contain bioclastic Dakota Formation northeast of Thoreau, in Mexico Museum of Natural History and remains of brachiopods, bivalves, gas- the Laguna area, and other locations in west- Science, 1801 Mountain Road NW, Albu- querque, NM 87104

MayMay 2000 NEW MEXICO GEOLOGY 51 One of the key questions surrounding mass Museum of Natural History and Science, imens representing isolated and associated accumulations of fossil bones of any age is 1801 Mountain Road NW, Albuquerque, skeletal elements are here referred to the mechanism of the bone-bed’s formation. NM 87104; J. W. Schneider, Institute of eusuchia indet. P-27840 is represented by Various characteristics of the assemblage can Geology, Freiberg University of Mining portions of the skull roof including much of be used to interpret how the bones were and Technology, Freiberg, Germany; and T. the frontal and parietals, and other regions of deposited en masse. Depending upon the Martens, Museum der Natur, Gotha, the skull including the jugal, basioccipital, site, several explanations can be proposed. Germany quadrate, fragments of the maxillae, and por- The Upper Triassic Snyder Quarry Recently, we described vertebrate fossils tions of both dentaries. The postcranial skele- (NMMNH locality L-3845) in the Petrified from conglomerates interbedded with ton is represented by fragmentary vertebrae, Forest Formation of the Chinle Group in marine Virgilian strata of the uppermost limb fragments, a partial ilium, and osteo- northern New Mexico has excellent potential Wild Cow Formation at Placitas. We add to derm fragments. The lack of occlusion pits to further explore the question of bone-bed this vertebrate record the temnospondyl medial to the maxillary teeth suggests that P- formation. The main bone-bearing horizon is amphibian family Dissorophidae. The best 27840 does not represent an alligatoroid. less than 0.3 m thick and, in initial strati- specimen is the apex of a laterally com- Other less complete specimens from the graphic assays, the northeastern edge of the pressed neural spine, covered with sculp- Fruitland and Kirtland Formations in the unit, as well as the next stratigraphically tured dermal bone and bearing anterior and NMMNH collection may belong to the same higher conglomeratic unit, slope gently posterior articulations for dorsal dermal taxon. These are characterized by relatively upwards until they are truncated by a hori- plates of an external series. This suite of char- anteroposteriorly elongate osteoderms that zontal conglomeratic bed. An initial interpre- acters is unique to certain problematic and lack keels and have broad overlap regions, tation suggests that the bones are concentrat- bizarre dissorophids from the Lower and dorsal vertebrae with procoelus centra. ed in an ancient stream channel with a depo- Permian of Texas often referred to the genus P-26260 is a partial left dentary that closely sitional dip down to the southwest. Aspidosaurus. The Placitas fossils represent resembles those of P-27840. It includes the Examination of the lateral extent of the main the only New Mexican and the first roots of 6 teeth, one complete tooth, and por- bone horizon and the condition of the bones Pennsylvanian evidence of a form identifi- tions of the symphyseal region. themselves will help to resolve further how able with, or similar to, that genus. A possible second eusuchian taxon from the assemblage developed. The bone bed Higher in the section, a variety of fossils the De-na-zin Member is represented by a itself is exceptionally diverse with both occur in the upper part of the Abo Formation single specimen (P-26234) that includes a invertebrates and vertebrates preserved. All at NMMNH locality L-3922. This locality has nearly complete osteoderm and an associat- of the larger bones are disarticulated except produced bones of a pelycosaur, several ed femur. The osteoderm of this specimen for some aetosaur scutes, and some of the plants, abundant conchostracans and isolat- bears a relatively high, narrow, and posteri- individual coelophysids are still associated. ed wings of a blattoid insect. The best blat- orly pointing median ridge and is similar to Also, exceptionally fragile skeletal elements toid specimen is the proximal two-thirds of a those pertaining to the crocodylian are preserved together with larger and left tegmen. The proximal series of subcostal Akanthosuchus from the lower Paleocene stronger bones. vein branches are indistinct, as is the bound- Nacimiento Formation of the San Juan Basin. Bones from the Snyder Quarry are notable ary between distal branches of the subcostal Isolated bulbous teeth probably represent for their deep black color and, in some cases, and proximal branches of the radial veins. posterior crushing teeth of an alligatoroid, light purple iridescent sheen, preservation However, the proximal branches of the radi- suggesting that the second eusuchian above that is unique to the Chinle. A fragment of an al, medial, and cubital veins and the veins of is an alligatoroid, or that there is at least a aetosaur scute from the quarry was analyzed the anal lobe are clear, and, though the medi- third eusuchian crocodylian present in Late using an energy dispersive spectrometer al seems relatively widely separated from the Cretaceous faunas of the San Juan Basin. (EDS) on a JEOL Scanning Electron Micro- radial and cubital veins, the specimen indi- scope (SEM) at the University of New Mex- cates the family Phyloblattinidae. This cos- ADDITIONAL REMAINS OF “MESO- ico. To account for the color of the bones, we mopolitan family occurs in North America SUCHIAN” GONIOPHOLIDID CROC- expected to find a high degree of manganese from Desmoinesian to Wolfcampian time, ODILIANS FROM THE UPPER CRETA- present in the fragment. However, the SEM and its species are useful as biostratigraphic CEOUS (UPPER CAMPANIAN) FRUIT- spectra recorded very low levels of man- indicators, but more and better specimens LAND AND KIRTLAND FORMA- ganese and unexpectedly high amounts of are needed from Placitas for that purpose. TIONS, SAN JUAN BASIN, NEW titanium in the scute fragment. The titanium The conchostracans are similar to the MEXICO, by Thomas E. Williamson, New would explain the iridescence seen on the German taxa Lioestheria monticula Martens Mexico Museum of Natural History and surface of numerous bones. A probable from the Tambach Formation and to L. Science, 1801 Mountain Road NW, Albu- source of the titanium is the volcanic detritus pseudotenella Martens from the Oberhof querque, NM 87104 found in the Chinle sediments, especially the Formation, both strata of Early Permian The goniopholidid crocodylian “Goniopholis” bentonitic and smectitic muds possibly (Wolfcampian equivalent) age. kirtlandicus is based on a partial skull from derived from the volcanics associated with the Upper Cretaceous Kirtland Formation. the opening of the Gulf of Mexico. If the EUSUCHIAN CROCODILIANS FROM Isolated teeth and osteoderms from a large source of the titanium is volcanogenic, then it THE FRUITLAND AND KIRTLAND goniopholidid are relatively common in the is highly probable that portions of the bone FORMATIONS, SAN JUAN BASIN, Fruitland and Kirtland Formations and have are being replaced by a mineral such as NEW MEXICO, by Thomas E. Williamson, been referred to this taxon. Additional ilmenite. Further analysis of clay samples New Mexico Museum of Natural History remains of a large goniopholidid including and multiple bone fragments throughout the and Science, 1801 Mountain Road NW, associated dorsal osteoderms and dorsal ver- quarry and from different species will per- Albuquerque, NM 87104 tebrae, isolated limb elements, and associat- haps yield further information about the ele- Late Cretaceous eusuchian crocodilians are ed osteoderms and a partial dentary are ments that were incorporated into the bones generally rare in the Upper Cretaceous (late reported here. These specimens add new as they fossilized. Campanian–Maastrichtian) Fruitland and information about the “mesosuchian” croco- Kirtland Formations. They are represented dilian from the Fruitland and Kirtland NEW VERTEBRATE AND INVERTE- primarily by isolated teeth, osteoderms, and Formations. Typical goniopholidid dorsal BRATE FOSSILS FROM THE UPPER postcranial fragments. Previously, these have osteoderms from the Fruitland and Kirtland PALEOZOIC WILD COW AND ABO been referred to Allognathosuchus, Brachy- Formations are extremely transverse, flat, FORMATIONS, PLACITAS, SAN- champsa, Crocodylus, and Leidyosuchus. How- marked with large and deep pits on the dor- DOVAL COUNTY, NEW MEXICO, by J. ever, these diagnoses are based on inade- sal surface, have large overlap areas, and lack M. Rowland and S. G. Lucas, New Mexico quate material. A partial skull and skeleton lateral articular surfaces. Dorsal vertebrae Museum of Natural History and Science, (NMMNH P-27840) from the De-na-zin are amphicoelus and have very elongate lat- 1801 Mountain Road NW, Albuquerque, Member, Kirtland Formation, and other spec- eral processes. A complete right femur (P-

5522 NEW MEXICO GEOLOGY May 2000 31551) is relatively large (length = 280 mm) have an influence on deposition at shallower Drive, Maywood, NJ 07607; Bruce D. Allen, and robust and bears a well-developed del- stratigraphic levels. When properly integrat- New Mexico Bureau of Mines and Mineral toid crest. A partial edentulous right dentary ed with well data and other sources of infor- Resources, 2808 Central Avenue SE, (NMMNH P-30064) is the first reported for a mation, good quality 3-D seismic data allow Albuquerque, NM 87106; and Kirsten M. Late Cretaceous goniopholidid from North the geoscientist to produce maps of subsur- Menking, Vassar College, Poughkeepsie, America. It is relatively large (preserved face features more accurately and in a frac- NY 12604 length = 427 mm) and robust (maximum tion of the time that might be spent using Estancia Basin in central New Mexico is a transverse diameter behind symphysis = 78 well data or 2-D seismic data alone. closed basin comprising an area of about mm; maximum depth = 88 mm; length of The "down-sides" to working with 3-D 5,000 km2 and has been the focus of many symphysis = 143 mm). Ten complete or par- seismic data are: (1) Availability of data. 3-D studies of changes in Late Pleistocene pluvial tial alveoli are preserved. The third and seismic data are expensive to collect and Lake Estancia. It is generally believed that fourth alveoli are subequal (length = ~30 therefore tend to be collected only where the ground-water discharge from the Manzano mm; width = ~18 mm), partially confluent project objectives make applying the technol- Mountains west of the basin was mostly with raised margins, and are the largest of ogy economically feasible (e.g., petroleum responsible for maintaining the lake during the tooth row. The other alveoli are relatively industry). (2) Availability of software. 3-D lowstands, with relatively little contribution widely spaced. The alveoli posterior to this seismic interpretation software can be expen- from the surface water. However, an are relatively small (length of the fifth alveo- sive and takes some training to utilize prop- unknown volume of surface water runoff lus = 13 mm; width of the fifth alveolus = 11 erly. (3) Over-reliance on seismic data. 3-D contributed to the hydrologic balance during mm) and decrease in size posteriorly. The seismic data are still seismic data, and vari- lake highstands. Surface water modeling of first two alveoli are nearly the diameter of ous pitfalls (e.g., velocity artifacts) that can Estancia Basin is in progress to estimate past the third and fourth. Two associated osteo- haunt the 2-D seismic interpreter can also surface water runoff and to understand the derms are circular, relatively thick, and dor- afflict the 3-D seismic interpreter. Integration effects of climate change. sally convex with large and deep pitting on of other data types is critical. 4) Over-reliance Estancia Basin does not have a single dis- the dorsal surface. They may represent dor- on technology. Despite the spectacular charge point, and a number of subwater- sal armor from the cervical region. images that may be obtained from 3-D seis- sheds drain to the center of the basin. Today, Goniopholidid remains are relatively more mic data volumes, a good geologic back- no surface runoff from the Manzano abundant in the coastal, more marine-influ- ground is necessary in order to ask the right Mountains reaches the center of the basin, enced Fruitland and lower Kirtland For- questions of the data set and properly inter- which contains saline lakes (playas) where mations (Hunter Wash and Farmington pret the results. ground water escapes by evaporation. For Members) than in more upland deposits rep- surface runoff modeling, the drainage area of resented by the upper Kirtland Formation EMPIRICAL AND PHYSICAL METHODS the entire watershed was subdivided into 22 (De-na-zin and Naashoibito Members) sug- FOR REGIONAL SOIL-MOISTURE subwatersheds ranging in size from about 20 DISTRIBUTION USING LANDSAT TM gesting that it preferred costal habitats. km2 to 1,300 km2 using USGS 30-m DEM and IMAGES, by P. R. H. Neville and C. K. topographic parameterization software VISUALIZATION OF SUBSURFACE Bales, Earth Data Analysis Center, Uni- TOPAZ (Garbrecht and Martz, 1995). A sur- STRATIGRAPHY, STRUCTURE AND versity of New Mexico, Albuquerque, NM face runoff model was developed for each ROCK PROPERTIES WITH 3-D SEIS- 87131; and J. B. J. Harrison and J. M. H. Hen- subwatershed using the modeling system MIC DATA, by Bruce Hart, New Mexico drickx, Department of Earth and Environ- SWAT (Arnold et al., 1996). SWAT is a physi- Bureau of Mines and Mineral Resources, mental Science, New Mexico Institute of cally based distributed parameter continu- New Mexico Institute of Mining and Tech- Mining and Technology, Socorro, NM ous time hydrologic model that simulates the nology, Socorro, NM 87801; and Steve 87801 processes of surface runoff, river routing, Ralser, Robin Pearson, Matt Herrin, Scott Although the problem of regional soil-mois- evapotranspiration, infiltration, and subsur- Cooper, and Dan Leiphart, Department of ture distribution appears trivial, no method- face flow. Hydrologic properties of soil were Earth and Environmental Science, New ology has been developed to date that is truly obtained from USDA SCS soil surveys and Mexico Institute of Mining and Tech- capable of reliable soil-moisture measure- were confirmed by field determination at nology, Socorro, NM 87801 ments over large areas using satellite data. In selected points in the basin. Geologists commonly have a problem this study we will test an empirical regres- The model was calibrated on a relatively extrapolating structural and stratigraphic sion method and a physical Surface Energy small watershed (drained by Tajique Creek) features exposed at the surface into the sub- Balance Algorithm for Land (SEBAL) devel- comprising an area of about 50 km2. Due to surface. At times, borehole information or oped by Bastiaanssen. The test is conducted relatively high relief of the basin, the precipi- geophysical data (e.g., 2-D seismic, gravity, in the Estancia Basin (New Mexico) on tation and temperature interpolation algo- aeromagnetic data) are available to guide the October 3, 1998, under relatively moist con- rithms reflected elevation differences. interpretation, but these data may lack reso- ditions. A significant regression (R2 equal 67) Sensitivity analyses indicate that precipita- lution or be ambiguous to interpret. Whether was determined between volumetric soil- tion and temperature are the most important the project has an "applied" (e.g., resource water content in the top 5 cm of the soil and variables in model simulations, followed by extraction) or "academic" (e.g., tectonic bands 1, 2, 3, 4, 5, 6, and 7 of the Landsat TM. vegetation type and soil roughness parame- reconstruction) focus, the results of the geol- It was also found that the evaporative frac- ters. Least important are channel and sub- ogist's interpretation can have a significant tion is much more stable during the day than basin geometric characteristics. Results indi- impact. Even seasoned geologists make mis- the Bowen ratio, which is critical for applica- cate that some calibration is required to takes, of various magnitudes, with ambigu- tion of SEBAL. The evaporation rates deter- match model results to the observed values, ous data. mined with SEBAL and the surface soil- and several model runs using estimates of High-quality 3-D seismic data provide the water contents determined with the empiri- climate change are presented to illustrate the geoscientist with unparalleled opportunities cal method show good qualitative agree- importance of atmospheric forcing on the for imaging and (correctly) interpreting sub- ment. These first results are promising, but hydrologic balance in Estancia Basin. Future surface structure, stratigraphy and rock more analysis needs to be done. work includes coupling of SWAT with a properties. Using data from northwest and ground-water model (MODFLOW) and an southeast New Mexico, we illustrate how 3- energy balance (lake) model, and comparing D seismic data can be used on an interactive SURFACE WATER RUNOFF MODELING surface runoff and hydrologic balance with workstation to image the subsurface. We see OF ESTANCIA BASIN, NEW MEXICO, scenarios of global climate change. features (stratigraphy, structure) that are not by Kamran H. Syed and Roger Y. Anderson, visible at the surface. Different structural Department of Earth and Planetary Sci- configurations may be present at different ences, University of New Mexico, Albu- APPLICATION OF USER-INTERACTIVE stratigraphic levels, and deep structures may querque, NM 87131; Nabil. G. Shafike, WEB PAGES FOR PRESENTATION OF Hydro-Tech Engineering, 68 Maybrook

MayMay 2000 NEW MEXICO GEOLOGY 53 LARGE MAP-LINKED GEOLOGICAL/ Earth’s surface, broadcast signals that of Biology, WRRI, and NMBMMR. The main ENGINEERING DATABASES, by Adam include information about the satellite’s posi- points of the study were to produce a com- Rewis, [email protected], Department of tion and the time at which the signal was pletely digital form of the published map, Computer Science, New Mexico Institute broadcast. Interpretation of these signals which includes the geologic map itself and of Mining and Technology, Socorro, NM allows the precise position of the receiver on, the description of the geologic units found on 87801; and Brian S. Brister, New Mexico or above, the Earth’s surface to be deter- the map. The map was created in the Bureau of Mines and Mineral Resources, mined. GPS receivers range from simple, Arc/Info and subsequently placed into an New Mexico Institute of Mining and Tech- inexpensive, hand-held models that allow Arc/Info and Arc/View file format upon nology, Socorro, NM 87801 determination of positions to within ± 30 m completion. The internet has become a common and pop- in the horizontal direction to high-end multi- The initial step taken in this project was to ular method of making large, public-domain receiver systems that provide positions accu- scan a scribe sheet used to create GM-57. databases of technical information, and rate enough to track continental motion. Scribe sheets were used in the cartographic detailed maps, available to the public. There are many applications of GPS tech- process for NMBMMR map production Successful current examples from the New nology to geosciences. Among the most basic before 1997. The original image was a TIFF Mexico Bureau of Mines and Mineral is recording and storing sample locations as file that was then converted, using Arc/Info, Resources web pages are: latitude and longitude, or as UTM coordi- into a grid file (Arc/Info raster file format) • STATEMAP Program geologic maps: nates, making translation of sample locations that was georeferenced to UTM, Zone 13 http://geoinfo.nmt.edu/maps/home.html into an ARCINFO format more seamless. NAD 27. This grid was scanned from a scribe • Oil and gas maps: http://geoinfo.nmt. Many GPS receivers can download stored sheet supplied by Glen Jones of NMBMMR. edu/resources/petroleum/poolmaps.html data directly to a personal computer. An Next, the coverage was essentially traced on • New Mexico subsurface database: http:// application of relatively high-end GPS analy- the computer using the grid as a backdrop to geoinfo.nmt.edu/data/ims/nm-ims.html sis to geology is precise mapping of locations create a coverage. This method was used Continued petroleum industry interest in of geological contacts or features in the field. instead of digitizing a hard copy of the origi- the Morrow Formation natural-gas play This can be done to centimeter-level preci- nal map because it was felt that copying the (Delaware Basin, southeast New Mexico) sion, if necessary, by using two receivers, one grid and producing a GIS coverage would be and feedback from petroleum explorationists as a base station that remains at a fixed loca- more precise and geologically accurate. The suggested the desirability of creating an tion, and one as a mobile receiver that is car- tracing of the grid was done within the internet research pool for public-domain ried around and used to map the features of Arc/Info program using Arctools com- information about the play. The Morrow interest. By processing the base and mobile mands. Internet Project is a cooperative effort data sets together, a high-precision map can This process was completed after going between the New Mexico Bureau of Mines be obtained. The co-processing of the two through and fixing all of the necessary edits. and Mineral Resources, New Mexico Tech data sets, called “differential GPS” analysis, The map and description can then be printed Department of Computer Science, New allows error-producing noise in the satellite- out in different forms, whatever may be Mexico Petroleum Recovery Research transmitted data to be corrected, allowing required for use or display. This work creat- Center, and Petroleum Technology Transfer high-precision positions (± 1 cm) to be ed a digital map that is accurate and hope- Council. obtained. Two examples of this type of work fully more useful than the hard copy of the Four products were integrated into the include mapping contacts between subaerial map. This process has been by no means per- Morrow Internet Project: and subglacial lava flows in Marie Byrd fected but is a useful format when converting • A GIS map of the play area (ARCVIEW- Land, Antarctica, and mapping the distribu- a hard copy of a map to digital form. based) containing numerous layers that may tion of volcanic ash layers in a Antarctic ice Therefore, use of this GIS database should be be turned on or off by the user and including fields. These types of maps can be used to done in conjunction with the original hard user-selectable links to other databases. precisely determine the paleo-positions of copy map to ensure a complete understand- • Morrow well production history (MS SQL the West Antarctic ice sheet and also to study ing of the information contained on GM-57. Server-based) accessible as a stand alone, and monitor local ice flow processes. Both of The GIS database is in Arc/Info format and search-by-query database linked to well these data sets were collected and processed has FGDC metadata. spots on the GIS map. in remote field locations, using solar power Seager, W. R., Hawley, J. W., Kottlowski, F. E., • Gas pool (field) reservoir information to recharge the GPS batteries for data collec- and Kelley, S. A., 1987, Geology of east half (ACCESS-based) accessible as a stand alone, tion and the PC batteries for data processing. of Las Cruces and northeast El Paso 1° x 2° search-by-query database linked to pool out- As discussed in Nielsen et al. (1999), GPS has sheets, New Mexico: New Mexico Bureau lines on the GIS map. the potential to become an integral part of of Mines and Mineral Resources Geologic • A bibliography of published geologic and geologic mapping and other field work. Map 57, 3 sheets, scale 1:125,000. engineering literature references pertaining to the Morrow Formation (ACCESS-based) CONVERTING NEW MEXICO BUREAU CONVERTING NEW MEXICO BUREAU accessible as a stand alone database linked to OF MINES AND MINERAL RESOURC- OF MINES AND MINERAL RESOURC- the reservoir information database. ES GEOLOGIC MAP 57 TO DIGITAL ES GEOLOGIC MAP 60 TO DIGITAL Project completion is scheduled for FORM, by Philip Dinterman, Department FORM, by Molly Johnson, Philip Dinterman, August, 2000. A trial version can be accessed of Geological Sciences, New Mexico State Jared Martin, and Stephanie Furgal, via: http://octane.nmt.edu/morrow/ University, Las Cruces, NM 88003; John F. Department of Geological Sciences, New Kennedy, Water Resources Research Mexico State University, Las Cruces, NM APPLICATIONS OF GLOBAL POSITION- Institute, New Mexico State University, 88003; John F. Kennedy, Water Resources ING SYSTEM (GPS) TO EARTH SCI- Las Cruces, NM 88001; Barbara Nolen, Research Institute, New Mexico State ENCE PROBLEMS, by Nelia W. Dunbar, Department of Biology, New Mexico State University, Las Cruces, NM 88001; Barbara [email protected], New Mexico Bureau of University, Las Cruces, NM 88003; and Nolen, Department of Biology, New Mines and Mineral Resources, New Mex- Glen Jones, New Mexico Bureau of Mines Mexico State University, Las Cruces, NM ico Institute of Mining and Technology, and Mineral Resources, New Mexico 88003; and Glen Jones, New Mexico Bureau Socorro, NM 87801 Institute of Mining and Technology, of Mines and Mineral Resources, New Global Positioning System, or GPS, is a satel- Socorro, NM 87801 Mexico Institute of Mining and Tech- lite-based technology that allows location of This project involved the conversion of nology, Socorro, NM 87801 a precise position on, or above, the Earth’s NMBMMR Geologic Map 57, Geology of east This project involved the conversion of surface by triangulation of signals from three half of Las Cruces and northeast El Paso 1° x 2° NMBMMR Geologic Map 60, Geology of or more satellites. The satellites, which orbit sheets, New Mexico (Seager et al., 1987) into southwest quarter of Las Cruces and northwest El at approximately 20,000 km above the digital form using GIS technology. The pro- Paso 1° x 2° sheets, New Mexico (Seager, 1995) Earth’s surface, broadcast signals that ject is sponsored by the NMSU Department into digital form using GIS technology. The

5544 NEW MEXICO GEOLOGY May 2000 project is sponsored by the WRRI, Depart- and Mineral Resources, New Mexico Research Institute, New Mexico State ment of Geological Sciences at NMSU, and Institute of Mining and Technology, University, Las Cruces, NM 88003; Molly the NMBMMR. The purpose of this project Socorro, NM 87801 Johnson, Philip Dinterman, and Jared Martin, was to produce a completely digital form of This project involved the conversion of Department of Geological Sciences, New the GM-60 so that the GIS coverage could be NMBMMR Geologic Map 53, Geology of Mexico State University, Las Cruces, NM used in an aquifer-assessment study. northwest part of Las Cruces 1° x 2° sheet, New 88003; and geology compilation by John W. The initial step taken in this project was to Mexico (Seager et al., 1982) into digital form Hawley, Hawley Geomatters, Albuquer- scan a scribe sheet used to create GM-60. using GIS technology. The majority of this que, NM 87196 Scribe sheets were used in the cartographic process was completed using the Arc/Info This poster is part of a project that was process for NMBMMR map production program with some of the final attribute edit- undertaken to characterize binational aqui- before 1997. The original image was a TIFF ing performed in Arc/View. There were sev- fers in southwestern New Mexico and pre- file that was then converted, using Arc/Info, eral steps involved in completing this project. pare data for an international data exchange into a grid file (Arc/Info raster file format) The initial step was to load the published with the Republic of Mexico. The study is a that was georeferenced to UTM, Zone 13 map into the computer as a warp grid. This continuation of joint efforts by the govern- NAD 27. This grid was scanned from a scribe was done by scanning a scribe sheet supplied ments of the United States and Mexico to sheet supplied by Glen Jones of NMBMMR. by the NMBMMR. Using this grid as a back- identify transboundary aquifers, quantify the Next, the linework was traced on the com- drop, a GIS coverage was created by tracing natural and induced chemical quality of each puter using the grid as a backdrop to create a the grid on the computer using Arc/Info. aquifer, determine the direction of ground- coverage. This method was used instead of This method is called “heads up digitizing” water flow, and develop Geographic Infor- digitizing a hard copy of the original map and tends to be more precise than digitizing mation System coverages. The project result- because it was felt that copying the grid and a hard copy of the original map. Two sepa- ed in a report to the U.S. Environmental Pro- producing a GIS coverage would be more rate coverages were created to contain the tection Agency, Region 6, Dallas, TX. The precise and geologically accurate. The trac- line work. The first coverage contains the report is titled “Trans-International Boun- ing of the grid was done within the Arc/Info lines that form the boundaries for the geolog- dary Aquifers in Southwestern New program using Arctools commands. ic units represented by polygons on the map. Mexico.” This process was completed after going The second coverage contains the line work The study area covers about 37,000 km2 through and fixing all of the necessary edits. for the geologic structures represented on the (14,300 mi2) in southwestern New Mexico Errors were identified by comparing the out- map, ie. faults, folds, etc. Once these cover- and adjacent parts of Arizona and Mexico. put of the digital map with the original scribe ages were completed, and all of the arcs were Most of the study area (31,600 km2, 12,200 sheet. The map and description can then be attributed, topology was built for the “geo- mi2) is in New Mexico with a small portion printed out in different forms, whatever may logic unit” coverage so that polygons could extending into Arizona (1,000 km2, 385 mi2). be required for use or display. This work cre- be produced and attributed. This portion of The hydrogeologic units that form the trans- ated a digital map that is accurate and hope- the work was done using the Arc/View pro- boundary aquifer system extend into Mexico fully more useful than the hard copy of the gram. Within the polygon edit feature a (primarily Chihuahua) and cover the area map. This process has been by no means per- name field was created, which contains a between 31°00' and 33°45' north latitude and fected but is a useful format when converting name for each polygon that corresponds with 106°55' and 109°30' west longitude. a hard copy of a map to digital form. the geologic unit it represents. A symbol field Most of the study area is located in the Therefore, use of this GIS database should be was also used containing values from a con- Mexican Highland section of the Basin and done in conjunction with the original hard structed shade set, which assigned each poly- Range physiographic province. The more copy map to ensure a complete understand- gon a color, and texture where necessary. permeable (primarily alluvial) fill compo- ing of the information contained on GM-60. These shades were created to correspond nents of the deep structural basins that char- The GIS database is in Arc/Info format and with the shades represented on the original acterize the Mexican Highland section form has FGDC metadata. map. Upon completion of the necessary the major aquifers described in the report. Seager, W. R., 1995, Geology of southwest edits, this map and its description can be Topographically closed basins with pied- quarter of Las Cruces and northwest El printed out at a scale of 1:125,000 or can be mont and basin-floor alluvial surfaces grad- Paso 1° x 2° sheets, New Mexico: New modified to fit the specific needs of a project. ing to central playa-lake depressions are des- Mexico Bureau of Mines and Mineral However, this GIS database should be used ignated bolsons (bolsones). Open basins with Resources, Geologic Map 60, 5 sheets, scale in conjunction with the published GM-53. piedmont slopes grading to axial streams 1:125,000. This geologic database is in Arc/Info export that discharge to lower-lying areas are format and has FGDC metadata. CONVERTING NEW MEXICO BUREAU referred to as semibolsons. Seager, W. R., Clemons, R. E., Hawley, J. W., The geologic and hydrostratigraphic data- OF MINES AND MINERAL RESOURC- and Kelley, R. E., 1982, Geology of north- ES GEOLOGIC MAP 53 TO DIGITAL base compilation was completed by Dr. John west part of Las Cruces 1° x 2° sheet, New W. Hawley, with the assistance of students FORM, by Jared Martin, Department of Mexico: New Mexico Bureau of Mines and Geological Sciences and Water Resources from the Department of Geological Sciences Mineral Resources, Geologic Map 53, 3 at NMSU and staff at WRRI. The GIS geolog- Research Institute, New Mexico State sheets, scale 1:125,000. University, Las Cruces, NM 88003; John F. ic and hydrostratigraphic database was cre- Kennedy, Water Resources Research SURFACE GEOLOGY AND HYDRO- ated in Arc/Info format. The GIS database Institute, New Mexico State University, STRATIGRAPHIC UNITS OF THE can be used with ArcView. All files used in Las Cruces, NM 88003; Barbara Nolen, SOUTHWESTERN NEW MEXICO the creation of the poster are available on the Department of Biology, New Mexico State REGION, GIS database and cartography CD-ROM included with the completed University, Las Cruces, NM 88003; and by John F. Kennedy, Water Resources report. Glen Jones, New Mexico Bureau of Mines Research Institute, New Mexico State

MayMay 2000 NEW MEXICO GEOLOGY 55