include allowing growth to become dependent in the Taos region; an inventory and geochemi- on a continually shrinking supply, responsibility cal study of the springs in the Rio Grande gorge; Abstracts for the perpetual pumping, and commitment of a paleoseismic trenching study of the southern future energy resources. Sangre de Cristo fault near Taos; and a study of the geology, hydrogeology, and hydrogeochem- Invited Speakers istry of surface water/ground water interactions along the Rio Grande in northern Taos County. New Mexico Geological Society THE SAN LUIS BASIN OF THE NORTHERN The Taos Soil & Water Conservation District has spring meeting RIO GRANDE RIFT, P. W. Bauer, bauer@nmt. inventoried water wells and mapped the ground edu, New Mexico Bureau of Geology and water and water quality of the county. Over The New Mexico Geological Society annual Mineral Resources, New Mexico Institute of many years, Glorieta Geoscience, Inc., has inves- spring meeting was held on April 18, 2008, at Mining and Technology, Socorro, New Mexico tigated the hydrogeology, aquifer characteristics, Best Western Convention Center, Socorro. Fol- 87801 and hydrogeochemistry of the Taos region. lowing are the abstracts from all sessions given The San Luis Basin (SLB) is the northernmost at that meeting. large basin of the Rio Grande rift. It extends EVOLVING GEOLOGIC UNDERSTANDING about 240 km from Velarde, New Mexico, to OF THE ESPAÑOLA BASIN, RIO GRANDE Keynote presentation p. 52 Poncha Pass, Colorado, encompassing the San RIFT, NORTHERN NEW MEXICO, G. A. Invited speakers p. 52 Luis Valley to the north and the Taos Plateau to Smith, [email protected], Department of Earth Session 1—Rio Grande rift, San Luis and Española the south. The basin is bounded on the east by and Planetary Sciences, University of New Basins p. 53 the Sangre de Cristo Mountains, on the west by Mexico, Albuquerque, New Mexico 87131 Session 2—Stratigraphy, structure, and paleontology p. 55 the Brazos uplift and San Juan Mountains, and Session 3—Rio Grande rift, Albuquerque and southern on the south by the Picuris Mountains. Ranging The Española Basin is central to studies of the basins p. 57 from 30 to 70 km wide, with elevations between Rio Grande rift because it is home to the type Session 4—Hydrogeology and climate p. 59 about 7,000 and 8,000 ft, the basin is said to be —superb badland exposures Poster sessions the world’s largest high-elevation valley. It is of rift-basin fill rich in vertebrate faunas and Paleontology p. 60 nearly the size of the state of Connecticut and datable ash beds. New 1:24,000-scale geologic Stratigraphy, structure, and mapping p. 61 averages less than seven people per square mile. maps (mostly NMBGMR supported by USGS- Hydrology, hydrogeochemistry, climate, and The Rio Grande originates in the San Juan Moun- STATEMAP), aeromagnetic data (USGS), and microbiology p. 64 tains, flows through the valley to Alamosa, runs subsurface stratigraphic studies of the Pajarito Author and subject indices p. 66 south through a gap in the San Luis Hills, and Plateau (LANL) have enhanced geologic under- into New Mexico where it has carved the Rio standing over the last decade. Stratigraphic Keynote Grande gorge. studies and lithofacies mapping by Dan Kon- The SLB is east-tilted, with about 8 km of Neo- ing build upon earlier interpretations by Ray IS A FEW BILLION ACRE-FEET OF STORED gene throw along the normal Sangre de Cristo Ingersoll to show that three primary sediment GROUND WATER REALLY A RESOURCE?, fault, and with a complex hinge zone along the sources filled the basin: erosion of granitic base- J. W. Shomaker, John Shomaker & Associates, western border. In the New Mexican portion of ment and Paleozoic rocks of the Santa Fe Range Albuquerque, New Mexico 87106 the basin, a deep north-south graben (the Taos on the east, recycling of volcaniclastic debris Many river-connected ground water basins store graben) exists along the Sangre de Cristo fault. along with quartzite-rich basement detritus large volumes of water that can’t be pumped The deepest part of the graben is west of Taos derived from the north, and recycling of volcani- and used because the resulting depletion of Pueblo, where the depth to Precambrian rocks clastic debris along with Paleozoic sedimentary the flow of the river would impair the rights is estimated to be >5,000 m. The west-bounding detritus that entered the basin from northeast. of downstream users. The Albuquerque–Belen fault of the Taos graben, known as the Gorge fault, This latter sediment pathway may relate to an Basin, for example, stores several hundred mil- approximately coincides with the Rio Grande ancestral Rio Embudo with headwaters far to the lion acre-feet, which might be compared with the gorge. West of the gorge, a bedrock bench rises east of the modern river, as suggested by upper recent (Year 2000) combined consumptive use of gently to the topographic basin boundary along Miocene basalt flows that probably entered the 184,000 acre-feet in Sandoval, Bernalillo, and the Tusas Mountains. To the north, the bench basin from the Ocate volcanic field. The Santa becomes a complex, intra-rift horst with pre-rift, Valencia Counties, but the Rio Grande is already Fe River also had a larger watershed in the past Oligocene volcanic rocks exposed in the middle of over-appropriated, and an increase in pumping that included the modern upper Pecos Valley. the rift at the San Luis Hills of southern Colorado. would cause still more depletion of the stream. This larger drainage produced coarse-grained, The 65-km-long, northeast-striking Embudo fault The Española and Lower Rio Grande Basins hydrologically important channel deposits rich is a transfer (or accommodation) zone that forms store hundreds of millions of acre-feet more. If in Paleozoic sedimentary detritus and quartzite the complex structural boundary that absorbs the the system is too large for channel-lining to be that covered a broad area of the southern basin differential extension between the east-tilted SLB during the Miocene. Beheading of the earlier practical, to isolate the river from the ground and the west-tilted Española Basin. water system, the stored ground water must Santa Fe River basin may have resulted from rise The southern part of the basin is a physio- of the Santa Fe Range as a ruptured hanging- simply remain in place. graphically and geologically unique terrain wall hinge zone uplift that paradoxically defines Another approach would be to pump the non- known as the Taos Plateau. The to Pleis- higher elevations than the footwall region along renewable ground water, put to beneficial use tocene Taos Plateau volcanic field is the largest the western side of the Española Basin. Research only the portion that actually comes from stor- (7,000 sq km) and perhaps most compositionally in two areas implies that basin subsidence was age, and return the balance to the stream. As the diverse volcanic field in the rift, with at least 35 underway by Oligocene to early Miocene. Near cones of depression expand and eventually reach discrete vents that range from tholeiitic basalt Santa Fe, volcaniclastic strata of the Bishop’s equilibrium, the entire amount pumped would to rhyolite, and that form vent morphologies be at the expense of streamflow—but pumping including shield volcanoes, cinder cones, and Lodge Member of the Tesuque Formation cor- and delivery to the stream must continue for- volcanic domes. The plateau surface shows only relate to the Espinaso Formation and include ever so as to prevent the natural system from minor dissection, with the Rio Grande and its 30 Ma tephra. These deposits overlie ~400 m of replacing the volume withdrawn from storage. major tributaries confined to deep canyons. conglomerate derived from Paleozoic and Pre- Although it seems implausible, this situation is The SLB is host to a variety of recent and ongo- rocks and deposited on basement for- theoretically sustainable if the revenue derived ing geological work. Through the STATEMAP merly denuded during Laramide uplift. These from sale of the stored water has established a program, the NMBGMR has mapped all of the relationships indicate Oligocene foundering of perpetual fund to support the continued pump- 7.5-min quads in the southern SLB. The largest the earlier uplift. Within the Abiquiu embay- ing. One hypothetical system in the Rio Grande ongoing project is a USGS program designed to ment in the northwest part of the basin, pre-25 valley could provide a total of about 6.8 million assess the influence of geology on the availability Ma strata of the lowermost Santa Fe Group thin acre-feet for municipal use (with 50% return of ground water, natural resources, and hazards westward across a staircase of east-facing faults flow) over 100 yrs, at a cost less than large-scale in the central SLB. As part of this study, much to the rift margin. desalination. A very reliable understanding of of the basin was flown for a high-resolution the ground water regime, and the threshold of aeromagnetic survey. Other recent and ongoing subsidence problems due to excessive draw- NMBGMR projects include: a series of detailed A geologic outline of the Albu- down, would be vital. Public-policy implications hydrogeologic assessments of high-growth areas querque Basin, S. D. Connell, connell@gis.

52 Ne w Me x i c o Ge o l o g y May 2008, Volume 30, Number 2 nmt.edu, New Mexico Bureau of Geology and a north- to northeast-tilted half graben whose recharge. 87Sr/86Sr varies from 0.7074 to 0.7156, Mineral Resources, Albuquerque Office, Albu- footwall was the Caballo Mountains. By the end indicating water-rock interaction with variable querque, New Mexico 87106 of deposition of the Hayner Ranch Formation, source rocks. Because these waters have relative- 87 86 The Albuquerque Basin of the Rio Grande rift stratigraphic separation on the Caballo fault sys- ly enriched Sr/ Sr it is likely that the Pennsyl- was the subject of intensive multiagency geologic tem had reached ~1,615 m. During deposition vanian carbonates and granitic basement rocks and hydrogeologic study beginning in the 1990s. of the upper Miocene Rincon Valley Formation, have contributed significantly to their Sr isotopic A focus of geologic study was on new mapping an additional 850 m of stratigraphic separation compositions. Although faults typically do not to better describe and understand the Santa Fe occurred on the Caballo fault block and the act as impermeable boundaries in the shallow Group basin-fill aquifer system, which currently Sierra de las Uvas began to rise, the latter cre- alluvial aquifer, the Seco fault and several of the provides much of the region’s supply of water. ating a west-tilted half graben with ~550 m of Los Cordovas faults act as impermeable bound- Results of these geologic studies led to the cre- stratigraphic separation on its boundary fault. aries in the Servilleta Formation and in the deep ation of a refined stratigraphy that incorporated The two late Miocene basins were linked by a basin-fill aquifer. However, other Los Cordovas subsurface data and improved age control. This gypsum-precipitating playa lake. faults do not act as significant impermeable work illustrated how the structural geometry Deposition of the Camp Rice and Palomas boundaries in the deep aquifer, suggesting vari- and geomorphic evolution of this basin influ- Formations (Pliocene–lower Pleistocene) was able cementation along fault planes at depth. enced the spatial distribution of rock types and accommodated by continued movement along faults and explained why parts of this basin pos- the faults bordering the Caballo Mountains (760 sess more productive water-supply wells than m stratigraphic separation) and Sierra de las GROUND WATER HYDROLOGY AND GEO- others. The Albuquerque Basin is segmented Uvas (100 m stratigraphic separation), as well as CHEMISTRY OF TAOS COUNTY, A. L. Ben- into smaller complexly faulted half-graben sub- by new faults that uplifted the Red Hills, Animas son, [email protected], and R. Gervason, basins by strain accommodation zones. Rifting Mountains, Rincon Hills, northwestern Sierra [email protected], Taos Soil and Water began in late Oligocene time with the creation de las Uvas, Cedar Hills, San Diego Mountain, Conservation District and Robledo Mountains. During this time the of segmented, internally drained sub-basins that This study was undertaken as a project of the ancestral Rio Grande flowed through six basins, were dominated by fluviolacustrine and eolian Taos Soil and Water Conservation District, to with the location and width of the floodplain sediments. By late Miocene time, sandier flu- begin the process of addressing concerns about largely controlled by basin symmetry. Periodic vially dominated extrabasinal sediments associ- ground water resources in Taos County. This is kilometer-scale shifting of the axial river toward ated with the ancestral Rio Grande reached the in a geologically complex area within the San northern part of the basin and ended in playa the Caballo footwall was a response to active faulting and basin tilting. Following deposi- Luis rift basin. To provide baseline data for Taos lakes at the southern end. By early Pliocene time, County, nearly 2,000 water wells have been accu- this axial river flowed through the basin and into tion of the Camp Rice and Palomas Formations (post-0.8 Ma), many pre-existing and new faults rately located using GPS. Water table elevation southern New Mexico. By Plio–Pleistocene time, maps have been prepared and a depth-to-water the axial-river load had coarsened and migrated experienced activity, including 40 m of offset on the Caballo fault. map prepared for laymen. Depth-to-water var- toward the present position of the Rio Grande ies from less than 100 ft along perennial streams valley, where it incised to form a continuous river along the Sangre de Cristo Mountain front to valley. In the Albuquerque–Rio Rancho area, the Session 1—Rio Grande Rift, San Luis and over 1,000 ft in western Taos County. Direction western basin margin is structurally high, and Española Basins of ground water flows can be seen on the water potable ground water is mostly derived from table elevation maps, and recharge sources can consolidated and calcite-cemented Miocene Structural controls on ground be implied for many areas from these maps. sediments. This structurally high western flank water flow and recharge into Deeper wells below 500 ft show effects of a the southern San Luis Basin near also provides shallower targets for petroleum downward pressure gradient and were not used Taos, New Mexico, P. Drakos, J. Lazarus, development in the subjacent Mesozoic strata. for the water table maps. J. Riesterer, Glorieta Geoscience Inc., P.O. Box The structurally lower eastern part of the basin Structure maps on the Servilleta basalt were under Albuquerque contains younger, coarser, 5727, Santa Fe, New Mexico 87502; K. Sims, Department of Geology and Geophysics, made and used in conjunction with aeromag- and thicker Plio–Pleistocene strata that produce netic data to map the numerous faults within some of the largest yields and generally higher Woods Hole Oceanographic Institution, Woods the study area. Water table differences are seen quality ground water in the region. An uncon- Hole, Massachusetts 02543; and M. Hodgins, across faults that impact aquifers below depths formity locally aids in differentiating between Glorieta Geoscience Inc., P.O. Box 5727, Santa of 200 ft. Upward pressure gradients and warm the less productive Miocene and more produc- Fe, New Mexico 87502 waters are frequently observed along faults. tive Plio–Pleistocene deposits. As potable water Subsurface lithologic and geophysical data from About 500 wells were plotted for major cations sources become scarce, abundant brackish-water a series of municipal, exploratory, subdivision, and anions and trace inorganics. Contoured resources may become attractive production tar- and domestic wells are used to delineate varia- maps were prepared on 19 selected constituents, gets for desalination along the structurally high- tions in thickness and extent of Tertiary through er northwestern flanks of the basin. With each including TDS, HCO3, Br, Cl, F, N, SO4, Ca, K, Quaternary sediments and Pliocene basalt flows Mg, Na, As, Ba, Cr, Pb, Si, Sr, U, and Zn. High new generation of geologic mapping, our under- and interbedded fluvial sequences in the south- standing about the geologic history and distribu- values exceeding EPA drinking standards were ern San Luis Basin near Taos, New Mexico. These mapped mainly along fault traces. Hydrochemi- tion of earth resources improves considerably. data are also utilized to help constrain the loca- cal zones are mapped across the county reflect- tion of buried faults. Two deep wells drilled in ing the geology of recharge source areas and age 2007 are used to refine previously published of ground water. SEDIMENTOLOGY AND PROVENANCE stratigraphic analyses of basin-fill deposits. The eastern part of the rift basin is gifted with OF BASIN-FILL STRATA AS A GUIDE TO Analyses of long-term pumping tests conducted perennial recharge from the mountain front FAULT EVOLUTION, SOUTHERN RIO in proximity to faults are used to evaluate the into a large clastic section that serves as a thick GRANDE RIFT, G. H. Mack, and W. R. Seager, effect of faults on ground water flow in shallow aquifer, which provides drinking water for the Department of Geological Sciences, New Mex- and deep basin-fill aquifers. Selected wells and majority of the population of Taos County. Local ico State University, Las Cruces, New Mexico surface water sources were sampled and ana- ground water problems include a slight water 88003 lyzed for major anions and cations, trace met- table drop adjacent to streams during drought The southern Rio Grande rift constitutes a broad als, 87Sr/86Sr, 3H, δd2H, and δd18O. Tritium results periods, rapid draining through fractured dacite (150 km) region of mid-late Cenozoic crustal indicate that recharge to the shallow aquifer lavas, low production rates of fine-grained and extension that is characterized by 20 fault blocks. occurs on a time scale of <5–10 yrs, but that volcanoclastic reservoirs in western Taos County, The history of individual range-boundary faults recharge to some deep alluvial wells and wells and cementation of the Picuris Formation aqui- can be deduced by using the sedimentology and completed into sediments interbedded with the fer in southern Taos County. provenance of strata deposited in complemen- Servilleta basalts occurs on a time scale of >50 tary basins. This approach is especially applica- yrs. Recharge into the mountain front fractured ble to a 100 km stretch of the southern rift from bedrock aquifers occurs on time scales ranging Truth or Consequences to Las Cruces, where from <5–10 yrs to >50 yrs. d2H and δd18O data STRUCTURAL EVOLUTION OF THE EAST- basin-fill strata ranging in age from late Oligo- suggest that some deep basin-fill aquifer wells ERN ESPAÑOLA BASIN, RIO GRANDE cene to Pleistocene are widely exposed. have received higher-elevation or older (Pleisto- RIFT, NORTH-CENTRAL NEW MEXICO, Deposition of the Hayner Ranch Formation cene?) recharge, whereas other deep wells have D. J. Koning, [email protected], New Mexico (upper Oligocene–mid Miocene) took place in received lower-elevation or modern/Holocene Bureau of Geology and Mineral Resources,

May 2008, Volume 30, Number 2 Ne w Me x i c o Ge o l o g y 53 New Mexico Institute of Mining and Technol- STRUCTURAL AND STRATIGRAPHIC we came to recognize that two lithologically dis- ogy, Socorro, New Mexico 87801; S. D. Connell, IMPLICATIONS OF OIL AND GAS DRILL- tinct, geographically restricted successions of New Mexico Bureau of Geology and Mineral ING AND SEISMIC EXPLORATION IN THE conglomerate comprise the “lower Abiquiu” and Resources, New Mexico Institute of Mining SANTA FE EMBAYMENT OF THE ESPAñO- that the provenance of these coarse sediments and Technology, Albuquerque Office, Albu- LA BASIN, NORTH-CENTRAL NEW MEX- is quite different from the provenance of strata querque, New Mexico 87106; J. Slate, U.S. Geo- ICO, B. A. Black, Black Oil Co., 206 W. 38th assigned to the “upper Abiquiu.” Maldonado logical Survey, P.O. Box 25046, Federal Center, Street, Farmington, New Mexico 87401; and and Kelley (in prep.) have suggested restricting MS 913, Lakewood, Colorado 80225; E. Wan, W. K. Dirks, Tecton Energy LLC, 3000 Wilcrest the name Abiquiu Formation to “upper Abiquiu” U.S. Geological Survey, 345 Middlefield Road, Suite 300, Houston, Texas 77042 strata and applying the name Ritito Conglomer- MS 975, Menlo Park, California 94025; J. F. Ninety-four (94) years of oil and gas exploration ate to “lower Abiquiu”conglomerate exposed Ferguson, Program in Geosciences, University has taken place in the Santa Fe embayment of the near the village of Abiquiu. Here, we propose the of Texas at Dallas, P.O. Box 30688, Richardson, Española Basin. The last 34 yrs of this explora- name Gilman Conglomerate for conglomerate Texas 75083-0688; V. J. S. Grauch, U.S. Geologi- tion has documented the contrasting effects of exposed near the village of Gilman in the south- cal Survey, Box 25046, Federal Center, MS 964, Laramide compression and later Tertiary exten- west Jemez Mountains. The basement-derived Denver, Colorado 80225; G. WoldeGabriel, Earth sional tectonics in the southern portions of the Ritito Conglomerate is exposed along the south- and Environmental Sciences Division, P.O. Box area. east flank of the Tusas Mountains, beneath the northwest Jemez Mountains as far south as the 1663, Los Alamos National Laboratory, Los As many as three separate thrust plates have northwest corner of the Valles caldera, and as far Alamos, New Mexico 87545; L. Peters, W. C. been drilled in the area. The well control com- west as San Pedro Parks in the Sierra Nacimien- McIntosh, N. Dunbar, New Mexico Bureau of bined with the available seismic lines demon- to. The volcaniclastic Gilman Conglomerate is Geology and Mineral Resources, New Mexico strates the presence of both pre-rift thrusting and present near the villages of San Ysidro, Jemez Institute of Mining and Technology, Socorro, expected later normal faulting associated with Springs, and Gilman along the Jemez fault New Mexico 87801; D. Broxton, and W. S. the opening of the Rio Grande rift. Possible flow- er structures associated with lateral movements zone. The restricted Abiquiu Formation covers a Baldridge, Earth and Environmental Sciences along the northeast extension of the Tijeras shear broad region of north-central New Mexico, with Division, P.O. Box 1663, Los Alamos National in this area are also possible. exposures as far south as the southwest Jemez Laboratory, Los Alamos, New Mexico 87545 In 1985 the first oil production from the Rio Mountains. Clasts from the Latir volcanic field We interpret the timing of basin tilting as well as Grande rift was marketed from the Santa Fe are common in the Abiquiu Formation in the deformation along specific structures in the east- embayment. It would be 26 yrs before this sub- northern Jemez Mountains but are absent in the ern Española Basin (EEB). The EEB has a half- economic discovery (at $8.00 a barrel) would southwest Jemez Mountains. Localized basalt graben geometry north of Santa Fe, with beds eventually prove to be an economic success (at flows and volcaniclastic sedimentation that are generally tilted 2–10° W toward a central fault $50+ a barrel). The re-completion of this well and temporally equivalent to late Abiquiu deposi- system (CFS). The CFS includes the northeast- the solving of the subsurface geologic story are tion elsewhere in the Jemez Mountains are pre- striking Embudo fault system and the Santa more than three and a half decades in the mak- served in the southeast Jemez Mountains on St. Clara fault (SCF) to the north, collectively acting ing. A recent 6-month moratorium declared by Peters Dome. The Pedernal chert is 1–2 m thick as a rift transfer structure, and the north-strik- the governor on oil and gas drilling in Santa Fe on Cerro Pedernal and Encino Point and occurs ing, east-down Pajarito fault (PF) to the south. County will slow, or perhaps even terminate, our in the uppermost part of the Ritito Conglom- Between the PF and SCF is a 6-km-long zone continuing ability to learn the details of the sub- erate. The chert is absent east of the Cañones consisting of several west-down faults. A series surface geology of this unique area. fault zone. Multiple layers of chert occur in the of aligned faults and folds comprise two major The commercially successful Tecton Black- restricted Abiquiu Formation on the west side north-striking structures east of the CFS. Santa Ferrill #1, and subsequent activities, has begun of the Coyote fault zone, and thin stringers of Fe Group basin fill attains a general thickness of to open a new oil and gas province in the Rio chert are present in the Abiquiu Formation in the 1–3 km in the EEB. However, basin fill thickens Grande rift. The recent exploration activities southwest Jemez Mountains. to 3–4 km in structural lows related to localized and production of high gravity oil suggests that The distribution of the conglomeratic units subsidence immediately adjacent to three faults million-barrel oil accumulations are potentially indicates the presence of two distinct sub-basins of the CFS. An recognized north of present within the downthrown areas of the rift. in the vicinity of the Jemez Mountains early in Santa Fe is bracketed between 25–30 Ma. Abundant source rock, a favorable history of Oligocene time. Later widespread volcaniclastic Stratal tilt data from relatively unfaulted areas maturity, and extensive reservoir systems are sedimentation sourced from the Latir volcanic indicate an episode of high-tilt rates between present in the rocks of the Santa Fe field covered the region, while localized volca- 16–10 Ma. Significant deformation continued embayment. Structural and stratigraphic com- nism and sedimentation occurred in the south- along the aforementioned two major structures plexities will account for a portion of the trapped east Jemez Mountains. Finally, silica-enriched east of the CFS in the late Miocene–Pliocene. oil and gas, and fractured Niobrara shale has ground waters deposited chert below the basal Earlier tilting along these structures is suggested large potential for oil and gas production over contact and within the Abiquiu Formation. by seismic reflection data and by angular rela- numerous sections in the southern part of the tions across the 25–30 Ma unconformity (at least Española Basin. locally). Pronounced subsidence occurred in the INFLUENCE OF BASEMENT STRUCTURE structural lows adjacent to the PF and SCF in the ON SHALLOW AQUIFER GEOCHEMISTRY late Miocene–Pliocene. Stratigraphy and tectonic implica- IN THE RIO GRANDE RIFT, NORTHERN We interpret the timing of vertical displace- tions of Oligocene to early Mio- NEW MEXICO—EXAMPLES FROM THE ment along the PF and SCF by comparing thick- cene sedimentation in the Jemez SANTA FE AND PEÑASCO EMBAYMENTS ness changes and vertical offsets of faulted strati- Mountains, north-central New OF THE ESPAÑOLA BASIN, P. S. Johnson, graphic intervals in the Santa Fe Group. These Mexico, S. A. Kelley, [email protected]. [email protected], New Mexico Bureau of indicate high throw rates along the SCF and com, New Mexico Bureau of Geology and Geology and Mineral Resources, New Mexico PF, and faults branching off of these structures, Mineral Resources, New Mexico Institute of Institute of Mining and Technology, Socorro, between 13–10 Ma. Approximately 430–500 m of Mining and Technology, Socorro, New Mexico New Mexico 87801; V. J. S. Grauch, U.S. Geo- stratigraphic separation of post-10 Ma Chamita 87801; K. Kempter, 2623 Via Caballero del Norte, logical Survey, Geologic Division, Denver, Formation strata and lesser vertical offset of the Santa Fe, New Mexico 87505; F. Maldonado, Colorado 80225; P. W. Bauer, D. J. Koning, and Pliocene-age Puyé Formation indicate that sig- U.S. Geological Survey, MS 980, Denver Fed- S. W. Timmons, New Mexico Bureau of Geol- nificant vertical motion along the SCF occurred eral Center, Denver, Colorado 80225; G. Smith, ogy and Mineral Resources, New Mexico Insti- after 10 Ma. Department of Earth and Planetary Sciences, tute of Mining and Technology, Socorro, New We infer that lateral motion along the SCF University of New Mexico, Albuquerque, New Mexico 87801 commenced by 9–12 Ma and peaked at 6–4 Ma Mexico 87131; S. D. Connell, and D. J. Koning, The west-tilted half graben of the eastern Españo- using the Chamita syncline, which we assume is New Mexico Bureau of Geology and Mineral la Basin is structurally and topographically high related to transpression created by the right-step Resources, New Mexico Institute of Mining along the base of the southern Sangre de Cristo between the EF and SC. Cross sections suggest and Technology, Socorro, New Mexico 87801 Mountains, where Precambrian basement lies at thickness changes across the Chamita syncline The Abiquiu Formation has traditionally been shallow depths beneath Santa Fe Group rift sedi- for post-12 Ma strata. A pronounced angular informally divided into three units: lower, Peder- ments that form the region’s primary aquifers. unconformity on the north limb indicates strong nal chert, and upper. During the course of recent At the southern end of the basin, geophysical folding at 6–4 Ma. 1:24,000 scale mapping in the Jemez Mountains, data indicate a shallow platform bounded on

54 Ne w Me x i c o Ge o l o g y May 2008, Volume 30, Number 2 its northern side by a north-down, arcuate flex- earliest PPf motion(s) continues: Precambrian vidual outcrops. Also in this zone are sparse, ure herein named the Rancho Viejo hinge zone. and ductile (e.g., Miller et al. 1963; Fankhauser meter-scale blocks of indurated Mississippian– Both the platform and the hinge zone have been and Erslev 2004; Wawrzyniec et al. 2007) versus Pennsylvanian sedimentary rocks and significant folded into a north-plunging syncline. Whereas Phanerozoic and brittle (e.g., Ancestral Rockies fine-grained cataclasite. We interpret this breccia the Santa Fe Group is 250 ft or less across much or Laramide; Karlstrom and Daniel 1993; Daniel zone as recording dilation and shear in a high- of the Santa Fe platform, the upper surface of et al. 1995; Cather et al. 2006). The focus of this strain zone adjacent to the PPf. (2) A western Oligocene-age volcanic and volcaniclastic strata, study is to characterize the deformation due to zone as much as 200 m wide has low dispersion which forms the base of the Santa Fe Group aqui- folding and determine if there is a genetic rela- of foliation orientations within individual out- fer, appears faulted and irregular, with as much tionship with the PPf. crops. This zone exhibits relatively minor fine- as 650 ft of Santa Fe Group filling local paleoval- Twenty-four quartzite samples from the south- grained cataclasite, is strongly indurated by red leys eroded on the surface. The Oligocene sur- to southwest-dipping Proterozoic Ortega and jasperoid, and locally is cut by less-brecciated face is deformed dramatically across the Rancho Rinconada Formations in the south limb of the pods of Mississippian carbonate (probable fis- Viejo hinge zone, where depth (and thickness Hondo syncline were collected along strike sure fills) and Pennsylvanian– arkosic of Ancha and Tesuque Formations) increases through the refold, up to ~2 km from the PPf. sandstone. We interpret this breccia zone to have from 500 to 2,000 ft. Northwest of Santa Fe, Thin sections were cut in horizontal planes in formed by weak dilational strain. In both brec- north-striking faults in the Barrancos structure order to document fabrics related to horizontal cia zones, the average orientation of foliation is zone uplift blocks of Oligocene volcanic rocks, shear couples or vertical-axis rotations. A quartz rotated ~20–30° counterclockwise relative to that thinning the Santa Fe Group to about 3,000 ft. microstructural analysis was done to test for a in undeformed gneiss to the west. This rotation These basement structures produce a relatively ductile strain gradient within the refold or with occurred before widespread Permian remagneti- thin Santa Fe Group aquifer in the Santa Fe distance from the PPf; quartzite samples collect- zation in the area, as no significant vertical-axis embayment and have brought Precambrian and ed by Bauer (1987), mainly from the north limb rotation has occurred since then (Wawrzyniec et Oligocene rocks upward into range of shallow of the Hondo syncline, provide ductile fabrics al. 2007). domestic and municipal water wells. Upward west of the refold for comparison. Those samples The inferred sequence of geologic events was: movement of deep, sodium- and arsenic-rich (up show mainly annealed foam texture, presumably (1) Pre-Permian (probably Proterozoic, based on to 54 µg/L) ground water into the shallow aqui- relict from 1.4 Ga heating (Bauer 1987). Minor regional deformation patterns) sinistral shear fer near Santa Fe may be facilitated by basement faults and fractures were also measured and caused counterclockwise rotation of foliation faults and flexure-related fracturing of Oligocene characterized along the same transects in order near the fault. (2) Pre-Middle Mississippian (early volcanic rocks in the Rancho Viejo hinge zone. to relate brittle deformation to the folding. Ancestral Rocky Mountains orogeny (ARM) or At the northern end of the basin, geologic Heterogeneous ductile strain in the refold older) dilation and brecciation. (3) Opening and mapping defines the Peñasco embayment as a overprints the foam texture and implies a Pro- filling of fissures during Middle Mississippian bedrock low between the Picuris Mountains to terozoic (post-1.4 Ga) age for the refold, which carbonate sedimentation and karst development. the north and the Sangre de Cristo Mountains to may predate the PPf itself. Fabrics include main- (Local post-brecciation, pre-jasperoid chlorite the south. The Dixon Member (Tesuque Forma- ly northeast-southwest elongate grains (north- cement is also present, but its age relationship tion) and Picuris Formation fill the embayment west-southeast horizontal shortening) with with the fissure fills is uncertain). (4) Late ARM to depths ranging from a few tens to several undulose extinction, sutured grain boundaries, injection of unlithified arkosic sand from the hundred feet, and form the valley’s major aqui- and subgrain development, suggesting low-T Alamitos Formation or Sangre de Cristo Forma- fers. Sets of northeast-striking faults associated deformation. The highest strain is in the refold tion into unindurated fault breccia. (5) Late ARM with the Picuris–Pecos fault system form horst hinge zone, but high-strain samples also come or Laramide deformation (sans vertical-axis rota- and graben structures in the embayment that are from both limbs ~1 km west and southeast of the tion) caused mixing of clasts of lithified upper oriented perpendicular to directions of regional hinge. The deflection of the Hondo syncline can Paleozoic strata into breccias along the PPf, fold- ground water and surface water flow. The Peñas- be explained by either east-side-up or dextral ing and faulting in Paleozoic strata east of the co horst, a major upthrown block of Precambrian shear in a north-striking zone. However, such PPf, and enhanced the permeability in breccias. crystalline rock, lies as much as 300 ft below land shear fails to explain the apparent lack of a sys- (6) A major Oligocene hydrothermal system was surface at Chamisal to as little as 30 ft below the tematic strain gradient approaching the PPf or localized by the high-permeability fault breccias, Rio Santa Barbara. Locally elevated concentra- the northwest-southeast grain-scale shortening causing jasperoid cementation (microquartz tions of naturally occurring uranium, arsenic, direction, which implies sinistral shear on the after chalcedony) and reheating (>110° C) that and fluoride are associated with the Peñasco PPf. Possibly, grain-scale fabrics were controlled reset regional Laramide apatite fission-track horst, the Picuris–Pecos fault system, and/or by specifics of the fold mechanisms (e.g., flex- cooling ages to 32–26 Ma near Deer Creek. (7) tuffaceous sediments in the Picuris Formation. ural slip) rather than the regional tectonic strain Development of numerous minor faults that cut Anomalously high TDS, chloride, chloride/bro- patterns. Preliminary field and petrographic jasperoid-cemented breccias, presumably dur- mide ratios, and silica are also measured in shal- data suggest that brittle structures are also con- ing Neogene rifting. In contrast to recently pub- low wells near horst-bounding faults. centrated in the hinge zone of the refold. These lished interpretations, geological relationships structures may be related to the brittle-ductile at Deer Creek do not require major Proterozoic Session 2—Stratigraphy, Structure, folding event, or may be much younger. dextral slip (and instead suggest some Protero- and Paleontology zoic sinistral slip), nor do they disallow major ARM or Laramide dextral slip on the PPf. Heterogeneous strain in a “Drag” GENESIS OF FAULT BRECCIA AT DEER fold adjacent to the Picuris– CREEK—IMPLICATIONS FOR THE SLIP Pecos fault in northern New Mexi- HISTORY OF THE PICURIS–PECOS FAULT, STRATIGRAPHY SOUTH OF co—Preliminary results, A. L. Luther, S. M. Cather, [email protected], A. S. Read, S. LAMY, NEW MEXICO, J. A. Spielmann and [email protected], G. J. Axen, Department A. Kelley, and D. Ulmer-Scholle, New Mexico S. G. Lucas, New Mexico Museum of Natural of Earth and Environmental Science, New Bureau of Geology and Mineral Resources, History and Science, 1801 Mountain Road NW, Mexico Institute of Mining and Technology, New Mexico Institute of Mining and Technol- Albuquerque, New Mexico 87104 Socorro, New Mexico 87801; and S. M. Cather, ogy, Socorro, New Mexico 87801 The Triassic stratigraphy around Lamy, Santa Fe New Mexico Bureau of Geology and Mineral Spectacular fault breccia as much as 250 m wide County, New Mexico, has been relatively under- Resources, New Mexico Institute of Mining is exposed at Deer Creek along the Picuris–Pecos studied compared to contemporaneous sections and Technology, Socorro, New Mexico 87801 fault (PPf), ~18 km southeast of Santa Fe. There, in north-central (Rio Arriba County) and east- In the Picuris Mountains of northern New Mex- the PPf juxtaposes Middle Pennsylvanian– central New Mexico (Quay County). A compos- ico, the east-trending, Proterozoic north-vergent Permian strata (Alamitos Formation and Sangre ite section is ~507 m thick and consists of Perm- Hondo syncline is refolded adjacent the Picuris– de Cristo Formation) with Proterozoic granite- ian (Artesia Group), Middle Triassic (Moenkopi Pecos fault (PPf) by a southwest-plunging syn- gneiss on the west. In addition to the ~38 km Group), and Upper Triassic strata (Santa Rosa, form that is <1.5 km wide east-west and ~8 km dextral separation documented elsewhere along Garita Creek, Trujillo, Petrified Forest, and Rock long north-south. The relationship between the the fault, the PPf at Deer Creek shows strati- Point Formations). The Artesia Group (18–25 m) PPf and the refold has not been studied system- graphic evidence for ~300 m of east-down sepa- overlies limestones of the San Andres Formation atically. Miller et al. (1963) interpreted the refold ration. The breccia consists of two zones: (1) An and consists of interbedded sandy mudstones as a ductile dextral drag fold along the PPf, but eastern zone, 10–50 m wide, directly west of the and crossbedded sandstones with rare gypsifer- it also may be due to PPf propagation or be an PPf, within which clasts of Proterozoic gneiss ous beds. A thick (~6 m), crossbedded sandstone older, unrelated structure. Controversy over exhibit diverse foliation orientations within indi- marks the onset of Moenkopi Group deposition.

May 2008, Volume 30, Number 2 Ne w Me x i c o Ge o l o g y 55 Overall, the Moenkopi Group is 27–30 m thick. ics dictates that they must greatly outnumber dated ash bed is slightly above the boundary Crossbedded sandstones predominate in the adults. Where were the juveniles? between these two land-mammal zones, it is Moenkopi Group strata, with lesser lithologies, Analysis of the Rotten Hill population showed estimated that the Puercan–Torrejonian bound- including cherty sandstones and mudstones. The that the diameter of Buettneria’s limb bones grew ary has an age of about 64.6 Ma thus making the Santa Rosa Formation unconformably overlies in strong negative allometry; e.g., the allometric duration of the Puercan land-mammal age 0.9 the Moenkopi Group and all three of its mem- constant for femur length versus midshaft diam- m.y. in the San Juan Basin. bers (ascending order), Tecolotito, Los Esteros, eter = 0.78, where a constant of 1.5 is required and Tres Lagunas, are present. The Tecolotito to maintain constant stress on the limb bones Member (12 m thick) consists of crossbedded throughout growth. Thus, weight-bearing capac- Exhumation History of the San sandstones, some with chert, and sandy mud- ity of the limbs decreased drastically throughout Juan Basin, S. Braschayko, sbrasch@nmt. stone. The Los Esteros Member (54 m thick) adulthood. edu, Department of Earth and Environmental has a lower third that is mudstone-dominated, We propose that in addition to taphonomic Science, New Mexico Institute of Mining and a medial third that has crossbedded sandstones influences against preservation of the juveniles, Technology, Socorro, New Mexico 87801; S. A. and sandy mudstones, and an upper third that is their absence may be due to an ecological sepa- Kelley, New Mexico Bureau of Geology and also mudstone-dominated. Crossbedded sand- ration from the adults. Separation of adults and Mineral Resources, New Mexico Institute of stones are the dominant lithology of the Tres juveniles is known in some extant amphibians Mining and Technology, Socorro, New Mexico Lagunas Member (14 m thick). The mudstone- and probably serves to reduce competition for 87801; and D. Stockli, The University of Kansas, dominated Garita Creek Formation overlies the food and conspecific predation of the juveniles. Lawrence, Kansas 66045 Tres Lagunas Member. This unit is at least 94 The increasingly weaker limb bones of the adults Low temperature thermochronology and sonic m thick, though regional topography made it could have enforced such an ecological separa- log data are combined to assess the post-Oligo- impossible to find a single section of the entire tion by making adults water-bound while the cene unroofing history of the San Juan Basin. unit. The Trujillo Formation (26 m thick) is sand- juveniles could have been more terrestrial or lit- Preliminary apatite (U-Th)/He data indicate that stone dominated with some mudstones. The Pet- toral. If so, this may explain the extreme preser- rocks as shallow as 385 m were at temperatures rified Forest Formation (196 m thick) is almost vational preference for adults; burial and fossil- above 70ºC until about 4–5 Ma and have since entirely composed of mudstone, the exception ization being much more likely in their aquatic cooled. Apatite fission track (AFT) data suggest being the cherty, crossbedded sandstone Correo habitat. higher temperatures to the north with cooling bed that occurs in the upper third of the forma- below 110ºC occurring in the late Miocene. The tion. The Rock Point Formation (56 m thick) San Juan Basin cooled from T>110ºC due to ero- is present as a series of sandy mudstones with A 40AR/39AR single-crystal sanidine sional exhumation from <15 Ma. AFT ages in the occasional sandstone beds. The Lamy collecting AGE FOR AN ALTERED VOLCANIC ASH San Juan Basin decrease toward the north. area yields the type assemblage of the Lamyan BED FROM THE PALEOCENE nACIMIEN- Interval transit time, which is the reciprocal sub-land vertebrate faunachron, including the TO FORMATION IN THE SOUTHERN SAN of sonic velocity, can be measured from sonic famous Late Triassic Lamy amphibian quarry JUAN bASIN SHEDS NEW LIGHT ON geophysical well logs and used to estimate rela- that has produced dozens of individuals of the THIS FORMATION’S STRATIGRAPHIC tive amounts of exhumation across an area. This metoposaurid amphibian Buettneria perfecta. AND BIOCHRONOLOGIC ESSENCE, J. E. technique is very useful due to the ubiquity of Fassett, [email protected], U.S. Geological sonic logs and the relative efficiency with which Survey, Emeritus, 552 Los Nidos Drive, Santa the data can be processed. This method can be PRELIMINARY ANALYSIS OF GROWTH Fe, New Mexico 87501; M. T. Heizler, and W. C. used as a cross-check of erosion estimates deter- AND AGE STRUCTURE OF BUETTNE- McIntosh, New Mexico Bureau of Geology and mined from low temperature thermochronology RIA (AMPHIBIA: METOPOSAURIDAE) Mineral Resources, New Mexico Institute of data and can be used to evaluate exhumation ASSEMBLAGES FROM THE UPPER TRI- Mining and Technology, Socorro, New Mexico versus heat flow variations across a basin. Inter- ASSIC OF WEST TEXAS AND NEW MEX- 87801 val transit time decreases exponentially with ICO, L. F. Rinehart, [email protected], The first 40Ar/39Ar single-crystal age for Paleo- increasing burial depth according to a compac- S. G. Lucas, New Mexico Museum of Natural cene strata in the San Juan Basin was obtained tion curve calibrated for each rock unit exam- History and Science, 1801 Mountain Road from sanidine crystals recovered from an altered ined. Because rock compaction is an irreversible Northwest, Albuquerque, New Mexico 87104, volcanic ash bed in the Nacimiento Formation process, rock units that are at a depth shallower A. B. Heckert, Department of Geology, ASU Box at Mesa de Cuba in the southeast part of the than their maximum burial depth will have a 32067, Appalachian State University, Boone, basin. This age is 64.49 ± 0.38 Ma (2 sigma) and lower-than-expected interval travel time rela- North Carolina 28608; and A. P. Hunt, New is based on single-crystal sanidine results rela- tive to the calibrated compaction curve. The cali- Mexico Museum of Natural History and Sci- tive to Fish Canyon Sanidine at 28.28 Ma and a brated compaction curve for the Mancos Shale ence, 1801 Mountain Road NW, Albuquerque, total 40K decay constant of 5.53E-10/a. Due to in the San Juan Basin was determined from over New Mexico 87104 significant contamination by older K-feldspar 100 well logs. The average interval transit time for Mancos Shale at depths shallower than 915 Two mass death assemblages of the Upper Tri- crystals, this date is considered a maximum depositional age. The dated ash bed is 119 m m ranges from about 75 to 110 μs/ft and shows assic temnospondyl amphibian Buettneria per- a pronounced exponential decrease in interval fecta Case, the “Lamy bonebed” from the Garita above the Cretaceous–Tertiary interface and is 76 m above the base of the Nacimiento/top of the travel time with depth. The maximum amount of Creek Formation in central New Mexico and relative exhumation recorded by the shale sonic “Rotten Hill” from the Tecovas Formation of Ojo Alamo Sandstone. This age places the dated ash bed near the top of magnetochron C29n. The log data is 1.2 km in the San Juan River valley; west Texas, yield tens to hundreds of individu- lower part of chron C29n was identified within however, the typical amount of relative exhuma- als. We used a statistical approach to resolve size the underlying Ojo Alamo Sandstone at Mesa tion in the San Juan Basin is less than 1 km. classes (= age groups) in clavicles and interclav- Portales, about 12 km south of Mesa de Cuba; icles from which we generated a growth curve the base of this chron is 98 m below the dated ash and age distribution for Buettneria. Comparison bed. This age determination allowed a calcula- LINKS BETWEEN THIRD-ORDER (m.y.- of these data to extant salamander outgroups tion of the rate of sedimentation for underlying SCALE) SEA-LEVEL AND CLIMATE (e.g., Andrias, Cryptobranchus, Chioglossa, others) Paleocene strata of 173 m/m.y (not corrected for CHANGE IN THE UPPER and other amphibians showed that growth was compaction). Extrapolating this rate of deposi- MONTOYA GROUP, SOUTHERN NEW indeterminate and that only sexually mature tion to overlying Nacimiento Formation strata to MEXICO, M. A. Tyra, M. Elrick, and V. Atudorei, (marked by size, slow linear growth, and age the base of the Eocene San Jose Formation places Department of Earth and Planetary Sciences, distribution shape) adults were present in the this contact at 63.40 Ma. Because the Paleocene– University of New Mexico, Albuquerque, New fossil assemblages. They lived, on average, 10 Eocene contact is 55.8 Ma, an enormous uncon- Mexico 87131 or 11 yrs past sexual maturity. Linear size (mea- formity of about 7.6 m.y. must be present at The Upper Ordovician Montoya Group (south- sured by skull and femur length) increased by the Paleocene–Eocene contact at Mesa de Cuba ern New Mexico, west Texas) was deposited a factor of ~1.9 between sexual maturity and (assuming there are no significant, intervening on a southward-dipping ramp and contains up death, similar to the outgroups. Juvenile Buett- present in Nacimiento strata to six 3rd-order stratigraphic sequences. These neria are recognizable at very small sizes else- overlying the dated ash bed). Puercan and (or) sequences have been correlated by Pope (2004) where in the Chinle Group, but are not present Torrejonian mammal fossils have been found and Harris et al. (2004) to similar sequences in these assemblages and are very rare in the at numerous localities in the southern San Juan across North America and Estonia. These cor- fossil record even though population dynam- Basin, including at Mesa de Cuba. Because this relations suggest eustatic sea-level change as

56 Ne w Me x i c o Ge o l o g y May 2008, Volume 30, Number 2 the driver; their root cause (tectonic or climatic), Ranch. In both areas unsupervised classifications Two exploratory wells were drilled in the Rio however, remains an open question. We are test- have been performed to analyze any correlations Puerco valley west of Rio Rancho during the ing the hypothesis that the rock magnetic signal with soil unit. More detailed field data have been summer of 2007 by Sandoval County and a resi- covaries with 3rd-order sea-level change in the collected at the Sevilleta, further quantifying the dential developer. Exp-6 spudded in thin alluvial Late Ordovician. visual correlations. cover just east of the surface trace of the Moqui- We measured the lower two sequences (30–70 no fault and ended 3,850 ft below ground surface m) of the Montoya Group in the Cookes Range, Session 3—Rio Grande Rift, (bgs). It was screened between 3,598 and 3,809 ft near Deming, New Mexico, which are composed bgs in the Aqua Zarca Member of the Chinle For- of deep-to-shallow ramp carbonates (Pope Albuquerque and Southern Basins mation and in the San Andres and Glorieta For- 2004). We are comparing sea-level-driven facies STRUCTURAL AND STRATIGRAPHIC mations, respectively. Exp-5 (total depth of 6,450 changes to rock magnetic values (magnetic sus- IMPLICATIONS OF OIL AND GAS DRILL- ft bgs, reaching Precambrian basement rock at ceptibility and anhysteretic remnant magneti- ING AND SEISMIC EXPLORATION DATA 6,350 ft) was screened in six intervals between zation) to evaluate the links between m.y.-scale IN THE ALBUQUERQUE BASIN OF THE 3,360 and 4,820 ft bgs from the Aqua Zarca to changes in sea level and climate. Rock magnetics RIO GRANDE RIFT, CENTRAL NEW MEX- the Yeso Formation. Exp-6 yielded approxi- can be used as a climate proxy for investigating mately 600 gallons per minute (gpm) of water. ICO, B. A. Black, Black Oil Co., 206 W. 38th changes in wind intensity/aridity, and/or flu- Exp-5 initially produced approximately 20 gpm Street, Farmington, New Mexico 87401; and vial sediment influx. Preliminary results show of artesian flow. After a commercial fracturing W. K. Dirks, Tecton Energy LLC, 3000 Wilcrest, that rock magnetics (2–5 m sampling resolution) procedure, Exp-5 flowed at a sustained rate of Suite 300, Houston, Texas 77042 in the lower sequence and interpreted sea level approximately 150 gpm. Ground water from the covary. Here decreasing magnetic values coin- One north-south seismic line parallel to the long wells contains approximately 12,000 mg/l TDS, cide with transgression (and vice versa) suggest- axis of the Albuquerque Basin and east-west 3,100 mg/l chloride, and 4,400 mg/l sulfate. ing either wind-intensity/aridity decreased dur- lines across all or parts of the basin (in conjunc- Drilling Exp-6 through the Moquino fault made ing sea-level rise and/or the influx of fluvially tion with the well control from the deeper explo- for difficult stratigraphic correlation until reach- derived material to the deep ramp decreased. ration tests that have penetrated the Cretaceous ing the Todilto gypsum beds at approximately Rock magnetics from the younger sequence rocks) shed significant light on the structural 1,685 ft bgs. After drilling Exp-5, units correlated show a more complex relationship with sea- style and the timing history of the opening of the between the two holes up to 1,415 ft bgs in Exp-6. level change, which we are presently investi- Rio Grande rift in this part of New Mexico. Using that depth for the intersection of the fault gating. To better understand Late Ordovician This exploration data also show dramatic and with the well and an estimated surface trace of climate change, we also are extracting conodont possibly unexpected structural partitions and the fault 230 ft west of the well indicates the fault apatite from the sequences to examine their sub-basins as well as hidden faults and horst dips approximately 81° east. oxygen isotopic composition (a climatic proxy and graben structural geometries in the larger The Moquino fault juxtaposes the marine for both temperature and ice volume). These rift structure. Of structural importance is the rec- shales of the Mancos Shale and the deltaic, isotopic values will further constrain the links ognition of Laramide thrusts and their location coal-bearing sandstones of the Menefee Forma- between m.y.-scale sea-level and climate change. and effect on pre-rift structures in the basin. tion. Vertical displacement may be as much as Insight into the timing and abruptness of syn- 2,285–2,785 ft based on published unit thickness- rift basin fill is dramatically seen on the seismic. es. The displacement on the Moquino fault is an DIGITAL SOIL MAPPING—EVALUATING Also strikingly illustrated is the changing tecton- example of how geologic structure can impact THE USE OF REMOTELY SENSED DATA, ic style of bounding faults on the western side of the economics of resource development. On the E. M. Engle, J. M. H. Hendrickx, and J. B. J. Har- west side of the fault, the top of the producing rison, Department of Earth and Environmental the rift margin from south to north. interval is 3,598 ft bgs. On the east side of the Science, New Mexico Institute of Mining and Of interest is the apparent effect of the pos- fault, the top of the producing zone could be as Technology, Socorro, New Mexico 87801 sible continuation of the Tijeras shear into and across the basin between the Belen sub-basin to deep as 6,383 ft bgs, nearly doubling the cost to The creation of accurate small scale soil maps the south and the Calabacillas sub-basin to the drill for that zone. is often very difficult due to time and cost con- north. This zone of disturbance (Tijeras accom- straints. The traditional methods of soil mapping modation zone) may help put constraints on the include using several sets of proxy data to iden- amount of lateral movement that has taken place Aquifer Characteristics of the tify boundaries. Aerial photographs are often in the rift—through time in this part of the rift. Santa Fe Group in Northern Rio the most useful due to the amount of detail they An additional accommodation zone may be pres- Rancho, J. Riesterer, P. Drakos, J. Lazarus, often show, from clusters of trees to outcrops of ent in the basin as a possible southwest extension Glorieta Geoscience Inc, P.O. Box 5727, Santa rock. With these data, a soil scientist can infer of the Placitas fault. Fe, New Mexico 87502; and J. Hawley, Hawley more detail about soil changes based on the land USGS Bulletin 2184, published in 2001, sup- Geomatters, P.O. Box 4370, Albuquerque, New cover. It is possible for an experienced soil scien- ports the theory that the Albuquerque Basin Mexico 87196 tist to be able to associate certain landforms with may contain a large basin-centered gas deposit in sets of internal soil properties. Using these aids, Subsurface data (lithologic and geophysical logs) the rift. Recent activities by Tecton Energy, LLC, among others, it is possible to get a preliminary collected from three deep municipal supply wells working with Black Oil suggest a multi-TCF gas idea of where boundaries will occur. This allows and one exploratory well are used in conjunction and hundred-million-barrel oil accumulations the researcher to have a plan, before going in the with data from long-term (7-day) pumping tests, may exist within the deeper downthrown areas field, of where he needs to spend the most time. remote sensing data (aeromagnetic surveys), of the rift. Most time in the field will be spent crossing back geologic mapping, and geochemistry data to and forth across these boundaries to confirm or Sub-basins in the Albuquerque Basin have determine variations in subsurface stratigraphy, change them as necessary. abundant source rock, a favorable history of chemistry, and aquifer characteristics in a portion Digital soil mapping is the computer-based maturity, and probable extensive reservoir sys- of the Albuquerque Basin. City of Rio Rancho operationalization of ideas for predicting soil tems. Structural complexities, including Lar- wells 10A, 22, and 23 are completed to depths of distribution and has become more feasible amide thrusting, as well as stratigraphic varia- between 2,000 and 3,000 ft in the Santa Fe Group with the advance of computational technology. tion will account for a portion of any trapped oil aquifer. Lithologic and geophysical logs from Remote sensing techniques can provide data that and gas. Post-Oligocene subsidence has allowed the wells indicate the presence of aerially exten- are spatially contiguous and spectrally contigu- coeval maturation of the Cretaceous source and sive subsurface units that can be correlated over ous, and it has been used successfully in the past a dramatic reduction in permeability of Tertia- distances of at least several miles in deep wells. to carry out land use and land cover surveys. It ry and Cretaceous sandstones. This may have A 3,000 ft deep exploratory boring (completed provides a quicker and more efficient method of effectively created a barrier for rapidly expelling as a 2,880 ft deep cased test well) at the well 23 mapping soils. hydrocarbons in separate sub-basins. site was zone sampled for water quality. Signifi- Using data from the Landsat 7 processed cant variations in water quality are recognized through the SEBAL model, visual correlations in samples collected below 2,000 ft vs. samples are seen between parameters such as albedo, STRUCTURAL AND STRATIGRAPHIC collected at 2,000 ft or less in the test well. Spin- surface temperature, normalized difference CONTROLS OF DEEP BRACKISH WATER ner logs conducted in the test well indicate sig- vegetation index, evapotranspiration and soil EXPLORATION, RIO PUERCO BASIN, nificant upward vertical ground water gradient moisture, and soil unit. Visual analysis has been NEW MEXICO, R. M. Sengebush, rsengebush@ in the aquifer. Clays encountered from 2,100 ft completed at two very different field sites, the intera.com, INTERA, Inc., 6000 Uptown NE, to 2,460 ft in well 23 act as significant confining Sevilleta National Wildlife Refuge and the Hilton Albuquerque, New Mexico 87110 beds. The upper portion of these clays are cor-

May 2008, Volume 30, Number 2 Ne w Me x i c o Ge o l o g y 57 relative to clays encountered in the bottom of by both subsidence and uplift at the northeast can be sustained by aquifer storage for 200–300 wells 10A and 22, which are also interpreted as edge of the Socorro Magma Body, or 4) long- yrs at the project locations. The total projected confining beds for the deeper Santa Fe Group term uplift is matched by episodic subsidence water use in the area is close to 500 AFY (acre- sediments. Water quality degrades rapidly (TDS of the surface. Within the Socorro Basin above feet per year) or about 20% of published regional > 4,500 mg/L) below the confining beds in the the Socorro Magma Body, however, ample evi- recharge estimates to the Rio Grande valley in well 23 test well, and composite borehole chem- dence of fault-bounded uplift, subsidence, and this area, suggesting that the local water supply istry in well 22 and well 10A indicate a similar extensive valley-border erosion contrasts with could be sustained indefinitely. increase in TDS below the clay beds. Although the reaches to the north and south within the pumping test and chemistry data indicate that rift. These observations affect not only interpre- faults identified in the area from surface map- tations of the duration of uplift, but also hypoth- CONDUCTIVE HEAT FLUX OVER SELECT- ping and/or aeromagnetic surveys act as barri- eses of a possible smaller shallow magma body ED GEOTHERMAL SYSTEMS IN THE RIO ers to ground water flow, stratigraphy and the and geologically reasonable rates of magma GRANDE RIFT AND ADJACENT AREAS presence of a regional confining bed are more injection into the Socorro Magma Body. SUGGESTS A PROCESS OF SHALLOW significant controls on water quality in the deep HYDROTHERMAL SYSTEM SIZE SCAL- aquifer system. ING, J. C. Witcher, [email protected], GEOHYDROLOGIC INVESTIGATION OF Witcher and Associates, P.O. Box 3142, Las THE SOUTHERN CHUPADERA MOUN- Cruces, New Mexico 88003 PROGRESS REPORT ON TRACKING RIO TAINS AREA—AVAILABILITY AND SUS- Geothermal reservoirs in a rift setting can be GRANDE TERRACES ACROSS THE UPLIFT TAINABILITY OF WATER SUPPLIES FOR static or dynamic. Static geothermal systems rep- OF THE SOCORRO MAGMA BODY, D. DOMESTIC USE, M. J. Darr, mjdarr@nmia. resent deep-seated and confined reservoirs with W. Love, [email protected], D. J. McCraw, com, MJDarrconsult, Inc., 6729 Green Valley temperatures that correspond to the temperature R. M. Chamberlin, S. D. Connell, S. M. Cather, Place NW, Albuquerque, New Mexico 87107 gradients associated with background upper New Mexico Bureau of Geology and Mineral The geology and hydrology of the southern Chu- crust heat flow. On the other hand, dynamic res- Resources, New Mexico Institute of Mining padera Mountains and the basin immediately ervoirs or systems have active upflow and asso- and Technology, Socorro, New Mexico 87801; west were investigated as part of a water avail- ciated outflow plumes that convectively and/ and L. Majkowski-Taylor, Department of Earth ability assessment for subdivision water supply. or advectively transfer deep-seated heat closer and Environmental Science, New Mexico Insti- The study area includes the bajada on the south- to the surface. The upflows and outflow plumes tute of Mining and Technology, Socorro, New east margin of the Magdalena Mountains and represent the flow paths and shallow storage or Mexico 87801 the south side of the Chupaderas above the Rio reservoirs for geothermal fluids. Because of the Historically, the ground surface above the sill- Grande valley floor near San Marcial in Socorro arid nature of Rio Grande rift region, many, if not like Socorro Magma Body has been rising on the County, New Mexico. most, geothermal systems are “blind” to surface order of 2–4 mm per yr, whereas subsidence has More than 21,000 acres (33 sections) were eval- hydrology and lack hot springs. This presents an occurred beyond its margins. For the past 25 yrs, uated for over 800 twenty-plus-acre homesites in opportunity to estimate total system thermal out- oft-cited articles have reported that terraces along three phases. After three initial exploratory bore- put by summation of conductive heat flow above the Rio Grande are deformed by uplift, but the holes were advanced, eight wells were drilled the water table across the area of the upflow and original articles did not include detailed descrip- and tested in alluvium and Santa Fe Group outflow plume for a particular system. Six to eight tions of the terrace deposits. Ongoing geologic materials in the bajada, and seven wells in the geothermal systems in the southern Rio Grande mapping of 7.5-min quadrangles along the Rio tuffs and volcanoclastic materials of the southern rift region are of sufficient exploration maturity Grande from Veguita to San Antonio across the Chupaderas. A number of existing wells were to assess natural conductive thermal output, southern Albuquerque Basin, the Socorro Magma also pump-tested and sampled. Test data were estimate reservoir volume, and assess probable Body, and the relatively narrow Socorro Basin integrated with geologic maps, satellite imagery, base or highest reservoir temperatures. There is shows three early to middle Pleistocene terrace and literature research to develop a comprehen- an apparent inverse size scaling of thermal out- deposits, local late Pleistocene terrace depos- sive picture of the area’s hydrogeology. Areas put in relation to base reservoir temperature. The its, and top(s) of early Pleistocene fluvial basin unsuitable for subdividing into lots based on largest thermal outputs correspond to very large fill. Lessons learned while tracing these discon- hydrologic factors were excluded from the final reservoir volumes and low temperature (<100o tinuous deposits southward include: 1) Original layout plans and totaled several thousand acres. C). On the other hand, systems with moderate- maximum fluvial aggradational elevations may Results show a surprising subsurface complex- to-high temperature (>100o C) are associated be preserved only locally, especially compared to ity beneath the veneer of alluvium covering the with much smaller total heat flux and apparent the southern Albuquerque Basin and the north- bajada. The basement configuration consists of en reservoir volumes. Hydrogeology appears to ern Palomas–Jornada Basin; 2) Commonly some echelon fault blocks, overlain by Santa Fe Group play an important role. The largest systems may lesser elevation of fluvial deposits is preserved sedimentary materials interbedded with tuffs and have more broadly distributed zones of upflow by interfingering with less erodible coarse- rhyolites. Transmissivity of the basin-fill materi- with large outflow plumes at shallow and inter- grained valley-border fans; 3) Coarse sediments als averages about 650 ft2/day (square feet per mediate depths (<1 km) in Paleozoic carbonate from the Rio Salado have affected the course of day) for domestic wells that tap the aquifer. Wells reservoirs. The smaller systems are intensely the Rio Grande and partially buried Rio Grande completed in interbedded volcanics have simi- focused by a variety of bedrock structures that terrace deposits over several square kilometers; lar transmissivity values, averaging 570 ft2/day. feed shallow outflow plumes of less extent in 4) If the historic Socorro Magma Body uplift Expected yields are 5–10 gpm (gallons per min- mostly Cenozoic basin-fill deposits. rate were constant, a 100,000-yr-old terrace tread ute), and water quality is generally excellent. should be about 200–400 m higher, and older The hydrology of the Chupadera Mountains, treads should have undergone even more uplift; by contrast, is dominated by the distribution of THE RIO GRANDE RIFT IN MEXICAN PER- 5) Short-term elastic uplift is generally viewed as fractured volcanic materials (the La Jencia and SPECTIVE, W. E. Elston, [email protected], domelike, but longer-term uplift could cause suf- Lemitar Tuffs) lying atop relatively imperme- Department of Earth and Planetary Sciences, ficient stretching to trigger longitudinal collapse able volcaniclastic materials (clay-rich Spears University of New Mexico, Albuquerque, New of keystone grabens, so terrace heights might not Group). Transmissivity in the main aquifer zone Mexico 87131 be affected or terraces might subside in places; averages about 17,250 ft2/day, indicating much Seen from the south, the Rio Grande rift appears and 6) Multiple north-trending rift-related faults higher production (greater than 50 gpm). Out- as an arm of the Mexican Basin and Range in the Socorro Basin south of San Acacia signifi- side of the main aquifer zone, transmissivity province. In central Mexico, a Laramide fold- cantly affect the elevations of Bandelier ashes drops to less than 10 ft2/day and well yields are and-thrust belt was inundated by mid-Tertiary preserved in axial fluvial deposits (by as much marginal. Water quality is excellent in the main volcanism, culminating in the great ignimbrite as 20 m), making estimates of maximum aggra- aquifer zone, with no dissolved arsenic problems flareup. As associated heat flow subsided, and dation or stream gradients uncertain. encountered. ductile extension gave way to brittle extension, Investigations to date show no major uplift Aquifer test results were used in site-specific basin and range fault blocks developed in the of Rio Grande terrace treads from the southern Theis calculations and/or MODFLOW ground eastern part of the province. Its western part, the Albuquerque Basin across the northern part of water flow models to predict the future draw- Sierra Madre Occidental, remained a relatively Socorro Magma Body uplift, implying either that down effects of withdrawals for water supply. undisturbed volcanic plateau. In the southwest 1) current uplift may be too recent to be recorded The results indicate that drawdowns are minimal corner of New Mexico, the central Mexican in the terrace succession, or 2) current uplift is due to low lot density and good aquifer transmis- province split: As the main fold-and-thrust belt at a maximum rate, or 3) this reach is affected sivity. Calculations show that projected water use bent northwest and continued into Arizona, it

58 Ne w Me x i c o Ge o l o g y May 2008, Volume 30, Number 2 cut across the Sierra Madre Occidental, leaving tonic activity. Areas of ground water discharge constant over recent times. The total dissolved the Mogollon–Datil volcanic field as a northern related to dissolution of Lower Permian strata solids (TDS) concentrations (ROE @ 180oC) for outlier. A lesser branch headed north, as the Rio were recognized based on alignments of gyp- 14 samples collected from 1962 to 2007 varied Grande rift system. sum-rich domes, visible on aerial photographs from 4,760 to 5,200 milligrams per liter. The TDS North of Hatch, the Rio Grande valley marks taken in October of 2007, with regional faults. concentrations at the lower end of the salt marsh the major fracture zone separating the extend- The δ34S values of sediments from the northern can be about twice that of the point of discharge ing western third of the continent from its more part of the basin are dominated by sulfate (10.6 due to evapotranspiration from vegetation and stable interior. The degree to which a distinct to 12.4 ‰) originating from the dissolution of the evaporation from the water surface. rift developed depended on the absence of crust middle Permian strata. However, three episodes “softened” by residual heat from mid-Tertiary of negative excursion of δ34S values (up to 2.2 ‰) volcanism. In the absence of volcanism, a distinct suggest episodes of water influx with lower δ34S The Biogenenicity of Desert Varnish topographic and structural rift border developed values that may be linked to the leaching of sul- and Cave Ferromanganese Depos- on the east side of the Palomas Basin, along the fate during near-surface weathering of sulfides. its, A. E. Dichosa, Department of Biology, Caballo–Fra Cristobal front. The “soft” west Values of δ34S significantly higher (median University of New Mexico, Albuquerque, New sides splintered into grabens around the Mog- 17.4 ‰) than those for sulfates derived from Mexico 87131; M. N. Spilde, Institute of Meteor- ollon Plateau pluton, core of the Mogollon–Datil fluids that interacted with Lower Permian strata itics, University of New Mexico, Albuquerque, field. Along the San Augustin Plains, this graben are found in sulfate-rich lake sediments from the New Mexico 87131; and D. E. Northup, Depart- system merged with the Socorro accommodation Estancia Basin. This suggests the involvement ment of Biology, University of New Mexico, zone, which translated the Rio Grande rift 50 km of bacterial sulfate reduction processes. Higher Albuquerque, New Mexico 87131 northeast and remained a site of minor siliceous organic carbon content in sediments from the The beautiful colors that paint the desert rocks volcanism into the Neogene. The east border of Estancia Basin (median 0.46 %) compared to the and the karst cave walls are primarily due to the the Albuquerque–Belen Basin remained rifted White Sands area (median 0.07 %) is consistent oxidation of iron (Fe2+) and manganese (Mn2+). along the Manzano–Sandia front. On the “soft” with higher rates of bacterial sulfate reduction On the terrestrial arid landscape, where weath- west side, intra-rift basaltic volcanism was active and the consequent overprinting of sulfur iso- ering and sunlight persist, these oxide layers into the Pleistocene. The Jemez volcano-tectonic tope signatures that would elucidate Holocene are called desert varnish. In the subsurface cave lineament again translated the rift 50 km north- fluid flow paths. east; its volcanism climaxed in the Pleistocene environment, where weathering and sunlight Valles caldera. The Española Basin has distinct are limited or nonexistent, they are called ferro- rift borders on both east (Sangre de Cristo) and MALPAIS SPRING AND MALPAIS SALT manganese deposits (FMD). Though this oxida- west (Chusas) sides. Thick intra-rift basalts MARSH, NORTHERN TULAROSA BASIN, tion process can be attributed to abiotic factors, resemble a failed ocean ridge. A monocline on NEW MEXICO, R. G. Myers, U.S. Army, recent evidence suggests that microbial influenc- the “soft” west side of the San Luis Basin borders IMWE-WSM-PW-E-ES, White Sands Missile es contribute to these formations for purposes the mid-Tertiary San Juan volcanic field; the San- Range, New Mexico 88002; B. D. Allen, and D. of protection and energy production. However, gre de Cristo block continues on the east side. In W. Love, New Mexico Bureau of Geology and the exact mechanisms by which they perform the Arkansas Valley the rift narrows into a fault Mineral Resources, New Mexico Institute of this simple activity are not completely under- zone buttressed on both sides by Rocky Moun- Mining and Technology Socorro, New Mexico stood. This research hypothesizes that microbes tain fault blocks. 87801 mediate Fe2+ and Mn2+ oxidation, thereby con- The Malpais Spring and Malpais Salt Marsh are tributing to and influencing the delicate ecosys- tems of both extreme environments. To test this Session 4—Hydrogeology and Climate located at the end of the distal section or south- western edge of the Carrizozo (or Malpais) oliv- hypothesis, we pose the following questions: 1) SULFUR ISOTOPE SIGNATURES IN GYPSIF- ine-basalt lava flow in the northern Tularosa Basin Who are the microbes that comprise the desert EROUS SEDIMENTS OF THE TULAROSA within White Sands Missile Range, New Mexico. varnish and cave FMD?; 2) Are there common AND ESTANCIA BASINS AS INDICATORS The Carrizozo lava flow was originally believed and/or novel microbial species present?; 3) Are 2+ 2+ OF SULFATE SOURCES AND THE LOCAL to be about 1,200 yrs old based on visual observa- there any Fe and Mn oxidizers?; and 4) How HOLOCENE HYDROLOGIC CYCLE, A. tions. Work by Saylards (1991) and Dunbar (1999) are the necessary substrates acquired from their Szynkiewicz, [email protected], L. M. Pratt, determined that the flow was actually about 5,000 environments? Department of Geological Sciences, Indiana yrs old. The Malpais Spring and Malpais Salt This investigation begins with samples asepti- University, 1001 E 10th Street, Bloomington, Marsh are one of two endemic localities of the cally collected from Socorro, New Mexico, and Indiana 47405; M. Glamoclija, Geophysical Lab- White Sands pupfish (Cyprinodon tularosa). from Spider Cave in Carlsbad, New Mexico. oratory, Carnegie Institution of Washington, Most of the ground water discharge from the DNA was extracted for the amplification of rep- 5251 Broad Branch Road NW, Washington, DC Malpais Spring area occurs as several springs resentative 16S rRNA genes (~569 bp) via the 20015; C. H. Moore, E. Singer, Department of and seeps. The aquifer for Malpais Spring con- polymerase chain reaction. Denaturing gradient Geological Sciences, Indiana University, 1001 sists of the regional Quaternary/Tertiary alluvial gel electrophoresis (DGGE) assays were run to E 10th Street, Bloomington, Indiana 47405; and bolson fill and the buried stream-channel sedi- identify the relative number of microbial species D. Bustos, White Sands National Monument, ments underneath the basalt flow. Enough flow from each community. Banding patterns suggest P.O. Box 1086, Holloman Air Force Base, New occurs in one area to form a stream channel that common microbial members and that dominant species are also present. Selected bands were Mexico 88330 flows to a wetland or salt marsh. The delineated wetlands, which encompassed approximately picked and reamplifed for subsequent nucleic Pleistocene/Holocene gypsiferous lake sediments 1,188 acres in 1997, have a salt-marsh ecosystem. acid sequencing and phylogenetic analyses. of the Tularosa Basin (White Sands area) and The dominant species of marsh vegetation are NCBI BlastN shows the presence of bacteria Estancia Basin were studied, using sulfur isotope salt grass (Distichlis spicata), iodine bush (Allen- whose closest relatives are the Alpha-, Beta-, and methods, to try and identify primary sulfate sourc- rolfea occidentalis), and spike rush (Eleocharis Gammaproteobacteria, Cyanobacteria, and Bacte- es and determine the hydrologic cycle during the palustris). Some areas of the wetlands are season- roidetes. Novel species are suggested, including Holocene tectonic evolution of these basins. ally inundated by water. one whose closest relative is found in the marine Four sections of lake sediments taken from dif- The flow of Malpais Spring was estimated to be environment. Scanning electron microscopy ferent sites in the White Sands area show wide 2,000 gallons per minute (gpm) in 1911 and 1,500 (SEM) reveals the presence of bacteria of various variation in the δ34S values of sulfate minerals gpm in 1955. Instantaneous flow rates measured sizes, some possessing unique physiological fea- (from 2.2–13.8 ‰ vs. VCDT) suggesting differ- near the top of the main stream channel between tures that indicate direct interactions with their ent sulfate sources for and different sedimentary 1984 and 2007 ranged from 290 to 1,200 gpm. environment. Classic culturing techniques show environments in the southern and northern parts These measurements do not include the flow the presence of oxides, indicating a similar bio- of the study area. In the southern part, mixing from some seeps and springs that discharge near genic process found in the natural environment. process between sulfate-rich fluids originating this stream channel and the upper marsh area. A from the dissolution of the middle (10.9–12.3 stream gage was installed on this stream channel ‰) and Lower (12.5–14.4 ‰) Permian strata by the U.S. Geological Survey and began opera- is indicated by a steady increase of δ34S values tion on 25 July 2003. At least two peak flows of Geochemistry and Potential Sourc- (11.3–13.8 ‰) and linked to discharge of deeper- about 1,930 gpm were recorded during January es of the January 7, 2008, South- seated ground water through fault-related frac- 2004 and August 2006. western New Mexico “Milky Rain”, tures. This process was probably controlled by Water quality at the points of discharge in the J. Gilbert, [email protected], Environmental climate change and/or episodes of increased tec- Malpais Spring area has remained somewhat Science Program, University of Texas at El

May 2008, Volume 30, Number 2 Ne w Me x i c o Ge o l o g y 59 Paso, 500 West University Avenue, El Paso, prolonged summer rainy season. We find that LATE PLIOCENE (BLANCAN) VERTEBRATE Texas 79968 and Department of Geological Sci- there appears to be dew point threshold (analo- faunaS FROM PEARSON MESA, HIDAL- ences, University of Texas at El Paso, El Paso, gous to monsoon onset indices developed for GO County, NEW MEXICO, AND GREEN- Texas 79968; T. E. Gill, Department of Geologi- sites in Arizona) that may indicate the start of the LEE County, ARIZONA, G. S. Morgan, gary. cal Sciences, University of Texas at El Paso, El monsoon, consistent with the onset of persistent [email protected], P. L. Sealey, and S. G. Paso, Texas 79968 and Environmental Science precipitation that nearly matches the accepted Lucas, New Mexico Museum of Natural His- and Engineering Program, University of Texas historic start date of July 7th. tory and Science, 1801 Mountain Road NW, at El Paso, El Paso, Texas 79968; D. Borrok, At this time we are refining the monsoon onset Albuquerque, New Mexico 87104 Department of Geological Sciences, University criterion based on precipitation and dew point, Exposures at Pearson Mesa in the Duncan Basin of Texas at El Paso, El Paso, Texas 79968; B. Frey, to take into account “false starts” that may be along the New Mexico–Arizona border have New Mexico Bureau of Geology and Mineral associated with transient mid-latitude weather produced a diverse assemblage of late Pliocene Resources, New Mexico Institute of Mining systems but are not associated with a large-scale (Blancan) vertebrates. The stratigraphic section and Technology, Socorro, New Mexico 87801; monsoon circulation. We will develop a time at Pearson Mesa consists of more than 60 m of T. Hertel, New Mexico Environment Depart- series of onset dates to examine the relationships sandstones, mudstones, and sedimentary brec- ment, New Mexico Air Quality Bureau, 1301 between monsoon onset, total seasonal precipita- cias of the Gila Group. Two distinct vertebrate Siler Road, Building B, Santa Fe New Mexico tion, and possible antecedent predictors of the faunas occur at Pearson Mesa: the early late Blan- 87507; M. Lane, Department of Geography, monsoon, and to consider whether the onset can Pearson Mesa Local Fauna (LF) is derived University of New Mexico, 1 University Lane, date has been changing during the past several from the lower 15 m of the stratigraphic section, Albuquerque, New Mexico 87131; M. Bleiweiss, decades. and the latest Blancan Virden LF occurs in the Department of Entomology, Plant Pathology upper 20 m of the section. The Pearson Mesa and Weed Science, New Mexico State Universi- Poster Session 1—Paleontology fauna consists of 25 species: three land tortoises ty, Las Cruces, New Mexico 88003; C. Lehmann, (Gopherus and two species of Hesperotestudo); and D. Gay, National Atmospheric Deposition TURONIAN AMMONITES FROM THE box turtle (Terrapene); colubrid snake; bird; and Program, Illinois State Water Survey, Universi- UPPER CRETACEOUS CARLILE AND 19 mammals. Age-diagnostic mammals from ty of Illinois Urbana-Champaign, 2204 Griffith SEMILLA SANDSTONE MEMBERS AND the Pearson Mesa LF include: the ground sloth Drive, Champaign, Illinois 61820 REFERENCE AREA OF THE JUANA LOPEZ Paramylodon cf. P. garbanii; the pocket gopher On the afternoon of January 7, 2008, an approxi- MEMBER OF THE MANCOS SHALE, EAST- Geomys persimilis; the cotton rat Sigmodon medi- mately 1,300 km2 region of Grant County, New ERN SIDE OF THE SAN JUAN BASIN, LA us; the three-toed horse Nannippus peninsulatus; Mexico, stretching northeast from White Signal, VENTANA, SANDOVAL COUNTY, NEW the one-toed horses Equus cf. E. cumminsii, and New Mexico, to Gila Cliff Dwellings, was subject MEXICO, P. L. Sealey and S. G. Lucas, New E. simplicidens; and the peccary Platygonus bical- to rainfall of milky-white color. Concerned resi- Mexico Museum of Natural History and Sci- caratus. The association of Paramylodon and Nan- dents, who collected samples from cisterns, rain ence, 1801 Mountain Road NW, Albuquerque, nippus defines a restricted interval of time in the gages, and roof runoff, contacted area universi- New Mexico 87104 Blancan between the first appearance of South American immigrants (including Paramylodon) in ties and state agencies to arrange for chemical At the reference section of the Juana Lopez Mem- analyses. Initial speculation targeted everything the southwestern US at ~3.0 Ma and the extinc- ber of the Mancos Shale near La Ventana in central tion of Nannippus at ~2.2 Ma. Magnetostratig- from mine tailings to Pacific Rim volcanic ash New Mexico, the unit is thick and well exposed. before wind back trajectories and MODIS satel- raphy further constrains the age of the Pearson In 1966 Dane and others reported a reference Mesa LF, with five normally magnetized sam- lite images indicated a possible regional source: section of 107 ft thick, the same thickness as the Willcox playa sediments. Analysis of major ions ples from the lower part of the section referred type section at Galisteo Dam. The Juana Lopez to the uppermost Gauss Chron (Chron 2An.1n; indicated elevated levels of calcium, sodium, sul- consists of three lithic intervals—lower calcaren- 2.58–3.04 Ma). Southwestern early late Blancan fate, and chloride, as would be expected in playa- ites, middle shale, and upper calcarenites, and is faunas (~2.6–3.0 Ma) correlative with Pearson type deposits. Ratification came from a National underlain by the Carlile Member of the Mancos Mesa include: Anapra, New Mexico; Wolf Ranch Atmospheric Deposition Program site at the Gila Shale. Only the upper part of the Carlile Member and 111 Ranch, Arizona; and Cita Canyon and Cliff Dwellings, which determined the calcium is exposed at La Ventana, and the Semilla Sand- Hudspeth, Texas. A 10-m-thick sedimentary content of the rain to be within the top 1.0% of stone Member is very thin. The ammonite fauna breccia overlying the Pearson Mesa LF lacks fos- all data gathered by the network in a typical 5 from the Carlile and Semilla includes Prionocy- sils and may represent a hiatus. The Virden LF yr period. On February 5, 2008, the New Mexico clus hyatti (Stanton), Coilopoceras springeri Hyatt, consists of 22 species: toad; large Hesperotestudo; Environment Department concluded that the Romaniceras (Romaniceras) mexicanum Jones and Terrapene; colubrid snake; lizard; two birds; and event samples had similar chemistry to surface Placenticeras cumminsi Cragin. The ammonite 15 mammals. A latest Blancan age (~1.8–2.2 Ma) water samples obtained from the Lordsburg pla- fauna from the Juana Lopez includes Scaphites for the Virden LF is indicated by the presence yas in the early 1990s and reassured the public whitfieldi Cobban, Prionocyclus novimexicanus of the dwarf cotton rat Sigmodon minor and the regarding its possible toxicity. Further research (Marcou), Prionocyclus macombi Meek, Coilopocer- small camelid Hemiauchenia gracilis, both restrict- will include trace element analysis of dissolved as colleti Hyatt and Baculites sp. Ammonite diver- ed to latest Blancan faunas, and the association constituents in the rain water, analysis of the sus- sity in the upper calcarenite interval of the Juana of the glyptodont Glyptotherium arizonae with the pended (non-dissolved) materials and recently Lopez is lower than at the type section. It includes coyote-like canid Canis lepophagus. Southwestern acquired dust samples. We present an overview primarily P. novimexicanus, secondarily S. whit- latest Blancan faunas correlative with Virden of this event, the meteorological characteristics fieldi, and rarely Baculites sp. The middle shale include: La Union, New Mexico, and Curtis of the “milky rain” storm, and the geochemistry interval, as at the type section, has a low diver- Ranch and San Simon, Arizona. of the materials. sity ammonite fauna dominated by P. macombi with an occasional C. colleti. The P. hyatti Zone, Bite Marks on a skull of Pseudop- An index of the onset of the North present in the Carlile Member at La Ventana, also occurs in other places in New Mexico, especially alatus mccauleyi (aRCHOSAURIA: American monsoon season in cen- cRUROTARSI: pHYTOSAURIDAE) FROM tral New Mexico, P. Higgins, phiggins@ in the Carlile Member at Galisteo Dam. The P. macombi and P. novimexicanus Zones are present THE UPPER TRIASSIC BULL CANYON unm.edu, D. Gutzler, Department of Earth and FORMATION, EASTERN NEW MEXICO, Planetary Sciences, University of New Mexi- in the Juana Lopez Member at La Ventana. The P. macombi Zone also occurs in many other places L. F. Rinehart, [email protected], New co, Albuquerque, New Mexico 87131; and D. Mexico Museum of Natural History and Sci- Kann, NOAA National Weather Service, Albu- in New Mexico, including the basal part of the Juana Lopez Member in Colfax County, where ence, 1801 Mountain Road NW, Albuquerque, querque, New Mexico 87106 New Mexico 87104; A. B. Heckert, heckertab@ the lectotype of P. macombi was collected. The appstate.edu, Department of Geology, Appala- We develop an objective index to indicate the zone of P. novimexicanus also occurs at various chian State University, ASU Box 32067, Boone, start of the monsoon season in central New New Mexico locations, especially in the D-Cross North Carolina 28608; S. G. Lucas, and D. C. Mexico using data from several measuring sta- Member of the Mancos Shale. The P. hyatti Zone Bond, New Mexico Museum of Natural His- tions around Albuquerque. The weather vari- is of middle Turonian age, the P. macombi Zone is tory and Science, 1801 Mountain Road NW, ables being considered include dew point, daily P. novimexi- of late-middle Turonian age, and the Albuquerque, New Mexico 87104 precipitation, relative humidity, and wind. With canus Zone is of late Turonian age. these data we are attempting to define and quan- A 1.12-m-long brachyrostral phytosaur skull tify noticeable changes that mark the onset of a (NMMNH P-56187) from the Upper Triassic

60 Ne w Me x i c o Ge o l o g y May 2008, Volume 30, Number 2 Bull Canyon Formation of eastern New Mexico to the New Mexico Museum of Natural History AN UPPER Cretaceous (LOWER CAM- is assigned to Pseudopalatus mccauleyi based on and Science (NMMNH) by the NMBMMR in late PANIAN) feather from the POINT its poorly preserved, but apparently depressed 1993 and accessioned into the NMMNH collec- LOOKOUT SANDSTONE, northwest- supratemporal fenestrae, its subtriangular squa- tion in 1998. It represents one of the most exten- ern New Mexico, T. Williamson, thomas. mosal process, and completely crested rostrum. sive collections of Ordovician cephalopods in [email protected], New Mexico Muse- The skull is obliquely flattened, exposing the left the country, if not the world. Unfortunately, the um of Natural History and Science, 1801 side of the face and skull roof. The lachrymal- Socorro collection, with its ~10,000 specimens, Mountain Road NW, Albuquerque, New nasal area, bounded by the external nares, antor- was too large to tackle for many years. However, Mexico 87104; B. S. Kues, G. S. Weissmann, bital fenestra (aofe), and orbit on the left side, is in 2004, one of us (ABH) initiated with two vol- Department of Earth and Planetary Sciences, punctured by three large holes, one immediately unteers (JM and DT) the long process of going University of New Mexico, Albuquerque, New dorsal to the middle of the aofe and two more through the Socorro collection in order to catalog Mexico 87131; T. A. Stidham, Department of (paired?) posterior to the first and approximately specimens and localities. This was accomplished Biology, Texas A&M University, 3258 TAMU, halfway between the aofe and the orbit. Based by using a single ledger kept by Flower and his College Station, Texas 77843; and S. L. Yurchyk, on size and shape, these holes appear to repre- various publications to assign as much locality Department of Earth and Planetary Sciences, sent bite marks, probably from another (possi- and taxonomic information to the specimens as University of New Mexico, Albuquerque, New bly conspecific) phytosaur. The three marks thus possible. The locality information obtained from Mexico 87131 form an “L” and probably represent two teeth the ledger was transferred to GPS coordinates Fossils of Cretaceous feathers are extremely rare, from one side of the biting animal’s jaw and one (UTMs) and entered into the NMMNH local- especially from clastic sediments. Here we report from the other, although the orientation of attack ity database, thus ensuring the data would be on a partial pennaceous feather collected from is not clear. The larger holes may mark wounds recorded for future research. The Socorro col- the lower Campanian Point Lookout Sandstone inflicted by the large teeth in the “bulb” of a phy- lection now represents a significant portion of of northwestern New Mexico (New Mexico tosaur snout, with the smaller injury attributed the NMMNH geoscience collection, over 2,000 Museum of Natural History locality L-7468). The to a smaller, more posterior tooth. The edges of of the 56,000 cataloged specimens, including 351 feather is from a laterally discontinuous shale at the holes are smooth and rounded, evidently holotypes, 10 topotypes, 155 paratypes, and 21 the top of the Point Lookout Sandstone, a basal having healed. syntypes. marine shoreline facies deposited during the R-4 The tooth marks measure: (1) 27 x 10 mm, (2) The process of cataloging is still ongoing, under regressive cycle. The shale contains cylindrical 25 x 13 mm, and (3) 16 x 14 mm. The combina- the direction of the senior author in conjunction invertebrate burrows including Ophiomorpha, tion of elongate and approximately round punc- abundant plant fragments of conifers and angio- tures supports assignment of the bite mark to the with other NMMNH staff. In 2007 the NMMNH was able to purchase, with BLM supported sperms, and a sparse invertebrate fauna includ- ichnotaxon Heterodontichnites hunti. This is only ing the inarticulate brachiopod Lingula and the the second bite mark on a phytosaur fossil of funds, five new collections cabinets to house the now curated Socorro collection. Finally, 15 yrs pelecypods Caryocorbula and Nucula. The flora which we are aware. The other is in the palate of and fauna of the shale unit suggest deposition a large skull of Redondasaurus bermani (NMMNH after the initial transfer these critically important fossils, once at risk, now have a permanent home in a quiet pond, probably on a delta-plain mud P-31094) from the Redonda Formation of east- flat, that was close enough to the shoreline to central New Mexico. This injury comprises three where they will be kept for future research and display. receive marine water and allow influx of sparse smaller (9–12 mm), approximately round punc- marine invertebrates, but also rendered brackish tures in a gently curved line that is 45 mm long. by fresh-water runoff. These punctures show healed edges and may The partial pennaceous feather, University of molding and CASTING A Redonda- have been self-inflicted. Thus, the Pseudopalatus New Mexico (UNM) 14742, is preserved on a saurus (archosauria: phytosau- bite mark is the first unambiguous evidence of a bedding plane as either a carbonized trace or an ridae) Skull using elements from phytosaur suffering an attack from another phy- autolithification. The feather is missing the basal three different animals, D. R. Uli- tosaur of which we are aware. barbs and the base of the rachis and calamus and barri, [email protected], New Mex- has a preserved length of 12.6 mm and a maxi- ico Museum of Natural History and Science, mum width of 6.2 mm. It possesses numerous THE ROUSSEAU H. FLOWER INVERTE- 1801 Mountain Road NW, Albuquerque, New barbs that are arrayed in symmetrical vanes. BRATE FOSSIL COLLECTION: CONSERVA- Mexico 87104 About three barbs per millimeter occur on each TION AND CURATION, J. A. Spielmann, New To produce a large (1.2-m-long) Redondasaurus side of the rachis, and the bases of 25 barbs are Mexico Museum of Natural History and Sci- bermani skull and jaw for the New Mexico Muse- preserved within each vane. Nine barbules per ence, 1801 Mountain Road NW, Albuquerque, um of Natural History and Science’s Triassic millimeter were counted along the distal side New Mexico 87104 and Department of Earth exhibit hall, elements of three different animals of one of the barbs on the left vane. The vanes and Environmental Science, New Mexico Insti- had to be sculpted together. The skull (NMMNH decrease in width toward a rounded tip. Both tute of Mining and Technology, Socorro, New P-31094) was missing its snout and lower jaw. vanes show gaps that indicate the barbs nor- Mexico 87801; J. McDonnell, D. Traeger, New A Redondasaurus snout (NMMNH P-25654) that mally interlocked and so possessed differenti- Mexico Museum of Natural History and Sci- was found nearby, but clearly belonging to a dif- ated distal and proximal barbules. Based on this ence, 1801 Mountain Road NW, Albuquerque, ferent animal, was sculpted onto the skull using morphology, UNM 14742 is a closed pennaceous New Mexico 87104; A. B. Heckert, Department Klean Klay. Photographs of the type skull of feather (Stage IV) and a contour feather and can of Geology, Appalachian State University, ASU be referred to Maniraptora, a group that includes Box 32067, Boone, North Carolina 28608; S. G. Redondasaurus bermani at the Carnegie Museum true birds and coelurosaur dinosaurs. It probably Lucas, New Mexico Museum of Natural His- in Pittsburgh, Pennsylvania, were used to estab- represents a bird. tory and Science, 1801 Mountain Road NW, lish the correct length to width ratio for an accu- Albuquerque, New Mexico 87104; and P. M. rate recreation of the complete skull. Because no Hester, Bureau of Land Management, 435 Mon- high quality lower jaws of Redondasaurus were Poster Session 2—Stratigraphy, tano NE, Albuquerque, New Mexico 87107 available for molding, a lower jaw from Pseudo- Structure, and Mapping palatus mccauleyi (NMMNH P-4256) was molded Rousseau H. Flower (1913–1988), formerly of and sculpted to fit the skull. Approximately PENNSYLVANIAN STRATIGRAPHY ON the New Mexico Bureau of Mines and Mineral 200 teeth (NMMNH P-31096, P-17036, P-17026, THE NORTHERN FLANK OF THE OSCU- Resources (NMBMMR), was one of the most P-44047) of Redondasaurus were molded in RTV important invertebrate paleontologists in the RA MOUNTAINS, SOCORRO COUNTY, silicone, cast in polyurethane, and glued into the history of New Mexico geology. His prolific col- NEW MEXICO, S. G. Lucas, spencer.lucas@ original tooth sockets. lecting and publishing established four orders, state.nm.us, Museum of Natural History and The right rear portion of the original skull was approximately 100 genera, and over 400 spe- Science, 1801 Mountain Road NW, Albuquer- slightly flattened, and the right quadrate some- cies of invertebrates, most of them cephalopods. que, New Mexico 87104; K. Krainer, Institute of what splayed out. In order to remove this distor- Many of his specimens were collected from BLM- Geology and Paleontology, University of Inns- tion from the final product, the cast had to be administrated lands in New Mexico and Texas. bruck, Innsbruck, A-6020, AUSTRIA; L. F. Rine- The extensive collection produced by Flower is drawn from the mold during the pre-cure stage hart, and J. A. Spielmann, New Mexico Museum one of the most important records of Paleozoic and reshaped while the resin was still soft and of Natural History and Science, 1801 Mountain invertebrates in the country. pliable. Road NW, Albuquerque, New Mexico 87104 A major portion of this collection (later known The Pennsylvanian strata exposed on the north- as the Socorro or Flower collection) was given ern flank of the Oscura Mountains are a classic

May 2008, Volume 30, Number 2 Ne w Me x i c o Ge o l o g y 61 section because M. L. Thompson used it as a key in discharge. At the end of the Pleistocene, vast that range from about 0.1–3.5 km long that may reference section in his 1942 monographic syn- quantities of sediment-rich, glacial meltwater represent a larger sheet that has been fragmented thesis of the Pennsylvanian in New Mexico. This flowing out of the Sacramento Mountains down and partly eroded. section is ~334 m thick, and we assign it to the the Rio Hondo built a vast fluviodeltaic fan out New 40Ar/39Ar ages for intrusive and extru- Sandia, Gray Mesa, Atrasado, and Bursum For- onto the Pecos River floodplain. This initiated sive rocks include the following: (1) El Alto mations. The Sandia Formation is thin (~13 m), meandering atop of the braid plain upstream of Basalt, 2.82 ± 0.05 Ma (isochron age), 2.86 ± overlies Precambrian granite, and is mostly shale the fan in response to a decrease in gradient. A 0.05 Ma (plateau age); (2) Servilleta Basalt, 3.45 and sandy limestone. The lowest cherty limestone segment of this initial meander belt, preserved ± 0.06 Ma (isochron age), 3.69 ± 0.45 Ma (pla- ledge marks the base of the overlying Gray Mesa north of Bitter Lake, likely carried flows concomi- teau age); (3) Sierra Negra Basalt, 5.44 ± 0.06 Ma Formation, which is ~162 m thick. Most of the tantly with braided channels to the east during the (isochron age), 5.56 ± 0.12 Ma (plateau age); (4) Gray Mesa is limestone (63% of the section), the early Holocene. The Rio Hondo fan pushed the Lobato Basalt/dike, 10.05 ± 0.07 Ma (isochron remainder is covered slopes (shale?), most of the Pecos River eastward into collapse depressions at age), 10.11 ± 0.13 Ma (plateau age); 9.57 ± 0.11 limestones are cherty and numerous fusulinid this time as well, which allowed the Rio Hondo to Ma (isochron age), 9.51 ± 0.21 Ma (plateau age); packstones are present. The Atrasado Formation build meander belts across the Pecos River braid and 7.83 ± 0.07 Ma (isochron age), 7.87 ± 0.10 Ma is ~124 m thick and includes (in ascending order) plain to the south during the early to middle Holo- (plateau age); (5) Cerrito de la Ventana basaltic the Veredas, Hansonburg, and Keller groups of cene. Pecos River meander morphometry clearly dike, 19.22 ± 0.30 Ma (isochron age), 19.58 ± 0.09 Thompson, names that should be abandoned. distinguishes late Holocene to historic meander Ma (weighted mean age); and (6) basaltic dike The facies ranges from siliciclastic sandstone and belts from those of the early Holocene, as meander of Red Wash Canyon, 19.63 ± 0.40 Ma (isochron fine-grained conglomerate to bedded fossilifer- amplitudes and wavelengths greatly increase up age). In-progress geochemical analyses by XRF ous limestone of an open marine shelf to mas- to a maximum 2 km wide meander with a wave- (major element) and INAA (trace element) will sive algal limestone of a mound facies formed length of 1.6 km, recorded from a 1940-vintage help resolve the geochemical evolution for these just below wave base in quiet water in the photic aerial photograph. Extensive man-made meander rocks. zone. The formations named by Thompson work cutoffs were constructed in the 1950s and 1960s, as local lithostratigraphic units at the member resulting in a modern channel that exhibits few, or bed rank. Thus, we recognize (in ascending small meanders that are typically locked into bed- Precambrian basement of the Defi- order) the Adobe Member (33.5 m), Council rock or former braided channel courses. ance uplift—possible correlation Springs Bed (4.8 m), Burrego Member (16.4 m), to the Uncompahgre Quartzite Story Member (18.3 m), Del Cuerto Member and influences of basement fab- (34.8 m), and Moya Member (16.5 m) of the SUMMARY OF THE GEOLOGY, GEO- ric on later tectonism, B. Dixon, Atrasado Formation. The Bursum Formation CHRONOLOGY, AND GEOCHEMISTRY and K. E. Karlstrom, Department of Earth and overlies the Atrasado Formation and is 35 m of OF THE ABIQUIU 1:24,000 QUADRANGLE Planetary Sciences, University of New Mexico, marine limestone and red-bed clastics. Abo For- AND CONTIGUOUS AREAS, NORTH- Albuquerque, New Mexico 87131 mation red-bed siliciclastics overlie the Bursum CENTRAL NEW MEXICO, F. Maldonado, Formation and are of presumed earliest Permian [email protected], D. P. Miggins, and J. R. The Defiance uplift is an asymmetrical basement- age. Fusulinids indicate that the Desmoinesian– Budahn, U.S. Geological Survey, MS 980, Den- cored, fault-bounded uplift of Ancestral Rockies Missourian boundary is in the upper Gray Mesa ver Federal Center, Denver, Colorado 80225 and Laramide age located entirely on the Navajo Formation, the Missourian–Virgilian boundary is The Abiquiu quadrangle is located within the Nation in northeast Arizona and northwest New ~ base of Del Cuerto Member, and the Wolfcam- Abiquiu embayment, a shallow, early extensional Mexico. Small outcrops of Precambrian rocks pian (Newwellian) base is ~ base of Bursum. basin of the Rio Grande rift near the eastern mar- occur in four canyons (Blue Canyon, Meadow gin of the Colorado Plateau–Rio Grande rift in Wash, Fork Canyon, and Hawk Canyon) that north-central New Mexico. The geology, newly drain the east side of the uplift (total outcrop 2 LATE QUATERNARY DEVELOPMENT OF determined 40Ar/39Ar dates and geochemical area of < 1 km ). Blue Canyon and Meadow THE PECOS RIVER FLOODPLAIN, BITTER data, and a newly discovered low-angle fault Wash contain quartzites, with no contact rela- LAKE QUADRANGLE, NEW MEXICO, D. J. are described. Rocks exposed in the quadrangle tionships exposed. These are medium-grained McCraw, [email protected], New Mexico Bureau and contiguous areas include continental Paleo- quartz arenites with well-preserved ripple marks of Geology and Mineral Resources, New Mexi- zoic and Mesozoic strata of the Colorado Pla- and crossbeds, lithologically very similar to the co Institute of Mining and Technology, Socorro, teau, Cenozoic basin-fill deposits, and Tertiary Uncompahgre Quartzite of southwest Colorado New Mexico 87801 volcanic rocks. Paleozoic units include the Late exposed about 200 km to the northeast. Fork and The floodplain architecture of the Pecos River Pennsylvanian to Early Permian Cutler Group, Hawk Canyons contain thinly laminated, low- valley within the Bitter Lake quadrangle is com- undivided. Mesozoic units are, in ascending grade argillite and grayish-green, highly altered prised of: 1) basal late Pleistocene braided stream order, the Upper Triassic Chinle Group, undi- greenstone (metabasalt). These are intruded by deposits; 2) distinct Holocene (2) and historic (2) vided, and Middle Entrada Sandstone several different granitoids: fine-grained gran- meander belts; 3) backswamp or spring cienega and Todilto Limestone Member of the Wanakah ite (probably 1.7–1.65 Ga), altered granite por- deposits beneath older Pecos River terraces to Formation. Cenozoic rocks include the Eocene phyry, megacrystic granite (likely 1.4 Ga), and the west; 4) thin alluvial veneers and karstic col- El Rito Formation, newly named Oligocene con- aplite and pegmatite dikes. Based on correlation lapse depressions atop of Permian Seven Rivers glomerate of Arroyo del Cobre, Oligocene–Mio- of aeromagnetic highs with granites encoun- Formation gypsum on the east; 5) a large, late cene Abiquiu Formation, and Miocene Chama– tered in drill holes, the basement of the uplift Pleistocene braided fluviodeltaic fan complex of El Rito and Ojo Caliente Members of the Tesuque appears dominated by granitoids. U-Pb zircon the Rio Hondo to the southwest; and 6) two early Formation of the Santa Fe Group. Intrusive and ages on basement xenoliths from the nearby to middle Holocene Rio Hondo meander belts extrusive rocks include the basaltic dike of Red Tertiary diatremes (Condie et al. 1999) include that prograded across the Pecos River floodplain Wash Canyon (Miocene), Cerrito de la Ventana both Paleoproterozoic granites (1,725–1,603 Ma) below the confluence. Pecos River alluvium is basaltic dike (Miocene), Lobato Basalt (Miocene), and Mesoproterozoic granites (1,453–1,381 Ma). light-reddish-brown, medium-grained quartzose Sierra Negra Basalt (Miocene–Pliocene), Serville- The assemblage and ages of Proterozoic rocks sand and pebbly sand; gravel consists of sand- ta Basalt (Pliocene), El Alto Basalt (Pliocene), and are thus similar to the Yavapai–Mazatzal transi- stone, quartzite, chert, igneous rocks, and minor dacite of the Tschicoma Formation (Pliocene). tional boundary zone elsewhere in New Mexico. carbonates, except in backswamp areas, which Quaternary deposits consist of ancestral axial Structure contour and isopach maps show a contain silt, clay, and gypsite. South of the Rio and tributary Rio Chama deposits, landslide col- gentle westward dip of the Great Unconformity Hondo confluence, Pecos River alluvium inter- luvium, and Holocene floodplain alluvium, fan accompanied by westward thickening of Paleo- mixes with Rio Hondo alluvium, which is dark and pediment alluvium. Faults in the quadran- zoic rocks (Werme 1981), indicating an Ancestral yellowish brown in color, and contains abun- gle are Tertiary normal faults that displace rocks Rockies history. The faulted east side, coincident dant porphyritic igneous and carbonate gravel. toward the rift and minor Mesozoic thrust faults. with East Defiance monocline, is likely Laramide Floodplain alluvium thickness decreases from A low-angle fault, referred to here as the Abiquiu in age, with possible right strike-slip movement a maximum of around 45 m along the western fault, separates an upper plate composed of the (Kelley 1955). Evidence for basement-controlled margin to <1 m to the east. transitional zone of the Chama–El Rito and Ojo localization of Phanerozoic structures includes Large Pleistocene-age braid plains are exposed Caliente Members of the Tesuque Formation parallelism of a prominent northeast-trending on the northern and southern edges of the quad- from a lower plate consisting of the Abiquiu aeromagnetic high and the Nazlini northeast- rangle. These resulted from steeper gradients, eas- Formation or the conglomerate of Arroyo del trending fault and deflection of the East Defiance ily erodible banks, and a much greater variability Cobre. The upper plate is distended into blocks monocline at the same basement anomaly.

62 Ne w Me x i c o Ge o l o g y May 2008, Volume 30, Number 2 AMS Data Bearing on the Deforma- which dissects a portion of the batholith. Major and/or “ heavy breathing” of a smaller shallow tional History of the Protero- rock types include quartzofeldspathic gneisses magma body as suggested by GPS data col- zoic Basement in the Las Vegas and laminated amphibolites. The felsic gneisses lected since 2003 (Newman et al. 2004). "Heavy Area, Southern Sangre de Cristo contain microcline + albite + quartz ± biotite in breathing" is a common metaphor for alternat- Mountains, New Mexico, L. Garcia, M. a medium- to coarse-grained anhedral granular ing magma chamber inflation and deflation over S. Petronis, J. Lindline, Department of Natural texture. Muscovite is rare and often secondary periods of several years or decades, as observed Sciences, New Mexico Highlands University, in origin. The felsic gneisses commonly display in the vicinity of several "restless" Quaternary Las Vegas, New Mexico 87701; and J. W. Geiss- quartz ribbons and microcline porphyroclasts calderas. man, Department of Earth and Planetary Sci- and are interpreted as metagranites. They have When viewed together in a relative and quali- ences, University of New Mexico, Albuquer- Rb-(Y+Nb) and Nb-Y variations indicative of tative sense, averaged tiltmeter data for stations que, New Mexico 87131 volcanic-arc granites. The mafic gneisses contain north and west of San Acacia suggest a period of Models for the deformational history of deep- to hornblende + plagioclase + quartz + titanite ± magmatic uplift (inflation) was occurring from middle-crustal rocks rely heavily on the docu- epidote and display a fine- to medium-grained the fall of 2002 to the summer of 2004. Tilting mentation of rock structures, which are not subhedral granular to idioblastic texture. They dominantly toward San Acacia from the sum- always detectable in the field. Anisotropy of show igneous differentiation trends on Niggli mer of 2004 to the fall of 2006 may represent a magnetic susceptibility (AMS) analysis allows variation diagrams and are interpreted as meta- period of magmatic deflation. Inflation may now for the evaluation of non-visible petrofabrics as basalts. They plot as island arc tholeiites and be ongoing. it can detect structural anisotropies of less than ocean island arc basalts on tectonic discriminant The apparent motions of local fault blocks are clearly not unidirectional, and when viewed in 1% in rock samples. We conducted anisotropy of diagrams. The granite gneisses and amphibolite an absolute sense some patterns seem counter- magnetic susceptibility (AMS) analysis on Pro- gneisses are interpreted as part of an arc system intuitive. Clearly, longer-term records of tilt and terozoic basement rocks west of Las Vegas, New that was accreted to North America during the perhaps more tiltmeters are warranted. Tiltme- Mexico, in an attempt to better document and assembly history of the continental lithosphere. ter data may ultimately be temporally correlated The bimodal nature of igneous activity suggests interpret deformation features. We studied medi- to surface motions currently being measured by a magmatic rift may have been operative dur- um-grade gneisses cropping out along County nearby continuous GPS stations and new INSAR Road 65 in the Gallinas Canyon, which dissects a ing their formation. We continue to analyze our data. portion of the Hermit’s Peak batholithic complex. data to see if differentiation of the proposed rift Rock types include quartzofeldspathic gneisses, setting (juvenile or continental) is possible and biotite schists, and laminated amphibolites. The test whether our data are consistent with an arc Incision history of the Rio Salado gneisses show intense penetrative deformation accretion model or if an expanded model includ- and implications for uplift histo- defined by a strong steeply dipping, northeast- ing crustal extension is required. ry of the Jemez Mountains, T. Sower, trending axial planar foliation. Minor macro- [email protected], D. Rose-Cose, K. E. Karl- scopic linear structures, including isoclinal fold strom, L. J. Crossey, Y. Asmerom, and V. Polyak, hinges and prismatic mineral alignments, plunge PRELIMINARY INTERPrETATION OF SIX Department of Earth and Planetary Sciences, moderately to the southwest. Oriented AMS YEARS OF TILTMETER MOTIONS ABOVE University of New Mexico, Albuquerque, New samples, typically eight to twelve samples per THE FLANKS OF THE SOCORRO MAGMA Mexico 87131 site, were collected from twelve sites through- BODY, CENTRAL RIO GRANDE RIFT, D. out the canyon. All samples were analyzed on W. Love, [email protected], B. D. Allen, R. M. The Rio Salado, a tributary to the Jemez River, an AGICO static KLY-4S Magnetic Susceptibil- Chamberlin, New Mexico Bureau of Geology has a suite of strath terraces that record the inci- ity/Anisotropy System at the University of New and Mineral Resources, New Mexico Insti- sion history of the south and west sides of the Mexico Rock Magnetism Laboratory in order to tute of Mining and Technology, Socorro, New Jemez/Nacimiento Mountains. The goal of the characterize the magnetic mineralogy and mag- Mexico 87801; and W. C. Haneberg, Haneberg project is to map Quaternary units, establish the netic fabric of the rocks. Preliminary rock mag- Geoscience, 10208 39th Avenue SW, Seattle, heights of terraces, correlate Rio Salado and Rio netic data indicate that the dominant magnetic Washington 98146 Jemez terraces, and evaluate the incision history of the southern flank of the Jemez Mountains to phase in most specimens is a ferri/ferromagnetic Three shallow (3 m) biaxial borehole tiltmeters oxide (magnetite, maghemite) as demonstrated evaluate possible surface uplift due to magmatic in place around the margins of the uplift above by an average bulk susceptibility of 8.5 x 10−3 inflation associated with the Jemez lineament the Socorro Magma Body (SMB) since 2002 show SI. Additional rock magnetic experiments are and/or Jemez volcano. near-surface ground motions at several temporal being conducted to further assess the magnetic Straths on the south flank of the Nacimiento scales. Two tiltmeters are located in narrow gra- mineralogy. The AMS fabric data are consistent uplift are cut into the Petrified Forest Member bens of the Rio Grande rift about 15–20 km north with the macroscopic structural features, partic- of the Chinle Formation. They are mantled by and south of the center of historic uplift near San ularly the lineations, which were visible at only thin (1–10 m) cobble to boulder gravels with Acacia. The north station is in a symmetrical gra- a fraction of the study sites. We propose that our basement lithologies that were sourced in the ben; it may be more responsive to magmatic tilt petrofabric and rock magnetic data reflect the nearby Nacimiento Mountains. Nine strath ter- than tectonic tilt. A third tiltmeter at Silver Creek dominance of northwest-southeast contractional races were mapped, with strath heights above is located on a west-tilted rift block about 15 km deformation and southwest-northeast extension the modern channel as follows: Qt1 2 m, Qt2 2–7 in the assembly history of the continental litho- west of San Acacia, where magmatic uplift and m, Qt3 20 m, Qt4 30 m, Qt5 44 m, Qt6 60 m, Qt7 sphere during the Proterozoic. Our study shows tectonic tilt should be additive. 113 m, Qt8 140–147 m, Qt9 164–183 m. These ter- races can be correlated along the south side of that AMS petrofabric analysis is a simple yet The tiltmeters (Applied Geomechanics model 722) with selectable gain and output range of the river for 9.4 km from the confluence with the powerful tool for obtaining high-quality orienta- ± 2500 mV are set at high-gain resolution of ± 0.1 Jemez River, west to the Nacimiento fault. Cor- tion data from crystalline rocks for which visible microradians over a range of ± 800 microradians. relation is based on elevation above the channel rock structures are lacking or tenuous. Readings of north-south and east-west tilts, as and nature of the thin gravel and travertine fill. well as temperatures, are taken every 30 seconds Gravels are variably cemented and overlain by and the average recorded every 20 minutes. The travertine. Travertine springs are present near PRELIMINARY PETROLOGIC ANALySIS OF western datalogger also records local precipita- the modern floodplain Qt0/Qt1 and provide a PROTEROZOIC HERMIT’S PEAK BATHO- tion. The tiltmeter records show: 1) earth-tide modern analog for the higher travertine-cement- LITH ORTHOGNEISSES, NORTH-CEN- cycles of 10ths of microradians on the order of ed gravels. The Agua Zarca Sandstone Member TRAL NEW MEXICO J. Lindline , , lindlinej@ two per day, 2) surface waves of distant mod- of the Chinle Formation forms the dip slope of nmhu.edu, and R. Trevizo, roberttrevizo@hot- erate-to-large earthquakes that affect tilt aver- the southern Nacimiento and, together with mail.com, Department of Natural Sciences, ages over 20–40 minutes, 3) 10- to 20-day abrupt fault conduits for deeply sourced waters, forms New Mexico Highlands University, Las Vegas, excursions following large precipitation events, the plumbing system for the travertine spring New Mexico 87701 4) 10–14 month wavelike variations perhaps waters. Accompanying incision, the position of We report preliminary petrologic results on related to lagging seasonal temperature gradi- the active springs has migrated north down the mafic and felsic orthogneisses of the Her- ents at depth of burial, 5) a few abrupt excur- dip slope synchronous with northward migra- mit’s Peak batholith, a Proterozoic plutonic- sions of uncertain origin, and 6) multi-year long- tion of the river channel and retreat of cliffs of metamorphic complex in the southern Sangre term changes in average tilts, both in direction Entrada and Todilto Formations. Dates on the de Cristo Mountains northwest of Las Vegas, and magnitude. The last type of tilting may be travertine were obtained by U-Series methods on New Mexico. We studied rocks that crop out related to transient motions of either structural three of the terraces giving the following incision along County Road 65 in the Gallinas Canyon, blocks within the Rio Grande rift above the SMB, rates: Qt3/4 is 30.6 ± 0.3 ka (36 m/31 ka = 116 m/

May 2008, Volume 30, Number 2 Ne w Me x i c o Ge o l o g y 63 Ma); Qt8 is 415 ± 0.2 ka (140 m/415 ka = 337 m/ in the Red River valley (RRV), New Mexico, A prominent glacial unconformity, which prob- Ma); Qt9 is outside U-Series range (164 m/>500 records the timing of alteration scar formation ably represents either overriding by the Ross Ice ka = <328 m/Ma). and compositions of pyrite-oxidizing fluids. Sheet or formation of localized glaciers on the Weathering and subsequent erosion of pyrite- bluff, separates the lower volcanic section (domi- enriched hydrothermally altered bedrock along nated by basanite flows and breccias) from the Buried Landscapes—Paleotopogra- the Red River, a Rio Grande tributary in Taos central volcanic section (dominated by trachyte phy of the Cerro Toledo interval, County, New Mexico, forms alteration scars. domes and secondary basanite flows). Multiple 40 39 Bandelier National Monument, Ar/ Ar(jarosite) dates range from 4.45 ± 0.70 Ma pairs of samples were collected from both above Jemez Mountains volcanic field, at the highest elevations of a weathering profile and below this unconformity in order to best con- E. P. Jacobs, [email protected], 3007 Villa to 0.31 ± 0.23 Ma at lower elevations in a scar strain the period of glacial erosion. The youngest Street, Los Alamos, New Mexico 87544 ferricrete. Although supergene jarosite does not age from beneath the unconformity is 9.74 ± 0.07 always yield well-behaved plateaus with precise Ma and the oldest age above the unconformity is Prior landscapes preserved between eruptive 40 39 cycles of the Jemez volcanic field form subsurface Ar/ Ar(jarosite) ages, RRV jarosite ages consis- 9.53 ± 0.07 Ma. This leaves between 350,000 and pathways that influence the flow of contaminants tently preserve “inverse superposition” relation- 70,000 yrs (allowing for errors at two sigma) for and ground water. Knowledge of how fluids ships typical of incised landscapes. Alteration the glacial erosion to have taken place. move from the surface through perched zones to scar formation probably began ~4.5 Ma, which is the aquifer is still developing. This study looks at consistent with weathering dates found by pre- the prior landscape “sealed” between two major vious workers at nearby Creede, Colorado. AQUEOUS GEOCHEMISTRY OF THE 34 ash flows (Otowi and Tshirege Members of the d Sjarosite values (-12.1 to -0.8‰) that overlap SPRINGS AND WELLS OF THE SEVILLETA 34 18 Bandelier Tuff at 1.6 and 1.2 Ma), within Bande- δd Spyrite (-13.6 to +2.7‰) and δd O(SO4) that NATIONAL WILDLIFE REFUGE—EVALU- lier National Monument (BNM). The ~380,000 yr range from -4.6 to +2.3‰ confirm that RRV jarosite ATING HYDROLOGIC PATHWAYS AND interval between the Bandelier eruptions, infor- formed from supergene alteration of pyrite rath- MICROBIOLOGY, A. J. Williams, awill7@ mally termed the Cerro Toledo interval, contains er than hypogene fluids. As at Creede, Colorado, unm.edu, L. J. Crossey, and K. E. Karlstrom, as much as 120-m-thick deposits that provide δdDjarosite decreases in younger samples and may Department of Earth and Planetary Sciences, favorable settings for perched zones. Windows provide a continental climate record. However, University of New Mexico, Albuquerque, New into this landscape are exposed in Frijoles and this trend toward isotopically lighter fluids is not Mexico 87131 18 Alamo Canyons, two narrow, deeply incised reflected in the narrow δd O(SO4) range. The average RRV alteration scar incision rate Both ground water and surface water are impor- canyons that lie within the northern section tant sources for many metropolitan and agri- of BNM. Structure contour and isopach maps calculated based on elevation differences between cultural communities along the Rio Grande derived from field observations of exposed con- stranded, dated ferricretes and alteration scar corridor. Both high salinity and trace element tacts in BNM are combined with existing geo- drainages is 77 m/m.y. This rate is consistent with concentrations are regionally important in logic surface and drill-hole data for the southern published incision rates for the Rio Grande in impairing water quality. Although these waters part of Los Alamos National Laboratory to pro- northern New Mexico. Incision rates suggest that are dominated volumetrically by meteoritic vide a glimpse of the topography that developed alteration scar erosion, which began when the Rio before eruption of the Tshirege Member. The Grande had its headwaters in the RRV, began in sources, recent research has revealed the wide- nonwelded Otowi Member was easily eroded, response to base level changes in the Rio Grande spread presence of volumetrically small, but resulting in a landscape characterized by rolling as it became an integrated stream as far south as geochemically important, deep fluid sources. hills with gentle gradients. Episodic eruptions northern Mexico during the Pliocene. These “endogenic” waters have been associ- of plinian ash and erosion of the Sierra de los ated with springs issuing along rift-bounding Valles, accompanied by possible seismic shak- faults in central New Mexico. This study reports ing during the collapse of a portion of Rabbit 40AR/39AR GEOCHRONOLOGICAL ANALY- new geochemical data from springs and ground Mountain, resulted in pulses of sediment that SIS OF MINNA BLUFF, ANTARCTICA— waters in a cross-rift transect located in the Sevil- periodically overwhelmed developing drainage EVIDENCE FOR PAST GLACIAL EVENTS leta National Wildlife Refuge and evaluates con- systems. Regional base level was controlled by WITHIN THE ANTARCTIC CRYOSPHERE, tributions from endogenic fluids. This transect the ancestral Rio Grande, whose location shifted A. F. Fargo, Department Earth and Environmen- extends from the Colorado Plateau on the west to in response to silicic volcanism from the Jemez tal Science, New Mexico Institute of Mining the Great Plains on the east and includes springs Mountains to the west, mafic flows from the and Technology, Socorro, New Mexico 87801; along deep rift-bounding faults. This transect is Cerros del Rio volcanic field (~3.0–1.1 Ma) to the W. C. McIntosh and N. W. Dunbar, Department also strategically located at the intersection of east, as well as probable seismic activity within Earth and Environmental Science, New Mexico the Albuquerque and Socorro Basins, a structur- the rift. The mafic flows created a resistant table- Institute of Mining and Technology, Socorro, ally complex zone that appears to coincide with land that provided local knickpoints for streams New Mexico 87801 and New Mexico Bureau of longitudinal changes in the Rio Grande surface draining the Otowi headlands, allowing broad Geology and Mineral Resources, Socorro, New water as reported in previous research. washes to form adjacent to the master stream. Mexico 87801 Results indicate the interaction of three dis- In addition, continuing eruptive activity, occa- The history and chronology of the Minna Bluff tinct hydrochemical facies: the first is a Na-Cl/ sional landslides, earthquakes, and undercutting volcanic peninsula provides insight into past SO4 composition that consisted of the San Acacia of the ancestral Rio canyon formed ephemeral dynamics of the Ross Ice Sheet. Twenty-five sam- pools, Rio Salado Springs, and the Rio Salado. impoundments that may have temporarily raised ples of volcanic rock from different elevations on The second, with a mixed cation-HCO3 rich com- base level along particular reaches influencing Minna Bluff have been dated using 40Ar/39Ar position, consisted of the San Lorenzo Springs. rates of tributary drainage network development geochronology. When volcanoes interact with The third, with a Ca/Mg–Cl/SO4 composition, and affecting where large, episodic outflows of glacial ice the resulting lithofacies can provide consisted of Cibola and Milagro Springs. We sediment would have been deposited. useful information on ice thickness that can be interpret these results in light of other regional used to interpret ice-sheet history. Datable vol- ground water surveys and evaluate mixing mod- Poster Session 3—Hydrology, canic rocks that bracket obvious glacial uncon- els to explain the observed variations. Ongoing Hydrogeochemistry, Climate, and formities also provide information about glacial trace element analysis will allow for further test- Microbiology history. This information can be combined with ing of hydrologic mixing models. data from the ANDRILL marine core to help RED RIVER INCISION RECORDED IN determine ice-sheet chronology for the Miocene SUPERGENE JAROSITE, TAOS COUNTY, in the McMurdo Sound region. Geomicrobiology and Geochemical NEW MEXICO, K. E. Samuels, ksamuels@nmt. Prior K/Ar dating of the southeastern expo- Energy for Microbial Metabolism edu, A. R. Campbell, Department of Earth and sures at Minna Bluff yielded dates ranging from in CO2-rich Springs of the Tierra Amarilla Anticline, New Mexico Environmental Science, New Mexico Institute 11 to 7.26 Ma and suggested that the southern tip , B. Cron, [email protected], Department of Biol- of Mining and Technology, Socorro, New Mex- of the bluff represents the oldest eruptions. New 40Ar/39Ar results from sanidine and amphibole ogy, University of New Mexico, Albuquerque, ico 87801; V. W. Lueth, and L. Peters, New Mex- mineral separates and groundmass concentrates, New Mexico 87131; L. J. Crossey, Department ico Bureau of Geology and Mineral Resources, show older ages of 11.67 ± 0.19 Ma in the north- of Earth and Planetary Sciences, University New Mexico Institute of Mining and Technol- ern end of Minna Hook (the eastern end of the of New Mexico, Albuquerque, New Mexico ogy, Socorro, New Mexico 87801 50-km-long bluff) and the youngest age of 8.28 ± 87131; and D. Northup, Department of Biology, Supergene jarosite, a pyrite weathering prod- 0.17 Ma from one of the stratigraphically highest University of New Mexico, Albuquerque, New uct, preserved in ferricretes and weathered veins lava domes on Minna Hook. Mexico 87131

64 Ne w Me x i c o Ge o l o g y May 2008, Volume 30, Number 2 Deep-sea hydrothermal vents and volcanic envi- ASPECT RELATED MICROCLIMATE’S look for relationships in temporal changes of the ronments are a consequence of tectonic forces EFFECTS ON SOIL-FORMING PROCESS- measurements. This included comparisons of air and fluid circulation near Earth’s surface. Along ES, HILLSLOPE EVOLUTION, AND VEG- and ground water temperature and water chem- the Tierra Amarilla anticline there are CO2-rich ETATION DISTRIBUTION IN A SEMIAR- istries to precipitation and other physical vari- mound springs that are also a consequence of ID WATERSHED, SEVILLETA NATIONAL ables. The result is a baseline dataset to look at interactions between deeply sourced (“endo- WILDLIFE REFUGE, NEW MEXICO, D. Gau- further relationships during the growing season genic”) fluids and the extensional character of gler, [email protected], Department of Earth when ET is significant and water is manipulated Earth’s surface. and Planetary Sciences, University of New for anthropogenic uses. Archaeal communities similar to those found Mexico, Albuquerque, New Mexico 87131 in Yellowstone National Park are known to uti- North-south hillslope asymmetry is exhibited in lize chemical species within the Tierra Amarilla a drainage basin incised into the pediment and SINKHOLES IN SOUTHEAST NEW MEXI- anticline for metabolic processes. In this study associated alluvium of the Los Pinos Mountains. CO—PROFILING THE GEOCHEMICAL, we prepared oligotrophic media to culture Microclimate variations with aspect and slope HYDROLOGICAL AND MICROBIAL microorganisms from both water and iron and appear to be related to hillslope morphology, CHARACTER OF SINKS ALONG THE sulfide-rich muds at the Tierra Amarilla anti- and variations in soil development, weathering, PECOS RIVER AT BITTER LAKE Nation- cline. We also sampled the springs for gas and and vegetation cover may lead to differences al Wildlife Refuge, ROSWELL, New water chemistry and established an analytical in landscape evolution. To test this hypothesis, Mexico, Z. E. A. Premo, and L. J. Crossey, geochemistry dataset. This dataset provided us catenas are being examined at several stages Department of Earth and Planetary Sciences, with useful thermodynamic constraints used in a of hillslope evolution from initial incision to a University of New Mexico, Albuquerque, New geochemical computer code. The values from the mature hillslope. Here the types and rates of Mexico 87131 computer code were then used to build a com- weathering of the Permian limestone, sandstone, Bitter Lake National Wildlife Refuge in south- prehensive list of potential metabolic reactions. and mudstone of the Yeso and Abo Formations eastern New Mexico was established in 1937 We were able to predict energy available to fuel are apparently related to moisture availability. to preserve the habitat of migratory waterfowl specific fungal and bacterial species found at the North-facing slopes, covered by juniper savan- and to protect wetlands surrounding the Pecos Tierra Amarilla site. nah, are steeper and transport-limited with deep- River near Roswell, New Mexico. Such wet- There is a flora of microbial life in these springs, er weathering profiles in all bedrock types, and lands have developed around a series of playa and knowledge of the microbial bioenergetics in have more extensive soil development including lakes, water-filled sinkholes (sinks), and surface these systems is limited. By establishing how carbonate and gypsum accumulation. South- springs. These spring systems are threatened this location acts thermodynamically, we can facing slopes, covered by creosote desert shrub- by regional climatic conditions in addition to come one step closer to defining the relationship land, are divided into segments by outcropping direct anthropogenic influences such as ground between microbial and geochemical interactions resistant bedrock units that act as local base level water development. The goal of this project is to in extreme environments by providing perti- controls, with segments being either transport or characterize the water chemistry of sinks at the nent information that will help predict microbial weathering limited depending on facies. Investi- refuge and identify hydrologic pathways that growth parameters in other CO -rich springs. gations have suggested that feedbacks between maintain these sinks. In addition, these efforts 2 weathering, soil formation, vegetation cover, and will be used to supplement ongoing biologi- hydraulic properties have enhanced the differ- cal research activities at the New Mexico State SOIL GEOMORPHIC PATTERNS AND ences in slope morphology over time. University (ichthyology) and University of New GRASSLAND RESISTANCE AT THE JORNA- Mexico (entomology). In particular, this research DA BASIN LTER SITE, D. M. Rachal, D.Rachal@ will identify the presence of specific chemical nmsu.edu, H. C. Monger, Department of Plant Relationships Between Temporal components within the water that can be used and Environmental Sciences, New Mexico State Variations in Ground water Chem- as tracers to investigate ground water flow, pol- University, Las Cruces, New Mexico 88011; and istry and Micrometeorologi- lution implications, and sources of accumulated D. Peters, U.S. Department of Agriculture, Agri- cal Fluxes Along the Middle Rio toxins in biota tissues. cultural Research Service, Jornada Basin LTER, Grande of New Mexico, S. Teet, L. J. Water chemistry for a subset of approximate- Las Cruces, New Mexico 88011 Crossey, Department of Earth and Planetary ly 20 sinks throughout the northern portion of Sciences, University of New Mexico, Albu- the refuge is presented, and results are com- Geomorphic properties, such as elevation, slope querque, New Mexico 87131; J. Cleverly, and pared with existing datasets. Preliminary mea- gradient, and orientation, are fundamental ele- J. Thibault, Department of Biological Sciences, surements indicate pH ranges of 7.14–8.97 and ments of the landscape that play a large role University of New Mexico, Albuquerque, New conductivity ranges of 8.58–106.6 mS/cm; such in the persistence of desert grasslands. Micro- Mexico 87131 parameters can vary widely between sinks only climatic variations created by these landform meters apart. An additional component of this elements can control physical and chemical It is important to know the chemical properties of ground water, particularly when it is a prima- project involves developing procedures to moni- weathering rates of parent material. Topograph- ry source of consumed water as is the case in the tor the subsurface chemistry at high temporal ic location (e.g. run-on vs. run-off position) can Middle Rio Grande of New Mexico (MRG). Many resolution for extended time periods to assess control the redistribution of this weathered aspects of this unique system have been studied the system sensitivity to atmospheric and sea- material, which can influence the movement including depth, spatial, and even some tem- sonal changes. In order to investigate microbial of nutrients and sediments by wind and water poral variability. More needs to be understood, activity, sediment and water will be cultured throughout an ecosystem. Over time, the process however, about how the physical and chemical by inoculating microbial-specific media, as well of erosion and sedimentation differentiates the properties of ground water in the MRG change as filtering water to obtain DNA; the aim is to landscape into individual soil units that vary in on a temporal scale, particularly at high resolu- identify and isolate anaerobic microbial activity age, physical, and chemical composition. Upon tion as affected by exogenic factors. Factors such throughout the water column. Microbial com- these soil-geomorphic entities, isolated patches as evapotranspiration (ET) and irrigation may be munities are essential primary producers sup- of grasslands can be found in the Jornada Basin, affecting ground water chemistry diurnally but porting the complex and unique ecosystems that New Mexico. These grass patches are resistant cannot be quantified because there are little data have developed within individual sinks. against the transition from semiarid, perennial to look at for correlation on such time scales. grasslands to a shrub dominated ecosystem that For this study, measurements were made dur- began within the Jornada Basin 150 yrs ago. The ing baseline conditions (in winter months when survival of these remnant grasslands is strongly ET and irrigation for agriculture were not present) influenced by vegetation-soil-landform relation- of DO, conductivity, pH, and water temperature Publication of these abstracts was support- ships. Therefore, the soil-geomorphic properties for approximately one month each at three dif- ed in part by a grant from the New Mexico of a specific landscape can provide a stronghold ferent sites along the Rio Grande using a Sonde Geological Society Foundation. for grass species to resist and survive the det- 600 SLM (YSI) logger. These sites were chosen rimental effects of desertification, thus, produc- because they already have established 3-Dimen- ing the isolated grass patches that are observed sional Eddy Covariance systems that include today in the Jornada Basin. several meteorological monitoring instruments as well as some for soil and water table measure- ments. Then the water chemistry data were ana- lyzed and compared with the other site data to

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