Jornada Del Muerto Basin Research Articles

Mixed Geothermal and Shallow Meteoric Origin of Opal and Calcite Beds In Pliocene-Lower Pleistocene Axial-Fluvial Strata, Southern Rio Grande Rift, Rincon Hills, New Mexico, U.S.A

Abstract Exposed in upper Pliocene fluvial strata in the eastern Rincon Hills and adjacent Jornada del Muerto Basin, southern Rio Grande rift, New Mexico, USA, are five laterally continuous beds 0.2 to 1.0 m thick of opal-CT, which straddle the East Rincon Hills normal fault. Four of these opal beds change basinward over ~ 1 km or less to white, friable, lithofeldspathic sand with opal glaebules, and then to microcrystalline calcite. The opal and calcite generally replaced fine sand at shallow depths, although two beds locally precipitated from standing water. 87Sr/86Sr values (0.71301 to 0.71724) of the opal beds are consistent with precipitation from an advecting, high-temperature geothermal fluid that flowed through bedrock and/or from a high-temperature geothermal fluid derived from a deep-crustal source. Carbon and oxygen isotopic values (δ13CPDB = −7.1 to −0.6; δ18OPDB = −9.1 to −5.6) of the calcite beds lie between and overlap those of Paleozoic carbonate and Pliocene paleosol calcite, suggesting precipitation from a mixture of a high-temperature geothermal fluid that interacted with Paleozoic carbonates and shallow, meteoric groundwater, for which paleosol calcite is a proxy. The geothermal fluids are interpreted to have upwelled along the East Rincon Hills fault, flowed laterally at or just below the surface, and precipitated opal in response to rapid cooling and evaporation. Downflow precipitation of opal glaebules occurred as a result of decreasing silica concentrations and perhaps by mixing with shallow, meteoric groundwater, from which calcite precipitated, probably by CO2 degassing.

Geochemical indicators of interbasin groundwater flow within the southern Rio Grande Valley, southwestern USA

Increased groundwater withdrawals for the growing population in the Rio Grande Valley and likely alteration of recharge to local aquifers with climate change necessitates an understanding of the groundwater connection between the Jornada del Muerto Basin and the adjoining and more heavily used aquifer in the Mesilla Basin. Separating the Jornada and Mesilla aquifers is a buried bedrock high from Tertiary intrusions. This bedrock high or divide restricts and/or retards interbasin flow from the Jornada aquifer into the Mesilla aquifer. The potentiometric surface of the southern Jornada aquifer near part of the bedrock high indicates a flow direction away from the divide because of a previously identified damming effect, but a groundwater outlet from the southern Jornada aquifer is necessary to balance inputs from the overall Jornada aquifer. Differences in geochemical constituents (major ions, δD, δ18O, δ34S, and 87Sr/86Sr) indicate a deeper connection between the two aquifers through the Tertiary intrusions where Jornada water is geochemically altered because of a geothermal influence. Jornada groundwater likely is migrating through the bedrock high in deeper pathways formed by faults of the Jornada Fault Zone, in addition to Jornada water that overtops the bedrock high as previously identified as the only connection between the two aquifers. Increased groundwater withdrawals and lowering of the potentiometric surface of the Jornada aquifer may alter this contribution ratio with less overtopping of the bedrock high and a continued deeper flowpath contribution that could potentially increase salinity values in the Mesilla Basin near the divide.

Evaluation of mountain-front recharge estimation techniques for Southern New Mexico basins

Technically sound water management practices in arid to semi-arid regions require effective quantification of model input parameters. Mountain-front recharge is one of the most uncertain parameters in groundwater flow models due to the complexity of estimation. This paper evaluated three mountain-front recharge estimation techniques using a numerical model developed for the Southern Jornada Del Muerto Basin, New Mexico. Digital elevation model (DEM) and distributed precipitation maps were used to delineate recharge zones in the study area on geographic information system (GIS) platform. Statistical and residual parameters were used to assess the reliability of the calibrated recharge. An estimated annual recharge of about 3,360 enters the basin through ephemeral streams. Simulated heads from the three estimation techniques had approximately equal mean, with different variance. Analysis of variance on the simulated piezometric heads revealed that all the three empirical methods were consistent with the observed data. Waltemeyer equation proved to be more efficient in estimating mountain-front recharge as it gave the closest match between the observed and simulated piezometric heads and other basin-specific climatic characteristics. Key words: Mountain-front recharge, numerical model, Southern Jornada Del Muerto Basin, GIS.

Geoarchaeology of the Mockingbird Gap (Clovis) site, Jornada del Muerto, New Mexico

AbstractThe Mockingbird Gap site is one of the largest Clovis sites in the western United States, yet it remains poorly known after it was tested in 1966–1968. Surface collecting and mapping of the site revealed a dense accumulation of Clovis lithic debris stretching along Chupadera Draw, which drains into the Jornada del Muerto basin. We conducted archaeological testing and geoarchaeological coring to assess the stratigraphic integrity of the site and gain clues to the paleoenvironmental conditions during the Clovis occupation. The 1966–1968 excavations were in stratified Holocene eolian sand and thus that assemblage was from a disturbed content. An intact Clovis occupation was found elsewhere in the site, embedded in the upper few centimeters of a well‐developed buried Bt horizon formed in eolian sand, representing the regional Clovis landscape. Coring in Chupadera Draw revealed ∼11 m of fill spanning the past ∼11,000 14C years. The stratified deposits provide evidence of flowing and standing water on the floor of the draw during Clovis times, a likely inducement to settlement. © 2009 Wiley Periodicals, Inc.

Nonlinear biofluvial responses to vegetation change in a semiarid environment

The desertification of grassland communities in the Jornada del Muerto Basin, southern New Mexico, USA, has occurred in association with a series of geomorphic responses that have influenced the system of vegetation change. Rainfall simulation experiments indicate that the volume of runoff generated from basin surfaces and its ability to erode are greatly affected by the distribution of vegetation, which ultimately controls processes such as rainsplash erosion, soil infiltrability and crust development. Animal activities also influence rates of sediment movement from unvegetated surfaces by disrupting soil crusts and making loose sediment available for transportation by overland flow. Shrublands in the Jornada Basin have a patchier vegetation cover than grasslands, with vegetated areas (shrubs) being separated by unvegetated (intershrub) zones. The exposed intershrub surfaces are more vulnerable to erosion than the grass and shrub surfaces. Thus, water and sediment yields, calculated using rainfall simulation experiments, were higher for vegetated (shrub and grass) plots than they were for unvegetated (intershrub) plots. The runoff and erosion model, KINEROS2, predicts that at the base of a 100 m slope, shrubland surfaces shed seven times more runoff and 25 times more sediment than grassland surfaces. Evidence to support the prediction of higher rates of erosion in the shrubland can be found in the form of the extensive rill networks that are common in this community. The contraction of grasslands has been associated with elevated rates of erosion that have altered the morphology of the surface, lowering slopes between shrubs, and increasing the amplitude of the microtopography. Overall, the viability of the exposed soils for recolonization by grasses has been reduced, reinforcing the system of shrubland invasion and lending support to the use of state-and-transition models to describe ecologic responses to change within this environment. Combined, these results indicate that biophysical interactions in semiarid environments, such as the Jornada del Muerto Basin, are extremely complex and highlight the need for integrative investigations in these regions.

Characterization of shrub distribution using high spatial resolution remote sensing: Ecosystem implications for a former Chihuahuan Desert grassland

Patchiness is often considered a defining quality of ecosystems in arid and semiarid regions. The spatial distribution of vegetation patches and soil nutrients coupled with wind and water erosion as well as biotic processes are believed to have an influence on land degradation. A geostatistical measure of spatial “connectivity” is presented to directly measure the size of patches in the landscape from a raster data set. Connectivity is defined as the probability that adjacent pixels belong to the same type of patch. Connectivity allows the size distribution of erodible patches to be quantified from a remote sensing image or field measurement, or specified for the purposes of modeling. Applied to high-resolution remote sensing imagery in the Jornada del Muerto Basin in New Mexico, the spatial distribution of plants indicates the current state of grassland-to-shrubland transition in addition to processes of degradation in this former grassland. Shrub encroachment is clearly evident from decreased intershrub patch size in coppice dunes of 27.8 m relative to shrublands of 65.2 m and grassland spacing of 118.9 m. Shrub patches remain a consistent 2–4 m diameter regardless of the development of bush encroachment. A strong SW–NE duneland orientation correlates with the prevailing wind direction and suggests a strong aeolian control of surface geomorphology. With appropriate data sets and classification, potential applications of the connectivity method extend beyond vegetation dynamics, including mineralogy mapping, preserve planning, habitat fragmentation, pore spacing in surface hydrology, and microbial community dynamics.

A test of models of fluvial architecture and palaeosol development: Camp Rice Formation (Upper Pliocene‐Lower Pleistocene), southern Rio Grande rift, New Mexico, USA

AbstractNumerical, experimental and theoretical models of fluvial architecture and palaeosol development are tested with outcrops of Upper Pliocene‐Lower Pleistocene sediment in the southern Rio Grande rift, New Mexico. The sediment was deposited and subsequently exhumed in the Jornada del Muerto basin, a westward‐tilted half graben whose footwall corresponds to the Rincon Hills and San Diego Mountain fault blocks. The axial river, the ancestral Rio Grande, shared time between the Jornada del Muerto basin and the adjacent Corralitos basin. The ancestral Rio Grande entered the Jornada del Muerto basin via a gap between the footwall blocks, periodically flowing southward towards San Diego Mountain, or making a broad northward sweep into the northern fluvial salient towards the Rincon Hills fault block and unfaulted northern edge of the basin. Ten logged sections up to 35 m thick are correlated using the top of the formation (La Mesa surface), a 1·59 Ma pumice conglomerate, and a ground‐water carbonate/opal bed. Additionally, one of the sections is dated by reversal magnetostratigraphy. Consistent with the model of Bridge & Leeder (1979) and Bridge & Mackey (1993a), differential tilting of the Jornada del Muerto half graben resulted in sections directly adjacent to the faults that consist almost exclusively of multistorey channel sands/sandstones, whereas more distal sections contain a greater proportion of crevasse‐splay fine sand and overbank mudstone and calcic palaeosols. Along the axis of the northern fluvial salient, a northward decrease in channel/floodplain ratio, a decrease in channel recurrence interval from 171 kyr to 685 kyr, and an increase in the maturity of calcic palaeosols are consistent with southward tilt of the unfaulted northern edge of the basin. An upsection decrease in sediment accumulation rate in the northern fluvial salient from 0·036 mm/ yr to 0·017 mm/ yr corresponds to an increase in the ratio of channel/floodplain facies and in the number of multistorey channel sands/sandstones, and is consistent with the model of Bridge & Leeder (1979) in which avulsion frequency is independent of sediment accumulation rate. Stage II and III calcic palaeosols indicate 103−105 year of landscape stability and soil formation between periods of floodplain deposition in response not only to basin tilting but also because the ancestral Rio Grande had multiple paths within the Jornada del Muerto basin and shared time between the Corralitos and Jornada del Muerto basins.

Lizard community structure across a grassland – creosote bush ecotone in the Chihuahuan Desert

I investigated the distribution and abundance of lizard species (Aspidoscelis inornatus, Aspidoscelis tesselatus, Aspidoscelis tigris, Aspidoscelis uniparens, Cophosaurus texanus, Crotaphytus collaris, Eumeces obsoletus, Gambelia wislizenii, Holbrookia maculata, Phrynosoma cornutum, Sceloporus magister, and Uta stansburiana) across a desert grassland – creosote bush (Larrea tridentata) ecotone in Dona Ana County, New Mexico. The ecotonal area in the Jornada del Muerto basin has increased dramatically in the past 150 years because of the rapid spread of creosote bush. I asked four related questions: how large and where is the ecotone based on vegetative structure, and do lizard abundance and diversity change across the ecotone? Vegetation data were analyzed using discriminate function analysis to determine the extent of the ecotone. Changes in lizard abundance across the ecotone were analyzed by analysis of variance. During two summers, 677 individual lizards of 9 genera and 12 species were captured. Lizard abundance increased with increasing distance from the ecotone and was similar in grassland and creosote bush habitat. Grasslands had higher species richness than both the creosote bush and ecotone habitats. Grassland sites had greater habitat heterogeneity than did creosote bush sites. No ecotone specialist species were detected, and all common lizard species could be found in each habitat. Three potential explanations for decreased abundance in the ecotone are presented: (1) increased risk of predation, (2) decreased prey abundance, and (3) lack of species-specific microhabitat requisites.

Synclinal‐horst basins: examples from the southern Rio Grande rift and southern transition zone of southwestern New Mexico, USA

AbstractIn areas of broadly distributed extensional strain, the back‐tilted edges of a wider than normal horst block may create a synclinal‐horst basin. Three Neogene synclinal‐horst basins are described from the southern Rio Grande rift and southern Transition Zone of southwestern New Mexico, USA. The late Miocene–Quaternary Uvas Valley basin developed between two fault blocks that dip 6–8° toward one another. Containing a maximum of 200 m of sediment, the Uvas Valley basin has a nearly symmetrical distribution of sediment thickness and appears to have been hydrologically closed throughout its history. The Miocene Gila Wilderness synclinal‐horst basin is bordered on three sides by gently tilted (10°, 15°, 20°) fault blocks. Despite evidence of an axial drainage that may have exited the northern edge of the basin, 200–300 m of sediment accumulated in the basin, probably as a result of high sediment yields from the large, high‐relief catchments. The Jornada del Muerto synclinal‐horst basin is positioned between the east‐tilted Caballo and west‐tilted San Andres fault blocks. Despite uplift and probable tilting of the adjacent fault blocks in the latest Oligocene and Miocene time, sediment was transported off the horst and deposited in an adjacent basin to the south. Sediment only began to accumulate in the Jornada del Muerto basin in Pliocene and Quaternary time, when an east‐dipping normal fault along the axis of the syncline created a small half graben. Overall, synclinal‐horst basins are rare, because horsts wide enough to develop broad synclines are uncommon in extensional terrains. Synclinal‐horst basins may be most common along the margins of extensional terrains, where thicker, colder crust results in wider fault spacing.

Microbial and chemical characterization of a groundwater flow system in an intermontane basin of southern New Mexico, USA

Groundwater of the southern Jornada del Muerto Basin, an intermontane basin structure associated with the Rio Grande rift located in south-central New Mexico, USA, was analyzed chemically and microbially. A microbial phospholipid fatty acids (PLFA) analysis revealed a sparse microbial population consisting of relatively simple microorganisms with no major population changes along the flow system. A nucleic acid (DNA) analysis of the groundwater resulted in the identification of ten eubacterial and one archeal species. Chemical analyses revealed that sulfate along with calcium, magnesium, iron, and manganese is removed by about an order of magnitude in concentration from the recharge area to the discharge area. The removal of iron, manganese, magnesium, and to some extent calcium can be explained by oxidation reactions and the precipitation of dolomite. Sulfate and additional calcium are most likely removed by the precipitation of gypsum. Thiobacillus spp. are oxidizing metal sulfides that occur as subsurface sulfide mineral deposits to sulfuric acid, which subsequently reacts with calcium carbonate and water to precipitate gypsum. The presence of these sulfide deposits exposed to oxygenated water in the deep groundwater flow system significantly alters its chemical and bacteriological composition.

Potential growth and drought tolerance of eight desert grasses: lack of a trade-off?

Eight perennial C-4 grasses from the Jornada del Muerto Basin in southern New Mexico show five-fold differences in relative growth rates under well- watered conditions (RGRmax). In a controlled environment, we tested the hypothesis that there is an inverse relationship (trade-off) between RGRmax and the capacity of these species to tolerate drought. We examined both physiological (gas exchange) and morphological (biomass allocation, leaf properties) determinants of growth for these eight species under three steady-state drought treatments (none=control, moderate, and severe). When well watered, the grasses exhibited a large interspecific variation in growth, which was reflected in order-of-magnitude biomass differences after 5 weeks. The species had similar gas-exchange characteristics, but differed in all the measured allocation and morphological characteristics, namely tiller mass and number, root:shoot ratio, dry-matter content, and specific leaf area (SLA). Drought affected tillering, morphology, and allocation, and reduced growth by 50 and 68% (moderate and severe drought, respectively) compared to the well-watered controls. With the exception of SLA, none of these variables showed a significant species-by-treatment interaction. We calculated three indices of drought tolerance, defined as the ratio in final biomass between all the possible "dry"/"wet" treatment pairs: severe/moderate, moderate/control, and severe/control. We found no significant correlation between these drought tolerance indices, on the one hand, and three indices of growth potential (greenhouse RGRmax, final biomass in the control treatment, and final:initial biomass ratio in controls), on the other. Based on these controlled-environment results, we hypothesize that the commonly reported correlation between plant growth potential and drought tolerance in the field may in some cases be explained by differential effects of plants on soil-water content rather than by differences in species responses to drought.

Environmental controls on nitric oxide emission from northern Chihuahuan desert soils

A survey of nitric oxide (NO) emission from Chihuahuan desert soils found mean NO fluxes <0.1 ng NO-N cm−2h−1 during the dry season. These fluxes were at thelower end of the range reported for temperate grassland and woodlandecosystems. NO fluxes from wet or watered soils were higher(0.1–35 ng NO-N cm−2 h−1).Watering of black grama grassland soils produced an initial pulse of 12ng cm−2 h−1 (12-h after 1-cm watering)with high fluxes sustained over 4 days with repeated watering. Initialpulses from shrubland soils were lower (maximum 5 ngcm−2 h−1), and fluxes declined withrepeated watering. Repeated watering of creosotebush soils depleted thesoil NH 4 + pool, and NO emissions weredirectly related to soil NH 4 + concentrationsat the end of the experiment. In watered andNH 4 + -fertilized creosotebush soils, NO fluxeswere positively related to potential net nitrification rates.NH 4 + -fertilization boosted the initial NOpulse 15 times in the shrubland and 5 times in black grama grasslandrelative to watered controls. These experimental results point towardgreater substrate limitation in shrublands. In this desert basin, NOemission averaged 0.12 kg N ha−1 y−1in untreated soil and 0.76 kg N ha−1y−1 in watered soil. We multiplied these averages bythe distribution of grassland and shrubland vegetation within a58,600-ha area of the Jornada del Muerto basin to estimate regionallosses of 0.15–0.38 kg NO-N ha−1y−1 for this area of the Chihuahuan desert.

Techniques for Computer-Assisted Mapping of Rangeland Change

Management of grasslands subject to replacement by woody species requires an understanding of the scales and patterns of change and how to detect and express them. We used the Jornada del Muerto Basin of southern New Mexico as a case study, testing the suitability of Landsat Multi-Spectral Scanner (MSS) data for detecting vegetation changes. Cycles of drought and heavy grazing have apparently changed the once extensive grasslands of the upland Jornada and surrounding areas gradually into a patchwork of shrublands and relict grasslands. Integrated remote sensing and geographic information system (GIS) techniques can facilitate automated detection of these rangeland changes. A GIS was used to store and process two 4-band, co-registered multi-temporal Landsat MSS scenes collected in July 1983 and August 1992. Scene-to-scene radiometric calibration was performed using a regression technique. The data were then evaluated for changes 3 different ways using algorithms based on differences between the 'red' (chlorophyll absorption) bands for the 2 scenes; the Euclidean distances between the 'red' and 'near-infrared' bands for the 2 scenes; and a standardized principal components analysis using all 8 MSS bands. A threshold of 3 standard deviations above the mean was applied to each of the 3 resulting 'change' images to represent areas of extreme change. Correlations among these images ranged between 0.83 and 0.95. We conclude these techniques can identify successfully the patterns and extent of extreme change, and thus have potential value for management of our rangelands resources.

Effects of Plant Size on Photosynthesis and Water Relations in the Desert Shrub Prosopis glandulosa (Fabaceae)

The Jornada del Muerto basin of the Chihuahuan Desert of southern New Mexico, USA, has undergone a marked transition of plant communities. Shrubs such as mesquite (Prosopis glandulosa) have greatly increased or now dominate in areas that were previously dominated by perennial grasses. The replacement of grasses by shrubs requires an establishment phase where small shrubs must compete directly with similar-sized grass plants. This is followed by a phase in which large, established shrubs sequester nutrients and water within their biomass and alter soil resources directly under their canopy, creating “islands” of fertility. We hypothesized that these two phases were associated with shrubs having different physiological response capacities related to their age or size and the resource structure of the environment. As a corollary, we hypothesized that responses of small shrubs would be more tightly coupled to variation in soil moisture availability compared to large shrubs. To test these hypotheses, we studied gas exchange and water relations of small (establishing) and large (established) shrubs growing in the Jornada del Muerto as a function of varying soil moisture during the season. The small shrubs had greater net assimilation, stomatal conductance, transpiration, and xylem water potential than large shrubs following high summer rainfall in July, and highest seasonal soil moisture at 0.3 m. High rates of carbon assimilation and water use would be an advantage for small shrubs competing with grasses when shallow soil moisture was plentiful. Large shrubs had greater net assimilation and water-use efficiency, and lower xylem water potential than small shrubs following a dry period in September, when soil moisture at 0.3 m was lowest. Low xylem water potentials and high water-use efficiency would allow large shrubs to continue acquiring and conserving water as soil moisture is depleted. Although the study provides evidence of differences in physiological responses of different-sized shrubs, there was not support for the hypothesis that small shrubs are more closely coupled to variation in soil moisture availability than large shrubs. Small shrubs may actually be less coupled to soil moisture than large shrubs, and thus avoid conditions when continued transpiration could not be matched by equivalent water uptake.

Distribution of Land Snails of the San Andres and Organ Mountains, Southern New Mexico

Distribution of Land Snails of the San Andres and Organ Mountains, Southern New Mexico

Periodic Sedimentation and Soil Formation on an Alluvial‐Fan Piedmont in Southern New Mexico

AbstractGullies cut in alluvial‐fan piedmont deposits at the southern end of the Jornada del Muerto basin, New Mexico, reveal evidence of periodic sedimentation and soil formation. The gullies show a succession of four major sediments, each of which has a distinct soil, indicating that each period of sediment deposition was followed by a period of stability and soil formation. The two youngest sediments are restricted primarily to a broad drainageway position and have soils with relatively weak Bt and carbonate horizons. The next older sediment, buried in the broad drainageway, has a soil that has prominent textural B and carbonate horizons and that emerges at the land surface on either side of the drainageway. Towards the basin axis the sediments thin and there is mergence of the land‐surface soil with the oldest soil exposed in the gullies.The land‐surface soils overlie much older soils and in places are so thin that the buried soils must be considered in classification of the land‐surface soils. Gradual mergence zones of major sediments can conceal complexities greater than might be suggested by the generally smooth relief. Filling of channels in old sediments by younger sediments can cause prominent and abrupt soil changes not suggested by the smooth relief and uniform slope which crosses the soil boundaries. These phenomena are especially prevalent in and adjacent to drainageways and in areas of thinning of major sediments.

Age of the Rio Grande Valley in Southern New Mexico

On the basis of physiographic and lithologic evidence, previous workers in southern New Mexico believed an ancestral Rio Grande occupied a course through the Jornada del Muerto Basin, across La Mesa, and into northern Mexico, where the waters evaporated in the lake region. Subsequently, a lower river extended headward through the gap at El Paso, Texas, captured the upper stream, and diverted its flow to the Gulf of Mexico. A re-examination of the evidence in the southern Jornada Basin and of La Mesa shows that the postulation of the ancestral course of the river is highly conjectural and cannot be proved. Bordering the Rio Grande Valley are gravels containing a vertebrate fauna including Cuvieronius and Equus, which indicate a Kansan age. Three paleosols separate the gravels from overlying sediments on which the Jornada-La Mesa surface is formed. This surface must date from mid-Pleistocene. Distribution of gravel on La Mesa surface west of the present Rio Grande Valley but derived from rocks in the mountains east of the valley precludes existence of the valley in Jornada-La Mesa time. The Jornada surface occurs in an internally drained basin extending northward toward central New Mexico. The La Mesa surface was an internally drained basin extending southward into Chihuahua, Mexico. The Rio Grande now is entrenched northwest-southeast below the Jornada-La Mesa surface and is bordered by a stepped sequence of geomorphic surfaces, the youngest of which is less than years old by radiocarbon dating. Thus the river valley at a maximum is mid-Pleistocene in age and has been emplaced in the same general axial position since that time.