Zuni Mountains Research Articles

Culturally Modified Trees: Peeled and Scarred Ponderosa Pine Trees in the Zuni Mountains, New Mexico, USA

Modification of forest trees can occur from a variety of factors. Both cultural and natural processes can injure trees and many injuries can be dated dendrochronologically. Distinguishing between types of injuries, however, is important for understanding past human land-use practices and delineating different activities or processes that impact the forest. In the Zuni Mountains of New Mexico, USA, we have identified trees intentionally peeled for their cambial layer and unintentionally damaged trees whose scars resemble cambium-peeled trees. Both detailed attribute recording and dendrochronological dating were used to identify past exploitation of this ponderosa pine forest.

Late Cretaceous–Recent Low‐Temperature Cooling History and Tectonic Analysis of the Zuni Mountains, West‐Central New Mexico

AbstractLaramide tectonic models are testable with spatiotemporal constraints. The Colorado Plateau portion of the orogen, however, lacks detailed information on deformation timing. Herein, we analyze the Zuni Mountains, a Colorado Plateau Laramide arch, with apatite thermochronology, stratigraphic analysis, and thermal calculations to constrain and interpret its low‐temperature and tectonic history. Results show 2.9–3.6 km of pre‐exhumation burial by Late Cretaceous time that was sufficient to reset apatite (U‐Th)/He and apatite fission track dates after Pennsylvanian–Permian Ancestral Rocky Mountains exhumation. Low thermal conductivity of fine‐grained sediments was instrumental in facilitating sufficient temperatures to reset dates. Cooling histories of samples were structurally controlled. Forward and inverse models suggest ca. 80–45 Ma moderate to rapid cooling on the southwest flank and range crest of the arch, while the northeast flank displays 80–55 Ma slow cooling, very slow 55–20 Ma cooling and/or reheating, and post‐20 Ma rapid cooling. Northeast flank protracted cooling likely resulted from burial during backlimb tilting of the arch. Onset of exhumation was ca. 80 Ma, similar to 80–75 Ma onset of localized subsidence in San Juan Basin and 80–77 Ma onset of exhumation on the Nacimiento arch, but somewhat earlier than commonly considered for Colorado Plateau Laramide arches. In the regional context, our results support an easterly sweep of deformation driven by Farallon flat‐slab processes, and argues against prior suggestions for synchronous onset of Colorado Plateau Laramide deformation. Timing of post‐20 Ma cooling is most consistent with mantle‐driven epeirogenic uplift rather than Oligocene geotherm relaxation.

Influence of Desert Springs on Habitat of Endangered Zuni Bluehead Sucker (Catostomus discobolus yarrowi)

ABSTRACTLocated on the southeastern part of the Colorado Plateau, the Zuni Mountains are home to the endangered Zuni Bluehead Sucker (ZBS) (Catostomus discobolus yarrowi). A 4-year study was conducted on a low-flow (<80 cm3/s) hillslope spring and intermittent stream, that are home to one of the three remaining ZBS populations. Seasonal measurements of physical and hydrochemical parameters were used to estimate the contribution of groundwater to the stream and to identify geologic and hydrologic controls for the spring discharge. Seasonal concentrations and standard deviations (s) of Mg2+ were used to determine that the spring water (5.6 mg/L; s = 0.4) and surface water up-gradient from the spring input (10.7 mg/L; s = 11.2) is from different sources. Surface water down-gradient from the spring input maintain ZBS populations and is a mixture of spring water and up-gradient surface water. Mass solution mixing was used to determine spring water contributes up to 99 percent of the down-gradient water during drier seasons. Isotopes (δD, δ18O, 3H) indicate that the spring water has been recharged primarily from snowmelt within the last 70 years, while up-gradient surface water is seasonal runoff from rain and snowmelt. Continuous monitoring of dissolved oxygen (DO) mean concentrations (up-gradient = 1.6 mg/L and down-gradient = 5.7 mg/L) indicated that surface water up-gradient from the spring input are anoxic and unable to support ZBS. Surface water down-gradient from the spring input maintain appropriate DO concentrations due to perennially discharging spring waters re-aerating downstream habitats.

Eleventh-century shift in timber procurement areas for the great houses of Chaco Canyon

An enduring mystery from the great houses of Chaco Canyon is the origin of more than 240,000 construction timbers. We evaluate probable timber procurement areas for seven great houses by applying tree-ring width-based sourcing to a set of 170 timbers. To our knowledge, this is the first use of tree rings to assess timber origins in the southwestern United States. We found that the Chuska and Zuni Mountains (>75 km distant) were the most likely sources, accounting for 70% of timbers. Most notably, procurement areas changed through time. Before 1020 Common Era (CE) nearly all timbers originated from the Zunis (a previously unrecognized source), but by 1060 CE the Chuskas eclipsed the Zuni area in total wood imports. This shift occurred at the onset of Chaco florescence in the 11th century, a time with substantial expansion of existing great houses and the addition of seven new great houses in the Chaco Core area. It also coincides with the proliferation of Chuskan stone tools and pottery in the archaeological record of Chaco Canyon, further underscoring the link between land use and occupation in the Chuska area and the peak of great house construction. Our findings, based on the most temporally specific and replicated evidence of Chacoan resource procurement obtained to date, corroborate the long-standing but recently challenged interpretation that large numbers of timbers were harvested and transported from distant mountain ranges to build the great houses at Chaco Canyon.

Climatic influences on fire regimes in ponderosa pine forests of the Zuni Mountains, NM, USA

We characterized fire history and examined climate–fire relationships in dry ponderosa pine (Pinus ponderosa) forests in the Zuni Mountains of northwestern New Mexico. Our findings indicate that the historical wildfire regime for the study area was typified by high-frequency, low-severity surface fires. Climate–wildfire relationships were assessed using both Superposed Epoch Analysis (SEA) and Bivariate Event Analysis (BEA). SEA revealed that interannual variability of the El Niño–Southern Oscillation (ENSO) and the Palmer Drought Severity Index (PDSI) was a strong driver of widespread wildfires; wetter conditions often occurred one to two years prior to fire and were followed by drought during the fire year. BEA revealed statistically significant relationships only in the case of extreme PDSI events and widespread wildfire in the year of fire (t=0). No relationship was found between either the Pacific Decadal Oscillation (PDO) or the Atlantic Multidecadal Oscillation (AMO) and widespread fire occurrence, signifying that shorter-term (i.e. interannual) oscillations between wet and dry conditions, rather than longer-term climatic variability, were historically most conducive to fire. Contextualizing these findings under ongoing climate and land-use change is challenging. Full restoration to historical conditions may be neither possible nor desired, but targeted efforts to promote a frequent, low-severity wildfire regime are generally consistent with our understanding of historical fire activity in this forest type and may foster ecological, economic, and/or societal goals.

Climate-growth relationships for Rocky Mountain juniper (Juniperus scopulorum Sarg.) on the volcanic badlands of western New Mexico, USA

We sampled Rocky Mountain junipers (RMJ) to produce a multi-century tree-ring chronology from a relict lava flow, the Paxton Springs Malpais (PAX), in the Zuni Mountains of western New Mexico. Our objective was to assess crossdating potential for RMJ growing on the volcanic badlands of the region, investigate potential relationships between climate and RMJ growth, and investigate temporal variability in relationships identified between climate and RMJ growing at our site. We hypothesized that, similar to other drought stressed-conifers growing on the lava flows, RMJ responds to climate factors that influence and indicate moisture availability. We found a high average mean sensitivity value (0.53), which indicated the PAX chronology exhibited enough annual variability to capture fluctuations in environmental conditions. The average interseries correlation (0.74) indicated confident crossdating and a significant association of annual growth among trees within the stand. The positive correlation between the PAX chronology and total precipitation for the local water year was significant (r=0.53; P<0.001). Significant positive correlations also were identified between monthly PDSI, monthly total precipitation, and RMJ radial growth. Analyses of temporal stability indicated that the positive relationship between RMJ growth at the PAX site and monthly PDSI was the most stable relationship during the period of analysis (1895–2007). More importantly, we identified a unique inverse relationship between radial growth and monthly mean temperature during periods of the preceding year and current growing year, the first such finding of a strong temperature response for a low-mid elevation tree species in the American Southwest. Our results confirm that RMJ samples collected on the Paxton Springs Malpais are sensitive to climate factors that affect moisture availability, further suggesting that RMJ may be suitable for use in dendroclimatic research at additional locations across the broad distribution of the species.

CAMBIUM-PEELED TREES IN THE ZUNI MOUNTAINS, NEW MEXICO

Cambium-peeled trees are relatively common in ponderosa pine forests of the Intermountain West. Found from British Columbia to southern New Mexico, cambium-peeled trees have been interpreted as (a) a response to famine conditions related to climatic variations, (b) a response to conflict-related food shortages and scheduling issues, (c) a sweet or delicacy, and (d) a medicinal product used to treat various internal and external ailments. This paper uses dendrochronology, and ethnohistory to examine three spatially discrete groups of peeled trees in the Zuni Mountains of New Mexico in terms of their relationships to climatic variability, conflict and cultural practices.

Magnetostratigraphy of the Upper Triassic Chinle Group of New Mexico: Implications for regional and global correlations among Upper Triassic sequences

A magnetic polarity zonation for the Upper Triassic Chinle Group in the Chama Basin, north-central New Mexico (United States), supplemented by polarity data from eastern and west-central New Mexico (Mesa Redonda and Zuni Mountains, respectively), provides the most complete and continuous magnetic polarity chronology for the Late Triassic of the American Southwest yet available. Most of the Chinle Group sequence is composed of hematitic mudrocks that typically carry a well-defined, well-grouped magnetization (residing in both pigmentary and detrital hematite), with laboratory unblocking temperatures as high as 680 °C. Demagnetization experiments isolate magnetizations of south- or north-seeking declination and shallow inclination, which are interpreted as early acquired, Late Triassic magnetizations. Our proposed polarity correlations, coupled with biostratigraphic observations and recent U-Pb age determinations on detrital zircon–bearing strata in the Chinle Group in western New Mexico, West Texas, and Arizona, indicate that deposition of Chinle strata likely spanned a much shorter time span than previously considered. If this interpretation is correct, the Chinle Group can be correlated with only part of the Newark Supergroup or the Upper Triassic Tethyan sections. On a local scale, lower Chinle strata in the Chama Basin are significantly older than the Bluewater Creek Formation in western New Mexico, and the base of the Poleo Formation represents a disconformity of >13 m.y. duration. Magnetic polarity chronologies from upper Chinle strata in New Mexico and Utah suggest that strata considered to be part of the Rock Point Formation in north-central New Mexico are not time equivalent to type Rock Point strata in Utah or to the Redonda Formation of eastern New Mexico.

New Distributional Records of the Red Squirrel (Tamiasciurus hudsonicus) in Western New Mexico and Evidence for Its Extirpation from the Zuni Mountains

In the American Southwest, the red squirrel (Tamiasciurus hudsonicus) occurs as disjunct populations in coniferous forests on mountaintops. There is a paucity of information concerning the species' distribution and habitat in western New Mexico. I report new records that document and verify the occurrence of red squirrels in additional montane areas in west central New Mexico, including the Mangas Mountains, Canovas Rim, Turner Mountain, Tularosa Mountains, Elk Mountains, Bearwallow Mountain, and Pinos Altos Mountains. I also report observations of red squirrels from an atypical habitat—low-elevation riparian forests. These new records suggest that the geographic distribution of the species in west central New Mexico is broader than indicated by existing records. However, I also document the apparent extirpation of red squirrels from the Zuni Mountains in northwestern New Mexico. The red squirrel is one of several avian and mammalian species associated with mixed coniferous forests that have become extirpated in this mountain range.

Revisions to stratigraphic nomenclature of the Upper Triassic Chinle Group in New Mexico: New insights from geologic mapping, sedimentology, and magnetostratigraphic/paleomagnetic data

Upper Triassic strata, termed the Chinle Formation or Group, reveal a complex sedimentologic history, which has led to numerous modifications to the lithostratigraphic nomenclature for this unit. Recent revisions to Chinle nomenclature in New Mexico are based on local stratigraphic section inspection. The utility of some stratigraphic subdivisions, especially at formation rank, are problematic when mapping units away from type areas. New magnetostratigraphic records for the Chinle Group, as well as 1:24,000-scale mapping, stratigraphic section logs, and sedimentologic analyses support the following revisions to current nomenclature of the Chinle: (1) formally raising Chinle strata to group status in New Mexico; (2) abandoning the term Zuni Mountains Formation for lower Chinle strata in the Chama Basin; (3) including the lower member of the Salitral Formation in the Shinarump Formation; and (4) reassigning strata termed Rock Point Formation in the Chama Basin to the Moenave Formation. Sedimentologic and basin-analysis interpretations utilized in earlier studies of the Chinle should be resurrected. The revised stratigraphic nomenclature for the Chinle Group and sedimentologic analyses, both old and new, greatly expands our understanding of depositional changes in the Chinle Basin of northern New Mexico. The trunk stream for Chinle deposition in New Mexico coursed westward through the site of the modern Sierra Nacimiento of north-central New Mexico during Shinarump time (?late Carnian or early Norian), then moved northward to flow to the west in the area of the modern Chama Basin. In addition, north-central New Mexico was probably a topographic high during the time of Owl Rock and Rock Point deposition in the late Norian, and thus no uppermost Triassic (late Norian to early Rhaetian) strata were deposited in the area of the modern Chama Basin.

Mark–Recapture and DNA Fingerprinting Data Reveal High Breeding-Site Fidelity, Low Natal Philopatry, and Low Levels of Genetic Population Differentiation in Flammulated Owls (Otus Flammeolus)

AbstractOver a seven-year period, we used mark-recapture in a population of Flammulated Owls (Otus flammeolus) in the Zuni Mountains, New Mexico, to estimate adult breeding-site fidelity, mate fidelity, natal philopatry, and dispersal distances. We also used DNA fingerprinting to examine the genetic population structure of Flammulated Owls among four mountain ranges in New Mexico and one range in Utah. Mark-recapture revealed that adults are site-faithful and tend to maintain pair bonds between years, whereas juveniles show little natal philopatry. DNA fingerprinting revealed very low differentiation among populations, even between the New Mexico and Utah ranges, with population subdivision (FST) estimates ranging from 0.00 to 0.04. Heterozygosity values were high within each mountain range and, together with the low FST values, suggest that this Neotropical migrant may have long-distance natal dispersal and frequent intermountain dispersal.Datos de Marcado-Recaptura y Huellas Dactilares de ADN Revelan Alta Fidelidad a los Sitios de Cría, Baja Filopatría Natal y Bajos Niveles de Diferenciación Genética Poblacional en Otus flammeolus

MARK–RECAPTURE AND DNA FINGERPRINTING DATA REVEAL HIGH BREEDING-SITE FIDELITY, LOW NATAL PHILOPATRY, AND LOW LEVELS OF GENETIC POPULATION DIFFERENTIATION IN FLAMMULATED OWLS (OTUS FLAMMEOLUS)

Abstract Over a seven-year period, we used mark-recapture in a population of Flammulated Owls (Otus flammeolus) in the Zuni Mountains, New Mexico, to estimate adult breeding-site fidelity, mate fidelity, natal philopatry, and dispersal distances. We also used DNA fingerprinting to examine the genetic population structure of Flammulated Owls among four mountain ranges in New Mexico and one range in Utah. Mark-recapture revealed that adults are site-faithful and tend to maintain pair bonds between years, whereas juveniles show little natal philopatry. DNA fingerprinting revealed very low differentiation among populations, even between the New Mexico and Utah ranges, with population subdivision (FST) estimates ranging from 0.00 to 0.04. Heterozygosity values were high within each mountain range and, together with the low FST values, suggest that this Neotropical migrant may have long-distance natal dispersal and frequent intermountain dispersal. Datos de Marcado-Recaptura y Huellas Dactilares de ADN Revelan ...

An Interview with Simon Ortiz: July 14, 1988

SIMON ORTIZ: My family comes from the Acoma Pueblo reservation west of Albuquerque and, specifically, at McCartys on the New Mexico state maps, right off the Interstate 40. DAVID DUNAWAY: Did you grow up in Acoma? SO: I grew up in the Acoma Pueblo community, at McCartys. McCartys is one of the villages, the other village is Acomita, and other additional small settlements at Anzac and some newer ones. I grew up there for the first twenty years of my life. DD: So what was McCartys and the Acoma community like in the '40s and '50s? SO: It was the war, World War II, of course, and the life there was sort of on the edge of something new happening. The war was going on, I remember that there were young men who were uniform, going off somewhere, to California, wherever that was, and there were trains passing on the railroad, which runs about a mile north of my mother's house, and there were always these war things going up and down, west and east, and things happening like that. Acoma and McCartys, the little village, was very small at that time, and it didn't seem to be any more world out there except what was passing through. It was a very small community and I grew up within the community which was family, clan, grandparents, mother, and father. Although, obviously, changes that had been taking place for many, many decades and in the past two hundred or so years—three hundred or so years—was very much impressioned upon me as a [End Page 12] child of the 1940s. There was something going on, mysterious, and, of course, somewhat fearful. I found that when I started school that this world that was outside of Acoma and McCartys was so different, because most of that world and the exposure that I had to it was through reading—what I read, anyway, in the pages in the schoolbooks—was not really the Acoma and the Indian world in general. It was always some white-picket-fence in the West, or perhaps in California. When I was very young, things were changing so fast. The atomic bomb was exploded right at the beginning of my life. I was born in 1941, right at the beginning of that war. And in 1945 and the changes that were wrought by the war, and especially the bomb, you know, are a part of the history that I was living. I didn't really know it, of course, as a child, just that it was happening. I think that the changes were exemplified by school, by the railroad, and the men, leaving. My father was a railroad worker. I didn't learn any English until I went to school at McCartys's day school, which was then a BIA federal school, when I was six, seven years old. DD: Was it a rural environment? SO: Very much so. Pueblo Indian people traditionally are agricultural people, cultivating the land with the traditional crops of corn, chile, pumpkin, beans, squash, those kinds of things. Bottom lands along the Rio de San Jose, which originates in the Zuni Mountains, were used for the growing of these crops, and then dry-farming in the Acoma valley, which is twelve more miles to the south, which is the traditional home—mother home site—of the Acoma people. I was born actually at the old Albuquerque Indian Hospital, here, in Albuquerque, and from there on I lived at home until I was about nineteen, when I went away to school—college—for the first time. In a couple of those years, because my father was a railroad worker for the Santa Fe Railroad, we lived in California, I think, when I was very young, when I was a baby. And then later on, when I was in the fifth grade, I remember, we went...

Geochemistry of southwestern New Mexico fluorite occurrences implications for precious metals exploration in fluorite-bearing systems

Fluorite-bearing Cu–Au, Ag–Au, and Ag–Pb–Zn deposits comprise a geologically and genetically varied group of mineral deposits in southwestern New Mexico. Additionally, several small to moderate tonnage former fluorite orebodies and numerous non-economic fluorite occurrences are distributed throughout much of New Mexico, western Texas, and northern Sonora, Mexico. We differentiate fluorite-bearing deposit types utilizing variations in fluorite geochemistry. Several types of data were collected by fluid inclusion microthermometry, δD and δ 18O analysis of inclusion fluids, and trace element analysis of fluorite separates. Fluid inclusion microthermometry indicates that fluorite in most of the veins formed from low salinity (0–7 eq. wt.% NaCl) fluids at temperatures between 100° and 220°C. A small number of vein and replacement deposits hosted by limestone or granite, including the Hansonburg Mississippi Valley Type (MVT) deposit, and the Zuni Mountains deposits, formed at similar temperatures, but from moderately saline (10–20 eq. wt.% NaCl) fluids. Magmatic fluids (>600°C, 80 eq. wt.% NaCl), are trapped in fluorite veins in the Capitan pluton. δD and δ 18O values of inclusion fluids range, respectively, from −108 to −27‰ and from −9.9 to 7.3‰ relative to SMOW. Horizontal to subhorizontal trends in δD versus δ 18O space suggest that variably-exchanged meteoric waters were responsible for fluorite deposition in most deposits. Trace elements show a broad range in concentration from tenths to hundreds of parts per million. The sediment-hosted fluorites in this study tend to have low ΣREE concentrations relative to fluorite hosted by igneous rocks. Limestone-hosted fluorites associated with felsic intrusive rocks have high ΣREE concentrations relative to all other sediment-hosted fluorites. Signatures indicative of precious metals mineralization are present in low-salinity epithermal systems containing Au and/or Ag. These are characterized by small and/or isolated ranges in Sr concentrations, Sc/Eu ratios, (Tb/Yb) n ratios, and Eu anomalies. Two apparently barren fluorospar districts in southwestern New Mexico contain fluorite with signatures indicative of precious metals mineralization and, therefore, it is suggested that precious metals mineralization may also be present within these districts.

Facies and age of the Oso Ridge Member (new), Abo Formation, Zuni Mountains, New Mexico

Facies and age of the Oso Ridge Member (new), Abo Formation, Zuni Mountains, New Mexico

Stream Geomorphology: Effects on Periphyton Standing Crop and Primary Production

Anthropogenic changes in stream geomorphology have reduced the capacity of many North American streams to trap and retain sediments and organic matter. Significant losses of retentive structures from many small streams have resulted from beaver trapping. We compared algal standing crops and rates of primary production in two adjacent streams in the Zuni Mountains of New Mexico. Castor Creek has been worked by beaver and is a complex, highly retentive system with an extensive floodplain and accumulations of organic debris. Sawmill Creek is moderately incised, free of large organic debris, and poorly retentive. Clay tiles introduced into Castor Creek had average chlorophyll a standing crops 3-9× greater than Sawmill Creek (54.8-257.8 vs. 18.4-44.9 mg/m²). Chlorophyll a on natural substrates averaged 11× greater in Castor Creek than in Sawmill Creek (1679.4 vs. 154.2 mg/m²). Average standing crop of chlorophyll a per 250 m reach was 136× greater in Castor Creek than in Sawmill Creek due to its greater surface area (12.4×) and greater standing crop (11×). Extensive filamentous algal mats and the macro-alga Nitella gracilis in Castor Creek's beaver ponds exhibited the highest rates of primary production (85 mg C m^-2 hr^-1) while epilithic samples from both streams were similar (16.6 and 21.2 mg C m^-2 hr^-1 for Castor and Sawmill Creeks respectively). Nutrient amendment experiments revealed that both streams were nitrogen limited. Sediment samples taken in 1989 showed Castor Creek had 25× more dissolved NH₄ in the upper 5 cm of sediment than Sawmill Creek (1242 vs. 50 μg/L). We suggest that higher algal production in Castor Creek is linked to greater nutrient availability at the sediment/water interface due to greater retention and processing of organic matter in the hyporheic zone.

Nest-Site Preferences of Flammulated Owls in Western New Mexico

We studied nest-site preferences of Flammulated Owls (Otus flammeolus) in the Zuni Mountains of western New Mexico and used multivariate analyses of the nest cavity, nest tree, and surrounding woody vegetation to ask if and then how the birds select nest sites. Significantly reduced variance in used compared to unused sites for both cavity/nest-tree and vegetation data indicates that the used sites are a nonrandom subset of the source pool (i.e., the birds are selective). Preferred cavities are modal in the source pool, but preferred vegetation is characterized by low shrub density, high canopy height, and high importance of mature Pinus edulis. Preferred vegetation characteristics appear more limited than preferred cavity/nest-tree characteristics. Nest sites have fewer shrubs in front of than behind the cavity entrance. This is consistent with the species' habit of flying at shrub level upon approaching and leaving the nest. The suggestion that Flammulated Owls have increased in abundance with increasing vegetative density is not supported.

Taxonomic Relationships of the Zuni Mountain Sucker, Catostomus discobolus yarrowi

Catostomus discobolus yarrowi of the Little Colorado River drainage in New Mexico and Arizona is variable, populations morphologially and biochem­ ically intermediate between C. discobolus of the Colorado drainage and C. plebeius of the Rio Grande drainage. Specimens of C. yarrowi from the headwaters of the Little Colorado in the Zuni Mountains, New Mexico, are especially similar to populations of C. plebeius from just across the continental divide. Downstream populations are more like C. discobolus. Morphological and biochemical charac­ ters show slightly different trends among samples, but the patterns are consistent the hypothesis that a late Pleistocene stream capture resulted in introgres­ sion of C. plebeius characters into C. discobolus. I N 1874, E. D. Cope described Minomus jar­ rovii from the Zuni River headwaters of the Little Colorado River drainage in New Mexico, based on specimens 9 dorsal fin rays and the lower jaw with acute cartilaginous edge, regularly convex forwards. The types (USNM 15783) were collected by H. W. Hen­ shaw in 1873. (Cope gave the type locality as Provo, Utah, but Cope and Yarrow (1875) cor­ rected it to the Zuni River, New Mexico.) Fow­ ler (1913) referred to specimens from the same drainage, at Fort Wingate and Nutria, New Mexico, as Pantosteus plebeius, a species the above characters, living in the Rio Grande drainage. The populations were rediscovered in other Zuni tributaries by W. J. Koster: the Rio Pescado in 1948 and Nutria Creek in 1960. Smith (1966) showed that the Zuni River

Potassium, uranium, thorium radiogenic heat contribution to heat flow in the precambrian and younger silicic rocks of the Zuni and Florida mountains, New Mexico (U.S.A.)

High heat flow in the Zuni Mountains, New Mexico, U.S.A., has been explained by the possible presence of a buried felsic pluton. Alternately, high K, U, Th abundances have been proposed to account for part of the high heat flow. The mean radiogenic heat contribution for 60 samples of Precambrian core rocks is 7.23 μcal/gm-yr, which is slightly higher than the average for western U.S.A. granitic rocks and significantly higher than the average for continental “crust”; hence, the K, U, Th radiogenic contribution from Precambrian rocks to the overall heat flow is significant. Radiogenic K, U, Th heat for 32 samples for the Florida Mountains, New Mexico, U.S.A., yields a lower mean of 5.46 μcal/gm-yr. This value is somewhat anomalous in that the predominantly syenitic rocks commonly yield higher values. Furthermore, heat flow is higher in areas distant from the Floridas and the radiogenic heat contribution is considered small.

Uranium and Thorium Abundances, Whole Rock Chemistry and Trace Element Chemistry, Zuni Mountains, New Mexico

The uranium and thorium abundances in the Precambrian silicic core rocks of the Zuni Mountains have been determined by delayed neutron activation analysis. The average uranium content of 57 surface and drill core samples is 3.75 ppm, and the average thorium content of 25 samples is 17.13 ppm. The Th/U ratio for 25 samples is 4.5 5, which is slightly higher than the range of 3.7-4.0 reported for many granitic rocks. The uranium in the Zuni Mountains has, in part, been redistributed, and significant amounts may have been removed by weathering or other processes. Rare earth element distribution patterns, positive U vs K20 correlation, and high U content in surface samples suggest local redistribution was significant. No data support the core rocks of the Zuni Mountains as a large potential in situ uranium resource.