Colorado Plateau

To assess how elements leach from several types of coal combustion products (CCPs) and to better understand possible risks from CCP use or disposal, coal ashes were sampled from two bituminous-coal-fired power plants. One plant located in Ohio burns high-sulfur (about 3.9%) Upper Pennsylvanian Pittsburgh coal from the Monongahela Group of the Central Appalachian Basin; the other in New Mexico burns lowsulfur (about 0.76%) Upper Cretaceous Fruitland Formation coal from the San Juan Basin, Colorado Plateau. The sampled CCPs from the Ohio plant were bottom ash (BA), economizer fly ash (EFA), and fly ash (FA); the sampled CCPs from the New Mexico plant were BA, mixed FA/EFA, FA, and cyclone-separated coarse and fine fractions of a FA/EFA and FA blend. Subsamples of each ash were leached using the long-term leaching (60-day duration) component of the synthetic groundwater leaching procedure (SGLP) or the toxicity characteristic leaching procedure (TCLP, 18-hour duration). These ashes were all alkaline. Leachate concentrations and leachabilities of the elements from the CCPs were similar between corresponding CCP types (BA, EFA, and FA) from each plant. The leachabilities of most elements were lowest in BA (least leachable) and increased from EFA to FA (most leachable). Ca and Sr were leached more from EFA than from either BA or FA. Leachability of most elements also increased as FA particle size decreased, possibly due in part to increasing specific surface areas. Several oxyanion-forming elements (As, Mo, Se, U, and V) leached more under SGLP than under TCLP; the opposite was true for most other elements analyzed.

Understanding the prehistoric and historic dynamics of pinon-juniper woodland requires knowledge of the seed dispersal mechanisms and seedling establishment requirements of the tree species. Here, the types and effectiven-ess of the different seed dispersers and the environmental requirements for seedling establishment are compared and contrasted for the various pinon and juniper species within the woodlands. The importance of longdistance vs. short-distance dispersal and the roles of ecotones and disturbance in woodland dynamics are discussed. Recommendations for future research are given.

Rock inscriptions containing both names and calendar dates provide place-specific data on travels of explorers, if those inscriptions are truly authentic. We exemplify here a new strategy for determining the authenticity of inscriptions in arid environments in two case studies. One is an inscription purportedly created during the Marcos de Niza expedition of 1539 through Arizona. The other might have been made by the Dominguez-Escalante expedition of 1776 through the Colorado Plateau and Great Basin. The rock inscription in Phoenix, Arizona, "Fr Marcos de Niza corona todo el nuebo Mexico a su costa ano de 1539," is likely not authentic. Although the Marcos de Niza petroglyph was manufactured before the use of leaded gasoline about 1922, it was made after the Little Ice Age ended in the mid-nineteenth century. In contrast, the engraving "Paso Por Aqui-Año 1776" near Lake Powell's Padre Bay in Glen Canyon National Recreation Area has a lead profile indicating that the engraving predates twentieth-century pollution and also contains a Little Ice Age signal, evidence that the engraving is likely authentic. Nearby graffiti and natural weathering often endangers rock inscriptions, necessitating conservation efforts of authentic engravings. Conservation efforts to protect the delicate condition of the Lake Powell engraving are justified by these findings. In contrast, unnecessary expenditures and effort can result from work on engravings that are not authentic.

full citation: Ford, R.L., Gillman, S.J., Wilkins, D.E., Clement, W.P., and Nicoll, K. 2010. Geology and Geomorphology of Coral Pink Sand Dunes State Park, Utah. In Anderson, P.B.; Chidsey, T.C. and Sprinkel, D.A. (Eds) Geology of Utah's Parks and Monuments, Utah Geological Association Publication 28, 3rd Edition, Bryce Canyon Natural History Association and Utah Geological Association. p. 379-406.

Coral Pink Sand Dunes State Park, located in southwestern Kane County, Utah, contains a variety of geologic features including one of the largest areas of freely migrating dunes in the Colorado Plateau. The semiarid climate, strong prevailing southerly winds, sparse vegetation, and abundant supply of sand-sized sediment make this area susceptible to eo-lian processes. Picturesque exposures of Jurassic rocks are present within the park. The stratigraphic sequence ranges from the Tri-assic-Jurassic Moenave Formation to the Middle Jurassic Carmel Formation. The most widespread bedrock unit exposed within the park is the Navajo Sandstone (Lower Jurassic). The Navajo Sandstone is also widely exposed across the Moccasin Terrace southwest of the park and is the most likely source for the sand that comprises the dune field. The " coral pink " color of the dune sand is the result of iron-oxide stains on the surface of the sand grains inherited from the source sandstones. Migrating dunes, whose morphology is primarily a function of wind characteristics, include transverse ridges, barchanoid ridges, and a solitary star dune. Dunes influenced or impeded by topographic obstacles or vegetation include climbing dunes, echo dunes, parabolic dunes, vegetated linear dunes, and nebkhas. We divide the dune field into major geomorphic units based on the dominant dune type. A largely stabilized (vegetated) sand sheet and partially stabilized, poorly organized dunes are present at the southern (upwind) end of the dune field. The active core of the dune field contains transverse ridges and barchanoid ridges. Barchanoid ridges at the northern (downwind) end of the active core grade into climbing dunes that ramp up the bedrock escarpment associated with the Sevier fault. The climbing dunes in turn grade into large parabolic dunes that dominate the downwind end of the dune field. Coral Pink Sand Dunes lies within the structural transition zone between the Great Basin section of the Basin and Range province to the west, and the core of the Colorado Plateau to the east. The north-south-trending Sevier fault cuts through the length of the park. The fault trace is marked by a west-facing bedrock escarpment that divides the park into two topographic units (a forested plateau to the east and a relatively low-lying valley floor to the west) and acts as a major control over the accumulation of sand within the dune field. Important events recorded in the geologic features of the park include the Triassic and Jurassic depositional history of the Glen Canyon Group, the Cretaceous to Cenozoic structural history of the Colorado Plateau, and the late Holocene history of the active dunes. Optically stimulated luminescence dates from the active core of the dune field indicate that Holocene eolian deposition began at least 4,000 years ago. Radiocarbon dating of organic materials from an exhumed soil surface suggests a period of landscape stability approximately 500-200 years ago, coincident with the Little Ice Age. Den-drochronologic data from the ponderosa pines in the park, along with historic photographs, indicate the dune field has experienced alternating wet periods and drought since the end of the Little Ice Age, which have influenced vegetation coverage and dune activity in the area. 379

The Fremont, a Formative culture located in the Eastern Great Basin and Colorado Plateau, have been primarily studied from an ecological perspective. This research addresses issues that are not ecological, the organization of production and exchange of ceramic vessels. Following criteria suggested by Brown et al. (1990), I argue that the following need to be addressed prior to a useful discussion of intergroup trade: the source of the raw materials of the exchanged objects, the associated pattern of distribution, the relative value of the objects, and their context of manufacture, use, and consumption. I specifically address three of these issues regarding the Snake Valley pottery series, asking what is the source of Snake Valley Black-on-gray pottery, what is the distribution of Snake Valley Gray, Snake Valley Black-on-gray, and Snake Valley Corrugated, and in what context was Snake Valley Black-on-gray manufactured? These questions are approached via two data sets -- a chemical assay and a distributional analysis. I argue that Snake Valley pottery was probably produced in a restricted area, the Parowan Valley, and that production was organized as community craft specialization, though I acknowledge that more research on this topic is ultimately required.

Nonmarine fluvial, eolian and lacustrine strata of the Chinle and Glen Canyon groups on the southern Colorado Plateau preserve tetrapod body fossils and footprints that are one of the world's most extensive tetrapod fossil records across the Triassic-Jurassic boundary. We organize these tetrapod fossils into five, time-successive biostratigraphic assemblages (in ascending order, Owl Rock, Rock Point, Dinosaur Canyon, Whitmore Point and Kayenta) that we assign to the (ascending order) Revueltian, Apachean, Wassonian and Dawan land-vertebrate faunachrons (LVF). In doing so, we redefine the Wassonian and the Dawan LVFs. The Apachean-Wassonian boundary approximates the Triassic-Jurassic boundary. This tetrapod biostratigraphy and biochronology of the Triassic-Jurassic transition on the southern Colorado Plateau confirms that crurotarsan extinction closely corresponds to the end of the Triassic, and that a dramatic increase in dinosaur diversity, abundance and body size preceded the end of the Triassic.

Maize played a major role in Chaco's interaction with outlying communities in the southern Colorado Plateau. This paper seeks to determine where archaeological corn cobs brought to Chaco Canyon were grown. Strontium-isotope and trace-metal ratios of 180 soil-water and 18 surface-water sites in the Southern Colorado Plateau have revealed possible source areas for some of 37 archaeological corn cobs from Chaco Canyon and 10 archaeological corn cobs from Aztec Ruin, New Mexico. The most probable source areas for cobs that predate the middle-12th-century drought include several Upper Rio Chaco sites (not including Chaco Canyon). There are many potential source areas for cobs that date to the late A.D. 1100s and early 1200s, all of which lie in the eastern part of the study area. Some Athapascan-age cobs have potential source areas in the Totah, Lobo Mesa, and Dinetah regions. One Gallo Cliff Dwelling cob has a strontium-isotope ratio that exceeds all measured soil-water values. Field sites for this cob may exist in association with Paleozoic and Precambrian rocks found 80–90 km from Chaco Canyon. Potential source areas for most Aztec Ruin cobs (many of which were found in rooms dating to the first half of the 13th-century) appear to be associated with a loess deposit that blankets the Mesa Verde and McElmo Dome regions.

We define the geographical distributions of mitochondrial DNA (mtDNA) lineages embedded within a broadly distributed, arid-dwelling toad, Bufo punctatus . These patterns were evaluated as they relate to hypothesized vicariant events leading to the formation of desert biotas within western North America. We assessed mtDNA sequence variation among 191 samples from 82 sites located throughout much of the species' range. Parsimony-based haplotype networks of major identified lineages were used in nested clade analysis (NCA) to further elucidate and evaluate shallow phylogeographic patterns potentially associated with Quaternary (Pleistocene-Holocene) vicariance and dispersal. Phylogenetic analyses provided strong support for three monophyletic lineages (clades) within B. punctatus . The geographical distributions of the clades showed little overlap and corresponded to the general boundaries of the Peninsular Desert, and two continental desert regions, Eastern (Chihuahuan Desert-Colorado Plateau) and Western (Mojave-Sonoran deserts), geographically separated along the Rocky Mountains and Sierra Madre Occidental. The observed divergence levels and congruence with postulated events in earth history implicate a late Neogene (latest Miocene-early Pliocene) time frame for separation of the major mtDNA lineages. Evaluation of nucleotide and haplotype diversity and interpretations from NCA reveal that populations on the Colorado Plateau resulted from a recent, likely post-Pleistocene, range expansion from the Chihuahuan Desert. Dispersal across historical barriers separating major continental clades appear to be recent, resulting in secondary contacts in at least two areas. Given the observed contact between major clades, we speculated as to why the observed deep phylogeographic structure has not been eroded during the multiple previous interglacials of the Pleistocene.

The US Geological Survey and the State geological surveys of many coal-bearing States recently completed a new assessment of the top producing coal beds and coal zones in five major producing coal regions-the Appalachian Basin, Gulf Coast, Illinois Basin, Colorado Plateau, and Northern Rocky Mountains and Great Plains. The assessments, which focused on both coal quality and quantity, utilized geographic information system technology and large databases. Over 1,600,000 million short tons of coal remain in over 60 coal beds and coal zones that were assessed. Given current economic, environmental, and technological restrictions, the majority of US coal production will occur in that portion of the assessed coal resource that is lowest in sulfur content. These resources are concentrated in parts of the central Appalachian Basin, Colorado Plateau, and the Northern Rocky Mountains. D (L.F. Ruppert).

Strata of the Moenave Formation on and adjacent to the southern Colorado Plateau in Utah-Arizona, USA represent one of the best known and most stratigraphically continuous, complete and fossiliferous terrestrial sections across the Triassic-Jurassic boundary. We present here a synthesis of new biostratigraphic and magnetostratigraphic data collected from the Moenave Formation across the outcrop belt, which extends from the St. George area in southwestern Utah to the Tuba City area in northern Arizona. These ...

The genus Yucca is widely recognized for its pollination mutualism with yucca moths. Analysis of diversiWcation in this interaction has been hampered by the lack of a robust phylogeny for the genus. Here we attempt the Wrst extensive nuclear DNA based assessment of the phylogenetic relationships of Yucca. We used AFLP markers to recover the phylogeny of 87 samples representing 38 Yucca taxa. An analysis based on 4322 markers strongly supported a topology consistent with morphological classiWcation at the section level (capsularfruited Chaenocarpa, Xeshy-fruited Sarcocarpa, and spongy-fruited Clistocarpa). Within Sarcocarpa, all but two of the traditional species were monophyletic. Within Chaenocarpa, the morphologically distinct series Rupicolae was strongly supported. In the remaining Chaenocarpa, a western group (Colorado Plateau southward) and an eastern group (Great Plains, central Texas east to Florida) were recovered. Within these groups, where taxonomic circumscriptions are narrow and historically contested, there was at most limited monophyly of traditional taxa, suggesting rapid recent diversiWcation, introgression, or non-monophyletically circumscribed taxa.

This article draws together data from two of Crow Canyon Archaeological Center's recent research projects and combines these data in new ways to elucidate the relationship between Mesa Verde region soil development and non-irrigation farming practices. The Pueblo Farming Project (PFP) seeks to preserve traditional farming knowledge and educate the public concerning traditional farming and the place of corn in Pueblo cultures. The Basketmaker Communities Project (BCP) focuses on understanding the Basketmaker III Period and the development of Early Pueblo communities. Pedologic data from each of Crow Canyon's experimental gardens, a mature pi~ non-juniper forest, and four Basketmaker sites reveal patterns of soil development. The Mesa Verde Loess-based soils become indurated with use and must be remediated, fallowed, or abandoned, with implications for site choice and residence time. Induration and productivity appear to vary inversely over time, with impacts due to management, vegetation, exposure, and use-life. Understanding the interplay of climate, cultural practice , and pedogenesis is, therefore, key to deciphering this geocultural record and pursuing agricultural sustainability in this region. We present a framework for unifying these lines of investigation and to facilitate moving future studies forward together. [Colorado Plateau, pedology, paleoe-cology, agriculture, archaeology]

The study of coprolites (desiccated feces) is recognized as a viable method for analyzing parasitism of prehistoric peoples. Eight species of helminth parasites, including nematodes, cestodes, and acanthocephalans, have been recovered from archaeological sites on the Colorado Plateau. The comparative analysis of parasitological findings illustrates the effects of changing subsistence strategies and varying life-style on prehistoric human parasitism. This comparative study is based on the analysis of coprolites recovered from one Archaic hunter-gatherer site and two Anasazi agricultural villages. Hunter-gatherers are represented by coprolites from Dust Devil Cave in southeastern Utah. Coprolites of prehistoric agriculturalists from Antelope House in Canyon de Chelly, Arizona, and from Salmon Ruin in northwestern New Mexico were studied. The results demonstrate that helminth parasitism increased with the advent of agriculture. Between the agricultural sites, differences in patterns of excreta disposal, foraging behavior, and local ecology resulted in pronounced variations in both percentage of coprolites containing parasite remains and the number of parasite species represented.

Significant ecological, hydrologic, and geomorphic changes have occurred during the 20th century along many large floodplain rivers in the American Southwest. Native Populus forests have declined, while the exotic Eurasian shrub, Tamarix, has proliferated and now dominates most floodplain ecosystems. Photographs from late 19th and early 20th centuries illustrate wide river channels with largely bare in-channel landforms and shrubby higher channel margin floodplains. However, by the mid-20th century, floodplains supporting dense Tamarix stands had expanded, and river channels had narrowed. Along the lower Green River in eastern Utah, the causal mechanism of channel and floodplain changes remains ambiguous due to the confounding effects of climatically driven reductions in flood magnitude, river regulation by Flaming Gorge Dam, and Tamarix invasion. This study addressed whether Tamarix establishment and spread followed climate- or dam-induced reductions in annual peak flows or whether Tamarix was potentially a driver of floodplain changes. We aged 235 Tamarix and 57 Populus individuals, determined the hydrologic and geomorphic processes that controlled recruitment, identified the spatial relationships of germination sites within floodplain stratigraphic transects, and mapped woody riparian vegetation cohorts along three segments of the lower Green River.
The oldest Tamarix established along several sampling reaches in 1938, and 1.50–2.25 m of alluvium has accreted above their germination surfaces. Nearly 90% of the Tamarix and Populus samples established during flood years that exceeded the 2.5-year recurrence interval. Recruitment was most common when large floods were followed by years with smaller peak flows. The majority of Tamarix establishment and Green River channel narrowing occurred long before river regulation by Flaming Gorge Dam. Tamarix initially colonized bare instream sand deposits (e.g., islands and bars), and most channel and floodplain changes followed the establishment of Tamarix. Our results suggest that Tamarix recruitment was triggered by large annual floods that were followed by years with lower peak flows, not by periods of low flow alone. Tamarix appears to have actively invaded floodplains, while Populus colonization has been limited. Thus, Tamarix invasion may have greatly influenced floodplain development and riparian vegetation composition along the lower Green River since the early 20th century.

incision. This study reveals the importance of integrating soil and ecologic studies with geomorphologic research; such an approach may be critical in helping understand how anthropogenically induced climatic changes of the next century could impact geomorphic processes and the ecology of arid and semiarid regions. © 1997 Elsevier Science B. V.

Vertical-to-inclined, cylindrical trace fossils that occur in the Upper Triassic Chinle and Dolores Formations on the Colorado Plateau are interpreted to be the casts of lungfish burrows. The casts, which are as much as 11 cm in diameter and as much as 1.6 m long, were formed by passive siliciclastic and carbonate sedimentation into apparently abandoned lungfish burrows. Locally, the burrow fillings are overwhelmingly abundant, and many intersect and have destroyed former burrow fillings. Superposition of bioturbation episodes has obliterated most primary sedimentary structures. This bioturbation has contributed to the mottled coloration and the knobby-weathering texture of the rocks. The burrow-fillings occur ubiquitously in three lithofacies, comprising 1) purple-and white-mottled, silicified sandstone and siltstone, 2) red and brown siltstone and mudstone, and 3) pink and green limestone. These strata were deposited in a continental environment that included fluvial channels and floodplains, sand sheets and playa mudflats, and lacustrine basins, marshes, and deltas.

Identification of the source of CO 2 in natural reservoirs and development of physical models to account for the migration and interaction of this CO 2 with the groundwater is essential for developing a quantitative understanding of the long term storage potential of CO 2 in the subsurface. We present the results of 57 noble gas determinations in CO 2 rich fields (>82%) from three natural reservoirs to the east of the Colorado Plateau uplift province, USA (Bravo Dome, NM., Sheep Mountain, CO. and McCallum Dome, CO.), and from two reservoirs from within the uplift area (St. John's Dome, AZ., and McElmo Dome, CO.). We demonstrate that all fields have CO 2 / 3 He ratios consistent with a dominantly magmatic source. The most recent volcanics in the province date from 8 to 10 ka and are associated with the Bravo Dome field. The oldest magmatic activity dates from 42 to 70 Ma and is associated with the McElmo Dome field, located in the tectonically stable centre of the Colorado Plateau: CO 2 can be stored within the subsurface on a millennia timescale.

The Colorado Plateau is located in the interior, dry end of two moisture trajectories coming from opposite directions, which have made this region a target for unusual climate fluctuations. A multidecadal drought event some 850 years ago may have eliminated maize cultivation by the first human settlers of the Colorado Plateau, the Fremont and Anasazi people, and contributed to the abandonment of their settlements. Even today, ranching and farming are vulnerable to drought and struggle to persist. The recent use of the Colorado Plateau primarily as rangeland has made this region less tolerant to drought due to unprecedented levels of surface disturbances that destroy biological crusts, reduce soil carbon and nitrogen stocks, and increase rates of soil erosion. The most recent drought of 2002 demonstrated the vulnerability of the Colorado Plateau in its currently depleted state and the associated costs to the local economies. New climate predictions for the southwestern United States include the possibility of a long-term shift to warmer, more arid conditions, punctuated by megadroughts not seen since medieval times. It remains to be seen whether the present-day extractive industries, aided by external subsidies, can persist in a climate regime that apparently exceeded the adaptive capacities of the Colorado Plateau's prehistoric agriculturalists.

The objective of this study was to characterize the community structure and activity of N 2 -fixing microorganisms in mature and poorly developed biological soil crusts from both the Colorado Plateau and Chihuahuan Desert. Nitrogenase activity was approximately 10 and 2.5 times higher in mature crusts than in poorly developed crusts at the Colorado Plateau site and Chihuahuan Desert site, respectively. Analysis of nifH sequences by clone sequencing and the terminal restriction fragment length polymorphism technique indicated that the crust diazotrophic community was 80 to 90% heterocystous cyanobacteria most closely related to Nostoc spp. and that the composition of N 2 -fixing species did not vary significantly between the poorly developed and mature crusts at either site. In contrast, the abundance of nifH sequences was approximately 7.5 times greater (per microgram of total DNA) in mature crusts than in poorly developed crusts at a given site as measured by quantitative PCR. 16S rRNA gene clone sequencing and microscopic analysis of the cyanobacterial community within both crust types demonstrated a transition from a Microcoleus vaginatus-dominated, poorly developed crust to mature crusts harboring a greater percentage of Nostoc and Scytonema spp. We hypothesize that ecological factors, such as soil instability and water stress, may constrain the growth of N 2 -fixing microorganisms at our study sites and that the transition to a mature, nitrogen-producing crust initially requires bioengineering of the surface microenvironment by Microcoleus vaginatus.

Uranium mining on the Navajo Reservation created an environmental justice disaster which has strangely helped bring the Navajo Nation to achieve considerable self-determination within the United States. The United States’ need for uranium to fuel the nuclear weapons and energy program brought the Atomic Energy Commission to establish an extensive mining operation on Southwestern edge of the Colorado Plateau. Many of mines established were on or near the Navajo Indian reservation. The Navajo Nation received little share in the profits due to poorly constructed lease and royalty contracts. What is more, most mines employed almost entirely Navajo men who were never told of the known health hazards from radiation expose. The Navajo people were desperate to work, the AEC was driven to produce uranium as quickly as possible, and the mining companies working for the AEC wanted the largest possible profits. Despite pressure from the Public Health Service (PHS), who had been gathering data r...

A fundamental tectonic boundary appears to have existed below the site of the present-day Colorado Plateau to Great Basin Transition Zone since Precambrian times. The Plateau proper has seen little deformation since Middle Proterozoic continental assembly apart from Cenozoic uplift and limited thickskinned contraction and calc-alkaline plutonism. In contrast, the Great Basin region has been subject to repeated episodes of both contractional and extensional tectonism, and extensional activity continues into the modern day. Evidence exists that the Colorado Plateau at its western margin is being converted to lithosphere with rifted Great Basin properties. Some models for migrating extension call upon progressive gravitational collapse of thicker crust of the plateau margin as it warms, possibly aided by hardening of the previously rifted lithosphere (i.e., Great Basin interior) via crustal thinning and cooling. However, this rather homogeneous and temporally gradual model of deformation has only partial applicability to evolution of the western Colorado Plateau and eastern Great Basin. On the one hand, the limited degree of block style faulting, high elevation, and high apparent elastic thickness of the Transition Zone resemble properties of the Colorado Plateau. On the other, heat flow, upper mantle velocities, and deep electrical conductivity of the transition are more like those of the active eastern Great Basin. We suggest that non-uniform extension occurs below the Transition Zone, with thinning of the lower crust and mantle lithosphere by a degree greater than that of the upper crust. Transition Zone extension may be distinctly earlier than that of the eastern Great Basin, with exhumation of the latter occuring quite uniformly in the Early to Middle Miocene, but the former perhaps initiating significantly later (Late Miocene-Early Pliocene). Estimates of total extension and lower crustal material movement for the eastern Great Basin in the Middle Miocene range widely depending upon the assumed role of the Sevier Desert detachment, but present-day extension appears unrelated to this feature. At present, we lack basic geophysical and geological data to resolve even gross contributions of force versus strength, let alone individual force or strength components, in driving deformation of the Transition Zone. Gravitational forces are expected to dominate, while Pacific plate boundary forces are considered negligible, but impact of the Colorado Plateau lithospheric keel upon elevated Great Basin asthenosphere may contribute. Strength indicators for the Transition Zone are conflicting. Uncertainties about the roles of low-angle detachments versus lower crustal flow in Transition Zone rifting reflect a limited knowledge of crust/mantle structure, and thus of processes of extensional consumption of formerly stable lithosphere here. The role of magmatism in the Transition Zone remains cryptic also. Some seismic models suggest a high-velocity "rift pillow" near the Transition Zone, which would imply focused extension and magmatism here, while others show only gradual progression in crustal thickness from west to east. The southern part of the Transition Zone has been highly modified by prior calc-alkaline plutonism which significantly affects upper crustal deformation style, but its influence on whole-lithosphere strength is unclear.

Analyses of stratigraphic sequences within the paleocanyons of the Hualapai Plateau, Arizona, are important because these deposits offer the only evidence for the Paleogene-Neogene geological history of the Grand Canyon area. In this paper, we focus on the origins and paleoenvironmental significance of the West Water Formation, located within the Milkweed and West Water paleocanyons on the Hualapai Plateau. We propose that the supposed " limestone unit " of the West Water Formation at and near its type section is not a limestone; rather, it is a 21 m-thick valley calcrete, overprinted by a ~1–2 m-thick pedogenic calcrete, and subsequently dolomitized in its upper-to-middle sections, with a superimposed 4 m-thick red paleosol. We also propose that this unit is not co-eval in age or origin with the Long Point limestone on the Coconino Plateau, and that the presence of a complex calcrete-dolocrete-paleosol alters previous interpretations associated with this unit. Evidence for a calcrete-paleosol origin, beyond the West Water Formation's lack of fossils, includes: its predominantly micritic calcite-palygorskite composition; its textures characteristic of valley and pedogenic calcrete deposits (as exhibited by thin section, SEM, and TEM analyses); and its association with a relatively thick overlying red paleosol that also contains abundant palygorskite. Stable carbon and oxygen isotope values from carbonate cements are also within the range expected of a near-surface calcrete. Carbonate minerals within the calcrete-dolocrete were precipitated at or near the water table in a valley setting due to evaporation and/or CO 2 degassing in a semi-arid to arid environment of deposition. High 87 Sr/ 86 Sr values within the calcrete were inherited from groundwater infiltrating through Music Mountain Formation arkosic sediments, which were derived from a Precambrian source terrane to the south and southwest. No absolute ages exist for the Music Mountain Formation and West Water Formation in the Milkweed and West Water paleocanyons; these sediments could range in age from the Late Cre-taceous to the latest Eocene-earliest Oligocene, and may record the Eocene-Oligocene Transition in the Grand Canyon area.

To assess how elements leach from several types of coal combustion products (CCPs) and to better understand possible risks from CCP use or disposal, coal ashes were sampled from two bituminous-coal-fired power plants. One plant located in Ohio burns high-sulfur (about 3.9%) Upper Pennsylvanian Pittsburgh coal from the Monongahela Group of the Central Appalachian Basin; the other in New Mexico burns lowsulfur (about 0.76%) Upper Cretaceous Fruitland Formation coal from the San Juan Basin, Colorado Plateau. The sampled CCPs from the Ohio plant were bottom ash (BA), economizer fly ash (EFA), and fly ash (FA); the sampled CCPs from the New Mexico plant were BA, mixed FA/EFA, FA, and cyclone-separated coarse and fine fractions of a FA/EFA and FA blend. Subsamples of each ash were leached using the long-term leaching (60-day duration) component of the synthetic groundwater leaching procedure (SGLP) or the toxicity characteristic leaching procedure (TCLP, 18-hour duration). These ashes were all alkaline. Leachate concentrations and leachabilities of the elements from the CCPs were similar between corresponding CCP types (BA, EFA, and FA) from each plant. The leachabilities of most elements were lowest in BA (least leachable) and increased from EFA to FA (most leachable). Ca and Sr were leached more from EFA than from either BA or FA. Leachability of most elements also increased as FA particle size decreased, possibly due in part to increasing specific surface areas. Several oxyanion-forming elements (As, Mo, Se, U, and V) leached more under SGLP than under TCLP; the opposite was true for most other elements analyzed.

Major-and trace-element analyses of garnets from heavy-mineral concentrates have been used to derive the compositional and thermal structure of the subcontinental lithospheric mantle (SCLM) beneath 16 areas within the core of the ancient Laurentian continent and 11 areas in the craton margin and fringing mobile belts. Results are presented as stratigraphic sections showing variations in the relative proportions of different rock types and metasomatic styles, and the mean Fo content of olivine, with depth. Detailed comparisons with data from mantle xenoliths demonstrate the reliability of the sections.

Janetski, Joel C., Christopher N. Watkins, and Cady B. Jardine. 
2011 Interaction and Exchange in Fremont Society.  In Perspectives on Prehistoric Trade and Exchange in California and the Great Basin, edited by Richard E. Hughes, pp. 22-54.  The University of Utah Press, Salt Lake City.

Much recent and current Fremont research has focused on social and economic life (including trade), with the priority being on probable demographic centers such as Five Finger Ridge, Baker Village, and Parowan Valley where some level of social complexity may have developed (see various but especially Janetski 2002; Janetski et  al. 2000). Stylistic analyses and differential distributional patterns of exotics, ceramics, and obsidian in these and other communities suggest scalar variation within a pan-Fremont interaction sphere. Here we present what we believe to be the critical factors in the deconstruction of the interaction sphere, the explanation of variability in the distributions of specific goods that moved across the Fremont landscape, and the mechanisms responsible for that movement. We believe that understanding of these mechanisms can be elucidated by discussing style and interaction spheres with a focus on tribal societies

eastern Arizona and southeastern Utah were measured at pressure to 7 kb. The data are compared with measurements on Alpine-type peridotires and associated eelogRes. Most of the eelogites have velocities consistent with materials composing the uppermost part of the mantle. Despite significant preferred orientations of pyroxenes, the velocity anisotropy of eelogites from the kimberlite-bearing pipes is considerably smaller than that normally ohsensed in dunRes and most peridotires. The reasons for the lack of a significant aniso•ropy in eelogites as well as for the anisotropies expected in peridotires are discussed on the basis of the elastic properties of the constituent minerals and the rules governing their preferred orientations. The fabric of a lherzolite nodule from Mule Ear suggests a low-velocity anisotrophy. From an application of a fabric-phase diagram for orthopyroxene and olivine to the lherzolite fabric, relatively high temperatures of reerystallization of this rock are indicated.

Detailed examination of the Upper Cretaceous capping sandstone member of the Wahweap Formation in the Kaiparowits Basin, Utah reveals the presence of aeolian stratification. Deposition by aeolian processes is recognized and distinguished from subaqueous deposition by the presence of centimeter-scale, inversely graded wind-ripple stratification. The aeolian stratification in the Wahweap Formation is the first occurrence reported from Upper Cretaceous strata on the Colorado Plateau of the western U.S.A. Aeolian stratification occurs as thin wind-reworked caps of fluvial-bar sandstones deposited within low-sinuosity braided streams and as more extensive deposits of small-scale dunes that developed in geographically restricted dune fields. Aeolian reworking of bars took place during low-stage flow and was possibly controlled by intermittent (seasonal) discharge variations. Prolonged aridity led to increased sand supply entering the aeolian system, dunes nucleated and grew rapidly between the braided stream systems. These small-scale dunes rarely developed extensive or tall slip faces as evidenced by the rare preservation of grain flow strata and the dominance of wind-ripple stratification. The dune field was characterized by sinuous-crested dunes, probably barchans, amid and linked to the extensive braided stream systems. Based on modern analogs, the resulting change in sand storage/supply probably is related to a short-term shift to a more semi-arid/arid climate, possibly seasonally. However, a longer-term climate change to semi-arid/arid may be indicated for the dune complex near the boundary with the overlying Kaiparowits Formation.

In a semi-arid, upland setting on the Colorado Plateau that is underlain by nutrient-poor Paleozoic eolian sandstone, alternating episodes of dune activity and soil formation during the late Pleistocene and Holocene have produced dominantly sandy deposits that support grass and shrub communities. These deposits also contain eolian dust, especially in paleosols. Eolian dust in these deposits is indicated by several

Eolian dust (windblown silt and clay) and biological soil crusts are both important to ecosystem functioning of arid lands. Dust furnishes essential nutrients, influences hydrology, contrib- utes to soil formation, and renders surfaces vulnerable to erosion. Biological soil crusts contribute directly to soil fertility by fixing carbon and nitrogen, and indirectly by trapping newly-deposited dust and stabilizing already-present soil. Results

The genus Yucca is widely recognized for its pollination mutualism with yucca moths. Analysis of diversiWcation in this interaction has been hampered by the lack of a robust phylogeny for the genus. Here we attempt the Wrst extensive nuclear DNA based assessment of the phylogenetic relationships of Yucca. We used AFLP markers to recover the phylogeny of 87 samples representing 38 Yucca taxa. An analysis based on 4322 markers strongly supported a topology consistent with morphological classiWcation at the section level (capsularfruited Chaenocarpa, Xeshy-fruited Sarcocarpa, and spongy-fruited Clistocarpa). Within Sarcocarpa, all but two of the traditional species were monophyletic. Within Chaenocarpa, the morphologically distinct series Rupicolae was strongly supported. In the remaining Chaenocarpa, a western group (Colorado Plateau southward) and an eastern group (Great Plains, central Texas east to Florida) were recovered. Within these groups, where taxonomic circumscriptions are narrow and historically contested, there was at most limited monophyly of traditional taxa, suggesting rapid recent diversiWcation, introgression, or non-monophyletically circumscribed taxa.

Biological soil crusts (BSCs) are topsoil biosedimentary structures built by photosynthetic microbes commonly found today on arid soils. They play a role in soil stabilization and the fertility of arid lands, and are considered modern analogues of ancient terrestrial microbial communities. We determined the concentrations of four biogenic and 21 other elements, mostly metals, in surface soils that hosted BSCs, in the soils underneath those crusts, and in proximate but non-crusted surface soils. The samples were from six sites in the Colorado Plateau highlands and the Sonoran Desert lowlands. In spite of the variability in climate and geologic setting, we found statistically significant overall trends of enrichment in biogenic elements and depletion in non-biogenic elements when BSCs were compared with non-crusted soils. The differences between crusted and non-crusted soils were statistically significant at 95% confidence for C, N (enrichments) and for Ca, Cr, Mn, Cu, Zn, As, and Zr (depletions). These trends are best explained by the activity of microbes. As expected, no differences in the concentrations of C, N, P, and S were detected between the soils underneath the crusts and the non-crusted soils, but the former showed depletion of non-biogenic elements, indicating that the leaching effect of crust microbes extends downward in the soil. These patterns speak to the need for a sustained input of allochthonous material, possibly dust, to maintain BSC fertility. These elemental patterns can be considered a biosignature that may be preserved in the rock record and might help identify ancient microbial communities on land.

Eolian deposition on the semiarid southern Colorado Plateau has been attributed to episodic aridity during the Quaternary Period. However, OSL ages from three topographically controlled (e.g. falling) dunes on Black Mesa in northeastern Arizona indicate that eolian sediments there were deposited in deep tributary valleys as early as 35-30 ka, with most sand deposited before 20 ka. In contrast, the oldest OSL ages for sand sheets fall within the Pleistocene-Holocene climatic transition (~12-8 ka). Thus most eolian sediment accumulated on Black Mesa under climatic conditions that were in general cooler, moister, and more variable than today, not more arid, pointing to a considerable increase in sediment supply.

A new 3-D shear velocity model of the crust and upper mantle beneath the Colorado Plateau and surrounding regions of the southwestern United States was made with finite frequency Rayleigh wave tomography using EarthScope/USArray data. The goal of our study is to examine the Colorado Plateau lithospheric modification that has resulted from Cenozoic tectonism and magmatism. We have inverted for the isotropic Vs model from a grid of Rayleigh wave dispersion curves obtained by a modified two-plane wave method for ...