Canyon Site Research Articles

A Pilot Study of Wichita Indian Archeology and Ethnohistory

In 1965 several anthropologists drew up plans for a one-year pilot study of the archeology and ethnohistory of the Wichita Indian tribes. After financial support had been generously provided by the National Science Foundation, the proposed research was carried out. This is a report on the results of that study. The pilot study was designed to: a) obtain a body of field data from the components of the Spanish Fort sites, the largest and best=documented of the historic Wichita sites in the Red River area; b) make test excavations at several other sites in order that a problem=oriented program of future research can be accurately planned; c) attempt to locate, by field reconnaissance, sites that relate to the Wichita occupation of the southern plains on both the historic and prehistoric time levels; d) make a survey of available ethnohistorical data in order (1) to compile a bibliography of documentary materials relevant to Wichita ethnohistory, (2) to make a detailed study of documents that relate specifically to the excavations being carried out at Spanish Fort and at the sites being tested, (3) to seek information that might lead to the field locations of other Wichita sites, and (4) to appraise those sources best suited for more extended examination. The co-investigators of the project were Tyler Bastian of the Museum of the Great Plains, Robert E. Bell of The University of Oklahoma, Edward B. Jelks of Southern Methodist University, and W.W. Newcomb of the Texas Memorial Museum at The University of Texas. Bastian supervised the archeological field work in Oklahoma under the direction of Bell. Jelks directed the archeological work in Texas. Newcomb directed the ethnohistorical research. Marvin E. Tong of the Museum of the Great Plains served the project as general coordinator. The main part of the ethnohistorical study consisted of a thorough search of the archives at The University of Texas for documents relating to Wichita ethnohistory. The archeological work included extensive excavations at the Longest Site in Oklahoma and at the Upper Tucker and Coyote Sites in Texas. More limited excavations were carried out at the Glass and Gas Plant Sites in Texas. Several other archeological sites were visited but not excavated beyond a test pit or two: the Devils Canyon and Wilson Springs Sites in Oklahoma, and the Gilbert, Stone, Vinson, and Womack Sites in Texas. An effort was also made to locate several sites in Oklahoma and Texas which were reported in historical documents but which had not been located in the field. After the library research and the archeological field work had been completed, a brief, general report could have been prepared to satisfy our contractual obligation to the National Science Foundation. It was felt, however, that the data which had been collected would be of interest to archeologists and ethnohistorians and, if possible, it should be made available to them in some detail without delay. Consequently, a series of descriptive papers was prepared instead of a summary report. Those papers are presented here.

A new approach to generating non-uniform support excitation at topographic sites

This study investigates different methods for generating non-uniform support acceleration at actual topographic sites. The factors affecting the non-uniform excitation of a topographic site include the time delay between the arrival times of incident waves at different soil depths, causing a phase difference, and the coherence function. The existing coherence models are based on data recorded on flat surfaces and are not suitable for surfaces with topographic features. Therefore, in the present study, models of a canyon site subjected to Ricker waves with different predominant frequencies, shear wave velocities, and shape ratios have been developed, and the results of boundary element analyses in the time domain (using the BEMSA code) have been obtained at different elevations on the canyon surface. Then, by conducting a statistical analysis employing the symbolic regression method on the results of numerous presumed cases, the relationships for calculating the time delay between the support responses and the coherence function of V-shaped canyons were obtained. To verify the accuracy of the proposed relationships, the results were compared with the records from the Pacoima Dam site during two different earthquakes and a good agreement was obtained between the results. Eventually, by implementing the proposed relationships in the random vibration method, the non-uniform acceleration of the site was simulated. The results indicate that the proposed relationships have an appropriate level of accuracy for calculating the time delay and the spectral coherence function of V-shaped canyons.

Jointed Rock Mass Effects on the Seismic Waves Scattering from the Canyon Sites in the Dam's Support

Jointed Rock Mass Effects on the Seismic Waves Scattering from the Canyon Sites in the Dam's Support

Habitat complexity mediates the predator-prey space race.

The spatial relationship between predator and prey is often conceptualized as a behavioral response race, in which prey avoid predators while predators track prey. Limiting habitat types can create spatial anchors for prey or predators, influencing the likelihood that the predator or prey response will dominate. Joint spatial anchors emerge when predator and prey occupy similar feeding habitat domains and risk and reward become spatially conflated, confusing predictions of which player will win the space race. These spatial dynamics of risk-foraging trade-offs are often obscured by habitat heterogeneity and community complexity in large vertebrate systems, fueling ambiguity regarding the generality of predictions from predator-prey theory. To test how habitat distribution influences the predator-prey space race, we examine correlation in puma and vicuña habitat selection and space use at two sites, one of which generates a distinct risk-foraging trade-off at a joint spatial anchor. The distribution of vegetation, which serves as both forage for vicuñas and stalking cover for pumas, differs between the sites; the llano contains a single central meadow that acts as a joint spatial anchor, while the canyon is characterized by more heterogeneous vegetation. Puma-vicuña habitat selection correlation was positive in the llano and negative in the canyon, and similarly, utilization distributions were more strongly correlated in the llano than the canyon. Vicuña locations occurred at higher values of puma habitat selection and utilization in the llano than in the canyon. Similarly, puma locations in the llano occurred at higher values of vicuña habitat selection and utilization than in the canyon. Although pumas consistently selected for and utilized vegetative and topographic cover regardless of habitat distribution, vicuñas only selected against vegetation in the heterogeneous canyon site, reducing spatial correlation with pumas. Our work suggests a joint spatial anchor favors pumas in the space race due to the inability for vicuñas to avoid crucial foraging habitat. The outcome of the predator-prey space race appears to be strongly informed by the distribution of habitat, whereby corresponding predictability of predator and prey favors predators in the spatial game.

A new boundary element solution to evaluate the geometric effects of the canyon site on the displacement response spectrum

This paper presents a step-by-step procedure using the three-dimensional boundary element approach to study the behavior of semi-circular canyons under seismic shear waves. The boundary element code TDASC allows utilization for various canyon geometries, evaluation of concurrent seismic waves and calculation of the ground motions on canyons due to an excitation at any arbitrary point of the incident field. Considering the widening ratio of the canyon (including prismatic, semi-prismatic and non-prismatic canyons), wave characteristics (wavelength, dimensionless period, direction) and maximum amplification pattern, the solution was applied to carry out a series of parametric studies. It was shown that canyon form can significantly affect the displacement amplification, especially at the points located on its edges. By increasing the wave dimensionless frequency (η > 1), the amplification pattern becomes more complex. On the basis of the results from a variety of considered cases, a new expression has been presented for the limiting wavelength beyond which the widening of the canyon will not have a major effect on the displacement amplification. To verify the reliability of the proposed approach, the obtained results, expressed in terms of displacement amplitude, were compared with those from the available published literature and a reasonably good agreement was observed.

Potential to reduce the concentrations of short-lived climate pollutants in traffic environments: A case study in a medium-sized city in Brazil

Understanding the spatio-temporal variation of short lived climate pollutants (SLCP) over cities is critical to protect public health and mitigate climate change. There is a lack of knowledge about the distribution of SLCP in South America, mainly in medium-sized cities (<1 million inhabitants). This work reports on results of a campaign conducted at several sites (street canyon, urban background, and suburban) in Londrina, Brazil. The pollution datasets (black carbon BC, nitrogen oxides NOx, ozone O3, fine particles PM2.5, and particle number PN) were analyzed by using descriptive statistics, diurnal cycles, time-space correlations, and establishing linkages with traffic rates and with wind conditions. Hourly mean (±standard deviation) BC concentrations ranged from 0.58 (±0.54) in the suburban area to 3.43 (±2.69) µg m−3 at the street canyon site (10,150 vehicles d−1 on weekdays), showing a high spatio-temporal variability even at short scales. PN (mean of 17,469 cm−3) and NOx (mean of 51.58 µg m−3) concentrations tracked BC levels and traffic rates, particularly the number of diesel buses at the canyon site. PM2.5 and O3 levels presented a lower spatial variability, with poor correlation with traffic rates in the canyon and were more tied to regional sources. NOx, BC, and PN showed the highest reduction potentials connected to the abatement of traffic emissions in the city center, particularly by targeting heavy-duty diesel vehicles. The reduction of PM2.5 and O3 concentrations is more challenging due to a significant regional contribution that requires cutting down emissions at state, national or even transboundary scales.

Simulation of fully nonstationary spatially variable ground motions on a canyon site

A new method of deriving evolutionary power spectral density (EPSD) function on surface of a canyon site with multiple soil layers was proposed. After the power spectral density on the base rock was determined, the auto/cross power spectral density function on site surface can be obtained by using the frequency response function (FRF), and a series of ground motions can then be generated. However, the spectral nonstationarity was neglected because the parameters in the FRF varied only with frequency. In the present paper, the time-varying frequency and damping ratio in FRF for each soil layer were incorporated for the derivation of the EPSDs on the surface. The influence of local site conditions on the coherency loss was considered. Spatially variable ground motions (SVGMs) possessing full nonstationarity were then simulated. A set of verifications was conducted, and the results showed that the proposed method is reliable.

Late Holocene paleoceanography in the Chukchi and Beaufort Seas, Arctic Ocean, based on benthic foraminifera and ostracodes

Calcareous microfossil assemblages in late Holocene sediments from the western Arctic continental shelf provide an important baseline for evaluating the impacts of today’s changing Arctic oceanography. This study compares 14C-dated late Holocene microfaunal assemblages of sediment cores SWERUS-L2-2-PC1, 2-MC4 and 2-KL1 (57 mwd), which record the last 4200 years in the Herald Canyon (Chukchi Sea shelf), and HLY1302-JPC-32, GGC-30, MC-29 (60 mwd), which record the last 3000 years in the Beaufort Sea shelf off the coast of Canada. Foraminiferal and ostracode assemblages are typical of Arctic continental shelf environments with annual sea-ice cover and show relatively small changes in terms of variability of dominant species. Important microfaunal changes in the Beaufort site include a spike in Spiroplectammina biformis coinciding with a decrease in Cassidulina reniforme in the last few centuries suggesting an increase of Pacific Water influence and decreased sea-ice. There is low-amplitude centennial-scale variability in proportions of benthic foraminiferal species, such as C. reniforme. In addition to these species, Cassidulina teretis s.l., Elphidium excavatum clavatum and Stainforthia feylingi are also common at this site. At the Herald Canyon site in the last few centuries, C. reniforme peaks around 150 years BP and then decreases while Spiroplectammina earlandi spikes and Acanthocythereis dunelmensis decreases also suggesting an increase in Pacific Water influence and decreased sea-ice at this site. This site also includes Buccella spp. and Elphidium excavatum clavatum. Differences in benthic foraminifera and ostracode species dominance between the two sites may be due to a greater influence of Pacific Water in the Chukchi shelf, compared to the more distal Beaufort shelf, which is also affected by the Beaufort Gyre and the Mackenzie River.

Characteristics and source apportionment of black carbon in the Helsinki metropolitan area, Finland

Black carbon is emitted from the incomplete combustion of carbonaceous fuels and will detrimentally affect air quality, climate and human health. In this study, equivalent black carbon (eBC) concentrations were measured by using an aethalometer (AE33) at three different locations in the Helsinki metropolitan area, Finland from October 2015 to May 2017. One sampling site was located in an urban street canyon (SC, sampling period 18 months) and two of the sampling sites were located in suburban detached house (DH) areas (DH1, 13 months and DH2, 5 months). Based on the campaign averages, the eBC concentration levels were higher at the street canyon site (1690 ± 1520 ng/m3) than at the residential detached house areas (DH1 = 880 ± 1500 ng/m3 and DH2 = 1040 ± 2130 ng/m3). The contribution of eBC from fossil fuel (BCFF) and wood burning (BCWB) were estimated based on the spectral dependence of light absorption of different sources. The spectral behavior is described using absorption Ångström exponent (α) values for both fossil fuel (αFF) and wood burning (αWB) that were determined using concurrent wood burning tracer (levoglucosan) measurements. Based on the source apportionment, the contribution of BCWB to eBC was clearly higher at the detached house area sites DH1 (41 ± 14%) and DH2 (46 ± 15%) than at the urban street canyon site (15 ± 14%). A distinct seasonal dependency was observed in the eBC concentration levels at the detached house areas. The highest concentrations were detected during the cold seasons due to residential wood combustion. On the opposite, at the SC site, the concentration levels of eBC were rather constant throughout the campaign, being dominated by the BCFF emissions from close-by vehicular traffic. Substantial temporal and spatial variability in eBC concentrations and sources were observed within the Helsinki metropolitan area. eBC is shown to be closely tied to the characteristics of the measurement site, season, meteorological conditions and the time of the day.

Suprabenthic crustacean assemblages subjected to high-energy hydrodynamic events in the Blanes Canyon and adjacent slope (NW Mediterranean Sea)

Submarine canyons and adjacent slopes from the NW Mediterranean Sea are subjected to high seasonal and inter-annual variability in hydrodynamic processes. Such an environmental setting has a profound influence in the spatial and temporal variability of deep-sea benthic assemblages. We analyzed the suprabenthic crustacean assemblages from the Blanes Canyon and the adjacent slope along a bathymetric gradient. Macer-Giroq sledge hauls were taken from 900 to 2250 m depth in the canyon axis and southwestern adjacent slope in the autumn of 2008, 2009 and 2012. From the twenty four hauls sampled, one hundred and seventy one species were identified. Major changes in densities, number of species and diversity were only found at particular depths or years. In general the samples yielded variable densities (from approx. 10 to 539 ind.100 m−2), mostly owing to temporal fluctuations in motile fauna such as amphipods and mysids, in relation to the occurrence of energy-driven events. The environmental conditions associated to these events coupled with particular topographic features at the shallowest sites (namely at 900 m depth) lead to contrasting biodiversity patterns in the canyon and adjacent slope: high dominance and subsequent depressed diversity in the canyon and the highest diversity on the slope at similar depths. At the deepest sites, suprabenthic diversity reached similar values in the canyon and adjacent slope, probably owing to the decreased influence of disturbance processes at greater depths. Trophic diversity decreased with depth only in the slope, while in the canyon it remained constant likely owing to the relatively enhanced trophic conditions found in the canyon at all depths. However, the community composition differed significantly between the canyon and adjacent slope and at contrasting depths (<1200 m vs. >1200 m). At shallowest depths, the canyon sites were characterized by a high contribution of motile omnivores while the slope sites were characterized by a high contribution of detritivores to the total abundance. Highly motile predators on zooplankton were dominant at deepest sites in both environments. Our results suggest that taxonomic and trophic diversity in the northwestern Mediterranean may be influenced by the abrupt topography and its interaction with hydrodynamic conditions (intensification of currents; variable intensity of disturbance/hydrodynamic events; food pulses linked to food availability). These are major drivers which influence the spatial and temporal availability of food sources to the various faunal compartments eventually propagating up the food web.

The Use of Unmanned Aerial Vehicles (UAVs) in Slope Stability Assessment

The use and applications of unmanned aerial vehicles (UAVs) in geotechnical engineering is rapidly growing, leading to changes in the way that data is acquired, analyzed and processed. UAVs can reach areas previously inaccessible via ground or helicopter, while also being quickly deployed. Cameras are the current standard for data collection and 3D model creation.&#x0D; There are multiple types of UAV’s currently available. Quadcopters can take off and land in spatially constrained areas, but carry a small stabilized camera producing low quality models. Octocopters permit an increased payload, so a higher quality camera can be attached, allowing for increased model accuracy. Flight time is reduced by the additional weight. Fixed wing UAVs create higher quality photogrammetry models, and are commonly deployed over large surface areas. Transport Canada certification must be approved prior to any flights occurring for research or work. A detailed application must be created, including a flight plan and demonstration of prior flight experience.&#x0D; At the White Canyon site in B.C., a Phantom 4 Quadcopter was flown for geotechnical analysis of a complex geometry slope, which has previously been studied for several years. The terrain has occluded the data available from the ground or from permissible helicopter flight paths. Therefore, detailed information from the slope has not been previously available. The process of using a UAV to obtain these data sets, to develop a full 3D model of these areas of the slope is discussed, considering the accuracy and quality of the data available.

Additional analysis of mtDNA from the Tommy and Mine Canyon sites

Ancient mitochondrial DNA analysis of samples from the Chaco outlier Tommy and Mine Canyon sites (dating to PII and PIII, respectively, and located near Farmington, New Mexico) originally revealed distinctly different haplogroup frequency distributions from one another. An additional twelve samples were added to those already published (Snow et al., 2010), bringing the total number of individuals with mitochondrial DNA data to 60. The additional samples diminished this difference but maintained the statistically significant distinction between the sites, pointing to a potential sampling bias at the Mine Canyon Site that might explain some, but not all, of the difference. The sites were compared with those from both modern and prehistoric populations in the desert Southwest and Mexico to better understand the regional context of the inhabitants, as well as inter-regional relationships, demonstrating that the Tommy Site fits well within the general Southwestern pattern, while the Mine Canyon Site stands out due to its higher than normal frequency of haplogroup A2. Thirteen burials from a kiva structure at the Mine Canyon Site are compared to the remainder of the excavated burials from the site in terms of mtDNA, burial position, pathology, and grave goods. The statistically significant differences of the kiva burials are discussed in terms of possible evidence of site abandonment, disease, slavery, and witchcraft.

Influence of habitat heterogeneity on the community structure of deep-sea harpacticoid communities from a canyon and an escarpment site on the continental rise off California

The sediment-covered deep-sea floor was initially thought to be environmentally homogeneous. Recent work has shown otherwise, and deep-sea ecologists have been searching for ecologically important environmental heterogeneities on different spatial and temporal scales, with particular interest in canyons. Here we report results for harpacticoid copepods from a site at 3262m depth in the axis of Monterey Canyon and one on an escarpment 46km away at 3090m depth. Multivariate community analyses revealed significant differences between sites in community structure. Absolute abundance, the ratio of subadult copepodites to adults, species density, the proportion of the harpacticoid individuals that emerged, and the proportion that lived in tubes were significantly lower at the canyon site than at the escarpment site. The proportion of the harpacticoid individuals that belonged to the surface-dweller life-style group was significantly higher than at the escarpment site. These marked differences imply that ecologically important environmental heterogeneities exist. We speculate that differences between the sites in food conditions and sediment grain-size distributions are among them.

Using ambient noise measurements to model urban particle number size distributions at a traffic site

Urban road traffic is a major joint emission source for particles and ambient noise. This study explores the relationship between both environmental stressors at an urban traffic site and analyses the potential to model particle number size distributions (NSD) from measurements of ambient noise frequency levels. Thus, a measurement campaign was conducted within an urban street canyon covering a period of 50 days. First, noise frequency levels were used to successfully model traffic intensity at the street canyon site on a half-hourly basis (R2 = 0.78). Thereafter, two multiple linear regression models were built to calculate NSD using noise frequency levels in combination with meteorological quantities (wind speed and air temperature) and air pollutant data (NO2) as explanatory variables. Implementation of meteorological quantities in Model 1 captured the diurnal variation of measured NSD. However, total particle number concentration (TNC) as derived from modelled NSD underestimated observed TNC. Implementation of NO2 led to higher model performance for TNC (R2 = 0.57) but not for particle NSD. Detailed information about urban background particle concentrations as a proxy for local conditions and about boundary layer conditions (e.g. atmospheric stability, mixing layer height) might help improving the model. The spatial characteristics of the site and their acoustical effects were not considered in the present approach (e.g. distance to road or buildings, road surface), hence, the results should be transferred to other sites with some caution.

Ambient concentrations and insights on organic and elemental carbon dynamics in São Paulo, Brazil

The São Paulo Metropolitan Area (SPMA) is a megacity with about 20 million people and about 8 million vehicles, most of which are fueled with a significant fraction of ethanol - making it a unique case worldwide. This study presents organic and elemental carbon measurements using thermal-optical analysis from quartz filters collected in four sampling sites within the SPMA. Overall Organic Carbon (OC) concentration was comparable at all sites, where Street Canyon had the highest concentration (3.37 μg m−3) and Park site the lowest (2.65 μg m−3). Elemental Carbon (EC), emitted as result of incomplete combustion, has been significantly higher at the Street Canyon site (6.11 μg m−3) in contrast to all other three sites, ranging from 2.25 μg m−3 (Downtown) to 1.50 μg m-3 (Park). For all sampling sites, the average OC:EC ratio are found on the lower bound (<2) of what is usually observed for other megacities, highlighting the significant contribution of EC in Sao Paulo. At the Street Canyon site, average OC:EC ratio was 0.56, to our knowledge the lowest value ever observed for any urban site. An approach for apportionment between primary and secondary organic carbon based on primary OC:EC ratio was evaluated. The secondary OC was estimated to be 30–40% of total OC concentrations throughout the various sampling sites.The organic carbon dynamics has been further studied using each of the thermally-derived organic carbon fractions. Each of these has been studied regarding their correlation with EC and the correlation between different sites. The analyses have identified that the OC3 and OC4, i.e., the carbon fraction which evolves from the filter at temperatures above 450 °C, presents a regional behavior, with high correlation among all sites. Conversely, OC1, the first fraction to evolve, has depicted a more local characteristic. Furthermore, the fraction of OC which becomes char during the temperature increase under inert atmosphere (the Pyrolytic Carbon-PC) has been the only fraction not to present a significant correlation with EC. Since that EC is assumed to be a primary emission marker, it indicates that PC is not significant in traffic emissions. This study provided innovative insights of the organic aerosol content associated with air pollution dynamics in a megacity impacted by a unique vehicular fleet. It also shows the need of implementation of EURO VI technology and to improve mass transport systems such a metro and more bus corridors to allow better transport for 19 million people in the SPMA.

Insights into methane dynamics from analysis of authigenic carbonates and chemosynthetic mussels at newly-discovered Atlantic Margin seeps

The recent discovery of active methane venting along the US northern and mid-Atlantic margin represents a new source of global methane not previously accounted for in carbon budgets from this region. However, uncertainty remains as to the origin and history of methane seepage along this tectonically inactive passive margin. Here we present the first isotopic analyses of authigenic carbonates and methanotrophic deep-sea mussels, Bathymodiolus sp., and the first direct constraints on the timing of past methane emission, based on samples collected at the upper slope Baltimore Canyon (∼385 m water depth) and deepwater Norfolk (∼1600 m) seep fields within the area of newly-discovered venting. The authigenic carbonates at both sites were dominated by aragonite, with an average δC13 signature of −47‰, a value consistent with microbially driven anaerobic oxidation of methane-rich fluids occurring at or near the sediment–water interface. Authigenic carbonate U and Sr isotope data further support the inference of carbonate precipitation from seawater-derived fluids rather than from formation fluids from deep aquifers. Carbonate stable and radiocarbon (δC13 and ΔC13) isotope values from living Bathymodiolus sp. specimens are lighter than those of seawater dissolved inorganic carbon, highlighting the influence of fossil carbon from methane on carbonate precipitation. U–Th dates on authigenic carbonates suggest seepage at Baltimore Canyon between 14.7±0.6 ka to 15.7±1.6 ka, and at the Norfolk seep field between 1.0±0.7 ka to 3.3±1.3 ka, providing constraint on the longevity of methane efflux at these sites. The age of the brecciated authigenic carbonates and the occurrence of pockmarks at the Baltimore Canyon upper slope could suggest a link between sediment delivery during Pleistocene sea-level lowstand, accumulation of pore fluid overpressure from sediment compaction, and release of overpressure through subsequent venting. Calculations show that the Baltimore Canyon site probably has not been within the gas hydrate stability zone (GHSZ) in the past 20 ka, meaning that in-situ release of methane from dissociating gas hydrate cannot be sustaining the seep. We cannot rule out updip migration of methane from dissociation of gas hydrate that occurs farther down the slope as a source of the venting at Baltimore Canyon, but consider that the history of rapid sediment accumulation and overpressure may play a more important role in methane emissions at this site.

Evaluation of trade and interaction between Chaco Canyon and Chaco outlier sites in the American Southwest by investigating trachybasalt temper in pottery sherds

Deciphering trade and interaction in prehistory is central for archeologists to understand social, economic, political, and religious ties among groups in a particular area. Constraint on the provenance of raw materials used for manufacturing pottery vessels and their original sources is critical to these goals. In this study, trade patterns and interaction between Pueblo Bonito in Chaco Canyon and Pueblo groups in the Chuska Mountains, along with four Chaco outliers in the Four Corners area of the American Southwest, were investigated using chemical analysis of sanidine crystal inclusions identified in three groups of trachybasalt pottery temper and rocks from the Navajo volcanic field. Initial petrographic analyses were then complemented with chemical analyses using EMP and LA-ICP-MS to determine the concentrations of major and rare trace elements of the sanidine identified in trachybasalt rocks and temper sherds. Partial least squares regression on trace element concentrations from sanidine analyses for the pottery sherds and rock samples demonstrate that although the majority of sanidine tempered materials was procured from Narbona Pass in the Chuska Mountains, New Mexico, some ceramic samples were still procured from other areas of the Navajo volcanic field. The results of our provenience and geochemical study indicate that a strong relationship between Chaco Canyon and Chaco outliers should be reconsidered, and that a political and religious model of exchange—people in Chaco Canyon and Chuska Mountains controlled production and exchange systems in the San Juan Basin—should be reevaluated.

Native Wildlife Use Of Highway Underpasses In A Desert Environment

Abstract While highway underpasses and culverts are often identified in conservation planning as wildlife corridors, their success at facilitating connectivity in deserts has rarely been tested. We evaluated wildlife use of seven, pre-existing highway underpass structures and four associated canyon sites over 29 mo to identify spatial and temporal wildlife use patterns and to assess factors that may constrain wildlife use, particularly for native carnivore species. Our results indicate that a wide diversity of wildlife species utilize the underpass structures including rodents, lagomorphs, deer, and carnivores. Structural attributes of the underpasses have a minor influence on use by most observed species, although structural characteristics and human activity both contributed to determining bobcat (Lynx rufus) usage. Wildlife and human diel patterns differed between the underpass sites and their associated canyons. We suggest that providing a range of underpass structures to support use by a diversity of...

Evaporation of traffic-generated nanoparticles during advection from source

Abstract Earlier work has demonstrated the potential for volatilisation of nanoparticles emitted by road traffic as these are advected downwind from the source of emissions, but there have been few studies and the processes have yet to be elucidated in detail. Using a dataset collected at paired sampling sites located respectively in a street canyon and in a nearby park, an in depth analysis of particle number size distributions has been conducted in order to better understand the size reduction of the semi-volatile nanoparticles. By sorting the size distributions according to wind direction and fitting log normal modes, it can be seen that the mode peaking at around 22 nm at the street canyon site is on average shrinking to 6.2 nm diameter at the park site which indicates a mean shrinkage rate for these particles of 0.13 nm s−1 with temperatures within the range 12–18 °C. The diurnal variation of the shrunken mode in the park reflects the diurnal pattern of particle concentrations at the street canyon site taken as the main source area. An analysis of peak diameter for the smallest mode at the downwind park site shows an inverse relationship to wind speed suggesting that dilution rather than travel time is the main determinant of the particle shrinkage rate. An evaluation of previously collected C10 to C35 n-alkane data from a different urban location shows a good fit to Pankow partitioning theory reflecting the semi-volatility of compounds believed to be representative of the composition of diesel exhaust nanoparticles, hence confirming the feasibility of an evaporative mechanism for particle shrinkage.

How Do Surficial Lithic Assemblages Weather in Arid Environments? A Case Study from the Atacama Desert, Northern Chile

Archaeological sites composed only of surficial lithics are widespread in arid environments. Numerical dating of such sites is challenging, however, and even establishing a relative chronology can be daunting. One potentially helpful method for assigning relative chronologies is to use lithic weathering, on the assumption that the most weathered artifacts are also the oldest. Yet, few studies have systematically assessed how local environmental processes affect weathering of surficial lithics. Using macroscopic analyses, we compared the weathering of surficial lithic assemblages from seven mid‐to‐late Holocene archaeological sites sampled from four different microenvironments in the Atacama Desert of northern Chile. Changes in polish, texture, shine, and color were used to establish significant differences in weathering between two kinds of locations: interfluves and canyon sites. Lithics from interfluve sites were moderately to highly weathered by wind and possessed a dark coating, whereas canyon lithics were mildly weathered despite greater exposure to moisture, often lacked indications of eolian abrasion, and lacked dark coatings. Our results show that lithic weathering can be used as a proxy for relative age, but only after considering local environmental factors. The power of such chronologies can be improved by combining archaeological, paleoenvironmental, geomorphological, and taphonomic data.