Basin In New Mexico Research Articles

First taeniodonts (Mammalia, Taeniodonta) from the Paleocene of Canada

ABSTRACT The Taeniodonta comprise one of several groups of eutherians that diversified following the extinction of non-avian dinosaurs, and were among the earliest to achieve a relatively large body in the wake of the mass extinction some 66 million years ago. The fossil record of Taeniodonta is sparse, with much of what is known of their evolution being derived from specimens of early Paleocene age from the San Juan Basin of New Mexico. The record is particularly poor at higher latitudes, and while Schowalteria clemensi—the oldest taeniodont, known from but one specimen from southeastern Alberta—lived alongside dinosaurs and a suite of archaic mammals near the end of the Cretaceous, specimens referable to the order have heretofore not been discovered in Paleocene deposits in Canada, despite nearly 60 years of intensive collecting. I report here on the first evidence of taeniodonts from the Paleocene of western Canada, a record that includes representatives of both families (Huerfanodon, a conoryctid, and Psittacotherium, a stylinodontid). The new records demonstrate not only that taeniodonts occurred at higher latitudes during the early part of the Paleocene in North America, but were exceedingly rare, in keeping with their known occurrences elsewhere. Although taeniodont ecology has been invoked as a possible explanation for their rarity, the comparably sparse records of other large- and small-bodied mammals in local faunas of Paleocene age throughout the Western Interior suggest that taphonomic processes may have played the more significant role.

Predicting areal extent of groundwater contamination through geostatistical methods exploration in a data-limited rural basin

The areal extent of regulatory standard exceedance for groundwater arsenic, fluoride, and nitrate was estimated and compared for multiple methods to evaluate groundwater contamination in a rural basin of New Mexico, USA. First, three geostatistical kriging techniques – Ordinary Kriging (OK), Universal Kriging (UK), and Empirical Bayesian Kriging (EBK) – were explored. Next, the exploration was extended to multivariate analysis (Co-OK, Co-UK, and EBK-regression) using groundwater pH as the other variable, compared to interpolation only considering the contaminant as a primary variable. Finally, non-parametric Indicator Kriging (IK) was utilized for probability mapping and assessing the likelihood of surpassing critical thresholds for contaminant concentrations. The contamination area changes with different kriging methods deployed, and the performances of kriging variants vary for the three chemical components. The models that best fit the empirical data were determined. The study examined the influence of the explanatory variable on the multivariate kriging prediction accuracy. The multivariate kriging approaches enhanced surface prediction accuracy and tended to cover the data limitation of the primary variable interpolations. The multivariate kriging improved spatial prediction of arsenic and fluoride by increasing the Empirical Coverage Probability (ECP) up to 0.05–0.25 from case to case; however, no improvement was observed in ECP for nitrate contamination distribution, as the explanatory variable pH was only weakly correlated with nitrate, suggesting that a stronger correlation between the primary and secondary variables can increase the probability of obtaining prediction improvements through multivariate kriging. This study developed a methodology for characterizing and identifying locations where groundwater had elevated concentrations of contaminants, threatening human health through drinking water exposure. By improving the spatial characterization of groundwater contaminants within the data-limited rural basin, policymakers planning improvements will support mitigation strategies to manage contamination sources of groundwater resources.

Hydrocarbon production induced land deformation over Permian Basin; analysis using persistent scatterer interferometry and numerical modeling

The Permian Basin, encompassing Southeastern New Mexico and Western Texas, has been an important source of oil and natural gas for over a century for the United States. With recent advancements in petroleum extraction methods, such as hydraulic fracturing and horizontal drilling, production has increased exponentially. Such rapid developments, along with the disposal of wastewater back into the subsurface, have caused significant changes in the stress regime of the region’s subsurface, resulting in various geohazards including land subsidence. In this work, we used the Sentinel-1C-band SAR dataset acquired between 2016 and 2021 to measure the basin-wide deformation over the entire Permian Basin. We utilized Persistent Scatterer Interferometry (PSI) technique to produce the time-series deformation at millimeter-level accuracy. The average monthly production and injection volumes and well depths over the Delaware Basin in New Mexico were calculated for each well and the impact of the hydrocarbon activities on the deformation was modeled using a distributed point source model from fluid volume and well depth data. The results show that the Permian Basin was deforming at a rate of 3–4 cm/yr., with two large pockets of deformation to the north of the Grisham Fault Zone (GFZ) in the Delaware Basin. The region south of the GFZ shows complex deformation features with linear patterns, indicating the presence of faults hindering fluid flow. Some areas in the Delaware Basin also show an uplift, especially along the Texas side of the border driven by shallow wastewater injection. The Midland Basin is also affected by subsidence with several localized subsidence zones identified in the region. Further, the Midland Basin experienced an increase in intensity and the spatial distribution of the deformation over the last few years. Given both production and injection well data, the modeled deformation results agree with the observed except in two pockets. When only production data is used for the modeling, the modeled deformation shows better agreement with the observed, especially in the interior of New Mexico. The modeling results suggest that the deep wastewater injection has minimal impact on surface deformation in the region. Additionally, it is also possible that the region has undergone inelastic deformation. While we used an elastic model in this preliminary study, a more accurate study requires regional poroelastic modeling to study the interaction between the solid subsurface and fluid hydrocarbons in detail.

Machine Learning for Geothermal Resource Exploration in the Tularosa Basin, New Mexico

Geothermal energy is considered an essential renewable resource to generate flexible electricity. Geothermal resource assessments conducted by the U.S. Geological Survey showed that the southwestern basins in the U.S. have a significant geothermal potential for meeting domestic electricity demand. Within these southwestern basins, play fairway analysis (PFA), funded by the U.S. Department of Energy’s (DOE) Geothermal Technologies Office, identified that the Tularosa Basin in New Mexico has significant geothermal potential. This short communication paper presents a machine learning (ML) methodology for curating and analyzing the PFA data from the DOE’s geothermal data repository. The proposed approach to identify potential geothermal sites in the Tularosa Basin is based on an unsupervised ML method called non-negative matrix factorization with custom k-means clustering. This methodology is available in our open-source ML framework, GeoThermalCloud (GTC). Using this GTC framework, we discover prospective geothermal locations and find key parameters defining these prospects. Our ML analysis found that these prospects are consistent with the existing Tularosa Basin’s PFA studies. This instills confidence in our GTC framework to accelerate geothermal exploration and resource development, which is generally time-consuming.

Characterization of ambient polychlorinated biphenyl background conditions in surface waters of the Pajarito Plateau, New Mexico.

This study presents the development of polychlorinated biphenyl (PCB) background threshold values (BTVs) that statistically characterize ambient background conditions for surface waters in undeveloped and developed landscapes of the Pajarito Plateau in the Rio Grande Basin of New Mexico. Between 2009 and 2018, surface water data were collected at 45 locations under a variety of flow conditions and regimes. A total of 163 samples were collected, with roughly 1/3 of samples and locations being in undeveloped areas (n = 53 from 17 locations), and the remainder being in developed areas (n = 110 from 28 locations). While there are areas on the Pajarito Plateau where PCB point sources are known or likely to have contributed to PCBs in soils, PCB BTVs calculated for undeveloped portions of watersheds (upstream of areas where PCB point sources are known or likely to have contributed to PCBs in soils, and therefore not affected by PCB sources within the watershed) are well above New Mexico's human health organism-only (HH-OO) water quality criterion (0.64 ng/L). Background threshold values are even higher in developed areas upstream of managed soil sites, suggesting that in developed areas, both diffuse ambient PCB sources (e.g., atmospheric deposition) and localized urban sources (e.g., building materials, paints, and electrical equipment) contribute to PCBs in those watersheds. These findings indicate that New Mexico's current HH-OO water quality criterion for PCBs cannot practicably be met due to ambient conditions. It is also impracticable to meet the US Environmental Protection Agency (EPA) criterion continuous concentration (CCC) of 14 ng/L in developed background areas, where the BTV is approximately 1.5 times the CCC. Integr Environ Assess Manag 2023;19:1307-1319. © 2022 SETAC.

Evaluation of a Minimum Liquid Discharge (MLD) Desalination Approach for Management of Unconventional Oil and Gas Produced Waters with a Focus on Waste Minimization

The objective of this research study was to evaluate the feasibility of using a minimum liquid discharge (MLD) desalination approach as an alternate management option for unconventional produced waters (PWs) with a focus on minimizing the generation of solid waste. The feasibility of MLD was evaluated using OLI, a water chemistry software, to model thermal desalination of unconventional PWs from the Delaware Basin in New Mexico (NM). Desalination was theoretically terminated at an evaporation point before halite (NaCl) saturation in the residual brine. Results of this study showed that selectively targeting a subset of higher flow rate and lower TDS wells/centralized tank batteries (CTBs) could yield up to 76% recovery of distillate while generating minimal solid waste. Using a selective MLD approach did reduce the quantity of distillate recovered when compared with ZLD, and left a reduced volume of residual brine which has to be managed as a liquid waste. However, selective MLD also greatly reduced the amount of solid waste. The use of a ZLD approach yielded incrementally greater quantities of distillate but at the cost of large quantities of difficult-to-manage highly soluble waste. Simulation results showed that waste generated before NaCl precipitation was primarily composed of insoluble compounds such as calcite, barite and celestite, which can be disposed in conventional landfills. This study also found a simple empirical linear relationship between TDS and distillate recovery, thus allowing a non-expert to rapidly estimate potential distillate recovery for a given starting PW quality.

Stratigraphy and hydrocarbon resources of the San Juan Basin: Lessons for other basins, lessons from other basins

This paper examines the relationships between stratigraphy and hydrocarbon production from the San Juan Basin of New Mexico and Colorado. Abundant data and the long production history allow lessons to be learned, both from an exploration and development perspective, that can be applied in other basins. Conversely, as new play types and technologies are defined and developed elsewhere, the applicability of those tools in the San Juan Basin needs to be understood for well-informed exploration and development activities to continue. The San Juan Basin is a Latest Cretaceous – Tertiary (Paleogene) structure that contains rocks deposited from the Lower Paleozoic to the Tertiary, but only the Upper Cretaceous section has significant hydrocarbon, mostly gas, production. Herein I make the case for studying depositional systems, and the controls thereon (e.g., basin development, eustasy, sediment supply), because they are the first-order controls on whether a sedimentary basin can become a hydrocarbon province, or super basin as the San Juan Basin has recently been defined. Only in the Upper Cretaceous did a suitable combination of forcing mechanisms combine to form source and reservoir rocks, and repeated transgressive-regressive cycles of the Upper Cretaceous stacked multiple successions of source and reservoir rocks in a way that leads to stacked pay potential. Because of the types of depositional systems that could develop, the source rocks were primarily gas prone, like those of other Rocky Mountain basins. Oil-prone source rocks are present but primarily restricted to episodes of peak transgression. A lack of suitable trapping mechanisms helps to explain the relative dearth of conventional oil pools. Although gas production has dropped precipitously in the past decade, driven primarily by overabundance of gas supply associated with the shale-gas boom, the combination of horizontal drilling and multi-stage hydraulic fracturing is being applied to revive oil production from some unconventional stratigraphic targets with success.

Mechanical stratigraphy in Mesozoic rocks of the San Juan Basin: Integration of stratigraphic and structural terms and concepts

We characterize relationships between stratigraphy and natural fractures in outcrops of Mesozoic strata that rim the San Juan Basin in New Mexico and Colorado. These outcrops expose fluvial and shallow-marine siliciclastic deposits and calcareous mudstones deposited in a distal marine setting. We focus primarily on a regionally extensive fracture set formed during the Eocene to minimize localized tectonic effects on fracture development. Where possible, we supplement our observations with wireline log- or laboratory-derived measurements of rock properties. Our goals are twofold: 1) to illustrate how direct integration of data and concepts from stratigraphy and structural geology can lead to better fracture characterization, and 2) to develop thought processes that will stimulate new exploration and development strategies. Genetic beds form one scale of stratification in the outcrops we describe. For example, sandstone beds can be arranged into coarsening and thickening upward successions that are the depositional record of shoreline progradation. In fluvial settings, cm- to dm-scale sandstone beds can also be part of m-scale single-storey channel complexes that, themselves, can be arranged into amalgamated channel complexes 10s of m thick. In these and other settings, it is important to distinguish between beds and features that can be defined via wireline logs because it is the former (cm- to dm-scale) that are usually the primary control the distribution of natural fractures. The extension fractures we describe are typically bed-bound, with bedding being defined by lithology contrasts and the associated changes in elastic properties. Fracture spacing distributions are typically lognormal with average spacing being less than bed thickness. Although mechanical bedding and depositional bedding are commonly the same, diagenesis can cut across bed boundaries and complicate this relationship, especially where lithologic contrasts are small. Deposits from similar depositional environments which undergo different diagenetic histories can have substantially different mechanical properties and therefore deform differently in response to similar imposed stresses.

Comparing Resource Plays in the Texas and New Mexico Permian Basin – Implications for Exploration Research

The Permian Basin in Western Texas and North Eastern New Mexico is an energy powerhouse. With three sub-basins i.e., Delaware, Central Basin Platform and Midland Basin producing hydrocarbons from both conventional and unconventional plays, the Texan Permian has been a focus of more interest from energy companies than the North-Western Shelf of the basin in New Mexico. However, the less explored North Western shelf of the basin in New Mexico furnishes equal opportunity for oil and gas exploration companies for further exploration research and subsequent discoveries. This research is an attempt to showcase the exploration significance and highlight the gaps for in exploration research in the New Mexico Permian Basin. We compare the oil plays in both Texas and New Mexico Permian based on reservoir geology and basin architecture. Overall, The Permian Basin is dominated by carbonate reservoirs. They account for 75% of all oil production followed by clastics, which contribute 14%; then come the mixed clastics and carbonates accounting for 8%; and lastly cherts make up around 3%. The leading growing production zone is the San Andres platform (Northwest shelf) carbonate play (4.0 billion bbl) followed by the Leonard restricted platform carbonate play (3.3 billion bbl). The Lower Permian Horseshoe and Pennsylvanian plays are next (2.7 billion bbl) and lastly by the San Andres platform carbonate play contributes to the overall production (2.2 billion bbl). With known potential of shelf plays we determine that North Western Shelf has similar stratigraphy and extensive hydrocarbon potential yet to be researched and explored.

Satellite monitoring of fugitive methane emissions from oil and gas facilities in Australia

Since 2016, GHGSat has been operating the world’s first and only satellite specifically designed to monitor methane emissions from industrial facilities around the world. The lessons learned through the success of this demonstration satellite have been incorporated into the company’s next two satellites, the first of which was originally scheduled to launch in September 2019 but was delayed as a result of a rocket failure. The satellite’s technology is ideally suited to the oil and gas industry, particularly unconventional developments in which a high density of facilities can be present. This paper introduces the technology briefly and discusses the predictive analytics applications being developed to augment the efficacy of the satellites in detecting methane emissions. An example of successful application of the predictive analytics engine to detect a methane leak in the Delaware Basin in New Mexico is presented. Parallels are drawn between shale basins in the US and the Surat Basin in Australia, highlighting the applicability of the technology for the oil and gas industry in Australia.

A Tribute to Tributaries: Endangered Fish Distributions within Critical Habitat of the San Juan River, USA

AbstractThe extent of fish movements in contemporary river networks can depend on spatial position relative to attractive features that may provide food and refuge, such as tributary mouths, or restrictive features, such as barriers. From the San Juan River basin in New Mexico and Utah, we integrated remote summertime PIT tag detections at two tributary mouths (McElmo Creek and Chaco Wash) with main‐stem recapture data from 2012 to 2015 to determine if two endangered species, Colorado Pikeminnow Ptychocheilus lucius and Razorback Sucker Xyrauchen texanus, differed in tributary use, demography, and seasonal ranges. Razorback Suckers were more abundantly detected (n = 266 individuals) and recaptured (n = 145) than were Colorado Pikeminnows (n = 96 detected; n = 55 recaptured). Despite the San Juan River flowing uninterrupted between the tributary mouths, individuals of each species separated into tributary‐specific groups. Razorback Suckers had very similar sizes and ages at each tributary, reflecting a homogeneous augmented population. Colorado Pikeminnows separated into tributary‐specific groups of either adult (Chaco Wash) or subadult (McElmo Creek) fish based on total length and age. Analyses suggested that fish size was a significant factor explaining the extent of seasonal ranges for both species. Although the ranges of both species exhibited a tributary effect, this effect was more significant in explaining Razorback Sucker ranges than Colorado Pikeminnow ranges, which were explained best by season. Understanding how mobile species interact with attractive and inhibitive river features can help managers identify potential sampling biases along with possible consequences of spatially structured populations. Managers should consider extending sampling upstream of barriers, installing additional permanent antenna arrays, and maintaining perennial flows in these tributaries.

Using a coupled agent-based modeling approach to analyze the role of risk perception in water management decisions

Abstract. Managing water resources in a complex adaptive natural–human system is a challenge due to the difficulty of modeling human behavior under uncertain risk perception. The interaction between human-engineered systems and natural processes needs to be modeled explicitly with an approach that can quantify the influence of incomplete/ambiguous information on decision-making processes. In this study, we two-way coupled an agent-based model (ABM) with a river-routing and reservoir management model (RiverWare) to address this challenge. The human decision-making processes is described in the ABM using Bayesian inference (BI) mapping joined with a cost–loss (CL) model (BC-ABM). Incorporating BI mapping into an ABM allows an agent's psychological thinking process to be specified by a cognitive map between decisions and relevant preceding factors that could affect decision-making. A risk perception parameter is used in the BI mapping to represent an agent's belief on the preceding factors. Integration of the CL model addresses an agent's behavior caused by changing socioeconomic conditions. We use the San Juan River basin in New Mexico, USA, to demonstrate the utility of this method. The calibrated BC-ABM–RiverWare model is shown to capture the dynamics of historical irrigated area and streamflow changes. The results suggest that the proposed BC-ABM framework provides an improved representation of human decision-making processes compared to conventional rule-based ABMs that do not take risk perception into account. Future studies will focus on modifying the BI mapping to consider direct agents' interactions, up-front cost of agent's decision, and upscaling the watershed ABM to the regional scale.

Identifying natural and anthropogenic variability of uranium at the well scale, Homestake Superfund site, near Milan, New Mexico, USA

The San Mateo Creek Basin in New Mexico, USA is located within the Grants Mineral Belt-an area with numerous uranium (U) ore deposits, mines, and milling operations. Six monitoring wells set in an alluvial aquifer near the Homestake Mining Co. Superfund site in the lower San Mateo Creek Basin were logged with a suite of borehole geophysical tools including spectral gamma-ray (SGR), vertically profiled with passive samplers for U and selenium (Se) concentrations, and purged sampled for same constituents. The integrated approach allowed for an assessment on the role of heterogeneity (both physical and chemical) in determining U concentrations in groundwater. Uranium, as measured with SGR logging, is ubiquitous in the alluvial aquifer and the underlying Chinle Group. Aqueous U concentrations appear to be inversely related to thorium (Th) concentrations, as measured by the SGR log, indicating the possibility that U is bound in or adsorbed to clays in the aquifer. The stratigraphy of the alluvium likely plays a role in elevated concentrations of aqueous U. Interbedded clay and sand layers allow for the mobilization of U in oxic sandy layers from U adsorbed in sediments in reduced clay layers. The stratigraphy also plays a role in the degree of mixing of groundwater in the formation and well. Mixing can obscure the ability to identify U sources. Mixing is exacerbated by the relatively long screens (> 20 ft long or > 6.1 m) of the monitoring wells.

Network analysis of intrasite material networks and ritual practice at Pueblo Bonito

The Chaco World, centered on the San Juan Basin of New Mexico, in the Southwestern U.S.A., was organized largely around ritual activities, including the use and deposition of a wide range of rare and unusual objects. The great houses of Chaco Canyon were foundational in the development of these ritual activities. Biographical or assemblage-oriented approaches are well suited to studying ritual behavior and have been successfully applied to understanding religious ritual at Chacoan great houses, especially the site of Pueblo Bonito. While formal network analyses (and traditional statistical analyses) are typically used to evaluate relationships between archaeological sites, we argue that network analysis also has great utility in expanding existing biographical approaches to Chacoan ritual. Applying network methods to a network of general artifact classes (like turquoise or pipes) from different room contexts within Pueblo Bonito helps to understand the co-associations of objects grouped together through common use or deposition, likely in the course of ritual activities. These co-associations help expand our knowledge of ritual behavior within Pueblo Bonito, indicating distinctions between architectural spaces based on specialized ritual practices. This analysis also has important implications for Chacoan social organization, supporting existing arguments for a Chacoan house society model.

Mapping the energy footprint of produced water management in New Mexico

Hydraulic fracturing (HF) and horizontal drilling have revolutionized the fossil fuel industry by enabling production from unconventional oil and gas (UOG) reserves. However, UOG development requires large volumes of water, and subsequent oil and gas production from both conventional and unconventional wells generate large volumes of produced water (PW). While PW is usually considered a waste product, its reuse may lessen demand for freshwater supplies, reduce costs for transportation and disposal, and reduce the risks for injection-induced seismicity. Whether this water is disposed of or treated and reused, both methods require significant amounts of energy. The objective of this study was to identify the primary energy demands of alternative water management strategies, and to characterize and quantify their geographic variability in four oil and gas producing basins in New Mexico using a single year of production. Results illustrate the importance of each component of each produced water management strategy in determining its total energy footprint. Based on 2015 production and water use data, the energy to extract fresh groundwater for hydraulic fracturing (34 GWh-th yr−1.) exceeds the energy that would be required if the same volume of PW were treated chemically (19 GWh-th yr−1.). In addition, the energy required to transport fresh water and dispose of PW (167 GWh-th yr−1.) is far greater than that required to move treated PW (8 GWh-th yr−1.) to a point of reuse. Furthermore, transportation distances, which contribute significantly to the total energy footprint of a given management strategy, are underestimated by nearly 50% state-wide. This indicates that reuse may be an even more energy efficient way to manage PW, even with energy-intensive treatment strategies like electrocoagulation. Reuse of PW for HF is not only more energy efficient than conventional management techniques, it also reduces both demand for scarce fresh water resources and use of disposal wells. By evaluating components of each management strategy individually, this work illustrates how the energy footprint of regional PW management can be reduced. The advent of UOG recovery in the last decade highlights the need to understand existing water management in the industry, identify opportunities and strategies for improvement, and recognize that these dynamics are likely to change into the future.

Puebloan Agriculture and its Impact on the Migratory Behavior of Birds

Towards the end of the thirteenth century, the Albuquerque Basin of New Mexico saw a significant increase in population from Puebloan peoples migrating into the valley. By the time of the Coronado expedition in 1541–1542, this area contained 12 large pueblos along the roughly 55 km long by 5 km wide Rio Grande floodplain, resulting in one of the densest concentrations of pueblos and agricultural fields in the Eastern Pueblo region. Zooarchaeological analyses of Classic Period faunal assemblages have yielded an abundance and diversity of wild bird remains with an emphasis towards migratory birds that reside in the region during the winter. These avifauna are almost entirely absent from the archaeological record of the preceding Developmental Period. This paper argues that changes in Puebloan farming practices between the two periods had a direct effect on shifting the traditional wintering grounds of these migratory birds northwards into the Albuquerque Basin.

Theoretical Approach To Model Gas Adsorption/Desorption and the Induced Coal Deformation and Permeability Change

Recovery of coalbed methane (CBM) can trigger a series of coal-gas interactions, including methane desorption, coal deformation, and associated permeability change. These processes may impact each other. A primary objective of this analysis is to simultaneously quantify these interactions and their impacts during CBM recovery. To achieve this and other objectives, a rigorously coupled adsorption–strain–permeability model was developed. Gas adsorption, coal deformation, and cleat permeability characteristics were described using simplified local density (SLD) adsorption theory, a theory-based strain model, and matchstick-based permeability models, respectively. The strain model was verified against measured methane-adsorption-induced coal strain data published during the past 60 years, and the coupled model was tested using well test data measured in the San Juan Basin of New Mexico in the United States. Results suggest that the strain model is very consistent with measured coal deformation data for fluid ...

The hydrogeology of the Sacramento Mountains and Roswell and Salt basins of New Mexico, USA: overview of investigations on dryland groundwater systems using environmental tracers and geochemical approaches

The hydrogeology of the Sacramento Mountains and Roswell and Salt basins of New Mexico, USA: overview of investigations on dryland groundwater systems using environmental tracers and geochemical approaches

Lone Butte: A Folsom Hunting Camp and Overlook in the Central Tularosa Basin of New Mexico

The Lone Butte site represents a substantial lithic assemblage from a Folsom hunting camp and overlook locality in the central Tularosa Basin of south-central New Mexico. It appears to be similar to the Rio Rancho site in the Central Rio Grande Valley in terms of its landscape position and assemblage signature. Lone Butte represents the largest and most comprehensive lithic assemblage from any Paleoindian site in the Tularosa Basin, strongly documented to have a substantial history of Folsom occupation. Interestingly, the Lone Butte assemblage is distinguished from the overall regional pattern in having relatively high proportions of preforms and channel flakes, which are made predominantly from Rancheria chert located at a distance of 40–100 km west of the site. This assemblage clearly reflects the anticipated mobility which seems partly characteristic of Folsom technological and settlement organization.

Baenid turtles of the Kaiparowits Formation (Upper Cretaceous: Campanian) of southern Utah, USA

I describe the assemblage of baenid turtles found in the Campanian Kaiparowits Formation of southern Utah and compare it with baenids from other basins across Laramidia. Baenids were one of the most diverse and abundant freshwater turtle clades during the Late Cretaceous. They were restricted to North America, with all except the basal-most taxon (Arundelemys) restricted to Laramidia. During the Campanian, baenids were conspicuous parts of the turtle assemblages of Alberta, Montana and New Mexico. The baenids of the Kaiparowits Formation are critical in that they provide an assemblage from southern Laramidia that is correlative with those from northern Laramidia, allowing for more accurate testing of Campanian palaeobiogeographical hypotheses. In this paper, two new baenid species, Neurankylus hutchisoni sp. nov. and Neurankylus utahensis sp. nov., are described. Additionally, the first description of cranial material from Denazinemys nodosa is provided. A comprehensive survey of collected material indicates that at least six baenid taxa are present in the formation, including Neurankylus hutchisoni, Neurankylus utahensis, Thescelus sp., Arvinachelys goldeni, Denazinemys nodosa and Boremys grandis. Arvinachelys, Neurankylus hutchisoni and Neurankylus utahensis have not been identified outside of the Kaiparowits Basin, but Denazinemys nodosa and Boremys grandis both are known from younger sediments of the San Juan Basin of New Mexico. Members of the genus Thescelus are known from the Campanian of New Mexico and the Maastrichtian of Wyoming, Montana and Saskatchewan, but are conspicuously absent in the Campanian of Alberta and Montana. The baenid assemblage in the Kaiparowits Formation provides support for both basin-scale endemism and north–south provincialism across Laramidia during the Campanian. There is also evidence for a latitudinal gradient in diversity, as only three baenid species have been reported from the temporally correlated Dinosaur Park Formation in Alberta.http://zoobank.org/urn:lsid:zoobank.org:pub:75DF6CFF-3E87-4729-9798-975C0157514F