Garfield County Research Articles

Stable-isotope chemostratigraphy as a tool to correlate complex Mississippian marine carbonate facies of the Anadarko shelf, Oklahoma and Kansas

The Mississippian section of the United States mid-continent Anadarko Basin (Oklahoma and Kansas) has been a prolific hydrocarbon reservoir since the 1920s, yet large-scale regional correlations between individual stratigraphic units remain difficult because of the complex and heterogeneous nature of the carbonate facies. New sedimentologic and carbon isotopic data from a nearly continuous Mississippian core (Pan American 1 Albert Severin) from the Anadarko Basin, Oklahoma (Garfield County), United States, provides insight into the potential of carbon-isotope chemostratigraphy as a correlation tool in complex stratigraphic successions for which biostratigraphic data are not available. The carbon isotopic composition () of whole-rock samples was analyzed to determine if stratigraphic trends reflect global changes in the carbon cycle. A large positive shift (+5.6‰) in the lower Tournaisian (Kinderhookian), consistent values (averaging +2.3‰) in the upper Tournaisian through middle Visean (upper Kinderhookian–Meramecian), and a negative shift (−2.3‰) in the uppermost Visean (lower Chesterian) correspond to trends in the carbon isotopic compositions ( values) from other regional data sets, including the global type section at Arrow Canyon, Nevada. Further analysis of the data reveals that isotopic compositions are not facies dependent, suggesting that marine chemistry and depositional changes in the Anadarko Basin reflect global environmental changes during the Mississippian. These inferences demonstrate the potential of the Pan American 1 Albert Severin core to be a Mississippian-type section for the Anadarko Basin, and that stable-isotope chemostratigraphy can be used as a correlation tool to better understand the subsurface in complex successions, such as the Mississippian limestone of the United States mid-continent.

New or rare species of cymbelloid diatoms (Bacillariophyceae) from Colorado (USA)

The cymbelloid diatoms of the Rocky Mountain region of the United States are not well known, with only a few species having been reported. Collections of diatoms from Rifle Falls in Garfield County, Colorado, USA, contain a wide range of cymbelloid diatom diversity. The collections include a new species of Cymbella, C. subtravertiensis sp. nov., belonging to the Cymbella helvetica group, which lacks apical pore fields. In addition, a rare species of Encyonopsis originally documented from Austria is also present, for which we include the first published electron microscope study of its valve morphology; this is the first report of this species in the United States. In addition, three new species of Encyonopsis, including E. coloradensis sp. nov., E. rockiensis sp. nov., and E. riflensis sp. nov. are documented with light and scanning electron microscopy, and these species provide excellent examples of the subtle morphological differences that can exist within the genus with regard to the morphology of the areolae and alveoli. Finally, we document a new species of Encyonema, E. calcephila sp. nov., that is similar to E. hustedtii, a species from Java.

A new fossil salamander (Caudata, Proteidae) from the Upper Cretaceous (Maastrichtian) Hell Creek Formation, Montana, U.S.A.

ABSTRACT North American Late Cretaceous salamanders are principally known by isolated atlantes and trunk vertebrae. Here I describe a new genus and species of fossil salamander, Paranecturus garbanii, gen. et sp. nov., based on these elements from the lower portions of the Hell Creek Formation (Maastrichtian), Garfield County, northeastern Montana, U.S.A. It is diagnosed by a unique combination of character states that include the presence of an alar-like process of the atlas and a groove on the posterior face of the neural arch and solid dorsal rib-bearers of the trunk vertebrae. My phylogenetic analysis of 13 caudate taxa and 23 atlantal and trunk vertebral characters recovered P. garbanii as a member of the Proteidae. P. garbanii represents the oldest fossil record of the Proteidae and demonstrates that this lineage was present before the Cretaceous-Paleogene mass extinction event. SUPPLEMENTAL DATA—Supplemental materials are available for this article for free at www.tandfonline.com/UJVP

Estrogen and Androgen Receptor Activities of Hydraulic Fracturing Chemicals and Surface and Ground Water in a Drilling-Dense Region

The rapid rise in natural gas extraction using hydraulic fracturing increases the potential for contamination of surface and ground water from chemicals used throughout the process. Hundreds of products containing more than 750 chemicals and components are potentially used throughout the extraction process, including more than 100 known or suspected endocrine-disrupting chemicals. We hypothesized that a selected subset of chemicals used in natural gas drilling operations and also surface and ground water samples collected in a drilling-dense region of Garfield County, Colorado, would exhibit estrogen and androgen receptor activities. Water samples were collected, solid-phase extracted, and measured for estrogen and androgen receptor activities using reporter gene assays in human cell lines. Of the 39 unique water samples, 89%, 41%, 12%, and 46% exhibited estrogenic, antiestrogenic, androgenic, and antiandrogenic activities, respectively. Testing of a subset of natural gas drilling chemicals revealed novel antiestrogenic, novel antiandrogenic, and limited estrogenic activities. The Colorado River, the drainage basin for this region, exhibited moderate levels of estrogenic, antiestrogenic, and antiandrogenic activities, suggesting that higher localized activity at sites with known natural gas-related spills surrounding the river might be contributing to the multiple receptor activities observed in this water source. The majority of water samples collected from sites in a drilling-dense region of Colorado exhibited more estrogenic, antiestrogenic, or antiandrogenic activities than reference sites with limited nearby drilling operations. Our data suggest that natural gas drilling operations may result in elevated endocrine-disrupting chemical activity in surface and ground water.

Human health risk assessment of air emissions from development of unconventional natural gas resources

BackgroundTechnological advances (e.g. directional drilling, hydraulic fracturing), have led to increases in unconventional natural gas development (NGD), raising questions about health impacts. ObjectivesWe estimated health risks for exposures to air emissions from a NGD project in Garfield County, Colorado with the objective of supporting risk prevention recommendations in a health impact assessment (HIA). MethodsWe used EPA guidance to estimate chronic and subchronic non-cancer hazard indices and cancer risks from exposure to hydrocarbons for two populations: (1) residents living >½mile from wells and (2) residents living ≤½mile from wells. ResultsResidents living ≤½mile from wells are at greater risk for health effects from NGD than are residents living >½mile from wells. Subchronic exposures to air pollutants during well completion activities present the greatest potential for health effects. The subchronic non-cancer hazard index (HI) of 5 for residents ≤½mile from wells was driven primarily by exposure to trimethylbenzenes, xylenes, and aliphatic hydrocarbons. Chronic HIs were 1 and 0.4. for residents ≤½mile from wells and >½mile from wells, respectively. Cumulative cancer risks were 10 in a million and 6 in a million for residents living ≤½mile and >½mile from wells, respectively, with benzene as the major contributor to the risk. ConclusionsRisk assessment can be used in HIAs to direct health risk prevention strategies. Risk management approaches should focus on reducing exposures to emissions during well completions. These preliminary results indicate that health effects resulting from air emissions during unconventional NGD warrant further study. Prospective studies should focus on health effects associated with air pollution.

Stemming retail leakage with a sense of community: Leveraging the links between communal ties and shopping decisions

Retail business development is a broad goal for both private business interests as well as local policymakers, yet the goal of retail opportunities for local residents themselves is often seen as secondary. This paper considers the argument that retail opportunities and sense of community are in fact linked in important ways, links that reinforce the social fabric of a community and/or neighborhood. The paper first briefly reviews the inherent linkages between retail shopping and local development patterns, and then considers the sense of community in the context of Garfield County in western Colorado. Based on the key questions derived from this background, we formally test the inter-relationship between local retail spending and sense of community from detailed survey data, then more broadly consider the factors that critically shape a locality's “sense of community.” These findings shape several important policy implications.

Proving Whether or Not Contamination is Caused by Oil and Gas Operations

Oil and gas development is becoming increasingly controversial in the U.S., in part because of uncertainty about the causes of groundwater contamination in active gas fields. Debates about whether contamination is caused specifically by hydraulic fracturing and whether gas wells should be regulated under the Safe Drinking Water Act rage, but without the relatively rare smoking gun, the question whether oil and gas development has caused contamination evades both scientific and legal determinations. The inability to determine causation is a problem that fuels public distrust of government and industry and deserves a serious effort to solve.In 2010, 2,682 wells were drilled in Pennsylvania, about 500 more than in Colorado’s Garfield County. Home to the Piceance Basin, Garfield County’s natural gas boom commenced in about 2004. That year, the Colorado Oil and Gas Conservation Commission (COGCC) permitted 796 wells in Garfield County -- a number that climbed steadily to 2,888 by 2008, the peak year to date. Whereas oil and gas development was previously concentrated offshore and in more confined parts of the Gulf Coast and Rocky Mountains, it is now occurring in more heavily populated areas such as Pennsylvania. Although the industry sparked controversy in its traditional territory, the volume of the public opposition has increased as development has invaded more populous regions and much of this controversy is fueled by concerns about water quality.During a 2009 public hearing on the New York Department of Environmental Conservation’s Supplemental Generic Environmental Impact Statement on oil and gas development, protesters in New York City held anti-development signs, interrupted official presentations and were escorted out of the venue. The New York legislature imposed a moratorium in November 2010 in order to allow the Department of Environmental Conservation to better study modern oil and gas development techniques, and federal legislators from New York, Pennsylvania and Colorado have called for federal regulation of the hydraulic fracturing (fracking) process under the auspices of the Safe Drinking Water Act (SDWA). Some of the reasons that oil and gas development is so controversial are that it is an industrial activity that is allowed under common law to encroach upon residential areas where it causes nuisance noise, odor and pollution. But it is also implicated in instances of ambient groundwater contamination that have not been fully resolved. This lack of resolution serves as a rallying cry for anti-development groups, and results partly from failures to adequately address issues of causation and proof. Public pressure, in turn, has spawned legislative proposals such as the so-called FRAC Act.

Identification of Leptosphaeria maculans Pathogenicity Group 4 Causing Blackleg on Winter Canola in Oklahoma.

Winter canola (Brassica napus L.) is a relatively new crop to Oklahoma and other southern U.S. states where it is considered a desirable rotation crop with wheat. In 2009, approximately 15,000 ha of winter canola were harvested in Oklahoma (3); that area is expected to almost double in 2010. Blackleg, a potentially devastating canola disease, was detected in Oklahoma in 2009. Blackleg is caused by Leptosphaeria maculans (Desmaz.) Ces. & de Not (anamorph = Phoma lingam (Tode:Fr.) Desmaz.). In early 2010, leaf samples showing typical symptoms of blackleg were collected from four canola fields near the town of Enid in Garfield County, OK. Small portions of infected tissues were surface disinfested in an aqueous solution of NaOCl (0.5% a.i.) for 1 min, rinsed twice in sterile distilled water, and plated on V8 medium. Seven colonies were isolated and when grown in pure culture, all produced 2 × 4.5 μm guttulate, unicellular, hyaline spores in pycnidia that ranged from 200 to 480 μm in diameter. These morphological characteristics correspond with those of P. lingam (1). To verify the pathogenic nature of the isolates and establish the pathogenicity group (PG) to which they belong, a standard inoculation protocol was followed on a set of three differential cultivars, Quinta, Glacier, and Westar (2). Briefly, for each isolate, tiny puncture wounds were made with sterile needles on the cotyledons of six 10-day-old plants of each differential and a 10-μl aliquot of a pycnidiospore suspension (1 × 107 spores ml-1) was deposited on the wounds. Also, a set of differentials were inoculated with distilled water (mock inoculation). Inoculated plants were incubated overnight in a misting chamber at 21°C in the dark and returned the next day to the greenhouse. Disease severity was recorded 10 days after inoculation using a 0 to 9 scale in which 0 to 2 = resistant, 3 to 6 = intermediate, and 7 to 9 = susceptible. This process was repeated three times. Two of the seven isolates evaluated were highly virulent on all three differentials, an indication they belong to pathogenicity group 4 (2). The other five isolates produced small lesions on Westar (resistant reaction) but failed to develop symptoms on the other two differentials. This phenotypic reaction has been associated with strains of PG-1. Mock-inoculated plants did not develop lesions. To our knowledge, this is the first time blackleg isolates from Oklahoma have been identified to the PG level. While this information will assist breeders in the development of both spring and winter canola lines with resistance to blackleg, additional studies are necessary to determine the relative prevalence and diversity of the various PG in Oklahoma.

Actual evapotranspiration estimation for different land use and land cover in urban regions using Landsat 5 data

Evapotranspiration (ET) is deemed critical for water resources management. Even in the same climatic and meteorological conditions, actual ET (ETa) may exhibit remarkable spatial variability across different vegetation covers, agricultural land use practices, and differing types of urban land development. The main objectives of this study are (1) to evaluate the possible closure of the heat balance equation using Oklahoma's unique environmental monitoring network; and (2) to estimate ETa and determine the variation with regards to varying types of land use and land cover in urban settings. In this study, a Surface-Energy-Balance ET algorithm was implemented to estimate ETa at a higher spatial resolution using Landsat 5 satellite images while the Oklahoma Mesonet observations can be used as our ground truth data. Accuracy of the estimated ETa was assessed using latent heat flux measurements provided by AmeriFlux towers. The associated bias ratios of daily mean ETa with respect to both burn and control sites are -0.92%, and -8.86% with a correlation of 0.83 and 0.81, respectively. Additionally, estimated ETa from a water balance budget analysis and the remotely sensed ETa are cross-validated with a low bias ratio of 5.2%, and a correlation coefficient of 0.7 at the catchment scale. The lowest ETa was observed for developed urban areas and highest for open water bodies. The ETa difference is also demonstrated from two contrasting counties. The results show Garfield County (agricultural) has higher ETa values than Oklahoma County (urban) for all land cover types except open water bodies.

Roost Sites of Allen's Lappet-browed Bats (Idionycteris phyllotis)

We report characteristics of maternity roosts of Allen's lappet-browed bat (Idionycteris phyllotis) at the northernmost extent of its range. In summer 2004, three female I. phyllotis were fitted with radiotransmitters and followed to three roosts in cracks of the same cliff face within Grand Staircase-Escalante National Monument, Kane and Garfield counties, Utah. There were ≥15 bats in the three roosts, which were on a large northwest-facing cliff, in the eastern side of a small box-canyon. Piñon-juniper (Pinus-Juniperus) woodland was on ridge tops and bottoms of canyons, which were ca. 1,800 m elevation with mature to old-growth woodlands. Roosts were in the top one-half of the cliff face, which was tall and highly fractured, with a large talus slope at the base.

First Record of Preble's Shrew (Sorex preblei) in the Northern Columbia Basin, Washington

The natural history of Sorex preblei (Preble's Shrew) and its distribution across western North America are poorly understood. Throughout its range, new records are of high interest (for example, Long and Hoffman 1992; Kirkland and Findley 1996; Hendricks and Roe del 2002; Shohfi and others 2006). Recently, Na gorsen and others (2001) expanded the docu mented distribution of S. preblei to include the Okanagan region of south-central British Co lumbia. Although S. preblei has been captured at numerous locations in eastern Oregon (Verts and Carraway 1998), the only previous records in Washington were from the Blue Mountains (Garfield County) in the southeast corner of the state (Armstrong 1957; Johnson and Cassidy 1997). Nagorsen and others (2001) speculated that the apparent absence of this species in the Columbia Basin of Washington was partially an artifact of insufficient sampling. Here, we re port a record of S. preblei from this gap in its documented distribution.

Industry Issues: Putting the Heat on Gas

Industry Issues: Putting the Heat on Gas

Mammalian Faunal Dynamics During the Last 1.8 Million Years of the Cretaceous in Garfield County, Montana

This study provides an analysis of biotic change in successive mammalian communities during the last 1.8 million years of the Cretaceous (67.3–65.58 Ma) from the Hell Creek Formation in Garfield County, Montana. Results show changes in relative abundances of species, mean individual body size, and to some extent taxonomic composition through the Hell Creek Formation. These results are interpreted as “normal” mammalian responses to fluctuating temperatures during the latest Cretaceous. By contrast, the extinction of 22–27 mammalian species at or near the Cretaceous-Tertiary (K-T) boundary cannot be explained by the coincident cooling interval alone. At the scale of temporal resolution available, these fossil data are inconsistent with an extended gradual pattern of extinction (linear-response) and are most consistent with either a non-linear response pattern for the K-T extinction, resulting from the accumulated stress of multiple long- and short-term environmental perturbations (e.g., climate change, sea-level regression, volcanism, an extraterrestrial impact), or a single, short-term cause (an extraterrestrial impact).

Profiles in Research

Ledyard R. Tucker was born on September 19, 1910 to Sarah and Reese Tucker in Glenwood Springs, Colorado. He attended the Glenwood Springs elementary school and the Garfield County high school, graduating in 1928. He attended the University of Colorado from 1928 to 1933, including two six-month stints with a construction company in San Antonio, Texas. After graduating with a degree in electrical engineering in the midst of the depression, Tucker drifted from Colorado to Texas to Chicago looking for work. He was fortunate to obtain a WPA position as a research assistant to Professor L. L. Thurstone at the University of Chicago, where he started working in January 1934. Professor Thurstone immediately recognized Tucker's analytical and spatial talents and encouraged him to pursue further education, which Tucker did, first in economics and then in psychology. He continued to work as Thurstone's research associate and as an instructor at the University of Chicago, completing his Ph.D. in 1946. He was widely regarded as Thurstone's most prominent proteg6. In 1944, Tucker took a position in statistics with the College Entrance Examination Board. In 1947, when the Educational Testing Service was founded, Tucker became the first Director of Statistical Analysis. In 1952, he switched to the research department where he stayed until 1960. He was a lecturer in psychology At Princeton University from 1948 until 1960. Tucker moved to academia full time in 1960 when he joined the University of Illinois where he held appointments as Professor of Psychology and Professor of Educational Psychology. In 1962, he was appointed Professor in the University of Illinois Center for Advanced Studies, a prestigious appointment. Included among the many awards and honors he has received are the ETS Distinguished Service to Measurement Award (1981), the American Psychological Association's (APA) Distinguished Scientific Contribution Award (1987), the highest honor awarded by APA, and the Lifetime Achievement Award from Division 5 of APA (1997). Tucker also served as President of the Psychometric Society and of Division 5 of APA. When Tucker retired in 1979, he was viewed as a pioneer and an intellectual giant in the field of psychometrics from the 1940s to the 1980s. He made major foundational contributions to the development of statistical methods in the areas of test theory, factor analysis, and scaling that are still clear and relevant today. And he continued to consult well into his 70s.

A NEW SPECIES OF CERCERIS FROM SOUTHERN UTAH (HYMENOPTERA: SPHECIDAE, PHILANTHINAE)

Abstract A new species, Cerceris escalante, is described from Kane and Garfield counties, Utah.

Carbon Isotope Excursion in Atmospheric CO2 at the Cretaceous-Tertiary Boundary: Evidence from Terrestrial Sediments

Abstract A −1.5‰ to −2‰ carbon isotope excursion immediately above the clay layer that defines the Cretaceous-Tertiary (K/T) boundary has been reported in marine sediments world wide. This paper reports a similar −1.5‰ to −2.8‰ carbon isotope excursion recorded by C3 land plants from three temporally-controlled, stratigraphically-constrained terrestrial sections in the Western Interior of North America (Garfield County, Montana, and Slope County, North Dakota). Carbon isotope measurements of bulk sedimentary organic carbon were well-correlated with those of isolated plant cuticle, suggesting that the terrestrial organic carbon signature in these sediments parallels that of plant cuticle. Carbon isotope signatures were also independent of rock type and depositional environment, showing that the carbon isotope signature of plants, although altered, is not biased taphonomically. Because the signature in terrestrial facies records the isotope composition of paleoatmospheric CO2, this record—combined with that...

Carbon Isotope Excursion in Atmospheric CO 2 at the Cretaceous-Tertiary Boundary: Evidence from Terrestrial Sediments

Other| August 01, 2000 Carbon Isotope Excursion in Atmospheric CO2 at the Cretaceous-Tertiary Boundary: Evidence from Terrestrial Sediments NAN CRYSTAL ARENS; NAN CRYSTAL ARENS 1Department of Integrative Biology, University of California, Berkeley, CA 94720 Search for other works by this author on: GSW Google Scholar A. HOPE JAHREN A. HOPE JAHREN 2Department of Earth and Planetary Sciences, Johns Hopkins University, Baltimore, MD 21218 Search for other works by this author on: GSW Google Scholar PALAIOS (2000) 15 (4): 314–322. https://doi.org/10.1669/0883-1351(2000)015<0314:CIEIAC>2.0.CO;2 Article history accepted: 02 May 2000 first online: 03 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation NAN CRYSTAL ARENS, A. HOPE JAHREN; Carbon Isotope Excursion in Atmospheric CO2 at the Cretaceous-Tertiary Boundary: Evidence from Terrestrial Sediments. PALAIOS 2000;; 15 (4): 314–322. doi: https://doi.org/10.1669/0883-1351(2000)015<0314:CIEIAC>2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyPALAIOS Search Advanced Search Abstract A −1.5‰ to −2‰ carbon isotope excursion immediately above the clay layer that defines the Cretaceous-Tertiary (K/T) boundary has been reported in marine sediments world wide. This paper reports a similar −1.5‰ to −2.8‰ carbon isotope excursion recorded by C3 land plants from three temporally-controlled, stratigraphically-constrained terrestrial sections in the Western Interior of North America (Garfield County, Montana, and Slope County, North Dakota). Carbon isotope measurements of bulk sedimentary organic carbon were well-correlated with those of isolated plant cuticle, suggesting that the terrestrial organic carbon signature in these sediments parallels that of plant cuticle. Carbon isotope signatures were also independent of rock type and depositional environment, showing that the carbon isotope signature of plants, although altered, is not biased taphonomically. Because the signature in terrestrial facies records the isotope composition of paleoatmospheric CO2, this record—combined with that from marine sections—offers additional insight into changes in carbon cycling underlying the K/T negative carbon isotope excursion. For example, radiometric age determinations from the Hell Creek Road locality in Montana bracket the atmospheric carbon isotopic recovery between 65.00 ± 0.05 Ma and 65.16 ± 0.04 Ma. This reflects a more rapid recovery for the terrestrial biosphere than for that of the marine realm, perhaps due to lower extinction rates in land plants than in marine primary producers. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Sandstone-Body and Shale-Body Dimensions in a Braided Fluvial System: Salt Wash Sandstone Member (Morrison Formation), Garfield County, Utah

Excellent three-dimensional exposures of the Upper Jurassic Salt Wash Sandstone Member of the Morrison Formation in the Henry Mountains area of southern Utah allow measurement of the thickness and width of fluvial sandstone and shale bodies from extensive photomosaics. The Salt Wash Sandstone Member is composed of fluvial channel fill, abandoned channel fill, and overbank/flood-plain strata that were deposited on a broad alluvial plain of low-sinuosity, sandy, braided streams flowing northeast. A hierarchy of sandstone and shale bodies in the Salt Wash Sandstone Member includes, in ascending order, trough cross-bedding, fining-upward units/mudstone intraclast conglomerates, single-story sandstone bodies/basal conglomerate, abandoned channel fill, multistory sandstone bodies, and overbank/flood-plain heterolithic strata. Trough cross-beds have an average width:thickness ratio (W:T) of 8.5:1 in the lower interval of the Salt Wash Sandstone Member and 10.4:1 in the upper interval. Fining-upward units are 0.5-3.0 m thick and 3-11 m wide. Single-story sandstone bodies in the upper interval are wider and thicker than their counterparts in the lower interval, based on average W:T, linear regression analysis, and cumulative relative frequency graphs. Multistory sandstone bodies are composed of two to eight stories, range up to 30 m thick and over 1500 m wide (W:T > 50:1), and are also larger in the upper interval. Heterolithic units between sandstone bodies include abandoned channel fill (W:T = 33:1) and overbank/flood-plain deposits (W:T = 70:1). Understanding W:T ratios from the component parts of an ancient, sandy, braided stream deposit can be applied in several ways to similar strata in other basins; for example, to (1) determine the width of a unit when only the thickness is known, (2) create correlation guidelines and maximum correlation lengths, (3) aid in interpreting the controls on fluvial architecture, and (4) place additional constraints on input variables to stratigraphic and fluid-flow modeling. The usefulness of these types of data demonstrates the need to develop more data sets from other depositional environments.

Evaluating the relationship of autumn buttercup (Ranunculus acriformis var. aestivalis) to some close congeners using random amplified polymorphic DNA

Autumn buttercup, an endangered endemic of wet, saline meadows in Garfield County, Utah, is treated differently in various taxonomic references now in use in the region. The taxon is currently listed as endangered by the United States Fish and Wildlife Service under the name Ranunculus acriformis var. aestivalis L. Benson. Others treat it as R. acris var. aestivalis (L. Benson) Welsh. In an attempt to resolve the taxonomical disagreements and to quantitatively describe the genetic uniqueness of this taxon, putative close relatives of the autumn buttercup, namely R. occidentalis (Nevada County, CA), R. acris (introduced from Europe and now growing wild in Rich and Cache counties, UT), R. acriformis var. montanensis (Lincoln County, WY), R. acriformis var. acriformis (Emery and Sanpete counties, UT), and R. acriformis var. aestivalis were collected and analyzed using random amplified polymorphic DNA (RAPD) genetic markers amplified from total cellular DNA extracts. Twenty‐three decanucleotide primers of arbitrary sequence were used for DNA amplification; over 350 markers were generated. The genetic marker data were analyzed using similarity coefficients and parsimony. Based on the results of those analyses and on a review of ecological and morphological characteristics, we have elevated the autumn buttercup to species rank as Ranunculus aestivalis (Benson) Van Buren &amp; Harper.

40Ar/39Ar dating and magnetostratigraphic correlation of the terrestrial Cretaceous–Paleogene boundary and Puercan Mammal Age, Hell Creek – Tullock formations, eastern Montana

The recovery and subsequent prolific radiation of mammals in the northern Western Interior of North America following the Cretaceous–Paleogene (K–P) boundary is well documented in rocks attributed to the Puercan Land Mammal Age. The most complete Puercan record is that of the Tullock Formation, which crops out widely in Garfield and McCone counties, eastern Montana. The Tullock Formation overlies the dinosaur-bearing Hell Creek Formation and consists of a stratigraphic series of channel and overbank deposits from which well-preserved Puercan faunas have been collected. These channel deposits are typically bracketed by widespread coal beds. The IrZ- and Z-coals mark the base of the Puercan at the K–P boundary as defined by the highest appearing local occurrences of in situ dinosaur fossils, the highest stratigraphic occurrence of Cretaceous pollen, and an anomalously high concentration of the element iridium (Ir). The IrZ-Coal is overlain sequentially by the Z-, HFZ-, Y-, W-, and U-coals.Fossil vertebrates of earliest Puercan age (Pu0 or Pu1) occur in sandstones of the Hells Hollow Channel between the IrZ-and HFZ-coals in Garfield County and below the Z-Coal in sandstones of the Bug Creek Channels, McCone County. Late Puercan (Pu2/3) fossil vertebrates are abundant between the Y- and W-coals in sandstones of the Garbani Channel in Garfield County, and in sandstones of the Purgatory Hill quarry in McCone County. Earliest Torrejonian (To1?) fossil vertebrates of the Mosquito Gulch localities, Garfield County, occur in sandstones of the Farrand Channel between the W- and U-coals.Magnetostratigraphies developed on sections at Billy Creek, Hauso Flats, Biscuit Butte, Bug Creek, and Purgatory Hill indicate that the IrZ- and Z-coals, the fossil vertebrate-bearing sandstones of the Hells Hollow and Bug Creek channels, and rocks up to midway between the HFZ- and Y-coals are contained in a zone of reversed polarity, correlated here with chron C29r. The Y through W coals, as well as the fossil vertebrate-bearing sandstones of the Garbani Channel and Purgatory Hill, are contained in an overlying zone of normal polarity, correlated with chron C29n. Rocks immediately above the W-Coal through the U-Coal, which include the Farrand Channel, are in a zone of reversed polarity, correlated here with chron C28r. The top of the section, just above the U-Coal, is in the uppermost zone of normal polarity, tentatively correlated here with the base of chron C28n.40Ar/39Ar dating of single crystals of sanidine separated from bentonites in the IrZ-, Z-, HFZ-, W-, and U-coals has yielded high-precision ages with standard errors of 0.1%. Replicate analyses of single crystals of sanidine yield weighted mean ages for bentonites in the following coals: IrZ, 65.16 ± 0.04 Ma; Z, 65.01 ± 0.03 Ma; HFZ, 64.77 ± 0.06 Ma; W, 64.11 ± 0.02 Ma; and U, 63.90 ± 0.04 Ma. These ages provide detailed calibration of Puercan through earliest Torrejonian (PuO, Pu1, Pu2, Pu3, and ?To1) land mammal ages and provide crucial calibration for the nonmarine K–P boundary and the Early Paleogene portion of the geomagnetic polarity time scale.