Northern Arkansas Research Articles

Comparisons of Twelve Freshwater Mussel Bed Assemblages Quantitatively Sampled at a 15-year Interval in the Buffalo National River, Arkansas, USA

Historically, 23 freshwater mussel species have been documented from the Buffalo National River (BNR), a 246 km, free-flowing river in northern Arkansas. The potential threats to BNR include land use/land cover changes, eutrophication, recreation, physical habitat changes, and various climate change-related effects. Twelve quantitative mussel bed sites were established and then sampled using a stratified random sampling protocol to evaluate the long-term changes between 2006 and 2020–2021 in population and assemblage characteristics. We compared (1) overall mussel bed persistence, sampling confidence levels and study-wide relative abundances, and compared species’ size and size-frequency distributions; (2) 10 overall site assemblage variables using paired t-tests; (3) site-level mean density, richness, and diversity indices using pair-wise Mann–Whitney U statistics; and (4) assemblage composition using Non-Metric Multidimensional Scaling. The major findings included the following: (1) sampling efforts based on a targeted 80% confidence level appears relatively robust, (2) BNR mussel assemblage composition and structure were relatively stable (however, small mussel bed persistence is a concern), (3) 7 of 23 sites were outliers based on freshwater mussel composition and habitat characteristics, and (4) assemblage composition changed with three species declining (Actinonaias ligamentina, Lasmigona costata, and Ptychobranchus occidentalis) and four species increasing (Cambarunio hesperus, Cyclonaias tuberculata, Eurynia dilatata, and Venustaconcha pleasii) between monitoring events.

Apparent annual survival of female eastern small-footed bats (Myotis leibii) roosting in Arkansas bridges

Abstract The Eastern Small-footed Bat (Myotis leibii) inhabits mountainous areas of the eastern United States and generally roosts in cliff faces and talus slopes. However, the difficulty of accessing these sites has limited research on this species. We studied survival rates of eastern small-footed bats by capturing bats roosting in crevices between sections of concrete guardrails on bridges in the Ozark mountains of northern Arkansas from 2014 to 2021. We accumulated 1,413 bat captures (1,050F; 363M) of 283 individual females and 198 individual males sampled over 8 years and determined apparent annual survival of female bats using Cormack–Jolly–Seber survival models. Only 1 of 30 bats tested positive for the presence of Pseduogymnoascus destructans, a fungus causing white-nose syndrome (WNS) which is responsible for significant declines in populations of some North American bat species, when all maternity colonies were sampled in the spring of 2019. Overall apparent annual survival of all females was 0.643, with first-year juvenile survival of 0.472 and adult (ages 1–6) survival of 0.744, approximately 58% greater than first-year survival. Apparent annual survival did not differ greatly among the sites or among years. We found no significant decline or increase in overall number of bats among all sites during the 8 years of study. Stability in both the number of bats encountered and their survival rates suggests that the impact of WNS on these colonies has been marginal.

Insights on the Formation Conditions of Manganese Oxides from Crimora, VA (USA)

Many regions of the United States contain manganese deposits economically valuable in New England, Appalachian, and Piedmont regions in the Eastern United States, in Northern Arkansas, and, to a small extent, in Central–Western California. Mn oxide/hydroxide (commonly referred to as Mn oxide minerals) are found in a wide variety of geological settings and occur as fine-grained aggregates, veins, marine and freshwater nodules and concretions, crusts, dendrites, and coatings on rock surfaces (e.g., desert varnish). How manganese oxides form and what mechanisms determine which oxides are likely to form are limited and still debated. This paper focuses on Mn oxides collected at the southern bound of the abandoned open-pit site called Crimora Mine (Augusta County, Virginia). This study uses mineralogical and chemical features to shed light on the origin of manganese deposits in Crimora along the western foot of the Blue Ridge in South–West Virginia. We report the first detailed study on the genesis of the Crimora manganese deposit conducted since the mine was closed in the 1950s. Crimora Mine sample is dark black fine- to medium-grained round and oblong nodules coated with a fine-grained intermix of yellowish earthy limonite, clays, and quartz. Scanning electron microscopy (SEM) revealed that the Crimora Mn-oxides exhibit concentric layering, breccia-like matrices, and veins. X-ray powder diffraction (XRPD) identified the set of Mn minerals as hollandite and birnessite. The concentration and range of dissolved chemical species in freshwater, seawater, and hydrothermal depositional fluids impart a geochemical signature to the Mn-oxides, providing a diagnostic tool to shed light on their genetic origin. Inductively coupled plasma optical emission spectroscopy (ICP-OES) analysis of the Crimora manganese oxides shows Mn, Fe, and Ti, as well as trace elements such as Co, Ba, Y, Zn, Cr, Ni, Tl, La, V, and Li. A bivariate analysis based on the geochemical correlation of Mn and other common substituting cations (e.g., Fe, Co, Ti) shows a mixed genesis in different environments with varying biological and sedimentary supergene (freshwater and marine) conditions. These data suggest that the Mn-rich deposit in Crimora, VA, was formed in a continental margin environment of surficial deposits and reprecipitated in mixed biogenic and supergene conditions.

Modeling migration and movement of gray bats

AbstractManaging landscapes for migratory species is challenging when migratory movement patterns are unknown. Researchers have collected sufficient data to understand summer and winter habitat use for federally listed bats, but movement between these habitats in spring and fall has not been studied extensively. In addition, movement within summer habitat is less well understood than the roosting requirements. To initiate a preliminary understanding of movement patterns of gray bats (Myotis grisescens), we gathered all occurrence and band recovery data available within the range of the species to model movement. By weighting the pathways using the population of winter and summer locations (i.e., cave roosts), we created a heat map demonstrating the likelihood of landscape use by gray bats including nightly foraging, migration, and roost switching. The resulting map highlighted 2 major areas of use during spring and fall migration: 3 high likelihood pathways through central Tennessee and 1 primary migration route between northern Arkansas and central Missouri, USA. Although future data could influence the accuracy of this map, the representation in its current form can be used to anticipate bat presence when considering industrial development such as wind turbine siting.

Kiricephalus coarctatus (Pentastomida: Porocephalidae) from Orange-Striped Ribbonsnake, Thamnophis proximus proximus (Serpentes: Colubridae), from Arkansas, U.S.A., with a Summary of Ophidian Hosts of the Western Hemisphere

Two adult orange-striped ribbonsnakes, Thamnophis proximus proximus, were collected from northern Arkansas and examined for helminths. A single snake harbored 4 specimens of the pentastomid, Kiricephalus coarctatus. We document a new host as well as a new distributional record for the parasite. This is only the second time a species of pentastomid has been reported from the state in any host. A summary of ophidian hosts of K. coarctatus from the Western Hemisphere is included.

Late Paleozoic Flexural Extension and Overprinting Shortening in the Southern Ozark Dome, Arkansas, USA: Evolving Fault Kinematics in the Foreland of the Ouachita Orogen

AbstractFaults and folds on the southern flank of the Ozark dome in northern Arkansas, USA, record flexural extension in a foreland area followed by shortening in response to the late Paleozoic Ouachita orogeny. Map‐scale structures and an analysis of fault‐slip data collected systematically during geologic mapping demonstrate that most deformation in the area accommodated north‐south extension as the southern margin of Laurentia was flexed beneath the thrust load of the Ouachita belt, probably during Middle Pennsylvanian. Extension was concentrated in northeast‐ and west‐northwest‐trending structural zones having sets of discontinuous, often en echelon normal and strike‐slip faults and associated monoclinal folds. Reactivation of basement weaknesses that underlie these zones is indicated by their close match to oblique‐rift models in which both the proportions of normal and strike‐slip faulting and the internal extension directions vary with orientation of the zones. Subsequent propagation of north‐south Ouachita shortening into the foreland formed small‐offset strike‐slip and sparse reverse faults that overprinted older extensional structures. Strike‐slip faults were concentrated in reactivated northeast‐trending structural zones. In two areas, reverse faults and local anticlines were developed in the footwalls of older normal faults, both near intersections of northeast‐ and west‐northwest‐trending structural zones. These are interpreted as areas of incipient inversion due to compressional stress concentrations at fault‐block corners. Spatial overlap of areas of north‐south shortening and fluid flux marked by silicification or lead‐zinc mineralization indicates that regional fluid flow of brines was coeval with and may have enhanced inversion during Late Pennsylvanian to early Permian.

Blanket NOP rules and regional realities: from the field

AbstractThere are fewer Certified Organic producers in the Mid-South US (southern half of Missouri, western Kentucky and Tennessee, northern Arkansas and eastern Oklahoma) than in other regions of the country such as the Upper Midwest, West Coast, or Northeastern US. Taus et al. (2013) The Professional Geographer 65, 87–102, posit that these clusters suggest regional characteristics impact adoption of organic agriculture and admit that regional studies lack consensus on the role of factors that drive adoption. This paper seeks to understand if there are regionally distinct challenges and opportunities for organic production in the region. Fourteen certified organic producers in Missouri were interviewed and areas of challenges and opportunities specific to their certification were identified within the three a priori themes of (1) biophysical characteristics, (2) marketing infrastructure and (3) financial feasibility. We suggest directions for future policy support from the National Organic Program (NOP) and bolstered feedback structures within the National Organic Standards Board to address regional disparities.

The Effect of an Insectivorous Lizard Predator (Crotaphytus collaris) on Ozark Glade Orthopteran Assemblages

Insectivorous lizards can alter arthropod community structure and composition. Collared lizards (Crotaphytus collaris) are believed to be keystone predators for Ozark glade grasshopper (Orthoptera) communities by increasing species richness on smaller glades. However, the interaction between collared lizard presence and glade area on orthopteran species richness has been inconsistent between studies on glades in southeastern Missouri. In this study, we explored the effects of collared lizard presence on orthopteran abundance, diversity, and assemblage composition in Ozark glades located in northern Arkansas. We found the presence of predatory collared lizard populations significantly affected orthopteran assemblage composition. However, the presence of collared lizards did not affect orthopteran abundance or diversity. Additionally, there were no interaction effects between collared lizard presence and glade area on orthopteran assemblages. We did find that month had the most consistent effect on orthopteran abundance, diversity, and assemblage composition. These results contrast with other studies that indicate collared lizards influence orthopteran species richness on other glade communities within the region. In this study, seasonal effects, glade area, and unmeasured bottom-up effects appear more important for determining orthopteran diversity than predation. Our results provide further evidence that the strength of top-down effects can vary across a predator's range and could have implications for glade restoration plans in the region.

Illumina Short-Read Sequencing of the Mitogenomes of Novel Scarites subterraneus Isolates Allows for Taxonomic Refinement of the Genus Scarites Fabricius 1775, within the Carabidae Family.

Simple SummaryGround beetles (Carabidae) have important ecological functions and serve as food, biological pest control, and models in biological research. Although there are over 40,000 ground beetle species worldwide, only a small fraction of those has genomic information currently available, which limits their classification and understanding of diversity. Since next-generation genome sequencing has become more mainstream, we used Illumina short-read sequencing to obtain complete mitogenomes from two Scarites beetles that we collected ourselves in Nebraska and Arkansas. Scarites are large ground beetles that resemble tropical beetles with a big head and large mandibles, and their role as predator and prey helps maintain sustainability in local ecosystems. This straightforward sequencing and analysis was found to be accurate and sufficient to help classify these isolates to the subspecies level. This is the first report of mitogenomes for Scarites subterraneus and only the second in that genus. This method is easily applicable to more beetle species and can be used to increase our understanding of beetles worldwide.We sequenced the complete mitogenomes, 18S and 28S rRNA of two new Scarites isolates, collected in Eastern Nebraska and Northern Arkansas (US). Based on molecular sequence data comparison and morphological characteristics, the new isolates were identified as a subspecies of Scarites subterraneus Fabricius 1775, for which we propose the subspecies names ‘nebraskensis’ and ‘arkansensis’. The new 18S and 28S rRNA sequences were found to be 99% and 98% identical to Scarites subterraneus. There are no other Scarites 18S or 28S rRNA sequences in the Genbank database, however, phylogenetic analysis of the Cox1 genes showed S. vicinus Chaudoir, 1843, and S. aterrimus Morawitz, 1863, as the closest relatives. This is the first report of a mitogenome for S. subterraneus, and only the second mitogenome for that genus. The nucleotide sequence identity between the mitogenomes of the two isolates is 98.8%, while the earlier sequenced S. buparius Forster 1771 mitogenome is more distantly related, with only 90% (to ssp. nebraskensis) and 89% (to ssp. arkansensis) overall nucleotide sequence identity. These new mitogenomes, and their phylogenetic analysis, firmly establish the position of Scarites on the Carabidae family tree and further refine the genus. In addition to the molecular data provided for the Scarites species, this approach also allowed us to identify bacterial and viral signatures for Providencia, Myroides, Spiroplasma, and a giant Nucleocytoviricota virus, associated with the Scarites species. We hereby present a simple and efficient protocol for identification and phylogenetic analysis of Scarites, that is applicable to other Coleoptera, based on total DNA extraction and Illumina short-read Next-Gen sequencing.

An Analysis of the 3 May 2020 Low-Predictability Derecho Using a Convection-Allowing MPAS Ensemble

Abstract This study analyzes the low short-range predictability of the 3 May 2020 derecho using a 40-member convection-allowing Model for Prediction Across Scales (MPAS) ensemble. Elevated storms formed in south-central Kansas late at night and evolved into a progressive mesoscale convective system (MCS) during the morning while moving across southern Missouri and northern Arkansas, and affected western and middle Tennessee and southern Kentucky in the afternoon. The convective initiation (CI) in south-central Kansas, the organization of a dominant bow echo MCS, and the MCS maintenance over Tennessee were identified as the three main predictability issues. These issues were explored using three MPAS ensemble members, observations, and the Rapid Refresh analyses. The MPAS members were classified as successful or unsuccessful with regard to each predictability issue. CI in south-central Kansas was sensitive to the temperature and dewpoint profiles in low levels, which were associated with greater elevated thermodynamic instability and lower level of free convection in the successful member. The subsequent organization of a dominant bowing MCS was well predicted by the member that had more widespread convection in the early stages and no detrimental interaction with other simulated convective systems. Last, the inability of MPAS ensemble members to predict the MCS maintenance over western and middle Tennessee was linked to a dry bias in low levels and much lower thermodynamic instability ahead of the MCS compared to observations. This case demonstrates the challenges in operational forecasting of warm-season derecho-producing progressive MCSs, particularly when ensemble numerical weather prediction guidance solutions differ considerably.

Analyzing Time-Energy Constraints to Understand the Links between Environmental Change and Local Extinctions in Terrestrial Ectotherms.

AbstractAccelerated extinction rates have prompted an increased focus on the interplay between environmental change and species response. The effects of environmental change on thermal opportunity are typically considered through a climate change context. However, habitat alteration can also have strong effects on the thermal environment. Additionally, habitat alteration is considered a leading factor of species extinction, yet few studies address the influence of habitat alteration on thermal opportunity and time-energy budgets in at-risk species. Here, we show the strong effects that habitat degradation can have on thermal opportunity, time-energy budgets, and life history demographics of local populations. In the Ozark Mountains of northern Arkansas, woody vegetation encroachment has resulted in a shift in life history traits that appears to play an important role in recent extirpations of eastern collared lizards (Crotaphytus collaris). Populations in degraded habitats experienced a decline in thermal opportunity and less time at body temperatures (time at Tb) suitable for digestion compared with those in intact habitats. We used our data to model the effect of reduced time at Tb on the net assimilated energy available for growth and reproduction. Our model predicts an ∼46% decline in the annual fecundity of individuals, which is similar to empirical observations of reproduction of C. collaris populations in degraded habitats (~49%). We conclude that C. collaris in degraded habitats experienced reduced growth and reproduction primarily as a result of constrained thermal opportunity leading to a decline in digestive processing rates. Our study applies an underappreciated approach to identify the biophysical and time-energy effects of habitat alteration.

Weatherscapes

The Ozark Mountains stretch from central Missouri into northern Arkansas and northeastern Oklahoma, as well as a touch of southeastern Kansas. Influenced by the dry air of the Great Plains, Canadia...

P1 Assessing Food Offerings Among Emerging Food Outlets in Northern Arkansas

<h3>Background</h3> Limited study of the availability of food in nontraditional food stores (Pharmacy and convenience stores) has left a gap in the understanding of the food environment in Arkansas. Recent corporate action among nontraditional food stores suggests that consumers are looking to these stores as sources of healthier food. <h3>Objective</h3> The question that guided this work asked, "Are there differences in food offerings among non-traditional food outlets, such as CVS and Walgreens, and how do those offerings compare to the offerings of convenience stores, in Arkansas?" Understanding differences among these food store types may be useful for subsequent efforts to improve equitable access to healthy food across Arkansas. <h3>Study Design, Setting, Participants</h3> This study used an observational design to assess offerings in non-traditional food outlets. The Nutrition Environment Measures Survey (NEMS) assessment tool was used to document and score the availability of food products in 54 stores in the northern half of Arkansas, including 27 pharmacy stores and 27 convenience stores within a 2.5 mile radius. <h3>Measurable Outcome/Analysis</h3> The NEMS tool gathered availability data across 13 measures, including: fruit, vegetables, dairy products, meat products, frozen dinners, baked goods, bread, beverages, chips and snacks, and cereal. <h3>Results</h3> Pharmacy stores had a higher mean availability score (x̅ = 19.0) than convenience stores (x̅ = 7.2). A paired sample t test indicated that the difference in mean availability score between the store types was not likely due to chance [t(26) = 16.01, <i>P</i> < .001]. <h3>Conclusions</h3> These findings suggest that pharmacy stores offer a healthier supply of foods as compared to convenience stores. Nontraditional food stores may be important intervention sites as consumers look to these stores for an increasing proportion of their food purchases. Further study may help to uncover differences in rural and urban food supply in Arkansas, and may have positive consequences for better understanding best practices for increasing access to food across the state.

&lt;p&gt;&lt;strong&gt;Geographic variation in a restricted-range endemic dragonfly &lt;em&gt;Gomphurus&lt;/em&gt; &lt;em&gt;ozarkensis&lt;/em&gt; (Odonata: Gomphidae), with description of a new subspecies&lt;/strong&gt;&lt;/p&gt;

The geographic distribution of Gomphurus ozarkensis (Westfall, 1975), a species described to science only four decades ago, is confined to a four-state area in the central United States: southeastern Kansas, eastern Oklahoma, western and northern Arkansas, and southern Missouri. Its small range has led some to classify it a species of conservation concern. We examined geographic variation in the species, which despite its small range exists in three distinct subpopulations: one in the Ouachita Mountains of western Arkansas and southeastern Oklahoma; one on the Ozark Plateau of northeastern Oklahoma, southeastern-most Kansas, southern Missouri, and northern Arkansas; and one in the Osage/Flint hills of southeastern Kansas and northeastern Oklahoma. Clinal variation is evident in the extent of yellow on the terminal abdominal segments and the extent to which certain thoracic stripes are fused. A population in a separate watershed basin in the southern Osage Hills of Oklahoma is taxonomically distinct, with some phenotypic characters tending toward G. externus (Hagen, 1858). We describe this population as a new subspecies of G. ozarkensis.

264 Using bermudagrass baleage to increase stocking rates of fall wheat pasture

Abstract The objectives of the current research were to determine the effect of offering ad libitum bermudagrass (Cynodon dactylon) round bale silage on performance and stocking rate of growing steers grazing wheat pasture in northern Arkansas. Eighteen, 1.6-hectare wheat fields were no-till planted to soft-red winter wheat in the first week of September (101 kg wheat seed/ha; cv. Jamestown) and were stocked to growing steers on October 23, 2018 at 2.5 steers/ha without bermudagrass baleage (CONTROL, n = 6) or with ad libitum bermudagrass baleage stocked at 2.5, 3.75, or 5.0 steers/ha (BALE2.5, BALE3.75, and BALE5.0, respectively; n = 4 pastures/treatment). The bermudagrass baleage was harvested in the late summer of 2018 and contained 40%DM, 14.3% CP, 70% NDF, 39% ADF, and 55% calculated TDN. Forage mass was 1,268 kg DM/ha (P ≥ 0.39) at the start of grazing and forage allowance (P &amp;lt; 0.01) was 2.25, 2.20, 1.62, and 1.27 kg forage DM/kg steer BW, respectively, at the start of grazing. Average daily gains of CONTROL (1.40 kg/d) did not differ (P = 0.36) from BALE2.5 (1.34 kg/d), but as stocking rate increased ADG decreased (P &amp;lt; 0.01) to 1.14 kg/d and 0.96 kg/d, for BALE3.75 and BALE5.0, respectively. As observed with ADG, gain per hectare and steer grazing-days per hectare did not differ (P ≥ 0.53) between CONTROL (340 kg/ha and 272 d/ha, respectively) and BALE2.5 (365 kg/ha and 272 d/ha, respectively), but each increased (P &amp;lt; 0.01) with increasing stocking rate, to 408 and 543 grazing d/ha for BALE3.75 and BALE5.0, respectively, and 467 and 524 kg BW gain/ha, respectively. The current research indicates that, even though individual animal performance decreases, stocking rates of wheat pasture for fall grazing stocker calves can be increased two-fold with up to 54% increase in BW gain/ha.

Interspecific Aggression between a Hoary Bat (Lasiurus cinereus) and a Tricolored Bat (Perimyotis subflavus) in Northern Arkansas

We observed interspecific aggression between a Hoary Bat (Lasiurus cinereus) and a Tricolored Bat (Perimyotis subflavus) along the Buffalo River in northern Arkansas in September 2016. The Hoary Bat presumably captured the Tricolored Bat and repeatedly bit its forearm and facial tissues while on the ground. The Tricolored Bat did not survive the encounter. Interspecific aggression has been observed in Hoary Bats previously and has occasionally been linked to rabies infection. Because of the circumstantial nature of our observation, we were unable to draw specific conclusions as to the nature of this behavior.

Spatial patterns of within-treeEnaphalodes rufulus(Coleoptera: Cerambycidae) attacks during outbreak conditions in the Ozark National Forest in Arkansas, United States of America

AbstractEnaphalodes rufulus(Haldeman) (red oak borer; Coleoptera: Cerambycidae) is a native wood borer that colonises and develops in oaks (QuercusLinnaeus; Fagaceae) across southeastern Canada and the eastern United States of America. It is rarely considered a pest because it normally occurs at low population density levels in stressed or dying oak trees. In the late 1990s and early 2000s there was a large, historically unique outbreak ofE.rufulusin the Ozark mountains of Arkansas and Missouri, United States of America. This outbreak provided an opportunity to investigate within-tree spatial distribution of attacks during unusually high insect population levels. Fifty trees from northern Arkansas were felled and destructively sampled. The locations of attack sites by femaleE.rufuluswere standardised across varying heights and diameters for comparison across trees. Attack sites showed a significant clustered pattern within trees. Attack sites were aggregated towards the lower and middle bole, and on the south-facing side of trees. This pattern has been seen in other insects, including wood borers, and is potentially related to differences in temperature. These patterns of ovipositional behaviour in outbreak situations have implications forE.rufulusresource partitioning and facultative intraguild predation among larvae.

A geochemical evaluation of the genetic relationship between Ouachita Mountains Paleozoic rocks and the Mississippi Valley-type mineralization in the southern Ozark Region, USA

The Pb and/or Zn deposits of the Tri-State and the Northern Arkansas Mississippi Valley-type (MVT) districts in the southern Ozark Region, located north of the Arkoma Basin and the Ouachita fold-thrust belt in North America, are genetically connected to the Pennsylvanian-Permian Ouachita orogeny. This orogenic event triggered a south-north topographic gradient flow of basinal brines, leaching metal-rich sediments en route. To establish whether the organic-rich shales of the Ouachita Mountains and the Ozark Region provided metals during the mineralization event, the Pb isotope compositions of the ores (sphalerite) have been compared to those of the sedimentary rocks (whole-rocks and leachates) of the Ouachita Mountains (Cambrian Collier Shale, Early Ordovician Mazarn Shale, Middle Ordovician Womble Shale, Late Ordovician Polk Creek Shale, Mississippian Stanley Shale, and Pennsylvanian Jackfork Sandstone) and the Ozark Plateau (Devonian/Mississippian Chattanooga Shale and Mississippian Fayetteville Shale). The Pb isotope compositions of ores in both districts show a broad and a linear range of isotopic values. This trend suggests mixing of Pb from two distinct end-member components. One end-member must be highly radiogenic, with Pb isotope ratios equal to or higher than the highest noticed value for ores. The other end-member must be less radiogenic, with Pb isotope ratios equal to or lower than the lowest value recorded for ores. The Pb isotope compositions of the analyzed whole rocks and leachates indicate that the best candidates for contributing the less radiogenic Pb to the ores are the sandstone members of the upper and middle Jackfork Sandstone and the lowermost section of the Chattanooga Shale.The depositional environment of the potential source rocks and their ability to sequester metals has been appraised using redox sensitive trace elements (Cd, Co, Cr, Cu, Mo, Ni, Pb, Th, U, V, Zn). Paleoredox proxies (e.g., enrichment factors of redox sensitive trace elements and V/V + Ni ratios) indicate deposition of the analyzed rocks mainly under anoxic and euxinic conditions, which are favorable for metal enrichment. However, oxic-suboxic conditions are also indicated by other geochemical proxies, suggesting a possible first order control of primary production that has resulted in an increased flux of organic matter. A disagreement in the redox conditions yielded by the paleoredox proxies has been noticed in several cases. This inconsistent behavior may be associated with several factors, including redox potential, pH, sulfur abundance, chemical availability, TOC values, and sediment provenance. The authigenic flux is the only fraction needed to unravel past redox conditions; however, the analyzed bulk sediments consist of authigenic, biogenic, and siliciclastic components, which may also have led to the observed disagreement in the redox conditions. Additional factors such as the basin geometry, the rates of sediment accumulation, the post depositional alteration processes associated with diagenesis and low-grade metamorphism during the Ouachita orogeny might have overprinted the depositional signatures.

Gray Bat Day Roosts in Concrete Barriers on Bridges during Migration

From 2013–2018 crevices between segments of concrete barriers on the sides of 164 bridges in northern Arkansas were surveyed for bat presence on 1270 occasions and gray bats (Myotis grisescens) were found roosting in 21 bridges. Bats used bridges over streams of all sizes and did not select crevices based on width. Seventy-two bats (62 males, 10 females) were captured alive and two were found dead. Most bats were observed in the spring (62, 84%) with some observations in fall (10, 14%), and two (3%) juvenile males were found in the summer. In 75% of observations, a single gray bat was detected on the bridge. However, there were surveys in which multiple gray bats or gray bats and other species used the same crevice. This research provides a better understanding of the migratory patterns of this federally-endangered species.

Geochemical investigations of the Woodford–Chattanooga and Fayetteville Shales: Implications for genesis of the Mississippi Valley–type zinc–lead ores in the southern Ozark Region and hydrocarbon exploration

The relationship between base metal deposits, especially Mississippi Valley–type (MVT) Pb–Zn deposits, and hydrocarbons is not well constrained. This is despite the fact that hydrocarbons generally occur in MVT deposits; the ores are emplaced in the same temperature range as hydrocarbon maturation and migration, and the deposits commonly occur in proximity to metal-rich black shales. Better understanding should lead to better exploration models for both hydrocarbons and MVT deposits. This connection is better understood with the help of Pb isotope patterns. Sphalerite Pb isotope compositions from the northern Arkansas and Tri-State mining districts and Woodford–Chattanooga and Fayetteville Shales were determined to assess the potential of shales as source rocks for the ore metals. The ores in both districts have a broad range of Pb isotope ratios and define linear trends, suggesting mixing of Pb from two distinct end members. Current results and previous depositional environment studies indicate the following: (1) shales deposited mainly under nonsulfidic anoxic conditions represent the less radiogenic end member, or (2) shales are the only source of ore metals. Given the array of organic molecules, each with their own thermochemical range, and the ways metals can be associated with them, the release of metals may cover varying ranges. Thus, the compositions of the released fluids would change through time and not have a single static composition, closely approximating the isotopic composition of the released metals at various times. Mineralization derived from a dynamically evolving fluid may show apparent end members, without the need to call on mixing of fluids from separate sources.