Big Horn County Research Articles

Geologic Map of the Spanish Point 7.5 Minute Quadrangle, Big Horn County Wyoming (Scale 1:24,000)

Geologic Map of the Spanish Point 7.5 Minute Quadrangle, Big Horn County Wyoming (Scale 1:24,000)

Geologic Map of the Woodrock Quadrangle, Sheridan and Big Horn Counties, Wyoming

Here we present the results of detailed (1:24,000 scale) mapping of the Woodrock 7.5 Minute Quadrangle Wyoming, which mainly consists of Archean basement rocks of the Laramide Bighorn uplift. Our focus was on the Archean geology of the Laramide age Bighorn uplift. Isotopic age determinations (U-Pb on zircon) were conducted at the University of Arizona LaserChron Center. Our work revealed the presence of four different components of the batholith. The oldest unit is a ~2880 Ma foliated Lookout Mountain Granodiorite that occurs in the southern part of the quadrangle in the vicinity of Bruce and Lookout Mountains. The ~2775 Black Mountain Tonalite occurs in the northeastern part of the quadrangle. The age of the Black Mountain Tonalite and Lookout Mountain Granodiorite overlap but the units are distinct in terms of structure and lithology so they were mapped separately. The central part of the quadrangle is underlain by the massive, ~2860 Ma Taylor Mine Granite. This unit is poorly exposed and variable in texture. The youngest unit is the ~2850 Ma Owen Creek Alkali Feldspar Granite, which occurs in the western part of the quadrangle. Mafic dikes of variable geometry, texture and age cross-cut the quartzofeldspathic rocks. Less than 25 m of poorly exposed Cambrian Flathead Sandstone occurs along the extreme western margin of the quadrangle. We discovered as much as 30 m of Oligocene White River Formation strata occur as terrace deposits along the western side of the Tongue River in the central part of the quadrangle. The White River strata are poorly exposed and consist of thin bedded tuffaceous sandstone and massive conglomerate that are light colors and include as clasts Paleozoic carbonate and Archean basement rocks. Less than 50 m of Pinedale-age glacial tills occur along the upper Tongue River in the southern part of the Quadrangle, forming hummocky, poorly-drained topography. Quaternary alluvium occurs along some of the larger streams.

First Report of Alfalfa Weevil (Coleoptera: Curculionidae) Resistance to Lambda-Cyhalothrin in Montana

Forage alfalfa (Medicago sativa L. [Fabales: Fabacae]) is a major agronomic crop grown nationally and Montana ranks highly in acres harvested. The alfalfa weevil (Hypera postica Gyllenhal [Coleoptera: Curculionidae]) is the primary defoliating pest that requires insecticide applications to prevent yield loss, particularly pyrethroid active ingredients (a.i.) that are both efficacious and cost-effective. Reports from commercial alfalfa producers in Big Horn County, MT, suggested local populations of alfalfa weevil had developed resistance to the pyrethroid a.i. lambda-cyhalothrin (type II pyrethroid). Chemical control is an important component of integrated pest management (IPM) of alfalfa weevil and the loss of pyrethroid a.i. as an effective tool would result in additional production costs. Two locations in southern Big Horn County and nine locations in four other Montana counties where resistance has not been reported were sampled and assayed for resistance to lambda-cyhalothrin. Populations from three counties were susceptible, the concentration causing 50% mortality (LC50) ranged from 0.02 to 0.10 µg/cm2. In contrast, populations from Big Horn County did not reach 50% mortality at the highest concentration of lambda-cyhalothrin tested (3.30 µg/cm2), indicating high levels of resistance have developed in these populations. A field trial in Big Horn County supported laboratory results of resistance; lambda-cyhalothrin at the highest label rate did not reduce alfalfa weevil populations. Additional bioassays suggest cross-resistance to zeta-cypermethrin (type II pyrethroid), but only partial cross-resistance to permethrin (type I pyrethroid).

A Geometric Morphometric Evaluation of Equid Tooth Shape at Natural Trap Cave, Wyoming

Natural Trap Cave is a sinkhole cave located in Big Horn County in northern Wyoming. The cave preserves many Quaternary taxa, including pollen and large carnivorous and herbivorous mammals such as various felids and ungulates. Many of these taxa went extinct in North America following the late Pleistocene megafaunal extinction. The cave was first excavated in the 1970s and 80s by teams from the University of Kansas and the University of Missouri, and more recently by teams from Des Moines University, The University of Adelaide, and The University of Rochester, along with a wide variety of volunteers. Specimens from this cave have been used to elucidate floral change in the area, disentangle ancient food webs, and extend the hypothesized range for Beringian wolves.Horses are the most common megafaunal group from this site, encompassing two genera: Equus and Haringtonhippus, the “New World stilt‐legged” horse, based on post‐cranial elements and mitochondrial DNA. Some recent studies have shown that horse taxa can be identified by tooth occlusal surface morphology. This study aims to test if isolated equid cheek teeth from Natural Trap Cave can be identified to the genus level, between Equus and Haringtonhippus using geometric morphometrics. 2D landmarks and sliding semi‐landmarks were taken around the periphery of a set of upper cheek teeth, including the areas of greatest curvature at the metastyle, mesostyle, parastyle, and around the protocone and post protoconal valley. Principal component analyses on known specimens do in fact separate Equus and Haringtonhippus, and this difference is statistically sigificant, with the primary difference being the width of the protocone. Additionally, molars and premolars also occupied significantly different areas of morphospace, opening up the possibility of identifying tooth position on unknown specimens as well. With the abundance of isolated horse teeth (either Equus or Haringtonhippus) from Natural Trap Cave, having a reliable means to distinguish between genera will allow us to better study the ecological differences between them and better understand the environment and faunal interactions in late Pleistocene Wyoming.Support or Funding InformationNSF EAR/SGP 1425059 (Natural Trap Cave Revisited: Ancient DNA, Climate and the Megafaunal Extinction) Julie Meachen, PI

Spherulitic dahllite of Duwi Formation phosphorite

Spherulitic dahllite structure is first once recorded microscopically by the present authors in the phosphorite rocks in Duwi Formation in Qusier–Safaga area, Red Sea. Petrographically the study dahllite in the Duwi Formation are authigenic in origin and deposited as a secondary mineral. It is subjected to the re-crystallization process that is one of diagenetic processes. It is resulting from re-crystallization of amorphous calcium carbonate–phosphate and collophane as well as by the weathering effect. Spherulitic dahllite indicated that the phosphorite rocks of the Duwi Formation seem to be subjected to the chemical weathering. Microscopically, the spherulitic dahllite occurs as colorless to pale brown color. It consists of subhedral to anhedral crystals and characteristic by plumose fibrous texture. The spherulitic dahllite structure in the phosphorite rocks at Duwi Formation—Late Cretaceous in Egypt are comparable to those at Thermopolis Formation (Upper Cretaceous), in Cody; as well as in Ishawooa, Park County, and in Big Horn County, Wyoming, United States.

First record of a middle Cenomanian caprinuloideid rudist (Hippuritida, Bivalvia) from Montana, USA, and its geographical and stratigraphical significance

The new caprinoidean rudist bivalve Cobbanicaprina bighornensis gen. nov., sp. nov. is described from the upper middle Cenomanian of Big Horn County, Montana, USA. Cobbanicaprina gen. nov. is closely related to Mexicaprina and differs from that form in the absence of an external ligamental groove. The presence of Cobbanicaprina gen. nov. in the middle Cenomanian indicates that the Caprinuloideidae did not become extinct at the top of the Albian and persisted into the Cenomanian. The presence of this specimen so far north in the Western Interior Seaway is attributed to a dried-out individual specimen having been transported post-mortem by currents.

Foaling rates in feral horses treated with the immunocontraceptive porcine zona pellucida

AbstractLocally abundant feral horses (Equus caballus) can rapidly deplete available resources. Fertility control agents present promising nonlethal tools for reducing their population growth rates. We tested the effect of 2 forms of the immunocontraceptive porcine zona pellucida (PZP) on foaling rates in 3 populations of feral horses in the western United States. A liquid form requiring annual boosters was administered at Little Book Cliffs Wild Horse Range, Mesa County (CO), and Pryor Mountain Wild Horse Range, Bighorn County (WY) and Carbon County (MT), and a time‐release pellet form designed to produce 2 yr of infertility was administered at McCullough Peaks Herd Management Area, Park County (WY). Average foaling rates (foals born/mare‐yr) from direct observation of untreated and treated female horses (mares), 2004–2008, were 60.1% (n = 153 mare‐yr) versus 6.6% (n = 91 mare‐yr) at Little Book Cliffs, and 62.8% (n = 129 mare‐yr) versus 17.7% (n = 79 mare‐yr) at Pryor Mountain, respectively. At McCullough Peaks, mean annual foaling rates from 2006 to 2008 were 75.0% (n = 48 mare‐yr) for untreated mares and 31.7% (n = 101 mare‐yr) for treated mares. Controlling for age of mares and pretreatment differences in fertility, PZP reduced foaling rates in all 3 herds. The pellets used at McCullough Peaks (produced by cold evaporation) were less effective than pellets used in a previous trial and produced by heat extrusion. Immunocontraception with PZP may be a useful tool in reducing fertility rates in some western United States feral horse herds, but population growth reduction will depend on timely access to mares for inoculation and the proportion of mares that can be successfully treated. Published 2011. This article is a U.S. Government work and is in the public domain in the USA.

A nearly complete skeleton of an early juvenile diplodocid (Dinosauria: Sauropoda) from the Lower Morrison Formation (Late Jurassic) of north central Wyoming and its implications for early ontogeny and pneumaticity in sauropods

A nearly complete skeleton of a juvenile sauropod from the Lower Morrison Formation (Late Jurassic, Kimmeridgian) of the Howe Ranch in Bighorn County, Wyoming is described. The specimen consists of articulated mid-cervical to mid-caudal vertebrae and most appendicular bones, but cranial and mandibular elements are missing. The shoulder height is approximately 67 cm, and the total body length is estimated to be less than 200 cm. Besides the body size, the following morphological features indicate that this specimen is an early juvenile; (1) unfused centra and neural arches in presacral, sacral and first to ninth caudal vertebrae, (2) unfused coracoid and scapula, (3) open coracoid foramen, and (4) relatively smooth articular surfaces on the limb, wrist, and ankle bones. A large scapula, short neck and tail and elongate forelimb bones relative to overall body size demonstrate relative growth. A thin-section of the mid-shaft of a femur shows a lack of annual growth lines, indicating an early juvenile individual possibly younger than a few years old. Pneumatic structures in the vertebral column of the specimen SMA 0009 show that pneumatisation of the postcranial skeleton had already started in this individual, giving new insights in the early ontogenetic development of vertebral pneumaticity in sauropods. The specimen exhibits a number of diplodocid features (e.g., very elongate slender scapular blade with a gradually dorsoventrally expanded distal end, a total of nine dorsal vertebrae, presence of the posterior centroparapophyseal lamina in the posterior dorsal vertebrae). Although a few diplodocid taxa, Diplodocus, cf. Apatosaurus, and cf. Barosaurus, are known from several fossil sites near the Howe Ranch, identification of this specimen, even at a generic level, is difficult due to a large degree of ontogenetic variation.

Multiple injury and infection in a sub-adult theropod dinosaur Allosaurus fragilis with comparisons to allosaur pathology in the Cleveland-Lloyd Dinosaur Quarry Collection

ABSTRACT A sub-adult Allosaurus fragilis (MOR 693) was discovered in 1991 in the Upper Jurassic Morrison Formation of Big Horn County, Wyoming. Examination of the specimen reveals pathological conditions on five dorsal ribs, gastralia, cervical vertebra, three dorsal vertebrae, caudal vertebra, chevron, scapula, manus phalanx, ilium, two metatarsals, and two pes phalanges. Detailed description of these bones includes classification according to probable cause (i.e., traumatic; infectious; traumatic-infectious; developmental; idiopathic). In addition to the paleopathological analysis of MOR 693, descriptions and interpretations are given from a study in progress of pathological abnormalities in the Cleveland-Lloyd Dinosaur Quarry collection. This study provides a model for future paleopathological analyses, emphasizing that description of the location, extent, and texture of an abnormality is crucial, since interpretations are subject to change. This analysis discusses physiological implications of the abnormalities in MOR 693 and suggests probable behaviors and environmental influences resulting in injury and infection. Lifestyle and behaviors that likely predisposed allosaurs to injury and infection include pursuit of prey, intra-specific competition for mates, and intra- and inter-specific rivalry for carcasses and territory. Ultimately, paleopathological analysis of a large sample of dinosaur bones may reveal that certain abnormalities characterize taxa, and are diagnostic of specific behaviors, environmental influences, and physiology.

Control of Russian Wheat Aphid, 1988

Abstract This evaluation was conducted in a winter wheat field in Big Horn County approximately 25 miles south of Billings, Mont. The field was seeded September 1987. Insecticide treatments were applied using a CO2-powered backpack sprayer equipped with a 10-ft hand-held spray boom and Teejet 8001LP flat-fan nozzles. The sprayer was calibrated to deliver 10.5 gal water/acre at 20 psi. Treatments were applied on 13 May when the flag leaf of the wheat plants was just visible and arranged in a randomized complete block design with 3 replicates, each measuring 20 by 30 ft. Insecticide efficacy was assessed by clipping 30 tillers from each treated and untreated replicate and counting the number of RWA on each tiller. Plots were machine harvested using a small-plot combine equipped with a 3-ft header. Two sections, measuring 28 by 3 ft, were harvested from each replicate. Grain samples were cleaned with yield calculated and test weight measured.

Jim Crow, Indian Style

N JUNE OF 1986, Judge Edward Rafeedie ruled official acts of discrimination ... have interfered with the rights of Indian citizens [of Big Horn County, Montana] to register and vote. Civil rights expert and ACLU attorney Laughlin McDonald later observed in the San Francisco Examiner racism against Indian people in Montana was even worse than he had expected. I thought I'd stepped into the last century, McDonald explained. Whites were doing to Indians what people in the South stopped doing to blacks twenty years ago. Big Horn County Commissioner and area rancher Ed Miller longs for the good old days when Indians remained on the reservation. Angered by Rafeedie's ruling, Miller threatened to appeal the decision to the Supreme Court. Voting Rights Act is a bad thing, Miller complained. I don't see no comparison with Negroes in the South. Before Janine Windy Boy and other plaintiffs filed suit against Big Horn County, things were fine around here, Miller lamented. Now they (Indians) want to vote, he exclaimed. What next?' On June 13, 1986, United States District Judge Edward Rafeedie ordered elections in Big Horn County violate Section 2 of the Voting Rights Act... . and that a new system of election must be adopted. Judge Rafeedie's decision culminated a three-year process begun in Big Horn County by Crow and Northern Cheyenne voters who refused any longer to accept second class voting rights.2 The case began its way into court in August of 1983, when Jeff Renz and Laughlin McDonald, ACLU attorneys for the plaintiffs, submitted a Motion for Preliminary Injunction preventing the defendants, Big Horn County, from holding a general election on November 6, 1983. The motion called for a hearing before Federal Judge James Battin in Billings, Montana. The motion and subsequent suit against Big Horn County charged the at-large system in county commissioner and school board elections in Big Horn County diluted the Indian vote so as to disenfranchise American Indian voters. The plaintiffs in Windy Boy v. Big Horn County argued the at-large scheme denied the plaintiffs' rights to participate in elections and to elect representatives of their choice to county and school board offices. In Big Horn County, where non-Indians constitute fifty-two per cent of the population and American Indians form forty-six per cent, at-large elections violated the Fourteenth and Fifteenth Amend-

Stratigraphy and Depositional Environments of Jurassic Gypsum Spring and Sundance Formations, Sheep Mountain Anticline Area, Big Horn County, Wyoming: ABSTRACT

Stratigraphy and Depositional Environments of Jurassic Gypsum Spring and Sundance Formations, Sheep Mountain Anticline Area, Big Horn County, Wyoming: ABSTRACT

Insecticide Efficacy for Army Cutworm in Winter Wheat, 1983

Abstract Experimental and registered insecticides were evaluated for efficacy against army cutworm in Big Horn County, Mont. Winter wheat was seeded in 12-in. rows in the fall of 1982. Plots were 8 by 20 ft with three applications of each treatment utilizing a completely randomized design. Insecticides were applied on 31 Mar. with a back-pack sprayer at 30 lb/in2 and volume of 20 gal/acre. Treatments were evaluated on 17 Apr. by sampling the soil surrounding the middle two rows for 6 ft of linear row.

Depositional History and Correlation Problems of the Anderson-Dietz Coal Zone, Southeastern Montana

The Roland, Smith, Anderson, and Dietz coal beds of the Tertiary Fort Union Formation in Big Horn County, Montana, split and merge in a complex pattern which makes standard methods of correlation by stratigraphic interval impossible. The splitting and merging of the coal beds can be related to the distribution of the associated rocks, particularly the sandstone beds which can be divided into crevasse splay and channel fill facies. The elastic partings and intervals between coal beds represent short term input of crevasse splay elastics into interdistributary peat swamps or the longer-term migration of fluvial channels through them. This interpretation means that the coal beds studied in Big Horn County are not separate isochronous beds but are irregularly distributed throughout the stratigraphic interval containing them, and coal beds near the base of the interval can frequently be physically correlated with coal beds near the top of the interval. It is therefore recommended that coal correlations not be carried over long distances or that new names not be assigned to coal beds within the interval without very detailed stratigraphic support.

A Dipnoan Tooth Plate from the Lower Cretaceous of Kansas, USA

A Dipnoan Tooth Plate from the Lower Cretaceous of Kansas, USA

Opkishaesa: Coal on Crow Reservation, Big Horn County, Montana: ABSTRACT

Geologic information has been gathered from 93 holes drilled and cored during the summers of 1968 and 1970 on coal lands in T6, 7S, R37, 38E, Big Horn County, Montana. Results of drilling indicate that at least 16 correlatable coal seams are present and range in thickness from 2 to 55 ft. Several billion tons of strippable reserves (200 ft high wall) were found in the Canyon, Anderson, Smith, Realbird, Schaak, and Roland seams. Realbird and Schaak are new seam names. Other correlations were established and are found in agreement with the work of the Montana Bureau of Mines and Geology. Stratigraphic changes in the upper part of the geologic column (surface to 1,000 ft) should be of interest and importance to both the oil explorationist and those involved with the mode of environment and origin of the Northern Powder River basin coal deposits. The entire project data are being digitized. More than 700,000 points controlling the surface contours are used in conjunction with coal-seam structure maps to arrive at overburden estimates, outcrop patterns, volumetric rock accounting, and mine model studies. Log suites were digitized as were chemical coal analysis results in order to develop both quantitative and qualitative control of the stratified sequence as well as the coal seams. It is believed that this and other discoveries in the area are nationally significant and are suitably large enough to be able to support petroleum liquid or gasification conversion plants, de-ashing refineries, as well as mine-mouth and char power facilities. Development of those industries will be dependent on many factors End_Page 535------------------------------ from engineering feats to economics of world petroleum. End_of_Article - Last_Page 536------------

Case History of the Tensleep Reservoir, Torchlight Field, Wyoming

Abstract The Torchlight field is located on the east side of the Big Horn Basin in Big Horn County, Wyo. Orchard Unit Well No. 1, the Tensleep discovery well, was completed in 1947. The 33 degrees API gravity Tensleep crude was highly undersaturated, and hydraulically contained in the anticlinal reservoir by a tilted water table. After development, fluid producing rate and reservoir pressure declined rapidly. Field performance indicated the reservoir was producing by a limited water drive and would require over 25 years for depletion. Comparisons are made between field producing rates and rates predicted by water influx theory. Predicted rates are 10 to 15 per cent higher than actual rates. The difference is due to reservoir pressure being higher than that assumed in the prediction. Supplemental water injection was started in Oct., 1957, to reduce reservoir life and increase oil rates. Oil response was immediate and reached a maximum rate of 1,785 BOPD in 1959. By Jan., 1965, the reservoir had been essentially depleted after producing 2,774,000 bbl oil. Supplemental water injections have reduced reservoir life at least seven years. Oil recovery by supplemental water injections of 43 per cent of original oil in place will be comparable to recovery by natural water drive. Predicted oil recovery by the Dykstra-Parsons and Stiles methods indicate recoveries of 46 and 50 per cent original oil in place, respectively. However, these two methods assume 100 per cent areal sweep efficiency, and reduction for areal sweep would result in close agreement with actual recovery. Introduction The Tensleep reservoir, Torchlight field, Wyo., is nearing depletion by natural water drive and supplemental water injections after producing over 2.7 million bbl of oil. Collection of extensive engineering data during early development permitted thorough evaluation of reservoir properties, early recognition of the producing mechanism and initiation of a water injection program which significantly increased oil rate and reduced reservoir life. Water injections did not influence or change ultimate oil recovery but provided a decrease in operating costs as compared to depletion by natural water influx. The advanced stage of depletion, plus availability of necessary engineering information, permits comparisons between theoretical and actual reservoir performance. The fluids, rocks and producing mechanism of the Torchlight Tensleep reservoir are characteristic of many Rocky Mountain Pennsylvanian Age reservoirs. A review of the history of the Torchlight Tensleep may assist in more efficient operation of similar reservoirs. History of Development Torchlight field is located on the east side of the Big Horn Basin in Big Horn County, Wyo. (Fig. 1). Wells were drilled as early as 1904, making Torchlight one of the oldest oil fields in Wyoming. JPT P. 1159ˆ

Complex Entrapment at Sage Creek Field, Big Horn Basin, Wyoming: ABSTRACT

Sage Creek field is located on a well developed asymmetric fold in the northern Big Horn Basin of Wyoming. This structure trends northwest-southeast parallel with the Big Horn Mountain front, through T. 57 N., R. 97-98 W., in Park and Big Horn counties. It has about 500 feet of structural closure. The field consists of one Madison well producing 20° gravity oil, and 21 Tensleep wells producing 26° gravity oil. Ultimate recovery from both zones is estimated at approximately 1½ million barrels. The Madison pool is of small areal extent and is a simple gravity accumulation in a zone of permeability well below the top of the formation. The Tensleep pool is of a more complex nature and consists of five separate accumulations in zones of porosity and permeability within an otherwise dolomitic Tensleep sand. These five bubbles of oil are displaced down the southwest or basinward limb of the structure by hydrodynamic activity of such an extreme type that the crest of the structure is water-bearing in all Tensleep zones. The unique features of accumulation in this field indicate the need for thoroughness and caution in the evaluation of the Tensleep formation in wildcat wells. End_of_Article - Last_Page 1096------------

Manderson Field, Big Horn County, Wyoming: ABSTRACT

The Manderson field on the Manderson anticline, which is a plunging structural nose about 12 miles long, is located on the eastern flank of the Big Horn basin in Big Horn County, Wyoming. Seismic and subsurface information indicates no effective structural closure along the axis of this anticline to form a trap for the accumulation of oil and gas. The facies change in the Phosphoria formation, from carbonates to redbeds takes place in an easterly direction across the southern end of the Big Horn basin. By establishing a chert horizon as the dividing line between the productive and non-productive zones of the Phosphoria formation, the problem of locating stratigraphic traps is simplified. Isopach End_Page 530------------------------------ maps of the productive part of the Phosphoria formation show the relation of the Manderson field to this stratigraphic trap. The reservoir in the Manderson field is a stratigraphic trap formed by the facies change in the Phosphoria formation. End_of_Article - Last_Page 531------------

Two Cases of Dental Anomaly in Early Tertiary Mammals

All large collections of Recent mammals contain specimens which show anomalies in the dental formulae or in individual teeth although such specimens are proportionately rare. Similar anomalies are found also in fossil specimens although the number is less because fewer specimens are involved. Are these fossil specimens productive of taxonomic error? I have received the impression that this is not an uncommon question among neozoologists. Mistakes have been made, but the number of named as a result of this kind of misunderstanding of the evidence probably is insignificant among fossil mammals. On the other hand, many examples of dental anomaly or abnormality have been described from fossils, although these descriptions frequently have been buried in comprehensive monographs. Determination of these cases as such is based on the same principles as in Recent species. Two examples in the collections of the Museum of Natural History, University of Kansas, and previously undescribed, are given below. The first specimen is a fragment of left lower jaw with two molar teeth and part of a third, K.U. No. 8508. This fragment belongs to the primate genus Pelycodus, and probably to the species P. ralstoni. The specimen was found on the south fork of Elk Creek, Big Horn County, Wyoming, in the lower part of the Willwood formation of early Eocene age.