• Geology of the boundary area, Eagle A-1 and Tanacross D-1 quadrangles, east-central Alaska

      Flynn, Roy L. (2003-05)
      Structural relationships and tectonic events in the Boundary area of east-central Alaska shed light on the generally obscure tectonic history of the Yukon-Tanana Upland region. This study used detailed mapping of 160 km², with supporting petrography, geochemical analyses, and ⁴⁰Ar/³⁹Ar dating to define the geology and tectonic history of the Boundary area. A major thrust zone juxtaposes lithotectonic assemblages of metamorphic rocks in the Boundary area, with the Fortymile River assemblage (approximately middle amphibolite facies) thrust over the Nasina and Klondike series (middle to upper greenschist facies), and ultramafic rocks and metagabbro (lower greenschist facies) and epidote-amphibolite-facies gneiss and schist imbricated along the thrust faults. Final thrust imbrication postdates cooling from peak metamorphism in amphibolite-facies lithologies, which appears to be Early Jurassic age. The thrust zone is exposed partially rimming a broad, dome-shaped anticline that encompasses the entire map area. Thermally reset ⁴⁰Ar/³⁹Ar ages in the Boundary area appear to be the result of a short-lived, probably igneous, Mid-Cretaceous reheating event, with widespread and locally variable effects, contemporaneous with intrusion of the Crag Mountain pluton south of the map area. Numerous later high-angle, presumably strike-slip faults transect the Boundary area, with apparently associated latest Cretaceous to Miocene volcanic rocks.
    • Geology of the Caribou Creek area, Big Delta quadrangle, east-central Alaska

      Lessard, Richard R. (2006-12)
      The Caribou Creek area, in the Big Delta C4 Quadrangle, East-Central Alaska, is known for significant placer gold, but no lode source. I present a new 200 km² area geologic map utilizing ground based mapping, airborne geophysical surveys, and follow-up laboratory investigations. Mapping and petrography delineate 10-20 km² blocks containing contrasting rock units and mineral assemblages. Amphibolite facies blocks contain abundant post-kinematic andalusite, with central blocks containing partially replaced kyanite, and blocks to the southeast and west containing post-kinematic sillimanite. Geothermobarometry shows that the amphibolite-facies blocks experienced pressures/temperatures of 11.5 kbars/650°C, followed by a collisional event associated with low-P/variable T post-kinematic recrystallization. The distribution of alumino-silicates suggests the central blocks were down dropped relative to adjacent blocks. Gold occurrences are found in west to northwest trending, steeply dipping quartz veins with stibnite ± arsenopyrite. Located in the central blocks, they are separated from a barren granodiorite pluton by a sinistral, northeast trending, high-angle fault. This study has shown the existence of major faults with significant vertical and horizontal movement, making gold source determination difficult. Future lode gold exploration in the area must take the high-angle faulting into consideration.
    • The geology of three extrusive bodies in central Alaska Range

      Albanese, Mary; Turner, Don; Swanson, Samuel; Gilbert, Wyatt; Kienle, Juergen; Stone, David (1980-05)
      The Buzzard Creek basalt, Jumbo Dome, and Sugar Loaf Mountain occur in the Central Alaska Range. The purpose of this study is to determine the age, nature, geothermal potential, and possible genetic relationships between these igneous bodies. The areas were investigated by mapping, radiometric dating, and petrologic studies. The Buzzard Creek basalt appears to have formed by a maar eruption about 3,000 years ago. Seismic evidence suggests this basalt may be related to current subduction in the area. Jumbo Dome consists of calc-alkaline andesite and is probably Pleistocene in age. Sugar Loaf Mountain is composed of Mid-Tertiary rhyolite. Geochemistry suggests that the Sugar Loaf Mountain rhyolite and Jumbo Dome andesite may also be subduction-related. Differences in age and geochemistry indicate there is no genetic relationship between the rocks of the three areas. The ages, type of volcanic features', and snow melt patterns suggest that these three areas have low geothermal potential.
    • Geomagnetic Influences On Thermospheric Winds Observed In The Auroral Zone

      Wallis, Donald Douglas James Herbert; Romick, G. J.; Swift, D. W.; Davis, T. N.; Anger, C. (1974)
    • Geomagnetic micropulsations with emphasis placed on the properties and interpretation of pearls

      Dawson, John Alexander (1965-05)
      The thesis can be divided into three somewhat divergent parts, historical, experimental, and theoretical. The first chapter is an attempt to survey the literature concerning all types of micropulsations. A classification scheme is presented which is in agreement with that adopted by the IAGA at Berkeley, California in 1963, though I have retained the older nomenclature. A summary of the known properties of the various types of micropulsations is presented along with a discussion of controversial points. The next four chapters describe the experimental work performed in cooperation with the Boulder laboratories of NBS, and some observations resulting therefrom. In contrast to the first chapter this section is confined exclusively to pearls. Pearls were found to show little correlation with ionospheric and magnetic data. Exception should be made for two riometer absorption events which can possibly be matched against pearl events. As about 60 to 70 per cent of the pearls observed at College and Macquarie can be matched against each other, pearls are considered to occur simultaneously at conjugate points. At College pearls are shown to be polarized in a plane perpendicular to the magnetic field line. The last chapter develops hydromagnetic wave theory as is pertinent to propagation through the upper magnetosphere. The various assumptions used are examined critically to justify their applicability to the upper magnetosphere. It is found that the magnetosphere below 10,000 km cannot be considered uniform for waves in the 1 cps range. Hence, harmonic solutions to the wave equation cannot be used and more elaborate techniques to treat this problem must be developed. It is suggested that pearls are Alfven waves which propagate along field lines to auroral latitudes. These waves then couple to other modes for propagation to lower latitudes.
    • A geometric analysis of thrust-truncated asymmetric folds, Upper Marsh Fork area, eastern Brooks Range, Alaska

      Jadamec, Margarete A. (2003-08)
      A new surveying technique was developed to document the geometry of eight km size thrust-related folds in the eastern Brooks Range, Alaska. This method combines data from a theodolite and reflectorless laser rangefinder to construct cross sections that are more precise than those based on field map data. In the study area, weakly to non-metamorphosed Carboniferous carbonates typically form northeast-trending, northwest-vergent, asymmetric thrust-truncated folds. The geometry of most of the folds is consistent with a detachment fold model that allows local thickness changes. The anticlines typically display interlimb angles of less than 90,̊ structurally thickened hinge zones, and overturned forelimbs that dip steeply to moderately, suggesting the folds are over-tightened. Furthermore, structural disruption of bedding in the anticlinal forelimbs suggests that strain was localized in this region of the fold and is interpreted to be a record of the transition from folding to thrust faulting within each fold.
    • The geometry and flow of Fireweed Rock Glacier, Alaska

      Bucki, Adam Kyle (2002-05)
      Little is known about the geometry, internal structure or flow of rock glaciers. Geophysical investigations were carried out on Fireweed Rock Glacier to define its geometry. Transient electromagnetic (TEM) methods were effective in determining its shape and depth as well as re-enforcing results of radar and seismic. All of these methods suggest a discontinuity at 15 to 30 m depth. The geometry acquired from these geophysical surveys was used to investigate the motion of the rock glacier. Analysis indicates that motion is concentrated in a pseudo-rectangular subsection of the larger valley on a 'shear plane' at about 27 m depth. We infer that both deformation above and 'sliding' along this shear plane contribute to the observed surface motion. This rock glacier flows relatively quickly for a rock glacier, and has seasonal and annual variations in speed. Some of the variations are related to the quasi-periodic calving at the terminus.
    • Geometry and kinematics of the Yakataga anticline, Icy Bay, Alaska

      Broadwell, Michael Scott; Wallace, Wes; McCarthy, Paul; Hanks, Cathy (2001-05)
      The Yakataga incline is a well-exposed asymmetrical fold with a ramp tip beneath the forelimb. Uncomformities in the backlimb and forelimb indicate that both limbs rotated during fold growth. The stratigraphic character and evidence for deformation before full lithification suggest non-parallel folding by distributed strain rather than flexural slip. These characteristics of the natural fold do not fit existing models for thrust-related folds and I suggest two models for the Yakataga anticline's growth: 1) the fold formed as a non-parallel detachment fold modified by fault-propagation folding in the forelimb; and 2) the fold formed as a rotating-limb fault-propagation fold. The first of these models seems to fit the natural fold better because: 1) this model accounts for the subsidiary fold in the forelimb; and 2) rotation of the backlimb in the fault-propagation fold model requires a fanning of the bedding, a feature not observed in the natural fold.
    • Geometry and kinematics of thrust-truncated and/or flattened asymmetrical folds in the eastern Brooks Range, Alaska

      Bailey, Rebecca D. (2007-08)
      Exceptional exposures of thrust-related folds within carbonate rocks of the Lisburne Group of the Brooks Range of northern Alaska are classified into four groups: unbroken/parallel folds, thrust-truncated/parallel folds, unbroken/flattened folds and thrust-truncated/flattened folds. The geometry of these folds varies greatly along strike, suggesting that serial sections do not represent successive stages in fold evolution. Geometric and kinematic modeling of individual folds reveals that no single fault-related fold model can reproduce the geometry of a given fold. Instead, successful forward modeling of the folds requires some combination of detachment folding with fault-bend folding or fault-propagation folding. All folds followed one of two kinematic paths: the initially parallel folds either broke through without flattening or flattened first and then broke through. Preferred hypothesis for why folds would deform by one path verses the other include: I) Original asymmetry will promote breakthrough over flattening, so that originally asymmetric folds will break through without flattening while initially symmetric folds will flatten before breaking through; and 2) A thin detachment unit may limit fold growth resulting in breakthrough without flattening, while a thick detachment units will not limit fold growth, allowing folds to shorten via flattening before breaking through.
    • The geometry in geometric algebra

      Kilpatrick, Kristopher N.; Maxwell, David A.; Williams, Gordon I.; Rhodes, John A. (2014-12)
      We present an axiomatic development of geometric algebra. One may think of a geometric algebra as allowing one to add and multiply subspaces of a vector space. Properties of the geometric product are proven and derived products called the wedge and contraction product are introduced. Linear algebraic and geometric concepts such as linear independence and orthogonality may be expressed through the above derived products. Some examples with geometric algebra are then given.
    • Geomorphic and climatic influences on white spruce growth near the forest-tundra ecotone in Southwestern Alaska

      Sousa, Emily E.; Heiser, Patricia; Mann, Daniel; Juday, Glenn P. (2015-08)
      Three types of treelines occur in Alaska: a latitudinal treeline running east-west along the Brooks Range, alpine treelines in mountainous regions, and a longitudinal treeline running northsouth along the Bering Sea coast. Latitudinal and alpine treelines in Alaska have been extensively studied; however, little is known about longitudinal treeline in western Alaska. Here I describe the associations between a longitudinal treeline in southwestern Alaska and geomorphology, soils, and climate. This diffuse, lowland treeline is dominated by white spruce (Picea glauca (Moench) Voss) and is presently expanding rapidly westward. Tree age and stand structure vary markedly according to geomorphic position and soil characteristics but generally fall into four vegetation-landscape associations. I cored spruce growing in these four associations to determine limiting germination dates and compare tree growth with climate records. Results show that timing and rate of establishment has varied between vegetation-landscape associations; however, once established, white spruce growth responds positively to warmer summer temperatures with minor variations between sites. Unlike drought-stressed white spruce in Interior Alaska, under likely near-term temperatures, spruce in southwestern Alaska will probably continue to respond positively to warming temperatures. My data suggest this treeline will continue to move westward across varying topographic features and soil conditions, resulting in a complex spatial mosaic of forested and nonforested communities behind the expanding forest margin.
    • Geomorphology and inconnu spawning site selection: an approach using GIS and remote sensing

      Tanner, Theresa Lynn; Margraf, T. Joseph; Wipfli, Mark S.; Verbyla, David (2008-08)
      This study examined the spatial components of inconnu Stenodus leucichthys spawning habitat use in the Selawik River, Alaska. Little is known about inconnu critical habitat needs; however, current studies of inconnu spawning behavior suggest a high level of habitat selectivity. This level of selectivity implies that there are specific habitat characteristics that these fish require for spawning. The purpose of this study was to build a heuristic habitat model that can be used to better understand inconnu spawning site selection in remote Alaskan watersheds. Using readily available, low- or no-cost remote sensing data layers, geographical information systems (GIS) were used in conjunction with multivariate statistics in an attempt to clarify relationships between geomorphologic features and spawning site selection. Spatial resolution of the remotely sensed data available in this study did not provide sufficient spatial detail to generate statistical correlations between spawning habitat selection and landscape characterizations. However, spawning occurred in areas of transition from high to low gradients, and in reaches typified as having very low slopes with very high sinuosity. Additionally, exploratory use of Radarsat fine beam 1 data favored its future application in fisheries investigations. This study is an initial step toward more research into inconnu spawning habitat.
    • Geophysics and tectonic development of the Caroline Basin

      Bracey, Dewey Raymond (1981-09)
      Contradictory hypotheses on the origin of the Caroline Basin suggested that an attempt be made to arrive at a reasonable synthesis of basin origin. This thesis attempts such a synthesis. The principal conclusions reached are that the Caroline Basin formed by a complex sea-floor spreading mechanism in Tertiary time behind a southward advancing island arc. Mantle plume development in the eastern basin during this time may have formed the Eauripik Rise through blockage of westward axial mantle flow at a transform dam. Non-uniform cessation of spreading began in Upper Oligocene, together with the obduction of the southern portion of the ancestral ridge onto New Guinea, with concurrent northward subduction of basin crust at the southern base of the remnant northern ancestral ridge. An extensional trough opened in the northern ridge and expanded until collision with the eastward advancing Yap-Palau arc in Upper Miocene.
    • A geostatistical model based on Brownian motion to Krige regions in R2 with irregular boundaries and holes

      Bernard, Jordy; McIntyre, Julie; Barry, Ron; Goddard, Scott (2019-05)
      Kriging is a geostatistical interpolation method that produces predictions and prediction intervals. Classical kriging models use Euclidean (straight line) distance when modeling spatial autocorrelation. However, for estuaries, inlets, and bays, shortest-in-water distance may capture the system’s proximity dependencies better than Euclidean distance when boundary constraints are present. Shortest-in-water distance has been used to krige such regions (Little et al., 1997; Rathbun, 1998); however, the variance-covariance matrices used in these models have not been shown to be mathematically valid. In this project, a new kriging model is developed for irregularly shaped regions in R 2 . This model incorporates the notion of flow connected distance into a valid variance-covariance matrix through the use of a random walk on a lattice, process convolutions, and the non-stationary kriging equations. The model developed in this paper is compared to existing methods of spatial prediction over irregularly shaped regions using water quality data from Puget Sound.
    • Germany's interests in the Arctic, as exemplifeid by its Arctic Council engagement

      Schley, Kerstin A.; Ehrlander, Mary; Boylan, Brandon; Hirsch, Alexander (2019-05)
      This thesis is a qualitative research exercise, which tests the explanatory value of the international relations theory of neoliberal institutionalism in explaining Germany's engagement in the Arctic and in the Arctic Council. The research question further attempts to clarify Germany's economic and environmental interests pursued through its engagement with the AC. This thesis analyzes Germany's engagement in the Arctic from a historical point of view up to Germany's contemporary interests. Germany's first Arctic engagement started with the period of whaling, continued through the age of polar heroes, up to the weather war of World War II. After the two World Wars, Germany struggled to restart its Arctic engagement, but nowadays enjoys a high reputation as an Arctic player. This is due to the well-known German polar research institute, the Alfred Wegener Institut Helholtz-Zentrum für Polar- und Meeresforschung, but also due to Germany's engagement in the Arctic Council. As a result of Germany's long history of polar, especially Arctic endeavors, the country became an Observer in the Arctic Council at its founding. As global warming has caused significant melting in the Arctic, Germany's interest has shifted from environmental concerns in the region to a dual emphasis of protecting the environment while pursuing economic opportunities. Today Germany pursues several interests in the Arctic, including economic, political, and environmental interests. Neoliberal institutionalism argues that cooperation can emerge through mutual trust and the building of norms, regimes and institutions. Realism on the other hand emphasizes security competition among great powers within anarchy of the international system, with the main aim to survive. The results of the analysis suggest that the theory of neoliberal institutionalism has better explanatory power for interpreting Germany's motivations for engaging in the Arctic Council than the theory of realism.
    • A giant of its kind

      Hinrichs, Christie A.; Farmer, Daryl; Heyne, Eric; Brightwell, Gerri (2013-05)