Now showing items 191-210 of 1029

• #### Daily Energy Budgets Of Caribou: A Simulation Approach (Energetics, Metabolism, Rangifer Tarandus, Migration)

Energetic constraints have played a major role in the evolution of caribou (Rangifer tarandus). This thesis discusses several ways in which these constraints have affected caribou morphology, physiology and behavior through their effects on the physiological condition of caribou. A computer model of daily energy budgets was used to simulate energy budgets of caribou in late winter, spring migration, and during the month of July when caribou may be harassed frequently by insects. Model outputs included estimates of metabolizable energy intake, and changes in body weight and body composition. Several of the model inputs, such as fasting metabolic rates and activity costs, were measured using captive caribou. The mean energy cost for locomotion by adult caribou was the lowest recorded for any terrestrial species, and was more strongly related to leg length than to body weight. Highly significant (p < 0.001) relationships between oxygen consumption and heart rates were used to estimate energy expenditures for activities from heart rates of caribou ranging within a large enclosure. Energy expenditures by caribou while feeding on grain at a trough, grazing, browsing and walking, as estimated from heart rates, were 12%, 18%, 18% and 46% higher than that while standing, respectively. The doubly labeled water method was validated using caribou and reindeer as a method for estimating energy expenditures by free-ranging ruminants. The computer model accurately predicted changes in body weight and composition in trials with captive caribou. The model predicted fat losses of approximately 4 kg for pregnant females of the Porcupine Herd during spring migration. During the insect season, a lactating female was predicted to be in negative energy balance on all days when insect harassment occurred for 12 h or longer. Variations in input data associated with energy intake had a much greater effect on model outputs than did factors associated with energy expenditure. Consequently, the optimal range use strategy in the absence of other constraints should involve movements to areas where the most digestible forages can be obtained and the highest eating rates attained.
• #### Daily heterogeneity in habitat selection by the Porcupine Caribou Herd during calving

Caribou exhibit scale-dependent habitat selection, but variance in daily habitat selection by the Porcupine Caribou Herd (PCH) has not been examined. Investigating temporal variance in habitat selection may clarify the time period when managers may accurately estimate calving-related habitat selection. Annually, 1992-1994, approximately 70 calves were radio-collared within 2 days of birth and relocated daily until departing the calving grounds. We used daily 99% fixed kernel utilization distributions (UD's) to estimate caribou distributions, then estimated daily habitat selection using logistic regression. Habitat variables included relative vegetation greenness, greening rate, landcover class, and elevation. Spatial scales of investigation included concentrated vs. peripheral use within daily UD's, daily use within the merged extent of all daily UD's, and daily use within the historical extent of calving, 1983-2001. We used linear regression of logistic regression parameter estimates on sequential sampling days to estimate temporal habitat selection trends during the 3 weeks following capture. Overall, caribou exhibited habitat selection at multiple scales, without temporal trends, suggesting that the 21-day period following capture constituted a single domain and that managers may accurately estimate calving-related habitat selection at any point during this period.
• #### Data (Appendix) for Book Chapter 22: Rapid Assessment of Urban Birds and GIS models of Kathmandu and Pokhara, Nepal with Regmi and Huettmann 2020 Hindu Kush Himalaya: Watersheds Downhill, Springer

This compiled dataset consists of a field data from rapid assessment of common birds found in urban areas of Kathmandu and Pokhara, Nepal, Hindu Kush-Himalaya (HKH) region.The dataset consists of 31 bird and animal species from a detection survey of 2 transects and photos in MS Excel sheets. It is overlaid with Open Street GIS map predictors for the study areas, and model predicted with GIS. We used the following 6 layers:waterways, natural places, shop polygons, land use, roads and highways and computed proximities for each in GIS. Methods and details are specified in the book chapter by Huettmann in Regmi and Huettmann 2020. This is the first and best compiled field and GIS data for the study area and is to set a start of such views and investigations towards a better and more fair access to data, as part of a better and more democratic decision-making process. Here an example is presented using avian species and GIS habitat layers.
• #### Data (Appendix) for Book Chapter 25: Museum Data holdings and Libraries in Nepal and Hindu Kush Himalaya region with Regmi and Huettmann 2020 Hindu Kush Himalaya: Watersheds Downhill, Springer

This compiled dataset consists of a value-added analysed GBIF data set in the wider Hindu Kush-Himalaya (HKH) region. The original data source is from individual national contributors found in GBIF. Data are used here for research purposes for the wider HKH region watersheds and to show institutional spread and distribution. Some major outside museums internationally are mentioned too. The dataset consists of MS Excel sheets Methods and details are specified in the book chapter by Huettmann in Regmi and Huettmann 2020. This is the first and best compiled data for the study area and is to set a start of such views and investigations towards a better and more fair access to data, as part of a better and more democratic decision-making process.
• #### Data (Appendix) for Book Chapter 28: Sarus Crane GIS Model with Regmi and Huettmann 2020 Hindu Kush-Himalaya: Watersheds Downhill, Springer

This dataset consist of an appendix of GIS model predictions of Sarus Cranes (GRus antigone Taxonomic Serial Number TSN: 176181) in Nepal. Details are specified in the book chapter by Karmacharya et al in G.R.Regmi and F. Huettmann 2020. This is the first model for this species and shows conservation management implications for the Terai landscape between Nepal and India.
• #### Data (Appendix) for Book Chapter 33: Persistent Langur (Semnopithecus) decline in Nepal with Regmi and Huettmann 2020 Hindu Kush Himalaya: Watersheds Downhill, Springer

This dataset consists of an appendix of a GIS map of langur sp information in Nepal. The datasets are locations, presences and absences from a value-added GBIF.org query, transect data by the authors and literature data Details are specified in the book chapter by Ale et al in Regmi and Huettmann 2020. This is the first and best compiled data for this species in Nepal and shows national declines with large conservation management implications.
• #### Data (Appendix) for Book Chapter 37: 'Road, Railroad and Airport data for the Hindu Kush Himalaya region' with Regmi and Huettmann 2020 Hindu Kush Himalaya: Watersheds Downhill, Springer

This compiled dataset consists of an appendix of value-added merged GIS maps for roads, railroads and airports in the wider Hindu Kush-Himalaya (HKH) region. The original data source is from individual national DIVA-GIS files and used here for research purposes for the wider HKH region watersheds. Nations included are: Nepal, India, China, Buthan, Kazachstan, Tajikistan, Kyrgystan, Uzbekistan, Turkmenistan, Afghanistan, Iran, Laos, Myanmar, Thailand, Vietnam, Pakistan, Bangladesh and Cambodia. The dataset consists of 21zip archives of these nations also covering railways and airports. Methods and details are specified in the book chapter by Huettmann in Regmi and Huettmann 2020. This is the first and best compiled data for the study area.
• #### Data (Appendix) for Book Chapter 43: Citizen Science Experience in Lumbini/Nepali for Sarus Cranes and Lesser Adjudants (Storks) with Regmi and Huettmann 2020 Hindu Kush Himalaya: Watersheds Downhill, Springer

This dataset consist of an appendix of citizen science data for the Sarus Crane and Adjudant storks in Lumbini and Jagdishpur Reservoir, Nepal. It's a plain MS Excel sheet.
• #### Data analysis and data assimilation of Arctic Ocean observations

Arctic-region observations are sparse and represent only a small portion of the physical state of nature. It is therefore essential to maximize the information content of observations and bservation-conditioned analyses whenever possible, including the quantification of their accuracy. The four largely disparate works presented here emphasize observation analysis and assimilation in the context of the Arctic Ocean (AO). These studies focus on the relationship between observational data/products, numerical models based on physical processes, and the use of such data to constrain and inform those products/models to di_erent ends. The first part comprises Chapters 1 and 2 which revolve around oceanographic observations collected during the International Polar Year (IPY) program of 2007-2009. Chapter 1 validates pan- Arctic satellite-based sea surface temperature and salinity products against these data to establish important estimates of product reliability in terms of bias and bias-adjusted standard errors. It establishes practical regional reliability for these products which are often used in modeling and climatological applications, and provides some guidance for improving them. Chapter 2 constructs a gridded full-depth snapshot of the AO during the IPY to visually outline recent, previouslydocumented AO watermass distribution changes by comparing it to a historical climatology of the latter 20th century derived from private Russian data. It provides an expository review of literature documenting major AO climate changes and augments them with additional changes in freshwater distribution and sea surface height in the Chukchi and Bering Seas. The last two chapters present work focused on the application of data assimilation (DA) methodologies, and constitute the second part of this thesis focused on the synthesis of numerical modeling and observational data. Chapter 3 presents a novel approach to sea ice model trajectory optimization whereby spatially-variable sea ice rheology parameter distributions provide the additional model flexibility needed to assimilate observable components of the sea ice state. The study employs a toy 1D model to demonstrate the practical benefits of the approach and serves as a proof-of-concept to justify the considerable effort needed to extend the approach to 2D. Chapter 4 combines an ice-free model of the Chukchi Sea with a modified ensemble filter to develop a DA system which would be suitable for operational forecasting and monitoring the region in support of oil spill mitigation. The method improves the assimilation of non-Gaussian asynchronous surface current observations beyond the traditional approach.
• #### Data Submission Package for Manuscript 'Model-predicting Matschie's Tree Kangaroo in Papua New Guinea'

These are the GIS data used for modeling Matschie's Tree Kangaroo (Huon Tree Kangaroo) in Papua New Guinea PNG; for details please see metadata. THe manuscript is currently in revision phase.
• #### Deactivation and excitation of 0I(6s ⁵S) at above-thermal energies

Absolute collisional deactivation and excitation cross sections have been measured for a beam of O (⁵P-⁵S°) incident on N₂. The beam energy was varied from 3.95 to 10.65 keV. Cross sections for charge transfer (electron capture) of 0⁺ in N₂ were also measured in the energy range from 2.4 to 24.3 keV. The variation of light intensity 5436 Å (from the 6s-3p transition of the quintet system of atomic oxygen) emitted from the beam as a function of N₂ target pressure was fitted to a beam of kinetic equation to determine deactivation and excitation cross sections. The cross section for deactivation in N₂ decreases from 6.84 x 10⁻¹⁵ cm² at 3.95 keV to 1.5 x 10⁻¹⁵ cm² at 19.65 keV. The cross section for excitation decreases from 3.3 x 10⁻¹⁹ at 3.95 keV to 2.25 x 10⁻¹⁹ cm² at 19.65 keV.
• #### Decadal scale vegetation maps for the boreal forest surrounding Fairbanks, Alaska

Vegetation maps of a selected area within the boreal forest surrounding Fairbanks, Alaska, have been generated for the nominal years of 1985, 1995, 2005, and 2015 using Landsat 4 and 5 Thematic Mapper and Landsat 8 Operational Land Imager surface reflectance products at 30 meter spatial resolution using a decision tree classification. The maps include 9 U.S. Geological Survey (USGS) vegetation classes, as well as barren land, open water, and ice/snow classes that are consistent with the classes identified in the 2001 National Land Cover Database (NLCD) map of Alaska generated by the USGS. Classification steps are based on USGS methodology, with refinements for the boreal forest, to ensure further comparison to the 2001 USGS NLCD map for Alaska. The overall weighted accuracies of first order estimates of data quality using cross validation are 93.2%, 88.4%, 93.3%, and 86.9% for the nominal years of 1985, 1995, 2005, and 2015 maps, respectively, compared to 81.8% accuracy for the USGS NLCD 2001 product. This study demonstrates that the spatial and spectral resolution of Landsat data is the best available for mapping the vegetation of Alaska's boreal forest at 1:50,000 scale. It also shows that the boreal forests surrounding Fairbanks, Alaska have witnessed a decrease in the growth of evergreen forests, an expansion of shrub and an increase in wetland distribution, all of which have been reported as impacts of a warming climate in the Arctic and Sub-arctic.
• #### Deciphering Okmok Volcano's restless years (2002-2005)

Okmok Volcano is an active island-arc shield volcano located in the central Aleutian islands of Alaska. It is defined by a 10-km-diameter caldera that formed in two cataclysmic eruptions, the most recent being ~2050 years ago. Subsequent eruptions created several cinder cones within the caldera. The youngest of these, Cone A, was the active vent from 1815 through its 1997 eruption. On July 12 2008 Okmok erupted from new vents located northwest of Cone D. Between 2001 and 2004, geodetic measurements showed caldera inflation. These studies suggested that new magma might be entering the system. In 2002, a newly installed seismic network recorded quasi-periodic ("banded") seismic tremor signals occurring at the rate of two or more episodes per hour. This tremor was a near-continuous signal from the day the seismic network was installed. Although the volcano was not erupting, it was clearly in a state of unrest. This unrest garnered considerable attention because the volcano had erupted just six years prior. The seismic tremor potentially held insight as to whether the unrest was a remnant of the 1997 eruption, or whether it signaled a possible rejuvenation of activity and the potential for eruption. To determine the root cause and implications of this remarkable seismic tremor sequence, I created a catalog of over ~17,000 tremor events recorded between 2003 and mid-2005. Tremor patterns evolved on the scale of days, but remained the dominant seismic signal. In order to facilitate the analysis of several years of data I created a MATLAB toolbox, known as "The Waveform Suite". This toolbox made it feasible for me to work with several years of digital data and forego my introductory analyses that were based on paper "helicorder" records. I first attempted to locate the tremor using the relative amplitudes of the seismograms to determine where the tremor was being created. Candidate tremor locations were constrained to a few locations along a corridor between Cone A and the caldera center. I then determined theoretical ratios between a reference station and stations nearby the candidate sources. Results suggested that the signal originated in the shallow portion of the corridor connecting the surface of Cone A to the top of the central magma chamber. This study also suggested that the source migrated along this corridor. I integrated the tremor patterns with other studies and proposed that heat and pressure from continued injections of magma were responsible for maintaining an open venting system at Cone A. The tremor resulted from the boiling of a shallow hydrothermal system in the vicinity of Cone A and volatiles potentially coming from the magma itself. The tremor catalog demonstrates that the seismic signal waned during the study period suggesting that fewer fresh volatiles entered the system, which may have allowed the pathways connecting the magma and volatiles to the surface to close up. By the time new magma entered the system in 2006, this network of pathways was closed, forcing the volatiles to seek a new exit. In hindsight, the 2003-2005 period of varied and waning seismic tremor, and the inferred end of massive open venting, may have been a pivotal era at Okmok that eventually led to the 2008 eruption.
• #### Decomposition of dissolved organic matter in Arctic and boreal streams

Arctic and boreal rivers connect terrestrial, oceanic, and atmospheric carbon (C) pools by transporting and processing dissolved organic matter (DOM). DOM composition influences its susceptibility to decomposition (biolability), which in turn determines whether the associated C is respired, stored, or exported. High-latitude ecosystems are changing rapidly due to processes such as permafrost thaw, shifts in vegetative communities, and increasing discharge, and each of these processes can influence the composition of DOM reaching rivers. The eventual fate of riverine DOM, whether it is mineralized or exported, shifts the balance of global C pools. Therefore, to understand how changes to high-latitude ecosystems influence the global C cycle, we must be able to connect patterns in DOM composition to its biolability and subsequent fate within the C cycle. The objectives of this study were to describe spatial and temporal patterns in DOM composition and biolability, and to determine links between the composition and biolability of DOM. I sampled DOM from streams along an Arctic-boreal gradient in interior Alaska throughout the year. I measured DOM biolability and nutrient limitation of decomposition in laboratory incubations and characterized DOM composition using optical properties and chemical analysis. I found that temporal patterns in DOM composition corresponded to seasonal trends in the hydrology of high-latitude catchments, linking DOM source to shallow, organic-rich flowpaths in spring and deeper groundwater flows in winter. Biolability was low, indicating that the majority of riverine DOM is recalcitrant to biological decomposition. I observed increased biolability in response to phosphorus (P) addition, particularly during spring, indicating that phosphorus limits DOM decomposition. To further examine the mechanisms driving C processing in streams, I also conducted a series of whole-stream experiments to compare the relative influence of molecular composition and nutrient content of DOM. I added leaf leachate to boreal streams and measured C retention, which represents both biological uptake and sorption. The leachates varied by molecular composition, due to differences in tissue chemistry of plant species, and in nutrient content, because the leaves were collected from plots with different fertilization regimes. Retention was greatest for leachates derived from trees that had been fertilized with P, indicating P-limitation of biological uptake of C or preferential sorption of P-containing organic molecules. Although leachates varied in molecular composition as determined by optical properties, these differences did not correspond to a difference in uptake rates by species. These patterns in DOM retention indicate that nutrient content is a greater constraint on C uptake than molecular composition. Together, the two studies suggest that export is the primary fate of ambient DOM in high-latitude streams, but that C processing is highly sensitive to inputs of bioavailable DOM. The coupling between the P and C cycles observed in both studies highlights the potential for nutrient availability to constrain or promote CO₂ emissions from C-rich, high-latitude catchments.
• #### Decompression induced crystallization of basaltic andesite magma: constraints on the eruption of Arenal volcano, Costa Rica

Continuously active since 1968, Arenal Volcano in Costa Rica has undergone various eruption styles. The deposited magmas, whereas geochemically similar, show a complex history of magma chamber processes, which are not fully understood. The intricate mixing histories of the phenocrysts and lack of oxide pairs have made determination of the volatile content and oxygen fugacity difficult by conventional methods. Phase equilibria experiments were carried out between 200-50 MPa and 940-1075°C in a TZM furnace at fO₂ of NNO and water saturation. Time in the furnace varied from 7 to 30 hours at constant pressure and temperature. Examination of the natural and experimental phase assemblages constrained the probable pre-eruptive conditions for Arenal magmas to be 50-80 MPa and 950-1040°C. For decompression experiments, the sample was initially held at two conditions 200MPa and 950°C and 60MPa and 1050°C. The samples were then decompressed by 5-30 MPa pressure steps held for 20 seconds to 8 hours until 20 MPa was reached, approximating average decompression rates of 0.25, 0.025, and 0.0013 MPa/s. Textures formed in the experiments and seen in the natural samples constrain the probable ascent rate of the Arenal magma to 0.05 mls. The ascent rate increases as explosivity increases.
• #### Deformation microstructures, mechanisms, and history of a shear zone within the Chugach accretionary complex in the Nelchina area, South-Central Alaska

Ductile-to-brittle fault zones reveal mineralogical processes that are thought to be responsible for the mechanical behavior of faults. I examined a pervasively deformed zone within the Jurassic to Cretaceous accretionary complex of southern Alaska that preserves hydrothermal alteration, dissolution precipitation, carbonaceous material (CM), clay minerals, and intracrystalline plasticity, all of which influence the strength of a fault. I characterized microstructures by SEM and EBSD, determined compositions by XRD, XRF, and Raman spectroscopy for one carbon-rich sample, and dated whole rock, rotated K-feldspar, and metamorphic muscovite by ⁴⁰Ar/³⁹Ar thermochronology to constrain the timing and conditions of accretion, uplift, and deformation recorded by this fault zone. I interpret the specific mineralogy and complex network of deformation microstructures as a result of multiple deformation events. Highest-temperature deformation recorded within the shear zone is lower greenschist facies (400-450°C). Quartz-rich clasts preserve deformation lamellae, grain bulges, sweeping undulose extinction, pressure solution, and brittle fractures characteristic of low grade (300-400°C) at the brittle-ductile transition. Brittle overprint is expressed by fractures cross-cutting the stretched quartz phacoids, and black fault rock that has entrained stretched quartz grains. Raman spectroscopy places precipitation of the CM at ~300˚C. I therefore associate the fault-rock fabrics with progressive down-temperature deformation as the fault was exhumed. I suggest that pressure solution and mineral alteration in all fault-zone samples, as well as quartz and phyllosilicate preferred orientation in a subset of the samples, indicate aseismic slip. Growth of clay and precipitation of CM reduced the friction coefficient, lowering the frictional strength and influencing the dynamic behavior of this fault zone. Constraining the relative timing of the different slip behaviors is hard to determine. It is possible they were active at the same time, especially with the increase of width and complexity at the deeper part of the fault. What is preferentially preserved in the rock record is the latest stage of slip. Pseudotachylite structures generated during earthquakes, however, are rarely preserved due to their susceptibility to alteration. In my field area, consequent exhumation and cooling lead to progressive down-temperature brittle deformation and strong hydrothermal alteration, which could have eradicated any evidence for frictional melting. Using ⁴⁰Ar/³⁹Ar thermochronometry alongside regional and local age constraints, I was able to provide some insight on timing of fault-zone and local tectonic activity. The fault lies between the McHugh Complex and Valdez Group, the two main components of the Jurassic to Cretaceous Chugach accretionary prism whose development and disruption is still debated. I interpret that fault activity lasted from ca. 120 Ma to ca. 60 Ma., and was followed by two stages of accelerated uplift and cooling during ca. 40 Ma and ca. 20 Ma. The cease of major fault activity after ca. 60 Ma, the lack of pervasive strike-slip motion indicators, and the presence of undeformed Eocene dikes as well as Eocene sediments deposited on top of both the McHugh Complex and Valdez Group, suggest they were deposited in proximity and were in place in Southern Alaska at the start of the Eocene epoch.
• #### Dependence of the ionospheric convection pattern on the conductivity and the southward IMF

Electric field measurements from the DE-2 satellite were used to determine the location of the convection reversal boundary and the potential around this boundary under a combination of interplanetary magnetic field (IMF) and auroral electrojet conditions. The electric potential is obtained by the integration of the electric fields. The convection reversal boundary is defined in this study as where the potential has its absolute maximum and minimum values. The data were sorted into 18 categories according to two levels of the negative IMF $B\sb{z},$ three ranges of IMF $B\sb{y},$ and two substorm phases. The data were fit with both continuous and discontinuous boundaries to get a functional representation of boundary potentials and locations. A simple model is constructed by solving the Laplace's equation in order to illustrate the obtained boundary potentials and locations. The results show that the enhanced electric field in the midnight sector is associated with an intense westward electrojet current. It can also be seen that the convection reversal boundary is found to be discontinuous near midnight. The discontinuous convection reversal boundary on the dayside is related to the merging near dayside cusp region. The discontinuous convection reversal boundary on the nightside is related to the conductivity enhancement. The intrusion of the dawn cell into the dusk cell is due to nonuniformity of the Hall conductivity in the ionosphere. Another model is constructed by solving the current continuity equation with field-aligned current and nonuniform conductivity added. It can be found that a secondary convection reversal, which is detached from the dusk-cell convection reversal, appears in the evening-midnight sector within the polar cap when the IMF $B\sb{y}$ is positive and the conductivity is nonuniform. This convection reversal is attributed to be created by the B $\times$ V dynamo. Also, the inclusion of the region 2 field-aligned current leads to an enhancement of the electric field in the region between the region 1 and region 2 currents.
• #### Depositional Environments Of The Late Cretaceous (Maastrichtian) Dinosaur-Bearing Prince Creek Formation: Colville River Region, North Slope, Alaska

The Prince Creek Formation contains first-order meandering trunk channels, second-order meandering distributary channels, third-order fixed anastomosed(?) distributary channels, crevasse splays, levees, lakes, ponds, swamps, paleosols, and ashfall deposits. Trampling by dinosaurs is common. Most deposition occurred on crevasse splay-complexes adjacent to trunk channels. Rhythmically-repeating coarse-to fine-grained couplets in inclined heterolithic stratification suggest tidal-influence in channels. Cumulative to compound soils similar to Entisols, Inceptisols, and potential acid sulfate soils formed on levees, point bars, crevasse splays, and on the margins of lakes and swamps. Frequent overbank flooding is evidenced by silt and sand dispersed throughout paleosol profiles and fluctuations with depth in several molecular ratios. Drab colors, organics, siderite, depletion coatings, and zoned peds indicate waterlogged, anoxic conditions while ferruginous and manganiferous features, insect and worm burrows, and rare illuvial clay coatings and infillings suggest drying and oxidation of some soils. Repeated wetting and drying is tied to fluctuating river discharge. Marine influence is evidenced by jarosite, pyrite, and gypsum which become increasingly common up-section near the contact with the shallow-marine Schrader Bluff Formation. Pollen includes Peridinioid dinocysts; algae; projectates; Wodehouseia edmontonicola; pollen from lowland trees, shrubs and herbs; Bisaccates; fern and moss spores; and fungal hyphae and indicates that all strata are Early Maastrichtian and that sediments become progressively younger to the north. 40Ar/39Ar analysis of a tuff returned an age of 69.2 +/- 0.5 Ma. World-class dinosaur bonebeds are encased in muddy overbank alluvium overlying floodplains. No concentration of bone was found in channels. Bonebeds are laterally extensive except where truncated by distributaries. At the Sling Pont, Liscomb, and Byers bonebeds alluvium encasing bone exhibits a bipartite division of flow and a massive mudstone facies containing flow-parallel plant fragments that "float" in a mud matrix suggesting deposition by fine-grained hyperconcentrated flows. Exceptional floods driven by seasonal snowmelt in the Brooks Range increased suspended sediment concentrations, generating hyperconcentrated overbank flows that killed and buried scores of juvenile dinosaurs occupying this high-latitude coastal plain. This unique killing mechanism likely resulted from fluctuating discharge tied to extreme seasonality brought about by the near polar latitude of northern Alaska in the Late Cretaceous.
• #### Depositional Systems, Paleoclimate, And Provenance Of The Late Miocene To Pliocene Beluga And Sterling Formations, Cook Inlet Forearc Basin, Alaska

The sedimentary record of forearc basins provides critical clues to the complex geologic history of subduction zones. This study focuses on Cook Inlet forearc basin, part of a larger forearc basin complex in southern Alaska. Specifically, I investigated the sedimentology, paleoclimate, and provenance of the Beluga and Sterling formations, comprising the late Miocene to Pliocene Cook Inlet basin record. These interpretations are used to reconstruct the Miocene-Pliocene basin history and better understand forearc development. Before ~11 Ma anabranching/single channel depositional systems of the Beluga Fm. deposited sediment on the western and eastern margins of Cook Inlet. Sandstone compositional data suggest sediment from the eastern margin was sourced from the accretionary prism. Between ~11 Ma and ~8 Ma deposition of the Beluga Fm. waned and sandstone compositional data indicate increases in volcanic lithic fragments derived from the volcanic arc to the northwest. Deposition by the southward-directed, sandy braided fluvial systems of the Sterling Fm. started on the western margin of the basin and migrated eastward, reaching the eastern margin ~8 Ma. By ~6 Ma, sandstone compositional data suggest that the volcanic arc was the dominant sediment contributor to the basin. Palynological results suggest that forests were predominately confined to coal swamps, and the surrounding floodplains were occupied by shrubs, herbs, and dispersed tree taxa. Thermophilic taxa persisted until at least ~6 Ma. Mean annual precipitation (MAP), estimated from delta13C values, ranged from 420 to 3900 mm a-1 with the greatest variability ~8 Ma. This ~8 Ma event correlates with a decline in sea surface temperatures of the Alaska Gyre and a North Pacific climate optimum. Climate likely played a minor role in fluvial style change. The dramatic change in depositional style between the Beluga and Sterling fms. is attributed to a change in sediment flux from the accretionary prism to the volcanic arc and western Alaska Range, most likely due to orogen-scale tectonic processes driven by far-afield flat-slab subduction of the Yakutat microplate. The change in fluvial style and sediment flux starting ~11 Ma suggests a previously unrecognized exhumation in the western Alaska Range at this time.
• #### Description and identification of larval fishes in Alaskan freshwaters

Identification of larval fish is important for assessing fish populations and human impact on fish ecosystems but is difficult due to subtle differences between larvae of different species. A key to larval fishes is valuable for successful population studies. This thesis is a preliminary study towards the development of a key to the larval stages of Alaskan freshwater fishes. Early life history information on 23 of approximately 40 Alaskan freshwater species was obtained from the literature. Six of these species (sheefish, Stenodus leucichthys; Arctic grayling, Thymallus arcticus; Arctic char, Salvelinus alpinus; Dolly Varden, S. malma; longnose sucker, Catostomus catostomus; and slimy sculpin, Cottus coqnatus) were laboratory-reared or collected near Fairbanks for additional information. Technical illustrations and morphometric data were prepared for each of the six species. This study indicates that follow-up research on several whitefishes will be critical for developing a comprehensive larval fish key to Alaskan freshwater species.