<p>South-central Alaska is home to many tectonic structures and mountain ranges that have experienced active uplift and deformation within the past 5 to 10 Ma. The Talkeetna Mountains are located above the area of flat-slab subduction of the Yakutat microplate. I hypothesize that the Talkeetna Mountains have been uplifted as a result of this underlying flat-slab subduction and that areas of the Talkeetna Mountains are neotectonically active. The Talkeetna Mountains are deforming heterogeneously across four different structural domains defined by differences in geomorphic patterns, seismicity, dominant fault types, and the orientation of horizontal maximum stress (SHmax). A strain partitioning structure divides the northern and southern domains, and is observed by a change in SHmax orientation from E-W in southern domains to NW-SE in the northern domain. The strain partition is accommodated by a crustal break along the Talkeetna thrust fault, which is expressed at the surface as a wide zone of deformation. Apatite fission-track analysis suggests two distinct periods of uplift: one dated from 45 to 30 Ma and another from approximately 10 Ma to present, with uplift rates of 0.14 mm/yr and 0.24 mm/yr, respectively. The first phase of uplift coincides with a time of significant plate reorganization in the north Pacific which resulted in translation of terranes northwestward. The second phase of uplift correlates with Neogene accretion of the Yakutat microplate. I propose that the majority of Neogene deformation and uplift in the Talkeetna Mountains is due to far-field deformation in the upper plate above the subducting slab. Variations in both composition of the crust and depth to the downgoing slab resulted in strain partitioning and northwest-directed compression in the northern Talkeetna Mountains and northwest compression and warping in the southern Talkeetna Mountains.

Tectonic and climatic influences on bedrock channels traversing the Central Andes, Bolivia

<p> Downcore changes in physical and biological characteristics of lacustrine sediments from Emerald Lake were used to reconstruct the Holocene glacier history of Grewingk Glacier, which drains the Grewingk-Yalik Ice Complex on Kenai Peninsula, Alaska. Emerald Lake is a threshold lake, receiving meltwater and clastic sediment when Grewingk Glacier overtops the topographic divide that separates it from Emerald Lake. Glacier meltwater discharge is represented in sediment cores from Emerald Lake by distinct light-gray, stony mud, with high density and low organic-matter content. Sub-bottom acoustical profiles were used to locate two core sites: one with a low sedimentation rate (Core 2; 18 m depth) and one with a high rate (Core 3; 50 m depth) to maximize both the length and resolution of the sedimentary sequence recovered in the ~3-m-long cores. Bulk density, sedimentation rate, stratigraphy, organic-matter content, and chlorophyll were used to record environmental changes since ~12 cal ka, with ¹⁴C and ²¹⁰Pb for geochronology. Ages were assigned to tephra beds in Cores 2 and 3: 18 and 9 beds respectively. A diffuse transition from the basal inorganic mud to organic-rich mud ~11.4 cal ka marks the initial retreat of the Grewingk Glacier below the divide of Emerald Lake. The overlaying organic-rich mud is interrupted by stony mud that records a brief re-advance as ice overtopped the divide again ~10.7 cal ka, followed by the final glacial-interglacial transition ~9.8 cal ka. The glacier did not spill meltwater into the lake again until the Little Ice Age, from around AD 1350-1900, consistent with documented LIA advances on the Kenai Peninsula. The retreat is estimated from lichen ages on a bouldery moraine on the topographic divide and is consistent with the previously estimated age of the Grewingk Glacier terminal moraine (AD 1858). The retreat of Grewingk Glacier below the divide at 11.4 cal ka took place as temperature and productivity increased across southern Alaska; the subsequent readvance above the divide at 10.7 cal ka corresponds with cooling beginning ~11.0 cal ka in south-central Alaska. Decreased precipitation in southern Alaska from 5.5 to 4.0 cal ka lowered the level of Emerald Lake and sedimentation rate decreased. The initial LIA advance over the divide (AD 1350) and peak meltwater input into Emerald Lake (AD 1660) coincide with documented solar minima, suggesting solar variability influences Grewingk Glacier fluctuations.</p>

<p> Optically stimulated luminescence (OSL) dating and stream profile analysis were used to evaluate the main structural elements controlling the formation of San Timoteo Badlands topography. Stream profiles from 16 streams were created using light detection and ranging (LiDAR) and GPS data, providing new 1 meter-resolution stream profiles along the badlands. Ten new OSL dates from sediments of elevated surfaces preserved east and adjacent to the Claremont fault provide five new vertical displacement rates along the badlands. OSL dates and stream profile analysis suggest that basin subsidence within the Casa Lorna pull-apart basin is the main factor controlling the formation of San Timoteo Badlands topography, and that there is currently little uplift in the northern portion. of the badlands.</p>

<p>Dissolutional features called karst exist on the surface, and in the subsurface as caves. In glaciated regions caves were thought to be post-glacial in origin. Work in the 1970s demonstrated that pre-glacial caves existed, but did not answer if a cave could form post-glacially. A model proposed by Mylroie and Carew (1987) states that a post-glacial cave would be controlled entirely by glacial features and the deranged drainage of glaciated terrains. Caves known as maze caves form at maximum rates, and could form to navigable size in the time since deglaciation. Maze caves form in the shallow subsurface, allowing them to be removed in subsequent glaciations. GIS water flow analysis, and calculation of formation times using cross-section data demonstrates that maze caves in the glaciated region of New York are post-glacial in origin fitting in the deranged drainage and forming in the time since deglaciation. </p>

<p> Mohawk Valley is an inter montane basin with a rich Quaternary record, located at the northernmost end of the Sierra Nevada Mountains in northeastern California. Geologic mapping of surficial deposits, stratigraphy, tephrochronology, geomorphology, and soil development were used to interpret the past 740 ky of Quaternary history of Mohawk Valley. The robust tephrochronologic record within Mohawk Valley includes twenty-six different tephras and sixty-seven tephra beds that range in age from 740 to 7 ka. Geochemical analyses and correlations with previously identified volcanic tephras have resulted in revised age estimates for tephra beds distributed within, and beyond, Mohawk Valley. </p><p> The tephra beds were deposited in lacustrine deposits of Mohawk Lake. Elevations of shorelines and minimum lake-levels based on elevations of waterlain tephra beds were used to reconstruct the history of Mohawk Lake. Mohawk Lake began to fill prior to 740 ka and continued to fluctuate, but overall rise, until after 175-235 ka when the lake reached the sill elevation, began to spill to the west, then incrementally lower and empty by ~7 ka. Throughout this period, there were at least five, and up to nine, different generations of glacial deposits that extended towards Mohawk Lake. These glacial deposits have been mapped, their soil development and weathering properties characterized, and ages estimated based on stratigraphic relations with tephra beds deposited within Mohawk Lake deposits. This mostly continuous, 740 ky record of sedimentation has enormous potential to examine paleoclimate in this area from any of a number of paleoclimate proxies. </p><p> The interpretation that a deep lake existed in Mohawk Valley requires a mechanism to allow for deposition and preservation of organic-rich deposits in deep water. Mohawk Lake was likely a meromictic lake, a setting that leads to an anoxic environment that can preserve organic-rich sediments such as those found in Mohawk Valley. In addition, shorelines around Mohawk Valley and across much of the Mohawk Valley Fault Zone are at consistent elevations suggesting there is not a significant vertical component of faulting since 175-235 ka, and maybe since 570-610 ka. This indicates a change from the history of subsidence since the early Pliocene.</p>

<p> Tropical Storm Debby affected the Gulf coast of Florida in late June, 2012. The storm's southerly approach temporarily reversed the annual net southward longshore sediment transport. The energetic conditions associated with Tropical Storm Debby can be seen in the wind, wave and tidal measurements taken from both onshore and offshore weather stations around the dual tidal inlets system of John's Pass and Blind Pass, approximately 25 kilometers north of the mouth of Tampa Bay. The energetic and persistent southerly forcing, in addition to higher storm induced water levels and wave heights, resulted in atypical beach erosion and sediment deposition on the ebb tidal deltas of the two inlets and the surrounding beaches. The John's Pass ebb delta gained 60,000 cubic meters of sediment and the Blind Pass ebb delta gained 9,000 cubic meters as a result of the storm. Shoreline position, beach profile and offshore bathymetric surveys conducted before and after Tropical Storm Debby illustrate the changes in the coastal morphology such as the development of an offshore bar south of Blind Pass and erosion of the dry beach north and south of John's Pass. The Coastal Modeling System (CMS) was used to simulate wave and tide-driven current fields during the passage of the storm. The modeled wave field qualitatively illustrated the shadowing effect of the Tampa Bay ebb delta in reducing the southerly approaching storm wave energy arriving at the study area during the storm. The tidal flow patterns through the inlets and over the ebb tidal deltas were considerably different during the storm, as compared to normal tidal cycles.</p>

Thesis (M.S. - Geology)--University of Arizona. / Bibliography: leaves 33-34.

<p> Mickey Springs in the Alvord Desert, southeast Oregon, is analogous to other Basin and Range hydrothermal systems where the requisite conditions of heat source and permeable pathways are met through crustal thinning due to normal faulting. This study examines the morphology and lifespan of near-surface spring features through use of ground penetrating radar, thermoluminescence (TL) dating, and elevation modeling. Duration of hydrothermal activity at Mickey Springs has not previously been determined, and age determinations of sinter at the site are conflicting. The reason for and timing of this change in silica saturation in the hydrothermal fluid has not been resolved.</p><p> Three morphologies of silica sinter deposition have been identified at Mickey Springs. These are (1) well-sorted, fine-grained sandstone with ripple marks, cross beds and preserved root casts, to poorly-sorted conglomerate of primarily basalt clasts, both cemented by coeval silica deposition, (2) large depressions (12-32 m diameter) rimmed with sinter, characterized by fine silt and clay blanketing a sinter apron and infilling the central depression, and (3) quaquaversal sinter mounds identified by outcropping pool-edge sinter typically surrounding a shallow depression of loose sediment.</p><p> Silica-cemented sandstone and conglomerate were the first features formed by coeval hydrothermal processes at the site, and were emplaced prior to 30 kya as suggested by structural and stratigraphic relationships. Structure between two interacting fault tips may have constrained the extent of silica cementation. By 30 kya, a left-stepping fault oriented roughly north/south further constrained the near-surface permeable zone. TL dates from sediment stratigraphically below and above sinter aprons around mounds and depressions (former spring vents) indicate sinter deposition between 30 and 20 kya. Location of these features was dictated by development of the left-stepping fault. As pluvial Lake Alvord filled at the end of the Pleistocene, lake sediment filled most vents, which were largely inactive, with fine-grained silt and clay.</p><p> Today, hydrothermal activity persists in two modes: (1) The current high-temperature springs, steam vents and mudpots concentrated in a 50 x 50 m area south of the sinter mounds and depressions, and (2) scattered springs and steam vents that exploit previous permeable pathways that once provided the hydrothermal fluid which precipitated the sinter aprons. Currently there is no active silica sinter deposition at Mickey Springs.</p><p> Structures and stratigraphic relationships identified through this study favor a transport-limited and structurally controlled model of fluid transport. Sinter deposition is determined to have occurred before the most recent highstand of pluvial Lake Alvord. A climate driven model, where groundwater recharge from pluvial Lake Alvord circulates to a deep heat source and enhances spring discharge, is not supported by these findings, as no evidence was found for sinter precipitation after the drying of the lake. Future studies of other hydrothermal systems in the Basin and Range may reveal that permeable pathways along local structures are the primary drivers in this region.</p>

Thesis (M.S.)--University of Missouri, School of Mines and Metallurgy, 1951. / Vita. The entire thesis text is included in file. Typescript. Title from title screen of thesis/dissertation PDF file (viewed December 15, 2009) Includes bibliographical references (p. 120-123).