Serpentinite emplacement in southwestern Puerto Rico indicates a complex plate boundary history between the Caribbean and North America plates. In this study we investigate the kinematics of shear planes within the serpentinite to improve constraints on the tectonic evolution of the region. Shear planes collected within the Monte del Estado and Río Guanajibo serpentinites reveal two predominant groups. One group comprises northwesterly-striking thrust faults and easterly-striking left-lateral faults. A second group comprises northwesterly-striking right-lateral faults and easterly-striking thrust faults. These shear zones reveal two shortening directions that trend NE-SW and N-S. The N-directed shortening is interpreted be older and subsequent stress reactivated the shear planes. The SW-directed shortening is attributed to transpression that caused contraction, uplift, and left-lateral shearing of serpentinite. A subsidiary younger group comprising fewer faults consists of northerly-directed thrusts and northwesterly-directed left-lateral faults and may be related to the last transpressional deformation within Puerto Rico. Thin-section observations show that porphyroclastic peridotite with pyroxenes that are kinked, show deformation lamellae, undulose extinction, and define foliation and lineation. Olivine shows a granuloblastic texture, and many crystals are strain-free and show polygonization indicating recrystallization. These textures indicate high temperature deformation that formed prior to serpentinization. Crystal-plastic deformation, recorded by serpentine mylonite and serpentine veins, was followed by brittle faulting. These structures demonstrate that the serpentinite was deformed and uplifted by tectonic stresses at the Caribbean-North America plate boundary zone and not by diapirism as a result of buoyancy differences within the crust. In southwestern Puerto Rico serpentinite emplacement has been described as first by collisional processes and second by diapirism. Structure mapping of the Monte del Estado and Río Guanajibo serpentinite bodies indicate that serpentinite was emplaced by thrusts verging towards the southwest in early Tertiary time. The thrust faults are mostly blind and produced fault-propagation folds in the overlying Late Cretaceous and Tertiary volcano-sedimentary cover. Low-angle thrusts are exposed in places at the southern contact of the Monte del Estado and Río Guanajibo serpentinite bodies and are interpreted to form part of the transpression that occurred in middle Tertiary at the boundary of the Caribbean-North America plates.

A 47.0 cm lake core was taken from Panther Hollow Lake, a small manmade lake located in Schenley Park within the City of Pittsburgh. The core was analyzed for geochemical evidence of the regions industrial history during the twentieth century. Physical and geochemical proxies showed that the lake sediments contained trace metal concentrations that are an order of magnitude above natural background levels, including high levels of heavy metals throughout the period of study and increasing concentrations of alkali and alkali earth metals. Lead was found at concentrations as high as 350 ppm in the core although chromium, arsenic, nickel, and vanadium are all well above background levels throughout the twentieth century. Depths were converted to age assuming a 0.5 cm/yr sedimentation rate. Using this age model, the shifts in concentrations of the industry-related metals align with changes made to environmental laws and industrial output in the region.

Till deposits, related to advances of mountain glaciers, and lake sediments record periods of abrupt warming and cooling during the Late Glacial interval (LG) (17,500 to 11,650 cal yr BP) in the northern tropical Andes. The synchronicity of temperature shifts in the tropical mountains and high northern latitudes during this period indicates that the low latitude atmosphere played a major role in LG abrupt climate change. Generally, the northern tropics are cold and dry when temperatures are lower in the North Atlantic region, and the opposite occurs during warm periods. The pattern of abrupt seesaw-like hemispheric temperature shifts, and the apparent link to tropical atmospheric dynamics, demonstrates the importance of low latitude circulation and water vapor feedbacks in rapid climate change. Geologic evidence from the precipitation-sensitive southern tropical Andes were used to reconstruct periods of ice advances and retreats during the Late Holocene. Neoglaciation in the Cordillera Raura of Peru began at ~3100 cal yr BP, marking a transition to a prolonged period of increased moisture transport to the Andes. The most extensive neoglacial advance took place locally during the Little Ice Age when conditions were both wetter and colder. The long-term, Holocene pattern of renewed ice cover in this region of the Andes was probably enhanced by astronomical forcing and convection-driven changes in moisture availability. Short-term glacial variability during the neoglacial was likely driven mostly by a combination of solar, atmospheric and oceanic processes. Lake sediments from the Pacific region of Nicaragua were used to record changes in the regional moisture balance during the late Holocene (~1600 cal yr BP to the present). Oxygen isotope values of calcium carbonate down-core identify periods of lake level fluctuations that resulted from changes in precipitation and evaporation rates. The driest regional conditions recorded in the isotope data are coincident with the onset of Little Ice Age cooling. This abrupt transition to more arid atmospheric conditions at 700 cal yr BP is consistent with other records from the northern tropics and subtropics that suggest hydrologic changes in the tropics were connected to high latitude climate variability during the late Holocene.

High-resolution sediment archives from small alpine lakes in the Alaskan Arctic and tropical Andes were used to investigate Holocene climate change in these climatically sensitive and important regions. Varved minerogenic sediments from glacial-fed Blue Lake, Brooks Range Alaska (1275 m asl), were used to derive a proxy temperature record between AD 730-2005. Cool temperatures characterize the late Holocene (last millennial average, or LMA = 4.2 °C) with 20th century warming anomalous within the context of the last 1275 years (0.8°C above LMA). However, temperatures between AD 1350-1450 and AD 1500-1620 approached modern values (0.4 and 0.3°C above LMA, respectively). Prolonged cooling at Blue Lake occurred from AD 1620-1880, during the Little Ice Age (LIA). LIA cooling and 20th century warming correspond to radiative minima and maxima, respectively. However, the relationship between radiative forcing and temperature is not consistent through the record, suggesting that other factors contributed to temperature variability in this region. In the tropics, South American summer monsoon (SASM) variability during the last 2300 years was reconstructed from oxygen isotope ratios of authigenic carbonate (δ18Ocal) preserved in varved sediments from Laguna Pumacocha (4300 m asl), Peru. High δ18Ocal values and reduced variability during the Medieval Climate Anomaly (MCA; AD 920-1050) suggest that the SASM and El Niño-Southern Oscillation (ENSO) were weak due to reduced easterly tropospheric flow and cooling within the eastern tropical Pacific (ETP). Low δ18Ocal from during the LIA (AD 1415-1820) and enhanced variability from AD 1415-1770 suggest that the SASM and ENSO were strong as a result of enhanced easterly tropospheric flow and warm, but variable, sea surface temperatures in the ETP, respectively. These ocean-atmosphere responses reflect the tropical Pacifics response to radiative forcing described by the ocean dynamical thermostat model (Clement et al. 1996). Long-term δ18Ocal trends at Pumacocha suggest that the SASM was weak during the early Holocene and then strengthened through the Holocene as Southern Hemisphere insolation increased. This confirms the importance of orbital controls on SASM dynamics. However, the Andean SASM strengthened to a greater extent than the SASM over the Amazon basin, indicating that these regions respond differently to similar forcing mechanisms.

Thermal infrared (TIR) remote-sensing and field-based observations were used to study aeolian systems, specifically sand transport pathways, dust emission sources and Saharan atmospheric dust. A method was developed for generating seamless and radiometrically accurate mosaics of thermal infrared data from the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) instrument. Using a combination of high resolution thermal emission spectroscopy results of sand samples and mosaic satellite data, surface emissivity was derived to map surface composition, which led to improvement in the understanding of sand accumulation in the Gran Desierto of northern Sonora, Mexico. These methods were also used to map sand transport pathways in the Sahara Desert, where the interaction between sand saltation and dust emission sources was explored. The characteristics and dynamics of dust sources were studied at White Sands, NM and in the Sahara Desert. At White Sands, an application was developed for studying the response of dust sources to surface soil moisture based on the relationship between soil moisture, apparent thermal inertia and the erosion potential of dust sources. The dynamics of dust sources and the interaction with sand transport pathways were also studied, focusing on the Bodele Depression of Chad and large dust sources in Mali and Mauritania. A dust detection algorithm was developed using ASTER data, and the spectral emissivity of observed atmospheric dust was related to the dust source area in the Sahara. At the Atmospheric Observatory (IZO) in Tenerife, Spain where direct measurement of the Saharan Air Layer could be made, the cycle of dust events occurring in July 2009 were examined. From the observation tower at the IZO, measurements of emitted longwave atmospheric radiance in the TIR wavelength region were made using a Forward Looking Infrared Radiometer (FLIR) handheld camera. The use of the FLIR to study atmospheric dust from the Saharan is a new application. Supporting data from AERONET and other orbital data enabled study of net radiative forcing.

The Las Vegas Valley Shear Zone, a right lateral strike slip fault that trends >100 m at N60W, makes a right step east of Beatty, Nevada resulting in detachment faulting and rhyolitic volcanism characteristic of the South West Nevada Volcanic Field. In the Fluorspar Canyon region of the field area, the Fluorspar Canyon-Bullfrog Hills (FC-BH) detachment dips 40° N and separates Late-proterozoic and Paleozoic strata in the footwall from Tertiary Volcanics and sediments in the hanging wall. To the east, the detachment links with the moderately dipping Tates Wash Fault. After removing the 40°N tilt, these two structures form a listric normal fault that cuts through the Paleozoic and into the crystalline basement. The hanging wall does not crop out in the field area and may be represented by the strata of the Grapevine Mountains of Death Valley. Extension along the FC-BH detachment migrates westward and occurs in previously recognized pulses. Expansive breccias are a distinctive feature in the field area and are directly related to extension. This study examines mapped breccias to determine their origin and relationship to deep structures in the field area. Deposits related to deep structures may influence the flow of possibly contaminated groundwater from Pahute Mesa in the Nevada Test Site southwest into the Beatty region. Breccias are interpreted to be deposited as large slide masses or accumulated in extension-related low areas. Groundwater flows southwest possibly using the NE trending Thirsty Canyon Lineament as a pathway. Water ponds against the east side of the N- trending Hogback Fault as suggested by the presence of numerous springs. The breccias mapped in the study area are not directly fault related, do not cut the underlying detachment, and do not significantly influence groundwater flow. Flow continues southward into the Beatty, Nevada region via the Amargosa River.

The major element and strontium isotope systematics and geochemistry of coal utilization byproducts (CUB) and their interactions with environmental waters were investigated using laboratory leaching experiments with water, sodium carbonate, acetic acid, nitric acid, and hydrochloric acid. Analysis of elemental data from both column and sequential leaching procedures shows rapid release of most major elements early in the leaching procedure, excluding silicon and iron, suggesting association with soluble and surface bound phases. Possible sulfate mineral phases can be inferred due to the high proportions of S leached with sodium carbonate solution, effective at dissolving sulfates such as anhydrite (CaSO3). For all elements except sulfur, highly acidic leachates were most effective in extracting elements from the CUB. In both the column and sequential leaching procedures silicon was leached most effectively by stronger acidic solutions later in the experiment, suggesting the presence of a more resistant silicate phase, possibly residual biotite, feldspar, or clays, or an amorphous glass phase formed during combustion. Isotopic results from the column leaching experiment show a marked increase in 87Sr/86Sr ratio with continued leaching. This general trend is also seen in the sequential leaching data, showing an increase in 87Sr/86Sr ratio with continued leaching in increasingly acidic solutions. These data show that there are isotopically distinct phases within the CUB, suggesting the presence of a more resistant, highly radiogenic phase that survives the combustion process and is leached after the more soluble minerals are removed. The Sr isotope systematics and leaching behavior of the Class F CUB samples demonstrate that isotopic homogenization of minerals in coal does not always occur during the combustion process, despite the high temperatures encountered in the boiler. A key factor in accessing more resistant phases within CUB appears to be the extent of leaching, rather than the particular leaching procedure or acid used. Early-released Sr tends to be isotopically uniform; thus the Sr isotopic composition of CUB could be distinguishable from other sources and a useful tool for quantifying the possible contribution of fly ash leaching to the total dissolved load in natural surface and groundwaters.

Fossil fuel combustion from point and mobile sources is a key contributor to atmospheric CO2, a major greenhouse gas, and NOx, a precursor to acid rain and smog. Increased concentrations of these pollutants are found near the sources, i.e., in urban areas and close to roadways. Vegetation in urban and near-road environments represents an important sink for anthropogenic inputs of NOx and CO2, and understanding the nutrient dynamics of vegetation in urban and near-road ecosystems is critical to understanding budgets of NOx and CO2. However, little is known about how these ecosystems compensate for higher local atmospheric CO2 and NOx concentrations. This study uses stable isotope geochemistry to trace atmospheric nutrients to urban and roadway vegetation. Chapter 1 presents an introduction to the environmental problems associated with atmospheric reactive nitrogen and CO2, the use of stable isotopes to determine the sources of these pollutants, and a review of recent studies which use stable isotopes to determine the sources of plant nutrient uptake. The study described in Chapter 2 examines the fate and transport of gaseous reactive nitrogen from mobile sources along a highway road gradient. This study uses stable isotopes of nitrogen in dry nitrogen deposition to examine the extent of nitrogen loading along a gradient perpendicular to a major highway. In addition, this study examines the effects of increased roadway N deposition on local vegetation by using the isotopic composition of plant tissue as a biomonitor of atmospheric N exposure. Chapter 3 details a similar study; however it is scaled up to an urban to rural gradient. This study used similar methods to the road gradient research, but examines N deposition at urban, suburban and rural sites in two metropolitan areas.

The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) was launched in December 1999 as one of five instruments on the NASA Earth Observing Systems (EOS) Terra satellite, and has proven effective for the detection and monitoring of volcanic eruptions and their associated products (Ramsey and Dehn, 2004). However, continuous advancement in analytical remote sensing techniques remains essential. For example, features associated with active volcanism commonly 1) are below the spatial resolution of the instruments 2) are more indicative of the state of volcanic unrest 3) tend to saturate thermal infrared (TIR) sensors due to their high thermal output. In addition, compositional, textural, and thermal heterogeneities can vary greatly within one 90 m TIR pixel, making accurate analysis and interpretations almost impossible without advanced techniques. Previous studies have shown that the radiance of an isothermal surface can mix linearly with respect to composition and texture, whereby emitted or reflected energy (TIR) from a heterogeneous surface is a combination of the radiance from each component proportionally to its areal percentage. However, where thermal mixing of a targets surface is involved, this technique is no longer valid, requiring alternative approaches to the solution. A thermal deconvolution algorithm has been developed to identify thermally mixed pixels and separate them into their hot and cool thermal components using archival and Urgent Request Protocol (URP) data from the higher spatial resolution shortwave (SWIR) bands of ASTER. These datasets targeted three active basaltic volcanoes exhibiting various thermal states including high-temperature lava flows with minimal SWIR saturation (Kilauea, Hawaii), low-temperature fumarole fields (Cerro Negro, Nicaragua), and high-temperature flows with significant SWIR saturation (Kliuchevskoi, Kamchatka). The results of this study show that this algorithm provides more accurate temperature estimates and corrections to the emissivity for better compositional mapping of the surface where SWIR radiance values do not approach minimum and maximum thresholds within each TIR pixel. This approach also serves as a rapid means for accurately identifying sub-pixel temperatures and minimizes the processing time, therefore allowing critical information to be quickly disseminated on these processes and hazards, which are commonly obscured in low to medium-spatial resolution orbital datasets.

This work focuses on the geochemistry and iron isotope systematics of pyrite from hydrothermal and coal-forming environments. Dissolution of pyrite, even under abiotic conditions, is difficult to study experimentally and previous studies have demonstrated that the rate of pyrite oxidation is dependent upon environmental conditions. Knowledge of dissolution mechanisms enables more accurate reaction rate measurements, and will improve the ability to predict the temporal changes in chemistry of ground and surface waters that come into contact with pyrite. The first aspect of the research presented here focuses on the need for standardization of sample preparation techniques to allow for experimental and interlaboratory comparison of pyrite dissolution experiments. A reproducible sample preparation technique for pyrite that yields clean, uniform grains within a narrow size range of interest was developed. It was shown that use of this method in pyrite dissolution experiments significantly reduces artifacts related to unconstrained surface area exposure to fluids. In the second portion of this work, iron isotopes were analyzed to quantify and source-track the dissolution of pyrite during abiotic pyrite dissolution experiments performed on hydrothermal and sedimentary pyrites. The hydrothermal pyrite δ⁵⁶Fe values fall within the range of previously measured values, but the coal/sedimentary values are higher than those previously measured for any Phanerozoic sedimentary pyrite. Leachates from oxidative dissolution of the pyrite at pH=3 tend, with minor exceptions, to yield δ⁵⁶Fe values equal to or below those of the coexisting bulk pyrite, by up to ~1‰. This is generally consistent with theoretical fractionation calculations. Iron isotopes could be a useful tool in distinguishing between waters that interact with coal-derived pyrite and pyrite formed under marine conditions. The third section focuses on extracting sedimentary pyrite and other minerals under typical near-surface temperatures and environments, which is complicated by the small grain size and complex nature of the phases found in the sedimentary environment. An extraction method was developed to better characterize the nature of iron behavior between phases present in coal forming environments. A proposed iron extraction method and testing procedure is outlined for future studies of Fe speciation in coal.