Thesis (M.S.)--Oregon State University, 2006. / Printout. Includes bibliographical references (leaves 66-69). Also available on the World Wide Web.

Paleoflood data are restrictive reflections of climatic conditions, representing one component of a region's climate; high rainfall intensity storms. In regions with a fairly simplistic, uniform hydroclimatological setting (floods above a given magnitude threshold are caused by predominantly one type of atmospheric circulation pattern), the temporal distribution of floods reflects that of the causal circulation pattern. Slackwater-deposit-based paleoflood reconstructions for three rivers in northern Australia cover an aggregate of 1200 years. Slackwater deposits (SWD) are fine-grained sediments which settle from suspension in low velocity areas during floods. These deposits approximate the flood's high water level, and allow reasonably accurate estimation of discharge. Radiocarbon dating of associated organics, and thermoluminescence (TL) dating of the 90-125 μm quartz fraction of the sediments, produce a paleoflood chronology. In this study, radiocarbon ages on SWD ranged from 1200 yr BP to modern, while TL ages on SWD and other fluvial sediments ranged from 2.6 to 60 ka. TL dating appears to have a large temporal range (1-100 ka) and a restricted spatial range (the lower reaches of a basin), while radiocarbon dating has a more restricted temporal range (0-35,000 yr BP) and a large spatial range (anywhere in the basin). The northern Australian paleoflood data formed clusters at 300-440 yr BP and 160 yr BP-present. This distribution is attributed to variations in the intensity of the El Nino/Southern Oscillation (ENSO) circulation (which prevents floods from occurring in northern Australia), and the anti-ENSO circulation (which is associated with large floods).

Within the constraints of uncertainty in the nature of erosion and transport in the sub-glacial environment, the study of glacialy-derived material from marine sediments located off the margin of East Antarctica provides a means for characterizing the sub-glacial geology obscured by the more than 98% ice cover of the continent. These insights into the geology of East Antarctica in turn provide characterization of sedimentary source areas, the knowledge of which can be applied to sediment provenance studies of ice rafted detritus (IRD) and thus about East Antarctic ice sheet history. Much of what has been learned of East Antarctica's Cenozoic ice sheet evolution has been achieved through the study of marine sediments, as ice sheets tend to erode their own history and much of what is preserved is, like the geology, obscured the ice sheet. Determining the provenance of ice-rafted detritus allows for spatial and temporal reconstructions of ice sheet behavior. Accordingly sedimentary provenance studies are key to documenting how Antarctica's ice sheet evolved through the Cenozoic. In this work, I have taken samples of marine sediments and used grain size and physical properties to separate different terrigenous components, and I have examined the sand fractions under a microscope. Following the sedimentological characterization, I have separated specific minerals from the sand fraction and employed isotopic measurements - 40Ar/39Ar on detrital hornblende and biotite grains, U-Pb on detrital zircons. I have also employed Nd isotope measurements on the terrigenous fine (< 63µm) fractions of these same samples. Chapter 2 is published in the journal Paleoceanography, and chapters 3 and 4 are to be submitted to Earth and Planetary Sciences and Paleoclimatology, Palaeoecology & Paleoceanography, respectively. In Chapter 2, I demonstrated that (1) four main sectors between the Ross Sea and Prydz Bay, separated by ice drainage divides, are distinguishable based upon the combination of 40Ar/39Ar ages of detrital hornblende and biotite grains and the εNd of the bulk fine fraction, (2) 40Ar/39Ar biotite ages can be used as a robust provenance tracer for this part of East Antarctica, and (3) sediments shed from the coastal areas of the Aurora and Wilkes sub-glacial basins can be clearly distinguished from one another based upon their isotopic fingerprints. This is particularly significant as the Aurora and Wilkes sub-glacial basins have elevations significantly below sea level, and thus are likely prone to being destabilized during warm climates. My work confirms and extends previous published evidence for episodes of massive ice rafting from these sectors. In Chapter 3, I addressed the relative merits of U-Pb zircon and the 40Ar/39Ar hornblende and biotite systems for sedimentary provenance studies. U-Pb zircon is a widely used detrital provenance tool. In polar and subpolar regions where chemical weathering is minor, hornblende and biotite are viable alternatives, and because they are more abundant in crystalline rocks it is possible to find significant populations in the relatively small samples that are available from marine sediment cores. My work has demonstrated that (1) detrital U-Pb zircon, 40Ar/39Ar hornblende and 40Ar/39Ar biotite ages all faithfully record the geologic history of East Antarctica, as expressed in their respective age populations, although different aspects may be accentuated in one or another (2) a number of previously unknown source regions have been identified (though not found on the continent yet) with this method (3) there is benefit to combining the three chronometers where possible as they are not completely redundant. Chapter 4 concerns the middle-Miocene climate transition (MMCT) on the Wilkes Land margin. In this study I combined 40Ar/39Ar with εNd of the terrigenous fine fraction across the MMCT in IODP Site U1356. The results from the two size fractions tell different stories and provide further support for the application of multiple tools. Specifically I found that (1) the hornblende ages in the MMCT of Site U1356 have a very dominant 1400-1550 Ma age population, which is not commonly found on the Wilkes land margin. I interpret these results, in the context of published geophysical interpretations of the sub-glacial geological boundaries, to require that the EAIS was greatly retreated in the Wilkes sub-glacial basin prior to and during the MMCT, and sat along the extension of the Mertz Shear Zone, at the western edge of the Wilkes Basin (2) While the hornblende evidence for provenance does not indicate large changes in iceberg sources, the εNd of the bulk fine fraction shows excursions to more radiogenic Nd values, 8 epsilon units higher than the local signal during times of elevated IRD concentrations at this site. The data reveal evidence for three events, which closely correspond with periods of glacial outburst floods responsible for carving part of the spectacular scabland topography (the Labyrinth) found in the Dry Valleys, and with provenance signals consistent with a significant sediment contribution from such a source and (3) the major pulse of dropstones to IODP Site U1356 occurs between ~14.0 and ~13.7 Ma, corresponding to the timing of the major pulse of IRD at ODP Site 1165 from near Prydz Bay, as well as to the timing of published records interpreted to indicate significant ice volume growth from oxygen isotope records and eustatic sea-level reconstructions. Collectively these observations allow tying together direct evidence for EAIS growth from proximal glacial-marine sediments and results from far field proxies. Overall, this work demonstrates the efficacy of isotopic and geochronological provenance tools for studying East Antarctica's geologic and ice sheet history. Furthermore the application of this approach to studying East Antarctic ice-sheet dynamics across the mid-Miocene Climate Transition (~14 Ma), one of the most important periods of East Antarctic ice sheet growth, highlights the powerful potential for future discoveries.

The Hudson River estuary (New York, USA) is a heavily urbanized estuary with a long history of environmental impacts from anthropogenic activities for hundreds of years. The estuary is intensely utilized, serving over ten million people throughout New York, Connecticut, and New Jersey. The portion of the Hudson River from Troy, NY to New York Harbor is tidal and is considered an important estuary. Tidal marshes are especially important for their roles in carbon sequestration, water filtration, primary production, flood-zone buffering, fisheries, and recreation. However, these valuable ecosystems are threatened by increasing anthropogenic activities, such as land clearing, channel modification, contamination release, and the introduction of invasive species (Howarth et al. 1991, Swaney et al. 1996, Pederson et al. 2005, Miller et al. 2006, Wall et al. 2008, Chou and Peteet. 2010, Nguyen and Peteet 2010, Collins and Miller 2011). In addition, projected warming, drought, sea level rise, and salt intrusion will likely amplify these anthropogenic effects (Bindoff et al. 2007, Christensen et al. 2007). Vegetation and sediment composition are two major keys that determine the health of the ecosystem. Thus, a necessary key in the restoration of the estuary is the understanding of baseline ecosystem and sedimental conditions as well as their long-term responses to climatic and anthropogenic activities. Such information is limited in the Hudson estuary (NYSDEC 2006, 2009, 2012). In this dissertation, we establish the baseline conditions of the vegetation and sediments of the Hudson Estuary using sediment cores from marshes and tributaries of the Hudson Estuary and investigate how the ecosystems have changed over time in response to major environmental changes. We expand paleoecological records in the freshwater section of the estuary to understand regional ecological changes as prior studies are restricted to the lower portion of the Hudson. An estuary-wide study of wetland and delta sediments across various environmental regimes aids our understanding of regional environmental shifts. We used two approaches to investigate environmental changes of the Hudson Estuary: 1) Long-term multiproxy paleoecological reconstruction at two important freshwater National Estuarine Research Reserve marshes; and 2) pre and post industrialization sediment composition analysis across a North-South transect of the river. Knowledge about past ecosystem structure and ecosystem response to anthropogenic and climatic changes can provide insights on how future changes may impact the ecosystem. Such information may be useful in future environmental management (Jackson and Hobbs 2009). In the first two chapters, we implement multiple proxies, including pollen, spores, macrofossils, charcoal, sediment bulk chemistry, and stable carbon and nitrogen isotopes to identify ecosystem changes spanning the past 1000 years in Tivoli Bays and Stockport Flats. Paleoecological reconstruction at both of these sites reveal climatic shifts such as the warm and dry Medieval Warm Period (MWP, 800 - 1300 AD) with high fire occurrence followed by the wetter cooler Little Ice Age (LIA, 1400 - 1800 AD), along with significant anthropogenic alterations in the watershed. Wetland and upland vegetation slightly changed during that period, reflecting water availability and temperature. The most striking changes occurred after the European settlement in the 17th - 18th centuries. Throughout the last century, invasive plant species including Typha angustifolia, Phragmites australis, and Lythrum salicaria pollen percentages increased by up to 20 times the pre-European settlement values, concurrent with marked changes in sedimentation rate, sediment composition, nutrient input, and organic content. Isotopic analysis of 13C at Tivoli Bays confirms major vegetation shifts concurrent with European settlement. The increase of fertilizer and sewage water was also visible by the enrichment of 15N in the sediment at the onset of European settlement. The concurrent trend of vegetation and sediment compositional changes suggests that sediment dynamics may play an important role in shaping wetland characteristics. In Chapter 2, the paleoecological result at Stockport Flats shows similar adverse anthropogenic impacts to the wetland as the biggest vegetation changes occurred at the onset of European settlement. In contrast to Tivoli, Stockport was a mudflat prior to the European settlement. As a result, Stockport has lower organic matter content (measured as Loss-On-Ignition (LOI)), less peat accumulation, and coarser grain size than Tivoli. This raises a question about what type of habitat should be targeted for conservation. A recently colonized wetland such as Stockport Flats does not serve the same function in carbon storage as an older wetland such as Tivoli. The third chapter is the first estuary-wide study of Hudson River sediment composition and sediment change before and after significant anthropogenic impacts. We characterize sediment composition at 20 wetlands and deltas across various environmental regimes from Troy, NY to the mouth of the Hudson River in New York Harbor. We identify natural and anthropogenic control of sediment dynamics in the estuary. Prior to the industrialization, LOI in older wetlands (24 % on average) is significantly higher than in new marshes and deltas (10% on average), indicating the importance of old wetlands as carbon sinks. After the European settlement, LOI markedly decreased and K, Ti, Rb, and Zr significantly increased in old wetlands as a result of the increase in land erosion and channel modification. Pb, Zn, Cu and Cr were found to be more enriched in relation to Sr than the upper continental crustal value by up to 180, 320, 100, and 18 times respectively as a result of anthropogenic input. During the process of correcting the signal for background metal level, we also found that the sediments from various settings have a wide range of background Pb of 8 - 80 ppm. Thus, the crustal Pb values that are commonly used for background correction of 20 - 25 ppm are not always applicable and detailed analysis of the actual background concentration at each location is necessary in order to accurately estimate anthropogenic contributions of industrial metals. Based on ecological and chemical proxies, we observe an enormous magnitude of change in vegetation, sedimentation rate, organic matter content, and nutrients during the last few centuries in the Hudson estuary, indicating significant anthropogenic influence on wetlands. Our estuary-wide sediment study indicates significant regional landscape change which results in an increase in inorganic matter input concurrent with vegetational shifts. The characterization of the baseline ecology and sediments in this study provides a guideline for ecosystem restoration and management to target the recovery and conservation of vegetation and sediment composition that is the most suitable for a given environment to fully reinstate ecosystem structure and function.

Ocean circulation plays an integral part in a multitude of Earth's processes including the transfer of heat and nutrients across the globe. Additionally, its role in initiating and/or responding to global climate change is thought to be significant though poorly constrained. One tool used to further understand the influence of changes in ocean circulation during climate transitions is paleocirculation records developed from deep sea cores. These records paint a picture of how ocean circulation changed throughout time and are composed of an array of elements and isotopes extracted from different sediment archives. Neodymium (Nd) isotopes have been applied to paleocirculation because of the geographic variability of these isotopes in seawater and their ability to be preserved in deep sea sediments. Nd isotope records have been extracted from Fe-Mn crusts, leachates of sediment coatings, fish debris and foraminifera dissolutions to investigate changes in circulation at both deep and shallow ocean depths. Several of these records have been developed to investigate changes in the amount of northern vs. southern sourced waters in the South Atlantic Ocean. The advancement of northern sourced waters into the South Atlantic and Southern Ocean is an important branch of the global ocean circulation system known as Atlantic Meridional Overturning Circulation (AMOC). In order to further investigate changes of AMOC in the South Atlantic, we have developed a Nd isotope record from Cape Basin core TN057-6 for the last ~400 kyr. In agreement with the literature, the developed Nd record shows a decrease in AMOC during the Last Glacial Maximum and for previous glacial stages. Interglacial or warm periods defined by increased AMOC of comparable magnitude to modern circulation. These findings are summarized in the first two chapters of this thesis. The potential for Nd isotopes (εNd) as a water mass tracer is dependent on a thorough understanding of Nd cycling within the water column. The use of Nd isotopes in the modern ocean is also a valuable tool for investigating biogeochemical cycles and environmental perturbations such as dust or freshwater inputs. The distribution of εNd within the oceans suggests quasi-conservative behavior, traces water masses and shows correlations with both salinity and silicate. However, one observation known as the "Nd-paradox" suggests there are some poorly constrained sources and sinks of Nd in the ocean. The "Nd-paradox" refers to an apparent decoupling of Nd isotopes and Nd concentration ([Nd]) within the water column. In order to explain such features and the Nd cycle as a whole, it is essential to expand the database of Nd seawater data. As part of the GEOTRACES initiative, there have been a growing number of studies to measure seawater Nd-composition. The last two chapters of this thesis focus on the Nd-composition of seawater samples collected along GEOTRACES cruise transect GA03 from Lisbon, Portugal to Cape Verde Islands to Woods Hole, USA. The major water masses sampled as part of this cruise are Mediterranean Outflow Water, Antarctic Intermediate Water, North Atlantic Deep Water and Antarctic Bottom Water. Additional features sampled are near shore and open ocean stations, the Saharan dust plume, an expansive oxygen minimum zone, nepheloid layers and a Mid-Atlantic Ocean Ridge hydrothermal site. For each sample we calculate a predicted Nd-composition based on water mass mixing. By comparing the predicted and measured Nd-composition, we are able to investigate how Nd deviates from conservative behavior. Results from this work show that εNd is predominately conservative at deep depths at open ocean stations and is sensitive to small changes in water mass end-member Nd-compositions. This finding has important implications for the way end-members are defined in paleoceanographic Nd studies. Hydrothermal inputs are shown to have no influence on the isotopic composition of nearby water mass εNd compositions. However, an expansive nepheloid layer in the deep western North Atlantic does influence seawater εNd. [Nd] does not show conservative behavior but rather follows the "Nd-Paradox" such that concentrations increase with depth across the basin and exceed predicted [Nd] values.

Thesis (Ph. D.)--West Virginia University, 2009. / Title from document title page. Document formatted into pages; contains xi, 240 p. : ill. (some col.), maps (some col.). Vita. Includes abstract. Includes bibliographical references.

Thesis (M.S.)--University of Wyoming, 2008. / Title from PDF title page (viewed on Jan. 19, 2010). Includes bibliographical references.

Thesis (Ph.D.)--University of Nebraska-Lincoln, 2009. / Title from title screen (site viewed January 5, 2010). PDF text: xx, 547 p. : ill. (chiefly col.) ; 47.3 Mb. UMI publication number: AAT 3360491. Includes bibliographical references. Also available in microfilm and microfiche formats.

Thesis (Ph. D.)--University of Washington, 2001. / Vita. Includes bibliographical references (leaves 121-129).

Project: Dendroclimatic History of the United States, Contract: E-41-70(N) / 1970 Final Report Prepared for: Laboratory for Environmental Data Research, Environmental Data Service, Weather Bureau, Environmental Science Services Administration, United States Department of Commerce / November 9, 1970 / Ring widths from trees on certain sites reflect climatic variation. Therefore, long time series derived from replicated and precisely dated ring-width chronologies may be utilized to extend climatic records into prehistoric times. Multivariate analyses of tree -ring chronologies from western North America are used to derive response functions from which one can ascertain what climatic information each ring -width chronology contains. In addition, multivariate analyses are utilized to calibrate a large number of ring -width chronologies of diverse response functions and from widely dispersed sites with a large number of regional climatic variables. A series of transfer functions are derived which allow estimates of anomalous climatic variation from tree -ring records. Reconstructions of anomalous variation in atmospheric circulation for portions of the northern hemisphere back to A.D. 1700 are obtained by applying the transfer functions to tree -ring data for time periods when ring data are available but climatic data are not.