Open Access. Powered by Scholars. Published by Universities.®
Physical Sciences and Mathematics Commons™
Open Access. Powered by Scholars. Published by Universities.®
- Institution
- Publication Year
- Publication
- Publication Type
Articles 1 - 15 of 15
Full-Text Articles in Physical Sciences and Mathematics
Geomorphic And Paleoclimatic Implications Of Glacial Extent Records In The Sierra Nevada Del Cocuy, Colombia During Termination 1, Jordan Nickerson Herbert
Geomorphic And Paleoclimatic Implications Of Glacial Extent Records In The Sierra Nevada Del Cocuy, Colombia During Termination 1, Jordan Nickerson Herbert
Dartmouth College Master’s Theses
Reconstructions of past glacial extents using geomorphic mapping and cosmogenic dating provide an opportunity to infer past climates. A record of the past extents of tropical mountain glaciers is particularly useful because there are few other means to reconstruct past temperatures in high-altitude, low-latitude locations. The tropics play an outsized role in mediating global climate, yet there is a lack of understanding of how the tropics may have influenced past climate changes such as the most recent deglaciation (Termination 1, ~18–11.7 ka). Improving reconstructions of tropical mountain glaciers will aid in understanding the role of the tropics in the global …
Evaluating Holocene Precipitation Variability In The Baltic Region Using Oxygen Isotopes Of Lacustrine Carbonate From Estonia, Maxwell Gordon Boes
Evaluating Holocene Precipitation Variability In The Baltic Region Using Oxygen Isotopes Of Lacustrine Carbonate From Estonia, Maxwell Gordon Boes
Graduate Research Theses & Dissertations
A high-resolution Holocene record of groundwater isotopic composition from eastern Europe enhances the current understanding of ocean atmosphere interactions and moisture transport dynamics. In the modern system, it has been established that the amount of regional winter precipitation is driven by the strength and direction of the sea level atmospheric pressure gradient over the Atlantic Ocean. This is defined by the North Atlantic Oscillation (NAO) index, that shows a positive correlation with precipitation amount during the cold season. This study aims to discover the link between atmospheric dynamics and the ratio of warm season to cold season precipitation through the …
Timescales Of Magma Transport In The Columbia River Flood Basalts, Determined By Paleomagnetic Data, Joseph Biasi, Leif Karlstrom
Timescales Of Magma Transport In The Columbia River Flood Basalts, Determined By Paleomagnetic Data, Joseph Biasi, Leif Karlstrom
Other Staff Materials
Flood basalts represent major events in Earth History, in part because they are linked to large climate perturbations and mass extinctions. However, the durations of individual flood basalt eruptions, which directly impact potential environmental crises, are poorly constrained. Here we use a combination of paleomagnetic data and thermal modeling to create a magnetic geothermometer (MGT) that can constrain the active transport lifetime of magmatic conduits and intrusions. We apply the MGT technique to eight feeder dike segments of the Columbia River basalts (CRB), demonstrating that some dike segments were actively heating host rocks for less than one month, while other …
Coastal Watershed Monitoring And Management: Geomorphology, Geochemistry, And Hydrologic Modeling Of Los Peñasquitos Creek, Ca, Ravleen Khalsa-Basra
Coastal Watershed Monitoring And Management: Geomorphology, Geochemistry, And Hydrologic Modeling Of Los Peñasquitos Creek, Ca, Ravleen Khalsa-Basra
Theses
Rivers in semi-arid climates are directly influenced by local geographic and hydrologic conditions and impacted by modifications to hydrology via urbanization. Changes can influence erosion, morphology, habitat sustainability, and watershed health. In highly urbanized southern California coastal regions, these rare open spaces provide vital ecosystem services. Los Peñasquitos Creek in San Diego County is one such watershed. Using stream surveying and laboratory methods we quantified channel characteristics, grain size distribution, total metal concentration [M], organic carbon (%OC), and phosphate to longitudinally characterize the creek for improved management. Results identified three distinct reaches in the watershed (upper, middle, lower). Downstream, depth …
Reconstructing Carbon Dynamics Of Alpine And Temperate Zone Lakes Using Stable Isotopic Analysis, Rebecca M. Doyle
Reconstructing Carbon Dynamics Of Alpine And Temperate Zone Lakes Using Stable Isotopic Analysis, Rebecca M. Doyle
Electronic Thesis and Dissertation Repository
Lake sediments integrate signals from the catchment, atmosphere and water column, offering a unique window through which to view changes in the carbon cycle. Carbon dynamics in lakes are changing due to nitrogen loading and anthropogenic climate warming (ACW), threatening the water quality of lakes. This thesis identifies how the carbon dynamics of lakes have responded to anthropogenically-driven forcings by comparing pre- and post- AD 1850 records preserved in lake sediments. First, the carbon dynamics of Barry Lake (Ontario, Canada), a low-elevation temperate lake, are investigated. Effective moisture (the net of water inputs and evaporation) is reconstructed using the carbon …
Evidence Of Variable Climate And Resources During The Late Pleistocene And Holocene At Gona, Ethiopia, Marie White
Evidence Of Variable Climate And Resources During The Late Pleistocene And Holocene At Gona, Ethiopia, Marie White
Steeplechase: An ORCA Student Journal
The African Humid Period (AHP) spanned a period of approximately 15 to 5 thousand years ago (ka) and resulted in Northern and Eastern Africa being wetter than today. This climate change event impacted flora, fauna, and humans to an unknown extent. Much of the work on the AHP across Eastern Africa utilizes lacustrine and marine proxies rather than river-based (fluvial). Gona, located in the Afar region of Ethiopia, is known for its extensive archaeological and fossil records in fluvial deposits. However, the paleoenvironment of the AHP at Gona has not been investigated. This study uses stratigraphy, geochronology, and paleopedology to …
Improving Thorium-230 Determination In Marine Sediment, Katherine Mateos
Improving Thorium-230 Determination In Marine Sediment, Katherine Mateos
Independent Study Project (ISP) Collection
Our oceans are intimately related to the climate of our planet. Paleoceanographic approaches aim to study oceans through geologic time to improve models of future climate. Radioisotopes provide us with chemical tracers that help us understand change through time. The uraniumseries decay chain contains thorium-230, a decay product of uranium-234. This isotope is useful to paleoceanographers in its disequilibrium to its parent isotope and in determining the flux of sediment falling to the ocean floor. In order to use 230Th to study oceans, we must be able to accurately measure the amount of thorium in sediment samples. Thorium is found …
Drip Water Measurements From Carlsbad Cavern: Implications Towards Paleoclimate Records Yielded From Evaporative-Zone Stalagmites, Victor J. Polyak, Jessica B.T. Rasmussen, Yemane Asmerom
Drip Water Measurements From Carlsbad Cavern: Implications Towards Paleoclimate Records Yielded From Evaporative-Zone Stalagmites, Victor J. Polyak, Jessica B.T. Rasmussen, Yemane Asmerom
International Journal of Speleology
Stalagmites can host numerous potential climate proxies (stable and radiogenic isotopes, trace elements, annual and non-annual banding, grayscale, growth hiatuses, mineral assemblage). Reproducibility and/or integration of proxy results between one or more stalagmites will become increasingly important, and ideally, climate records generated by multiple stalagmites from the same cave or cave room are expected to be near-identical. The reality is that stalagmites from the same cave room can yield differing results to some degree, especially in cave environment zones that are evaporative. Our drip water study in an evaporative shallow-depth cave environment in Carlsbad Cavern shows that adjacent drip sites …
Depositional And Environmental Controls On Oxygen And Carbon Isotope Compositions Of Late Pleistocene To Mid-Holocene Shelly Fauna From The Huron Basin, Ontario, Canada, Jane Wilson
Electronic Thesis and Dissertation Repository
The δ¹⁸O and δ¹³C of aragonitic mollusc shells were analyzed from nine sites in the Huron Basin, Ontario, Canada. These sites represent three lake phases spanning the Late Pleistocene to the mid-Holocene (Algonquin, Transitional, and Nipissing) and three depositional environments (fluvial, estuarine, and lacustrine). Depositional environment controls mollusc δ¹⁸O more strongly than climate. The source of carbon and climate control the δ¹³C of the shelly fauna. Shells from fluvial sites are most depleted of ¹⁸O and exhibit the greatest antipathetic δ¹³C-δ¹⁸O covariation. This reflects the dynamic nature of this system. Lacustrine sites have …
Testing Of The Late-Ordovician Pre-Gice Warm Water Carbonate Hypothesis In Alabama, Brandon Euker, Stacey Law
Testing Of The Late-Ordovician Pre-Gice Warm Water Carbonate Hypothesis In Alabama, Brandon Euker, Stacey Law
Senior Honors Projects, 2010-2019
The Guttenberg Carbon Isotope Excursion (GICE) (uppermost Sandbian-lower Katian, Late Ordovician) has been suggested to represent the transition from a Cambrian-Ordovician greenhouse world to Late Ordovician icehouse world. This transition is thought to coincide with a proposed shift from deposition of warm water carbonate rocks to cool water carbonate rocks in the North American midcontinent. We used oxygen isotopes (d18O) of conodonts to test the idea that the rocks below the GICE interval represent a consistently warm environment. Conodonts were isolated from samples of the Chickamauga Group collected at the Tidwell Hollow section in Blount County, AL, from …
Late Holocene Climate And Environmental Reconstruction Derived From The Asian Ice Core Array (Aica), Bjorn Grigholm
Late Holocene Climate And Environmental Reconstruction Derived From The Asian Ice Core Array (Aica), Bjorn Grigholm
Electronic Theses and Dissertations
Recent climate change has impacted natural and human systems across the Earth, emphasizing the need for greater understanding of both the existing and changing natural and anthropogenic forcing mechanisms and subsequent responses of the Earth’s climate system. High-resolution, multi-parameter ice core records retrieved and analyzed from two Asian Ice Core Array (AICA) sites, Geladaindong (central Tibetan Plateau) and Inilchek (central Tien Shan) were utilized to reconstruct atmospheric chemical concentrations and composition over the past ~100-500 years, improving the understanding of late Holocene climate and environmental variability in Asia. Both ice cores were analyzed for major and trace elements, major soluble …
Stable Isotope Paleolimnology Of Barry Lake, Ontario, Canada Since Ad - 1268, Zijun Liu
Stable Isotope Paleolimnology Of Barry Lake, Ontario, Canada Since Ad - 1268, Zijun Liu
Electronic Thesis and Dissertation Repository
The paleolimnology of Barry Lake, SE Ontario, Canada is described using mineralogy, magnetic susceptibility, carbon:nitrogen ratio, mass accumulation rates, grain-size, δ18O and δ13C of authigenic calcite and mollusc aragonite, δ13C and δ15N of organic matter, and archival records. These sediments span the Medieval Warm Period (MWP), Little Ice Age (LIA), and human settlement. Interval I proxies (AD 1268-1350, MWP) indicate warmer and drier conditions and elevated lacustrine production. Interval II (AD 1350-1615) was cooler and wetter, with lower lacustrine production and low-oxygen conditions causing loss of shelly fauna. Interval III (AD 1615-1850, …
7700 Years Of Holocene Climatic Variability In Sermilik Valley, Southeast Greenland Inferred From Lake Sediments, Samuel H. Davin
7700 Years Of Holocene Climatic Variability In Sermilik Valley, Southeast Greenland Inferred From Lake Sediments, Samuel H. Davin
Masters Theses 1911 - February 2014
During the latter half of the 20th century until present day there has been an unprecedented rise in global annual mean temperatures accompanied by rising sea levels and a decrease in Northern Hemisphere snow cover, which if it continues will lead to widespread disruption of climate patterns, ecosystems, and present-day landscapes. It is therefore of critical importance to establish an expanded network of paleoclimate records across the globe in order to better assesses how the global climate system has changed in the past, that we may create a metric by which to address modern change. Herein is presented a7,700 …
Cora – A Dedicated Device For Carbon Dioxide Monitoring In Cave Environments, Marc Luetscher, Felix Ziegler
Cora – A Dedicated Device For Carbon Dioxide Monitoring In Cave Environments, Marc Luetscher, Felix Ziegler
International Journal of Speleology
High resolution time-series of cave CO2 fluctuations are increasingly demanded to quantify calcite precipitation processes. CORA, an energy-efficient NDIR-device, has been specifically developed for the long-term monitoring of carbon dioxide in remote cave environments. To allow comparison between different cave sites, changes in air pressure and temperature are compensated for using dedicated probes. Laboratory experiments demonstrate that CORA’s precision is adapted to the analysis of spatially and temporally variable CO2 regimes and therefore suitable for a large number of applications. Data obtained with 12 independently calibrated instruments are reproducible within 3% (1σ). The two-point calibration function is validated …
Carbon And Sulfur Cycling In Early Paleozoic Oceans, Cara Kim Thompson
Carbon And Sulfur Cycling In Early Paleozoic Oceans, Cara Kim Thompson
Doctoral Dissertations
Here, I evaluate biospheric evolution during the Ordovician using high-resolution inorganic carbon and sulfur (carbonate-associated sulfate and pyrite) isotope profiles for Early Ordovician to early Late Ordovician strata from geographically distant sections in Western Newfoundland and the Argentine Precordillera. Additionally, I present new, high-resolution U-Pb ages for volcanic ash beds within strata of the Argentine Precordillera. Carbon isotope data record subdued variation that is typical of Early- to Middle Ordovician strata worldwide. By contrast, sulfur-isotopic compositions of carbonate-associated sulfate reveal a complex signal of short-term, rhythmic variation superimposed over a longer-term signal. This short-term, rhythmic variation occurs in all sections …