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Articles 1 - 30 of 35
Full-Text Articles in Life Sciences
Comparing Multiple Approaches To Reconstructing The Phosphorus History Of Marl Lakes: A Utah Lake Case Study, Mark R. Devey
Comparing Multiple Approaches To Reconstructing The Phosphorus History Of Marl Lakes: A Utah Lake Case Study, Mark R. Devey
All Graduate Theses and Dissertations, Spring 1920 to Summer 2023
Freshwater lakes around the world have suffered from the increasing occurrence of harmful algal blooms in recent decades. One of the most pressing reasons water quality managers try to address harmful algal blooms is that some of the species that occur with them produce toxins which can affect humans, pets, and wildlife. In many lakes, the nutrient phosphorus controls whether these harmful algal and bacterial species can occur. Therefore, efforts to control harmful algal blooms often center around reducing inputs of phosphorus from a variety of sources within the watershed. Scientists and water quality managers have long been challenged by …
Impact Of Prairie Restoration On Geochemistry And Microbial Communities In Groundwater, Kayla Koenig
Impact Of Prairie Restoration On Geochemistry And Microbial Communities In Groundwater, Kayla Koenig
Graduate Research Theses & Dissertations
Prairie restoration is important for reversing the loss of biodiversity and repairing ecosystem functions humanity is dependent on diverse ecosystems. This study looks at the impact of the beginning phases of prairie restoration on groundwater geochemistry and microbial communities the relationship between them. This research project studied the geochemistry and microbial communities in five wells before, during, and after the beginning phases of the first year of a prairie restoration on the Northern Illinois University campus. Water samples were collected bimonthly for a year and analyzed on an Ion Chromatograph. Microbial samples were collected monthly and underwent DNA extraction, amplification, …
A Record Of Vapour Pressure Deficit Preserved In Wood And Soil Across Biomes, Adrian Broz, Gregory J. Retallack, Toby M. Maxwell, Lucas C.R. Silva
A Record Of Vapour Pressure Deficit Preserved In Wood And Soil Across Biomes, Adrian Broz, Gregory J. Retallack, Toby M. Maxwell, Lucas C.R. Silva
Biology Faculty Publications and Presentations
The drying power of air, or vapour pressure deficit (VPD), is an important measurement of potential plant stress and productivity. Estimates of VPD values of the past are integral for understanding the link between rising modern atmospheric carbon dioxide (pCO2) and global water balance. A geological record of VPD is needed for paleoclimate studies of past greenhouse spikes which attempt to constrain future climate, but at present there are few quantitative atmospheric moisture proxies that can be applied to fossil material. Here we show that VPD leaves a permanent record in the slope (S) of least-squares …
Development Of A Synthesis Method For O2-Releasing Compound For Microbiological Experiments, Danae Greco
Development Of A Synthesis Method For O2-Releasing Compound For Microbiological Experiments, Danae Greco
Williams Honors College, Honors Research Projects
Many celestial bodies within our solar system may have habitable environments due to the presence of liquid water. Europa, one of Jupiter’s moons, may be habitable because of its liquid ocean and other potentially biologically favorable conditions. The ocean on Europa is hypothesized to contain large amounts of oxidants and low pH due to the radiolytically processed icy ocean shell. This suspected environment on Europa is similar to the composition of acid mine drainage on Earth, which can house microbial communities in environments of extreme acidity. Similar chemical reactions in Europa’s ocean may occur to produce the appropriate reduction-oxidation gradients …
Increased Dust Deposition In New Zealand Related To Twentieth Century Australian Land Use, Janice Brahney, Ashley P. Ballantyne, Marcus Vandergoes, Troy Baisden, Jason C. Neff
Increased Dust Deposition In New Zealand Related To Twentieth Century Australian Land Use, Janice Brahney, Ashley P. Ballantyne, Marcus Vandergoes, Troy Baisden, Jason C. Neff
Watershed Sciences Faculty Publications
Mineral aerosols (dust) generated in the dryland regions of Australia have the potential to reach New Zealand through atmospheric transport. Although a large portion of dust in New Zealand originates in Australia, little is known about how dust deposition has varied over time in New Zealand or what may have caused this variation. We used geochemical dust proxies to examine the recent history of dust deposition to two alpine lakes in Kahurangi National Park, South Island, New Zealand. Geochemical indicators suggest that dust deposition began to increase around 1900, with the greatest deposition rates occurring from ~1920 to ~1990. In …
Microbial Fe(Iii) Reduction As A Potential Iron Source From Holocene Sediments Beneath Larsen Ice Shelf, Jaewoo Jung, Kyu-Cheul Yoo, Brad E. Rosenheim, Tim M. Conway, Jae Il Lee, Ho Il Yoon, Chung Yeon Hwang, Kiho Yang, Christina Subt, Jinwook Kim
Microbial Fe(Iii) Reduction As A Potential Iron Source From Holocene Sediments Beneath Larsen Ice Shelf, Jaewoo Jung, Kyu-Cheul Yoo, Brad E. Rosenheim, Tim M. Conway, Jae Il Lee, Ho Il Yoon, Chung Yeon Hwang, Kiho Yang, Christina Subt, Jinwook Kim
Marine Science Faculty Publications
Recent recession of the Larsen Ice Shelf C has revealed microbial alterations of illite in marine sediments, a process typically thought to occur during low-grade metamorphism. In situ breakdown of illite provides a previously-unobserved pathway for the release of dissolved Fe2+ to porewaters, thus enhancing clay-rich Antarctic sub-ice shelf sediments as an important source of Fe to Fe-limited surface Southern Ocean waters during ice shelf retreat after the Last Glacial Maximum. When sediments are underneath the ice shelf, Fe2+ from microbial reductive dissolution of illite/Fe-oxides may be exported to the water column. However, the initiation of an oxygenated, …
Source, Transport, And Age Of Sediment From Cascade Volcano Watersheds To The Nearshore: Insights For Contaminant And Ecological Studies, Renee Takesue, Kathy Conn, Margaret Dutch
Source, Transport, And Age Of Sediment From Cascade Volcano Watersheds To The Nearshore: Insights For Contaminant And Ecological Studies, Renee Takesue, Kathy Conn, Margaret Dutch
Salish Sea Ecosystem Conference
Inputs of sediment and sediment-bound contaminants from urbanized watersheds to the nearshore region are a growing concern as coastal populations increase around the Salish Sea and worldwide. Geochemical sourcing and aging of nearshore sediment is one potential way to: a) distinguish land-derived sediment in nearshore environments, b) gain insights about how sediment and contaminants are redistributed, and c) determine how recently they were deposited. Sediments from Cascade volcanoes have distinct geochemical compositions that allow discrimination between land-derived (volcanic) and marine (lowland) sediment. As sediment is transported by rivers to the nearshore, it adsorbs particle-reactive contaminants and short-lived radionuclides, and the …
Catalyzed Synthesis Of Zinc Clays By Prebiotic Central Metabolites, Marcelo I. Guzman, Ruixin Zhou, Kaustuv Basu, Hyman Hartman, Christopher J. Matocha, S. Kelly Sears, Hajatollah Vali
Catalyzed Synthesis Of Zinc Clays By Prebiotic Central Metabolites, Marcelo I. Guzman, Ruixin Zhou, Kaustuv Basu, Hyman Hartman, Christopher J. Matocha, S. Kelly Sears, Hajatollah Vali
Chemistry Faculty Publications
How primordial metabolic networks such as the reverse tricarboxylic acid (rTCA) cycle and clay mineral catalysts coevolved remains a mystery in the puzzle to understand the origin of life. While prebiotic reactions from the rTCA cycle were accomplished via photochemistry on semiconductor minerals, the synthesis of clays was demonstrated at low temperature and ambient pressure catalyzed by oxalate. Herein, the crystallization of clay minerals is catalyzed by succinate, an example of a photoproduced intermediate from central metabolism. The experiments connect the synthesis of sauconite, a model for clay minerals, to prebiotic photochemistry. We report the temperature, pH, and concentration dependence …
Ancient Maya Agricultural Resources In The Rio Amarillo Valley Near Copán, Honduras, Bryce Matthew Brown
Ancient Maya Agricultural Resources In The Rio Amarillo Valley Near Copán, Honduras, Bryce Matthew Brown
Theses and Dissertations
The purpose of this study was to use soil physical and chemical analyses to better understand the ancient agricultural landscape around the ancient Maya cities of Rio Amarillo and Piedras Negras, two tributary sites to Copan, Honduras. Our primary objective was to determine whether a mass erosion event around 800 A.D. occurred which could have caused crop failure and famine or if stable soil conditions persisted during the collapse of these city-states. Stable carbon isotope analysis of the humin fraction of the soils showed that much of this valley was used anciently for agriculture, including hillslopes and hilltops; however, there …
An Investigation Of Hydrogeologic, Stratigraphic, And Structural Controls On Acer Grandidentatum Communities In A Karst Landscape, Owl Mountain Province, Fort Hood Military Installation, Texas, Melinda S. Faulkner
Electronic Theses and Dissertations
The Owl Mountain Province is located within the Fort Hood Military Installation, an approximately 880 km2 installation established in the 1940s in Bell and Coryell counties, Texas, which has undergone extensive land use changes associated with military training, maintaining much of the vegetation in early succession. This study investigates thelithologic, stratigraphic, and structural controls on the hydrologic, hydrogeologic, and geomorphologic evolution of the Owl Mountain Province as expressed by mesic vegetation communities, including Pleistocene relicts Acer grandidentatum, within karst terrains. These systems exhibit complexly overprinted speleogenetic evolutions within a dynamic groundwater regime resulting from regional climate shifts throughout the …
Exploring, Exploiting And Evolving Diversity Of Aquatic Ecosystem Models: A Community Perspective, Annette B.G. Janssen, George B. Arhonditsis, Arthur Beusen, Karsten Bolding, Louise Bruce, Jorn Bruggeman, Raoul-Marie Couture, Andrea S. Downing, J. Alex Elliott, Marieke A. Frassl, Gideon Gal, Daan J. Gerla, Matthew R. Hipsey, Fenjuan Hu, Stephen C. Ives, Jan H. Janse, Erik Jeppesen, Klaus D. Jöhnk, David Kneis, Xiangzhen Kong, Jan J. Kuiper, Moritz K. Lehmann, Carsten Lemmen, Deniz Özkundakci, Thomas Petzoldt, Karsten Rinke, Barbara J. Robson, René Sachse, Sebastiaan A. Schep, Martin Schmid, Huub Scholten, Sven Teurlincx, Dennis Trolle, Tineke A. Troost, Anne A. Van Dam, Luuk P.A. Van Gerven, Mariska Weijerman, Scott A. Wells, Wolf M. Mooij
Exploring, Exploiting And Evolving Diversity Of Aquatic Ecosystem Models: A Community Perspective, Annette B.G. Janssen, George B. Arhonditsis, Arthur Beusen, Karsten Bolding, Louise Bruce, Jorn Bruggeman, Raoul-Marie Couture, Andrea S. Downing, J. Alex Elliott, Marieke A. Frassl, Gideon Gal, Daan J. Gerla, Matthew R. Hipsey, Fenjuan Hu, Stephen C. Ives, Jan H. Janse, Erik Jeppesen, Klaus D. Jöhnk, David Kneis, Xiangzhen Kong, Jan J. Kuiper, Moritz K. Lehmann, Carsten Lemmen, Deniz Özkundakci, Thomas Petzoldt, Karsten Rinke, Barbara J. Robson, René Sachse, Sebastiaan A. Schep, Martin Schmid, Huub Scholten, Sven Teurlincx, Dennis Trolle, Tineke A. Troost, Anne A. Van Dam, Luuk P.A. Van Gerven, Mariska Weijerman, Scott A. Wells, Wolf M. Mooij
Civil and Environmental Engineering Faculty Publications and Presentations
Here, we present a community perspective on how to explore, exploit and evolve the diversity in aquatic ecosystem models. These models play an important role in understanding the functioning of aquatic ecosystems, filling in observation gaps and developing effective strategies for water quality management. In this spirit, numerous models have been developed since the 1970s. We set off to explore model diversity by making an inventory among 42 aquatic ecosystem modellers, by categorizing the resulting set of models and by analysing them for diversity. We then focus on how to exploit model diversity by comparing and combining different aspects of …
Indications Of Ancient Maya Soil Resource Management In Northern Belize, Austin Michael Ulmer
Indications Of Ancient Maya Soil Resource Management In Northern Belize, Austin Michael Ulmer
Theses and Dissertations
The objective of this study was to use soil chemical properties, particularly carbon isotopes to describe the agricultural landscape in the Blue Creek region on the Rio Bravo Escarpment in northwestern Belize. The primary question associated with this study focused on the comparative agricultural potential of the soils between the upland karst environment and the lowland coastal plains using the distribution and frequency of ancient Maya maize production. Soil physical features, such as clay concentrations throughout profiles in conjunction with soil chemical properties were used to aid in determining the level of ancient maize production. Isotopic evidence suggests that anciently, …
Paleoredox Geochemistry And Bioturbation Levels Of The Exceptionally Preserved Early Cambrian Indian Springs Biota, Poleta Formation, Nevada, Usa, Jonah Meron Novek
Paleoredox Geochemistry And Bioturbation Levels Of The Exceptionally Preserved Early Cambrian Indian Springs Biota, Poleta Formation, Nevada, Usa, Jonah Meron Novek
Theses and Dissertations
The early Cambrian Indian Springs biota, western Nevada, USA exhibits Burgess Shale-type (BST) preservation of a diverse array of animal phyla, including the earliest definitive echinoderms. It therefore provides an important window on animal life during the Cambrian radiation. The objective of this study is to analyze the trace metal paleoredox geochemistry and bioturbation levels of this BST deposit in order to characterize the paleoenvironmental conditions in which these animals lived and their fossils were preserved. A total of 28 rock samples were collected from outcrops at three previously reported intervals of exceptional preservation at the Indian Springs locality, as …
Microbe-Mineral Relationships And Biogenic Mineral Transformations In Actively Venting Deep-Sea Hydrothermal Sulfide Chimneys, Tzihsuan J. Lin
Microbe-Mineral Relationships And Biogenic Mineral Transformations In Actively Venting Deep-Sea Hydrothermal Sulfide Chimneys, Tzihsuan J. Lin
Doctoral Dissertations
This dissertation uses a combination of microbiology, mineralogy, and geochemistry to understand dissimilatory iron reduction in hyperthermophilic archaea and the role and potential impact of these and other vent microorganisms within active deep-sea hydrothermal vent chimneys. The central objective of the dissertation is to determine if mineral composition and chimney type are among the primary determinants of microbial community composition and hyperthermophilic, dissimilatory iron reducer growth, in addition to other environmental factors such as nutrient availability, temperature, pH, and chlorinity. This is done using samples and organisms collected from the Endeavour Segment of the Juan de Fuca Ridge in the …
Karst Estuaries: A Newly Described Ecosystem Governed By Aquifer Hydrology, Damian M. Menning
Karst Estuaries: A Newly Described Ecosystem Governed By Aquifer Hydrology, Damian M. Menning
USF Tampa Graduate Theses and Dissertations
The overall goal of this dissertation is to define the hydrological, geochemical, and biological characteristics of a Karst Estuary. These types of estuaries represent a unique ecosystem created by freshwater inputs from direct flow through karst conduits and/or diffuse flow through a karst matrix. In order to determine the characteristics of a Karst Estuary we monitored short-term tidal fluctuations, long-term rainfall patterns, aquifer levels, spring discharge, multiple geochemical parameters, microbial communities in the water column and sediment, and macrofaunal communities in the sediment along a transect from a submarine spring through the Gulf of Mexico. Four sites were selected along …
Geochemical Analysis Of Eolian Fluxes During The Transition From Greenhouse To Icehouse Conditions In Equatorial Pacific., Daniel Nicholas Miller
Geochemical Analysis Of Eolian Fluxes During The Transition From Greenhouse To Icehouse Conditions In Equatorial Pacific., Daniel Nicholas Miller
Theses and Dissertations
To assess the atmospheric conditions during times of differing pole to equator thermal gradients through the middle Eocene to early Oligocene, 42 to 30 Ma, samples from deep-sea sediment cores U1331, U1332, U1333 from IODP Expedition 320/321 in the eastern equatorial Pacific (EEP) have been chemically leached to isolate the operationally defined eolian dust (ODED; <63 μm fraction). The ODED was analyzed for neodymium (Nd) isotopic compositions and rare earth element (REE) concentrations in order to determine the provenance of the ODED fraction and to elucidate the environmental conditions (e.g. predominant wind patterns) during deposition over the interval of study. The variations in the ODED fraction are expected to be controlled by changes in sources delivered via eolian input. However, negative cerium anomalies in the Post Achaean Australian Shale (PAAS) normalized rare earth element profiles of the ODED show a biasing geochemical seawater phase to the ODED signature. It is found that εNd values and cerium anomalies (Ce/Ce*) of ODED are consistent with fossil fish teeth values that record bottom water signatures from the same location and time period until ~36-37 Ma; around the Priabonian/Bartonian boundary marked by increased thermal gradients due to the emplacement of high elevation glaciers on Antarctica (Scher et. al., 2014). Moreover, the more negative cerium anomalies correlate to more radiogenic εNd values. The geochemical seawater signature in the ODED samples is believed to be caused by a change in sedimentary phase regulated by the spatial paleoposition of the sites relative to the biological high productivity zone and/or the depth of the CCD. Subsequently these regulators on the sedimentary phases of the ODED were investigated for biasing the geochemical signatures of the ODED, assumed to be changes in sources thereby provenance. Together, the Nd and REE results from the study temporally indicate that the ODED fraction may be a mixing between two sources, that of a biasing biogenic and/or authigenic source that records seawater conditions, and that of an older, less radiogenic continental source, inferred as Asian loess, as an increased thermal gradient prevails over the course of the study. Further research needs to be performed to make more robust and conclusive linkages between sources, mixing of sources, and atmospheric eolian delivery patterns, highlighting the necessity for a better understanding of atmospheric conditions during important climatic events throughout the history of the Earth.
Reconstructing Recent Sedimentation In Two Urbanised Coastal Lagoons (Nsw, Australia) Using Radioisotopes And Geochemistry, Brian Jones, H Heijnis, J. Harrison, Suzanne Hollins, S Hankin, Atun Zawadzki
Reconstructing Recent Sedimentation In Two Urbanised Coastal Lagoons (Nsw, Australia) Using Radioisotopes And Geochemistry, Brian Jones, H Heijnis, J. Harrison, Suzanne Hollins, S Hankin, Atun Zawadzki
B. G. Jones
In this study, we combined grain size and geochemical analyses with radioisotope analysis of lead-210 (210Pb), caesium-137 (137Cs) and radiocarbon (14C) ages to reconstruct the sedimentation history of two urbanised coastal lagoons in south-east Australia. Towradgi and Fairy Lagoons were both found to exhibit slow initial sedimentation of less than 1 mm year-1 prior to anthropogenic influences. Land clearing in the catchments increased runoff and erosion in the creeks feeding into the estuaries, and has resulted in progradation of fluvial material into the estuarine systems with a marked increase in sedimentation to between 2 and 7 mm year-1. The upper …
Geochemical Evidence Of Ancient Maya Marketplace Activities In The Puuc Hills Of Mexico And At Caracol, Belize, Jacob M. Horlacher
Geochemical Evidence Of Ancient Maya Marketplace Activities In The Puuc Hills Of Mexico And At Caracol, Belize, Jacob M. Horlacher
Theses and Dissertations
The large public plazas of the ancient Maya were likely swept clear of debris and durable artifacts that could have provided evidence of the ancient anthropogenic activities. However, geochemical residues of food or mineral ores and pigments became affixed to soil and floor particles. These particles chemically bound so that natural movement of water is insufficient to cause them to move, leaving invisible geochemical signatures of ancient activities. This line of study is focused on the relationship between the geospatial distribution of element concentrations and ancient human activities using current laboratory techniques and isopleths, or chemical concentration contour maps, to …
Thin Soils And Sacbes: The Soil Resources Of Uci, Yucatan, Mexico, Zachary S. Larsen
Thin Soils And Sacbes: The Soil Resources Of Uci, Yucatan, Mexico, Zachary S. Larsen
Theses and Dissertations
The objective of this study was to use pedological evidence in conjunction with Geographic Information Systems, and soil physical and chemical analyses as means to better understand the agricultural landscape surrounding the ancient Maya city of Uci. Specifically, the query of this thesis is to determine whether there is an association between settlement density and soil resources, and what relationship if any there is between the ancient sacbe of Uci and its surrounding agricultural potential. Stable carbon isotope analysis of the humin fraction of the soil organic matter was conducted on several profiles from karst depressions known as rejolladas near …
Soil Geochemistry And Pathfinder Element Distribution Associated With The Hillgrove Antimony-Gold-Tungsten Deposit, New England Orogen, Nsw, R Ellsmore, Solomon Buckman, C Simpson
Soil Geochemistry And Pathfinder Element Distribution Associated With The Hillgrove Antimony-Gold-Tungsten Deposit, New England Orogen, Nsw, R Ellsmore, Solomon Buckman, C Simpson
Solomon Buckman Dr.
No abstract provided.
Geochemical Analysis Of Ancient Activities At Two Plazas In Cobá, Mexico, Eric G. Coronel
Geochemical Analysis Of Ancient Activities At Two Plazas In Cobá, Mexico, Eric G. Coronel
Theses and Dissertations
Two plazas at Cobá, Mexico, may have been the place of market activity during the classic Maya period. The intense decomposition in the warm, moist soils of the Yucatan Peninsula precludes the identification of organic artifacts in archaeological contexts, but phosphorus and trace elements accumulation in soils may provide evidence of marketing activities. The spatial patterns of P and trace element concentrations were used to elucidate the types of ancient Maya activities that took place in those plazas. Phosphorus concentrations are highly correlated (p-value <0.01) with Fe, Mn, and Zn levels in both Plaza B and D. Although the soil geochemistry of Plaza B does not show a marketplace pattern in comparison with previous studies, the elemental concentrations and distributions within Plaza D join other lines of evidence to support the premise that marketplace activities took place at that location. Soil samples were analyzed using DTPA extraction, Mehlich II, Olsen, and Portable X-Ray Fluorescence (PXRF). Experiments were performed to study the suitability of PXRF for field studies. Aspects that were studied include granule size, soil moisture content, protective plastic films that could interfere with the X-Ray signal when placing the samples on top of the analyzer, and a comparison of certified soil standards to the PXRF elemental concentration readings. The results suggest that a field laboratory could be set up to air-dry and sieve soil samples to a minimum mesh size of #10 (> 2 mm).
The Biogeochemistry Of Submerged Coastal Karst Features In West Central Florida, Keith Michael Garman
The Biogeochemistry Of Submerged Coastal Karst Features In West Central Florida, Keith Michael Garman
USF Tampa Graduate Theses and Dissertations
West Central Florida is a complex karst environment with numerous sinkholes, springs, and submerged cave systems. Many of these karst features are anchialine, located within the subterranean estuary where freshwater and saltwater mix. Water quality data and/or fauna data were obtained from twenty-one karst features and their associated cave systems. The anchialine karst environment of the study area has a wide range of habitats with measured salinities ranging from freshwater at <0.2 ppt to sulfidic, hypersaline water at 38.5 ppt and measured pH readings ranging from 6.39 in water impacted by sulfur oxidizing bacteria to 10.3 in an isolated room of a cave. Stygobitic crustaceans were identified in conduits extending beneath the Gulf of Mexico supporting the hypotheses that freshwater crustaceans could survive higher sea levels in freshwater conduits beneath saltwater. The fauna associated with the anchialine cave systems included Sabellidae and Polychaeta worms, hydroids, cnidarians and hydrobiid snails. Jewfish Sink, like other anaerobic marine basins that were submarine springs, has four zones: oxic zone, transition zone, upper anoxic zone and anoxic bottom water. The upper zones have seasonal water quality variations from winter cooling and sinking of surface water and changes in the microbial communities. Activity of sulfate reducing bacteria is carbon limited in the anoxic zones, where sulfate reduction is the major metabolic process, and primary production is phosphate limited in the oxic zones. Organic input from the Gulf of Mexico drives the bacterial anaerobic ecosystem, resulting in a “sulfide pump”, in which sulfide percolates upward removing oxygen from the overlying sediment.
Soil Geochemistry And Pathfinder Element Distribution Associated With The Hillgrove Antimony-Gold-Tungsten Deposit, New England Orogen, Nsw, R Ellsmore, Solomon Buckman, C Simpson
Soil Geochemistry And Pathfinder Element Distribution Associated With The Hillgrove Antimony-Gold-Tungsten Deposit, New England Orogen, Nsw, R Ellsmore, Solomon Buckman, C Simpson
Faculty of Science - Papers (Archive)
No abstract provided.
Middle Miocene Ice Sheet Dynamics, Deep‐Sea Temperatures, And Carbon Cycling: A Southern Ocean Perspective, Amelia E. Shevenell, James P. Kennett, David W. Lea
Middle Miocene Ice Sheet Dynamics, Deep‐Sea Temperatures, And Carbon Cycling: A Southern Ocean Perspective, Amelia E. Shevenell, James P. Kennett, David W. Lea
Marine Science Faculty Publications
Relative contributions of ice volume and temperature change to the global ∼1‰ δ18O increase at ∼14 Ma are required for understanding feedbacks involved in this major Cenozoic climate transition. A 3‐ma benthic foraminifer Mg/Ca record of Southern Ocean temperatures across the middle Miocene climate transition reveals ∼2 ± 2°C cooling (14.2–13.8 Ma), indicating that ∼70% of the increase relates to ice growth. Seawater δ18O, calculated from Mg/Ca and δ18O, suggests that at ∼15 Ma Antarctica's cryosphere entered an interval of apparent eccentricity‐paced expansion. Glaciations increased in intensity, revealing a central role for internal climate …
~3,850 Ma Tonalites In The Nuuk Region, Greenland: Geochemistry And Their Reworking Within An Eoarchaean Gneiss Complex, Allen P. Nutman, Vickie C. Bennett, Clark R. L Friend, Kenji Horie, Hiroshi Hidaka
~3,850 Ma Tonalites In The Nuuk Region, Greenland: Geochemistry And Their Reworking Within An Eoarchaean Gneiss Complex, Allen P. Nutman, Vickie C. Bennett, Clark R. L Friend, Kenji Horie, Hiroshi Hidaka
Faculty of Science - Papers (Archive)
The Eoarchaean (>3,600 Ma) Itsaq Gneiss Complex of southern West Greenland is dominated by polyphase orthogneisses with a complex Archaean tectonothermal history. Some of the orthogneisses have c. 3,850 Ma zircons, and they vary from rare single phase metatonalites to more common complexly banded migmatites. This is due to heterogeneous strain, in situ anatexis and granitic veining superimposed during younger tectonothermal events. In the single-phase tonalites with c. 3,850 Ma zircon, oscillatory-zoned prismatic zircon is all 3,850 Ma old, but shows patchy ancient loss of radiogenic Pb. SHRIMP spot analyses and laser ablation ICP-MS depth profiling show that thin …
Reproducibility Of Geochemical And Climatic Signals In The Atlantic Coral Montastraea Faveolata, Jennifer M. Smith, Terrence M. Quinn, Kevin P. Helmle, Robert B. Halley
Reproducibility Of Geochemical And Climatic Signals In The Atlantic Coral Montastraea Faveolata, Jennifer M. Smith, Terrence M. Quinn, Kevin P. Helmle, Robert B. Halley
Marine Science Faculty Publications
Monthly resolved, 41‐year‐long stable isotopic and elemental ratio time series were generated from two separate heads of Montastraea faveolata from Looe Key, Florida, to assess the fidelity of using geochemical variations in Montastraea, the dominant reef‐building coral of the Atlantic, to reconstruct sea surface environmental conditions at this site. The stable isotope time series of the two corals replicate well; mean values of δ18O and δ13C are indistinguishable between cores (compare 0.70‰ versus 0.68‰ for δ13C and −3.90‰ versus −3.94‰ for δ18O). Mean values from the Sr/Ca time series differ by …
Application Of Paleoclimatology To Coral Reef Monitoring And Management, C. Mark Eakin, Peter K. Swart, Terrence M. Quinn, Kevin P. Helmle, Jennifer M. Smith, Richard E. Dodge
Application Of Paleoclimatology To Coral Reef Monitoring And Management, C. Mark Eakin, Peter K. Swart, Terrence M. Quinn, Kevin P. Helmle, Jennifer M. Smith, Richard E. Dodge
Marine & Environmental Sciences Faculty Proceedings, Presentations, Speeches, Lectures
The skeletons of reef-building corals are valuable archives of climatic and environmental information. Paleoclimatic data chiefly have been generated in areas most sensitive to global or regional climatic variability. However, these records also provide valuable information on anthropogenic influences – guidance of value to resource managers. NOAA’s Coral Reef Watch targets observations of current and past coral reef health in or near marine protected areas through satellites, in situ sensor platforms, and paleoclimatic analyses. Paleoclimatic data provide retrospective monitoring through multi-century environmental reconstructions that improve our understanding of past stress to coral reefs. Two sites in the Florida Keys National …
A Fossil Coral Perspective On Western Tropical Pacific Climate Similar To 350 Ka, K. H. Kilbourne, Terrence M. Quinn, F. W. Taylor
A Fossil Coral Perspective On Western Tropical Pacific Climate Similar To 350 Ka, K. H. Kilbourne, Terrence M. Quinn, F. W. Taylor
Marine Science Faculty Publications
The nature of tropical climate variability ∼350 ka is addressed using δ18O and Sr/Ca records from a modern and a fossil coral from Vanuatu (southwestern tropical Pacific Ocean). Modern El Niño events at Vanuatu produce positive coral δ18O and Sr/Ca anomalies; similar anomalies observed in the fossil coral records suggest that El Niño was operative 350 kyr ago. Seasonal variations in coral Sr/Ca, a sea surface temperature (SST) proxy, have the same amplitude in both corals, whereas seasonal δ18O variations are smaller in the fossil coral than in the modern coral. This is consistent …
Diagenesis And Geochemistry Of Porites Corals From Papua New Guinea: Implications For Paleoclimate Reconstruction, Helen V. Mcgregor, M Gagan
Diagenesis And Geochemistry Of Porites Corals From Papua New Guinea: Implications For Paleoclimate Reconstruction, Helen V. Mcgregor, M Gagan
Faculty of Science - Papers (Archive)
No abstract provided.
High Precision, High Spatial Resolution Analysis Of Sulfur Isotopes By Laser Combustion Of Natural Sulfide Minerals, S. P. Kelley, A. E. Fallick, P. Mcconville, A. J. Boyce
High Precision, High Spatial Resolution Analysis Of Sulfur Isotopes By Laser Combustion Of Natural Sulfide Minerals, S. P. Kelley, A. E. Fallick, P. Mcconville, A. J. Boyce
Scanning Microscopy
Laser induced combustion provides a powerful new technique for sulfur isotope measurements in natural sulfides. A high power continuous laser, focused through a modified microscope system onto a sulfide mineral target, produces highly localized heating. The laser beam is focused to a spot 25 μm in diameter at the sample surface. In the presence of low pressure oxygen, temperatures at the centre of the spot are sufficiently high to produce localized oxidation. Resultant SO2 is transferred to a gas source isotope ratio mass spectrometer, where the 𝛿34S can be measured to a precision better than 0.25‰. Sulfur …