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Full-Text Articles in Physical Sciences and Mathematics
Experimental Insights Into The Origin Of Microcrystalline Calcites, Mohammed Hashim
Experimental Insights Into The Origin Of Microcrystalline Calcites, Mohammed Hashim
Dissertations
A significant proportion of modern marine calcium carbonate sediments is dominated by metastable aragonite and high Mg calcite that either dissolves or stabilizes to low-Mg-calcite (calcite) or dolomite during diagenesis. Sediment dissolution and stabilization have implications for the CaCO3 budget in the ocean and carbon burial rates. Yet, the diagenetic conditions that promote each process and their relative importance are poorly understood. Further, stabilization most commonly produces calcite microcrystals that exhibit various textures and host micropores. Despite their ubiquity in the rock record, the controls on microcrystal textures remain unclear. Here, laboratory experiments were used to investigate aragonite-to-calcite stabilization as …
Past Ice-Ocean Interactions On The Sabrina Coast Shelf, East Antarctica: Deglacial To Recent Paleoenvironmental Insights From Marine Sediments, Kara J. Vadman
Past Ice-Ocean Interactions On The Sabrina Coast Shelf, East Antarctica: Deglacial To Recent Paleoenvironmental Insights From Marine Sediments, Kara J. Vadman
USF Tampa Graduate Theses and Dissertations
The East Antarctic Ice Sheet (EAIS) contains ~53 meters of sea level equivalent (SLE) ice, and observations suggest it is sensitive to ongoing and past climate change. The EAIS has traditionally been considered insensitive to climate perturbations because it is largely grounded above sea level. However, aerogeophysical surveys, oceanographic observations, and models indicate that large areas of the EAIS are grounded below sea level and contain 19.2 m SLE. Marine-based parts of the EAIS are thought to be located on inland-sloping beds that drain through marine terminating outlet glaciers, indicating large areas of the EAIS may be more sensitive to …
Reconstructing Surface Water Carbonate Ion Concentration Changes In The Eastern Equatorial Pacific Across Glacial Transitions, Lenzie Gail Ward
Reconstructing Surface Water Carbonate Ion Concentration Changes In The Eastern Equatorial Pacific Across Glacial Transitions, Lenzie Gail Ward
OES Theses and Dissertations
Today, the eastern equatorial Pacific (EEP) plays a critical role in the global CO2 budget as a major source of CO2 to the atmosphere, but recent studies suggest the region may shift to a sink for atmospheric CO2 under different climate states. Here, I focus on two transitional periods, the last deglaciation (25 kyr to present) and last glaciation (the Marine Isotope Stage (MIS) 5a-4 transition, 96 to 60 kyr), to investigate how the carbon system in the EEP responds to major climate changes. I measured B/Ca ratios in the planktic foraminifera Globigerina bulloides from core MV1014-17JC …
Diatoms And Their Response To Tectonic Gateway Changes: Case Studies From Southern Hemisphere Sites, Jason James Coenen
Diatoms And Their Response To Tectonic Gateway Changes: Case Studies From Southern Hemisphere Sites, Jason James Coenen
Graduate Research Theses & Dissertations
This dissertation covers three major transitions in Earth's climate system throughout theCenozoic (the past 65 million years of Earth's history). The progressive breakup of the super continent Pangea and the ultimate change in ocean circulation (and redistribution of heat) as a result of tectonic events dating back to the Mesozoic, primed Earth's climate system for cooling and ultimately bipolar glaciation. Climate transitions in three distinct environments were studied using absolute diatom abundance, diatom assemblages, and geochemical tracers of diatoms (i.e., biogenic silica weight%). Two geographic regions are the focus of this dissertation work. Region one is the Ross Embayment of …
Neogene Dinoflagellate Cysts From The Tropical Americas, Damian Cardenas
Neogene Dinoflagellate Cysts From The Tropical Americas, Damian Cardenas
Doctoral Dissertations
"Marine palynomorphs, mainly dinoflagellate cysts and acritarchs, constitute excellent proxies for biostratigraphic and paleoceanographic studies in neritic sequences. Neogene marine palynological studies have mostly focused on the Northern Hemisphere, resulting in the scarcity of dinoflagellate cysts and acritarchs from tropical latitudes. Forty samples encompassing the late Chattian-late Burgidalian time interval (~24.1- 17.3 Ma) in the Southern Caribbean were analyzed for their marine palynological contents. A biostratigraphic scheme for the region is proposed and includes the upper Chattian-lower Aquitanian Minisphaeridium latirictum Interval Zone (~23.9-22.0 Ma), the upper Aquitanian Achomosphaera alcicornu Interval Zone (~22.0-20.3 Ma), and the Burdigalian Cribroperidinium tenuitabulatum Interval Zone …
Constraining Respired Carbon Storage In The Eastern Tropical Pacific Over The Last 25 Thousand Years Using Benthic Foraminiferal Boron/Calcium Ratios, Brian James Close
Constraining Respired Carbon Storage In The Eastern Tropical Pacific Over The Last 25 Thousand Years Using Benthic Foraminiferal Boron/Calcium Ratios, Brian James Close
OES Theses and Dissertations
The storage of inorganic carbon in the deep Pacific Ocean is thought to play an important role in regulating both glacial-interglacial and millennial-scale atmospheric CO2 concentrations (Broecker and Barker 2007; Sigman et al., 2010). A recent study by Loveley et al. (2017) showed that sedimentary authigenic uranium (aU) concentrations, a proxy for suboxic bottom-water conditions, increased significantly in the Eastern Equatorial Pacific (EEP) during the Last Glacial Maximum (LGM, 18 kyr – 23 kyr). If this is correct, the low-oxygen, CO2-rich waters would also have a lower pH and a lower carbonate ion concentration ([CO32- …
Distribution And Variability In Sulfur Isotopes Within Paleoproterozoic Metasedimentary Strata Of The Michigamme Formation, Upper Peninsula, Michigan, Beau J. Haag
Masters Theses
In the Upper Peninsula of Michigan, the Paleoproterozoic Michigamme Formation is composed of a thick package of metasedimentary rocks derived from foreland basin sediments which were deposited during the 1.8Ga Penokean Orogeny. These rocks contain significant, but variable amounts of texturally distinct sulfide minerals such as pyrrhotite and pyrite. We report a systematic relationship between δ34S values from sulfide mineral occurrences, and their stratigraphic locations regardless of texture and mineral composition. We suggest the sulfide minerals within the Michigamme Formation have inherited δ34S values from early sedimentarydiagenetic sulfides, therefore preserving primary isotopic signatures. The observed stratigraphic …
Multi-Proxy Characterization Of Acex Subunit 1/5 (The “Zebra” Interval) To Better Understand Sediment Deposition At This Critical Age Boundary And Paleoceanographic Transition, Victoria Hojnacki
Senior Honors Projects, 2010-2019
Sediment cores recovered from the Lomonosov Ridge on IODP Expedition 302, the Arctic Coring Expedition (ACEX), provided the first major insights into long-term Cenozoic history of climate and ocean conditions in the central Arctic. However, the ACEX record is hampered by a major hiatus or severely condensed interval (depending on age-model interpretations) at 198.7 mcd separating the middle Eocene and Miocene records. Lithologic subunit 1/5 lies above this depth horizon, and is informally called the “zebra interval” because of distinctive stripes - black and gray tilted and cross-banded silty-clay layers, up to 3 cm thick that characterize the lower ~2.5 …
Using Foraminifera In Stemseas Site 1 To Understand The Recent Paleoceanographic And Paleoclimatic History Of Tanner Basin, California Borderland, Michael Stanley Stone
Using Foraminifera In Stemseas Site 1 To Understand The Recent Paleoceanographic And Paleoclimatic History Of Tanner Basin, California Borderland, Michael Stanley Stone
Senior Honors Projects, 2010-2019
In May of 2016, the STEMSEAS Educational Transit cruise OC1605-tranA collected the STEMSEAS Site 1 core from the Tanner Basin in the California Borderland. This research serves as the first formal survey of the foraminifera preserved within that core. The purpose of this research is to use foraminifera preserved within that core to understand the recent depositional and paleoenvironmental conditions at Site 1, and to place that information into a regional paleoceanographic and paleoclimatic context. In pursuing this purpose, this research aims to answer three questions: 1) Can biostratigraphic markers in the foraminiferal assemblages in STEMSEAS Site 1 core be …
Ocean Forcing Of Quaternary East Antarctic Ice Sheet Evolution: An Ice-Proximal Sedimentary Perspective, Michelle E. Guitard
Ocean Forcing Of Quaternary East Antarctic Ice Sheet Evolution: An Ice-Proximal Sedimentary Perspective, Michelle E. Guitard
USF Tampa Graduate Theses and Dissertations
Antarctica and the Southern Ocean play a critical role in Earth’s climate system. Antarctica’s ice sheets contain enough ice to raise global sea level by ~58 m, and the Southern Ocean distributes climate signals and nutrients to the major ocean basins and the deep ocean. Antarctica’s largest ice sheet, the East Antarctic Ice Sheet (EAIS), was considered stable compared to those in West Antarctica and the Antarctic Peninsula because it was thought to be grounded above sea level. However, subglacial topography now reveals vast submarine basins and measurements of ice velocity in the Pacific sector indicate marine-terminating outlet glacier thinning …
Paleoceanography And Paleoenvironmental Changes Of The Cenomanian-Turonian Boundary Interval (94-93 Ma): The Record Of Oceanic Anoxic Event 2 In The Central And Eastern Parts Of The Western Interior Sea, Khalifa Elderbak
Doctoral Dissertations
The Cenomanian/Turonian (C/T) boundary marine strata of the Late Cretaceous Western Interior Sea (WIS) exhibit a positive carbon isotopic excursion in the bulk-carbonate and organic carbon. This marks Oceanic Anoxic Event 2 (OAE 2), which spans the uppermost part of the Hartland Shale and one-third of the overlying Bridge Creek Limestone members of the Greenhorn Formation and their equivalents. The interval is characterized by alternating beds of light-colored limestone and dark-colored marlstone and calcareous shale. These lithologic couplets have been related to Milankovitch orbital cyclicity. Foraminiferal assemblages from three selected sites, including the C/T boundary Global Boundary Stratotype Section and …
Timing Of Svalbard/Barents Sea Ice Sheet Decay During The Last Glacial Termination, Tasha Snow
Timing Of Svalbard/Barents Sea Ice Sheet Decay During The Last Glacial Termination, Tasha Snow
USF Tampa Graduate Theses and Dissertations
The Arctic and North Atlantic underwent significant climactic changes since the Last Glacial Maximum (25,000 years before present (1950 AD); ka BP), but offsets in the timing of events between the two regions are poorly constrained due to age model uncertainties that arise from changing radiocarbon reservoir ages. Here, we use a relatively high-resolution, multi-proxy stable isotope and sedimentologic dataset from Eastern Fram Strait (ODP Leg 162 Site 986) marine sediments to constrain the timing of Svalbard/Barents Sea Ice Sheet decay and infer deglacial reservoir ages over the last 30 ka. We use magnetic susceptibility, inorganic and organic carbon, foraminiferal …