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Reconstructing Biological and Chemical Changes in the Tropical Pacific using Bio-Barium and Pelagic Barite.

Record Type:	Electronic resources : Monograph/item
Title/Author:	Reconstructing Biological and Chemical Changes in the Tropical Pacific using Bio-Barium and Pelagic Barite./
Author:	Kim, Ji-Eun.
Description:	1 online resource (166 pages)
Notes:	Source: Dissertations Abstracts International, Volume: 84-04, Section: B.
Contained By:	Dissertations Abstracts International84-04B.
Subject:	Geochemistry. -
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=29712251click for full text (PQDT)
ISBN:	9798845451545

Reconstructing Biological and Chemical Changes in the Tropical Pacific using Bio-Barium and Pelagic Barite.
Kim, Ji-Eun.

Reconstructing Biological and Chemical Changes in the Tropical Pacific using Bio-Barium and Pelagic Barite. - 1 online resource (166 pages)

Source: Dissertations Abstracts International, Volume: 84-04, Section: B.

Thesis (Ph.D.)--The Ohio State University, 2022.

Includes bibliographical references

The study of past geologic records and present-day oceanographic processes can benefit society by better understanding how climate and biogeochemical processes interact in ocean. I present research that helps better understand these interactions by studying marine sediments, specifically barium in aqueous settings. This dissertation is separated into three projects that utilize geochemical interpretation of sediments and fluxes from the ocean to understand biogeochemical changes in past and present oceans.The first two projects study the export of carbon from ocean surface to deep waters in the tropical Pacific. The Maastrichtian records confirm that organic carbon export proxies related to barite (BaSO4) can be reconstructed at high-resolution using non-destructive X-ray fluorescence (XRF) Ba. This scanning XRF Ba record from 71.5 to 66 million years ago (Ma), after 405 kyr tuning, shows direct precessional cycle influence on organic carbon export during the cool greenhouse conditions of Late Cretaceous in the tropical Pacific. This suggests high frequency climate variability existed in the tropical Pacific and precession had a role in driving these changes, which were enhanced after Deccan volcanism when CO2 concentrations increased. A modern sediment trap record of carbon export determined by analyzing excess-Ba content (proxy for barite) from 2003 to 2013 records changed across a shift in the phase of the Pacific Decadal Oscillation (PDO). This record suggests upwelling is the main driving force for carbon export in the Eastern Tropical Pacific (ETP) by the carbon export showing variations following the PDO phases as similar to the upwelling magnitude changes, rather than the surface dust input. The dust deposition at the surface decoupled from dust export at depth leads to the conclusion that dust has limited role as a micronutrient source. Together these records suggest that hydrological changes in the tropical Pacific are important drivers of change for organic carbon export in both the Late Cretaceous and modern oceans.The last project presents selenium (Se) and arsenic (As) speciation within natural barite samples which reflect the aqueous environment oxidation state (i.e., oxic, suboxic, and anoxic). Natural barite sample (n=12) Se(VI)/Se(IV) and As(V)/As(III) results were obtained through X-ray absorption near edge structure (XANES) spectroscopy from marine pelagic, marine diagenetic, continental, hydrothermal, and cold seep barite. The results suggest that Se and As speciation reflect the redox condition of the environment in which barite precipitates, and further potentially provide information about biological sulfate reduction.

Electronic reproduction.
Ann Arbor, Mich. :
ProQuest,
2023

Mode of access: World Wide Web

ISBN: 9798845451545Subjects--Topical Terms:

539092
Geochemistry.
Subjects--Index Terms:

PaleoclimateIndex Terms--Genre/Form:

542853
Electronic books.

Reconstructing Biological and Chemical Changes in the Tropical Pacific using Bio-Barium and Pelagic Barite.
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504 $a Includes bibliographical references
520 $a The study of past geologic records and present-day oceanographic processes can benefit society by better understanding how climate and biogeochemical processes interact in ocean. I present research that helps better understand these interactions by studying marine sediments, specifically barium in aqueous settings. This dissertation is separated into three projects that utilize geochemical interpretation of sediments and fluxes from the ocean to understand biogeochemical changes in past and present oceans.The first two projects study the export of carbon from ocean surface to deep waters in the tropical Pacific. The Maastrichtian records confirm that organic carbon export proxies related to barite (BaSO4) can be reconstructed at high-resolution using non-destructive X-ray fluorescence (XRF) Ba. This scanning XRF Ba record from 71.5 to 66 million years ago (Ma), after 405 kyr tuning, shows direct precessional cycle influence on organic carbon export during the cool greenhouse conditions of Late Cretaceous in the tropical Pacific. This suggests high frequency climate variability existed in the tropical Pacific and precession had a role in driving these changes, which were enhanced after Deccan volcanism when CO2 concentrations increased. A modern sediment trap record of carbon export determined by analyzing excess-Ba content (proxy for barite) from 2003 to 2013 records changed across a shift in the phase of the Pacific Decadal Oscillation (PDO). This record suggests upwelling is the main driving force for carbon export in the Eastern Tropical Pacific (ETP) by the carbon export showing variations following the PDO phases as similar to the upwelling magnitude changes, rather than the surface dust input. The dust deposition at the surface decoupled from dust export at depth leads to the conclusion that dust has limited role as a micronutrient source. Together these records suggest that hydrological changes in the tropical Pacific are important drivers of change for organic carbon export in both the Late Cretaceous and modern oceans.The last project presents selenium (Se) and arsenic (As) speciation within natural barite samples which reflect the aqueous environment oxidation state (i.e., oxic, suboxic, and anoxic). Natural barite sample (n=12) Se(VI)/Se(IV) and As(V)/As(III) results were obtained through X-ray absorption near edge structure (XANES) spectroscopy from marine pelagic, marine diagenetic, continental, hydrothermal, and cold seep barite. The results suggest that Se and As speciation reflect the redox condition of the environment in which barite precipitates, and further potentially provide information about biological sulfate reduction.
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538 $a Mode of access: World Wide Web
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650 4 $a Geology. $3 516570
650 4 $a Paleoclimate science. $3 3173835
650 4 $a Marine geology. $3 3173821
650 4 $a Biogeochemistry. $3 545717
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653 $a Carbon cycle
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