NSF Org:	EAR Division Of Earth Sciences
Recipient:	CINCINNATI UNIV OF
Initial Amendment Date:	July 3, 2017
Latest Amendment Date:	July 3, 2017
Award Number:	1733977
Award Instrument:	Standard Grant
Program Manager:	Dena Smith-Nufio dmsmith@nsf.gov  (703)292-7431 EAR  Division Of Earth Sciences GEO  Directorate for Geosciences
Start Date:	September 1, 2017
End Date:	August 31, 2020 (Estimated)
Total Intended Award Amount:	$130,812.00
Total Awarded Amount to Date:	$130,812.00
Funds Obligated to Date:	FY 2017 = $130,812.00
History of Investigator:	Thomas Algeo (Principal Investigator) Thomas.Algeo@uc.edu
Recipient Sponsored Research Office:	University of Cincinnati Main Campus 2600 CLIFTON AVE CINCINNATI OH  US  45220-2872 (513)556-4358
Sponsor Congressional District:	01
Primary Place of Performance:	University of Cincinnati Main Campus OH  US  45221-0013
Primary Place of Performance Congressional District:	01
Unique Entity Identifier (UEI):	DZ4YCZ3QSPR5
Parent UEI:	DZ4YCZ3QSPR5
NSF Program(s):	Sedimentary Geo & Paleobiology
Primary Program Source:	01001718DB NSF RESEARCH & RELATED ACTIVIT
Program Reference Code(s):
Program Element Code(s):	745900
Award Agency Code:	4900
Fund Agency Code:	4900
Assistance Listing Number(s):	47.050

ABSTRACT

The goal of the funded proposal is to determine the relative amounts of oxygen dissolved in ancient oceans during a unique geologic time interval (300 to 420 million years ago) when three major mass extinctions occurred and the Earth was significantly warmer than today. Understanding the history of oxygen levels in ancient oceans is important because oxygen concentrations influence all marine animal life, control the formation and preservation of petroleum and many economic mineral deposits, and affect important biochemical reactions in the oceans and atmosphere. This project utilizes the relatively new geochemical tool of uranium isotopes to develop the most detailed history of changing ocean oxygen concentrations to date. The funding supports the training of the next generation of Earth scientists, will provide hands-on field and laboratory experience for first-generation college students, and will support multiple primary school science teachers to conduct real-world science to gain confidence and provide new ideas for their own classrooms.

The project goal is to develop a global-ocean redox curve using U isotopes from Devonian-Mississippian marine carbonates. The ~100 million year study interval, which bridges the transition between poorly oxygenated Precambrian-Early Paleozoic oceans and well-oxygenated Late Paleozoic-Recent oceans, is important because of: 1) a doubling of atmospheric pO2 levels, 2) a transition from greenhouse to icehouse climate and intensifying ocean circulation, 3) the occurrence of three mass extinctions, two of which are attributed to marine anoxia, and 4) multiple large positive 13C excursions. The U-isotope composition of marine carbonates has the potential to record mean global-ocean redox conditions owing to the long residence time (~500 thousand years) of U in seawater. Samples will be collected from biostratigraphically well-dated successions in Nevada and Utah at spacings ranging from ~100 thousand years/sample to <20 thousand years/sample through specific event intervals. To assess samples for local redox influences, we will analyze redox-sensitive metals, Fe-speciation, and Corg:P ratios. To verify the global nature of the composite curve, we will sample and compare to selected shorter stratigraphic intervals on other continents.

PROJECT OUTCOMES REPORT

Disclaimer

This Project Outcomes Report for the General Public is displayed verbatim as submitted by the Principal Investigator (PI) for this award. Any opinions, findings, and conclusions or recommendations expressed in this Report are those of the PI and do not necessarily reflect the views of the National Science Foundation; NSF has not approved or endorsed its content.

The major goal of this project was to use U isotopes in well-preserved marine limestones to develop a high-resolution record of variation in redox (reducing-oxidizing) conditions in the global ocean during the middle Paleozoic (ca. 420 to 350 million years ago), a key interval in the oxygenation history of the Earth-surface environment. This profile was compared with contemporaneous records of atmospheric O2 and potential tectonic, climatic, and paleobotanic controls on oceanic oxygenation. The geochemical dataset generated for this project demonstrated substantial variability in global-ocean redox conditions through the study interval. Specifically, the data revealed a major increase in oceanic anoxia during the Pragian-Emsian stages of the Early Devonian that can be linked to a coeval expansion of early land plants. This finding is of considerable significance in understanding biogeochemical cycling during the Middle Paleozoic, providing support to the hypothesis that terrestrial floral expansion was a key driver of atmospheric CO2 decline prior to the Late Paleozoic Ice Age, thus setting the stage for that major climate event, as well as of increased land-to-marine nutrient fluxes, triggering the Late Devonian mass extinctions among marine invertebrate faunas. These findings should inform relevant sections of Earth history courses being taught at institutions of higher education globally. The project also led to training of four undergraduates at the University of Cincinnati in laboratory techniques and scientific research methods as well as mentoring of one post-doctoral student who has since progressed to a faculty position at a research level-one university in the United States.

Last Modified: 10/30/2020
Modified by: Thomas J Algeo

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