| NSF Org: |
EAR Division Of Earth Sciences |
| Recipient: |
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| Initial Amendment Date: | July 12, 2013 |
| Latest Amendment Date: | September 2, 2015 |
| Award Number: | 1324954 |
| Award Instrument: | Continuing Grant |
| Program Manager: |
Dena Smith-Nufio
dmsmith@nsf.gov (703)292-7431 EAR Division Of Earth Sciences GEO Directorate for Geosciences |
| Start Date: | August 15, 2013 |
| End Date: | January 31, 2018 (Estimated) |
| Total Intended Award Amount: | $125,736.00 |
| Total Awarded Amount to Date: | $125,736.00 |
| Funds Obligated to Date: |
FY 2014 = $68,706.00 FY 2015 = $24,963.00 |
| History of Investigator: |
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| Recipient Sponsored Research Office: |
202 HIMES HALL BATON ROUGE LA US 70803-0001 (225)578-2760 |
| Sponsor Congressional District: |
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| Primary Place of Performance: |
E301 Howe-Russell Baton Rouge LA US 70803-2701 |
| Primary Place of
Performance Congressional District: |
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| Unique Entity Identifier (UEI): |
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| Parent UEI: |
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| NSF Program(s): | Sedimentary Geo & Paleobiology |
| Primary Program Source: |
01001415DB NSF RESEARCH & RELATED ACTIVIT 01001516DB NSF RESEARCH & RELATED ACTIVIT |
| Program Reference Code(s): |
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| Program Element Code(s): |
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| Award Agency Code: | 4900 |
| Fund Agency Code: | 4900 |
| Assistance Listing Number(s): | 47.050 |
ABSTRACT
Collaborative Research: Testing the Early Late Ordovician Cool Water Hypothesis
by
Achim Herrmann, Louisiana State University
Kenneth MacLeod, University of Missouri
Stephen Leslie, James Madison University
EAR-1324954, -1323444, -1324577
ABSTRACT
The Late Ordovician glaciation (LOG) is associated with the second largest mass extinction event of the Phanerozoic. It marks the end of the global warm conditions of the early Paleozoic that lasted ~150my and occurred under elevated pCO2 conditions. Considerable doubt has recently been raised with regard to the duration of the LOG, its potential driving mechanisms, and pre-glacial, long-term temperature variations. For instance approximately 15 Ma prior to LOG the North American continental plate was situated in tropical to subtropical latitudes, but sedimentological and paleontological evidence suggest a shift from deposition of warm water carbonates to deposition of cool water carbonates. It is not clear whether this sedimentological change reflects global cooling (indicating significant perturbation to the global climate system well before the Late Ordovician glaciation) or physical responses to tectonic activity with no requisite climatic implications.
The projects will test competing hypotheses that try to explain this event through an extensive geochemical study. In particular, PIs will use the geochemical archive of conodont apatite (delta18O and epsilonNd) and carbonates (DELTA48, delta18O, and delta13C) to address questions about paleoceanographic conditions during the Early Late Ordovician. They expect that this research will lead 1) to clarification of potential causes for the paleontological/sedimentological changes during this interval, 2) to a better understanding of epicontinental sea circulation and an improved facies model for epicontinental low latitude carbonate platforms (for which no modern-day analogues exist), and 3) to better documentation of the temperature history of the Ordovician greenhouse interval.
This research project will have active participation by undergraduate students, graduate students, and a secondary school science teacher. Therefore, the project will not only impact present university students and researchers, it will also impact future generations of students through enhancing an earth science secondary educations teacher¡¦s knowledge base and science curriculum. Data will be contributed to publicly accessible databases making them available for further research and general education in the fields of paleoclimate and paleoceanography.
PUBLICATIONS PRODUCED AS A RESULT OF THIS RESEARCH
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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.
Study of ancient marine systems is needed to understand environmental controls on the stratigraphic record. This project examined environmental changes across a proposed cooling interval prior to the Late Ordovician glaciation. To this end, we studied the geochemical, paleontological, and sedimentological record of multiple area to investigate these changes in space and time. In order to precisely correlate the different areas, we also developed a high-resolution correlation framework based on volcanic ash beds.
Oxygen isotopes, a proxy for sea surface temperature, do not shift during the transition from “warm-water” to “cool-water” carbonate deposition. This would suggest that an environmental factor other than cooling was the cause for this shift in lithology. Similarly, a prominent positive carbon isotope excursion proposed to be the signature of organic carbon burial, which would have resulted in lower pCO2 and lower average global temperatures, was actually associated with slight warming. Shifts in neodymium isotopes, which are a weathering proxy and water mass tracer, correlate with this warming trend and suggest that this warming event triggered increased weathering rates during this time period.
In sum, we found that conodont oxygen and neodymium isotopes suggest stable or slightly warming conditions in the 10 million years before the Late Ordovician glaciation and mass extinction. Thus our findings explicitly contradict models invoking long term gradual cooling during the Late Ordovician and implicitly suggest that the end Ordovician glaciation and extinction were geologically quite rapid and catastrophic events.
The broader impacts of this project emphasized education and training of students. At LSU, seven graduate students and six undergraduate students became members of the research team. This included several students from underrepresented groups. The students engaged in sample collection, laboratory work, and data analysis, exposing them to the process of interdisciplinary scientific research. Many of these students developed a Master's thesis or senior thesis from their work on this project, and most presented their results at regional or national geoscience meetings. Several peer-reviewed journal papers have been publised with students as the lead author. The data output of the study will be made available to both the Earth-sciences community and the public through publically accessible databases.
Last Modified: 08/23/2018
Modified by: Achim D Herrmann
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