| NSF Org: |
OCE Division Of Ocean Sciences |
| Recipient: |
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| Initial Amendment Date: | February 2, 2016 |
| Latest Amendment Date: | July 16, 2021 |
| Award Number: | 1458444 |
| Award Instrument: | Standard Grant |
| Program Manager: |
Gail Christeson
gchriste@nsf.gov (703)292-2952 OCE Division Of Ocean Sciences GEO Directorate for Geosciences |
| Start Date: | September 1, 2016 |
| End Date: | August 31, 2022 (Estimated) |
| Total Intended Award Amount: | $180,348.00 |
| Total Awarded Amount to Date: | $180,348.00 |
| Funds Obligated to Date: |
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| History of Investigator: |
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| Recipient Sponsored Research Office: |
1500 SW JEFFERSON AVE CORVALLIS OR US 97331-8655 (541)737-4933 |
| Sponsor Congressional District: |
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| Primary Place of Performance: |
104 CEOAS Admin Bldg Corvallis OR US 97331-5503 |
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Performance Congressional District: |
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| Unique Entity Identifier (UEI): |
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| Parent UEI: |
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| NSF Program(s): | Marine Geology and Geophysics |
| Primary Program Source: |
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| 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
Almost 30% of the Pacific plate south of the equator formed in a period where Earth's magnetic field was exceptionally stable. During this Cretaceous period, the Ontong-Java-Nui (OJN) volcanic outpouring also occurred, creating a large plateau (1/100 of Earth's area) that eventually split apart. With no reversals of the magnetic field to generate the characteristic crustal anomalies that allow scientists to track tectonic plate motions, it has not been possible to understand the cause-effect relation between this deep magmatic generation and the change in plate motion at the surface. While satellite measurements provide broad indication of seafloor structure, it is not possible to discern the narrow abyssal hills that would have formed at the fast spreading centers that controlled the plateau breakup. More detailed seafloor mapping and sampling are required. Undergraduate and graduate students will receive training in marine geological data acquisition during this study and some will participate in post-cruise analysis via class projects. Podcasts of a research seminar will extend the reach of the new knowledge.
The OJN breakup is hypothesized to have occurred via spreading at the Osbourn Trough, along unmapped spreading centers in the Ellice Basin. Like other early Cretaceous oceanic plateaus, the OJN seems to have formed near a triple junction. Better understanding of Pacific tectonics during the Cretaceous normal superchron should shed light on the connections between oceanic plateau formation, breakup, plate reorganizations and associations with mantle plumes. In addition, paleolatitude data from the super-plateau remnants can to be tied to a common Pacific reference frame to refine the Pacific apparent polar wander path, which will then be compared with the Indo-Atlantic reference frame to determine the relative contributions from hotspot drift and true polar wander. Understanding evolution of OJN-linked processes is a long-term undertaking. This study takes the first step in this process with a multibeam survey of the Ellice Basin that will combine mapping of the central parts of this large basin where extinct spreading centers are likely to be located and remnants of fracture zones can be easily discerned. Coupled with selective dredging and Ar dating of basaltic rocks, as well as existing samples from IODP Site U1365 near Osbourn Trough, it will be possible to determine the timing of the inferred change in spreading direction, termination of Ellice Basin spreading, and the end of rifting along the Osbourn Trough.
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.
Ontong Java Nui is proposed to have been the largest volcanic system on Earth when it erupted some 120 million years ago on the sea floor in the Pacific Ocean. Shortly after it erupted, plate tectonics supposedly split this massive volcanic feature into five fragments that drifted away from each other. The major goals of the project were to plan and undertake a reconnaissance survey of the Cretaceous Ellice Basin in the South Pacific, which formed between two of those five fragments, to collect multibeam bathymetry, to obtain datable seafloor rocks from selected dredge targets, and to collect new radiometric age and geochemistry results from the dredge samples collected in the Ellice Basin, but also from ocean drilling samples in the Osbourn Basin, which formed between yet tow other Ontong Java Nui fragments. Our results show that all three fragments separated extremely rapidly, possibly as much as 4X faster than any plate tectonics today, and stopped in roughly their current configuration only 20 million years after they began splitting apart. We also show that the source of the magma in one of the basins, the Ellice Basin, differed slightly from the initial volcanism that made up Ontong Java Nui as a whole. This is the first age and geochemistry data for the Ellice Basin, and it along with our new ages from the Osbourn Basin, are critical to further understanding the eruption and breakup history of Ontong Java Nui.
Last Modified: 03/27/2023
Modified by: Anthony Koppers
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