| NSF Org: |
OCE Division Of Ocean Sciences |
| Recipient: |
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| Initial Amendment Date: | April 12, 2013 |
| Latest Amendment Date: | July 29, 2013 |
| Award Number: | 1341047 |
| Award Instrument: | Continuing Grant |
| Program Manager: |
Barbara Ransom
bransom@nsf.gov (703)292-7792 OCE Division Of Ocean Sciences GEO Directorate for Geosciences |
| Start Date: | March 2, 2013 |
| End Date: | August 31, 2016 (Estimated) |
| Total Intended Award Amount: | $137,501.00 |
| Total Awarded Amount to Date: | $137,501.00 |
| Funds Obligated to Date: |
FY 2012 = $41,895.00 FY 2013 = $1.00 |
| History of Investigator: |
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| Recipient Sponsored Research Office: |
4300 MARTIN LUTHER KING BLVD HOUSTON TX US 77204-3067 (713)743-5773 |
| Sponsor Congressional District: |
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| Primary Place of Performance: |
TX US 77204-2015 |
| 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): | Marine Geology and Geophysics |
| Primary Program Source: |
01001213DB NSF RESEARCH & RELATED ACTIVIT 01001314DB 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
The cause of the bifurcating tracks of seamounts and seafloor swells in the Walvis Ridge area in the South Atlantic just off South Africa has been a longstanding enigma in Marine Geology and in our understanding of hotspots and the plate tectonic evolution of Africa. This project will go to sea to dredge and analyze rocks from the part of the seafloor to the west of the Walvis Ridge and examine changes from hotspot to diffuse volcanism. The present location of the Walvis hotspot and the reason for its waning volcanic activity over the last 60 Myr will also be determined. Argon trapped in minerals in the collected seafloor volcanic rocks will be used to determine the age progression of the volcano tracks. Rock, major and trace element geochemistry and isotopes will be used to see if the younger rocks in the bifurcated tracks can be linked to the older Walvis Ridge. Multibeam bathymetric mapping and a map of seafloor magnetics will also be generated to examine structural trends and plate tectonic motions of this part of the ocean floor. Broader impacts of the work include international collaboration with a complementary German effort that is studying the older part of the Walvis Ridge, K-12 teacher and graduate and undergraduate student training, and support of a PI whose gender is under-represented in the sciences.
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 overarching objective of this project is to understand the geological development of the younger Walvis Ridge and how it fits models of hotspot-ridge interaction and hotspot track development. Walvis Ridge is part of a system of volcanics stretching across the south Atlantic ocean and is thought to have formed by the interaction of a mantle plume with the Mid-Atlantic Ridge. Other important portions of this system at the Parana and Etendeka continental flood basalts, on South American and Africa, respectively, and the Rio Grande Rise oceanic plateau on the South American plate off Brazil. In fact, the Tristan hotspot (that formed Walvis Ridge) is one of the few that can be traced back to continental flood basalt provinces. The Walvis Ridge is signficant because it is the main hotspot chain that constrains African plate motion in absolute motion models. Nevertheless, Walvis Ridge and Rio Grande Rise have very different morphologies, and Walvis Ridge itself changes morphology from a high ridge near Africa to several small seamount chains ending in two active volcanoes (Tristan and Gough islands). These complications are not expected in the simple mantle plume model.
This collaborative project brought together three investigators to examine different aspects. Co-PI Anthony Koppers (Oregon State University) is determinig radiometric ages for dredge samples and Cornelia Class (Lamont Doherty Earth Observatory) is measuring geochemisty and isotopic chemistry of dredged samples. These two parts were the main focus of the project and the research cruise (MV1203) of the R/V Melville, which dredged many seamounts in the younger Walvis Ridge. The Texas A&M University (University of Houston) part was to study geophysical data collected on the cruise and other existing geophysical data with the goal of better understanding the development of the Walvis Ridge.
The TAMU/UH portion of the project has examined magnetic anomaly data in the vicinity of Walvis Ridge. This has been an unusually difficult task because many of the data that were used to identify magnetic anomalies during the 1980s were US Navy data and are now lost. We have examined magnetic data taken during cruise MV1203 to confirm the magnetic anomalies along the tracks and they have not changed the anomaly pattern signficantly. However, this work has provided background for writing a future proposal to collect new magnetic data. This part of the project also examined magnetic anomalies around Rio Grande Rise as well as the tectonic fault fabric that is visible in satellite altimetry-derived gravity data. The gravity data suggest some tectonic anomalies around Walvis Ridge and Rio Grande Rise at the time they were together at the Mid-Atlantic Ridge. We developed a model that explains this by the formation of these igneous mountains around a microplate. This model is the basis for two proposals submitted to the International Discovery Program (IODP) for drilling in the South Atlantic. One proposes drilling on Walvis Ridge to examine the geochemical development of two different geochemical trends with the split into several seamount chains in the young part of the ridge and to examine the microplate model for the older part. The other proposal, submitted in collaboration with Brazilian colleagues, will drill the Rio Grande Rise to get a similar picture from the South American portion of this igneous province.
Last Modified: 12/05/2016
Modified by: William W Sager
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