| NSF Org: |
EAR Division Of Earth Sciences |
| Recipient: |
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| Initial Amendment Date: | July 26, 2013 |
| Latest Amendment Date: | July 26, 2013 |
| Award Number: | 1324939 |
| Award Instrument: | Standard Grant |
| Program Manager: |
Justin Lawrence
jlawrenc@nsf.gov (703)292-2425 EAR Division Of Earth Sciences GEO Directorate for Geosciences |
| Start Date: | August 15, 2013 |
| End Date: | July 31, 2016 (Estimated) |
| Total Intended Award Amount: | $19,113.00 |
| Total Awarded Amount to Date: | $19,113.00 |
| Funds Obligated to Date: |
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| History of Investigator: |
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| Recipient Sponsored Research Office: |
9001 Stockdale Hwy Bakersfield CA US 93311-1022 (661)654-2233 |
| Sponsor Congressional District: |
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| Primary Place of Performance: |
1000 East University Avenue Laramie WY US 82071-2000 |
| 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): | Geomorphology & Land-use Dynam |
| 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
Understanding patterns of erosion and sedimentation in mountains is important for Earth scientists and land-use managers alike. Over management timescales, eroded sediment affects water quality, influences the amount and quality of aquatic habitat in rivers, and determines the lifespan of both natural and manmade reservoirs by setting the pace of sedimentation within them. Over longer, geologic timescales, eroded sediment also influences landscape erosion by providing rivers with the tools they need to cut into underlying bedrock and thereby adjust to changes in climate and tectonic forcing. Thus, the erosion of sediment is both the product of and a key driving force behind landscape change. Work funded by this grant will develop new methods for interrogating sediment about where it comes from, how it is generated, and how fast it moves across landscapes. This should permit progress on understanding erosional processes and how they influence landscape response to climatic and tectonic forcing.
Geologists have long recognized that sediment contains a wealth of information about its journey from intact rock on hillslopes to the jumbles of particles that cover modern riverbeds and fill ancient sedimentary deposits. Extraction of this information has become increasingly sophisticated with recent technological and methodological advances. As a result, understanding of surface processes has become increasingly quantitative. For example, rates of erosion from slopes can now often be measured from cosmogenic nuclides, which build up in sediment grains when they are near Earth's surface. Meanwhile, recent studies have shown that the clockwork-like buildup of radiogenic helium in the mineral apatite can be used as a fingerprint of where sediment comes from on catchment slopes. Here, this apatite-helium tracing technique will be used together with cosmogenic nuclides in a completely new way, to simultaneously unveil spatial variations in both the erosion rates and sizes of sediment produced on hillslopes by bedrock weathering. This marks an important advance in sediment tracing; until now, there was no way to quantify how the sizes of eroded sediment vary over catchment scales. Preliminary results show a connection between the elevation of slopes and the sizes of sediment that they produce by weathering and erosion. Higher-elevation slopes, which are colder and less vegetated, produce coarser sediment. This points to climate as a key regulator of sediment size. The proposed research will test the new sediment tracing approach in a steep catchment and explore hypotheses about linkages between climate and the sizes of eroded sediment. Expected outgrowths of this research include fresh insight on common, but as-yet incompletely understood downstream trends in landscapes, such as: fining in grain size in mountain streambeds; shifts from braided to meandering channel forms; and changes in aquatic habitats and the organisms that populate them.
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 goal of this collaborative research project was to develop and test a new geochemical technique that identifies how the initial size of sediment supply varies with altitude across steep mountain catchments. The technique couples two widely used sediment-tracing methods in a completely new way; cosmogenic nuclides are measured together with thermochronometric ages in a range of sediment sizes. The results are then analyzed and interpreted to reveal the pace of sediment erosion from slopes and the altitude at which individual sediment particles were produced. These measurements provide a solution for how the initial size distribution of eroded sediment varies with elevation.
The goal for my portion of the collaborative research project was to explore the use of detrital apatite fission track (AFT) thermochronometry as a new way to trace the location where sediment was produced within a mountain catchment. This method has the potential to confirm sediment source areas identified by other methods and to function as the primary method where other techniques are unsuitable.
This project supported an early career researcher at a minority serving institution and helped to justify the development of new laboratory facilities at California State University, Bakersfield (CSUB). The high-quality optical microscope used for fission track analyses is the only such microscope accessible to researchers and students in the Dept. of Geological Sciences. This microscope, and the fission track thermochronometric methods that it permits, have already been incorporated into several course activities and student research projects. The availablity of high-quality research equipment and exposure to different analytical techniques has assisted the CSUB Dept. of Geological Sciences to recruit and retain a diverse student body interested in STEM fields.
The necessary calibration of the microscope/analyst is close to completion. Bedrock and sediment samples collected as part of this collaborative research project are currently being dated. Results from this study are planned to be presented at the 2017 Annual Meeting of the Geological Society of America in Fall of 2017 (Seattle, WA) and will be submitted for publication shortly thereafter.
Last Modified: 10/29/2016
Modified by: William C Krugh
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