| NSF Org: |
EAR Division Of Earth Sciences |
| Recipient: |
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| Initial Amendment Date: | June 26, 2019 |
| Latest Amendment Date: | June 26, 2019 |
| Award Number: | 1839301 |
| Award Instrument: | Standard Grant |
| Program Manager: |
Audrey Huerta
EAR Division Of Earth Sciences GEO Directorate for Geosciences |
| Start Date: | July 1, 2019 |
| End Date: | March 31, 2023 (Estimated) |
| Total Intended Award Amount: | $216,559.00 |
| Total Awarded Amount to Date: | $216,559.00 |
| Funds Obligated to Date: |
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| History of Investigator: |
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| Recipient Sponsored Research Office: |
6300 E STATE UNIVERSITY DR STE 332 LONG BEACH CA US 90815-4670 (562)985-8051 |
| Sponsor Congressional District: |
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| Primary Place of Performance: |
1250 Bellflower Blvd. Long Beach CA US 90840-0004 |
| 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): | Tectonics |
| Primary Program Source: |
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| Program Reference Code(s): | |
| Program Element Code(s): |
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| Award Agency Code: | 4900 |
| Fund Agency Code: | 4900 |
| Assistance Listing Number(s): | 47.050 |
ABSTRACT
The origin and development of mountain belts has long been of special interest to people and a primary target of research in the Earth Sciences. This study will advance our scientific understanding of the processes that control the uplift of mountains by studying the patterns and rates of elevation change in an actively-growing mountain belt. The western Transverse Ranges of California are being uplifted by compression along the boundary between the North American and Pacific tectonic plates. In addition to the uplift of individual mountain ranges along specific faults, the lower valley areas are also rising, indicating a deeper cause to the regional uplift of the mountains. Old floodplains that have been lifted above their rivers by tectonic forces will be used as reference markers to measure the amount and rate of tectonic uplift and investigate how local vs. regional mechanisms contribute to mountain growth. The scientific advances associated with this project are coupled with training and education of both graduate and undergraduate students at a Hispanic Serving Institution that emphasizes inclusion of underrepresented groups in Science, Technology, Engineering, and Mathematics (STEM) fields. The project will also benefit the local population of southern California through enhancing understanding of regional seismic hazards posed by the faults that bound and underlie the western Transverse Ranges.
Regional uplift affects an entire mountain belt, whereas local uplift results in the production of relief in the form of individual ranges and valleys. The western Transverse Ranges (WTR) of California are an active fold and thrust belt where high rates of shortening have been interpreted from geodetic studies and from geologic reconstructions. Uplift rates based on marine terraces and river terraces along the southern coast of the WTR are as high as 7 millimeters per year but vary dramatically along the coast across faults and folds that trend oblique to the coast. These high uplift rates, as measured in the elevated hanging walls of reverse faults or actively growing anticlines, are local uplift rates that are most likely not characteristic of the entire mountain belt. This project will develop a more complete picture of topographic development in the WTR by using previously unstudied fluvial strath terraces present within the WTR, and marine terraces along the western coast, as markers for vertical deformation across the mountain belt. The terraces have been offset and lifted in the hangingwalls of reverse faults, but their presence in the footwall valleys as well indicate an additional component of regional uplift that must be occurring on deeper structures. Thus, it is possible to measure both local and regional uplift and separate the two components. Luminescence and radiocarbon dating will be used to establish a Late Quaternary chronology of the terraces to calculate the timing and rate of deformation and topographic development.
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
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.
This project revealed several interesting aspects of the western Transverse Ranges of California that hold implications how mountain belts are formed and how the faults that lift those mountain belts interact. First, we found that the ranges in the mountain belt are lifted along faults that intersect the surface, but that there is also a deeper squeezing and lifting of the entire area such that the valleys are also rising. Second, we found that this uplift is not constant through time, but that some of the ranges and hills were rising fast between ~85 and 45 thousand years ago, but have since slowed dramatically, or completely stopped rising. This is the result of changes in the rate of slip along the faults that underly the ranges; some of the faults in the area have slowed down over the past 50 thousand years, while others have likely increased. This surprising result is important for understanding earthquake hazards. Third, we dated a large number of river and coastal terrace deposits that have been lifted by faults above the current rivers or sea level. We found that the river terraces and coastal terraces are the same age and that their formation is controlled by climatic variations over the past 100 thousand years. This confirms previous interpretations in the region and the large number of new age constraints will help future studies understand how river systems work and interact with changing sea level.
This project also supported the mentoring and training of six graduate students, and five undergraduate students, half of whom are from under-represented groups in the geosciences. All of these students have gone on to well-paid geoscience careers or futher graduate studies.
This project also led to the revival of the Southern California Vertical Motion Database, which is a collation of tectonic uplift and subsidence data from the region that is available to researchers, government agencies, and the public online and is being hosted by the Southern California Earthquake Center.
The results of this project have been dissimenated through three peer-reviewed journal publications, numerous geologic meeting presentations, public talks, and incorporation into teaching materials at CSU Long Beach.
Last Modified: 05/30/2023
Modified by: Nathan Onderdonk
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