| NSF Org: |
EAR Division Of Earth Sciences |
| Recipient: |
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| Initial Amendment Date: | February 16, 2018 |
| Latest Amendment Date: | February 16, 2018 |
| Award Number: | 1745743 |
| 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: | March 1, 2018 |
| End Date: | February 28, 2022 (Estimated) |
| Total Intended Award Amount: | $150,320.00 |
| Total Awarded Amount to Date: | $150,320.00 |
| Funds Obligated to Date: |
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| History of Investigator: |
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| Recipient Sponsored Research Office: |
2215 RAGGIO PKWY RENO NV US 89512-1095 (775)673-7300 |
| Sponsor Congressional District: |
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| Primary Place of Performance: |
2215 Raggio Pkwy Reno NV US 89512-1095 |
| 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): | |
| Program Element Code(s): |
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| Award Agency Code: | 4900 |
| Fund Agency Code: | 4900 |
| Assistance Listing Number(s): | 47.050 |
ABSTRACT
The Eastern Pacific Ocean in the Northern Hemisphere is one of the most prolific regions on Earth in terms of generation of intense tropical cyclones that make landfall on the coasts of arid southwestern North America and dramatically enhance runoff, flooding, and associated erosion and sedimentation. Recent research indicates that these large-scale events have altered the hydrological and ecosystem balances over historical and geological timescales (decades to thousands of years). This project will assess how far north along the coast of southwestern North America these storms have occurred in the geologic past, and how far inland they controlled geomorphic change events through rain and erosion. The specific goal is to determine if previously documented periods when tropical cyclones dominated runoff and sediment deposition across large alluvial fan systems of the southern Baja California peninsula can be detected in central Baja California, the southern California deserts, and even as far north as the southern Arizona Sonoran Desert. Data will test whether dissipating cyclones were drivers of alluvial fan sedimentation over thousands of years, and if a temporal correlation can be established to a period of transition between a milder, humid paleoclimate to the current arid climate. For the first time, a tropical cyclone landfall chronology covering the last few millennia will be developed for the Pacific coast of southwestern North America. This research has the potential to inform large-storm prediction scenarios for southern California and northwestern Mexico, which is relevant to hazards management for communities in need of risk assessment of rare and extreme events. The project will contribute to the training of the next generation of earth scientists using a tiered approach, with field-based collaboration of postdoctoral fellows, graduate and undergraduate students. This approach has been proven successful for inclusion of underrepresented minorities, enhanced also with planned research alongside Mexican collaborators and students. The project will provide unique broader educational experiences for grade-school students in Indiana and Arizona, through the use of technology to connect fieldwork and classrooms.
This project will compare a recently established alluvial fan chronology in southern Baja California, with newly-obtained alluvial fan and paleotempestological records. A Holocene paleotempestological record of overwash deposits in the Pacific coastal Vizcaino Desert will be developed for the first time. The inferred tropical storm activity will be compared with inland alluvial fan deposition in this area and in the northern Sonoran Desert, enabling discrimination of signals from different moisture sources, based on observed coastal and alluvial sedimentology, stratigraphy, and specific proxy records. Effects of different sources of moisture that drive sedimentation will be assessed by probing different time periods, and compared to independent paleoclimatic proxies. Bayesian analysis of luminescence, cosmogenic, and radiocarbon geochronology will improve age control precision. The coupled alluvial and coastal record at orbital timescales will help to understand linkages between Quaternary alluvial sedimentation and hydroclimatic variability in the region, and will increase our understanding of basic principles of alluvial fan aggradation in response to change in arid hydroclimates. The project will test effects of millennial- and orbital-scale shifts in tropical circulation on landscape evolution of the region, which are, in turn, critical to test models of occurrence and effects of hydrological extremes and associated landscape changing events.
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.
The objective of this project is to determine the northern-most extent where periods of more intense and/or frequent tropical cyclones made landfall across arid southwestern North America during the Late Quaternary, likely coinciding with precessional increases in summer insolation in the eastern Pacific at 10-20 N. Results from previous research indicate that increases in tropical cyclone events are likely to be a primary source of regional precipitation responsible for generating large fluvial discharges and pronounced aggradation of alluvial fans. The project was designed to determine if impacts of the dissipating tropical cyclones were also a primary contributing factor on alluvial fan deposition in four study areas located in the Sonoran Desert: (1) Muggins Mountains, AZ, (2) Cibola/Trigo Peaks, AZ, (3) the Lower Colorado Desert containing a portion of the Anza-Borrego, south of Ocotillo, CA, and (4) the Vizcaino subregions of central Baja California (Mexico). The results of this research project expand on results from previous NSF-funded research (Antinao and McDonald, 2014) that develop a benchmark alluvial fan chronology in southern Baja California. Both NSF projects integrated detailed mapping of alluvial deposits with comprehensive soil stratigraphy to (1) subdivide local depositional units and (2) support developing a regional correlation, or stratigraphic framework, of alluvial depositional units. The core goal of this project was comprehensive integration of soil-stratigraphy (relative dating using models of soil development) and numerical ages (terrestrial cosmogenic, luminesce, and radiocarbon dating) to stratigraphically correlate alluvial depositional records developed in the four study areas with the alluvial record developed in Southern Baja. The overlying premise for this project was to determine if predominant cycles of regional alluvial fan could be established between southern Baja California and central Baja California and Southern California and SW Arizona. The presence of regionally correlative stratigraphic fan units demonstrates that periods of pronounced fan deposition associated with tropical cyclone systems in southern Baja California are also driving discrete periods of alluvial fan sedimentation in central the desert regions southern California and Arizona.
Results from this NSF project were also compiled with regional soil- and fan-stratigraphy and local pluvial records from three other study areas in the Mojave Desert, CA. These three study area are located marginal between the Providence Mountains and the Kelso Dunes, Pilot Knob Valley, and Panamint Valley. The resulting synthesis, spanning ~1800 km along southwest North America, represents the most regionally extensive and best dated compilation of alluvial fans yet assembled.
Major project results indicate that:
(1) Regional correlations, reinforced with soil-stratigraphy, indicate that major periods of alluvial fan deposition occurred ~0.5-1ka, 2-4 ka, 4-8 ka, ~10-15 ka, 30-40 ka, 60-70 ka, and ~100-110 ka and that the depositional record these events are common among multiple desert mountain basins. The pattern of regionally correlative alluvial fans has been commonly speculated and the results of this project provide compelling evidence to support this hypothesis.
(2) A key component thought to be driving fan deposition is a regional increase in precipitation associated with a pronounce increase in monsoonal storms. Similar timing between the end of the marine isotope stage (MIS) 4 and a pronounced cycle of regional fan deposition suggests a similar response to climate change which indicates a likely increase in dissipating tropical cyclones.
(3) Soil stratigraphy is essential for subdividing local fan deposits, reinforcing numerical age estimates, and supporting regional correlation among Quaternary units. The incorporation of soil stratigraphy provides critical field-based data to develop geomorphic, stratigraphic, and climatic models that can be subsequently tested through stratigraphy and numerical dating techniques
Intellectual Merit: Results increase knowledge of basic principles of how alluvial fan aggradations responds in response to change in hydroclimates at orbital timescales. For the first time, a regional to sub-continent record of alluvial fan chronology has been developed linking a landfall chronology of tropical cyclones with pronounced periods of alluvial fan formation across southwestern North America during the Late Quaternary.
Broader Impacts: Results demonstrate that major periods of alluvial fans reflect large-scale climatic processes such as an increase in the intensity and duration of precipitation. In the SW North America, the principle climatic driver must include the northern movement of dissipating East Pacific tropical cyclones. Specifically, results demonstrate (1) the existence of several cycles of alluvial fan deposition occur at periods shorter than interglacial-glacial cycles, which are usually called in common models as driving alluvial fan aggradation, and (2). Regionally extensive and repeated alluvial fan stratigraphy indicates that pronounced periods of fan deposition are climatical driven and overprint local- to regional tectonics
Last Modified: 08/29/2022
Modified by: Eric Mcdonald
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