Transcript of Nicole Grabos and Erin Argyilan PhD (Advisor) Department of Geosciences- Indiana University...
- Slide 1
- Nicole Grabos and Erin Argyilan PhD (Advisor) Department of
Geosciences- Indiana University Northwest Field Methodology of
Optically Stimulated Luminescence (OSL) Dating of Parabolic Dunes
Along the Southern Shoreline of Lake Michigan
- Slide 2
- Outline Study Background Site Location Methodology Results
Conclusions Study Accomplishments
- Slide 3
- Evolution of Parabolic Dune Formation What amount of time is
preserved in a single dune? What is the most reliable age for dune
stabilization? Can Particle Size Analysis (PSA) be used to observe
depositional patterns and locate optimal points of
stabilization?
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- Field Methods of OSL Samples were collected below bioturbation
within the C- horizon PSA was collected from individual horizons to
observe changes in grain transport
- Slide 5
- Optically Stimulated Luminescence (OSL) Dating OSL will
determine the age of burial on individual quartz grains
Single-Aliquot Regeneration Method o Up to 90 aliquots are used to
determine the overall age Age = De/Dose rate o Dose Rate: Radiation
in the surrounding soil determined through atomic absorption o De:
Measure of energy accumulated in the grains
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- Study Design
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- Study Area: Southern Shoreline of Lake Michigan Toleston Beach
Deposits (4500 years old to present)
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- Sample Site: Inland Dunes A westerly oriented parabolic dune
was chosen north of Stagecoach Rd. just south of Inland Marsh in
Ogden Dunes. The dune size is approximately 1720 feet in diameter.
Total dune relief is approximately 50 feet. Sample placement was
adjusted due to interference from the adjoining dune to the
southeast.
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- Inland Dunes Results Evidence of grading, though a finer
resolution is necessary to define grainfall patterns Observable
differences in ages, though all overlap in error Bucket-Augering
yielded an older sample age
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- Sample Site: Dune Acres A easterly oriented (indicating a
south- westerly wind) parabolic dune was chosen just east of
Mineral Springs Rd. in Dune Acres. The dune size is approximately
2375 feet in diameter. Total dune relief is approximately 28.5
feet. Sample location was chosen due to well defined shape and
minimal interference by surrounding dunes.
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- Dune Acres Results Resolution was not fine enough to see
evidence of grainfall patterns Observable differences in ages,
though all overlap in error Bucket-Augering yielded an older sample
age
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- Conclusions Both dunes overlapped in error using the OSL
method, indicating that any part of the lee side would be
acceptable for an indication of stabilization In both cases, the
bucket augured sample yielded an older age, possibly due to
muddling of the sample. Therefore, the pit digging method may be a
more reliable approximation for stabilization. Grading was present
in the Inland Marsh sample, though a finer resolution would be
necessary to make distinguishable conclusions The combination of
PSA and OSL revealed that though the dunes were formed at roughly
the same period of time, migration history of individual dunes
could be interpreted using the PSA
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- Grant Accomplishments Formal presentations at both COAS
Undergraduate Research Conference and National Geological Society
of America (GSA) Conference Experience with ArcGIS mapping software
OSL sample processing in North Dakota State Universitys laboratory
Data was accepted for publication This data also served to fuel an
adjacent study that used the dune geomorphology, PSA, and OSL to
approximate a more accurate point of stabilization based on active
dune dynamics
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- References National Park Service. "Lake View." Indiana Dunes
National Lakeshore. Spring 2012. Web. Spring 2012. Sloss, Craig R.
"Coastal Dunes Geomorphology." Nature.com. Nature Publishing Group,
2012. Web. 05 Apr. 2012.. Mallinson, D. "Optically Stimulated
Luminescence Is a Method of Determining the Age Ofburial of Quartz
or Feldspar Bearing Sediments Based upon Principles Ofradiation and
Excitation within Crystal Lattices, and Stems from the Fact
Thatimperfections in a Crystal Latt." A Brief Description of
Optically Stimulated Luminescence Dating. 2008. Web. 05 Apr.
2012..