Provenance of a modern soil of Middle Tennessee assessed using trace elements and zircon U-Pb geochr...
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Provenance of a modern soil of Middle Tennessee assessed using trace elements and zircon U-Pb geochronology. KATSIAFICAS, Nathan J. and AYERS, John C. Department of Earth & Environmental Sciences, Vanderbilt University, 2301 Vanderbilt Pl, PMB 351805, Nashville, TN 37235.

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Katsiaficas nathan j and ayers john c

Provenance of a modern soil of Middle Tennessee assessed using trace elements and zircon U-Pb geochronology

KATSIAFICAS, Nathan J. and AYERS, John C.

Department of Earth & Environmental Sciences, Vanderbilt University, 2301 Vanderbilt Pl, PMB 351805, Nashville, TN 37235


Harpeth river terrace soils

Harpeth River Terrace Soils

  • Huckemeyer (1999) hypothesized loess component in terrace soils

  • We are testing her hypothesis using zircon U-Pb geochronology and immobile trace element concentration ratios

Huckemeyer (1999)


Field site

Field Site

  • Ultisols atop Sangamon age equivalent terrace (~128-75 ka)

  • Fort Payne Fm. (Mfp) Mississippian cherty limestone bedrock (Wilson, 1990)

Soil data from NRCS (2012)


Sampling

Sampling

B1

B2


Bulk samples

Bulk Samples

  • Whole rock and soil samples fused to glass with LiBO2

  • Glasses analyzed for major elements and trace elements using LA-ICP-MS

  • Concentration ratios of immobile trace elements (e.g. Nb, Ta, Zr, etc…)


Major element concentrations

Major Element Concentrations

  • Measured using EDS


Bulk sample immobile trace e lement c oncentration ratios

Bulk Sample Immobile Trace Element Concentration Ratios


Bulk sample immobile trace e lement c oncentration ratios1

Bulk Sample Immobile Trace Element Concentration Ratios


Grain size and density

Grain Size and Density


Element mass fluxes

Element Mass Fluxes

Brimhall et al. (1991)

B1: 85% volume removal of Mfp

B2: 80% volume removal of Mfp

  • Mass fluxes ≤ 0 consistent with bedrock source


Zircon

Zircon!

  • Standard mineral separation procedures to concentrate heavy minerals

  • BSE and CL imaging of zircon on SEM

  • Trace elements and U-Pb dating of zircon using LA-ICP-MS with 20 μm spot size

  • Construction of age spectra for each sample

B2

B1

Mfp


Zircon trace elements

Zircon Trace Elements


Zircon trace elements1

Zircon Trace Elements


Zircon u pb

Zircon U-Pb


Age spectra

Age Spectra


Trace element ratios and element mass fluxes vs u pb analyses

Trace Element Ratios and Element Mass Fluxes vs. U-Pb Analyses

  • Bulk immobile trace element ratios:

    • Similar origins for B1 and B2

    • Lack of similarity of overlying soils to Mfp

  • Element Mass Fluxes

    • Consistent with derivation of B1 and B2 from Mfp

  • Zircon U-Pb analyses:

    • Input of outside source for B1?

    • Some component of Mfp in B1 and B2?

  • Soils atop Mfp formed from insoluble residue?

  • Other potential end-member parent materials

    • Loess (Peoria)

    • Alluvium


Future work

Future Work

  • Future analyses to be conducted on Thermo iCAP Qc ICP‐MS with 193nm excimer laser

  • Limestone soil/bedrock pair and potential end-member parent materials

  • Larger populations of zircon

  • Addition of monazite U-Th-Pb ages?


Potential implications

Potential Implications

  • Use of zircon and potentially monazite for soil provenance in regions with limestone bedrock

  • Potentially, Peoria loess presence further south and east than previously documented

  • Possibility of tracing zircon in bedrock to sources of clastic input at time of deposition


Acknowledgements

Acknowledgements

  • GSA Southeastern Section Graduate Research Grant

  • Assistance from Vanderbilt EES students and faculty, especially Aaron Covey, Susanne McDowell, Abraham Padilla, and Tamara Carley

  • High school student collaborator, Camille Lasley


Works cited

Works Cited

  • Brimhall, G.H., Lewis, C.J., Compston, W., Williams, I.S., and Reinfrank, R.F., 1994, Darwinian zircons as provenance tracers of dust-size exotic components in laterites: mass balance and SHRIMP ion microprobe results, in Ringrose-Voase, A.J., and Humphreys, G.S., eds., Soil Micromorphology: Studies in Management and Genesis: Amsterdam, Elsevier, Developments in Soil Science, v. 22, p. 65-81.

  • Huckemeyer, J.L., 1999, Late Quaternary Alluvial Stratigraphy and Soil Development Along the Harpeth River, Central Tennessee: Nashville, TN, Vanderbilt University Press, 192 p.

  • NRCS, 2012, Gridded Soil Survey Geographic (gSSURGO) Database for Tennessee: United States Department of Agriculture, National Resources Conservation Council. Available at: http://datagateway.nrcs.usda.gov (Accessed March, 2013).

  • Wilson, C.W., 1990, The Geology of Nashville, TN: Nashville, TN, State of Tennessee, Dept. of Environment and Conservation, Division of Geology, 172 p.


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