299-6 Portable XRF Investigation of Tuffaceous Lacustrine Sediments in the Miocene Teewinot Formation, Jackson Hole, Wyoming, USA

Session: Geochemical Studies of Sediments (Posters)

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Abstract:

The use of portable x-ray fluorescence (pXRF) devices has become increasingly common in numerous aspects of science and industry.  In geology, their accuracy is significantly constrained by minimal sample preparation, spectral interference due to simultaneous collection of all wavelengths, and difficulty in the detection of elements at very low levels or of low atomic number. In comparison to laboratory methods such as XRF or ICP-MS, however, pXRF is much less expensive and offers much faster turn-around.

A total of 500 samples of loose sediment were collected from mapped locations of the late-Miocene Teewinot Formation in Jackson Hole, Wyoming, USA.  These comprised varying amounts of pyroclastic fragments, lacustrine limestone and clays, and Pleistocene loess.  After drying and sieving to < 250 microns, samples were examined microscopically, and those roughly containing >50% pyroclastics were analyzed using a Bruker Titan pXRF instrument in a desktop setup.  Calibration curves were constructed using 28 other rhyolitic samples for which laboratory analyses were available.  These showed good correlation for several elements.

 Inter-element plots of the Teewinot analyses reveal some distinct groupings which suggest the existence of between 3 and 5 chemical “types”.  This agrees with previous studies which employed various laboratory methods but fewer samples.  Overall, the method employed in this study, while limited with regard to definitive correlations, does provide useful supplementary information and is helpful in selecting samples for additional study.

Geological Society of America Abstracts with Programs. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-6974

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