Undegraduate Research

Undergraduate Geology Thesis

Title

Evaluation of Handheld XRF (HHXRF) in Sedimentary Lithology Discrimination of Unprepared Drill-Cores

Summary

May 1, 2016 – X-ray fluorescence (XRF) logs are a series of plots that show the variation of the concentrations of elements with depth in a drill-core. This study examined a 116-meter-long (380-foot-long) core drilled in Winnebago County, east-central Wisconsin, covering Cambrian through Ordovician strata. Researchers at the Wisconsin Geological and Natural History Survey (WGNHS) have generated a series of XRF logs on this core with a Thermo Scientific Niton XL3t GOLDD+ handheld XRF analyzer (HHXRF) under the factory calibration to improve lithological discrimination and identify unconformities.

The current study evaluated the reproducibility of this method by re-generating a series of XRF logs at 1-foot intervals using the same model of HHXRF and following the same protocol. The agreement across XRF logs from two studies was evaluated by correlation coefficients (r) from plots in which the concentrations of one element at a given depth from two studies are plotted on the x-axis and y-axis, respectively. Mg, Al, Si, K, Ca, and Fe have the best agreement with r ≥ 0.89. The XRF log of the dominant naturally-occurring radioactive element K and its gamma log have an agreement. To evaluate the precision and accuracy of the HHXRF, repeat analyses on three standard reference materials (USGS BIR-1, USGS W2, and NIST 2709a) over six months using the factory calibration indicate that the measurements of a number of major and trace elements are highly precise but generally inaccurate. Overall, rapidly-generated and cost-effective XRF logs may be effectively used to improve lithological discrimination.

Left: Thermo Scientific Niton XL3t GOLDD+ handheld X-ray fluorescence (XRF) and lead-lined box set up in laboratory. Top right: Scanning Electron Microscopy (SEM). Bottom right: Handheld XRF.

Acknowledgements

This research was supported by Department of Geology at Beloit College. I thank my advisors Professor James Rougvie* who provided insight and expertise that greatly assisted the research. I appreciate Professor Susan Swanson* and Professor Jay Zambito† for their efforts and time on loaning the cores from WGNHS.

I am grateful to Professor Carl Mendelson*, Steve Ballou*, and Professor George Lisensky** for their assistance. I would like to thank my friend Estiaque Shourov for comments that greatly improved the manuscript. I would also like to thank Professor Achim Herrmann° for his comments on dolomite diagenesis and Dr. Scott LaBrake†† for compiling the X-ray data table.

* Department of Geology, Beloit College, Beloit, WI

† Wisconsin Geological and Natural History Survey and University of Wisconsin-Extension

** Department of Chemistry, Beloit College, Beloit, WI ° Department of Geology & Geophysics, Louisiana State University, Baton Rouge, LA

†† Department of Physics and Astronomy, Union College, Schenectady, NY

Undergraduate Astronomy Research: Saturn's F-Ring

Title

Spatial calibration using Saturn's moons and identification of clumps in the F ring with brightness in Cassini images

Summary

May 1, 2016 – Saturn’s F ring is a narrow ring made of small particles that is tilted 0.0064° in relation to main rings. Cassini is an unmanned spacecraft, currently orbiting Saturn. Bright features orbiting through the F ring, known as clumps, represent high-density particle regions in the F ring. Previous researchers have studied images from Earth-based telescopes or Cassini when it flies above or below the ring plane. We studied high-resolution images (1024 × 1024 pixels) that were captured by the narrow-angle camera (NAC) as Cassini crosses the ring plane. We used brightness plots that total the brightness for every x-position in Cassini images to identify clumps. These images provide new insights on the vertical structure of the F ring, but cover only about one tenth of the radius of Saturn’s rings, due to the narrow field of view of NAC (0.35°). To determine which part of the ring is captured in the images and then make useful observations, we used the known ephemeris positions of Saturn’s moons, including Rhea, Dione, Mimas, and Enceladus, as reference points when they appear in the images. We adopted an approach similar to the Circular Hough Transform (CHT) to locate the centers of Saturn’s moons. Combined with ephemeris positions and the detected centers of the moons, we are able to express the offset right ascension (dRA) of identified clumps from brightness plots.

People

Advisor: Professor Britt Scharringhausen

Team members: Tiannong "Skyler" Dong, Rikely Buckingham (spring 2016), Martin Garcia(fall 2015), and Sarah Vermeland (fall 2015)