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My students and I are currently engaged in the following research:
(1) Using the stable isotopic ratios of fossil corals from the Dominican Republic to understand what shallow ocean conditions were like before the Isthmus of Panama fully formed and isolated the Caribbean and Pacific oceans.
(2) Using the stable isotopic ratios and the uranium-thorium ages of stalagmites to reconstruct what climates were like over the last several hundred thousand years in:
- the Great Basin (Nevada)
- the Ozarks
- in Portugal
(3) Using the mineralogy of stalagmites from Nepal to better understand variations in the amount of rain associated with the Indian summer monsoon over the last several thousand years (in conjunction with Dr. Luis Gonzalez, University of Kansas)
Student Projects
2005
Amanda Gibson ('08) (below right) and Charles Trodick ('07) (below left) worked from June through August in Dr. Asmerom's radiogenic isotope mass spectrometry lab at the University of New Mexico. Using uranium-thorium disequilibrium techniques, they dated numerous stalagmites from several caves from Nevada and Portugal. The data from the Nevada cave is the subject of a paper that we're about to submit for review which explores the relationship between millenial-scale climate variability in Greenland and the Great Basin of the western United States. The Portuguese work, while still in its infancy, is also showing a relationship with the North Atlantic. |
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Lara Moellers ('06) (left) and Diana Krogmeier ('07) (right) dated two stalagmites from northwestern Arkansas during December 2005. Both stalagmites grew across glacial/interglacial transitions (16-6 ka and 145-126 ka). Both speleothems have been sampled at 3 mm intervals for carbon and oxygen stable isotopic analysis, and we anxiously await the results. |
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| Mike Lommler ('06) tied annual growth banding (identified from X-radiographs) from 7 million-year-old corals from the Dominican Republic to sinusoids in Sr/Ca and U/Ca ratios measured across the growth bands using laser ablation mass spectrometry at the Australian National University. Using published equations, Mike converted both Sr/Ca and U/Ca ratios to sea surface temperatures. |
2004
| Peter Cole ('05) (below) and Brian Hoye ('06) (right) spent the summer with me working in Dr. Yemane Asmerom's radiogenic isotope mass spectrometry lab at the University of New Mexico. Using uranium-thorium disequilibrium techniques, they dated numerous stalagmites from several caves including some from Nevada. Brian concentrated on building a chronology of an Arkansas stalagmite that grew from 21,000 - 16,000 years ago, an interval of particular interest to many paleoclimatologists. He is currently analyzing this stalagmite using stable isotopes at the University of Iowa. |
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Peter used a combination of uranium-thorium and uranium-lead dating methods to constrain the age of fossil corals from the Dominican Republic. He is currently obtaining high-resolution stable isotope analyses of these corals in order to reconstruct how seasonal temperatures changed in the Caribbean five million years ago when cool Pacific waters were stilling flowing into the Caribbean between North and South American. When the Isthmus of Panama fully formed, it altered ocean conditions and is believed to be responsible for several extinctions of Caribbean fauna. |
| Alyssa Borowske ('08)and I spent a week caving in Portugal in early June. Significant archeological exploration has been performed in many areas of the country, but little paleoclimatic information is available to tie into it. Our goal is to use the paleoclimate indicators in stalagmites to help archeologists better understand the climatic context in which archeological changes occurred. Here, Alyssa is standing in a newly-discovered cave complete with bones and artifacts. |
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Alexa Clements continued her work on a New Zealand flowstone by obtaining high-resolution stable isotope analyses at the University of Iowa. Here she is using the joy-stick on the computer-guided microsampler. |
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2003
| Stephanie Penn ('05) and I collected fossil corals from the Dominican Republic with a team of paleontologists from the University of Iowa, the City College of New York, the University of Miami, and the University of Illinois. Stephanie then spent much of the summer cutting, polishing, and examining ther samples for signs of diagenetic alteration, and finally analyzing "pristine" corals using stable isotopic techniques. |
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Alexa Clements ('05) spent much of the summer preparing and analyzing a core from a New Zealand flowstone. High-resolution paleoclimate records are rare in the South Pacific, and this cave deposit, which spans the last 35,000 years, is known tocontain evidence of environmental change at a coarse scale. Our goal is to see what, if any, new information may be gleaned from a much finer scale analysis. |
2002
| Michelle DuPree ('02) did two projects. First, she and I spent the summer dating stalagmites from Nepal at the University of New Mexico. Evidence suggests that the type of mineral present in a stalagmite (calcite vs aragonite) reflects conditions in the cave, in particular, cave aridity. Dating these mineralogical transitions allows us to better understand which time periods when the Indian summer monsoon was particularly strong (wet) and when it was weak (dry). |
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Secondly, Michelle collected stalagmites from Devils Ice Box Cave, central Missouri. After cutting and polishing, she dated them at the University of New Mexico and collected stable isotopic data. Her samples grew from 3500 to 1000 years ago and appear to record shifts between prairie and savannah environments over the cave. Jill Leonard ('02) joined us on the caving trip. |
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