Week 4 Recap

On Monday, I finished sifting all of our dried sediment samples so that Jim Ingle can more easily identify foraminifera in our followup meeting. I also looked at the coral and shells samples under a microscope, which led me to subject them to one more cleaning, since there were still visible detrital sand and silt grains.

I devoted most of Tuesday and Wednesday to reading papers and reviewing equations. I also re-derived the equations for the Osmond 3D isochron, which helped clarify several points of confusion.

On Friday we met with Peter Blisniuk to talk about the potential application of oxygen isotopes on our carbonates. Delta-18-O in marine carbonates is dependent on water temperature, meaning it serves as a proxy for sea level in deep-water environments but is more difficult to interpret in shallow-water settings where high-frequency temperature flux is significant.

While Karrie is out of town and the U/Th prescreening lab work is on hold, I will powder and weigh out carbonate samples for oxygen and carbon isotope analysis to be performed next week.

I selected 30 different samples (the most that can be run for oxygen isotopes in one day) and photographed the individual shells and corals with the microscope-camera facility in the Payne lab.

I read and took notes on the following papers:

Muhs, D.R., Kennedy, G.L., and Rockwell, T.K., 1994, Uranium-Series Ages of Marine Terrace Corals from the Pacific Coast of North America and Implications for Last-Interglacial Sea Level History: Quaternary Research, v. 42, p. 72-87.

Kaufman, A. and Broecker, W.S., 1965, Comparison of 230-Th and 14-C Ages for Carbonate Materials from Lakes Lahontan and Bonneville: Journal of Geophysical Research, v. 70, p. 4039-4054.

Magnani, G., Bartolomei, P., Cavulli, F., Esposito, M., Marino, E.C., Neri, M., Rizzo, A., Scaruffi, S., and Tosi, M., 2007, U-series and radiocarbon dates on mollusc shells from the uppermost layer of the archaeological site of KHB-1, Ra's al Khabbah, Oman: Journal of Archaeological Science, v. 34, p. 749-755.

Szabo, B.J., 1979, 230-Th, 231-Pa, and open system dating of fossil corals and shells: Journal of Geophysical Research - Oceans, v. 84, p. 4927-4930.