* The major elements within tephra samples were identified using the Department of Geology and Geophysics at the University of Alaska’s Cameca SX-50 Electron Microprobe. The analytical routine, as discussed in chapter 3, was adapted for this projects samples from the work done by Beget et al. (1994b).
Old Crow tephra was used as a working standard due to its homogeneity and its strong chemical repeatability in past runs. Calibration of the samples off the Old Crow’s standard data provided consistency checks for in all of the microprobe runs and the end analysis. All of the major elements were normalized and reported as oxides with iron being Fe2O3. The descriptions are from the appearance and location of the tephra layer in situ. The tephra grain-size terminology is from Table AA 1.1 (Fisher, 1961; Schmid, 1981; Chough and Sohn, 1990). *