Fig. 2. Bivariate plots of pumice glass major and trace elements.

SiO₂ versus CaO (wt %) is shown in (A), and Sr versus Zr (ppm) is shown in (B). Each point is the pumice clast average of 7 to 15 analyses. Color scheme is similar to the schematic stratigraphic section in Fig. 1, but with statistically distinct pumice populations shown as different shades and shapes (see statistical analysis within the Materials and Methods section for details). Error bars represent ±1σ analytical uncertainty, based on repeat analyses of the RGM-1 glass secondary standard. See fig. S1 for a comparison of glass to whole-rock data.