Is the Chattanooga Shale an ash-fall deposit?
Mr. Froede makes the following assertion: Additionally, as previously cited, many of the radioactive shale and clay layers are found as laterally continuous units which extend over thousands of square miles [three references], and this clearly fits within a description of a volcanic ash fall. Mr. Froede makes a valid statement that the units are very widespread but then makes an unfounded assertion that this is evidence for an ash fall. One way to determine if the Chattanooga Shale is an ash fall deposit would be to compare the isopachs (maps connecting points of equal thickness) of the Chattanooga Shale and its correlatives with isopachs of known volcanic ash falls. The isopach for the major eruption of Mt. St. Helens on May 18, 1980, is shown in Figure 1 (Sarna-Wojcicki, et al., 1981, fig. 336). A map for the much larger eruption of Mt. Pinatubo in the Philippines is shown in Figure 2 (Wiesner, et al., 1995, fig. 1). Note that the thicknesses are expressed in millimeters for Figure 1
