Petrified and charcoalified woods were collected from the Dawson Creek region of Big Bend National Park. The results of the various tests conducted on the fossils were reported in Parts I—IV of this series along with a creationist interpretation of petrifaction and charcoalifaction. Samples of the clays, in which the fossil woods were located, were gathered with permission of the Park Service. Tests were performed on the clays to determine their origin and the nature of diagenetic processes acting upon them. The clays are believed to be of volcanic origin. The original volcanic ash was altered to form bentonitic clays. This alteration probably occurred in the late stages of the Flood or soon thereafter in a post-Flood temperate climate in Trans-Pecos Texas.