Block of petrified wood encountered on a bed of popcorn soil during the Assn. of American State Geologist field trip to the back country of Petrified Forest National Park. The wood weathered out of the Chinle Formation (Late Triassic, 210-230 Ma), a colorful mudstone, such as in the Painted Desert, and less abundant lenses of sandstone and conglomerate, deposited by a large river system.
For a 1:50,000 scale geologic map of the Park: Jeff Martz, Bill Parker and others, 2012, Geologic Map of Petrified Forest National Park, Arizona. Arizona Geological Survey Contributed Map CM-12-A, 1 map sheet, map scale 1:50,000,18 p. http://repository.azgs.az.gov/uri_gin/azgs/dlio/1487