Geologic Map of Petrified Forest National Park, Arizona

This geologic dataset covers the area within the boundaries of Petrified Forest National Park (PEFO), located in northeastern Arizona as defined prior to the expansion approved in December of 2004; much of the land in the approved expansion has not yet been acquired by the National Park Service, and is inaccessible to the public. The map is based on unpublished mapping by Billingsley (1985b), Johns (1988), Woody (2003), published mapping by Martz and Parker (2010), and new mapping. The geology of the Little Colorado River Valley in eastern Arizona, including the PEFO area, is characterized by widespread exposures of Triassic and Jurassic terrestrial sedimentary rocks. The Upper Triassic Chinle Formation constitutes the bulk of the non-Quaternary exposures within the Park. The Chinle Formation unconformably overlies the Lower- Middle Triassic Moenkopi Formation. Although this latter unit is not exposed within PEFO, widespread exposures are present to the west and south in the Little Colorado River Valley.