NPS Paleontology Research Abstract Volume


PLANT MEGAFOSSILS OF THE UPPER TRIASSIC CHINLE FORMATION,
CANYON DE CHELLY NATIONAL MONUMENT, ARIZONA

Sidney Ash
Weber State University
Ogden, UT 84408-2507

Although Canyon de Chelly National Monument is most famous for the Indian cliff dwellings found within its boundaries, it also includes several localities that contain plant megafossils. These fossils are found in the Chinle Formation of Late Triassic age. Interestingly, the first Triassic plant fossils to be collected from Arizona were found in the Monument in 1849. The work which has been accomplished thus far shows that plant megafossils occur at several horizons in the lower part of the formation in the Shinarump and Monitor Butte Members. The flora is comparatively small and include representatives of only the lycopods, cycadophytes, conifers, and several taxa of uncertain classification. The most interesting form in the flora is Dechellyia, a fossil which combines features that usually occur in separate groups. The Chinle plant fossils are preserved as compressions, impressions, and petrifications. In general, the flora correlates with the classic Chinle flora of Petrified Forest National Park and northwestern New Mexico. Several of the fossils that occur in the Monument have either been described or mentioned in the literature but no complete study of the flora has yet been published. At this time the following plant megafossils have been recognized in the Chinle Formation in Canyon de Chelly National Monument:

Lycopods

Seleginella anasazia

Conifers

Masculostrobus clathratus

Araucarioxylon arizonicum

Pelourdea sp.

Dechellyia gormanii

Dinophyton spinosus



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