NPS Paleontology Research Abstract Volume


PLANT MEGAFOSSILS OF THE UPPER TRIASSIC CHINLE FORMATION,
CAPITOL REEF NATIONAL PARK, UTAH

Sidney Ash
Weber State University
Ogden, UT 84408-2507

Plant megafossils occur at many localities in the Chinle Formation of Late Triassic age in Capitol Reef National Park. These localities, which occur at several horizons in the formation ranging from the Shinarump Member at the base to the Owl Rock Member equivalent at the top, contain representatives of most major groups of vascular plants including horsetails, ferns, cycadophytes, conifers, and several taxa of uncertain classification, including Sanmigueia, a fossil that some authors believe is an angiosperm. The Chinle plant fossils are preserved as compressions, impressions, petrifications and pith casts. The flora correlates in general with the classic Chinle flora of northern Arizona and New Mexico. When study of these fossils is completed science will have a better understanding of the plant life and paleoecology of the area during Late Triassic.

Some of the fossils that occur in the park 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 Capitol Reef National Park:

Horsetails

Equsetites sp.

Ferns

Phlebopteris smithii

Cynepteris lasiophora

Cladophlebis sp.

Cycadophytes

Eoginkgoites davidsonii

Zamites powellii

Zamites n. sp.

Conifers

Pagiophyllum sp.

Brachyphyllum sp.

Araucarioxylon arizonicum

Classification uncertain

Sanmiguelia lewisi




THE PRESETTLEMENT VEGETATION OF CAPITOL REEF NP
RECONSTRUCTED WITH FOSSIL PACKRAT MIDDENS

Kenneth L. Cole
NPS - CPSU
115 Green Hall
Department of Forest Resources
University of Minnesota
St. Paul, MN 55108

Norman R. Henderson
Capitol Reef National Park
Torrey, Utah 84775

Plant macrofossils and pollen from twenty five packrat middens were analyzed in order to reconstruct the past vegetation and to analyze vegetation changes occurring since settlement at Capitol Reef National Park. The middens ranged in age from modern to greater than 39,000 years. Eight middens collected from Hartnet Draw in northern Capitol Reef allowed the reconstruction of vegetation over the last 5400 years. Presettlement middens consistently contained fossils of plants now heavily browsed by cattle such as winterfat (Ceratoides lanata), pinyon pine (Pinus edulis), sagebrush (Artemisia tridentata) and rice grass (Oryzopsis hymenoides), none of which are present in a modern packrat midden although some of these plants are present in varying amounts in the modern community. In contrast, the modern sample is the only midden containing specimens of plants typical of overgrazed range such as whitebark rabbitbrush (Chrysothamnus visidiflorus), and greasewood (Sarcobatus vermiculatus), and one of two middens containing snakeweed (Gutterezia sarothrae). The recent grazing impacts precipitated by far the most severe vegetation changes of the last 5000 years.



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United States Department of the Interior, National Park Service