Tate, Richard W , Tomescu, Alexandru MF .
Plant Fossil Diversity in the Late Eocene Clarno Chert of Oregon.
CHERTS of the Clarno Formation (Oregon, USA) comprise a rich assemblage of permineralized vegetative remains and reproductive structures of ferns and seed plants preserved in a subtropical Late Eocene marshland. Studies of Clarno cherts in the mid-20th century, primarily by Arnold and Brown, probed the diversity of the preserved flora, yielding several novel taxa. Despite this, in the period following these early studies the paleobotanical potential of the Clarno Chert has been largely overlooked. A survey of plant remains in a new set of Clarno Chert samples completes the image drawn by earlier studies, allowing for reassessment of botanical diversity in this unit. Rhizomes and petioles of the fern genera Dennstaedtiopsis and Acrostichum are pervasive in the samples; remains of seed-free plants also include Equisetum stems, dispersed filicalean leptosporangia and a fragmentary sporangiate structure. Spermatophytes are represented by diverse seeds and by abundant dicotyledonous twigs and roots, most of which appear to belong to a single species of sapinidalean affinities. The secondary xylem of many of these woody fragments is penetrated by roots of plants that grew on the vegetal material as it was decomposing at the time of fossilization. Missing tissue inside seeds and numerous occurrences of coprolite nests within different vegetative parts provide evidence of pre- and post-burial herbivory and complete the image of interactions in the peat that was fossilized in the cherts. The biotic diversity and quality of preservation of plant fossils highlight the significance of the Clarno Chert for the knowledge of Tertiary floras of western North America, and recommend it for further study.
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1 - Humboldt State University, Department of Biological Sciences, Arcata, California, 95521, USA
Presentation Type: Poster:Posters for Sections
Location: Auditorium/Bell Memorial Union
Date: Tuesday, August 1st, 2006
Time: 12:30 PM