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Abstract Detail

Paleobotanical Section

Manchester, Steven  [1].

Leaves from the Eocene Clarno Nut Beds flora, Wheeler County, Oregon.

Eocene leaf floras in Oregon have played an important role in understanding floristic and climatic change in the Pacific Northwest.  However, in contrast with Oligocene and younger floras of the region, the Eocene floras have received relatively little taxonomic study and most of the constituent species have never been illustrated or described. Eocene floras contain a greater proportion of unfamiliar elements due to the combined effects of extinction and changes in geographic range that have occurred since the time that those plants were growing. Although best known for its assemblages of silicified woods, fruits and seeds, the Clarno Formation in northcentral Oregon is also rich in fossil leaves.  The leaf flora is useful for inferring climate from a physiognomic perspective, and for taxonomic comparisons with fossil floras other regions where well-preserved fruits, seeds and woods are not available. Analysis of leaf impressions from siltstones of the Clarno Nut Beds site, in the Clarno Unit of John Day Fossil Beds National Monument, augments prior investigations of reproductive organs and wood.  The leaf flora includes ferns, extinct cycads (Eostangeria, Dioonopsis and Ctenis), Ginkgo, palms, and numerous kinds of dicotyledonous leaves, including Platanaceae (Macginitiea), Fagaceae (Quercus), Ticodendraceae (cf Ticodendron), Juglandaceae (cf. Juglans), Sabiaceae (Meliosma), Menispermaceae spp., and Lauraceae spp.  Approximately 52% of the 63 dicotyledonous species have entire-margined leaves, leading to an estimated mean annual temperature of about 17°C.  Compared to more northerly Eocene floras, the Nut Beds flora is poor in conifer diversity, and has larger leaves.  Compared to floras of similar age in eastern North America, the Nut Beds flora is poor in diversity of Leguminosae and Theaceae.

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1 - University of Florida, Florida Museum of Natural History, PO Box 117800, Gainesville, FL, 32611, USA

none specified

Presentation Type: Oral Paper:Papers for Sections
Session: 37
Location: Pines North/Boise Centre
Date: Wednesday, July 30th, 2014
Time: 9:00 AM
Number: 37003
Abstract ID:689
Candidate for Awards:None

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