WHEELER, ELISABETH A.* AND STEVEN R. MANCHESTER. Department of Wood and Paper Science, North Carolina State University, Raleigh, NC 27695-8005; Florida Museum of Natural History, University of Florida, Gainesville, FL 32611. - Survey of the diverse middle Eocene wood assemblage of the Clarno Formation, northcentral Oregon.
A diverse assemblage of silicified woods occurs in the type area of
the Clarno Formation in north central Oregon, USA. These woods occur
as predepositionally abraded fragments along with abundant fruits and
seeds in tuffaceous sediments at the Nut Beds locality in the Clarno
Unit of John Day Fossil Beds National Monument. A comprehensive
investigation of these woods, involving the thin-sectioning and
analysis of more than 500 specimens, has resulted in the recognition
of about 70 distinct taxa--making it the richest Eocene wood
assemblage so far known. Although the diversity of woods at the Nut
Beds apparently is not as high as that of fruits and seeds (ca 175
species), the woods document some new families for the flora and
provide improved insight into the composition of this thermophilic
assemblage. At least fifty of Nut Beds wood types are referable to
extant family. Among these, some have anatomy diagnostic of
particular modern genera (e.g., Alangium, Meliosma, Prunus);
others represent extinct genera (e.g.,
Clarnoxylon--Juglandaceae, Triplochitioxylon--Malvaceae
s.l.); but most are stereotypic genera, i.e., cannot be assigned to an
extant genus because their combination of features occurs in more than
one extant genus (e.g., Magnoliaceoxylon, Maloidoxylon). We
recognize the following families based on woods from the Nut Beds:
Aceraceae, Anacardiaceae, Annonaceae, Araliaceae, Betulaceae,
Cercidiphyllaceae, Cornaceae, Eupteleaceae, Fagaceae, Flacourtiaceae,
Hamamelidaceae, Juglandaceae, Lauraceae, Leguminosae, Magnoliaceae,
Malvaceae, Moraceae, Platanaceae, Rosaceae, Sabiaceae, Sapindaceae,
Ulmaceae, Vitaceae, Palmae, Ginkgoaceae, Pinaceae, Taxodiaceae.
Key words: Clarno Formation, Eocene, fossil wood, paleobotany, Tertiary, wood anatomy