MYERS, JEFFREY A. Department of Earth and Physical Sciences, Western Oregon University, Monmouth, OR 97361. - Unique vegetation from the Eocene Cordilleran uplands.
The ~38-35 Ma Cedarville Flora, NE California, is a unique
leaf-dominated impression flora intermediate between
"Boreotropical" Paleogene vegetation and
Metasequoia-dominated "Arctotertiary" vegetation of the
early Oligocene Northwest. The assemblage grew at ~1000 m
paleoelevation on the seaward slope of the Paleogene Cordillera, in
biogeographic connection with both upland interior and lowland coastal
vegetational sources. Cedarville evergreen broadleaved taxa (eg.
Annonaceae, Magnolia, Meliosma, Quercus, Schizandra) while not
diverse, closely resemble species from Eocene Oak-Laurel vegetation of
the Northwest lowlands. Deciduous broadleaved taxa (eg. Alnus,
Cedrelospermum, Cercidiphyllum, Decodon, Parrotia, Plafkeria, Platanus
exaspera, Pterocarya, Ulmus) are conspecific with or similar to taxa
from the latest Eocene Florissant Flora, Colorado, and Oligocene
Bridge Creek Flora, central Oregon. With the exception of Rosaceae
(seven species) however, diverse "Arctotertiary" lineages
that distinguish Bridge Creek-type assemblages (eg. Aceraceae,
Betulaceae, Tiliaceae, etc.) are absent or represented by one species
in the Cedarville Flora. At Cedarville, the combination of moderate
elevation and maritime climate (cool summers, moderate winters, and
copious, non-seasonal precipitation) permitted the intergradation of
"Boreotropical" lineages from lowland coastal vegetation and
"Arctotertiary" lineages from the interior Cordillera. The
Cedarville Flora documents both the early westward migration of
seasonally-adapted microthermal lineages, and the adaptation of
megathermal "Boreotropical" lineages to increasingly cool
and seasonal climate.
Key words: Cedarville, Cordillera, Eocene, paleobotany, paleoclimate