SCHORN, HOWARD E., DIANE M. ERWIN, AND PATRICK F. FIELDS.* Museum of Paleontology, University of California, Berkeley, CA 94720, Department of Botany and Plant Pathology, Michigan State University, East Lansing, MI 48824. - Columbia Plateau and Intermountain Basin Neogene floras: Introduction to the Project.
Past interpretations of the Neogene paleobiogeography and paleoclimate
in western North America have generally relied on paleofloras averaged
out over fairly large intervals of time. We are developing a project
in which we look at suites of essentially contemporaneous paleofloras
through time; each suite thus representing a partial "slice"
or "snapshot" of that "moment’s" flora and
vegetation. This approach is a natural step as dating methods become
increasingly improved and larger numbers of paleofloras are dated.
Taxonomic revision of each suite is the fundamental step in the
project. As an example of this approach we compare four 12.5 Ma
megafossil floras distributed from west-central NV, central eastern OR
and southern ID. The more generalized climatic parameters estimated
from the older more time inclusive intervals are in general applicable
to the suite, however, when recognized changes in taxonomic
composition are large enough they do alter earlier climatic
interpretations. Our taxonomic revisions and floral contemporaneity
provide a better understanding about paleobiogeographic relations at
particular "moments" in the Neogene of western North
America. When these isochronous paleofloral assemblages are
considered back within the general temporal framework they provide
specific reference points to anchor the overall evaluation of western
North America's Neogene flora and vegetation.
Key words: Neogene, paleobiogeography, paleobotany, paleoclimatology, paleoecology, taxonomy