Pollen analyses of sediments from Holes 1019C, 1019E, 1020C, and 1020D as well as piston Core EW9504-17 provide continuous, chronostratigraphically controlled proxy vegetation and climate data for coastal northwest North America for the last ~500 k.y. Systematic changes in the representation of the diagnostic components of northern California plant assemblages clearly show orbital-scale variations. Interglacials are all marked by an abrupt increase in alder followed by expansion of lowland oak woodland and redwood forests. Glacials are dominated by montane forest and woodland assemblages. This sequence reflects large-scale climatic controls (e.g., orbital-scale variation in insolation and Northern Hemisphere ice sheets) in western North America over the last five glacial cycles. Regional climatic control (variations in sea-surface conditions) is implied by the differential development of xeric oak and mesic redwood communities.
1Lyle, M., Koizumi, I., Richter, C., and Moore, T.C., Jr. (Eds.), 2000. Proc. ODP, Sci. Results, 167 [Online]. Available from World Wide Web: <http://www-odp.tamu.edu/publications/167_SR/167sr.htm>. [Cited YYYY-MM-DD]
2Lamont-Doherty Geological Observatory, Columbia Univeristy, Palisades NY 10987, USA. (Present address: Heusser and Heusser, Inc., 100 Clinton Road, Tuxedo NY 10987, USA.) heusser@lamont.ldeo.columbia.edu
3Center for Geophysical Investigation of the Shallow Subsurface, Boise State University, Boise ID 83725, USA.
4College of Ocean and Atmospheric Science, Oregon State University, Corvallis OR 97331, USA.
Date of
initial receipt: 30 September 1998
Date of acceptance: 18 June 1999
Ms 167SR-206