Wetlands Levee Coring

SUMMER LAKE BASIN, SOUTH-CENTRAL OREGON, U.S.A.

The Summer Lake Basin of south-central Oregon has been a source of scientific interest since the early part of the last century. In the middle 1980s a new episode of research began that still continues. In the middle 1980s the late Dr. Jonathan Davis began investigating the many volcanic ashes in the exposures along the Ana River at the north end of the basin. At his instigation a group of scientists from California State University, Bakersfield (paleomagnetist, Rob Negrini), University of Arizona (ostracode specialist, Andrew Cohen), and the Desert Research Institute (paleoecologists, Lonnie Pippin and Peter Wigand) sampled the Ana River exposures and started a program of coring that followed up on some that had been conducted by Dr. Dave Adam of the U.S.Geological Survey at the southern end of the basin.

In addition, to samples collected along the Ana River which reveal strong correspondences (especially prior to the last interglacial) between local vegetation history and the oceanic O18 record (a reflection of global temperature), cores were taken at three other localities. Two of these, Wetlands Levee and the Bed & Breakfast localities, have now been analyzed and will shortly appear in publication. The one hundred-foot core obtained from Wetlands Levee in the west-central part of Summer Lake, south-central Oregon, covers the last 94,000 years. Its record is providing a unique comparison of the response of lake chemistry, and aquatic and terrestrial vegetation to climates since the last interglacial. Ratios of pollen, spores and algae from the Wetlands Levee core and the Bed and Breakfast core reveal not only periods of colder climate associated with glacial advances, but also episodes of significant drought such as that around 30,000 years ago. The information recovered here mirrors that recovered 250 km to the southeast where much larger lakes existed.

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