PALEOMAGNETIC INVESTIGATION OF LAKE LAHONTAN SEDIMENTS AND ITS APPLICATION FOR DATING PLUVIAL EVENTS IN THE NORTHWESTERN GREAT-BASIN

A comparison of paleomagnetic secular variation in sediment of Pleisto cene Lake Lahontan in the northwestern Great Basin with secular variat ion in lake sediment in the Mono Basin, California, indicates that Lak e Lahontan was in the valley of the Truckee River between Pyramid Lake and Wadsworth, Nevada, from about 19,000 to 13,000 yr B.P. The secula r variation in older Lake Lahontan sediment in the Truckee River valle y has the general features of secular variation in middle Pleistocene lacustrine sediments near Rye Patch Dam, Nevada, 125 km to the east. O n the basis of field mapping and tephrochronology, the sections of old er lacustrine sediments are not coeval. The apparent, but erroneous, c orrelation of those sediments emphasizes the need for multiple dating methods when paleomagnetic secular variation is used to date stratigra phy. (C) 1997 University of Washington.