Radiocarbon and paleomagnetic chronology of the Searles Lake Formation, San Bernardino County, California, USA

The Searles Lake Formation in Searles Valley, southeastern California, represents deposition of the paleo-Owens River into a Pleistocene and Holocene pluvial terminal lake. A prior 32-10 ka estimated age for the upper part of the Searles Lake Formation relied on uncalibrated, conventional radiocarbon dates. We present accelerator mass spectrometer radiocarbon dates that indicate the base of the Searles Lake Formation at the Poison Canyon type section is 46 ka. That age is consistent with paleomagnetic data at Poison Canyon and the Tire Farm locality, which record high-latitude Southern Hemisphere virtual geomagnetic poles that we assign to the 41 ka Laschamp excursion. The presence of Searles Lake at 46-43 ka also is consistent with a Pacific storm track that extended south of 37.5 degrees N at that time. At the head of Salt Wells Valley-Poison Canyon, sediments that we interpret as a Searles Lake highstand were radiocarbon dated at 14.1 ka.