Laschamp Excursion at Mono Lake?

The Laschamp Geomagnetic Excursion (ca. 41 ka) and a related increase of cosmogenic nuclides provides a global tie point among sedimentary and ice core records. In the Wilson Creek Formation. Mono Lake, California, the Laschamp Excursion has not been recognized although the so-called Mono Lake excursion was found in the section with an estimated age of about 28 ¹⁴C ka. However, our reevaluation of the age of the Mono Lake Excursion at its type locality using new ¹⁴C dates on carbonates and ⁴⁰Ar/³⁹Ar sanidine dates on ash layers yields an estimate of 38-41 ka. This chronology and the absence of a second excursion in the Wilson Creek Formation suggest that the distinct paleomagnetic feature with negative inclinations at Mono Lake is correletive with the Laschamp Excursion.