A full-vector paleomagnetic secular variation record (PSV) from Pyramid Lake (Nevada) from 47-17 ka: Evidence for the successive Mono Lake and Laschamp Excursions

- This paper develops a full-vector paleomagnetic secular variation (PSV) record for Pyramid Lake, Nevada for 17-47 ka.
- This PSV record is dated by three methods, radiocarbon dating, correlation to dated ashes, correlation to dates PSV features.
- This PSV record contains the Mono Lake Excursion (∼34.5 ka) and the Laschamp Excursion (∼40.5 ka).

We have carried out a paleomagnetic study of late-Pleistocene Pyramid Lake core PLC08-1 (1680 cm). Our goals were to develop a full-vector paleomagnetic secular variation (PSV) record for the core, establish a paleomagnetic chronostratigraphy for the lake based on correlation of the PSV record to other dated PSV records in the region, compare that chronostratigraphy with previously developed radiocarbon and ash chronologies, and search for evidence of the Mono Lake Excursion and Laschamp Excursion. We have recovered a full-vector PSV record (inclination, declination, relative paleointensity) for the interval 47 ka to 17 ka. Twenty radiocarbon dates and four dated ashes provided a chronostratigraphic framework for this record. We have also used the link between our PSV and other dated PSV records to develop an independent PSV chronostratigraphy for the core. The PSV chronostratigraphy is not significantly different from that estimated by the radiocarbon and ash chronologies. We note the existence of two intervals of anomalous paleomagnetic directions. The younger interval, centered at 34.1±0.4 ka, has the characteristic vector component features of the Mono Lake Excursion. The older interval, centered at 40.9±0.5 ka, has the characteristic paleomagnetic signature of the Laschamp Excursion. This is the first time both intervals of excursional behavior have been found in the same sediment record from the western USA. Our new PSV record also corroborates previous estimates of the Mono Lake Excursion directional field behavior (Liddicoat and Coe, 1979) and age (Benson et al., 2003).