Pollen analysis of death valley sediments deposited between 166 and 114 ka

Abstract

Salt Core DV93–1, from Badwater Basin in California's Death Valley, is a nearly complete sedimentary record of mud and evaporite deposits spanning the past 192 ka. Fossil palynomorph assemblages from core depths of 151.8 m (ca. 166 ka) to 103.5 m (ca. 114 ka) have been analyzed as part of a larger study which will eventually include all of core DV93–1. The palynological analysis discussed here reveals four pollen zones between 151.8 m and 103.5 m. Zone 1, the “Cheno‐Am”; zone (151.8 m to 143.5 m depth, 166–154 ka), has high percentages of Chenopodiaceae/Amaranthus (Cheno‐Am) pollen, and is correlative with the end of marine Oxygen Isotope Stage (OIS) 7. Zone 2, the juniper zone (143.5 m to 117.3 m, 154–124 ka), correlates with OIS 6, as evidenced by high percentages of juniper (Cupressaceae) pollen and low percentages of Ambrosia pollen. Equivalent pollen assemblages are found at higher elevations in Death Valley today, where temperatures are 11° C cooler and rainfall is eight times greater. At the top of Zone 2 (124 ka), a simultaneous drop in juniper and increase in oak (Quercus) pollen occurs, followed by a replacement of Artemisia with Ambrosia in Zone 3, the oak zone. This event corresponds to warming associated with Termination II. The estimated age of this warming event is in agreement with the Termination II event visible in the pollen record from nearby Owens Lake (Litwin et al., 1997). Zone 4, the Asteraceae zone (108.8 m to 103.5 m, 119–115 ka), contains higher percentages of Asteraceae and Cheno‐Am pollen, indicating further warming during this time.