LATE-HOLOCENE HYDROCLIMATE INFERENCES FROM LITTLE LAKE, ELKO COUNTY, NEVADA

Prominent lunettes are present on the floor of the Independence Valley, ~35 km southeast of Wells, in Elko County, Nevada. The dunes border the downwind margins of discrete circular playas at the end of “The Slough” descending from the East Humboldt Mountains. The playas are ~500 m in diameter and the dunes consist of curving ridges, 500-800 long, 50-80 m wide, and up to 5 m tall. The two largest lunettes are labeled as “Little Lake” on the Ventosa 7.5’ quadrangle (1980). Gastropod shells are abundant on the playas and in the dune sediments. Shells from the Little Lake playa were radiocarbon dated to 650 and 680 ± 30 years. Similar ages of 610 and 700 ± 30 years were obtained for shells from a depth of ~50 cm below the crests of two different lunettes. All of these ages have calibration ranges overlapping between AD 1250 and 1400. This correspondence, along with the presence of Rosegate Series points on the playa surface, suggests that Little Lake transitioned from a quasi-perennial to ephemeral water body ca. AD 1300, consistent with other evidence for drought in the Great Basin during the Medieval Climate Anomaly. Shells from the crest of a third lunette returned a radiocarbon age of 2170 ± 30 years, which calibrates to between 2.1 and 2.3 ka BP. This age corresponds with a reported late-Holocene dry period in the Great Basin from 1.9 to 2.5 ka BP. Using the Global Surface Water Explorer, 14 years (between 1984 and 2018) were identified in which Little Lake contained water in at least one month. These years are grouped in three clusters: 1984-1987, 1997-2000, and 2017-2018. Statistical analysis reveals that maximum snow water equivalent (SWE) is significantly greater in the mountains, and Palmer Drought Severity Index is significantly lower in the northeastern Nevada climate region, in years when water is present in Little Lake compared with those in which the lake remains dry. Similar results are obtained when considering just years in which water is present in June, the most common month. Average temperature is significantly higher in years when Little Lake fails to form, in contrast to years in which the lake contains water for the majority of the spring and summer. Values of the PDO are also higher, although not significantly (P=0.07), in years when Little Lake holds water. Although the hydrology of Little Lake may be influenced to an unknown degree by water diversions, this overall pattern implies that the lake and its associated lunettes are a sensitive recorder of late Holocene hydroclimate variability in northeastern Nevada.