REFINED LATE HOLOCENE LAKE-LEVEL HISTORY OF OWENS LAKE, EAST-CENTRAL CALIFORNIA

The late Holocene lake-level history of Owens Lake has been refined by new geomorphic mapping and stratigraphic studies of previously undated lacustrine and aeolian landforms. We investigated well-developed shorelines (wave-cut notches, beach ridges, and delta bars) that encircle the basin at elevations of 1108, 1103, 1101, and 1099 m. Several complexes of vegetated linear dunes located below the 1108 m shoreline were also studied to decipher the temporal relationship between climatically induced lake-level fluctuations and aeolian deposition.

Radiocarbon (¹⁴C) and infrared stimulated luminescence (IRSL) analyses were used to date shoreline and dune features. Interbedded sandy and gravelly deposits within a beach ridge at 1108 m near Swansea yielded two IRSL ages of 3620 ± 260 and 3490 ± 290 yr B.P. Detrital charcoal sampled in sandy beach rock at the crest of a beach ridge at 1103 m that crosses Carroll Creek yielded a ¹⁴C date of 870 ± 40 yr B.P. [910–700 cal yr B.P.]. Erosional shorelines below 1103 m were dated by employing sediment sampling from hand-augered boreholes at the crests of two parallel dune ridges near Swansea that produced five IRSL ages in morpho-stratigraphic order. The outer dune ridge was sampled to a depth of 4 m and yielded IRSL ages that indicate two episodes of sand accumulation at 760 ± 90 and 410 ± 40 yr B.P. The inner dune ridge was sampled to a depth of 2.5 m and produced two IRSL ages. Alluvium at the base of the section yielded an age of 5000 ± 210 yr B.P. and the age of overlying aeolian deposits indicate sand accumulation at 300 ± 30 yr B.P. The ¹⁴C age of the 1103-m beach ridge is supported by the oldest IRSL age of 820 ± 30 yr B.P. from overlying aeolian deposits that bury its associated lake plain. The age of the 1101 and 1099 m shorelines is bracketed to between 300 ± 30 and 400 ± 30 yr B.P., based on cross-cutting relations with laterally continuous wave-cut notches that only occur on the outer dune ridge.

The new late Holocene ages on shorelines and dune formation correlate well with the timing of regional paleoclimatic variations inferred from other lake basin histories, including the wet period from ~3.8 to 3.2 ka, the Medieval Climatic Anomaly (~1.1 to 0.6 ka), and the Little Ice Age (~0.35 to 0.07 ka).