Abstract

The well-developed shoreline record of pluvial Lake Lahontan in the Jessup embayment, Nevada, is used to refine the history of late Pleistocene lake-level fluctuations and to assess controls on shoreline development and distribution. Controls on the strength and type of shorelines developed include local slope, the amount and characteristics of sediment available for transport, the availability of accommodation space, and length of time the lake level resides at a particular shoreline elevation. At the Sehoo highstand and during the early part of the regression, strong storm winds and waves from the south-southeast set up a clockwise net shore-drift pattern near the head of the embayment. Although significant differences in local slope, geometry of the shoreline, and wave energy existed in the embayment, crestal heights of constructional shoreline features formed at the highstand vary <2.6 m in elevation and hence provide a relatively precise marker of the highstand elevation.

Radiocarbon dating of a camel bone preserved in high shoreline deposits indicates that the lake reached its highest elevation of 1338.5 m in the embayment and receded from that elevation immediately prior to 13 070 ± 60 yr B.P. Similar and slightly older radiocarbon ages on gastropod shells preserved in barrier deposits at 1327 m (13 280 ± 110 yr B.P.) and 1331 m (13 110 ± 110 yr B.P.) suggest that the final rise to the highstand was very rapid and that the lake maintained its highest stand for a very brief period of time, perhaps only for years or decades. The brevity of the highstand is reasonable in light of the recent formation of similar barrier features in modern Pyramid Lake, which formed in less than seven months due to a rapid increase in lake level.

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