The Lake Lahontan highstand: age, surficial characteristics, soil development, and regional shoreline correlation

The Lake Lahontan basin has been the site of numerous pluvial lakes during the Pleistocene. We address the question of whether or not the highest remn ant shoreline features around the perimeter of the lake were produced durin g the most recent Sehoo highstand (similar to 13 ka), the penultimate Eetza highstand (similar to 140-280 ka), or both. To do so, we document surficia l characteristics, morphologic preservation, and soil development on multip le Sehoo beach barriers in the Jessup embayment to define the range in char acteristics displayed by latest Pleistocene beach features. Sehoo barriers generally exhibit original constructional morphology that has been little m odified by erosion. Soils developed on Sehoo barriers are generally thin an d weakly developed and an strongly influenced by the introduction of eolian fines into the predominately clast-supported coarse beach gravels. Similar observations from 13 other highstand barriers and from seven older-than-la test Pleistocene paleosols located around the basin form the basis for a re gional comparison. Based on similar characteristics, including the degree o f morphologic preservation and weak soil development, we conclude that the widespread and nearly continuous high shoreline around the perimeter of Lak e Lahontan dates from the most recent major lake cycle in all areas except in the Walker Lake subbasin. In the Walker Lake subbasin, isolated early to middle Pleistocene lacustrine outcrops and landforms are elevated as much as 70 m above the late Pleistocene limit, but are differentiated by their d egraded form and lack of continuity around the subbasin. Similar unambiguou s landforms were not observed elsewhere and at similar elevations in the no rthern subbasins of Lake Lahontan. (C) 1999 Elsevier Science B.V. All right s reserved.