Late Quaternary highstands in the Mud Lake and Big Lost Trough subbasins of Lake Terreton, Idaho

Pleistocene Lake Terreton on the northeastern Snake River Plain, Idaho, contains a record of five episodes of higher effective moisture during the past 160 k.y. Subsurface lacustrine sediments were analyzed from three cores (CB-20, CB-21, CB-23) from the Mud Lake subbasin of Lake Terreton and one (2-2A) from the Big Lost Trough subbasin. Surface sediments were examined in shallow excavations in the North Lake embayment of the Mud Lake basin. The chronology of the sediments is defined by thermoluminescence (TL) and infrared stimulated luminescence (IRSL) age estimates from lacustrine sediment, amino acid racemization age estimates from ostracodes and gastropods, and accelerator mass spectroscopy radiocarbon dates from lacustrine gastropods. Mud Lake cores contain evidence of three highstands during the past 160 k.y. Evidence of highstands includes laminated lacustrine mud, ostracodes, and gastropods. The oldest highstand occurred between ca. 120 and 160 ka, documented by TL and IRSL age estimates ranging from 130 ± 12 ka to 152 ± 13. This highstand correlates broadly with lacustrine sediment in core 2-2A in the Big Lost Trough subbasin, which yielded ostracodes with amino acid ratios consistent with the LittleValley cycle in the Bonneville Basin (ca. 150 ka). Lacustrine sediment from a second highstand yielded luminescence age estimates of 88 ± 7 ka and 84 ± 6 ka. A younger, undated interval of lacustrine sediment may correlate with a ca. 22-11 ka highstand. Surficial lacustrine deposits in the Mud Lake and Big Lost Trough subbasins of Lake Terreton, described in this and previous studies, document two additional highstands (ca. 22-11 ka and after 1 ka).