New exposures of Lava Creek ash more closely constrain the age of the Sacagawea Ridge glaciation, Wind River Mountains, Wyoming (USA)

Abstract Geochemical and 40 Ar/ 39 Ar age analyses of a new exposure of a previously destroyed volcanic ash locality within the Airport Terrace above the Middle Popo Agie River in Lander, Wyoming, allows us to re-establish it as Lava Creek A from the last major eruption of the Yellowstone caldera, with a weighted mean age of 628.2 ± 4.1 ka. Confirmation of the ash as Lava Creek more firmly establishes correlation of the terrace with the WR-7 terraces along the Wind River that contain Lava Creek ash and with outwash correlated to the Sacagawea Ridge type moraine at Dinwoody Lakes. By projecting the Airport Terrace gradient upstream, we show that it grades to the previously mapped terminus of the Sacagawea Ridge valley glacier. Additionally, 10 Be boulder-exposure ages of ca. 521, ca. 554, and ca. 556 ka from Sacagawea Ridge moraines in nearby canyons support more closely constraining the Sacagawea Ridge glaciation here to Marine Oxygen Isotope Stage 16, which corresponds with recent evidence for an advance of the Laurentide Ice Sheet at this time in the U.S. midcontinent.