Late Pleistocene glacier advances in the Ahklun Mountains

3 Questions to consider: 1.What techniques have been used to determine the extent and timing of the LGM in the Ahklun Mountains? 2.How tightly is the timing of the LGM and penultimate advances constrained? 3.What can be done to improve the glacial history of the Ahklun Mountains?

Kaufman and Manley, 2004

Key Chronologies Most glacial chronologies in AK of the last glacial cycle rely on radiocarbon dating, tephrostratigraphy and exposure dating The most robust chronologies in the state are from the Brooks Range, the Alaska Range, and the Ahklun Mountains BR AKR AM

ice cap ice cap

Luminescence-dated lava 70±10 ka, underlies penultimate till Kaufman et al., 2001

Kaufman et al., 2001

intro remarksspatialkey chronologies: BR, AKR, AMsum 1: Age of lava, max constraint on penultimate till 2: Overlying organics are radiocarbon dead 4 36 Cl exposure ages Also, reworks Old Crow Tephra Briner et al., C TL

Sediment core from Arolik Lake Kaufman et al., 2003

36 Cl Age (ka) Lesson: Cosmogenic exposure dating provides timing of moraine stabilization. This is a minimum age for deglaciation. Deposition of glacial lake clay in Arolik Lake Kaufman et al., 2003

LGM advance, ka Penultimate advance, ka