Late Pleistocene glacier advances

1. Late Pleistocene glacier advances in the Ahklun Mountains

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

3. Kaufman and Manley, 2004

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

29. ice cap ice cap

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

33. Kaufman et al., 2001

34. intro remarks key chronologies:BR, AKR, AM spatial sum 4 36Cl exposure ages TL 1: Age of lava, max constraint on penultimate till 2: Overlying organics are radiocarbon dead 14C Also, reworks Old Crow Tephra Briner et al., 2001

41. Sediment core from Arolik Lake Kaufman et al., 2003

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

44. LGM advance, 24-22 ka Penultimate advance, 50-60 ka