Late Pleistocene glacier advances

in the Ahklun Mountains

3 Questions to consider:

1. What techniques have been used to determine the extent andtiming 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 theAhklun Mountains?

Kaufman and Manley, 2004

Key Chronologies

• Most glacial chronologies in AK of the last glacial cycle relyon 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

icecap

icecap

Luminescence-datedlava 70±10 ka, underlies

penultimate till

Kaufman et al., 2001

Kaufman et al., 2001

intro remarks spatialkey chronologies: BR, AKR, AM sum

1: Age of lava, max constraint on penultimate till

2: Overlying organics are radiocarbon dead

4 36Cl exposure ages

Also, reworksOld Crow Tephra

Briner et al., 2001

14C

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, 24-22 ka

Penultimate advance, 50-60 ka