late pleistocene glacier advances
DESCRIPTION
Late Pleistocene glacier advances. in the Ahklun Mountains. 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? - PowerPoint PPT PresentationTRANSCRIPT
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