Download Limitations of absolute age constraints for the Quaternary morainal

Limitations of absolute age constraints
for the Quaternary morainal record in the
Eastern Sierra Nevada, California from
detailed stratigraphic relationships
of the Casa Diablo till
Margie B. DeRose
Martin J. Kennedy
Department of Earth Sciences
University of California, Riverside
High Resolution Climate Records
North Atlantic δ18O Records
Marine sediment cores
Greenland ice cores
North Atlantic Marine Sediment
WARM
COLD
Raymo (1994)
3 Million-year δ18O record
Greenland Ice
1
• +120 ka
δ18O record
COLD
Å
WARM
Æ
Steffensen, et al. (2008)
Greenland Ice Core
WARM
COLD
Altabet, et al. (2002)
Rapid Changes
GISP2
Alley, et al.
1993
WARM
↑
COLD
↓
Sierra Nevada
N
rra
Sie
a
ad
ev
http://geon.unavco.org/unavco/lib/images/California_3D_Relief_topography_oblique.jpg
ra
er
Si
v
Ne
a
ad
http://www.goes-arch.noaa.gov/cgi-bin/post-archive
North Atlantic &
Greenland ice records
• Relevance to the Sierran climate record?
North Atlantic &
Greenland ice records
• Relevance to the Sierran climate record?
• Frequency of abrupt change recorded in
the Sierra?
North Atlantic &
Greenland ice records
• Relevance to the Sierran climate record?
• Frequency of abrupt change recorded in
the Sierra?
• Cyclicity and timing of events?
North Atlantic &
Greenland ice records
• Relevance to the Sierran climate record?
• Frequency of abrupt change recorded in
the Sierra?
• Cyclicity and timing of events?
• In phase with the North Atlantic records?
North Atlantic &
Greenland ice records
• Relevance to the Sierran climate record?
• Frequency of abrupt change recorded in
the Sierra?
• Cyclicity and timing of events?
• In phase with the North Atlantic records?
• Stable or unstable?
Å WARM
COLD Æ
Santa Barbara
Basin
ODP Site 893
(Robert, 2004)
Death Valley
(Yang, et al., 2005)
Mono Lake
(Benson et al., 1998)
ra
er
Si
Mono Lake
da
va
Ne
Death Valley
Santa Barbara Basin
ODP 893
http://fermi.jhuapl.
edu/states/maps_
bw/ca_bw.gif
Sierran Climate Record
• Frequency of ice advance in Sierra
– Connection with Northern Hemisphere climate
• Moraines
– Direct record of glacial advance & retreat
Convict Lake
• Photo of Convict Lake & recessional
moraines
(Google™ Earth Image, 2008)
Pine Creek
(Google™ Earth Image, 2008)
Sierran Climate Record
• Chronology for morainal record
– timing, magnitude, & frequency
• Age control
– 14C
• Limited to ~40,000 yr and younger (Walker, 2005)
– Cosmogenic
• Potential error of at least 20% (Walker, 2005)
• Need absolute age control
Mammoth Lakes
www.mapquest.com
Glacial
Geologic Map of the Long Valley Caldera (Bailey, 1989)
Volcanic
Geologic Map of the Long Valley Caldera (Bailey, 1989)
Absolute Age Constraints
• Stratigraphic Relationships
• Only 2 absolute age constraints
– Sherwin till
– Casa Diablo till
• Chronology of Sierran glacial record
Sherwin Till
Bishop Tuff
759 ± 2ka
40K/40Ar
(Sarna-Wojcicki
et al., 2000)
Bishop Tuff
Sherwin Till
HWY 395
Casa Diablo Till
Casa
Diablo
Till
Map:
Bailey (1989)
miles
Casa Diablo Till
Lower
Basalt
126 ± 25 ka
Map:
Bailey (1989)
40K/40Ar
miles
(Bailey, 1976)
Casa Diablo Till
Upper
Basalt
62 ± 13 ka
40K/40Ar
(Bailey, 1976)
Map:
Bailey (1989)
miles
Detailed Mapping
Casa Diablo till
• Address bounding age relationships
• Show relative ages
• Relation to volcanics
• Any new relationships
Preliminary Results
• Lack of evidence for the upper bounding
basalt flow
– No younger age control
• New undocumented relationships
– Potential additional age constraints
• Improve resolution of the Sierran climate
record
Conclusions
• Void in established chronology for the
Sierran glacial record
• Correlation with broader records
• Additional age controls may exist
• Clear need for further detailed studies
• Improve chronology
• Hemispheric teleconnections
Project Support
• Valentine Eastern Sierra Reserve
Graduate Student Research Grant 2008
• White Mountain Research Station
Graduate Student Minigrant 2008
• John Dunham Field Fellowship,
Department of Earth Sciences, University
of California, Riverside 2008