scholarly journals Unravelling contamination signals in biogenic silica oxygen isotope composition: the role of major and trace element geochemistry

2008 ◽  
Vol 23 (4) ◽  
pp. 321-330 ◽  
Author(s):  
Tim S. Brewer ◽  
Melanie J. Leng ◽  
Anson W. Mackay ◽  
Angela L. Lamb ◽  
Jonathan J. Tyler ◽  
...  
Keyword(s):  
Trace Element ◽  
Oxygen Isotope ◽  
Biogenic Silica ◽  
Isotope Composition ◽  
Oxygen Isotope Composition ◽  
Trace Element Geochemistry ◽  
Element Geochemistry

Trace-element geochemistry of individual glass shards of the Old Crow tephra and the age of the Delta glaciation, central Alaska

2003 ◽  
Vol 60 (1) ◽  
pp. 63-69 ◽  
Author(s):  
James E. Begét ◽  
Mary J. Keskinen
Keyword(s):  
Trace Element ◽  
Oxygen Isotope ◽  
Electron Microprobe ◽  
Trace Element Geochemistry ◽  
Ion Microprobe ◽  
Element Geochemistry ◽  
Alaska Range ◽  
East Central ◽  
Oxygen Isotope Stage ◽  
Glass Shards

AbstractTwo widespread tephra deposits constrain the age of the Delta Glaciation in central Alaska. The Old Crow tephra (ca. 140,000 ± 10,000 yr), identified by electron microprobe and ion microprobe analyses of individual glass shards, overlies an outwash terrace coeval with the Delta glaciation. The Sheep Creek tephra (ca. 190,000 yr) is reworked in alluvium of Delta age. The upper and lower limiting tephra dates indicate that the Delta glaciation occurred during marine oxygen isotope stage 6. We hypothesize that glaciers in the Delta River Valley reached their maximum Pleistocene extent during this cold interval because of significant mid-Pleistocene tectonic uplift of the east-central Alaska Range.

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