scholarly journals Detailed study of selenium in glacial-lake deposits, wetlands, and biota associated with irrigation drainage in the southern Freezeout Lake area, west-central Montana, 1994-95

1999 ◽  
Keyword(s):  
Glacial Lake ◽  
Lake Area ◽  
West Central ◽  
Central Montana ◽  
Irrigation Drainage ◽  
Lake Deposits

The Age of Glacier Peak Tephra in West-Central Montana

1984 ◽  
Vol 21 (1) ◽  
pp. 36-41 ◽  
Author(s):  
Peter J. Mehringer ◽  
John C. Sheppard ◽  
Franklin F. Foit
Keyword(s):  
Electron Microprobe ◽  
Major Element ◽  
Late Summer ◽  
Volcanic Glass ◽  
Late Glacial ◽  
Major Element Chemistry ◽  
West Central ◽  
Ash Layer ◽  
Central Montana ◽  
Lake Deposits

At Sheep Mountain Bog, near Missoula, Montana, a late-glacial tephra, that probably fell in late summer, is preserved as an 8-mm-thick graded bed overlain by another 8 mm of redeposited ash mixed with lake deposits. Sediment surrounding the ash was 14C dated to about 11,200 yr B.P. Electron-microprobe analyses of the volcanic glass and hornblende phenocrysts from this ash layer indicate that they are similar in major-element chemistry to those of Glacier Peak layer G previously considered to be about 12,000 yr old or older.

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