Detrital Zircon Evidence Requires Revision of Belt Stratigraphy in Southwest Montana.

File(s)
Date
2009-07-23Author
Balgord, Elizabeth A.
Forgette, Michelle M.
MacLaurin, Catherine I.
Advisor(s)
Mahoney, J. Brian
Ihinger, Phillip D.
Metadata
Show full item recordAbstract
The Belt Supergroup was originally named for widespread exposures of thin-bedded red clastic strata in the Big Belt Mountains in southwestern
Montana. Subsequent studies extended the geographic extent and thickness of the Belt Supergroup throughout Montana, Idaho and British Columbia. The nonfossiliferous character of these strata necessitated purely lithostratigraphic correlations. The advent of detrital zircon analyses has provided a method for more rigorous evaluation of proposed correlations. In southwest Montana, the Belt Supergroup consists primarily of thin-bedded, fine-grained sandstone, siltstone and shale of the Spokane, Empire and Greyson Formations. These rocks are overlain by the Middle Cambrian Flathead Sandstone, which is a prominent, cross-stratified medium to coarse
grained quartz arenite that stands in bold relief to the underlying recessive Belt rocks. The contact between these two packages is mapped throughout southwest Montana as a profound unconformity, but recent mapping suggests the contact is actually a conformable, coarsening upward gradational transition.
Subject
Belt Supergroup--Geology
Siltstone--Belt Supergroup
Shale--Belt Supergroup
Sandstone--Belt Supergroup
Siltstone--Montana
Shale--Montana
Sandstone--Montana
Geology, Stratigraphic--Cambrian
Posters
Permanent Link
http://digital.library.wisc.edu/1793/35592Type
Presentation
Description
Color poster with charts and graphs.