40Ar/39Ar Laser Dating of Detrital Muscovite from the Teddy Creek Group & Renova Formation, Blacktail Mountains, Montana: Implications for the Tectonic Evolution of the Western Cordillera

Document Type

Grant Proposal

Date Accepted

Spring 2006

Project Description/Abstract

40Ar/39Ar laser age dating of single detrital muscovites from sandstones of the Teddy Creek Group and Renova Formation will be performed to determine their age and the provenance and unroofing history of their source region. Current models speculate sediment was derived from the 60-80 million year old Idaho Batholith, located 100 km to the northwest. An alternative model involves a locally derived source from the 1.8-2.7 billion year old metamorphic rocks of the Blacktail and surrounding ranges. The significant age disparity will easily be resolvable and distinguishable between these two models.

This study will also address the debate of whether high standing topography existed during the time of deposition of the Renova Formation by providing information on the stratigraphic age of the Teddy Creek sandstones. 40Ar/39Ar laser dating will be a powerful tool in unraveling and deciphering the geologic and tectonic evolution of the western Cordillera.

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