Age and magnitude of dip-slip faulting deduced from differential cooling histories: an example from the Hope Fault, northwest Montana

J. A. Fillipone, Yin An Yin, T. M. Harrison, G. Gehrels, M. Smith, J. C. Sample

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Abstract

A new method is described in which the age and magnitude of dip-slip faulting are estimated from contrasting cooling histories of footwall and hanging wall rocks adjacent to the Hope fault, northwest Montana. The Hope fault has been interpreted in the past as a mostly right-slip fault. New kinematic data, 40Ar/39Ar thermochronometry, and geobarometry indicate that cooling of footwall rocks at ~40 Ma resulted from dip-slip movement. This movement caused vertical separation of about 3 to 5 km between footwall and hanging wall rocks, suggesting that a minimum dip-slip component of 4 km developed during the Late Eocene. These results indicate that the Hope fault experienced substantial normal slip in the Late Eocene, making it coeval with other normal and detachment-style faults in the northern US Cordillera. -from Authors

Original languageEnglish (US)
Pages (from-to)199-211
Number of pages13
JournalJournal of Geology
Volume103
Issue number2
DOIs
StatePublished - Jan 1 1995

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ASJC Scopus subject areas

  • Geology

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