Abstract

Samples of quartzo-feldspathic dikes that were intruded along fractures parallel to the axial planes of folds produced by major deformational events in the eastern Beartooth Mountains were dated by the Rb–Sr whole rock method. Despite relatively large errors associated with the individual dates, it is shown that the second of four recognized fold sets was generated roughly 2750 Ma ago and the third fold set prior to approximately 2565 Ma ago.

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