Whole rock Rb/Sr age dating near Flin Flon, Manitoba, yields isochrons of 1775 ± 89 m.y. for the Amisk Group (mainly volcanic rocks), and 1805 ± 14 m.y. for the granodioritic Annabel Lake Pluton which intrudes the Amisk. These are considered to be emplacement ages (within their error–limits).A tentative interpretation of the Hudsonian Orogeny in this area is derived by fitting the Rb/Sr ages and previously published K/Ar ages to the sequence of events as determined from detailed structural studies. According to this interpretation, Amisk volcanism began approximately 1865 m.y. ago, and the Hudsonian Orogeny ended approximately 1800 m.y. ago.

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