AN INVERTED ARCHEAN SUCCESSION AT RAINY LAKE, ONTARIO

The geological history of the Archean rocks at Rainy Lake, Ontario, has been the subject of controversy for over 90 years. Interpretation of new structural data, particularly application of the concept of structural facing, demonstrates that part of the Archean sequence at Rainy Lake was structurally overturned prior to the development of dominant (F//2) folds. This structural revision indicates that, here, Coutchiching metasediments are younger than Keewatin volcanic rocks. Fold-nappe or thrust-nappe tectonics may have been responsible for the pre-F//2 inversion of the stratigraphic sequence. Refs.