stratigraphy, structure and metamorphism of archean rocks at rainy lake, ontario
abstract
the rocks of the rainy lake area have been deformed
during three distinctive episodes. minor structures provide
the geometry which characterizes each episode. the youngest
structures include regional faults, a crenulation cleavage,
kink bands and minor f[subscript 3] folds. these d[subscript 3] structures are superimposed on structures of the d[subscript 2] episode. these include dominant f[subscript 2] folds having axes lying in a penetrative cleavage which parallels the axial surfaces of the folds. some f[subscript 2]
folds have a downward structural facing which is evidence that the stratigraphic succession at rainy lake is overturned
at a regional scale. it is proposed that this inversion took
place during a d[subscript 1] deformation by the formation of large f[subscript1] fold nappes. minor d[subscript1] structures are difficult to document.
the rocks of the region were metamorphosed simultaneously
with much of the deformation. the distribution of
index minerals defines the boundaries of the biotite,
staurolite-cordierite and sillimanite-muscovite zones. the
non-parallel distribution of metamorphic minerals may be
explained by the non-parallelism of isotherms and isobars
during medium grade metamorphism.
these new data support the view that the coutchiching
biotite schists at rainy lake are stratigraphically
younger than metavolcanic rocks of the keewatin group although
they presently underlie the keewatin structurally. this
observation resolves a part of the historically important
”seine-coutchiching problem”.
collections
- retrospective theses [1604]