Peter Kevin Holmes HBSc thesis abstract

Thesis Title: 
The Structure of Archean Metasedimentary Rocks Near Mosher Lake, Geraldton, Ontario
Peter Kevin

The structure of the Archean metasedimentary rocks of the Beardmore-Geraldton fold belt is investigated.  It has been suggested that two deformational episodes have affected the area near Geraldton.  The F1 folds are recumbent and not seen in outcrop.  An early foliation (S1) is observed in thin section that closely parallels bedding (So).  The dominant folds of the area, called F2, have associated an axial-planar, penetrative cleavage (S2).  This S2 fabric element is subvertical and generally strikes east-west.

The structural facing direction of F2 folds is either upward to the west or downward to the east.  Folds with consistent facing directions are separated by an east-west trending shear zone.

Modification of F2 flexure folds by homogeneous compressive strain, has flattened folds so that they approach the geometry of similar fold styles.  Further modification of fold geometry has occurred due to shear displacements that are typical of the fold belt.  The zone of intense shearing shows how earlier fabric elements have been transposed into the S2 foliation.

The horizontal compressive forces acting from the north and south have produced the east-west trending shear zone and folds of the area.  These crustal forces have affected the well-stratified metasedimentary rocks and are reflected by the structure, observed on all scales.