Sam Tyler

            A collection of structural, lithological, and geophysical data is used to estimate the location and nature of the southern boundary of the Nepewassi domain of the Central Gneiss Belt, Grenville Province.  Field mapping of a teardrop-shaped structure on the West Bay of Lake Nipissing, Ontario was performed.  Structural data acquired during field work was added to Lumbers’ 1970 Burwash East map.  The structural nature of the ‘teardrop’ structure and its surroundings suggest a complex history of deformation.  High strain, ductile Grenvillian deformation (D1) is responsible for L-S foliation defined by mineral grain orientation and overturned folds (F1).  A second, post-1235 Ma phase of deformation (D2) is responsible for the formation of gently plunging, upright ESE folds (F2) which overprinted D1 fabrics and F1 folds to form type 1 transitional to type 2 (“teardrop”) and type 3 interference patterns (folding west of “teardrop”).  A boundary in which the Britt domain overthrusts the Nepewassi to the north is suggested to extend E from the Cosby batholiths.  Possible scenarios for relative event timing are suggested:  post-1235 Ma D2 deformation followed by emplacement of the Britt, or, emplacement followed by and possible resulting in D2 deformation.

Keywords: Grenville Province; Grenville Orogeny; Central Gneiss Belt; Britt Domain; Nepewassi Domain; Lake Nipissing; Lavigne (ON); Fold superposition; Thrust belts; North American tectonic history
Pages: 29
Supervisor: Nicholas Culshaw