Fried Schwerdtner (Emeritus)
University of Toronto
Department of Earth Sciences
22 Russell Str. Toronto
Ontario, Canada M5S 3B1
Tel.: 416 978 5080
Fax.: 416 978 3938
Post-convergent structures in the western Grenville Province (Ontario)
The eastern Canadian Shield contains deeply eroded segments of the Mesoproterozoic Grenville Orogen – largest collisional mountain belt the world has ever seen. The relict orogen is particularly well exposed in central and southeast Ontario. Here, my coworkers and I have addressed problems of structural geology for many years, both in the field and various research laboratories. Since 2011, I have been collaborating closely with Toby Rivers, Department of Earth Sciences, Memorial University of Newfoundland, and his research associates. In the field, we have investigated macroscopic and mesoscopic structures apparently formed under conditions of orogenic collapse, and tried to reconstruct the post-convergent geological development of the Central Gneiss Belt (for details, see Schwerdtner et al. 2014, Can. J. Earth Sci. 51: 243-265; Rivers and Schwerdtner 2015, Geoscience Canada, 42: 403-436). In 2016-17, Toby Rivers and I studied the re-deformed rocks of the Proterozoic Laurentian margin, also known as the Parautochthonous Belt of the Grenville Province. Taking advantage of geological maps published by the Ontario Geological Survey, we collected detailed structural and petrological evidence in closely-spaced road cuts of the greater Mattawa-North Bay and Britt-Noëlville-Commanda regions. The new geological information thus obtained not only elucidates the post-convergent deformation of the Laurentian margin, but also aids in approximating the trace of the Allochthon Boundary Thrust of the Ottawan Orogen, western Grenville Province. Starting in 2014, special attention has been focused on the structural origin of multi-order cross-folds, which dominate the geological map pattern at the reworked continental margin of the northern Georgian Bay region. We have hypothesized that these cross-folds formed in a post-convergent regime of left-lateral ductile transtension (Schwerdtner et al. 2016), but would like to find additional field evidence for a regional component of orogen-parallel shearing. This will continue to be a principal objective in our research program for 2018-19. In addition, we focus special attention on well-exposed subdomain boundary zones of the Algonquin domain, and collect mesoscopic structural evidence as to the role of post-convergent deformation in creating the subdomains − possible examples of Grenvillian polygonal mega-boudins.
Schwerdtner, W.M., Rivers, T., Tsolas, J., Waddington, D.H., Page, S., and Jang, J. 2016. Transtensional origin of multi-order cross-folds in a high-grade gneiss complex, south- western Grenville Province: formation during postpeak gravitational collapse. Canadian Journal of Earth Sciences, 53: 1511-1538.
Rivers, T. and Schwerdtner, W.M. 2015. Post-peak evolution of the Muskoka Domain, western Grenville Province: ductile detachment zone in a crustal-scale metamorphic core complex. Geoscience Canada, 42: 403-436.
Schwerdtner, W.M.,Rivers, T., Zeeman, B., Wang, C.C., Tsolas, J., Yang, J., and Ahmed, M. 2014. Post-convergent structures in lower parts of the 1090-1050 Ma (early Ottawan) thrust-sheet stack, Grenville Province of Ontario, southern Canadian Shield. Canadian Journal of Earth Sciences, 51 243-265
Schwerdtner, W.M. 2013. Photograph of the month. Journal of Structural Geology, 48 (October issue): 1-2.
Schwerdtner, W.M. and Yang, J.F. 2011. Photograph of the Month: Pseudotachylite at the basal contact of the Parry Sound allochthon, Grenville Province of Ontario, Canada. Journal of Structural Geology, 33: 1714.
Schwerdtner, W.M., Lu, S. J. and Yang, J.F., 2010. Wall-rock structure at the present contact surfaces between repeatedly deformed thrust sheets, Grenville Orogen of central Ontario, Canada. Canadian Journal of Earth Sciences, 47: 875-899.
Schwerdtner, W.M., Lu, S.J. and Landa, D., 2010. S/Z buckle folds as shear-sense indicators in the ductile realm: Field examples from the Grenville Province of Ontario and the Appalachians of South Carolina. In ‘From Rodinia to Pangea: The Litho- tectonic record of the Applachian Region, Geological Society of America Memoir 206, Chapter 30, p. 773-794.
Schwerdtner, W.M. and Klemens, W.P., 2008. Structure of the Ahmic domain and its vicinity, southwestern Central Gneiss Belt, Grenville Province of Ontario (Canada). Precambrian Research, 167: 16 – 34.
Schwerdtner, W.M., Riller, U.P. and Borowik, A., 2005. Structural testing of tectonic
hypotheses by field-based analysis of distributed tangential shear: examples from major high-strain zones in the Grenville Province and other parts of the Canadian Shield. Canadian Journal of Earth Sciences, 42: 1927 – 1947.
Schwerdtner, W.M., Downey, M.W. and Alexander, S.A., 2004. L-S shape fabrics in the Mazinaw domain and the issue of NW-directed thrusting in the Composite Arc Belt, southeastern Ontario. Geological Society of America, Memoir 197, p. 183 – 2008.
Rivers, T. and Schwerdtner, W.M. 2014. New ideas on the post-peak development of the Central Gneiss Belt in the Muskoka Region. Field trip guide, Friends of the Grenville weekend in Gravenhurst, Ontario; October 3-5, 2014.
Schwerdtner, W.M., Robin, P.-Y. F., Alexander, S., Burke, J., Downey, M.W., and Serafini, G., 2003. Connection between Grenvillian deformation and granitoid pluton emplacement in the Composite arc Belt (Tweed-Kaladar area), southestern Ontario, Canada. Guidebook for Friends of the Grenville (Amis du Grenville) field trip, Department of Geology, University of Toronto.
Schwerdtner, W.M., Klemens, W.P., Robin, P.-Y. F., Vertolli. V.M., and Waddington, D.H., 2005. Geological structure and lithology in parts of the Muskoka region, southwestern Central Gneiss Belt, Grenville Province of Ontario. Field trip guide, 25th annual workshop of the Canadian Tectonics Group and Structural Geology-Tectonics Division of the Geological Association of Canada, Department of Geology, University of Toronto.
Schwerdtner, W.M., Dickin, A.P. and Robin, P.-Y. F., 2009. Rocks, structures and tectonic scenarios: Introduction to the Grenville Province of Ontario. Guidebook for a pre-sessions field trip (Geological Association of Canada), Joint Assembly (AGU- GAC-MAC Meeting), Department of Geology, University of Toronto.