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 Grenville Province of Ontario
The southeastern Canadian Shield includes deeply eroded segments of the Mesoproterozoic Grenville Orogen – largest collisional mountain belt the world has ever seen. Since 2011, Toby Rivers (Memorial University of Newfoundland) and I have re-examined and jointly analyzed a family of multi-scale transtensional cross-folds and other late-stage extensional structures. Based on the results of this investigation, we have tried to reconstruct the post-convergent geological development of the early-Ottawan thrust-sheet stack (see list of references, below). In June-July of 2018, we will focus special attention on well-exposed subdomain boundary zones in the allochthonous Algonquin domain, and collect mesoscopic structural evidence as to the role of late-Ottawan, post-convergent deformation in shaping these subdomains – possible examples of Grenvillian polygonal mega-boudins. In addition, Toby Rivers, a junior field assistant and I plan to continue our field-based litho-structural study of the rock assemblage representing the Proterozoic Laurentian margin in northeast Ontario: the Parautochthonous Belt of the westernmost Grenville Province. New litho-structural information obtained by our team has not only elucidated the post-convergent deformation of the Proterozoic Laurentian margin, but also aided in refining the trajectory of the Ottawan Allochthon Boundary. In 2018-19, we will continue our field-based study of approximately upright, km-scale cross-folds within the Parautochthonous Belt and the Grenville Front Tectonic Zone, where these folds appear to be attenuated and greatly distorted. In addition, we will also study various inherited mesoscopic fabrics and examine structural features created by Rigolet-phase deformation. Based on the results of this field-based investigation of the Grenville Front Tectonic Zone, we will try to assess the hypothesis that a sizable slice of Ottawan gneiss was cut out by Rigolet faulting at the Grenville Front.
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.