Walfried Schwerdtner

Field-based structural geology of heterogeneously deformed orthogneisses and associated metamorphic rocks, westernmost Grenville Province (Ontario)

Since 2011, Toby Rivers, Fried Schwerdtner and Dennis Waddington have undertaken detailed litho-structural work in the Grenville Province of Ontario, based mainly on careful examination of roadcuts and other clean rock-exposures. After studying a variety of geological problems in the Grenville gneiss terrain of central Ontario and adjacent parts of the Sudbury and North Bay regions (see paper by Rivers and Schwerdtner 2024, Can. J. Earth Sci., 6: 894 – 940), their main interest turned to the Central Metasedimentary Belt (CMB) of southeast Ontario, in the early summer of 2024. Here, Fried Schwerdtner, Dennis Waddington and Amaru Izarra-Jacome (junior field assistant) examined meso-structural features in the Harvey-Cardiff region, western Bancroft area (Fig. 1; Schwerdtner et al. 2024. In Program with Abstracts: Antigonish 2024, Workshop of the Canadian Tectonics Group, p. 13).

In the coming summer, special attention will be paid to the mesoscopic structural geology of metasedimentary marbles containing metamorphosed and dismembered siliceous layers. Two research foci were identified in 2024-2025: (1) Structural styles of ductile-brittle deformation of siliceous and mafic layers in highly strained marble units and (2) Paleo-kinematic evolution of tadpole-shaped structures, relics of siliceous or mafic layers in highly strained marble units. Main research targets: Clean road-cuts exposing thick marble units in the Bancroft, Carnarvon, Minden and Northbrook regions.   

Figure 1

Fig. 1: Geological sketch map of the western Grenville Province of southeastern Ontario showing four of the five granitoid complexes (grey ‘islands’) called ‘domes’ in the legend, Harvey-Cardiff domain (neither indicated nor labeled on the sketch map). From NE to SW, these grey ‘islands’ are the Cardiff, Cheddar, Anstruther and Burleigh granitoid complexes; the northeastern-most (Faraday) complex is not shown. BSZ = Bancroft shear zone, CMBbz = Central Metasedimentary Belt boundary zone. Small squares indicate rock-sampling locations in earlier geoscientific studies of the CMBbz and/or the Harvey-Cardiff domain. Map image courtesy of Michelle J. Markley, Mount Holyoke College, Massachusetts.

Figure 2

Fig. 2: Fragments of paragneiss and amphibolite in banded marble, Haliburton area, Ontario

Figure 3

Fig. 3: Folded and fragmented layers of paragneiss and amphibolite in white marble, Minden area, Ontario. Bottom: Blue cap of field assistant for scale.

Figure 4

Fig. 4: Folded and fragmented layers of paragneiss and amphibolite in a matrix of white marble, Gravenhurst area, Ontario. The diameter of the large amphibolite piece at the right upper corner is about 20cm.

Recent Publications

A. Research Papers in Refereed Journals

Rivers, T. and Schwerdtner, W.M. 2024. The Ottawa River Gneiss Complex revisited: Formation of the metamorphic core and detachment zone of a large Grenvillian metamorphic core complex. Canadian Journal of Earth Sciences. Vol 61, No. 9, pp. 894-940.

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.

B. Nonrefereed publications

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.

C. Recently published Abstracts

(1) 2020 Annual GSA Meeting, Montréal QC

Carter et al. 2020. Abstract 71-12: RETROGRESSED BANDED GNEISSES AS INDICATORS OF INVERTED DUCTILE THRUSTS, WESTERN OTTAWA RIVER GNEISS COMPLEX, GRENVILLE PROVINCE OF ONTARIO). Geological Society of America Abstracts with Programs. Vol 52, No. 6, 2020; doi: 10.1130/abs/2020AM-352187 https://gsa.confex.com/gsa/2020AM/meetingapp.cgi/Paper/352187

Schwerdtner et al. 2020. doi: 10.1130/abs/2020AM-352984https://gsa.confex.com/gsa/2020AM/meetingapp.cgi/Paper/352984

2. 2021 GAC-MAC Meeting, London ON

Schwerdtner and Rivers 2021, GAC-MAC Meeting London ON, Abstracts Volume 44, p. 271, 272

Waddington and Schwerdtner 2021, GAC-MAC Meeting London ON, Abstracts Volume 44, p. 302

3. 2022 GAC-MAC Meeting, Halifax NC

Schwerdtner & Cowan 2022, GAC-MAC Meeting, Abstracts Volume 45, p. 197

4. 2023 GAC-MAC Meeting, Sudbury ON

Schwerdtner, W.M., Waddington, D.H., Liu, Lingfei and Yiu, Fannie. 2023, GAC-MAC Meeting, Sudbury ON, Abstract Volume 46

5. 2024 Workshop of the Canadian Tectonics Group (CTG, an MAC Division), Antigonish NS

Schwerdtner et al. 2024, Programs with Abstracts, p. 13.