FOLLOWING THE STEPS OF SANDRA BARR: MY WORK IN THE CANADIAN APPALACHIANS

In their seminal paper on the geology of Cape Breton Island and the Canadian Appalachians, Barr and Raeside (1989, Geology, v. 17, p. 822–825) divided the island into four terranes and proposed that the Eastern Highlands shear zone is the boundary between the Bras d’Or and Aspy terranes. At their invitation, I worked on the shear zone and the relationship between the two terranes for my PhD thesis, under the supervision of Paul Williams. Following that, I worked on southwestern Newfoundland and its correlation with Cape Breton Island for my post-doctoral research with Cees van Staal. Our main conclusions include the following:

• The Aspy terrane is the remnants of a Japan-type arc--back-arc system along the Bras d’Or (Ganderian) continental margin. In this model, the arc had a continental basement that rifted away from the Bras d’Or terrane during the back-arc opening (Lin, 1993, Canadian Journal of Earth Sciences, v. 30, p. 1773-1781).
• The Eastern Highlands shear zone is a major Silurian shear zone with a sinistral SE-over-NW sense of shear. Movement along the shear zone led to major differential uplift in the hanging wall (Lin, 2001, Journal of Structural Geology, v. 23, p. 1031-1042), as indicated by the Al-in-hornblende pressure data of Farrow and Barr (1992, Canadian Mineralogist, v. 30, p. 377-392).
• Cape Breton Island and southwestern Newfoundland were the location of Silurian collision between the St. Lawrence promontory on the Laurentian margin and the Cabot promontory on the Ganderian margin (Lin et al., 1994, Geology, v. 22, p. 897-900). The model explains the observations that in this part of the Canadian Appalachians, the orogen is much narrower, the deformation is stronger, the grade and pressure of metamorphism are much higher, and the Silurian orogen-parallel thrusts are dominantly west-vergent, antithetic to the westward subduction.
• Orogen-parallel strike-strip motion may have played a significant role in the evolution of the Appalachian-Caledonian orogen (Lin et al., 2013, Geological Society of America Bulletin, v. 125, p. 1618-1632).

My next goal on the Canadian Appalachians is to finish a study on St. Paul Island, a project I started with Sandra Barr about 30 years ago!