Resumen de Cretaceous to Tertiary tectono-thermal evolution of the Laurentian margin in Quebec, Canada-Preliminary results -
U. A. Glasmacher, A. López Martínez, A. Tremblay, M. Zentilli, G.A. Wagner, M. Balcazar
In the Canadian Appalachians, the Laurentian margin (i.e. the Humber zone of Williams 1979) is separated into two subzones, external and internal, based on contrasting deformation style and metamorphic intensity. In southern Quebec, the external Humber zone consists of siliciclastic rocks, limestones and mafic volcanic rocks that are deformed into a series of imbricated northwest-directed thrust nappes. Rock units vary from unmetamorphosed to sub-greenschistfacies of metamorphism. Towards the northwest non-deformed Cambrian and Ordovician siliciclastic rocks and limestones of the St. Lawrence Lowlands overlay the Precambrian basement of the Canadian Shield. The Post-Devonian thermo-tectonic evolution of the eastern margin of the Canadian Shield, the St. Lawrence Lowlands and the external Humber zone is only sparsely known. Along the Chaudière River transect (external Humber zone) apatite fission track pooled ages range from 136± 11 Ma to 167 ± I l Ma and along the Montmorency transect (St. Lawrence Lowlands to Canadian Shield) from 122 ± 9 Ma to 156 ±11 Ma. At the Montmorency normal fault the apatite FT-age of the hanging wall is 34 Ma younger than the apatite FT-age of the footwall. This age difference is interpreted in the frame of the development of the St. Lawrence River rift system.
