Silurian Orogeny in the Newfoundland Appalachians

Mapping and U-Pb age studies in the Central Mobile Belt in the southern Newfoundland Appalachians provide new insights into the tectonic evolution of this region. An older limit for the main Paleozoic deformation in the northern Hermitage Flexure is provided by the 466 ± 3 Ma Bay du Nord Group. The regional D1 deformation of Ordovician strata is bracketed by ages of 429 +5/-3 Ma and 415 ± 2 Ma from the synkinematic Burgeo intrusive suite. Two major metamorphic complexes (Port aux Basques complex, Little Passage gneiss), yield 412 ± 2 Ma and 423 +5/-3 Ma ages, respectively; the latter is intruded by the 421 ± 2 Ma synkinematic Gaultois Granite. A 396 +6/-3 Ma granite of the North Bay Granite Suite provides a younger limit for the main regional deformation and peak metamorphism. The La Poile Group, (420 +8/-2 Ma, 424 +7/-3 Ma and 428 ± 6 Ma), the Bear Pond rhyolite (429 +7/-3 Ma), and the Stony Lake volcanics (423 + 3/- 2 Ma), exposed within and north of the Hermitage Flexure, are now documented as products of extensive Silurian subaerial volcanicity and related sedimentation. Coeval magmatic activity is also manifested by the Main Gut gabbro (431 ± 2 Ma) and the Boogie Lake complex (435 +6/-3 Ma). The emplacement of batholiths, penetrative regional deformation and metamorphism, and widespread subaerial volcanicity argue for climactic Silurian orogeny in the Newfoundland Appalachians, synchronous with similar events elsewhere in the northern Appalachians and the Caledonides of Scotland and Scandinavia.