Redefinition of the Wild Bight Group, Newfoundland: implications for models of island-arc evolution in the Exploits Subzone

• Published in: Canadian Journal of Earth Sciences
• Main Authors: MacLachlan, Kate, O'Brien, Brian H, Dunning, Greg R
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 2001
• Subjects: General Earth and Planetary Sciences; Saunders; Wild Bight; Seal Bay; Omega Point; Pennys Brook; Newfoundland
• Online Access: http://dx.doi.org/10.1139/e01-006; http://www.nrcresearchpress.com/doi/pdf/10.1139/e01-006

The Wild Bight Group and correlative plutonic rocks of the South Lake Igneous Complex comprise one of the accreted, Ordovician, peri-Gondwanan, oceanic terranes of the Newfoundland Appalachians. Recent field work and isotopic ages from the eastern Wild Bight Group require that the stratigraphic sequence be redefined. A package of bimodal volcanic rocks, which forms the oldest part of the group and contains all of its volcanogenic massive sulphide deposits, is redefined as the Glovers Harbour Formation. This formation is correlative with intra-oceanic ophiolitic sequences elsewhere in the Exploits Subzone. Previous stratigraphic nomenclature for the upper Wild Bight Group is largely retained, although the lithological variation within and spatial distribution of the Omega Point, Seal Bay Brook, and Pennys Brook formations are revised, and the Side Harbour Formation is included as part of the Seal Bay Brook Formation. The upper Wild Bight Group is interpreted to represent a second and distinct arc sequence that formed on the Gondwanan continental margin. There is a ca. 10 million-year hiatus in volcanic activity between the Glovers Harbour Formation and upper Wild Bight Group, although marine sedimentation was likely continuous during this time. This hiatus corresponds with Penobscot deformation and obduction of Exploits Subzone ophiolites onto the Gander Zone farther to the east and south. The Glovers Harbour Formation is correlated with the Tea Arm and Saunders Cove formations of the Exploits Group, whereas the upper Wild Bight Group can be correlated in some detail with the New Bay and Lawrence Head formations. The upper Wild Bight Group and correlative rocks of the Exploits Group are interpreted to represent the arc and back arc, respectively, of the same Middle Ordovician arc system.