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

The Wild Bight Group and correlative plutonic rocks of the South Lake Igneo us Complex comprise one of the accreted, Ordovician, peri-Gondwanan, oceani c terranes of the Newfoundland Appalachians. Recent field work and isotopic ages from the eastern Wild Bight Group require that the stratigraphic sequ ence be redefined. A package of bimodal volcanic rocks, which forms the old est 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 Explo its Subzone. Previous stratigraphic nomenclature for the upper Wild Bight G roup is largely retained, although the lithological variation within and sp atial distribution of the Omega Point, Seal Bay Brook, and Pennys Brook for mations 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 c ontinental margin. There is a ca. 10 million-year hiatus in volcanic activi ty between the Glovers Harbour Formation and upper Wild Bight Group, althou gh marine sedimentation was likely continuous during this time. This hiatus corresponds with Penobscot deformation and obduction of Exploits Subzone o phiolites onto the Gander Zone farther to the east and south. The Glovers H arbour Formation is correlated with the Tea Arm and Saunders Cove formation s of the Exploits Group, whereas the upper Wild Bight Group can be correlat ed in some detail with the New Bay and Lawrence Head formations. The upper Wild Bight Group and correlative rocks of the Exploits Group are interprete d to represent the arc and back arc, respectively, of the same Middle Ordov ician arc system.