THE NOGGIN COVE FORMATION - A MIDDLE ORDOVICIAN BACK-ARC BASIN DEPOSIT IN NORTHEASTERN NEWFOUNDLAND

The Noggin Cove Formation is the largest volcanic unit of the eastern Exploits Subzone. It is approximately 1 km thick and consists mainly o f stratified mafic volcaniclastic rocks with subordinate pillowed basa lt and black share. Stratigraphic relationships and regional correlati ons indicate a Middle Ordovician age. The Carmanville Melange and the distinctive Woody Island formation, with coticule layers and olistostr omes, occur along the northern margin of the Noggin Cove Formation, an d the formation is faulted against siltstone and shale of the Davidsvi lle Group along its southern margin. The Noggin Cove Formation underwe nt three periods of deformation: (1) D-1, early recumbent F-1 folding; (2) D-2, northeast-trending tight to isoclinal F-2 folding with perva sive axial planar cleavage (S-2); and (3) D-3, open east-plunging F-3 folding of the regional S-2 cleavage. Regional greenschist facies meta morphism was locally followed by contact metamorphism related to intru sion of the Siluro-Devonian Frederickton, Rocky Bay and Aspen Cove plu tons. Facies distribution, ubiquitous vesicular clasts, and the volume of monomictic volcaniclastic rocks imply that the Noggin Cove Formati on is an erosional marine volcaniclastic apron built up to the south o f a shallow marine to subaerial evolving volcanic source. Back-are geo chemical affinities, coupled with lithology and stratigraphy, indicate a back-are basin paleotectonic setting.