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 of stratified mafic volcaniclastic rocks with subordinate pillowed basalt and black share. Stratigraphic relationships and regional correlations indicate a Middle Ordovician age. The Carmanville Melange and the distinctive Woody Island formation, with coticule layers and olistostromes, occur along the northern margin of the Noggin Cove Formation, and the formation is faulted against siltstone and shale of the Davidsville Group along its southern margin. The Noggin Cove Formation underwent three periods of deformation: (1) D-1, early recumbent F-1 folding; (2) D-2, northeast-trending tight to isoclinal F-2 folding with pervasive axial planar cleavage (S-2); and (3) D-3, open east-plunging F-3 folding of the regional S-2 cleavage. Regional greenschist facies metamorphism was locally followed by contact metamorphism related to intrusion of the Siluro-Devonian Frederickton, Rocky Bay and Aspen Cove plutons. Facies distribution, ubiquitous vesicular clasts, and the volume of monomictic volcaniclastic rocks imply that the Noggin Cove Formation is an erosional marine volcaniclastic apron built up to the south of a shallow marine to subaerial evolving volcanic source. Back-are geochemical affinities, coupled with lithology and stratigraphy, indicate a back-are basin paleotectonic setting.