The relationship between the Gander and Avalon zones in the Bonavista Bay region, Newfoundland

Blackwood, R. Frank (1976) The relationship between the Gander and Avalon zones in the Bonavista Bay region, Newfoundland. Masters thesis, Memorial University of Newfoundland.

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Abstract

The Dover Fault, characterized by a 300-500 metre wide mylonite zone, forms the boundary between the Gander and Avalon Zones in Bonavista Bay, Newfoundland. The Gander Zone, northwestwards of the fault, is underlain by a basement gneiss complex consisting of orthogneiss and paragneiss. The gneisses are intruded by a variety of granitic rocks including megacrystic granite, garnetiferous granite and gabbro. A strong, regionally developed, cataclastic foliation is superimposed upon the gneissic banding and overprints some of the granitic rocks. Metasedimentary rocks form a cover sequence to the basement gneisses in the northwestern part of the area. -- The Avalon Zone, southeastwards of the Dover Fault, is underlain by Hadrynian volcanic rocks which are strongly foliated. Late Hadrynian - Early Cambrian Molasse rocks post-date the deformation of the volcanic rocks. -- The Dover Fault formed in association with the regional cataclastic foliation, both are products of a tectonic event which overprints the Gander Zone and deforms the Precambrian volcanic rocks of the Avalon Zone. Thus the main movement on the fault is Precambrian. In southeastern Newfoundland, the Hermitage Bay Fault, characterized by a 50-100 metre wide breccia zone, forms the boundary between the Gander and Avalon Zones. Here, Paleozoic brecciation has destroyed most of the original (mylonitic) structure. -- The Gander and Avalon Zones form two major tectonostratigraphic belts which may be traced all along the southeastern side of the Appalachian-Caledonian system. Precambrian orogenic activity affecting these two zones is likely related to the Cadomian Orogeny.

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