Pre-Ordovician Polyphase Structure in the Burlington Peninsula of the Newfoundland Appalachians

Abstract

THE Appalachian System in Newfoundland can be subdivided into three tectonostratigraphic divisions characterized by differences in Early Palaeozoic depositional and structural development (Fig. 1). The Central Mobile Belt1, characterized by thick variably deformed late Precambrian sedimentary and volcanic rocks, is flanked by more stable platformal regions2,3 underlain by thinner, generally less deformed sequences of similar age. On the Western Platform these rocks unconformably overlie a gneissic Grenvillian basement. The Central Mobile Belt in the northern part of the island can be further subdivided into an axial region of sedimentary and volcanic rocks of dominantly Ordovician and Silurian age, which are generally moderately deformed and incipiently metamorphosed in contrast to the marginal crystalline belts (Fig. 1) of poly-deformed metasedimentary and metavolcanic rocks of upper greenschist to low amphibolite facies, which contain large recumbent folds4. These rocks have been subjected to polyphase deformation and moderate grade metamorphism before deposition of adjacent Lower Ordovician rocks in the west5,6 and Middle Ordovician rocks in the east7.