Possible Cryptic Suture in South-west Newfoundland

Abstract

THE concept of an important fault, the Cabot Fault, cutting across western Newfoundland was proposed by Wilson1 who interpreted it as a great sinistral fault and correlated it with the Great Glen Fault system in Scotland. There is, however, a second large fault in south-west Newfoundland, the Cape Ray Fault, the importance of which has previously been unrecognized. This fault separates two entirely different pre-Ordovician gneissic terrains which, when traced north-eastwards from Port aux Basques (Fig. 1) form the eastern and western margins of the Newfoundland Central Mobile Belt. This belt contains Lower Ordovician rocks in its central part which are interpreted as remnants of an old ocean floor, the proto-Atlantic1–5. The Cape Ray Fault thus effectively cuts out this ocean toward the south and juxtaposes its eastern and western margins. It may therefore represent a cryptic suture along which complete closure of the proto-Atlantic took place.