The Gander–Avalon Zone boundary in southeastern Newfoundland

Abstract

The Dover Fault, characterized by a 300–500 m wide mylonite zone, separates the Gander and Avalon Zones in northeastern Newfoundland and formed in association with the Precambrian regional deformation that overprints these zones. In southern Newfoundland, foliated granitic rocks of the Gander Zone are separated from non-foliated granites and clastic sedimentary and volcanic rocks (Connaigre Bay Group) of the Avalon Zone by a 50–100 m wide breccia zone called the Hermitage Bay Fault. Relationships along the Hermitage Bay Fault suggest that it is an Acadian structure that modifies the original Precambrian mylonite zone.

New age data refine extent and duration of Paleozoic and Neoproterozoic plutonism at Ganderia–Avalonia boundary, Newfoundland

“…In northeastern Newfoundland, the Ganderia-Avalonia boundary is defined by a major shear zone, the Dover fault (Blackwood and Kennedy 1975;Blackwood and O'Driscoll 1976), which is defined by seismic-reflection studies as a crustal-scale structure that offsets the Moho (Keen et al 1986;Marillier et al 1989;Stockmal et al 1990). The Dover fault is a shear zone up to 25 km wide that has two documented phases of deformation and displacement: the earlier phase is ductile, exhibits sinistral transpressive kinematics, and is thought to be Silurian, whereas the later phase is brittle-ductile, exhibits dextral kinematics, and is interpreted to be Devonian or younger in age (Dallmeyer et al 1981;Hanmer 1981;Holdsworth 1994;D'Lemos et al 1997).…”

“…2). It has been interpreted as the continuation of the Ganderia-Avalonia boundary (e.g., Blackwood and O'Driscoll 1976), but has a more subtle expression in seismic reflection data (Quinlan et al 1992).…”

The Main Basement Features Recognized in the Northern Part of the North Atlantic Area

“…Later, a more accurate study of the relationship between the magnetic and gravity anomalies and the exposed Appalachian structures of eastern Newfoundland gave good arguments for proposing a Precambrian age for the structures causing the anomalies ). This proposed age was first based upon the facts (1) that the westernmost anomalies were cut obliquely at the Dover Fault-probably dating from the Hadrynian (latest Precambrian, post-Grenvillian)-which forms the western boundary of the Avalon Zone (Blackwood and Kennedy, 1975;Blackwood and O'Driscoll, 1976), and (2) that the onshore extensions of three of the lineated anomalies were shown to result from Hadrynian structures (Haworth, 1975). East of Newfoundland, no direct proof for a Precambrian age was found.…”

Timing of arrival of the Avalon Zone in the northeastern Appalachians: a new look at the Straddling Granite

“…1). Gander and Avalon Zone rocks adjacent to the fault contrast sharply in age, grade of metamorphism, lithology, and style of deformation (Blackwood and Kennedy 1975;Blackwood and O'Driscoll 1976;O'Driscoll and Strong 1979;ColmanSadd 1980). The Avalon Zone is dominated by Upper Precambrian subaerial sedimentaty and volcanic rocks and lower Paleozoic platformal sedimentary sequences, none of which have exceeded greenschist facies metamorphism.…”

“…Hanmer 198 1). Blackwood and Kennedy (1975) and Blackwood and O'Driscoll(1976) suggested from structural interpretations, based on their own work and that of Jenness (1963), that the Hermitage Bay -Dover fault system was initiated in Late Precambrian time, but that it was modified by late Acadian brittle deformation.…”