Abstract

Rocks ranging in age from late Precambrian to early Carboniferous, and (or) Late Devonian, have been deformed by intense cataclasis in a broad upwarped belt which extends for a distance of 140 km along the Bay of Fundy in southern New Brunswick. This upwarped belt is denned by a penetrative cleavage (S1), which is generally roughly parallel to bedding (S0) in sedimentary rocks, although cross-cutting relationships have been observed. Most rock and mineral fragments in these deformed rocks have been crushed, flattened, stretched, and (or) pulled apart in several directions parallel to S1. In a few localities, S1 is roughly parallel to axial surfaces of mesoscopic folds (F1), but there is no evidence for regional F1 folds. S1 surfaces have been folded, throughout almost the entire area, by a second group of folds (F2) and a third group of folds (F3) mainly in the northeastern part of the belt. These structures have, in numerous localities, been truncated by high-angle reverse or normal dip-slip faults and locally by low-angle thrusts.

The S1 fabric probably resulted from up-warping or bending (under a lithostatic load) which was produced by vertical movements of basement blocks underlying deformed layers. Mesoscopic F1 folds are believed to have formed along the margins of uplifted blocks. F2 folds appear to have resulted mainly from gravity sliding along slopes produced by continued upwarping. F3 folds were produced by slip roughly parallel to S1.

The structure of the “Fundy cataclastic zone” differs greatly from the Acadian (Middle Devonian) deformed belt, which is characterized by upright, close to isoclinal folds produced by northwest-to-southeast shortening. The vertical block movements, to which we attribute the cataclastic deformation, probably occurred during a period of readjustment following the Acadian orogeny.

First Page Preview

First page PDF preview
You do not currently have access to this article.