The Appalachian fold and thrust belt, Northwestern Newfoundland

Grenier, Robert (1990) The Appalachian fold and thrust belt, Northwestern Newfoundland. Masters thesis, Memorial University of Newfoundland.

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Abstract

The Appalachian fold and thrust belt was studied from Bonne Bay to Ten Mile Lake in northwestern Newfoundland. This region is a weakly emergent thrust belt that brings Grenville basement (of the Long Range Inlier) above a parautochthonous Cambro-Ordovician carbonate sequence and locally above the Humber Arm Allochthon. Reverse faults are interpreted as steep ramps above a gently east-dipping sole thrust. The most westerly basement-involved thrust is interpreted as occurring offshore throughout most of the study area and probably even occurs west of the Humber Arm Allochthon. Basement-involved thrusting postdates the Ordovician emplacement of the Humber Arm Allochthon and is most likely Devonian. -- Faults within the northwestern Newfoundland fold and thrust belt form a linked system. Along-strike variations in spacing and amount of displacement result in major differences in structural style. Three zones of contrasting structural style are recognized. In the southern zone, between Bonne Bay and Portland Creek Pond, deformation is predominantly confined to a narrow belt involving two thrusts with a hanging wall anticline and an overturned footwall syncline. In the central zone, between Portland Creek Pond and Hawkes Bay, deformation is distributed over a wider area marked by numerous high-angle reverse faults with opposing polarity. In the northern zone, between Hawkes Bay and Ten Mile Lake, deformation is accommodated by displacement on two widely spaced thrusts. -- Transport of Grenville basement above the parautochthonous carbonate sequence and the Humber Arm Allochthon is greatest in the southern zone where horizontal structural shortening has a minimum value of about 9 km., and is predominantly accommodated by the development of a regional-scale syncline-anticline pair. Structural shortening in the central and northern zones has a minimum value of 3 and 2 km., respectively, and is primarily accommodated on faults with only minor folding of strata. Structural shortening is minor at the extreme northern and southern ends of the Long Range Inlier. -- Structural telescoping of units in the Humber Arm Allochthon at St. Pauls Inlet has a minimum value of 32 km., and is interpreted to be related to Taconian emplacement. -- Faults in northwestern Newfoundland are parallel to the Long Range Dyke Swarm which was controlled by rifting during the initiation of the Iapetus Ocean. The position of the fold and thrust belt may be controlled by the reactivation of preexisting rift-related normal faults within basement rocks.

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