Structural architecture and evolution of the Humber Arm Allochthon, Frenchman's Cove - York Harbour, Bay of Islands, Newfoundland

Buchanan, Christopher R. (2004) Structural architecture and evolution of the Humber Arm Allochthon, Frenchman's Cove - York Harbour, Bay of Islands, Newfoundland. Masters thesis, Memorial University of Newfoundland.

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Abstract

The Frenchman's Cove -York Harbour area provides extensive exposure of a critical structural contact within the Humber Arm Allochthon. The Blow Me Down Ophiolite Massif is exposed in the uppermost structural slice and complexly deformed and dismembered sedimentary rocks of the Humber Arm Supergroup are located in the intermediate slices of the allochthon. The sedimentary rocks are early Cambrian- to early Ordovician-age and represent diverse depositional settings, including early rift-basins, the continental slope of the Cambro-Ordovician carbonate platform, and syntectonic flysch deposits. -- Five tectono-stratigraphic domains are distinguished on the basis of lithostratigraphy, the geometries of fold-thrust systems, and overprinting criteria of successive generations of structures. Detailed analysis of the fold-fault systems demonstrates that four phases of deformation affect the area. D₁ forms recumbent F₁ folds and duplex structures, creating regional scale nappe-type structures. A regional scale F₂ antiformal culmination at Frenchman's Cove is associated with thrust faults that dismember folded F₁ duplex structures during D₂. Out-of-sequence D₃ fault systems, truncate the antiformal culmination and incorporate slices of volcanic rocks in an east- verging imbricate fan, and locally form discreet melange zones. D₄ consists of a steep northerly-striking fault system with apparent sinistral strike-slip fault displacements. The complex structural systems mapped in this area demonstrate that careful, detailed tectono-stratigraphic studies are required to resolve the tectonic history of the allochthon and emplacement mechanisms of the Bay of Islands Ophiolite Complex.

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