Slump Folds and Early Structures, Northeastern Newfoundland Appalachians: Re-Examined

The Bard Island area (Bear Path Cove) presents a well exposed section of complex fold styles that crop out in central Notre Dame Bay, Newfoundland, which have previously been interpreted as a good example of wet-sediment deformation. A re-examination of this classic area shows that the deformation history was more complex than previously thought. The earliest phase of deformation in the Upper Ordovician Point Leamington Formation (deep-marine turbidites) may have occurred while the sediment was semi and/or unlithified. Whether this was a surficial product of slumping or (stratigraphically deeper) thrusting is not known. The majority of structures around Bard Island are demonstrably the result of "hard rock" tectonic deformation with the imposition of the late Silurian regional Acadian (D₂) deformation onto previously deformed (D₀, D₁) late Ordovician rocks. The earliest tectonic (hard rock) folds (F1) were westward-closing recumbent folds with curvilinear subhorizontal axes (N-S trending) with an associated cleavage. Pre-D₂ boudinage is also recorded where highly attenuated beds have local quartz veins cross-cut by the S₂ cleavage. No macroscopic D₁ structures were recognized in the area. D₂ structures trend NE-SW, dip steeply to the NW, and generally involve tight, shallowly plunging folds with an associated slaty cleavage. F3 folds are regionally restricted and not present in the study area. Further deformation about NW-SE to N-S axes was the result of post-Acadian (F₄) folding. D₅ faults also contribute to the overall complexity of the area by displacing pre-existing linear structures (e.g., F₂ fold axes).