Post-Taconian shortening, inversion and strike slip in the Stephenville area, western Newfoundland Appalachians

• Published in: Canadian Journal of Earth Sciences
• Main Authors: Palmer, Sarah E, Waldron, John W.F, Skilliter, D M
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 2002
• Subjects: Newfoundland
• Online Access: http://dx.doi.org/10.1139/e02-041; http://www.nrcresearchpress.com/doi/pdf/10.1139/e02-041

Deformed terrigenous and carbonate sedimentary rocks representing the early Paleozoic Laurentian continental margin form a series of elongate, fault-bounded blocks that plunge north beneath the Humber Arm Allochthon in the Stephenville area, west Newfoundland Appalachians. The continental shelf succession was folded and thrust-faulted after emplacement of the Humber Arm Allochthon. In the west of the area, Table Mountain is cut by a "pop-up" structure bounded by downward-converging reverse faults. Structures at the east margin of Table Mountain indicate both dextral and reverse slip. The Phillips Brook Structure, farther east, contains multiple, fault-bounded carbonate slices; one slice, carried by the West Blanche Brook fault, is thrust over the Humber Arm Allochthon. The western edge of the Indian Head massif, consisting of Grenville basement, is also a thrust contact. These reverse faults and thrusts, which cut the carbonate succession and postdate emplacement of the Humber Arm Allochthon, are in turn overprinted by structures formed during dextral strike-slip motion. Unconformable Early Carboniferous cover postdates most of the deformation. Cross-sections indicate shortening of a few kilometres, and basement was clearly involved in the deformation. The Port au Port Peninsula, immediately to the west, records a history of Acadian inversion of Taconian basins. The prevalence of pop-up structures and mappable variations within the stratigraphic units forming the top of the carbonate succession indicate that a complex geometry of Taconian horsts and grabens was inverted during post-Taconian (?Acadian) shortening and dextral strike-slip motion. These relationships suggest a variety of attractive targets in petroleum exploration.