Sarah E. Palmer

The Stephenville area of western Newfoundland contains Precambrian basement, an Early to Middle Paleozoic continental shelf succession, and Late Paleozoic cover rocks. These units have been variably transported and deformed in several tectonic episodes during Appalachian orogenesis. In the Middle Ordovician Taconian Orogeny, the Humber Arm Allochthon was thrust onto the shelf succession. Structural relationships within the shelf succession indicate a major tectonic event post-dating Middle Ordovician thrusting. The rocks (a clastic shelf succession overlain by a carbonate-dominated platform succession) outcrop in three northeast-trending ridges; Table Mountain, Whale Back Ridge and the Phillips Brook structure.

The structures on Table Mountain are dominantly faults and associated folds. The Table Mountain Fault Zone comprises several west-vergent faults and one east-vergent fault, which create a "pop-up" or flower structure and separate two large blocks of platform carbonates. Stratigraphic variations and geometries of the faults within the Table Mountain Fault Zone indicate reactivation from previous normal faults. The Romaines Brook Fault is a steep fault with a component of dextral strike-slip movement that bounds the east edge of Table Mountain. Further east on Whale Back Ridge, a north-trending fault, the Kippens Fault, places upper carbonate platform rocks to the east above the Taconian Humber Arm Allochthon to the west. Faults in the Phillips Brook structure include: the Indian Head Thrust System comprising several sinuous reverse faults with considerable stratigraphic separation; the West Blanche Brook Fault which locally places platform strata above the Taconian Humber Arm Allochthon; and the Cold Brook Fault, a steep fault, bisecting the Phillips Brook structure, with a component of dextral strike-slip movement.

A tectonic history can be established, based on field relationships and stratigraphic evidence, in which Taconian extension and later allochthon emplacement was followed by several shortening events, propagating from east to west and placing platform successions above the Taconian allochthon. This was followed by a dextral strike-slip event which probably occurred in the Devonian period.

Keywords:
Pages:
Supervisor: