ATLANTIC GEOLOGY 163 Inversion or Taconian structure during Acadian overthrusting, Port Au Port Peninsula, Newfoundland G.S. Stockmal Geological Survey of Canada, Atlantic Geoscience Centre, P.O. Box 1006, Dartmouth, Nova Scotia B2Y 4A2, Canada and J.W .F. Waldron Department of Geology, St. Mary's University, Halifax, Nova Scotia B3H 3C3, Canada The structural front of the northern Canadian Appalachians has been facilitated by our recognition that restricted Middle lies submerged beneath the Gulf of St Lawrence for most of its Ordovician basins, which formed adjacent to early Taconian length. It is oriented parallel to and lies just offshore of the west normal faults and within fault-bounded graben, were "inverted" coast of Newfoundland as far south as the Port au Port Peninsula. by reverse-sense reactivation of the associated normal faults where it and associated structures come ashore and are exposed. during subsequent orogenic shortening. These basins contain the The structure of the Port au Port Peninsula has been interpreted spectacular conglomeratic Cape Cormorant Formation (upper by us to lie within a foreland "triangle zone" that developed Table Head Group) and lower Goose Tickle Group turbiditic during Ordovician (''Taconian") and Siluro-Devonian (''Ac­ flysch. adian") compressional episodes; importantly, some early Tac~ Local overturning of the upper detachment of the triangle nian structures affecting the Cam bro-Ordovician carbonate plat­ zone, along the extreme western edge of the peninsula, is consid­ form were extensional. Carboniferous strike-slip deformation is ered a direct consequence of basin inversion. Structural thinning minor, overprinting earlier structures. Structural interpretation of overturned stratigraphy can explain perplexing map and Atlantic Geology, July 1991, Volume 27, Number 2 Copyright © 2015 Atlantic Geology 164 ABSTRACTS outcrop patterns of units in the hangingwall of the triangle wne presence of lateral ramps that result in map-scale structural upper detachment The non-cylindrical nature of this and associ­ culminations and depressions. Structures mapped within the ated structures resulted from reactivation of faults oblique to the carbonate platfonn support our previous interpretation that the thrust front Other non-cylindrical complications arise due to the platfonn is highly transported. .