"The northern boundary of the St. Lawrence platform is defined by a Paleozoic- Precambrian contact where the Champlain Sea eroded material away. The Frontenac Arch links the Precambrian Gatineau Hills to the Adirondack Mountains and is the western limit of the Ottawa Embayment. The Beauharnois Arch is the eastern limit of te Ottawa Embayment and was active by the late Ordovician with possible reactivation at a later time. High Angle Faults define the Ottawa Embayment. Most are post Ordovician but some occured in the Ordovician. Steeply dipping Paleozoic strata can occur immediately adjacent to the faults. Otherwise, strata are subhorizontal and display broad open folds (Wilson 1946). The Appalachian orogen defines the south-eastern boundary of the Ottawa Embayment and the Allegheny Basin defines the southerly limits of the western St. Lawrence Platform." (Dix et. al, 1997)
