Acadian orogeny Acadian orogeny The Acadian orogeny is a long-lasting mountain building event which began in the Middle Devonian, reaching a climax in the early Late Devonian. It was active for approximately 50 million years, beginning roughly around 375 million years ago, with deformational, plutonic, and metamorphic events extending into the Early Mississippian. The Acadian orogeny is the third of the four orogenies that created the Appalachian orogen and subsequent basin. The preceding orogenies consisted of the Potomac and Taconic orogeny, which followed a rift/drift stage in the Late Neoproterozoic. The Acadian orogeny involved the collision of a series of Avalonian continental
Grenville orogeny the Highlands to the southeast and the Lowlands to the northwest. It is believed that the shear zone (the Carthage-Colton) was a transpressional boundary during the Ottawan, when the Highlands were thrust over the Lowlands. The Grenville province is named for the village of Grenville in Quebec, and constitutes the youngest portion of the Canadian Shield. Since the area has not undergone any regional metamorphic overprinting since the orogeny, it is considered an ideal study area for Grenville and pre-Grenville age tectonics. Hence, most of what is known about the orogeny and its processes is derived from the Grenville Province.