After the formation associated to a period of crustal thining what amount of time did a long-lasting mountain building event occur?
Mount Pleasant Caldera:  It is one of few noticeable pre-Cenozoic calderas, and its formation is associated to a period of crustal thinning that followed the Acadian orogeny in the northern Appalachian Mountains. 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.
i don't know