What is the oldest fold mountain in the world?

Answer 1

This is difficult to determine but the Green-stone belts are very old fold mountains (Southern Africa) and there are some old folded sedimentary rocks to be found in Greenland.

Answer 2

The oldest fold mountain range in the world is the Appalachian Mountains in North America. They formed around 480 million years ago during the Ordovician Period and have been eroded and reshaped over time, but still retain their folded structure.