During which geologic periods did most Pyrenean mountain building occur?

The formation of the Pyrenees involved two distinct geologic events. While an earlier mountain-building process known as the Variscan (or Hercynian) orogeny occurred between the late Devonian Period and the early Permian Period (approximately 370 to 290 million years ago), this created the older folded region that serves as the range's foundation.1

The majority of the mountain building associated with the modern Pyrenees resulted from the collision of the Iberian and European tectonic plates. Although this uplift began during the second half of the Cretaceous Period, the primary phase of mountain building occurred during the Eocene and Oligocene epochs, spanning roughly 56 million to 23 million years ago.12