English: The commune lies within the Axial Zone of the Pyrenees Mountain chain. Most of the commune is underlain by gneiss, granite and metasediments of pre-hercynian (600Ma - 300Ma) age.

For example, the metasediments in the bank of the river (below the car park) in this image are of Cambrian age (c 500Ma).

However, an isolated area of younger, post-Hercynian Mesozoic formations (c 250-75 Ma), covering barely 10 square kilometres, lies immediately to the north and east of Amélie-les-Bains. The main sloping crag in this image, which rises from left to right beyond the river, and which is an outcrop of Triassic dolomitic limestone (c 240Ma), lies within this Mesozoic zone. Such Mesozoic formations once covered the entire Axial Zone of the Pyrenees. This Mesozoic zone near Amélie is of special geological interest because it is "the only outcrop of Mesozoic cover rocks of the Axial Zone in the eastern and central Pyrenees..." (Calvet, Marc; Delmas, Magali; Gunnell, Yanni; Laumonier, Bernard. 2022. Geology and Landscapes of the Eastern Pyrenees: A Field Guide with Excursions (page 407). Springer International Publishing. Kindle Edition.)