Glasgow University’s Department of Continuing Education organised an excursion tour to the western Pyrenees in June 2012. One of the spectacular structures that the group saw was the Torla fold, which is on the left of the photograph. The picture was taken from the village of Torla, in northern Spain.
The rocks in the Torla Fold belong to the Gallinera limestone formation, which was laid down in the Ypresian stage of the Eocene (around 50 Ma). The Gallinera Formation was distorted during the Pyrenean orogeny, which occurred later in the Eocene, at around 37 Ma, and resulted from the collision of the Iberian microplate with the Eurasian plate. The Torla fold looks like a recumbent fold, but is actually a slightly overturned drag fold caused by minor thrust faults associated with the Mont Perdu Thrust. This view is looking north, and the Mont Perdu Thrust is directed to the south, towards the camera. The plane of the thrust is roughly level with the top of the wedge-shaped bare slope that interrupts the tree cover on the mountain in the centre of the picture.