The Déboulière-Vaugines Overthrust

This site reproduces and illustrates on a smaller scale what happens on a larger scale in the Luberon massif. It is a “miniature Luberon.”

Location: Vaugines (84)
Site type: Remarkable geological formation
Parking

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Surface perforée à la Déboulière, Vaugines. (S. Legal/PNRL)
Surface perforée à la Déboulière, Vaugines. (S. Legal/PNRL)

The site of Déboulière, sometimes called La Garrigue, is 2.5 kilometers long and 500 meters wide. It stands out distinctly in the landscape as a small hill emerging from the cultivated plains.

This small structure is an anticlinal fold (arched up), situated in the midst of the Durance plain. The particularity of this anticlinal is observable on its southern flank: Hauterivian limestones, dating back 130 million years old, are covered by 20 million years old Miocene marine sands, and then, again, by Hauterivian limestones. The sands were deposited on the Lower Cretaceous, as evidenced by the perforations of pholads (lithophagous bivalves) that mark the contact. These same sands are covered by another Cretaceous unit, which is overthrust and tilted southward.

The apparent amplitude of the overthrust is several tens of meters.

Similarly, the Luberon massif is overthrust to the south, covering the terrains of its foreland, but the amplitude in that case is on the order of kilometers.