Gouffre des Frachets

The opening is surrounded by a fence. It is located at the contact of the globigerina schists (SG) and the nummulitic (N).

The first part consists of a shaft 17 metres deep, which passes entirely through the nummulitic sandy limestones: 2 metres thick, and the fine bedded limestones of the Upper Cretaceous: 12 metres thick.

This shaft opens into a circular chamber of 45 m x 41 m, whose ceiling is formed by the last stratum of the Upper Cretaceous. It seems rather curious that a chamber of this size could have been excavated in the impermeable green sandstones of the Gault. We may suppose that there was a collapse of the Gault into a large pit dug in the compact limestones of the underlying Urgonian. The walls, as well as most of the blocks covering the floor, are of the Gault.

At the southern end, one can enter through a low vault into a small chamber apparently the base of a filled shaft whose ceiling and half of its circumference are formed by a cone of debris cemented by calcite.

At the southern end, the ceiling and half of the circumference of the small chamber are formed by a cone of debris cemented by calcite.

North of the chamber, a small cascade springs from the Upper Cretaceous, at the contact with the sandstones. This small stream disappears at the lowest point of the chamber, at -24 m, between enormous blocks that discourage any attempt at clearing.

The first part consists of a shaft 17 metres deep. This shaft opens into a circular chamber of 45 m x 41 m. At the southern end, one can enter through a low vault into a small chamber.

Samples of pebbles taken in this chamber were of the Upper Cretaceous: nummulitic and globigerina schists.