Grotte Gorf

The access gallery formed along the axis of the main joint, but at the expense of the horizontal bedding. a wall, made of large limestone blocks, was built at its entrance, leaving a passage 2 m wide by 0.50 m high. Beyond this wall, the gallery has a roughly rectangular section 1.50 m wide by 0.60 to 1 m high; its floor consists of a dry, rather dark-looking earthy fill. 7.50 m long, it gives access to the cave proper, consisting of a widened joint.

At the bottom of a 2.50 m step opens a gallery 2 m wide that extends over a length of 4 m directly below the access gallery; its height varies from 0.50 to 0.80 m and its floor consists of a pile of spoil extracted from the shaft. The shaft, 8 m deep, is artificial and dug, along the jointed wall, into the fill. The vertical section of the fill reveals its nature: small limestone blocks (frost shattering?) embedded in more or less yellowish and damp clay, without any obvious stratigraphy at first sight.

At a depth of 10 m, that is about 7 m from the top of the shaft, lies a calcite level with a thickness varying from 0.80 to 1 m, dipping downstream of the gallery; the underlying clay is very yellow and very damp, of a clayey consistency. From the -9 m mark, the joint, which being closed served as support for the fill, opens again: the space between the walls widens from 0.10 m to 1.50 m over 3 to 4 m in length. At the farthest point reached to date (-12.50 m), the fill continues, still fossiliferous.

At a depth of 10 m lies a calcite level with a thickness varying from 0.80 to 1 m, dipping downstream of the gallery; it is mainly in this calcite "floor" that the largest fossiliferous level is located, the bones being cemented there by the calcite. At the bottom of the shaft, a stalagmitic flowstone again obstructs the passage; a small concretioned "niche" is found there. Downstream, a calcite flowstone came to obstruct the gallery. The digging out was doubtless stopped by the calcite floor which, in its lower part, again hinders the work.

This cavity doubtless corresponds to a temporary sinkhole (perte temporaire) of an ancient watercourse. The excavation must have taken place at the expense of the vertical joint during the establishment of the valley that drained the surface waters, the first breakthrough creating the present access gallery. In a second phase, as the valley deepened, the gallery was abandoned while, lower down, a second conduit began to form. During a long period and at the same time as the valley was deepening, the new passage enlarged, creating the main entrance of the cave, today choked.

As the excavation of the valley continued, or at least the sinking of the waters into it, the cavity drained water only temporarily and with a slower flow, favouring the deposition of colluvium and allowing a partial fill of the main gallery. In a second phase, the water flow slowed until it was no more than a trickle allowing the establishment of a thick calcite floor. Finally, an input of sediments due to possible floods, to aeolian effects and to frost-shattering phenomena completely choked the main entrance, while downstream a calcite flowstone came to obstruct the gallery.

It would seem that before the digging out the floor sloped towards the present shaft to abut against the rock (narrowing of the joint). The digging-out work required the installation of timbering arranged in steps. The digging out was done down to about the -12 m level by crossing the calcite floor and, beneath it, progression could be made horizontally after clearing the fill, through the joint widened to about 1 m. It is certain that if the digging-out work had continued by widening the joint at this level rather than by vertical digging, the part of the deposit destroyed would have been largely preserved; but this had to be known.

In the spoil of the gallery at -3 m, very numerous bones can be seen; we extracted from these only a young bear's back-skull (in two pieces) and an atlas vertebra. At the top of the shaft, at ground level, are arranged a few bones doubtless removed from the spoil after the digging out. Bones are found to be present in the conglomerate; they seem more numerous towards the bottom of the fill. In the clay and especially in the calcite "floor" lies the largest fossiliferous level: the bones are very numerous, intertwined with one another, cemented by the calcite or embedded in clay. Numerous bones are still visible at the farthest point, either in place or laid to one side as is the case in a small concretioned "niche" at the bottom of the shaft.