Note on the use of hydrofluoric acid for the recovery of conodonts from Ordovician cherts in the Southern Uplands of Scotland and the significance of the conodonts

Abstract. Procedures have been described for the recovery of conodonts from cherts by dissolution in hydrofluoric acid (see Stone, 1987 for a review), but this technique rarely has been applied. Cherts are more widely distributed in southern Scotland than are limestones which have been the focus of most research on conodonts. The HF technique thus opens a new and possibly more widely applicable avenue for conodont research for southern Scotland than the traditional methods.

Ordovician conodonts on the surfaces of red cherts were reported from several localities near Peebles by Lamont and Lindström (1957), and the same authors found conodonts in yellow silt-stones interbedded with cherts south of Abington. These localities were visited to obtain samples that we believed to have a high probability of containing conodonts in order to test the HF procedure on Scottish rocks. We found conodonts in red rocks like those reported by Lamont and Lindström at their Noblehouse and Ruddenleys localities. Unfortunately the rocks there are not cherts as they reported, but are red mudstones instead. Such rocks are not amenable to the HF techniques.

Microscopic examination of grey cherts collected loose below Ravengill Burn (Grid Reference 26/921199, one of Lamont and Lindstrom’s localities) showed that they contained radiolaria, a common fossil in the cherts of Scotland. Small pieces of these cherts, aggregating about 50 g, were placed in dilute (10% by volume) HF. The acid was decanted episodically after periods ranging from 8 hours to 73 hours, and the undissolved material was wet-screened through a . . .