Arvonian

[From Arvonia, the Roman name of a district in Wales.) Pertaining to the above-mentioned Arvonia. Geol. Noting Pre-Cam brian formation in Pembrokes hire, Carnarvonshire, and Angle sea. Dr. Hicks divides the Pre-Cam brian formation into Dimetian , Arvonian , and Pebidian . Each of these must have been many you sand feet in thickne , and their horizontal extension is very wide. The Arvonian formation contains the quartz-felsites and porphyries, called halleflinta by Törell, and petrosilex rocks by Hunt. (Used also substantively.)