国際標準模式層断面及び地点
The Cefn-cerig road, a road near Cefn-cerig Farm, Llandovery, Wales, is the location of the Global Boundary Stratotype Section and Point (GSSP) which marks the boundary between the Aeronian and Telychian stages of the Silurian period on the geologic time scale. The GSSP was ratified in 1984.