A thick section of rock along its cliffs is designated the Global Boundary Stratotype Section and Point ( or GSSP ) representing the boundary between the Precambrian era and the Cambrian period , million years ago .
A 140 m thick section of rock along its cliffs is the Global Boundary Stratotype Section and Point ( GSSP ) . It represents the boundary between the Precambrian era and the Cambrian period , 541 million years ago .