GSSP for Cryogenian Stage

Definition:

The base of the Cryogenian System will be placed at a globally correlative level that lies stratigraphically beneath the first appearance of widespread glaciation and is assigned in the interim a 'calibrated age' of circa 720 Ma. This definition should be used in publications until a formal Cryogenian GSSP can be ratified.

References:

Shields-Zhou, G., Porter, S.A. and Halverson, G.P. 2016. A new rock-based definition for the Cryogenian Period (circa 720–635 Ma). Episodes, 39, 3–9, DOI: 10.18814/epiiugs/2016/v39i1/89231