GSSP for the Cryogenian – Ediacaran Boundary

Definition:

The base of the Ediacaran System is defined as the base of the Marinoan cap carbonate (Nuccaleena Formation) in the Enorama Creek Section of the central Flinders Ranges, Adelaide Rift Complex, South Australia. The principal observed correlation events are (1) the rapid decay of Marinoan ice sheets and onset of distinct cap carbonates throughout the world, and (2) the beginning of a distinctive pattern of secular changes in carbon isotopes.

Location:

The Enorama Creek Section is located in the central Flinders Ranges, Adelaide Rift Complex, South Australia at a Latitude of 31°19'53.2"S, and a longitude of 138°38'0.2"E.		 click


Sedimentology:

The GSSP is underlain by a varied assemblage of glacial, glacial-marine and associated deposits of the Elatina Formation. The lower contact of the Nuccaleena Formation is a disconformity, tentatively attributed to post-glacial isostatic rebound. The Marinoan cap carbonate is located at the base of the Nuccaleena Formation. It is typically no more than a few meters thick and is composed primarily of finely laminated cream and pink microspar and dolomicrite. It is interpreted to represent a short-lived chemical oceanographic event accompanying Marinoan deglaciation and sea-level rise and to be of global extent. 		click


Primary Markers:

The principal observed correlation events are (1) the rapid decay of Marinoan ice sheets and onset of distinct cap carbonates throughout the world, and (2) the beginning of a distinctive pattern of secular changes in carbon isotopes.

Other Locations around the World:

Marinoan-type cap carbonates are recognized above the Nantou Formation in China, the Blaini Formation in the lesser Himalayas (India), the Smalfjord Formation in North Norway, the Icebrook Formation in Canada, the Ghaub Formation in Namibia. The Yudoma Group in Siberia and the Vendian succession in Ukraine, both begin with a transgression within the Ediacaran Period.

References:

Knoll, A. H., Walter, M. R., Narbonne, G. M., and Christie-Blick, N., 2006. The Ediacaran Period: a new addition to the geologic time scale. Lethaia 39, p. 13-30.