GSSP for Ediacaran System
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.
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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.
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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.
Correlation Events:
(1) 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.
Notes on Derivation of Age:
Age suggested by Ediacaran Subcomm.; bracketed by radiometric ages of 600 and 635 Ma
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.
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