Stratigraphy and geochemistry of a ca 800 Ma negative carbon isotope interval in northeastern Svalbard

The Neoproterozoic Akademikerbreen Group in northeastern Svalbard comprises 2 km of nearly pure carbonate section. The carbonates are generally highly C-enriched (δCN5‰), but this trend is interrupted by an ∼325 m interval of low δC values (−4 to 0‰) in the upper Grusdievbreen and lower Svanbergfjellet formations. An abrupt negative isotopic shift at the onset of this low δC interval is reproduced in detail in multiple sections along the length of the outcrop belt (125 km) and everywhere coincides with a prominent sequence boundary and change in lithology. Likewise, the return to positive δC values coincides with a second exposure surface. Correlation of the lower Akademikerbreen Group δC record with a nearly identical isotopic profile in the Bitter Springs Formation of Central Australia suggests an age of ∼800 Ma for the low δC interval and confirms that it is a global seawater signal. The coincidence of the negative and positive δC shifts with major stratigraphic perturbations in the otherwise conformable succession suggests that both episodes of transient sea level change were related to global phenomena. Sr/Sr ratios rise transiently from an average of 0.7063 to 0.7066 within this interval. Whereas large negative δC anomalies in the Neoproterozoic are commonly associated with episodes of widespread glaciation, the Akademikerbreen low δC interval precedes the oldest (Sturtian) of the known Neoproterozoic glacial events, and no other evidence suggests an ice age at this time. We propose instead that the negative δC interval is related to a pair of inertial interchange true polar wander (TPW) events. © 2006 Elsevier B.V. All rights reserved.