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The carbon-isotopic composition of the Neoproter- Kaufman and Knoll, 1995; Kaufman et al., 1991, 1997). The highly 13C-enriched intervals typical of interglacial times have received only minor attention, but it is Chemical Geology 237 (20ozoic oceans was generally high, but fluctuated by ata second...
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| Language: | English |
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| Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.575.4122 http://www.princeton.edu/geosciences/people/maloof/pdf/Halversonetal07.pdf |
| Summary: | The carbon-isotopic composition of the Neoproter- Kaufman and Knoll, 1995; Kaufman et al., 1991, 1997). The highly 13C-enriched intervals typical of interglacial times have received only minor attention, but it is Chemical Geology 237 (20ozoic oceans was generally high, but fluctuated by ata second exposure surface. Correlation of the lower Akademikerbreen Group δ C record with a nearly identical isotopic profile in the Bitter Springs Formation of Central Australia suggests an age of ∼800 Ma for the low δ13C interval and confirms that it is a global seawater signal. The coincidence of the negative and positive δ13C shifts with major stratigraphic perturbations in the otherwise conformable succession suggests that both episodes of transient sea level change were related to global phenomena. 87Sr/86Sr ratios rise transiently from an average of 0.7063 to 0.7066 within this interval. Whereas large negative δ13C anomalies in the Neoproterozoic are commonly associated with episodes of widespread glaciation, the Akademikerbreen low δ13C 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 δ13C interval is related to a pair of inertial interchange true polar wander (TPW) events. |
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