Antarctica A Keystone in a Changing World (2008) / Chapter Skim
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A Pan-Precambrian Link Between Deglaciation and Environmental Oxidation--T. D. Raub and J. L. Kirschvink
A Pan-Precambrian Link Between Deglaciation and Environmental Oxidation--T. D. Raub and J. L. Kirschvink
Pages 83-90
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From page 83... ...
. The sedimentary sulfate minerals barite and gypsum and effect between Earth's Neoproterozoic biosphere and also become more prevalent in evaporative environments glaciation is complicated because large and rapid True Polar post ~2.3 Ga, as seen in the Barr River Formation of the Wander events appear to punctuate Neoproterozoic time and Huronian Supergroup of Ontario (see Figure 1)
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From page 84... ...
Comparison of less exists that large-scale continental ice sheets extended well robust paleomagnetic data for all Precambrian glaciations into the tropics, yielding sea ice at the equator (Embleton with well-documented paleolatitudes for Phanerozoic glaand Williams, 1986; Evans et al., 1997; Sohl et al., 1999; cial deposits yields an interesting schism. With the possible Sumner et al., 1987)
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From page 85... ...
Blue wax This fundamental Precambrian-Phanerozoic shift in ing triangles indicate intervals of dominant supercontinent Earth's glacial mode also appears to manifest itself in the amalgamation, and red waning triangles indicate intervals relation of glacial events to a plate-tectonic supercontinent of dominant supercontinent fragmentation and dispersal. A cycle.
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From page 86... ...
with striated and faceted pebbles, and occasional dropstones Whereas Precambrian glaciations appear restricted to that attest to a glacial origin. intervals of supercontinent fragmentation and dispersal, Although all sedimentary redox indicators throughout Phanerozoic glaciations appear more generally associated the Pongola Supergroup argue for widespread anoxia, studwith supercontinent amalgamation and intervals of orogen- ies of sulfur isotopes that indicate that mass-independent esis.
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From page 87... ...
. MIF range of sulfur isotopes is diminished briefly after each The younger two of the Neoproterozoic deglaciations glacial unit, hinting at but not proving transient oxidation occupy the newly defined Ediacaran Period (Knoll et al., events.
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From page 88... ...
A sudden event known in Oman Patterns of sulfur isotopic fractionation in carbonate as the Shuram anomaly then quickly oxidized a previously associated sulfate change across the Marinoan glaciation, isolated dissolved organic carbon reservoir, and the remainsuch that seawater sulfate concentration was minimal during der of the Ediacaran Period experienced increasing levels of and after early Cryogenian glaciations, but significant fol sulfur dissimilation reactions, permitted by enhanced oxygen lowing Marinoan glaciation (Hurtgen et al., 2005)
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From page 89... ...
for Paleoproterozoic glacial events and the rise of atmospheric oxygen. Geology 32(10)
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From page 90... ...
Earth and Planetary Science Letters 2006. Production of hydrogen peroxide in the atmosphere of a Snowball 258(1-2)
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