Neoproterozoic glaciations in a revised global palaeogeography from the breakup of Rodinia to the assembly of Gondwanaland
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This review paper presents a set of revised global palaeogeographic maps for the 825–540 Ma interval using the latest palaeomagnetic data, along with lithological information for Neoproterozoic sedimentary basins. These maps form the basis for an examination of the relationships between known glacial deposits, palaeolatitude, positions of continental rifting, relative sea-level changes, and major global tectonic events such as supercontinent assembly, breakup and superplume events. This analysis reveals several fundamental palaeogeographic features that will help inform and constrain models for Earth’s climatic and geodynamic evolution during the Neoproterozoic. First, glacial deposits at or near sea level appear to extend from high latitudes into the deep tropics for all three Neoproterozoic ice ages (Sturtian, Marinoan and Gaskiers), although the Gaskiers interval remains very poorly constrained in both palaeomagnetic data and global lithostratigraphic correlations. Second, continental sedimentary environments were dominant in epicratonic basins within Rodinia (>825 Ma to ca. 750 Ma), possibly resulting from both plume/superplume dynamic topography and lower sea-level due to dominantly old oceanic crust. This was also the case at ca. 540 Ma, but at that time the pattern reflects widespread mountain ranges formed during the assembly of Gondwanaland and increasing mean age of global ocean crust.Third, deep-water environments were dominant during the peak stage of Rodinia break-up between ca. 720 Ma and ca. 580 Ma, likely indicating higher sea level due to increased rate of production of newer oceanic crust, plus perhaps the effect of continents drifting away from a weakening superplume. Finally, there is no clear association between continental rifting and the distribution of glacial strata, contradicting models that restrict glacial influence to regions of continental uplift.
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