The Neoproterozoic (1000-540 Ma) glacial intervals: No more snowball earth?

Abstract

The Neoproterozoic interval (1000-540 Ma) contains ample evidence for a series of glacial intervals. These include the 750-700 Ma Sturtian glaciation, the 625-580 Ma Marinoan-Vendian glaciation and the 600-550 Ma Sinian glaciation. Paleomagnetic evidence has suggested that many of these glaciations occurred at tropical latitudes ( [les] 25[deg]) and this led to a number of theories that attempt to explain the occurrence of these anomalously low latitude glaciations (e.g., an increase in the axial tilt of the earth, an equatorial low-orbit ice-ring, rapid equator to pole continental drift, incorrect identification of impact deposits as glacial deposits or secondary magnetizations misidentified as primary). New paleomagnetic data for Laurentia, China, Baltica and parts of Gondwana are combined with a reanalysis of previously published data to demonstrate that the Neoproterozoic glaciations may well all have occurred above 25[deg] latitude. Climate models using a juvenile Sun of slightly lower luminosity, lower CO2 levels and coupling to Milankovitch cycles suggest that ice sheets could extend to within +/-25[deg] of the Neoproterozoic equator. Thus, the new paleomagnetic data and climate models offer an alternative explanation for the Neoproterozoic glaciations that is consistent with the waxing and waning of intermediate latitude ice sheets to form the conformable sequences of warm climate-cold climate strata.