Duration and nature of the end-Cryogenian (Marinoan) glaciation
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The end-Cryogenian glaciation (Marinoan) is portrayed commonly as the archetype of snowball Earth, yet its duration and character remain uncertain. Here we report U-Pb zircon ages for two ash beds from widely separated localities of the Marinoan-equivalent Ghaub Formation in Namibia: 639.29 ± 0.26 Ma and 635.21 ± 0.59 Ma. These findings verify, for the first time, the key prediction of the snowball Earth hypothesis for the Marinoan glaciation, i.e., longevity, with a duration of ≥4 m.y. They also show that the nonglacial interlude of Cryogenian time spanned 20 m.y. or less and that glacigenic erosion and sedimentation, and at least intermittent open-water conditions, occurred 4 m.y. prior to termination of the Marinoan glaciation.
Prave , A R , Condon , D J , Hoffmann , K H , Tapster , S & Fallick , A E 2016 , ' Duration and nature of the end-Cryogenian (Marinoan) glaciation ' , Geology , vol. 44 , no. 8 , pp. 631-634 . https://doi.org/10.1130/G38089.1
© 2016 Geological Society of America. This work is made available online in accordance with the publisher’s policies. This is the author created, accepted version manuscript following peer review and may differ slightly from the final published version. The final published version of this work is available at https://dx.doi.org/10.1130/G38089.1
DescriptionThis work was supported by NERC Isotope Geoscience Facility Steering Committee grant IP-1462-0514.
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