Nonmonotonic Postdeglacial Relative Sea Level Changes at the Aftermath of Marinoan (635 Ma) Snowball Earth Meltdown
© 2019. American Geophysical Union. All Rights Reserved. Marinoan snowball Earth offers us a set of sedimentary and geochemical records for exploring glacial isostatic adjustment (GIA) associated with one of the most severe glaciations in Earth history. An accurate prediction of GIA-based relative sea level (RSL) change associated with a snowball Earth meltdown will help to explore sedimentary records for RSL changes and to place independent constraints on mantle viscosity and on the durations of syndeglaciation (Td) and cap carbonate deposition. Here we mainly examine postdeglacial RSL change characterized by an RSL drop and a resumed transgression inferred from the cap dolostones on the continental shelf in south China. Such a nonmonotonic RSL behavior may be a diagnostic GIA signal for the Marinoan deglaciation resulting from a significantly longer postdeglacial GIA response than that for the last deglaciation. A postdeglacial RSL drop followed by transgression in south China, which is significantly affected by Earth's rotation, is predicted over the continental shelf for models with Td ≤ 20 kyr and a deep mantle viscosity of ~5 × 1022 Pa s regardless of the upper mantle viscosity. The inferred GIA model also explains the postdeglacial RSL changes such as sedimentary-inferred RSL drops on the continental shelf in northwestern Canada and California at low-latitude regions insignificantly affected by Earth's rotation. Furthermore, the good match between the predicted and observed RSL changes in south China suggests an approximate duration of ~50 kyr for the Marinoan 17O depletion event, an atmospheric event linked to the post-Marinoan drawdown of CO2 and the concurrent rise of O2.
Publication Source (Journal or Book title)
Journal of Geophysical Research: Solid Earth
Irie, Y., Nakada, M., Okuno, J., & Bao, H. (2019). Nonmonotonic Postdeglacial Relative Sea Level Changes at the Aftermath of Marinoan (635 Ma) Snowball Earth Meltdown. Journal of Geophysical Research: Solid Earth, 124 (8), 9373-9394. https://doi.org/10.1029/2018JB017260