[S-CG55] Various interactions between solid Earth and climates

[SCG55-P01] マリノアンスノーボールアースの氷床融解に伴う海水準変動

*入江 芳矢¹、中田 正夫¹、奥野 淳一²、バオ フイミン³ (1.九州大学、2.国立極地研究所、3.ルイジアナ州立大学)

キーワード：全球凍結、海水準、グレイシオアイソスタシー

The Marinoan snowball Earth, which ended at ~635 Ma, offers us a set of sedimentary and geochemical records for studying a relative sea level (RSL) history of Earth system response to a large perturbation and its accompanied changes in the atmosphere and biosphere. An accurate perdition of post-Marinoan RSL changes would set independent constraints on the rate of recovery of the Earth system from a snowball state. Here we examine RSL changes due to glacial isostatic adjustment (GIA) associated with Marinoan snowball deglaciation by chiefly considering two RSL change patterns, (i) an RSL drop followed by RSL rise in the syn-deglacial phase (melting phase) inferred from the cap dolostones deposited on the continental slope in Namibia, and (ii) an RSL drop followed by RSL rise in the post-deglacial phase (time after the complete melting) inferred from the cap dolostones deposited on the continental shelf in South China, West Africa and Canada. We show that the physical mechanisms responsible for (i) and (ii) mainly depend on the coastline geometry, the syn-deglacial duration and mantle viscosity structure. Our modeling suggests that the RSL change patterns (i) and (ii) are explained by adopting the coastline geometry like a peninsula, a syn-deglacial duration of 10–20 kyr and a viscosity of ~10²³ Pa s in the deep mantle. The deep mantle viscosity of ~10²³ Pa is roughly equal to that inferred from the recent analyses using GIA data sets due to the last deglaciation.