[Objective]The Cryogenian so-called"Snowball Earth"glaciation was the most extreme icehouse climate in the Earth's history.During this time,ice sheets may have extended to the low latitudes or even as far as the paleo-equatorial area,leading to a globally frozen earth and inspiring the term"Snowball Earth".However,marine chemis-try and biogeochemical cycles remained unconstrained.[Methods]To examine this,detailed geochemical analysis was carried out for the Yazhai and Fengmu sections of the Fulu Formation in the Yangtze Block,northern Guangxi province.[Results]The Fulu Formation in this region mainly consists of sandstones with rare carbonate interbeds.The stratigraphic correlation suggests that the carbonates were deposited during Sturtian glaciation.Geochemical anal-ysis shows almost uniform carbonate carbon isotope δ13Ccarb values(mean-3.5‰),decoupled from organic carbon iso-tope variation.The δ13Ccarb values are significantly higher than the mantle carbon isotope values(-6‰).[Conclu-sion]This indicates a low level of marine primary productivity during Sturtian glaciation.Massive P from marine hy-drothermal activity may have provided the nutrients to sustain synglacial organic matter production.
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