Tonian glaciation in South China

Paleoclimatic conditions during the Tonian Period (~1000-720 Ma), preceding the Cryogenian Snowball Earth glaciations, remain ambiguous. While the apparent paucity of glacially influenced sedimentary rocks suggests a stable and dominantly ice-free climate during the late Tonian, several pre-Sturtian glacial deposits have been tentatively identified. To investigate climatic conditions leading up to the Cryogenian, we present glacial till depositions in Tonian from four outcrops in the Tongshan, South China, along with geochemical and geochronologic data from one of these sites, revealing significant regional climatic shifts during the Tonian period. This glacial till deposition is constrained older than 745.3 Ma from zircon age and is constrained in 792.1–773 Ma through stratigraphic correlation. In addition, another climatic cooling at ~750 Ma, although with no clear sedimentological evidence, is evidenced by decreased weathering proxy. This climatic cooling may have been correlated with the glaciolacustrine deposits of the Konnarock Formation in southwestern Virginia, USA. Our findings thus reveal the existence of at least two cold climate intervals during the late Tonian Period, thereby providing novel insights into the evolution of global climate conditions in advance of the Cryogenian Snowball Earth.