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Subglacial erosional forms of Marinoan glacier in NW Tarim, China

Yuermeinak Formation, Cryogenian, subglacial erosional forms, thermal regime, paleogeography, Tarim

Theme 3: Earth-Life Co-evolution Through Time > Session 3b: Evolution of the Earth-Life System During the Neoproterozoic-Paleozoic Transition

Glaciers were a central element of the Cryogenian period in the Neoproterozoic era. Through their movement, glaciers shaped both depositional and erosional landforms. The latter serve as critical evidence for understanding glacier kinematics and represent the most definitive indicator of thermal regimes. These landforms hold significant implications for determining sedimentary environments and reconstructing paleogeography. Cryogenian subglacial erosional forms are preserved on several cratons globally, with China’s only example located in the Aksu area, NW Tarim Craton. However, numerous well-preserved erosional forms here remain unsystematically described and studied, hindering research on Cryogenian glacial dynamics, depositional environments, and paleogeographic reconstruction of the Tarim Craton. Detailed measurements and characterization were performed on eight sites of Cryogenian erosional forms in Aksu, identifying striations, various p-forms, and roche moutonnées, which indicate meltwater involvement at the ice-bedrock interface and reflect glacial kinematics with a northeast-to-southwest moving direction. Subglacial erosional forms and the overlying sedimentary successions jointly reveal the depositional environmental evolution of the Yuermeinak Formation from subglacial to proglacial to post-glacial transgression. In contrast, global Marinoan glaciation (represented by the Nantuo Formation), which lack subglacial erosional forms, are generally interpreted as glaciomarine deposits. The erosional forms and overlying sedimentary successions documented in this study form a complete record of continental ice sheet advance-retreat processes. Global correlations indicate that major cratons worldwide likely experienced evolution from continental to glaciomarine glacier during Cryogenian. The subglacial erosional forms and striated clasts of the Marinoan glaciation indicate a temperate glacial thermal regime during the latter stages of the snowball Earth, with such warm-based glacier further pointing to a mid- to low-latitude paleogeographic setting. The consistent ice flow directions observed in both the Yuermeinak Formation in Tarim and Walsh Formation in Australia collectively suggest that the northwestern Tarim was likely adjacent to the northwestern Australia during the Cryogenian, with both occupying mid-low paleolatitudes.