Dynamics of Marinoan-age glaciers in NW Tarim, China

Abstract

Glaciers were pivotal agents in shaping Cryogenian landscapes through erosional and depositional processes. Subglacial erosional forms serve as critical archives of glacial dynamics and thermal regimes, offering insights into paleoenvironmental interpretation and paleogeographic reconstruction. Cryogenian subglacial erosional forms are preserved on seven cratons globally, with China’s excellent example located in the Aksu-Wushi area of the northwestern Tarim Craton. A series of well-preserved erosional features of subglacial origin crop out, which until now have not been subject to systematic description or interpretation. This is redressed herein, and eight sites are surveyed in detail, enabling considerable insight into and unintegrated that have hindered research on Cryogenian glacial dynamics. In the Aksu-Wushi area, striations, grooves, p-forms, roches moutonnées, and glacial plucking morphologies, testify to both abrasion and meltwater processes at the ice-bedrock interface. A southwest-directed ice flow, with gradual southward deflection, is identified. Subglacial erosional forms and the overlying sedimentary successions documented in this study jointly reveal the depositional environmental evolution of the Yuermeinak Formation from subglacial to proglacial to post-glacial transgression, forming a complete record of continental ice sheet advance-retreat processes. The dynamic patterns and thermal regime of the Marinoan glacier further provide critical constraints for paleogeographic reconstruction. The consistent ice flow directions and sedimentary evolution observed in both the Yuermeinak Formation (Tarim) and Walsh Formation (Australia) collectively suggest that the Tarim was likely adjacent to the Australia during the Cryogenian period. The subglacial erosional forms and striated clasts at Aksu-Wushi area indicate a temperate glacial thermal regime during the latter stages of the snowball Earth event, compatible with a mid- to low-latitude paleogeographic setting. The massive gravel-bearing sandstone and siltstone with dropstones between the basal diamictite and overlying Ediacaran cap dolomite represents large-scale chemical weathering at the end of temperate glacier. Thus, paleo-glaciology can play a vital role in deep time paleogeographic reconstructions.