Ediacaran Cordilleran-type mountain ice sheets and their erosion effects

Glacial erosion has long been recognized as a significant factor contributing to continental denudation during the Ediacaran Period, consequently leading to geochemical perturbations and biotic evolution in marine environments. However, the role of Ediacaran glaciation in the oceanic geochemical perturbations remains controversial due to ambiguous geochronological correlations and unresolved paleogeographic and tectonic settings. A total of 45 Ediacaran glacial records have been reviewed and categorized into four Ediacaran glaciations: Gaskiers (581-579 Ma), Fauquier (ca. 571 Ma), Bou-Azzer (ca. 565-560 Ma), and Hankalchough (ca. 562-551 Ma) glaciations. Of these glacial records, 53% have been reported in the Avalonian-Cadomian and Altaids accretionary orogenic belts, recognized as representing Cordilleran-type mountain ice sheets (CMISs). This study reports an Ediacaran glaciation in the southern Altaids, NW China, with 18 glacial and non -glacial facies and 1173 new U-Pb-Hf data from detrital zircons. The maximum ages of deposition based on detrital zircons from the Ediacaran to Lower Cambrian strata indicate an age range from 591.1 to 561.9 Ma for the glacial and deglacial sequences. The glacial sequences consist mostly of proglacial marine facies associated with icerafted diamictites and turbidite facies. The unimodal detrital zircon feature of these proglacial facies suggests that the glaciation center was located proximal to a ca. 644 Ma magmatic arc. A statistical comparison of detrital zircon facies was conducted on a regional Ediacaran dataset compiled from 12,291 U-Pb-Hf data points from the Altaids, Siberia, Tarim, North China and South China Cratons. The result suggests the presence of CMISs extending from Beishan to Yili Tianshan and Kyrgyz Tianshan along an active margin of the Paleo-Asian Ocean (PAO). The provenance shift and exhumation of a ca. 967 and 2469 Ma granitic basement suggests that erosion by the Ediacaran ice sheets provided a greater contribution to the terrestrial influx and geochemical perturbations in the late Ediacaran oceans compared with other glacial and tectonic events.