Mid-latitude climatic oscillation during the late Ediacaran ice age

The enigmatic Ediacaran ice age bridged the extreme Cryogenian Snowball Earth glaciations and the Cambrian Explosion, and witnessed the emergence of the Ediacara biota, the earliest complex macroscopic life forms in Earth's history. However, due to the lack of precise geochronological and paleomagnetic data, the temporal and spatial distributions of Ediacaran glaciations remain controversial. It is unclear whether it was episodic or continuous, and local or global. In this study, we present convincing sedimentological evidence showing the advance and retreat of Ediacaran glaciation based on the study of Talisayi Formation in the Guozigou section, northwestern China. The intercalated sandstone, siltstone, mudstone, and especially ¹³C-enriched carbonates within the glacial deposits indicate that normal marine deposit and primary productivity persisted during the Ediacaran ice age. Furthermore, by compiling global Ediacaran glacial deposits, we identified five Ediacaran glacial depositions containing interglacial carbonate and three sections with multiple sets of glacial diamictite intercalated with normal marine deposition. These sedimentological observations argue episodic glacial wax and wane in low to mid latitude and bring up our hypothesize that the overlapping of glaciers zone and carbonate production zone during the Ediacaran ice age. The carbonate precipitation may either be the result of regional warming after glacial retreat or the consequence of high seawater alkalinity due to pervasive carbonate dissolution of glacier eroded or grinded carbonate platforms. Such climatic condition is consistent with the ‘Great Ediacaran ice age’ model, characterized by a continuous and mid-to-high-latitude glaciations. The prolonged Ediacaran ice age also implies an icehouse background for the evolution of Ediacaran biota and the emergence of early animals.