Composite sand-ice wedge pseudomorphs suggestive of a frosty Ediacaran–Cambrian transition

The Ediacaran–Cambrian transition (approx. 580–520 million years ago), one of the most critical intervals in Earth's history, witnessed physical environment change and climate fluctuations coupled with extraordinary radiations of metazoan life. Up to now, there are insufficient data to evaluate the true nature of the Ediacaran–Cambrian transition climate. This research reports the newly discovered wedge structures on the Luoquan glacial diamictites in western Henan, North China Craton, to discuss and try to prove the nature of the Ediacaran–Cambrian transition climate fluctuation. The results show that the Luoquan wedges show downward V-shaped pinching in two dimensions, with heights of 20–400 cm and widths of 3–25 cm. A cryogenic origin of composite sand-ice wedge pseudomorphs is the most likely interpretation based on observations of their morphological, textural, and sedimentological characteristics. The observed evidence is ambiguous but could indicate an extremely cold climate resulting in periglacial environments during the Ediacaran–Cambrian transition. These findings can contribute to a better understanding of extreme fluctuations in the global climate that probably affected ocean chemistry and biological evolution during the Ediacaran–Cambrian transition.