"Snowball Earth" Hypothesis and the Palaeoenvironment for Life Evolution during the Late Neoproterozoic

During the Neoproterozoic,earth suffered through at least two globe-engulfing ice age.Researchersproposed Snowball hypothesis to explain a series of puzzling Neoproterozoic sedimentary recordings.This hypothesis has become an ancient widow for the study of global glaciation and bio-radiation aftermath.Other researchers,however,do not agree that the earth has been completely ice-covered.They proposed alternative hypotheses,such as Slushball/ Semifrozen Earth,and Thin-icemodels.Although,each hypothesis cannot explain all the geological and geochemical recordings,more and more evidence,especially,molecular organic geochemical and biological evidences show that the ocean was not entirely ice-covered during Snowball Earthage.Thin ice sheets or open waterzones remained in tropical areas. The open waterzone is essential for the survival and evolution of photosyntheticorganisms,which would make a significant impact on the Cambrian Bio-radiationand the evolution of life on theearth.