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At least two global Neoproterozoic (Cryogenian) glaciation events ("Snowball Earth") occurred 710 Ma (Sturtian) and 630 Ma (Marinoan) ago, during which the oceans were either completely frozen or at most a few small open water oases remained. Neither the cause of the onset of the glaciations, their extent and duration, nor the cause for the deglaciations, are currently fully understood.

In this study we try to follow up earlier studies by our group that indicated the presence of an extraterrestrial signature in rock units that mark the transition between the glacial diamictites and the overlying cap carbonates. This study deals with the suggestion that a large-scale impact event might have triggered the rapid deglaciation.

Here we discuss the search for impact signatures using mineralogical and geochemical methods in samples from the Chuos/Rasthof (Sturtian) and Ghaub/Maieberg (Marinoan) postglacial transition at the Neoproterozoic Otavi Group (Namibia). However, no geochemical and mineralogical signatures that would be characteristic of an impact, such as an enrichment in siderophile element abundances or the presence of Cr-spinels or shocked minerals, were detected in our samples. Thus, there is no indication yet that an impact event was involved in the formation of the studied transition layers.