Peter William Crockford, Akshay Mehra, Paul F Hoffman

Snowball Earth cap carbonate sequences provide an archive of what are likely the most dramatic climate transitions in all of Earth history. One approach to gain insight into these events is the detailed observation of sedimentary structures within these post-glacial units. Here, we report on newly discovered radially-symmetric sedimentary structures within the Keilberg Member post-Marinoan ‘cap dolostone’ from the Otavi Group of northwest Namibia. We describe the local expression of over 60 decimeter-scale cymbal or disc structures from a single location. We interpret these features, which we name Zildjian structures, to be of likely abiotic origin. Through morphological comparisons, we suggest that Zildjian structures are most similar to Astropolithon, a pseudofossil which formed as a result of fluid or gas expulsion.