Field associate Pippa Halverson from Harvard University with his hand on a knife-sharp flooding surface representing an end to a ca. 720 million-year-old ice age in the Otavi Group of Namibia.  Below his hand are boulder sized granite and carbonate dropstones from the glaciomarine Ghaub Formation.  Above are finely laminated, fine-grained dolomicrites of the Maieberg Formation, likely deposited very rapidly as the glaciers melted and sealevel rose.

Secular variations in the carbon-isotopic compositions of inorganic carbonate and co-existing organic carbon.  The significantly reduced fractionation in the cap carbonates immediately above and below the glaciations suggests carbon limitations to growing photosynthetic microorganisms.