Neoproterozoic Paleontology

To compliment our refined environmental records, my group and our collaborators have embarked on a parallel effort to construct a time-calibrated Neoproterozoic paleontological database.  We began this work in NW Canada where we dated the Bitter Springs d13C event to 811.5 ± 0.3 Ma, and used this marker to recalibrate the diversification of eukaryotic crown groups [16].  We also remapped outcrops containing unique scale microfossils and reassigned these strata to units that are ~150 million years older than previous estimates [11], directly above the 811.5 Ma horizon [16].  Further work demonstrated that these microfossils are likely akin to green algae, are composed of phosphate, and may represent the earliest know example of eukaryotic biomineralization [24].  We then extended our reassessment of the Neoproterozoic microfossil record to Death Valley, CA, where a dolostone bed within the glacigenic Kingston Peak Fm had been claimed to represent a syn-glacial microfossil assemblage. Our group’s mapping and geochemical studies show that the fossiliferous horizon are olitstostroms (slump blocks) from a particular horizon in the underlying Beck Spring dolomite, and thus cannot be used to assess the nature of the glaciations [33].  While clearing up the context of these earlier finds, we have discovered new Neoproterozoic microfossil assemblages in Mongolia, Namibia, Death Valley, and the Yukon [24-27,33,34].  These initial efforts suggest that there are major differences in microfossil assemblages before and after the Sturtian glaciation that may be useful not only for biostratigraphy, but also for understanding the impact of global glaciation on the evolution of life.