Dr. Lydia Tarhan

Please Join the Geology Department for a colloquium entitled "Taphonomy and Paleoecology of the Ediacara Biota", presented by Dr. Lidya Tarhan, Yale University

The colloquium will be held in Edmunds 130 at 11 AM on Friday February 3rd.


The Ediacara Biota, Earth’s earliest fossilized complex, multicellular ecosystem, is preserved in terminal Ediacaran strata worldwide, in the wake of the severe climatic perturbation of Snowball Earth and just prior to the Cambrian Explosion. Ediacara fossil assemblages consist of exceptionally preserved soft-bodied forms of enigmatic morphology, ecology and affinity which nonetheless represent a critical stepping-stone in the evolution of complex animal ecosystems. Many Ediacara fossil assemblages are preserved as casts and molds in sandstone (‘Ediacara-style preservation’). However, the means by which these assemblages became fossilized have long been poorly constrained.

I will present new paleoecological and taphonomic findings for the Ediacara Biota, with a particular emphasis upon reconstruction of the mechanisms responsible for the preservation of Ediacara-style fossil assemblages. On the basis of paleontological, geochemical and petrographic data, I propose that Ediacara-style preservation was due to rapid, early diagenetic precipitation of silica cements. The precipitation of these silica cements was likely facilitated by the high dissolved silica concentrations of the oceans prior to the appearance of prolific silica biomineralizers (silicifying sponges, radiolarians and diatoms). Ediacara-style preservation appears to have been ubiquitous across a wide range of morphologically disparate groups, demonstrating the importance of a pervasive and persistent environmental control on Ediacara fossilization. These findings confirm that Ediacara-style fossil assemblages can indeed be used to reconstruct the diversity and ecology of the oldest complex ecosystems, and indicate that the apparently sudden appearance and disappearance of the Ediacara Biota in the geologic record are real biostratigraphic signals and not preservational artifacts.