December 18th, 2025

   As profound gap in the stratigraphic record that frequently spans the boundary between the Phanerozoic and the Proterozoic, the Great Unconformity has been recognized for well over a century, but long dismissed as anything from an intractable problem to merely an unremarkable consequence of normal tectonic processes. In this talk, we will consider both the varied and sometimes contradictory usage of the term, as well as some aspects of the current debate about the significance and origin of the underlying geological phenomena, including evidence spanning from stratigraphy to geochemistry to thermochronology.