Prof. Francine McCarthy
Earth Science, Brock University
Why propose a GSSP for the Anthropocene in a freeze core from Crawford Lake, Canada? What's so special about this lake?
In 2009, the International Subcommission on Quaternary Stratigraphy commissioned a working group to investigate atmospheric chemist Paul Crutzen's claim that we were no longer living in a Holocene world, and whether the Anthropocene had substance as a new epoch of geological time. Over the subsequent decade, Anthropocene Working Group (AWG) members scoured the literature and debated the existence of, and merits of various potential bases for, this possible new epoch, beginning with the Industrial Revolution and specifically, Watts’ steam engine, as Crutzen had suggested. The AWG recognized substantial transition away from the Holocene state, driven by multiple factors including anthropogenic emissions of CO2, an altered state that is likely to persist for at least 50,000 years, but with a globally synchronous base in the mid-20th century, with the main shift in trajectory of the Earth System attributed to the Great Acceleration. With support from the Haus der Kulturen der Welt, twelve widely geographically distributed geological successions from a variety of depositional settings were investigated as potential GSSP candidates to define an Anthropocene epoch/ series, all of which recorded evidence of a substantial globally synchronous shift during the 1950s. In April 2023, a supermajority of AWG members selected the varved sediments of the meromictic Crawford Lake as best representing the departure of conditions from Holocene norms, with the coincident rise in plutonium fallout from aboveground nuclear weapons testing as the primary chronostratigraphic marker.