Geological evidence for the Anthropocene—Response

Abstract

Certini and scalenghe and Lewis and Maslin seem convinced that geoscience must rely heavily on formal stratigraphic nomenclature to move forward. This view likely originates from the centuries-long effort to compile the relative geologic age sequence, which was a monumental achievement, especially given religious and social opposition. The compilation required careful attention to stratigraphic principles such as superposition, index fossils, diachroneity, and facies changes. Over time, the findings became formalized in geologic nomenclature. However, since the mid-1900s, geochemical (radiometric) dating has increasingly overshadowed (although not replaced) those time-honored principles. In my experience, most geoscience papers in recent decades initially refer to geologic nomenclature as a way of providing a familiar frame of reference, but they soon shift focus to the best geochemical dating available. Although my view will displease some geological colleagues, isn't it time to acknowledge that almost all dating of geological sequences now takes place in the “geochemical age” (with a small “a”)? Lewis and Maslin propose that we designate a “Paleoanthropocene” (capital “P”). Should we place its start at the mass extinction of marsupials in Australia near 50,000 years ago? Or should we choose the mass extinction of large mammals in the Americas almost 40,000 years later? Or, if we decide to pick a level during the 10,000 years or more when crops and livestock were being domesticated and agriculture was spreading across the continents, which one time within that long span should we use for a formal designation? Could any choice be satisfying, given that it would have to ignore the rest of the long and rich history of early human influences? In contrast, informal use of these terms (anthropogenic, anthropocene, and paleoanthropocene) would present no such problems or constraints.