THE GEOLOGIC ANTHROPOCENE: ANALYSIS AND CURRENT STATUS

The presently informal term “Anthropocene” was proposed by Crutzen & Stoermer in 2000 as a chronostratigraphic unit at series/epoch rank. This generated interest within the geological community, and in 2009 the Anthropocene Working Group (AWG) was established by the International Commission on Stratigraphy (ICS) Subcommission on Quaternary Stratigraphy (SQS) to explore the potential of the Anthropocene as a formal subdivision of geologic time. The Anthropocene represents a unique overlap of geological, historical and instrumental time, allowing stratigraphic signals to be dated with unparalleled precision. Using an Earth Systems approach to analyze a range of global anthropogenic indicators through historical time, AWG members identified the “Great Acceleration” of the mid-20^th century as the most promising interval in which to define its inception. This interval is represented by distinctive stratigraphic signals that reflect pronounced increases in rates of erosion and sedimentation, chemical perturbations to the cycles of carbon, nitrogen, phosphorus and other elements, production of novel materials, changes to global climate and sea level, and biotic changes that include unprecedented levels of species invasions globally. Many of these changes have left indelible stratigraphic traces including artificial radionuclides, changes to carbon and nitrogen isotope patterns, fly ash particles, and biological remains. Plutonium-239 fallout is a promising primary marker, with global signal inception ~1952. The rank of series/epoch seems the most suitable, signifying that Earth commonly exceeds the natural variability of the Holocene Series/Epoch. The AWG is currently identifying those regions and environments most favorable for studying and ultimately selecting a candidate Global Boundary Stratotype Section and Point (GSSP) to define the Anthropocene base. For the Anthropocene to become an official unit of geological time, the AWG must submit a formal proposal that would require supermajority approval by the voting members of SQS and its parent body the ICS, and then ratification by the International Union of Geological Sciences. The AWG plans to submit such a proposal within the next few years. If approved, this will formally acknowledge the most recent chapter in the narrative of Earth history.