The Anthropocene: an overview of geological assessment to date
This presentation outlines the work of the Anthropocene Working Group in gathering evidence to constrain and assess the Anthropocene as a potential new formal chronostratigraphic unit within the Geological Time Scale. Evidence includes the appearance and rapid dispersal of many new mineral forms (including metals, plastics and industrial fly ash), rock types (including concrete) and sediment bodies including artificial ground, together with sediments released by land use changes. Humans now move more terrestrial sediment than all natural fluxes by rivers, wind, and glaciers. Chemostratigraphic evidence includes isotope patterns altered by perturbations to the carbon, nitrogen and phosphorus cycles at rates and magnitudes unprecedented in Quaternary times, atmospheric gas changes preserved in ice, disseminated metal and persistent organic pollutant and artificial radionuclides traces, many of which are novel signatures. Biostratigraphic evidence includes the consequences of extinctions, geologically unprecedented species invasions and marked assemblage changes. Recent climate and sea level trends are outside the Holocene trajectory, though global temperature and sea level are still within the Quaternary interglacial envelope. Anthropogenic influence on stratigraphic signals commenced thousands of years ago, but the most pronounced inflection in most trends away from Holocene patterns is in the mid-20th century. Attempts at definition through the selection and detailed multiproxy analysis of candidate GSSP (‘golden spike’) sections, with potential candidates in marine anoxic basins, corals, lakes, glacial ice, speleothems and trees will be introduced.