Part 2: Descriptions of the proposed Crawford Lake GSSP and supporting SABSs. The Anthropocene Epoch and Crawfordian Age: proposals by the Anthropocene Working Group

Abstract

This part of the Anthropocene Working Group (AWG) submission proposes that the base of the Anthropocene should be defined as series/epoch, terminating the Holocene Series/Epoch with a single Crawfordian stage/age using a Global boundary Stratotype Section and Point (GSSP) in an annually varved Crawford Lake core, Ontario, Canada, defined at 17.5 cm in core CRA23-BC-1F-B at the base of the dark lamina in a varve deposited in 1952 CE, at the level where the primary marker shows a rapid increase in 239+240Pu concentrations (coinciding with a globally recognisable, isochronous signal of the first above-ground thermonuclear tests). Secondary markers, determined in precisely correlated core closely adjacent to the proposed GSSP host, include a marked increase in 14C values and in spheroidal carbonaceous particles (SCPs), increased heavy metal concentrations, a decline in δ15N values, a marked change in phytoplankton assemblages and declines in elm (Ulmus) pollen and in non-arboreal pollen. The submission also provides descriptions of three proposed Standard Auxiliary Boundary Stratotypes (SABSs), in cores extracted from marine anoxic sediments of Beppu Bay (Japan), in Sihailongwan Maar Lake (China) and in the Śnieżka Peatland (Poland) and eight reference sections located in cores extracted from marine anoxic sediments in the Baltic Sea, from coral bioherms off Australia and in the Gulf of Mexico, from an Antarctic ice core, from San Francisco Estuary and nearby lake (USA), in a speleothem from northern Italy and a section in urban anthropogenic deposits in Austria. This ubiquity of signals verifies that the Anthropocene can be widely delineated as a sharply distinctive chronostratigraphic unit in diverse terrestrial and marine depositional environments, and reflects a major Earth System change that will have geologically lasting consequences.