Ongoing debates in the Earth, planetary, and social sciences examine the merits and implications of traces in the stratigraphic record that would indicate that humans are now one of the 'great forces of nature'. Candidates for key marker horizons in such a stratal section include noted changes in carbon and nitrogen concentrations, plastics, radionuclides, and metals. Candidates for determining calendar age, include the tipping point in land cover from wildlands to agriculture and the first nuclear detonation. Here we offer a critical review of recent literature contributing to delineating an Anthropogenic stratum, by exploring their interpretation as initiating, sustaining, or indeed ending an Anthropocene epoch. We also offer a reflection on the layer not representing a new period, any more than, for instance, iridium marks a 'meteoritic' epoch between the Cretaceous and Palaeogene. We examine temporal scales for their accord with geological methods of definition and delineation, and for the opportunities and constraints each presents for understanding and responding to transformations in the Earth system. Our thesis is that increasingly fortified stances on the 'right' definition of the Anthropocene epoch follow traditions of linear and authoritarian historical accounts, and prevent discovering epistemes of human-environment interactions that are open for coexistence. The co-existence of many key transitions will sustain ongoing and fruitful deliberations over human-environment interactions that the Anthropocene proposal has initiated, promoting research that can work with the many scales, discourses, and narratives of environmental change. (C) 2016 Elsevier Ltd. All rights reserved.
