The issue of erecting a new stratigraphic Epoch encompassing the time since humans had a global effect on the Earth System has irked me ever since the term emerged for discussion and resolution by the scientific community in 2000. An Epoch in a chronostratigraphic sense is one of several arbitrary units that encompass all the rocks formed during a defined interval of time. The last 541 million years (Ma) of geological time is defined as an Eon – the Phanerozoic. In turn that comprises three Eras – Palaeozoic, Mesozoic and Cenozoic. The third level of division is that of Periods, of which there are 11 that make up the Phanerozoic. In turn the Periods comprise a total of 38 fourth-level Epochs and 85 at the fifth tier of Ages. All of these are of global significance, and there are even finer local divisions that do not appear on the International Chronostratigraphic Chart . If you examine the Chart you will find that no currently agreed Epoch lasted less than 11.7 thousand years (the Holocene) and all the others spanned 1 Ma to tens of Ma (averaged at 14.2 Ma). Indeed, even Ages span a range from hundreds of thousands to millions of years (averaged at 6 Ma).
In the 3rd week of May 2019 the 34-member Anthropocene Working Group (AWG) of the International Commission on Stratigraphy (ICS) sat down to decide on when the Anthropocene actually started. That date would be passed on up the hierarchy of the geoscientific community eventually to meet the scrutiny of its highest body, the executive committee of the International Union of Geological Sciences, and either be ratified or not. In the meantime the AWG is seeking a site at which the lower boundary of the Anthropocene would be defined by the science’s equivalent of a ‘golden spike’; the Global boundary Stratotype Section and Point (GSSP). Continue reading “Anthropocene edging closer to being ‘official’”
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