Reacción a "Reactions to the proposal of Crawford Lake in Canada as a geological reference site for the Anthropocene "

Is the selection supported by solid data?  

"The data supporting the nomination are based on a series of short drilling holes taken at the bottom of a lake with exceptional conditions for recording all kinds of environmental fluctuations, and using state-of-the-art ultra-high resolution analytical techniques. It is a small lake, developed in a doline of karstic origin, with a maximum depth of 24 m, with stratified and oxygenated water, where varved sediments are deposited with remains of pollen and microorganisms that testify to geochemical and organic changes. Anthropocene sediments are restricted to the upper 10-13 cm of all boreholes, affected by all kinds of anthropogenic contaminants from a neighbouring highly industrialised region.  

The work and site selection is sound: this half-span of Anthropocene sediments preserves all the stratigraphic indicators of a geologically changed horizon. Another matter is whether the formal range is that of an epoch. F,or example in the Devonian there are planetary-scale oceanographic events that occur within geological floors and are highly detectable; however, they do not mark formal geochronological boundaries. The history of the planet is a succession of geological changes and the Anthropocene is not geology. It is more like the old theological-philosophical concepts of the Anthropozoic era or the Anthropogenic period, which did not make it into geology because of their unscientific character.  

Are there any major limitations to be taken into account?  

"The boreholes provide an ideal sequence of events recorded in the sediments, which has taken many years to be found. But as a standard scale, the detection of such a small Anthropocene requires a sum of specialists and sophisticated technologies that do not make it cost-effective in any case. And then there are indicators that disappear over time, such as radioisotopes from nuclear explosions: the plutonium detected in some Lake Crawford shafts has a half-life of 24,100 years, and will cease to be detectable after 100,000 years, almost irrelevant on the geological scale.  

What impact might this selection have (or not), for geology and beyond?  

"Those of us who believe that the Anthropocene is a geological event, the result of the diachronic impact of human activity on our own ecosystem, are not in favour of giving it a start date, much less of formalising the term on a geological scale measured in thousands to millions of years, in order to create a forward-looking and ultimately guilt-ridden unit by trying to make it the geological expression of a global change of anthropogenic origin. This is why the Anthropocene should continue to be treated as a meta-concept that can be used by all kinds of thinkers, artists and scientists, and I find it ridiculous that a minority elite of geologists insist on putting the concept of the Anthropocene in the context of a global change of anthropogenic origin.”