An international team of researchers has chosen Lake Crawford (Canada) as the place that best represents the beginnings of what could be a new geological epoch, the Anthropocene.
The Anthropocene Working Group has proposed Crawford Lake as a Section and Global Boundary Stratotype Point (GSSP) for the Anthropocene. A GSSP is an internationally agreed reference point to show the beginning of a new geological period or epoch in layers of rock that have accumulated over centuries.
Some geologists have proposed that we live in the Anthropocene, a new geological epoch in which human activity has become the dominant influence on the planet's climate and environment.
The concept has important implications for how we think about our impact on the planet, but there is disagreement in the scientific community about when the Anthropocene began, how it manifested itself, and whether human influence has been substantial enough to constitute a new geological era. , which usually spans millions of years.
To help answer these questions, the International Commission on Stratigraphy (ICS) created the Anthropocene Working Group.
"Sediments found at the bottom of Crawford Lake provide an exquisite record of recent environmental change over the last few millennia," says Dr Simon Turner, Secretary of the Anthropocene Working Group at University College London (UCL), UK. United.
"Seasonal changes in water chemistry and ecology have created annual layers that can be sampled for multiple markers of historical human activity," he continues. "It is this ability to accurately record and store this information as a geological archive that can be compared to historical global environmental changes that make places like Crawford Lake so important."
He adds that "a GSSP is used to correlate similar environmental changes observed in other sites around the world, so it is essential to have a robust and reproducible record in this type of locality."
The team has assembled sections of core samples from various environments around the world, from coral reefs to ice sheets. Samples from these locations were sent for analysis to the GAU-Radioanalytical Laboratories of the University of Southampton, at the National Oceanography Center in Southampton, UK. There, the researchers processed the samples to detect a key marker of human influence on the environment: the presence of plutonium.
Professor Andrew Cundy, Professor of Environmental Radiochemistry at the University of Southampton and a member of the Anthropocene Working Group, says: "The presence of plutonium gives us a clear indicator of when humanity became such a dominant force that it was able to leave a unique global 'fingerprint' on our planet".
He explains that "in nature, plutonium is only present in trace amounts, but in the early 1950s, when the first hydrogen bomb tests were carried out, there was an unprecedented increase in plutonium levels in samples of around the world. Since the mid-1960s, when the Nuclear Test Ban Treaty came into force, plutonium has been declining," he adds.
Other geological indicators of human activity include high levels of ash from coal-fired power plants, high concentrations of heavy metals such as lead, and the presence of fibers and plastic fragments. All this coincides with 'The Great Acceleration', a spectacular increase in human activities, from transport to energy use, which began in the mid-20th century and continues today.
Of the hundreds of samples analysed, the Crawford Lake core has been proposed as the GSSP, along with other secondary deposits showing similar high-resolution records of human impact. The evidence of the deposits will now be presented to the ICS, which next year will decide whether to ratify the Anthropocene as a new geological epoch.
