The Anthropocene golden nail may have been Lake Crawford in Canada

According to “Nature” news, on July 11, local time, the Anthropocene Working Group announced at the stratigraphic conference in Lille, France, and a press conference in Berlin: the official symbol of the beginning of the Anthropocene is Lake Crawford in Canada. If the proposal is approved, the sediment core of Lake Crawford would be the golden nail that marked the beginning of the Anthropocene.

Lake Crawford, Canada, has been proposed as the official site marker for the Anthropocene Golden Nail. Image source: Brock University, Canada

The Anthropocene is a geological era in which humans profoundly influenced the planet, and researchers have spent 14 years discussing when and how humans began to change the planet. Year after year, particles settle into the lake and drift to the bottom of the lake, forming layers of sediment that record environmental conditions. Among the embedded contaminants are fly ash particles from burning fossil fuels, as well as traces of radioactive plutonium from atmospheric nuclear bomb tests. Researchers have captured chemical traces of radioactive fallout from nuclear bombs and other forms of environmental degradation in the lake sediments.

Not all geoscientists agree with the idea of the golden nail of the Anthropocene. They argue that tying the beginning of this era to the most recent time and place ignores the idea that humans have been changing the planet over a longer period of time.

“European scientists seem fascinated by the fact that this period has only recently begun.” Zoe Todd, an anthropologist at Simon Fraser University in Canada, says that for indigenous people and other displaced and dispossessed people affected by mass violence over the past 600 years, everything that led to this global shift actually began much earlier.

But proponents say formalizing a new era has powerful symbolic value. Colin Waters, a geologist at the University of Leicester in the United Kingdom who chairs the Anthropocene Working Group and chairs the Anthropocene Working Group, said the Anthropocene golden nail is not intended to acknowledge the beginning of human activity on Earth, but to mark the Earth’s response to dramatic changes.

In 2019, the Anthropocene Working Group began discussing a shortlist of Golden Nail sites, from peat bogs in Poland to coral reefs in Mexico. Earlier this year, the group narrowed the list to two shortlists: Sihailongwan Lake and Lake Crawford in northeastern China. In April, Lake Crawford received 60 percent of the working group’s approval votes, earning it the title of candidate Golden Nail.

Both lakes have sedimentary layers every year, recording changes in the environment over time. Han Yongming, a geochemist at the Institute of Earth Environment of the Chinese Academy of Sciences, pointed out that unlike Crawford Lake, Sihailong Bay is relatively undisturbed by local influences and therefore contains a broader record of changes.

Although the surface area of Lake Crawford is only 2.4 hectares, it is 24 meters deep, so the water from the bottom cannot be mixed with the water in the upper layer. It was formed when a limestone cave collapsed and water flooded the cave. Every summer, the lake warms and calcium carbonate precipitates out and sinks to the bottom, forming a distinctive white layer that serves as a visual sign of the passage of time.

These layers recorded rising levels of radioactive plutonium fallout from nuclear bomb tests. Cores collected in Crawford in 2019 and 2022 showed that traces of plutonium increased in the early 2050s, but the team of Francine McCarthy, a microsomal paleontologist at Brock University in Canada and leader of the Anthropocene Working Group, collected additional cores this year for more detailed analysis. They found that the year of the golden nail could be 1950 (when some environmental changes accelerated) or 1952 (when plutonium levels rose sharply).

In the coming months, the working group will present three ideas to the Quaternary Stratigraphy Subcommittee. First, Lake Crawford should serve as a golden nail for the beginning of the Anthropocene, the exact year of which has yet to be determined. Second, the Anthropocene should become a geological epoch that ends the Holocene, the first of which may be named the Crawford Epoch. Finally, some candidate sites that did not receive the title of Anthropocene Golden Nail could be supplemented to help identify the Anthropocene in different geological settings.

If the proposal passes the next round of voting, it will be submitted to the International Committee of Stratigraphy and finally to the International Union of Geological Sciences. Any part of the proposal can fail in any round. (Source: China Science News Xin Yu)

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