A bay in south-west Japan could become the place on Earth that geologists use to officially establish the start of the Anthropocene, thanks to an abundance of sardine scales and other evidence revealing humanity’s growing influence on the planet.

Beppu Bay has now formally joined 10 other sites being considered by researchers trying to find the planet’s best candidate for a “golden spike”, a clear signal in Earth’s geological record that can designate a new epoch shaped by human impact.

In 2016, scientists on the Anthropocene Working Group (AWG) voted in favour of a defining new epoch starting around the middle of the 20th century, on the grounds that humanity’s nuclear weapons testing, fossil fuel burning, plastic pollution and other activities were of sufficient scale to push the world into a new geological age.

But the Anthropocene remains just an idea rather than an official epoch until approved by the International Commission on Stratigraphy (ICS), the arbiter of geological timescales.

Gaining approval will involve AWG researchers providing evidence from one location with enough markers to show the start of the Anthropocene. Radionuclides from nuclear weapons tests are thought to be the most obvious marker, but the AWG is seeking a location with multiple indicators to serve as the golden spike, or the global boundary stratotype section and point (GSSP). An ice core from Greenland marks the GSSP for the end of the Pleistocene and start of the Holocene, the current geological epoch.

Read more: Where will we find the first telltale signs of the Anthropocene?

Now a flurry of research from Japan means Beppu Bay is the 11th potential GSSP, up against sites including an Italian cave, a Chinese lake and a coral reef off Australia. “Beppu Bay is a spawning site for sardines in the western Pacific, and researchers have managed to match very nicely the density of sardine scales in the sediment core with written records of sardine catches in Japan over many centuries,” says Colin Waters at the University of Leicester, UK, referring to a 2017 paper.

Simon Turner at University College London says there are a variety of records showing how humans have influenced the sediment record in the bay, notably the acceleration of the use of PCB chemicals post-1950 and the presence of caesium-137 from nuclear weapons tests. Analysis of plutonium isotopes at the bottom of the bay could provide more evidence, he says.

Speaking at the virtual European Geosciences Union general assembly on 28 April, Turner gave an update on the other 10 potential GSSP locations. Teams working on sediment cores from the Baltic Sea and from Searsville Lake in the San Francisco Bay area are two of the furthest ahead for completing work on Anthropocene markers.

Encouragingly for advocates of the new epoch, markers that were expected, such as radionuclides from nuclear bombs, are beginning to line up with other markers for the mid-20th century, such as fly ash from coal power stations, says Turner.

He says geologists are “on track” to propose a start for the Anthropocene based on one of the 11 sites. The plan is for research on the locations to be published in peer-reviewed journals by May 2022, with the AWG voting to decide the winning candidate by late 2022. That site will then be put forward for consideration by the ICS.