Singhbhum Craton: Where India Keeps Earth’s Oldest Life

The rock comes from a place called Bhitardari. It lies in the Singhbhum Craton of eastern India. The craton spans parts of Jharkhand and Odisha.

• The rock is a chert with black and white bands.
• Its black bands are rich in carbon. Scientists say the carbon came from microbes, tiny living cells.
• The study appeared in PNAS in late August 2026 (ScienceAlert).
• The team included Trisrota Chaudhuri of the Geological Survey of India, Kolkata.
• It also included Mark Harrison of the University of California, Los Angeles.
• The authors call it the oldest directly dated rock with a confirmed biosignature (The Hindu).

Here is the puzzle. Chert is very good at keeping old carbon safe. But chert itself cannot be dated directly. So how did the team find its age?

Zircon: a clock inside the rock

• A zircon crystal traps a little uranium when it forms.
• Over time, the uranium slowly turns into lead, at a known, steady rate.
• Measure how much lead has built up. That tells you the crystal’s age.
• This method is called uranium-lead dating.

What the zircons said

• The team tested eight zircons from the chert.
• Four gave the same age: 3,497 million years.
• These zircons seem to come from volcanic ash. The ash settled while the chert was forming.
• So the ash and the chert are the same age. That is why the rock is called “directly dated”.

There are no bones or shells this old. The first life was made of single cells. So scientists look for chemical clues instead.

Clue 1: a carbon fingerprint

• Carbon comes in a light form, carbon-12, and a heavy form, carbon-13.
• Living cells prefer the light form when they take in carbon.
• So carbon made by life has extra carbon-12. The Bhitardari carbon has this pattern.
• The pattern hints at a way of fixing carbon like the Calvin cycle, used by plants today.

Clue 2: layers like a microbial mat

• The rock has thin, repeating layers of silica and carbon.
• They look like the remains of a microbial mat, a thin sheet of microbes.
• Tests also showed the carbon is old, broken-down living matter. It is not later dirt that crept in.

Older rocks have fossils of mats too

• Microbial mats can build layered mounds called stromatolites.
• Some still grow today, like the ones in the photo above.
• Stromatolites are among the oldest fossil evidence of life.

Think of a continent as an old house. Rooms get added and pulled down over time. But the foundation stays put. A craton is like that foundation.

• A craton is an old, stable part of a continent.
• It has deep roots that go far down into the Earth.
• Cratons hold the oldest rocks on any continent.
• Most formed in the Archaean eon, from 4 to 2.5 billion years ago.
• The word comes from the Greek kratos, which means “strength”.

India’s five cratons

• India has five main Archaean cratons: Dharwar, Bastar, Singhbhum, Bundelkhand and Aravalli.
• Dharwar, in the south, is one of the oldest and the largest.
• Singhbhum sits in the east, under Jharkhand and Odisha.

Singhbhum has fascinated geologists for a long time. It keeps some of the oldest rocks in India. And it keeps telling new stories about the young Earth.

Its oldest parts

• Its oldest rocks are called the Older Metamorphic Group.
• The Singhbhum Granite formed in stages, about 3.4 to 3.1 billion years ago.
• Some zircon grains here are 4.2 to 4.0 billion years old. So crust formed here more than 4 billion years ago.

One of the first beaches

• In 2021, a study looked at Singhbhum’s old sandstones (The Conversation).
• The sand was laid down about 3 billion years ago on beaches and in rivers.
• So land had risen above the sea here by then. It may be among Earth’s first dry land.

India’s iron store

• The craton holds banded iron formations, called the Iron Ore Group.
• Big mines like Kiriburu-Meghahatuburu in West Singhbhum, Jharkhand, dig out this ore.
• The Kiriburu-Meghahatuburu deposit holds over 150 million tonnes of hematite.
• Bhitardari itself lies in the Eastern Iron Ore belt of the craton.

The Earth formed about 4.54 billion years ago. The Bhitardari microbes lived about a billion years later. That is quite early in Earth’s story.

• If microbes were already common by then, life must have started even earlier.
• These microbes may already have had a smart way to fix carbon.
• So life may not be a rare accident. It may start easily on any planet with the right conditions.
• That idea guides the search for life on Mars and beyond.