600-million-year-old stromatolites in the Himalayas tell the story of a lost ocean and Earth's first breath

Indian Express

28-05-2025

Long before dinosaurs thundered across continents and ferns began unfurling in prehistoric forests, it was microscopic life that set the Earth on its path to habitability. Stromatolites, reef-like structures built by ancient cyanobacteria in shallow seas, document this evolution. Found across India — from the Vindhyas and Cuddapah Basin to the limestone ridges of the Himalayas — these mineralised mounds chronicle a time when oxygen did not yet exist, and continents had not yet collided.
Now, a large outcrop of these stromatolites — dating back 600 million years — recently unearthed in the pine-clad ridges of Chambaghat in Solan district has sparked renewed calls for preservation and public engagement with India's geological heritage.
Dr Ritesh Arya, geologist and founder of the Tethys Fossil Museum, in Kasauli, stumbled upon these arched, hemispheroid structures during a pre-dawn walk.
These ancient structures offer a window into a time when Earth's atmosphere was dominated by greenhouse gases, and oxygen was nonexistent. Their presence in the Himalayas, far from any current coastline, reveals a story of tectonic shifts, lost oceans, and the microbial origins of life.
It took billions of years for the Earth to become habitable for humans, primarily due to the absence of oxygen in its atmosphere.
'Oxygen was absent from the Earth's atmosphere for close to half of its lifespan,' writes Kartik Aiyer, a researcher at the Center for Electromicrobiology at Aarhus University, in his 2022 paper, The Great Oxidation Event: How Cyanobacteria Changed Life.
When the Earth was formed around 4.5 billion years ago, the atmosphere consisted of carbon dioxide, methane, and water vapour, as opposed to the present-day atmosphere that consists primarily of nitrogen and oxygen. 'Though sunlight split the water vapor in the atmosphere into oxygen and hydrogen, the oxygen quickly reacted with methane and got locked into the earth's crust, barely leaving any traces in the atmosphere,' writes Aiyer.
Ancient microbial mats, primarily composed of blue-green algae or cyanobacteria, trapped and bound sediment over time, forming layered, reef-like mounds.
'Stromatolites are biosedimentary structures produced in shallow marine seas built by blue-green algae. The structure has been retained, but the algae is dead,' says Dr Arun Deep Ahluwalia, former professor of geology at Panjab University.
As oxygen began accumulating in the atmosphere, thanks to these early cyanobacteria, the Earth transitioned from anaerobic to aerobic conditions, paving the way for multicellular life. 'Around 3.5 billion years ago, the only organisms surviving were single-celled microbes that created oxygen. After stromatolites, created by cyanobacteria or blue-green algae, began producing oxygen, Earth's atmosphere transformed, allowing multicellular life to evolve. This remarkable journey, preserved in our geoheritage, led to the rise of trilobites, dinosaurs, and eventually, modern humans,' says Dr Arya.
This increase in oxygen levels in the atmosphere and oceans, which took place around 2.4 billion years ago, was called the Great Oxidation Event or Oxygen Catastrophe.
Dr Ahluwalia draws a distinction between fossils and stromatolites: 'If the original organism is preserved, I technically call it a fossil. But if only the outline is preserved, I'd rather call it a biosedimentary structure.'
The stromatolites at Chambaghat lie within the Krol Group of sedimentary rocks, comprising limestone, shale, and sandstone, formed in a shallow marine environment of what was once the Tethys Sea. 'These stromatolite-bearing formations were laid down in a shallow marine sea called the Tethys Sea, before India collided with Tibet and the sea was squeezed out,' says Dr Ahluwalia.
This region was once part of Gondwana, the southern supercontinent that included India, South America, Africa, and others. The Indian plate's northward drift and collision with Eurasia lifted marine sediments, including stromatolites, thousands of meters skyward. Arya notes, 'These are shallow marine deposits that we're finding at the height of 5,000-6,000 feet above sea level.'
'Above the Precambrian-Cambrian boundary, around 543-548 million years ago, you find abundant body fossils. Below that, you get organo-sediment structures built by blue-green algae,' Dr Ahluwalia says.
What sets Chambaghat apart is the scale and accessibility of the find. We're not talking about a few samples,' says Arya. 'We've found a whole hill. In India, we often find stromatolites that are 1.5 billion years old, but this outcrop is at least 600 million years old, and could be even older.'
Dr Jagmohan Singh, former chief general manager at ONGC, says: 'It is one of the oldest fossils, they indicate the beginning of life as a single cell, right from the first cell, and while we found such structures in Jhamarkotla in Rajasthan, a whole hillock has been found in Solan.'
However, not all scientists agree. Dr Vibhuti Rai, sedimentologist and paleontologist at the University of Lucknow, says, 'To tout these structures as fossils is inaccurate. These are not true fossils. Stromatolites are organo-sedimentary structures formed from the entrapment of calcium carbonate precipitates by algae and cyanobacteria. To call these a significant or rare discovery is a hoax, as they are found all over India. These are, in fact, the most common geological structures that can occur. In fact, the oldest stromatolites are found in Dharwad in Karnataka, which are at least 2,500 million years old.'
The oldest stromatolites are 3.6 billion years old and are found in Australia.
Dr Ahluwalia, however, offers context: 'While the outcrop is magnificent in preservation and can be used as a stromatolite exhibit, it is by no means a new discovery, and it's not the oldest evidence of life. In fact, the stromatolites in the Krol Belt are the youngest stromatolites.'
India has other stromatolitic sites — the Bhima Basin in Karnataka, the Aravalli Supergroup, and the Kadapa mountains of Madhya Pradesh, among them. 'The older stromatolites are found in the Shali-deoban area in the Himalayas,' says Dr Ahluwalia. 'The younger stromatolites exhibit a gentle arc and are laminated and hemispheric, the older ones are branching the columnar. The exhibit in Solan falls in the former category.'
'Geologists find stromatolites, write a paper, and then store them away in obscure departments,' Arya says, drawing attention to the need to preserve these structures. 'There's no access for locals, tourists, or even many researchers.'
He is advocating for the creation of a Geoheritage Park at Chambaghat to preserve these structures, involving schools, tourism bodies, and the community. 'These rocks should be our teachers,' he says. 'Children should grow up with a sense of wonder that they live near rocks that helped create the oxygen we breathe.'
While most of the hill is government land, some areas are privately owned. Arya is appealing to district authorities for support and hopes to seek UNESCO heritage status.
Professor Ashok Sahni, former INSA scientist, agrees with Arya's assessment: 'The Chambaghat stromatolites signify an important event in Earth history. These cyanobacteria used photosynthesis to produce oxygen. As the oxygen levels grew in the atmosphere, the rise of more complex life was possible.'
Arya's plea is not isolated. Across India, other geological marvels face similar neglect. In Rajasthan, the sites of Jhamarkotra and Zawar are powerful reminders of what's at stake. At Jhamarkotra, a fossil park hosts 1.8-billion-year-old stromatolites, yet lies largely unprotected. Its phosphate-rich rocks have drawn mining interests, but at a cost. Mining has exposed some stromatolites, yet without formal safeguards, scientific treasures risk being lost to bulldozers. For now, local villagers and acacia trees are the only custodians, as per a 2023 article in The Hindu.
As Arya puts it, 'The coral-like environment in these hills reminds one of Goa, but it's on a mountain.' The site tells a layered story of life on Earth, one that demands to be preserved before erosion, construction, or neglect erase it forever.
📌Chitrakoot, Uttar Pradesh – Known for columnar stromatolites in Vindhyan limestones.
📌Morni Hills, Haryana – Features well-preserved stromatolite beds in dolomite formations.
📌Mussoorie and Nainital, Uttarakhand – Sites in the Krol Belt showcase Precambrian marine sedimentation.
📌 Jaisalmer Fossil Park, Rajasthan – A protected area highlighting a range of Mesozoic fossils, including marine life.
📌 Jhamarkotra, Rajasthan – Hosts 1.8-billion-year-old stromatolites in phosphate-rich rocks under mining threat.
📌 Zawar, Rajasthan – Ancient zinc-smelting site near stromatolitic formations, reflecting metallurgical and geological heritage.
📌 Dharwar Supergroup, Karnataka – Neoarchean stromatolites in the Chitradurga schist belt, over 2.6 billion years old.
📌 Bhima Basin, Karnataka – Precambrian stromatolites preserved in shallow marine limestones.
📌 Shali-Deoban, Himachal Pradesh – Older columnar and branching stromatolites predating those in the Krol Belt.
📌 Kadapa Basin, Andhra Pradesh & Madhya Pradesh – Proterozoic stromatolitic limestones in the Cuddapah Supergroup.
📌 Sikkim – Stromatolite-bearing dolomites from the Buxa Formation, a declared Geoheritage site.
📌 Bhojunda, Rajasthan – National Fossil Park with stromatolites from the Lower Vindhyan range.
📌 Salkhan, Uttar Pradesh – Fossils of 1.4-billion-year-old stromatolites spread over a large public fossil park.
📌 Chandi Formation, Chhattisgarh – Mesoproterozoic stromatolites preserved as bioherms and biostromes.
📌 Bilara Group, Rajasthan – Exceptionally preserved Ediacaran stromatolites in the Marwar Supergroup.
📌 Sikkim – A new fossil park under development to highlight regional stromatolite finds.
Aishwarya Khosla is a journalist currently serving as Deputy Copy Editor at The Indian Express. Her writings examine the interplay of culture, identity, and politics.
She began her career at the Hindustan Times, where she covered books, theatre, culture, and the Punjabi diaspora. Her editorial expertise spans the Jammu and Kashmir, Himachal Pradesh, Chandigarh, Punjab and Online desks.
She was the recipient of the The Nehru Fellowship in Politics and Elections, where she studied political campaigns, policy research, political strategy and communications for a year.
She pens The Indian Express newsletter, Meanwhile, Back Home.
Write to her at [e-mail] or [e-mail]. You can follow her on Instagram: @ink_and_ideology, and X: @KhoslaAishwarya. ... Read More