What are Stromatolites?

Context (IE): 600-million-year-old stromatolites have been discovered in Chambaghat, Solan, HP.

Stromatolites

They are organo-sedimentary structures formed from the entrapment of calcium carbonate precipitates by algae and cyanobacteria (blue-green algae).
They are living fossils and the oldest living lifeforms on our planet. The oldest stromatolites, 3.6 billion years old, are found in Australia.

They represent some of Earth’s earliest life forms, especially prominent during the Precambrian era (about 541 million years ago) before complex life evolved.
They form in shallow marine settings, and some also thrive in intertidal zones, freshwater ponds, and lagoons.
They are characterised by alternating light & dark bands; size can vary from a few millimetres to a meter; they typically appear flat, dome-shaped, or columnar.
Living stromatolites are extremely rare, found only in select saline lakes and coastal lagoons, offering a glimpse into extremophile life.
They played a key role in the Great Oxygenation Event, altering Earth’s atmosphere by introducing oxygen.

Chambaghat’s stromatolites are embedded within the Krol Group’s limestone, shale, and sandstone, deposited under the ancient Tethys Sea. As the Indian tectonic plate drifted northward and collided with the Eurasian plate, these marine sediments were uplifted, forming the Himalayas at elevations of 5,000–6,000 feet.

Stromatolites are key to reconstructing ancient ecosystems & understanding Earth’s early biosphere, atmosphere, and evolutionary history.
They are markers of continental drift and mountain-building.
Living stromatolites are relevant to astrobiology & search for potential biosignatures on other planets.

Sikkim: Buxa Formation, a declared Geoheritage site.
Andhra Pradesh, Madhya Pradesh: Kapada Basin (Cuddapah Supergroup).
Haryana: Morni Hills (dolomite formations).
Uttar Pradesh: Chitrakoot (Vindhyan limestones).
Uttarakhand: Mussoorie and Nainital (Krol Belt stromatolites).
Rajasthan: Jaisalmer Fossil Park (Mesozoic stromatolites), Jhamarkotra and Zawar.
Himachal Pradesh: Shali-Deoban (Krol Belt specimens).
Karnataka: Bhima Basin (Precambrian stromatolites), Dharwar Supergroup (Neoarchean stromatolites over 2.6 billion years old).