An ocean at the top of the world
In the high-altitude cold desert of Spiti Valley, villages like Langza sit at elevations around 4,400 meters. Here, the thin air and barren slopes hold a deep geological secret: the ground is littered with the fossilized remains of marine animals. These fossils are tangible proof that the rock beneath the Himalayas was once the floor of an ancient sea. This body of water, known as the Tethys Sea, separated the supercontinents of Gondwana and Laurasia for millions of years.
The existence of a sea floor at this altitude results from one of the most powerful geological events on Earth. Around 50 million years ago, the landmass that is now the Indian subcontinent, having broken away from Gondwana, completed its journey northward and collided with the Eurasian continent. The immense pressure of this tectonic collision buckled and folded the Earth's crust, thrusting the sedimentary layers of the Tethys seabed thousands of meters into the sky. This process, which is still ongoing, created the Himalayan mountain range. The fossils found here are the physical record of a lost ocean and the birth of the world's highest mountains.
Creatures of the Cambrian sea
The most significant fossils in Spiti are found within a thick sequence of sedimentary rock called the Haimanta Group, specifically in layers like the Kunzam La Formation and the Parahio Formation. These rock beds date to the Cambrian Period, between 541 and 485 million years ago. They contain many trilobites, an extinct group of marine arthropods that were wildly successful during the Paleozoic Era.
Specific species identified in Spiti include Oryctocephalus indicus and Bhargavia prakritika. The presence of trace fossils—preserved tracks and burrows such as Diplichnites (trilobite walking trails) and Rusophycus (trilobite resting pits)—shows the behavior of these ancient creatures. Alongside the trilobites, fossils of other marine invertebrates like brachiopods and echinoderms are also present. The particular assemblage of trilobite species in Spiti shows strong similarities to fossils found in North America, southern China, and Australia, helping paleontologists reconstruct the configuration of continents during the Cambrian and providing strong evidence for the existence of the Gondwana supercontinent.