A groundbreaking study of ancient rocks in the Vizianagaram-Salur region of Andhra Pradesh has provided the 'smoking gun' evidence that India and Antarctica were once physically joined as a single, massive mountain belt known as the Rayner-Eastern Ghats orogen. The Rayner Province is located in present-day East Antarctica.
Shared Geological History
Researchers found that rocks in the two regions share the same age, chemical signatures, and mineral composition. They also discovered that the rocks underwent the same three stages of geological history, providing strong evidence that eastern India and East Antarctica were once connected before drifting apart millions of years ago.
Research Team and Methods
The research team included Shubhadeep Roy, Sankar Bose, Sayantika Ghosh, Sneha Mukherjee, Nilanjana Sorcar, and J Amal Dev from Presidency University, Kolkata; Queensland University of Technology, Australia; National Centre for Earth Science Studies, Thiruvananthapuram; and Korea Polar Research Institute, Republic of Korea. The researchers studied rocks called granulites, a type of metamorphic rock formed deep inside the Earth under extreme heat and pressure. These rocks preserve a record of ancient events that took place deep within the Earth's crust.
Tiny Crystals, Massive Clues
Prof Sankar Bose, dean of the faculty of natural and mathematical sciences at Presidency University, said the team examined minerals such as zircon, garnet, and monazite in Vizianagaram-Salur using advanced mineral analysis techniques. 'Notably, zircon is renowned for its durability under extreme heat and pressure, which can obliterate other minerals. Due to this robust nature, zircon acts as a tiny time capsule within these rocks. The decay of radioactive elements like uranium and lead within zircon crystals enabled us to construct a detailed timeline, pinpointing events that unfolded hundreds of millions to billions of years ago in the Eastern Ghats province,' said Prof Bose.
Three Stages of Geological History
The rocks from Vizianagaram and Salur recorded the same three major stages of geological history identified in East Antarctica. The first stage occurred around 1,000 to 990 million years ago, when the rocks were exposed to ultra-high temperatures of about 1,000 degrees Celsius deep within the Earth's crust. As the landmasses that would become India and Antarctica collided, they created the Rayner-Eastern Ghats orogen.
The second stage took place between about 950 and 890 million years ago, a period of reworking where rocks were heated again or buried deeper, altering their mineral structures. Such a long and complex history is typical of major mountain belts formed by continental collision.
The third stage occurred between about 570 and 540 million years ago, when chemically rich fluids moved through cracks and layers in the rocks, leaving a distinct chemical fingerprint. Researchers believe this was linked to distant tectonic forces associated with the assembly of Gondwana. 'Even if the main collisions were happening elsewhere, the stress and fluid movement reached this region and altered the rocks in a recognisable way. The same fluid-related signature appears in both the Indian and Antarctic samples, strengthening the case that they shared the same geological history,' added Prof Bose.
The Great Breakup and Drifting Continents
Around 130 to 150 million years ago, during the age of dinosaurs, the supercontinent Gondwana began to break apart. A giant rift opened and gradually widened into what became the Indian Ocean. India began drifting northward towards Asia, while Antarctica moved southward towards the pole. The once-connected mountain belt was split apart and carried away on separate continental plates. Today, thousands of kilometres of ocean separate the two regions, but the rocks preserve the same deep-time geological record.
Why This Matters
'The ground beneath Eastern Ghats today may seem stable, but these rocks tell a story of extreme heat, deep burial, chemical change, and continental travel across a billion years. They survived temperatures near 1,000 degrees Celsius, were altered more than once, and later became part of a landmass that drifted far from its ancient twin in Antarctica,' said Prof Bose. By piecing together this 'geological clock', scientists can better predict how current geological processes might unfold, which is essential for managing natural resources and assessing geological risks such as earthquakes.
