‘Smoking gun’ evidence was found in AP’s granulite rocks, which showed same age and chemistry as those in East Antarctica
VISAKHAPATNAM: Imagine a world where the lush Eastern Ghats of India did not face the Bay of Bengal (Indian Ocean) but instead merged seamlessly into an icy mountain range in Antarctica. For decades, geologists have looked at maps of the continents and suspected that they were once pieces of the same puzzle. Now, 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. For the uninitiated, the Rayner Province is located in present-day East Antarctica.The 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.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. As a result, these rocks preserve a record of ancient events that took place deep within the Earth’s crust.Speaking to TOI, 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 in Andhra Pradesh 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 the geology faculty.Tiny crystals, massive clues:What they found was striking. “The rocks from Vizianagaram and Salur recorded the same three major stages of geological history that have already been identified in East Antarctica. The first stage occurred around 1,000 to 990 million years ago. During this period, the rocks were exposed to ultra-high temperatures of about 1,000 degrees Celsius deep within the Earth’s crust – roughly as hot as lava. As the landmasses that would eventually become India and Antarctica collided, they created a massive mountain range known as the Rayner-Eastern Ghats orogen,” said Prof Bose.The second stage took place between about 950 and 890 million years ago. Scientists describe this as a period of reworking. The rocks were heated again or buried deeper, and their mineral structures were altered once more. Such a long and complex history is typical of major mountain belts formed by continental collision.The third stage occurred much later, between about 570 and 540 million years ago. During this period, chemically rich fluids moved through cracks and layers in the rocks. This fluid activity left 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 the drifting continents:According to earlier studies, 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. Scientists can still trace their shared past because the rocks preserved 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.
