Surat: history
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Eocene Epoch
Paul John, July 23, 2023: The Times of India
About 50 million years ago – a period known as the early Eocene Epoch – the Indian subcontinent was an island drifting northward towards Asia after separating from a vast continent called Gondwanaland. Its plants and animals looked nothing like those we see today. There was a fourlegged mammal that would give rise to modern-day horses and rhinos, primates that would be the precursors of modern lemurs, and many other species.
Remains of these now-extinct animals are sometimes found neatly preserved as fossils across the country, but the lignite mines in Vastan, Mangrol and Tadkeshwar, 40km northeast from Surat in Gujarat, are a treasure trove for palaeontologists – the scientists who study fossils.
Fuel For Research
Lignite, like coal, is a sedimentary rock that’s mostly used as fuel in thermal power plants. The lignite mines near Surat have a thick layer of sedimentary rock known as the Cambay Shale Formation (CSF) that has an abundance of plant, insect and vertebrate fossils.
The first CSF fossils were discovered at the Vastan mine in 2002. Since then, paleontologists from India and abroad have collected thousands of specimens from Vastan and other nearby mines.
Among the most remarkable finds here are the bones and 200 teeth of Cambaytherium thewissi, the ancestor of the modern horse that lived 54. 5 million years ago. After 15 years of studies, palaeontologists and geologists believe not only modern-day horses but also tapirs and rhinoceroses originated from this animal. “Modern horses, rhinos and tapirs belong to a biological order called Perissodactyla. These animals have an uneven number of toes on their hind feet and a special digestive system,” says R S Rana of the department of geology at HNB Garhwal University in Uttarakhand.
Fossils of Asiadapis cambayensis and Marcgodinotius indicus are other interesting finds. These two primates belonged to an extinct group called adapoids that had already diversified by the early Eocene. Adapoids are the ancestors or close relatives of lemurs, lorises and bushbabies, primitive primates that live today in Africa and Asia.
The fossils from Tadkeshwar are being studied by a nine-member team of palaeontologists from Johns Hopkins University, HNB Garhwal University, Rowan University, Wadia Institute of Himalayan Geology, Ghent University, Panjab University and the Royal Belgian Institute of Natural Sciences. The team has published several papers on the fossils.
Abundance Of Plant Fossils
The Vastan mines area was once home to a tropical deciduous forest with moisture-loving plants, so remains of early fruit-bearing trees and shrubs have also been found in the mines. These include fruits like Ziziphus xylopyrus or kath ber, and flowering vines like Combretum decandrum or Rangoon creeper.
In 2010, palaeontologists discovered 150kg of amber shards from Tadkeshwar with insects trapped in them, indicating that the region was more diverse than previously thought.
Researchers from India, the US and Germany deduced that the fossilised tree resin belonged to a 60-million-year-old tropical rainforest. “This discovery is important because it is the first significant one found in India,” a senior researcher, who did not wish to be named, told TOI.
India-Europe Connection
The fossils found in CSF are important for several reasons. They are not only some of the earliest specimens of the Cenozoic or current geological age that started 66 million years ago but also show a link between India and Europe at the time.
“The Vastan mammalian fauna… is the oldest Cenozoic mammal fauna from India, dating back to the early Eocene Epoch,” says Rana. “It contains a mix of European and Asian taxa (populations of organisms), suggesting that India was still connected to Europe at this time. Also, the fauna includes the first early Eocene primates from India, which provide important insights into the evolution of this group of mammals. ”
Indeed, there are strong similarities between the CSF fossils and fossils from Europe. For instance, the horse ancestor Cambaytherium is closely related to another animal called Plagiolophus that lived in France and Spain around the same time. Similarly, the early primates Asiadapis and Marcgodinotius are closely related to the European adapoids, Leptadapis and Cantius.
How could an exchange of animals have occurred across India and Europe in the early Eocene when they were separated by thousands of kilometres of ocean? The animals possibly moved across an arc of islands known as Kohistan-Ladakh that lay along the northern margin of the Neo-Tethys Ocean, a large body of water that separated India from Asia.
Link With Gondwana Too
On the other hand, some fossils from Tadkeshwar are linked to Gondwana, the southern supercontinent that India broke away from during the late Cretaceous Epoch, some 65 million years ago. For example, fossils of Pelomedusoides turtles (sidenecked), Dyrosaurid crocodiles (with long snouts) and madtsoiid snakes (medium-sized to gigantic reptiles) have been found in CSF. All of these are typical Gondwanan groups.
These fossils suggest that India retained some of its ancient Gondwanan fauna even after it became isolated as an island. Some of these animals may have originated in Madagascar, which was the last landmass to separate from India during the Late Cretaceous. Alternatively, they might have come from North Africa, which was closer to India than Europe during the early Eocene. They may have crossed the southern margin of the Neo-Tethys Ocean using similar island-hopping routes like their European counterparts.
Fossils from Tadkeshwar show that the early Eocene was a time of rapid faunal turnover in India when new groups arrived from other continents while old groups persisted or became extinct. These changes were driven by India’s northward drift, which altered its climate and environment.
