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Indian Amber and Plate Tectonics
About 160 million years ago India broke off from the East African land mass and raced northwards, sometimes at the incredible speed of 25 cm per year, until it rammed into Asia about 40 to 50 million years ago, that is at least what is generally assumed. But if that is so the Indian continent would have been an isolated island for about 100 million years ago. This time should have been sufficient to give rise to a unique flora and fauna.
A multitude of ancient insects, but also spiders, mites, and plant parts found in a vast new amber deposit in India - some 150 kg of amber produced by an ancient rainforest in the Early Eocene, or 52-50 million years ago - are however less unique than would have been expected after 100 million years of island isolation.
Most of the included insects show links to modern insects as well as those that lived millions of years ago in different parts of the world, including Asia, Australia, and even South America (and thus not particularly Africa or Madagascar!). This could be explained by “land-bridge” connections (Where?). It is also possible for plants to drift hundreds of km on open ocean currents, and in the case of insects, some can fly, or get blown away, but …
The resin that later became amber originated from an ancient tropical rainforest, and likely produced by a sort of flowering hardwood trees that predominate in the forests of southeast Asia today. Many experts used to suggest that this type of tropical broadleaf rainforest first originated in the Miocene some 20 or 25 million years ago. That is yet another idea challenged by the recent amber discovery.
Besides the rainforest's age and India's biogeography it is astonishing to see the huge number of perfectly preserved specimens of insects, most of which have never been seen before. Unlike other types of amber found in deposits in the north (like the Baltic Amber), the Indian amber is quite distinct from that of resins produced by conifers, and much softer. This unique property made it possible completely to dissolve the amber and extract the ancient insects, plants and fungi.
The best known amber deposits are in the Dominican Republic, Mexico and the Baltic region, where some 80% of the world's known amber is found. There are tonnes of amber in the new Indian discovery with fossils from the terrestrial tropics, where the fossil record is otherwise not so good, because usually all the organic material gets rotten very quickly. With tonnes of amber now at the disposal a lot of secrets may be uncovered about world those many millions of years ago.