Global Geological And Climatic Events

India and Australia were evolutionary neighbours

Note4Students

From UPSC perspective, the following things are important :

Prelims level : Dickinsonia, Bhimbetka

Mains level : Geological time scale

Bhimbetka, which has yielded a fossil of Dickinsonia dating back about 550 million years, is the first time the particular fossilized organism has been recorded in India.

Why does this fossil matter?

  • It dates back to an era regarded as the precursor to the explosion of life on earth during the Cambrian period.
  • Thus it puts India firmly on the map for studies of the Ediacaran era along with Australia and Russia.

Here’s what makes the discovery a global milestone:

(a) Ediacaran Period

  • The finding gives lead about the earliest living species during a period of the earth’s history known as the Ediacaran, named after the Ediacara Hills in South Australia.
  • This is the period in Earth’s history when Dickinsonia and several multicellular organisms existed.
  • It was approximately 635 million years ago (Ma) and 541 Ma, with the living creatures of the era, called vendobionts.

Now take this opportunity to revise the Geological time scale from your NCERTs. Try differentiating between different era, periods and epoch.

(b) India’s Proximity to Australia

  • Studies of the rock characteristics in and around Bhimbetka show that they share several characteristics with rocks in Australia.
  • Dickinsonia fossils from India were found by the scientists to be identical to the Rawnsley Quartzite in South Australia.
  • This provides evidence of their age and the proximity of the two landmasses in Gondwanaland in that era.
  • The evidence however did not support reconstructions adjusted for the polar wander phenomenon [which involves motion of continents over geologic time and its impacts].

 Use of Zircon dating

  • The age of fossil rock is determined using Zircon isotopes.
  • Zircon dating of the youngest Maihar sandstone in Madhya Pradesh puts its age at 548 Ma.
  • The lower Bhander group in the Son and Chambal valleys yielded an isotope-derived age for limestones ranging from 978 Ma to 1073 Ma, situating it in the older Tonian period.
  • The Ediacaran period was the precursor to the Cambrian (about 541 Ma to 485.4 Ma) when the earth witnessed an explosion of life forms and much of which makes up modern animal life today.
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