Why in news? Researchers  from the Indian Institute of Science (IISc), Bengaluru, studied the rock deposits in southern India and have found that there was a composition of shallow, inland sea in the south Indian regions.

Highlights:

• The researchers analysed the ancient carbonate deposits in Vempalle in Andhra Pradesh and estimated the temperature and composition of shallow, inland sea that dates back to the Paleoproterozoic era.
• The study, published in the Chemical Geology, has been done in coordination with the University of Tennessee.
• sedimentary deposits formed in the region around 1.9-2 billion years ago. These deposits are mainly stromatolites, one of the earliest fossilised life forms on the planet.
• the first such evidence found in India. Researchers are now looking to work together with China, the US and Australia where materials of similar age have been found.

What did the study find out?

• The findings provide insights into how the conditions were during that time and how it provided the right ambience for photosynthetic algae to bloom.
• various studies of fossils from the Palaeoproterozoic era have shown that some life might have existed even under these harsh conditions. “Large amounts of carbon dioxide in the atmosphere were absorbed by the sea and trapped as carbonates in
• The team was able to figure out that the temperature of the seawater was about 20 degrees Celsius. This is in contrast to previous studies that analysed only chert samples from around the same period and had estimated that the temperature was around 50 degrees Celsius.
• The lower temperature estimate agrees more closely with the theory that the conditions were ideal for supporting life forms.
• During the Palaeoproterozoic era, the type of water present was earlier believed to be only heavy water, containing a specific set of isotopes or forms of hydrogen. However, in the study, the team showed that light water was also present back then.

What is Palaeoproterozoic era?

• The Paleoproterozoic is the first of three subdivisions of the Proterozoic Eon (occurring from 2.5 billion to 1.6 billion years ago (Ga). This period is marked by the first stabilization of the continents, and also when cyanobacteria evolved.

What is dolomite?

• Dolomite, a direct precipitate from seawater, provides a signal not only of seawater chemistry but also of seawater temperature.
• The researchers collected dolomite samples from chert – hard rocks formed by the interaction of microbes with seawater – and deposits underneath them called dolomitic lime-mud. Isotope thermometry technique was used to analyse them.