Scientists find ancient ocean water in Himalayas, offer insights into Earth’s past

A joint team of Indo-Japanese scientists have found traces of an ancient ocean that once existed in the Himalayas around 600 million years ago.

Scientists from the Indian Institute of Science (IISc), Bengaluru, and Niigata University, Japan, have discovered droplets of water trapped in mineral deposits that were likely left behind from the pristine ocean.

After analysing the deposits, which had both calcium and magnesium carbonates, the researchers said that the discovery could provide key insights into a significant oxygenation event in Earth's past.

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“These mineral deposits are like time capsule for paleo oceans," Prakash Chandra Arya, a PhD student at the Centre for Earth Sciences (CEaS), IISc, and the research's lead author, said in his study published in Precambrian Research.

Snowball Earth glaciation

According to their thesis, Earth was once covered with thick sheets of ice between 700 and 500 million years ago, known as the Snowball Earth glaciation— one of the major glacial events in Earth's history.

Then it was followed by the Second Great Oxygenation Event, which increased the amount of oxygen in the Earth's atmosphere and led to the evolution of complex life forms.

However, scientists have not fully comprehended how these events were connected due to the lack of well-preserved fossils and the disappearance of all past oceans that existed in the Earth's history.

They believe that exposure of such marine rocks in the Himalayas can offer some clues to the Earth’s past climate.

"We don't know much about past oceans," says Prakash. "How different or similar were they compared to present-day oceans? Were they more acidic or basic, nutrient-rich or deficient, warm or cold, and what was their chemical and isotopic composition?"

“Such insights could also provide clues about the Earth's past climate, and this information can be useful for climate modelling,” he added.

What did they find?

The study states that the deposit found by the team showed that the sedimentary basins were deprived of calcium for a prolonged period of time, probably due to low riverine input.

This lack of calcium led to increased magnesium levels, with the resulting magnesium deposits trapping ancient ocean water as they crystallised.

"During this time, there was no flow in the oceans, and hence no calcium input. When there is no flow or calcium input, as more calcium precipitates, the amount of magnesium goes up," says Sajeev Krishnan, Professor at CEaS and corresponding author of the study.

The study states that calcium deprivation may have caused nutrient deficiency and created favourable conditions for slow-growing photosynthetic cyanobacteria.

These organisms could have begun releasing more oxygen into the atmosphere, contributing to the Second Great Oxygenation Event, their research argues.

The study was conducted across a vast stretch of the western Kumaon Himalayas, from Amritpur to the Milam glacier and Dehradun to the Gangotri glacier region.

Using extensive laboratory analysis, scientists were able to confirm that the deposits originated due to precipitation from ancient ocean water, and not from other places, such as the Earth's interior, for example from submarine volcanic activity.

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