In the Kumaon mountains in the central sector of Uttarakhand’s Himalayas, a team of scientists from the Indian Institute of Science and Japan’s Niigata University have unearthed water droplets trapped in mineral deposits. These droplets could be remnants of an ancient ocean that existed around 500-700 million years ago, say the scientists, and that they could enhance the understanding of how complex life forms evolved on Earth.
In their paper, published in the journal Precambrian Research in September, three scientists from Centre for Earth Sciences of the Indian Institute of Science and two from Niigata University wrote that they had discovered mineral deposits in the Kumaon mountains, in a region also known as the Lesser Himalayas, that contained marine carbonates from a sea of the Neoproterozoic era, estimated to have existed between 1 billion and 540 million years ago.
The team found sparry magnesites, which are stratigraphically associated with dolomite, a kind of limestone that is rich in magnesium carbonate and calcium carbonate and stromatolite, which is a sedimentary rock formed by microbial organisms. But the deposits the researchers found had lower amounts of calcium and higher amounts of magnesium, suggesting a different origin and environment of precipitation, the researchers wrote in their paper.
“In present-day environmental conditions, precipitating magnesium carbonate in the oceans is difficult. However, during the Neoproterozoic era, extreme environmental and climatic factors favoured magnesium carbonate precipitation because the calcium input in the oceans was significantly low due to the freezing of rivers,” said professor Sajeev Krishnan of the Centre for Earth Sciences, one of the corresponding authors of the paper.
The research team is hopeful their findings will bring more researchers to the Himalayas to uncover more about the evolution of complex life forms on Earth.
“Our contribution may attract other research groups towards the Himalayan mountain range for experimenting on carbonate/past ocean chemistry, the evolution of cyanobacteria, Snowball Earth glaciation and related Earth’s Oxygenation Events,” said Prakash Chandra Arya, a PhD student at the Indian Institute of Science and the first author of the paper.
The evolution of complex life forms
The researchers stated that the development of sparry magnesites in the Kumaon mountains took place approximately 750-580 million years ago during the Snowball Earth glaciation period when Earth was covered by thick ice sheets.
“This led to changes in sedimentation rates, ocean chemistry and the response of life to these events,” Arya said. “Low calcium input during that period provided photosynthesising cyanobacteria with the opportunity to rapidly evolve and expand, as other microorganisms would hardly survive in such conditions.”
Samriddhi Jain, a PhD scholar at the Indian Institutes of Technology Bombay who studies single-celled organisms called foraminifera, explained this phenomena in detail. “During the Snowball Earth glaciation period, the thick ice sheets performed the albedo effect; that is, they reflected more sunlight leading to reduced solar insulation and less heating of the Earth’s atmosphere,” she said.
“The thick ice sheets and their albedo effect restricted the flow of rivers into oceans. As a result, the flow of riverine nutrients that are important for the growth of complex life forms were reduced in the ocean. However, the photosynthesising cyanobacteria, also known as blue-green algae, flourished even with less nutrients,” she added.
These evolving communities of cyanobacteria generated a large amount of oxygen in the atmosphere, causing the Neoproterozoic Oxygenation Event, also known as the Second Great Oxygenation Event, which occurred from 630-551 million years ago, after Snowball Earth glaciation.
It is thought that the increased oxygen in the atmosphere during the Second Oxygenation Event led to the rapid evolution of complex life forms from simple unicellular or small multicellular forms, the paper stated. This event, known as Cambrian Explosion, is believed to have happened between 541 million and approximately 530 million years ago at the end of Neoproterozoic and the beginning of Cambrian era.
“We know very little about our past oceans, where the first life forms originated and evolved. We don’t know much about whether the past oceans were more acidic or basic, warmer or colder, more nutrient-rich or deficient, and how different their chemical and isotopic composition was compared to the present oceans,” Arya said. “The ocean water trapped in magnesite crystals can provide insights into these aspects, and this information can be used for future climate modeling.”
Their findings highlighted a likely “a chain reaction” of one Earth process triggering another. The team demonstrated how a climatic event would have altered ocean and sediment chemistry, resulting in rapid proliferation of cyanobacteria, which, in turn, increased the oxygen levels in the atmosphere and laid the foundation for the evolution of complex life forms.
The Himalayas in evolution
The research team affirmed that the Himalayas were a prime location to explore various Earth processes, including continental-continental collision, orogeny, tectonic deformation, seismic activity and climate variations, which are extensively recorded and visible in this region. The Kumaon Lesser Himalayas are recognised as one of India’s notable Precambrian basins.
“We were interested in understanding the collisional dynamics of the Indian and Eurasian plates, which can only be done in the Himalayas,” Arya said on being asked why they chose the Himalayas for their research. “The region has a revealing stratigraphy and has nicely exposed sparry magnesite in the eastern side of Kumaon.”
The researchers further stated that there was once a vast ocean once where the Himalayas now stand. “Before the Indian plate collided with the Eurasian plate, there was an ocean named Tethys,” the first author of the paper stated (Tethys is also the name of the Greek goddess of freshwater).
Even though a significant part of the Himalayas is dominated by rocks (limestone and dolomite) that were formed exclusively in a marine setting, the ocean water trapped in the magnesite crystals was not from the Himalayas’ current geographical location. This is because approximately 600 million years ago, the Indian plate was situated in a different location than it is today.
The team of scientists is hopeful their findings will attract other research groups to the Himalayan mountain range and aid our understanding of ancient oceans, which is restricted due to tectonic activities that have since destroyed them. The chemical and isotopic compositions of these oceans are largely a mystery, with only indirect signatures available, they wrote in their paper.
Jain, the PhD scholar from IIT Bombay, echoed the same and advocated for further research on past oceans. She said, “Studying preserved ocean chemistry from the magnesites can provide important insights into past environmental conditions, making it possible to understand the history of oxygenation.”
Studying these oxygenation events, she said, is crucial to understanding the evolution of multicellular life, including humans, from multicellular eukaryotes – unicellular organisms whose cells contain a membrane-bound nucleus.
On being asked how their findings are important and applicable to other regions on Earth, Arya said, “Sparry magnesites from different geological periods are exposed in various parts of the world, particularly in Europe, North America and South America. Despite the differences in time scale, we believe that certain key chemical and biological responses will be reflected in their results.”
This article was first published on Mongabay.