Ancient ocean water could help climate modelling

A team of researchers from India and Japan have found water droplets trapped in mineral deposits in the Kumaon mountains in the Indian state of Uttarakhand that were likely left from an ancient ocean dating back some 600 million years, as reported by Mongabay-India. The scientists say these droplets could aid the understanding of the Neoproterozoic Oxygenation Event and the Earth processes that fostered the evolution of complex life. They add that these droplets could offer insights about the makeup of ancient oceans and the environment at the time and they could be helpful for future climate modelling.

Referencing a paper, published in the journal ‘Precambrian Research’ in September, the Mongabay-India report highlights the work of three scientists from the Indian Institute of Science (IISc) Centre for Earth Sciences and two from Japan’s Niigata University, who 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. 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.

From their study, Mongabay-India reports that 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, as the researchers wrote in their paper. They 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.

The paper says that 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.

The research 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 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.

The researchers further stated that there was once a vast ocean once where the Himalayas now stand. 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 research team add in their paper that it is hopeful their findings will bring more researchers to the Himalayas to uncover more about the evolution of complex life forms on Earth. This could aid in the 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.