Science & Technology, India (Commonwealth Union) – In the lofty Himalayas, scientists from the Indian Institute of Science (IISc) and Niigata University, Japan, have made a fascinating discovery of water droplets trapped in mineral deposits, believed to be remnants of an ancient ocean that thrived around 600 million years ago. The examination of these deposits, containing calcium and magnesium carbonates, has also shed light on potential factors that contributed to a significant oxygenation event in Earth’s history.
Describing the finding as a “time capsule for paleo oceans,” Prakash Chandra Arya, a PhD student at the Centre for Earth Sciences (CEaS), IISc and the lead author of the study published in Precambrian Research, emphasizes the significance of this discovery.
Scientists hypothesize that roughly 700 to 500 million years ago, Earth experienced an extended period of global glaciation known as the Snowball Earth glaciation, one of the most momentous glacial events in its history. Subsequently, there was a surge in oxygen levels in the atmosphere, known as the Second Great Oxygenation Event, which played a pivotal role in the evolution of complex life forms. However, connecting these events has been challenging due to the scarcity of well-preserved fossils and the disappearance of past oceans from the Earth’s records. The exposures of marine rocks found in the Himalayas offer an opportunity to unveil some of the answers to this intriguing puzzle.
Snowball Earth glaciation, one of the most significant glacial events in our planet’s history, is thought to have occurred in multiple episodes between 720 and 635 million years ago, during the Cryogenian period of the Neoproterozoic era. These episodes of extreme global glaciation left a profound mark on Earth’s geological and biological history, shaping the course of evolution in ways that still influence life today.
“We don’t know much about past oceans,” said 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?”
Prakash further elaborated that such insights may further give clues in regards to the prior climate of the earth, and this information can be helpful for climate modelling.
The team’s findings, dating back to the time of the Snowball Earth glaciation, revealed that sedimentary basins endured a prolonged period of calcium depletion, likely due to reduced riverine input. The absence of ocean flow during this period meant no influx of calcium. Professor Sajeev Krishnan, the corresponding author of the study from CEaS, explained that this condition led to an increase in magnesium as more calcium precipitated. As magnesium deposits crystallized, they were able to trap paleo ocean water in their pore spaces.
The scarcity of calcium also created a nutrient-deficient environment, favorable for the growth of slow-growing photosynthetic cyanobacteria. These organisms might have significantly contributed to increased oxygen release into the atmosphere. According to Prakash, the rise in atmospheric oxygen levels would have driven biological evolution.
The team extensively looked out for these deposits in a vast stretch of the western Kumaon Himalayas, covering areas from Amritpur to the Milam glacier, and from Dehradun to the Gangotri glacier region. Through thorough laboratory analysis, they confirmed that the deposits resulted from precipitation from ancient ocean water rather than from sources like the Earth’s interior, such as submarine volcanic activity.
The researchers believe that these deposits hold vital information about ancient oceanic conditions, including pH, chemistry, and isotopic composition, which were previously only hypothesized or modeled. Such data can offer valuable insights into the evolution of oceans and life in Earth’s history.
The study is likely to be highly beneficial for researchers seeking solid evidence on the unfolding of events on earth many years back. The emergence of advanced data analytics and more advanced equipment in recent decades has helped gain better insights into previously puzzling occurrences.
