Date:

Study challenges common view of oxygen scarcity on Earth 2 billion years ago

Shungite, a unique carbon-rich sedimentary rock from Russia that deposited 2 billion years ago, holds clues about oxygen concentrations on Earth’s surface at that time.

Led by Professor Kurt Konhauser at the University of Alberta and Professor Kalle Kirsimäe at the University of Tartu, an international research team involving other colleagues from France, Norway, Russia, and USA, have found strikingly high molybdenum, uranium, and rhenium concentrations, as well as elevated uranium isotope ratios in drill cores that dissect the shungite rocks.

- Advertisement -

These trace metals are only thought to be common in Earth’s oceans and sediments when there is abundant oxygen around. The researchers found that such trace metal concentrations are unrivaled in early Earth’s history, suggesting elevated levels of oxygen at the time when the shungite was deposited.

“What is puzzling is that the widely-accepted models of Earth’s carbon and oxygen cycles predict that shungite should have been deposited at a time of rapid decrease in oxygen levels,” says Mänd, a PhD candidate at the University of Alberta and lead author of the study.

Most scientists agree that atmospheric oxygen levels significantly increased about 2.4 billion years ago–known as the Great Oxidation Event (GOE)–and reached about half of modern levels by about 2.1 billion years. The GOE was also accompanied by a shift in carbon isotope ratios in sedimentary rocks.

To scientists, this fits the story–the anomalous carbon isotope ratios reflect the burial of massive amounts of plankton as organic matter in ocean sediments, which in turn lead to the generation of excess oxygen. But the prevailing understanding is that immediately after this period of high concentrations, oxygen levels decreased again and remained low for almost a billion years during Earth’s so-called ‘middle age’.

- Advertisement -

“Fresh drill cores that we obtained from the Lake Onega area with the support of University of Tartu and Tallinn University of Technology provide some of the best rock archives to decipher the environmental conditions immediately after the GOE” says Kirsimäe, coordinator of geological field work.

“What we found contradicts the prevailing view–essentially we have clear evidence that atmospheric oxygen levels rose even further after the carbon isotope anomaly ended,” says Mänd. “This will force the Earth science community to rethink what drove the carbon and oxygen cycles on the early Earth.”

These new findings are also crucial for understanding the evolution of complex life. Earth’s ‘middle age’ represents the backdrop for the appearance of eukaryotes. Eukaryotes, the precursors to all complex life, including animals such as ourselves, generally require high oxygen levels in their environment to thrive.

This work now strengthens the suggestion that suitable conditions for the evolution of complex life on early Earth existed for a much longer time than previously thought. As such, the findings indirectly support earlier studies where Prof. Konhauser was involved that revealed large, potentially eukaryotic trace fossils as old as 2.1 billion years.

Despite these new advances, the delay between the initial rise of oxygen and the appearance and radiation of eukaryotes, remains an area of active research; one that University of Tartu and University of Alberta researchers are well positioned to help answer.

ESTONIAN RESEARCH COUNCIL

Header Image – Two-billion-year-old shungite, a type of sedimentary rock exposed in north-western Russia, records evidence for balmy, oxygen-rich conditions on the early Earth. Photo credits K. Paiste. Credit : K. Paiste.

- Advertisement -
spot_img
Mark Milligan
Mark Milligan
Mark Milligan is multi-award-winning journalist and the Managing Editor at HeritageDaily. His background is in archaeology and computer science, having written over 7,500 articles across several online publications. Mark is a member of the Association of British Science Writers (ABSW), the World Federation of Science Journalists, and in 2023 was the recipient of the British Citizen Award for Education, the BCA Medal of Honour, and the UK Prime Minister's Points of Light Award.
spot_img
spot_img

Mobile Application

spot_img

Related Articles

Stone box containing rare ceremonial offerings discovered at Tlatelolco

Archaeologists from the National Institute of Anthropology and History (INAH) have discovered a stone box containing ceremonial offerings during excavations of Temple "I", also known as the Great Basement, at the Tlatelolco archaeological zone.

Excavation uncovers traces of the first bishop’s palace at Merseburg Cathedral Hill

Archaeologists from the State Office for Monument Preservation and Archaeology (LDA) Saxony-Anhalt have uncovered traces of the first bishop’s palace at the southern end of the Merseburg Cathedral Hill in Merseburg, Germany.

BU archaeologists uncover Iron Age victim of human sacrifice

Archaeologists from Bournemouth University have uncovered an Iron Age victim of human sacrifice in Dorset, England.

Archaeologists find ancient papyri with correspondence made by Roman centurions

Archaeologists from the University of Wrocław have uncovered ancient papyri that contains the correspondence of Roman centurions who were stationed in Egypt.

Study indicates that Firth promontory could be an ancient crannog

A study by students from the University of the Highlands and Islands has revealed that a promontory in the Loch of Wasdale in Firth, Orkney, could be the remains of an ancient crannog.

Archaeologists identify the original sarcophagus of Ramesses II

Archaeologists from Sorbonne University have identified the original sarcophagus of Ramesses II, otherwise known as Ramesses the Great.

Archaeologists find missing head of Deva from the Victory Gate of Angkor Thom

Archaeologists from Cambodia’s national heritage authority (APSARA) have discovered the long-lost missing head of a Deva statue from the Victory Gate of Angkor Thom.

Archaeologists search crash site of WWII B-17 for lost pilot

Archaeologists from Cotswold Archaeology are excavating the crash site of a WWII B-17 Flying Fortress in an English woodland.