U.S. Geological Survey (USGS), USA
Info
Stromatolites are biogenic sedimentary rocks formed by the trapping and binding of sediment particles or the precipitation of dissolved substances as a result of the growth and metabolism of microorganisms in a body of water. They are usually layered and often consist of very finely layered limestone.
These limestones release life-sustaining oxygen into the environment.
Before the emergence of cyanobacteria, Earth’s atmosphere was virtually oxygen-free. Through billions of years of photosynthesis by the stromatolite-building microorganisms, the oceans—and ultimately the atmosphere—were enriched with oxygen. This laid the foundation for the development of higher, aerobic life forms.
Source: https://study.com/academy/lesson/stromatolites-overview-examples.html
Today, our planet is teeming with life, but that wasn’t always the case. Long before forests towered into the sky, animals roamed the land, and dinosaurs rose to prominence and then went extinct, our planet was shaped by a much smaller, more inconspicuous form of life. And even today, we can find traces of it.
These ancient fossils, the earliest visible evidence of life on Earth, are known as microbialites.
Western Australia is home to an extraordinary archive of microbialites: from the oldest known specimens preserved in rocks nearly 3.5 billion years old in the Pilbara to living specimens in the Shark Bay UNESCO World Heritage Site.
Our review of 50 years of microbialite research in Western Australia, published in the journal *Alcheringa*, summarizes what this archive can tell us about the evolution and resilience of life on Earth.
Despite a fossil record spanning billions of years, microbialites are surprisingly fragile. Fossil sites remain vulnerable to excessive collection and destruction, while living microbialites face increasing pressure.
In places like Lake Clifton and Shark Bay, certain events may have already caused irreparable damage. One such example occurred in May 2024, when dozens of aurora hunters trampled 2,000-year-old thrombolites in a restricted area at Lake Clifton.
Fossil microbialites preserved in rocks nearly 3.5 billion years old in the Pilbara region of Western Australia.
The Earth’s Oldest Traces of Life
Microbialites are mound-like structures that come in many shapes and sizes. They form when microbial colonies either precipitate minerals or trap and bind sediments.
The various types of microbialites can be characterized by their internal structure. Stromatolites are the best known and feature distinctive layers. Thrombolites, on the other hand, have a lumpy texture.
Stromatolites from the Proterozoic era, preserved in a wide variety of shapes and sizes.
Microbialite discoveries can tell us a great deal about life on Earth. They provide clues as to where some of the earliest life forms existed, where we might search for life beyond Earth, and how our atmosphere became oxygen-rich, paving the way for more complex life.
Modern sites are particularly important because they help us better understand the processes by which microbialites formed in the ancient rock record. Living microbialites from Shark Bay have even been described as the “Rosetta Stone” for understanding their fossil counterparts.
Microbialites also preserve evidence of how life in the past responded to ecological upheavals. The microbialite records in Western Australia span at least one and possibly two of Earth’s five major mass extinctions.
These records from deep time suggest that microbialites could serve as early indicators of ecological stress. There is evidence that sudden increases in microbialites in the past often preceded or coincided with major ecological disruptions and mass extinctions.
The living thrombolite reef at Lake Clifton in Western Australia, where microbial communities continue to form structures very similar to those preserved in the ancient rock record.
Nevertheless, our review highlights several significant gaps in our knowledge.
Scientists continue to debate how to distinguish structures formed by living organisms from those created by non-biological processes. Nor can we always say with certainty in which environments ancient microbiolites formed.
There is also uncertainty regarding which factors determine the shape and structure (morphology) of microbiolites. We also do not know exactly to what extent modern examples reflect the fossil forms.
Why the internal structure of thrombolites is lumpy rather than layered, as in stromatolites, remains a mystery. So does the question of how far back in the geological record they extend. Western Australia may be home to some of the oldest known thrombolites, but these specimens have not yet been documented in detail.
2.7-billion-year-old thrombolites from Western Australia that have not yet been described. These could be among the oldest known thrombolites in the world.
In short: Earth’s earliest biological history is not yet complete, even as the gaps are slowly being filled. Preserving the evidence—both living and fossilized—is essential if future scientists are to answer questions we don’t yet have answers to, or perhaps even ask questions we haven’t even thought of yet.
An Ancient Archive in Danger
A sign at Lake Clifton reminds visitors to stay away from the delicate living thrombolites, which can take decades or even centuries to recover from physical damage.
Despite their geological longevity and seemingly unchanging nature, microbialites are surprisingly delicate. Their rock-like appearance makes this difficult to recognize.
Living microbiolites can be extremely sensitive to environmental disturbances. Because of their extremely slow growth rates, it can take decades or centuries for physical damage to be repaired—if at all.
Many modern microbiolite sites are facing increasing pressure from changes in water quality, climate change, and rising visitor numbers.
Fossil microbiolites are also at risk. Throughout Western Australia, tourism, improper collecting, and even scientific sampling can damage or compromise these irreplaceable sites. As geological features, they are protected under the Geological Heritage Act.
Aerial view of Hamelin Pool, Shark Bay. The tracks carved through the microbiolites by carts more than 90 years ago are still visible today. Image courtesy of the Geological Survey of Western Australia, Department of Mines, Petroleum and Exploration.
Nevertheless, geological heritage in Australia continues to receive little recognition at both the federal and state levels and is allocated insufficient funding. The report “Australian State of the Environment 2021” concluded that “the overall outlook for geological heritage is poor” due to a lack of national policy frameworks, focus, and resources for this aspect of cultural heritage. Unfortunately, little has changed in this regard.
Today, we are confronted with an unprecedented and accelerating loss of biodiversity. The microbialite archive offers a long-term perspective on how ecosystems respond to environmental changes, ecological disturbances, and shifting conditions. The extent to which these insights can enrich our understanding of the challenges facing life today remains an open question.
Equally important is the question of whether the archives themselves—both living and fossil—will remain intact and accessible so that future generations can investigate not only the questions we ask today, but also those we cannot even imagine yet.
Source: https://theconversation.com/earths-oldest-evidence-of-life-is-written-in-stone-but-its-at-risk-of-disappearing-293101
These limestones release life-sustaining oxygen into the environment.
Before the emergence of cyanobacteria, Earth’s atmosphere was virtually oxygen-free. Through billions of years of photosynthesis by the stromatolite-building microorganisms, the oceans—and ultimately the atmosphere—were enriched with oxygen. This laid the foundation for the development of higher, aerobic life forms.
Source: https://study.com/academy/lesson/stromatolites-overview-examples.html
Today, our planet is teeming with life, but that wasn’t always the case. Long before forests towered into the sky, animals roamed the land, and dinosaurs rose to prominence and then went extinct, our planet was shaped by a much smaller, more inconspicuous form of life. And even today, we can find traces of it.
These ancient fossils, the earliest visible evidence of life on Earth, are known as microbialites.
Western Australia is home to an extraordinary archive of microbialites: from the oldest known specimens preserved in rocks nearly 3.5 billion years old in the Pilbara to living specimens in the Shark Bay UNESCO World Heritage Site.
Our review of 50 years of microbialite research in Western Australia, published in the journal *Alcheringa*, summarizes what this archive can tell us about the evolution and resilience of life on Earth.
Despite a fossil record spanning billions of years, microbialites are surprisingly fragile. Fossil sites remain vulnerable to excessive collection and destruction, while living microbialites face increasing pressure.
In places like Lake Clifton and Shark Bay, certain events may have already caused irreparable damage. One such example occurred in May 2024, when dozens of aurora hunters trampled 2,000-year-old thrombolites in a restricted area at Lake Clifton.
Fossil microbialites preserved in rocks nearly 3.5 billion years old in the Pilbara region of Western Australia.
The Earth’s Oldest Traces of Life
Microbialites are mound-like structures that come in many shapes and sizes. They form when microbial colonies either precipitate minerals or trap and bind sediments.
The various types of microbialites can be characterized by their internal structure. Stromatolites are the best known and feature distinctive layers. Thrombolites, on the other hand, have a lumpy texture.
Stromatolites from the Proterozoic era, preserved in a wide variety of shapes and sizes.
Microbialite discoveries can tell us a great deal about life on Earth. They provide clues as to where some of the earliest life forms existed, where we might search for life beyond Earth, and how our atmosphere became oxygen-rich, paving the way for more complex life.
Modern sites are particularly important because they help us better understand the processes by which microbialites formed in the ancient rock record. Living microbialites from Shark Bay have even been described as the “Rosetta Stone” for understanding their fossil counterparts.
Microbialites also preserve evidence of how life in the past responded to ecological upheavals. The microbialite records in Western Australia span at least one and possibly two of Earth’s five major mass extinctions.
These records from deep time suggest that microbialites could serve as early indicators of ecological stress. There is evidence that sudden increases in microbialites in the past often preceded or coincided with major ecological disruptions and mass extinctions.
The living thrombolite reef at Lake Clifton in Western Australia, where microbial communities continue to form structures very similar to those preserved in the ancient rock record.
Nevertheless, our review highlights several significant gaps in our knowledge.
Scientists continue to debate how to distinguish structures formed by living organisms from those created by non-biological processes. Nor can we always say with certainty in which environments ancient microbiolites formed.
There is also uncertainty regarding which factors determine the shape and structure (morphology) of microbiolites. We also do not know exactly to what extent modern examples reflect the fossil forms.
Why the internal structure of thrombolites is lumpy rather than layered, as in stromatolites, remains a mystery. So does the question of how far back in the geological record they extend. Western Australia may be home to some of the oldest known thrombolites, but these specimens have not yet been documented in detail.
2.7-billion-year-old thrombolites from Western Australia that have not yet been described. These could be among the oldest known thrombolites in the world.
In short: Earth’s earliest biological history is not yet complete, even as the gaps are slowly being filled. Preserving the evidence—both living and fossilized—is essential if future scientists are to answer questions we don’t yet have answers to, or perhaps even ask questions we haven’t even thought of yet.
An Ancient Archive in Danger
A sign at Lake Clifton reminds visitors to stay away from the delicate living thrombolites, which can take decades or even centuries to recover from physical damage.
Despite their geological longevity and seemingly unchanging nature, microbialites are surprisingly delicate. Their rock-like appearance makes this difficult to recognize.
Living microbiolites can be extremely sensitive to environmental disturbances. Because of their extremely slow growth rates, it can take decades or centuries for physical damage to be repaired—if at all.
Many modern microbiolite sites are facing increasing pressure from changes in water quality, climate change, and rising visitor numbers.
Fossil microbiolites are also at risk. Throughout Western Australia, tourism, improper collecting, and even scientific sampling can damage or compromise these irreplaceable sites. As geological features, they are protected under the Geological Heritage Act.
Aerial view of Hamelin Pool, Shark Bay. The tracks carved through the microbiolites by carts more than 90 years ago are still visible today. Image courtesy of the Geological Survey of Western Australia, Department of Mines, Petroleum and Exploration.
Nevertheless, geological heritage in Australia continues to receive little recognition at both the federal and state levels and is allocated insufficient funding. The report “Australian State of the Environment 2021” concluded that “the overall outlook for geological heritage is poor” due to a lack of national policy frameworks, focus, and resources for this aspect of cultural heritage. Unfortunately, little has changed in this regard.
Today, we are confronted with an unprecedented and accelerating loss of biodiversity. The microbialite archive offers a long-term perspective on how ecosystems respond to environmental changes, ecological disturbances, and shifting conditions. The extent to which these insights can enrich our understanding of the challenges facing life today remains an open question.
Equally important is the question of whether the archives themselves—both living and fossil—will remain intact and accessible so that future generations can investigate not only the questions we ask today, but also those we cannot even imagine yet.
Source: https://theconversation.com/earths-oldest-evidence-of-life-is-written-in-stone-but-its-at-risk-of-disappearing-293101
