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According to conventional models, the sharp cooling and significant drop in sea level that occurred during the Eocene-Oligocene transition, about 34 million years ago, should have led to
According to conventional models, the sharp cooling and significant drop in sea level that occurred during the Eocene-Oligocene transition, about 34 million years ago, should have led to large-scale erosion of the continents. This would lead to the accumulation of large amounts of sandy material at the bottom of the ocean. The transition from the Eocene to the Oligocene marked one of the most extreme climate changes since the extinction of the dinosaurs, transforming the Earth’s climate from a “greenhouse” to an “ice age.”
But a new study from Stanford University reveals a surprising paradox: Virtually no sediment from this period has been found on the margins of all seven continents.
This unexpected finding was published on: Earth Science Reviewsreveals a mysterious global gap in the geological record.
“The results lead us to ask, ‘Where did all this sediment go?'” said senior author Stefan Graham, a professor at Stanford’s Doerr School of Sustainability. “It made me wonder,” he said. “Answering this question will help us better understand the functioning of sedimentary systems and how climate change affects deep-sea sediments.”
The discovery challenges existing models of sediment deposition and erosion and provides new insights into the global ecological consequences of significant climate change. The resulting data could also provide a clearer understanding of how today’s rapid climate change is reshaping the Earth’s surface.
“We took our first global look at the understudied response of the planet’s largest sediment mass transfer systems during the extreme Eocene to Oligocene transition,” explained lead author Zach Burton, now an associate professor in the Department of Earth Sciences. at Montana State University.
The transition from the Eocene to the Oligocene was a period of deep cooling of the planet. Massive ice sheets have formed in previously ice-free Antarctica, global sea levels have fallen dramatically, and mass extinctions of both marine and terrestrial species have occurred.
Before this period, Earth experienced some of the highest temperatures and sea levels since the dinosaurs, according to climate proxy records. Burton and his colleagues first set out to investigate the effects of these warm early Eocene conditions on deep-sea sedimentary systems.
In a study published in 2023 Nature Scientific ReportsThey found evidence of abundant sand deposition along Earth’s continental margins and linked this to increased weathering that increased soil erosion. The team then decided to expand their study to include the late Eocene and early Oligocene, when the Earth cooled rapidly and entered an “ice” climate.
To do this, researchers extensively examined hundreds of scientific studies spanning more than a century. They analyzed studies documenting ancient sediments that were often buried several kilometers below the ocean floor.
This comprehensive review included findings from offshore oil and gas drilling, onshore rock outcrops, and seismic data interpretation. In total, the study examined more than 100 geographic regions around the world, providing a detailed overview of the geological record at the edges of all continents. When the team combed through the collected data, they found a surprising absence of sand-rich sediments from the Eocene-Oligocene transition.
“We didn’t see abundant sand deposits like we saw in our Early Eocene warm climate study,” Burton said. “Instead, we found that distinct, widespread erosional unconformities—in other words, gaps in the rock record—developed during the extreme climatic cooling and oceanographic changes of the Eocene-Oligocene.”
Researchers offer various theories to explain the missing sediments. One idea is that strong ocean floor currents caused by changes in temperature and salinity caused by climate change may have eroded the ocean floor, washing sediments away from the continents.
Another possibility is that the rapid fall in sea level exposed continental shelves, allowing sediments to accumulate into the ocean depths, bypassing nearby sedimentary basins. Additionally, glacial erosion around Antarctica may have played a role in the redistribution of sediments.
These processes appear to occur worldwide, indicating that sedimentary deposits are influenced by global climate controls. Researchers believe this global impact indicates profound climate changes felt not only on land but also in the deepest ocean basins.
The results of the research provide valuable insight into how the Earth’s surface may respond to significant climate change. The transition from the Eocene to the Oligocene provides a window into the large-scale environmental changes that can result from rapid climate change, and is critical to understanding modern anthropogenic climate change.
Although the current climate change crisis is smaller on an overall scale than the Eocene-Oligocene transition, it is developing much faster. Researchers believe that studying these past events can help scientists better predict the dramatic changes that may occur as Earth’s climate continues to change rapidly.
“Our findings may help inform the radical changes that may occur at the Earth’s surface under conditions of rapid climate change,” Graham said. “The geological past determines the present and especially the future.”
By looking at past climate events and the response of sedimentary rocks, scientists hope to gain information that can guide our understanding of the challenges of modern climate change and potentially help mitigate its effects on Earth’s ecosystems and surface environment.
Source: Port Altele
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