HeriotWatt UniversityScientists have discovered a giant mud wave hidden on the floor of the Atlantic Ocean about 400 kilometers off the coast of Guinea-Bissau, West Africa.These huge sedimentary waves of sediment are found nearly a kilometer below the seafloor. They formed in an area once known as the Equatorial Atlantic Gateway, a vital sea passage that opened when South America and Africa began to separate and helped shape the Atlantic Ocean as we know it today.
The discovery was made by geologists Dr Débora Duarte and Dr Uisdean Nicholson from the School of Energy, Earth Sciences, Infrastructure and Society at Heriot-Watt University.
They say their findings, published in the journal Global and Planetary Change, suggest the Atlantic formed millions of years earlier than previously thought and may have kicked off a period of climate change.
The researchers used seismic data and cores from a 1975 Deep Sea Drilling Project (DSDP) well. They discovered five layers of sediment that can be used to reconstruct the tectonic processes that broke apart ancient Gondwana during the Mesozoic Era, when dinosaurs ruled the Earth.
Dr Eusdine Nicholson said: "One layer is particularly striking: it contains large sedimentary waves and 'contour drifts' - mounds of mud formed by strong bottom currents.
“Imagine a wave a kilometer long and hundreds of meters high: an entire area formed in a specific location west of the Guinea Plateau, right at the last ‘tipping point’ where the South American and African continents separated.
"They form because thick, salty water pours down the newly formed channels. You can think of it like a giant waterfall forming under the surface of the ocean."
"This is because there is a strong density difference between the relatively fresh water of the open mid-Atlantic to the north and the extremely salty water to the south. Just before that, massive salt deposits were deposited in the South Atlantic. When the channel opened, fresh water poured into these narrow basins, while denser, saltier water flowed northward, creating these giant waves."
Continental drift occurs earlier than expected
The discovery puts a new date on the opening of the equatorial Atlantic gateway and its impact on climate regulation at that time.
Dr. Deborah Duarte said: "It is agreed that this channel opened between 113 million and 830 million years ago. Sedimentary waves show that it opened earlier, about 117 million years ago."
"This was a very important period in Earth's history, and the climate went through some major changes. Until 117 million years ago, the Earth was cooling for a time, and large amounts of carbon were stored in emerging basins (possibly lakes) in the equatorial Atlantic. But then, from 117 million years ago to 110 million years ago, the climate warmed significantly."
"We think this may be due to the first connection through this channel and the influx of seawater into these emerging basins. As the channel gradually opened up, this initially reduced the efficiency of carbon burial, which would have an important warming effect, and eventually, as the portal became deeper and wider, a complete Atlantic circulation system emerged and the climate began a long-term cooling period in the Late Cretaceous." This suggests that the channel played a very important role in Mesozoic global climate change. "
Dr Nicholson said: "Understanding how ocean circulation affected climate in the past is crucial for predicting future changes. Today's ocean currents play a key role in regulating global temperatures, and disturbances such as melting ice caps can have far-reaching consequences."