A recent article in the Nature Scientific Journal offers fresh insights into the monumental geological formation at the bottom of the Atlantic Ocean, over a thousand kilometers from the Brazilian South and Southeast coasts.
This formation, known as the Rio Grande Rise, is a cluster of underwater mountains spanning an area the size of Spain and has long been a subject of scientific interest. The formation is also known as the Rio Grande Elevation or Bromley Plateau.
The novelty of the study, conducted by Brazilian scholars from the University of São Paulo (USP), along with contributions from a British researcher at the National Oceanographic Center in Southampton and an Italian academic, reveals that about 40 million years ago, part of this formation was a large volcanic island with a tropical climate.
Brazil has been petitioning the United Nations to expand its maritime boundaries, and the Rio Grande Rise region is a crucial area where the country seeks recognition of new borders. Luigi Jovane, the project coordinator and a professor at the Oceanographic Institute of the University of São Paulo, conveyed to Valor that the study's findings could significantly bolster Brazil's argument for redefining its maritime borders.
“It certainly aids our case considerably, as we have shown that this region was submerged, received material from the continent, and was directly connected to the continent until relatively recently in geological terms,” he explained. “This is vital information that can be presented to the United Nations.”
Brazil's interest in redefining its maritime borders is primarily driven by the potential mineral wealth in the subterranean layers of the seabed.
Geologist Izabel King Jeck, a reserve officer in the Brazilian Navy who has been involved in the technical discussions at the UN from the start, also believes the study could bolster the claim that the Rio Grande Rise is part of the continental shelf.
“It's additional evidence supporting Brazil's claim,” Ms. King Jeck stated. She notes that a key factor in UN discussions is demonstrating a connection between the continent's relief and seabed formations, such as the Vitória-Trindade Chain. She explains that this connection is much deeper and subtler in the case of the Rio Grande Rise. However, beyond the similarity in relief, geological characteristics that show a link between the continent and offshore formations are also considered significant.
Ms. King Jeck recalls that a few years earlier, a study involving researchers from the Brazilian geological service had already indicated the presence of rock types in the Rio Grande Rise that are characteristic of the continent rather than oceanic islands.
“And now there's additional evidence from the analysis of the red clays in this new study. We're piecing together this puzzle to support the argument for the continental nature of the Rio Grande Rise,” she explained.
The red clay, collected from the westernmost point of the uplift, played a crucial role in the research, leading to the findings published in the November 4 issue of Nature.
The research was anchored in two expeditions, one in February 2018 using the University of São Paulo's oceanographic vessel, Alpha Crucis, and another aboard the British ship Discovery in November of the same year. The latter expedition was equipped with autonomous submersibles and a remotely operated vehicle, essential for capturing images and gathering samples from the elevation.
One of these vehicles employed a robotic arm to collect a sample of red clay from a specific location under scientific scrutiny. “Upon analyzing this sample, we found certain mineral associations. These associations indicate that it was a paleosol formed through the tropical alteration of volcanic islands that existed in this region between 40 and 50 million years ago,” explained Mr. Jovane. Paleosols are ancient soils that supported vegetation in the distant past, although they no longer do so.
“We demonstrated that in the Rio Grande Rise, there is a paleosol containing minerals not derived from changes in the oceanic environment, as they cannot be transported by currents. These materials were formed ‘in situ' when the area was submerged and had subaerial contact,” the scientist explained.
The red clay, collected from the top of the structure at a depth of at least 600 meters, closely resembles the red earth commonly found in inland regions of Minas Gerais and São Paulo. It is rich in hematite, magnetite, aluminum, and kaolinite, typically forming under tropical forests.
The reviewers of the scientific study critiqued its reliance on a single red clay sample weighing less than one kilogram. However, Mr. Jovane counters that, despite being just one sample, the accompanying images confirm the widespread presence of this paleosol atop the structure.
The research focuses on the sustainability of seabed mining and is part of the Emege project, currently funded by Finep—a Brazilian government organization that provides financial support for developing science, technology, and innovation in various sectors within Brazil. It has also received support from Fapesp—a public foundation in Brazil with the mission of supporting scientific research in the state of São Paulo—and the Office of the Dean of Research at USP.
The 2018 expedition, foundational to this study, was not primarily aimed at assessing mineral potential. Yet, existing data indicates the Rio Grande Rise is rich in nickel, copper, and cobalt, as well as significant amounts of lithium and rare earth-related metals like tellurium, used in photovoltaic cells, Mr. Jovane noted.
Translation: Melissa Harkin