We studied a large underwater sediment pile called the Valentin Feilberg Drift, located off the southern coast of Argentina. This drift was built over millions of years by deep ocean currents, including those coming from Antarctica and the Atlantic Ocean. Earlier research suggested that the drift started forming around 15 million years ago, when the Antarctic Ice Sheet became permanent, and that a major change happened around 8 million years ago when a new deep current from the North Atlantic may have reached this area. But until now, these ideas were hard to confirm without core samples.

In our study, we used high-resolution acoustic imaging to “see” layers of sediment beneath the seafloor, both deep (down to 1 km) and shallow (down to 70 meters). By analyzing repeating patterns in these layers, which reflect natural climate cycles, we were able to estimate their ages more precisely. We identified two key times of change: about 12.5 million and 7.8 million years ago. These findings help us better understand how deep ocean currents changed over time and how events like the closing of the Central American Seaway and changes in the North Atlantic shaped global ocean circulation.