The Amazon River originated as a transcontinental river around 11 million years ago, and took its present shape approximately 2.4 million years ago. These are the most significant results of a study on two boreholes drilled in proximity of the mouth of the Amazon River by Petrobras, the national oil company of Brazil. A team from the Institute for Biodiversity and Ecosystem Dynamics (IBED) of the University of Amsterdam, the University of Liverpool and Petrobras used this new oceanic data to reconstruct the history of the Amazon River. The study was published in the scientific journalGeologyin July 2009.

Until recently, a sediment column around 6 miles thick from the Amazon deep-sea fan (a sort of underwater delta), proved a hard nut to crack, and scientific drilling expeditions such as the Ocean Drilling Program only could reach a fraction of it. Recent exploration efforts by Petrobras, however, were successful. Sedimentological and paleontological analysis on samples from two boreholes, one of which was more than 2.5 miles below sea floor, now give insight into the history of both the Amazon River and the Amazon deep-sea fan. Prior to this publication, the exact age of the Amazon River was unknown, and this research has large implications for understanding South American paleogeography and the evolution of aquatic organisms in Amazonia and the Atlantic coast.