EU and Brazilian researchers: Amazon River older than previously thought

The Amazon River contributes a fifth of the total fresh water supply to the global oceans and has the largest drainage basin of all rivers around the world. The history of the river and its basin has been hard to assess, but geochemical and palynological analyses now shine a light on the climatic and geographical development along with the evolution of its biome.

‘We applied high resolution analytical techniques not previously used in the region,’ says Professor Farid Chemale, senior author from the University of Brasilia (now at Universidade do Vale do Rio dos Sinos, São Leopoldo). Researchers sampled the transition interval in a classical section of the Amazon submarine fan, where the sediments transported by the river are deposited, ‘and as a result accurately record its evolutionary history,’ explains Prof Chemale.

By analysing sediment extracted from a hydrocarbon borehole situated offshore, more than 4.5 kilometres below sea level, the CLIM-AMAZON project now dates the formation of the river at 9.4 to 9 million years ago. This postdates estimates from an earlier study of the same borehole by around 1 to 1.5 million years. The research was recently published as an early view of the journal ‘Global and Planetary Change.’

Aiming to increase the visibility and excellence of long-term Brazilian-European scientific activities, CLIM-AMAZON is also shining a new light on the biome evolution of the region.

Dr Carina Hoorn, lead author and researcher at the University of Amsterdam’s Institute for Biodiversity and Ecosystem Dynamics, says, ‘Our new data confirms an old age for the Amazon River and also point at an expansion of grasslands during the Pleistocene that was not known before.’ Their research showed a rise in grass remains that suggests that mountain uplift and Quaternary climatic changes strongly affected the landscape. Dr Hoorn explains, ‘This probably opened up new habitats for grass colonisation.’

These findings reveal a defining moment in the development of the paleogeography of South America as the river formed both a bridge and a divider for biota in the Amazonian landscape. ‘Further research on land and at sea may give more answers but will require investment in both continental and marine drilling,’ says Dr Hoorn.

The CLIM-AMAZON project, a joint Brazilian-European scientific initiative for climate and geodynamic research on the Amazon River Basin sediment, fostered exchanges between Brazilian and European scientists in the area of geosciences and environmental studies. It did so through scientific meetings and visits by experienced European researchers to Brazil.

For more information, please see:
project website