Tracing the sedimentary provenance of the Congo River: A source-to-sink approach using double zircon dating ((U-Th)/He & U-Pb)

The Congo River system, located in Central Africa, drains a basin exceeding 3.5 million km² and with a course up to 4,000 km, ranking it among the world’s largest rivers. It spans from the western edge of the East African Rift to its offshore deep-sea fan which associated with oil and gas resources. This vast system is characterized by a high sediment load, positioning the Congo as the second-largest contributor to modern continent-to-ocean sediment flux, after the Amazon River. These observations raise several interconnected questions: i) what are the origin of this sediment? ii) does this high sediment load reflect a high erosion rate? (iii) how has this flux evolved throughout the Congo River’s history?

Moreover, the Congo River sediments– have recorded the vertical dynamics of the corresponding area (i.e. Central African Plate) which remain poorly constrained, except along the rift margins. These sedimentary archives have also recorded how Central Africa’s erosional dynamics have evolved over the past, and whether it has been impacted by climatic or tectonic changes. 

Applying a source-to-sink approach to the Congo River sediments may therefore provide critical information and data to better understand the dynamics and history of one of the world largest sedimentary systems of the world and help to better understand the uplift and erosional evolution of this vast region.

Recent studies have employed conventional source-to-sink methods (e.g., heavy mineral analysis and U-Pb zircon dating) on modern Congo sediments (Garzanti et al., 2021, 2019). However, these approaches faced challenges due to the homogeneity of source signals, particularly in the Cuvette Centrale and surrounding basement outcrops, which exhibit similar geochronological signatures. To overcome this limitation, we apply a recent method: double dating of zircons ((U-Th)/He and U-Pb) combine with REE determination. Applied to both modern and ancient sediments (up to 50 Ma), this technique enables more precise source reconstruction. We will present the newly generated results and discuss their implications for the Congo River’s sedimentary history and the broader understanding of Central Africa’s geological evolution.

 

Garzanti, E., Bayon, G., Dennielou, B., Barbarano, M., Limonta, M., Vezzoli, G., 2021. The Congo deep-sea fan: Mineralogical, REE, and Nd-isotope variability in quartzose passive-margin sand. Journal of Sedimentary Research 91, 433–450. https://doi.org/10.2110/jsr.2020.100

Garzanti, E., Vermeesch, P., Vezzoli, G., Andò, S., Botti, E., Limonta, M., Dinis, P., Hahn, A., Baudet, D., De Grave, J., Yaya, N.K., 2019. Congo River sand and the equatorial quartz factory. Earth-Science Reviews 197, 102918. https://doi.org/10.1016/j.earscirev.2019.102918