• Researcher: Camilo Esteban Gaitan Valencia
• Host institution: Université Bourgogne Franche Comté
• Supervisors: Emmanuelle Pucéat, Pierre Pellenard

Objectives:

The major uplift phase encountered by South Africa during the late Cretaceous leaded to a drastic increase in the denudation rates of the south African margin, associated to large sediment accumulation rates offshore. This event provides a unique opportunity to explore the long-term response of chemical weathering and of erosion to intense tectonic uplift within a greenhouse climate. The respective importance of these two processes in the evolution and distribution of detrital fluxes and in the formation of reservoirs is a key question that still remains to be elucidated, especially in such active tectonic context where denudation rates and weathering rates can become decoupled. The ESR will apply here a novel geochemical approach, combining clay mineralogical analyses with clay Nd and Hf isotope composition (ΔεHf), to:

• decipher the respective evolution of chemical weathering and erosion during the late Cretaceous uplift of South Africa
• tackle the links between these two processes and the evolution and distribution of detrital fluxes in this tectonic setting
• explore the potential impact of this uplift on late Cretaceous climate evolution, through CO2 consumption by silicate weathering reactions.

To meet these challenging objectives, both ODP/DSDP cores (360, 361) offshore and cores onshore from (the Geological Survey?) in the (Cape Basin/Orange Basin?) region have been targeted, with sediment accumulation rates already available, that will be used to capture the respective role of weathering and erosion changes in the evolution and distribution of sediments offshore.

Expected Results:

• respective evolution and relative importance of erosion and weathering of the south African margin during the late Cretaceous uplift of South Africa
• links of these two processes with detrital fluxes evolution and sediment distribution offshore
• potential role of this tectonic uplift in climate evolution during the Cretaceous.

Secondments:

• Université de Rennes 1 (F. Guillocheau) - Replace geochemical and mineralogical signals within the framework of sediment accumulation rates history offshore (7 months)
• GFZ – Helmholtz Centre Potsdam (J Braun) - Numerical experiments of weathering and erosion during tectonic uplift (1 month)