Contributors: Biogéosciences UMR 6282 (BGS); École Pratique des Hautes Études (EPHE); Université Paris Sciences et Lettres (PSL)-Université Paris Sciences et Lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université Bourgogne Europe (UBE); Archéologie, Terre, Histoire, Sociétés Dijon (ARTeHiS); Ministère de la Culture et de la Communication (MCC)-Centre National de la Recherche Scientifique (CNRS)-Université Bourgogne Europe (UBE); Geo-Ocean (GEO-OCEAN); Université de Bretagne Sud (UBS)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO EPE)-Centre National de la Recherche Scientifique (CNRS); Institut des sciences de la terre Lausanne (ISTE); Université de Lausanne = University of Lausanne (UNIL); Géosciences Rennes (GR); Université de Rennes (UR)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS); ANR-20-CE49-0014,RISE,Contrôle tectonique de la dernière transition entre les modes climatiques de greenhouse et de icehouse : the rôle du soulèvement de l'Afrique(2020); European Project: 860383,H2020-MSCA-ITN-2019,H2020-MSCA-ITN-2019,S2S-Future(2020)
Abstract: International audience ; Climate cooling during the late Cretaceous (ca. 100-66 Ma) has been linked to CO2 drawdown produced by enhanced denudation episodes recorded in the eastern margin of South America and western margin of South Africa. However, the onset of these episodes is recorded during rather than prior to the main climate cooling stage of the late Cretaceous, reported within the Santonian-Early Campanian interval (about 86-81 Ma). Here, we investigate the clay fraction (< 2 μm) of sediments from the borehole O-A1 located in the continental slope of the Cape Basin, adjacent to the western South African Margin. We combine these results with previous records from the basin (DSDP 361) to investigate the controlling factors of the denudation record along the South African Plateau, and their relationship with the climate cooling during the late Cretaceous. The ΔεHf record (proxy for silicate weathering intensity) from site O-A1 shows an increase in silicate chemical weathering intensity during the Cenomanian-Maastrichtian (ca. 95-68 Ma) interval, predating the Campanian-Danian interval shown by the DSDP 361 record. While this offset between the sites is attributed to age model uncertainties from the site DSDP 361, the observed increase in silicate chemical weathering intensity is concomitant to an enhanced phase of physical erosion and tectonic uplift of the South African Plateau and mirrors the evolution of seawater 87 Sr/ 86 Sr at that time. Additionally, the duration of this increase even during global climate cooling suggests that the increase in weathering intensity and rate are mainly tectonically driven. Our ΔεHf(80) data from site O-A1 shows for the first time an increase in silicate chemical weathering intensity as early as the Cenomanian, suggesting not only that it could have played a role in maintaining the cool global climate trend during J o u r n a l P r e -p r o o f Journal Pre-proof the late Cretaceous, but that this episode could have contributed to trigger the CO2 drawdown responsible ...
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