The impact of African aridity on the isotopic signature of Atlantic deep waters across the Middle Pleistocene Transition

Bruno Malaizé (1) , Elsa Jullien (1) , Amandine Tisserand (1) , Charlotte Skonieczny (2) , Francis Grousset (1) , Frédérique Eynaud (1) , Catherine Kissel (3, 4) , Jérôme Bonnin (1) , Svenja Karstens , Philippe Martinez (1) , Aloys Bory , Viviane Bout‑roumazeilles (5, 6) , Thibaut Caley (1) , Xavier Crosta (1) , Karine Charlier (1) , Linda Rossignol (1) , José-Abel Flores , Ralph Schneider

1 EPOC - Environnements et Paléoenvironnements OCéaniques
2 GEOPS - Géosciences Paris Saclay
3 CLIMAG - Climat et Magnétisme
4 LSCE - Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette]
5 LOG - Laboratoire d’Océanologie et de Géosciences (LOG) - UMR 8187
6 Géosystèmes - UMR 8157

A high resolution analysis of benthic foraminifera as well as of aeolian terrigenous proxies extracted from a 37 m-long marine core located off the Mauritanian margin spanning the last ~1.2 Ma, documents the possible link between major continental environmental changes with a shift in the isotopic signature of deep waters around 1.0-0.9 Ma, within the so-called Mid-Pleistocene Transition (MPT) time period. The increase in the oxygen isotopic composition of deep waters, as seen through the benthic foraminifera δ 18 O values, is consistent with the growth of larger ice sheets known to have occurred during this transition. Deep-water mass 2 δ 13 C changes, also estimated from benthic foraminifera, show a strong depletion for the same time interval. This drastic change in δ 13 C values is concomitant with a worldwide 0.3‰ decrease observed in the major deep oceanic waters for the MPT time period. The phase relationship between aeolian terrigeneous signal increase and this δ 13 C decrease in our record, as well as in other paleorecords, supports the hypothesis of a global aridification amongst others processes to explain the deep-water masses isotopic signature changes during the MPT. In any case, the isotopic shifts imply major changes in the end-member δ 18 O and δ 13 C values of deep waters.

Domaines: Sciences de la Terre

Bruno Malaizé, Elsa Jullien, Amandine Tisserand, Charlotte Skonieczny, Francis Grousset, et al.. The impact of African aridity on the isotopic signature of Atlantic deep waters across the Middle Pleistocene Transition. Quaternary Research, 2012, 77 (1), pp.182-191. ⟨10.1016/j.yqres.2011.09.010⟩. ⟨hal-03329205⟩