Mineralogical and Nd-Sr isotopic data from the Red Sea and the Gulf of Aden sediments
|Author(s)||Rojas Virginia P.1, Meynadier Laure1, Colin Christophe1, Bassinot Franck1, Miska Serge1|
|Affiliation(s)||1 : Université de Paris, Institut de physique du globe de Paris, CNRS, F-75005 Paris, France|
|Keyword(s)||Radiogenic isotopes, Clay mineralogy, Bulk mineralogy, Red Sea, Gulf of Aden, Last glacial period, African humid period|
Cores MD92-1002 and MD92-1008 were retrieved during the MD73 REDSED campaign of R/V Marion Dufresne in 1992 and are located in the western Gulf of Aden and southern Red Sea, respectively. The aim was originally to identify sediment sources thanks to the use of radiogenic isotopes. The sedimentary record in both cores presented large magnetic susceptibility peaks, which had been measured by Bouilloux et al. (2013), and these variations could have been caused either by source changes or by postdepositional processes. Nd and Sr isotopes vary depending upon rock types, and magnetic measurements can reflect lithological variations. Therefore the relationship between these parameters, can allow us to discriminate between source-driven changes and diagenetic processes that could induce variations in the magnetic signal. The studied basins are situated in a region influenced by the Asian and African monsoons, which had temporal variations. It is also one of the major regions of dust deposition, being near the Saharan and the Arabian deserts. Source determination of sediments in the basins can help us understand modern and past atmospheric pathways and relate them to climate variations. Using sediment cores that cover at least 20 ka enables the study of the last climatic cycle, i.e. the Last Glacial Maximum (LGM), the deglaciation and the present interglacial period. To further constrain the type of sources of the sediments being carried to the Red Sea and Gulf of Aden basins we also performed DRX analyses to measure the relative proportions of minerals in the bulk fraction and in the clay fraction. The clay fraction is a minor part in these sediments, however clay minerals are derived from weathering of the continents and they allow us to understand past environmental conditions. The combination of all these different tracers can help us decipher the mechanisms of sediment transport and link them to environmental variations during the Quaternary. X-ray diffraction (XRD) analyses were performed using a PANalytical X'Pert Pro Diffractometer (GEOPS Laboratory, Université Paris-Sud). Errors in mineral percentages were estimated to be around 1-2%. Sr and Nd isotope analyses were carried out on 22 carbonate-free samples from each core at a sampling resolution of around 40 cm. Nd and Sr isotopic compositions were analyzed using a Thermo Finnigan Neptune Multiple Collector Inductively Coupled Plasma Mass Spectrometer (MC-ICP-MS) at the GEE Laboratory, IPGP (Paris, France). The results are published in Rojas et al. (2019) https://doi.org/10.1016/j.quascirev.2019.02.033.
|Acknowledgments||This work was supported by the MONOPOL ANR project (n° ANR 2011 Blanc SIMI 5-6 024 04). Parts of this work were supported by IPGP multidisciplinary program PARI, and by Region île-de-France SESAME Grant no. 12015908.|