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Accueil > Recherche > Thèses / HDR > Thèses soutenues > 2017

04/07/2017 - YU Zhaojie

Indina monsoon paleovariability and its impact on weathering of the Himalaya.

  • Directeur : Christophe COLIN (IDES).
  • Financement : CSC UPSUD

The Neodymium isotopic composition (εNd) of seawater has been shown to be a new proxy to trace the water mass provenance and mixing. Nd is mainly in the dissolved form in seawater (90 to 95 %) with a concentration of about 10-12 g/g. Its residence time (about 500 - 1000 yr) is shorter than the time for inter-ocean mixing. Consequently, through lithogenic inputs, water masses are characterized by different εNd. εNd has been already used on seawater to establish hydrology of the deep and intermediate water masses of the Ocean. We propose to use this new proxy into the Bay of Bengal to track the present day hydrology of the Bay of Bengal and to assess the impact of the erosion of the Himalaya on εNd seawater of the northern part of the Indian during the late Quaternary. The main objectives of this PhD study are to analyze seawater samples and expanded marine sedimentary sections from the Bay of Bengal collected during the oceanographic cruise MONOPOL of the Marion Dufresne (May-June 2012) in order to reconstruct Indian Monsoon and weathering history of the Himalaya. We will use geochemical, mineralogical, and micropaleontological proxies in order to reconstruct the weathering history of the Himalaya of the late Quaternary in order to establish their relationship to changes in the intensity of the Indian monsoon rainfall and winds, and sea-level variations. A specific effort will be devoted to Nd isotopic composition in order to track the impact of weathering intensity on seawater Nd isotopic composition of the North Indian Ocean. For this project we will analysed REE and εNd of seawater samples collected in several water stations of the Bay of Bengal to establish the present time distribution of Nd in this part of the Ocean. In a last step, we will reconstruct past seawater εNd of the Bay of Bengal from εNd analyses on foraminifera.