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Accueil > Recherche > Thèses / HDR > Thèses soutenues > 2012

29/02/2012 : ZHAO Yulong

Restitutions des conditions climatiques passées de l’Afrique du nord et de l’hydrologie de la Méditerranée au cours des derniers cycles climatiques à partir de l’étude à très haute résolution temporelle de carottes marines

  • Directeur : C. Colin
  • Bourse du gouvernement Chinois et DRI UP11

Annually, great masses of fluvial and eolian sediments from permanent rivers and deserts in North Africa are transported into the Mediterranean Sea. These transport processes are tightly related to climate variability of adjacent landmasses, particularly changes in precipitation (i.e. erosion potential) of the Nile catchment and wind strength (i.e. deflation potential) of the Sahara Desert.

The total amount, as well as mineralogical and geochemical composition, of the marine sediments in the Mediterranean Sea, especially the eastern half, is therefore key to understand climate variability in North Africa.

- A lot of sedimentological and geochemical investigations of deep-sea cores, surface and core-top sediments, borderland riverine or deltaic sediments, and eolian dust samples in the eastern Mediterranean region have been done to investigate potential climate controls of detrital sediments in the eastern Mediterranean Sea. The existing records, however, are dedicated either to relative short time intervals or to the Pliocene epoch. There is hitherto no record of detrital sediments in the eastern Mediterranean basin that covers the whole Quaternary, a period that is characterized by rhythmic expansion and contraction of continent-sized ice sheets, rises and falls in global sea level, and not least, major glacial/interglacial shifts of the Earth’s climate. The objective of my thesis is to reconstruct a continuous high-resolution terrigenous record to the eastern Mediterranean Sea which penetrates the whole Quaternary.

By doing this, we attempt to reconstruct the history of climate changes in the northern Sahara, the Ethiopian Highlands, and the eastern Mediterranean Basin during the Quaternary and their possible links with the African monsoon.

The main material chosen in this study is one marine core on the distal Nile deep-sea fan (Core MD90-964) which covers the last 1.75 million years.

- Planktonic foraminiferal oxygen/carbon isotopes, carbonate and total organic carbon contents, and clay mineralogy and high-resolution element geochemistry (XRF Core Scanner) analyses are performed on the core sediments to achieve the aims. The preliminary results of our study show that the eastern Mediterranean region is affected by various factors that represent different climate procedures (Fig. 4). Nevertheless, the most significant climate system that affects the sources of sediments to the eastern Mediterranean basin is the African monsoon.