A multiproxy approach for reconstructing environmental responses to climate variability in western Mediterranean over the last deglaciation

Resumo

This Thesis provides a high-resolution paleoclimate and paleoceanographic reconstruction for the past 20 ka in the western Mediterranean, obtained from a multiproxy approach in a suite of marine and continental sediment records. Previous work in this region has demonstrated the rapid response and high sensitivity of the Mediterranean region to the North Atlantic oceanic and atmospheric processes. Nevertheless, most of the previous studies have focused on one or very few records and the comparison between different basins and between marine and continental realms has not been fully addressed. Thus, this thesis aims to compare the climatic and sedimentary signals from different sub-basin in the western Mediterranean, and from marine and continental sedimentary records in order to provide new insights into the evolution of the western Mediterranean climate since the end of the Last Glacial Maximum to the present. To do so, diverse geochemical proxies have been obtained at high-resolution from seven marine records located in the Algero-Balearic and Alboran basins, and from one alpine continental record in Sierra Nevada. Major and trace element composition as well as elemental ratios in hemipelagic marine sediments support that the relative variation between terrigenous and carbonate fraction at suborbital scale is controlled by the deep current intensity while the surface productivity, the sea level variations and the riverine and eolian inputs have a minor influence. A palynological study was also performed in the alpine wetland record, which has provided a detailed environmental reconstruction of vegetation variations during the Holocene. The stable carbon and hydrogen isotopic composition measured in long-chained n-alkanes has been obtained in two of the studied marine records located in the eastern and western Alboran basins, which are influenced by different river catchments demonstrating the importance of sedimentary processes in the organic matter deposition.