Séminaire
Past interglacial periods can be seen as a series of natural experiments characterized by different boundary conditions (e.g. seasonal and latitudinal distribution of insolation, atmospheric greenhouse gas concentrations, extent of continental ice sheets), with different consequent effects on the character of climate change. Past interglacial are keys to understand past but also future-climate, because they represent potential analogues of the present warm period (Holocene) and offer the unique possibility to investigate the background of climate variability in which human-induced modifications operate, and to clarify their role in the natural sequence of events.
Continental carbonates (speleothem and lacustrine sediment) from the Mediterranean basin represent invaluable archives of past climate. Particularly, oxygen stable isotope composition of these deposits responds sensitively to variations in regional hydrology. This information can be complemented by the study of others properties (e.g. elemental and mineralogical composition), to obtain more detailed information on local environmental changes. In this talk, several case studies from central Italy lakes and caves are presented. They cover the Last Interglacial (ca. 130-90 ka), and the interglacial corresponding to the marine Isotope Stage (MIS) 19 (ca. 790-760 ka), considered the best orbital analog of the Holocene over the last million of years. All the presented records have independent, radiometric chronologies thanks to uranium-thorium dating of speleothem and to Argon/argon dating of volcanic ash layers interbedded to the lacustrine sediment. Climate evolution, hydrological response and millennial-scale variability are evaluated, and the potential link with the extra-regional and global climate is discussed.
julien.gargani@u-psud.fr