Climate forcing of terrigenous sediment input to the central Mediterranean Sea since the early Pleistocene
Résumé
Clay mineralogy of ODP Site 964 in the Ionian Sea was investigated in order to reconstruct variations in detrital sediment input to the central Mediterranean Sea and to reconstruct the corresponding climatic processes over the last 1500 kyr. The clay mineralogy of ODP Site 964 indicates a major shift in sedimentary sources from the Saharan Desert, which is characterized by a clay mineral assemblage of palygorskite–illite–kaolinite, to the Apennine Peninsula, characterized by an illite–smectite clay assemblage, at ~ 700 kyr. Prior to ~ 700 kyr, the low smectite content (10–20%) and the strong precessional cycles in the variations of kaolinite, illite and palygorskite indicate that terrigenous sediment to the central Mediterranean Sea mainly originated from Saharan dust and was strongly affected by the African monsoon, with a minor contribution of sediment deriving from the Apennine Peninsula. An increase in the illite/kaolinite ratio in the maxima of boreal summer insolation indicates a decreased dust input from the southern Sahara as a result of the northward displacement of the African Monsoon-ITCZ system. A gradual increase in smectite content has been identified between 1050 and 500 kyr, probably associated with environmental (vegetation) and/or hydrological changes in southern Europe linked to the occurrence of the MPT, and partly to tectonic uplift in the Apennine Peninsula. A marked increase in terrigenous flux is observed at around 350 kyr, coeval with a major phase of uplift in the Calabrian Arc.