干旱区生态环境知识资源中心

Marls of the Metochia section (Gavdos, Greece) have been analyzed using geochemistry, environmental magnetism, and diffuse reflectance spectrometry to study late Miocene paleoenvironmental changes in the eastern Mediterranean region. Fuzzy c-means cluster analysis (FCM), combined with nonlinear mapping (NLM), has been performed on a multiparameter data set to identify and characterize terrigenous source areas from North Africa and the Aegean margin. The parameters included in the FCM were selected on the basis of their univariate characteristics and their ability to trace input changes from regional source areas. The hard isothermal remanent magnetization (HIRM), calculated on a carbonate-free basis, and the Ti/Al ratio are used to distinguish aeolian dust and transport mechanisms of material originating from North Africa. Mass accumulation rates of Al and Ni are employed to represent the input of terrigenous material originating from the Aegean region. CaCO(3), calculated from Ca abundance, provides information concerning marine productivity and Mn/Al is used to trace reductive diagenesis in the marls. After performing the FCM and NLM analysis, a four-cluster solution has the greatest stability and describes paleoenvironmental changes in both the African and European source areas. The cluster solution clearly reveals the change from input dominated by terrigenous material in the lower parts of the Metochia section to marine input at the top of the section but also reveals changes in paleoenvironmental conditions in North Africa from arid to more humid conditions at similar to 8.2 Ma.