Tracking provenance change during the late Miocene in the eastern Mediterranean using geochemical and environmental magnetic parameters

Abstract

[1] 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 $8.2 Ma.

Source-to-sink magnetic properties of NE Saharan dust in Eastern Mediterranean marine sediments: review and paleoenvironmental implications

“…This fraction is large enough to include both pedogenic and lithogenic hematite grains, which can then reach the Eastern Mediterranean Sea as constituents of eolian dust. This is in agreement with the eolian origin that has been proposed for hematite in Eastern Mediterranean marine sediments by comparing HIRM data with proxies for Saharan dust supply, such as Ti/Al ratios (Larrasoaña et al, 2003a(Larrasoaña et al, , 2008Köhler et al, 2008;Liu et al, 2012b) (Figure 3).…”

“…These values indicate subtle magnetite concentration variations in background sediments (Figure 3). Magnetic data indicate that hematite is also ubiquitous in Eastern Mediterranean Sea sediments (Kruiver and Passier, 2001;Larrasoaña et al, 2003bLarrasoaña et al, , 2006Larrasoaña et al, , 2008Balsam et al, 2007;Köhler et al, 2008), as has also been shown by diffuse reflectance spectroscopy (DRS) data (Heslop et al, 2007;Liu et al, 2012b). Hematite abundances are typically inferred using HIRM or other properties aimed at isolating high-coercivity mineral signals (e.g., an alternating field-demagnetized IRM or IRM@AF) (Larrasoaña et al, 2003b(Larrasoaña et al, , 2006(Larrasoaña et al, , 2008Liu et al, 2012b).…”

“…Given the practical difficulties in applying magnetic fields that can saturate goethite, identification of this mineral has largely been based on DRS data (Heslop et al, 2007;Köhler et al, 2008;Liu et al, 2012b). DRS data suggest that goethite, although ubiquitous, is less abundant than hematite in Eastern Mediterranean marine sediments (Balsam et al, 2007).…”

“…Given the often discontinuous nature of the continental sedimentary record, these marine magnetic records of eolian dust deposition provide valuable sources of information on past climate variability in continental regions (Liu et al, 2012a). In the case of the Eastern Mediterranean Sea, magnetic records of eolian dust deposition have been used to provide novel information on paleo-environmental conditions in the neighboring Sahara Desert (Larrasoaña et al, 2003a;Köhler et al, 2008), which has important implications for better understanding paleo-monsoon dynamics (Trauth et al, 2009) and of any climatic influence on human evolution (Larrasoaña et al, 2013).…”

“…The areas that have provided the most outstanding records of eolian dust deposition based on magnetic properties are the equatorial Atlantic Ocean (Bloemendal et al, 1993;deMenocal, 1995;Maher and Dennis, 2001;Itambi et al, 2009;Just et al, 2012), the N Pacific Ocean (Doh et al, 1988;Yamazaki and Ioka, 1997;Yamazaki, 2009Yamazaki, , 2012Bailey et al, 2011), the eastern Mediterranean Sea (Dinarès-Turell et al, 2003;Larrasoaña et al, 2003a;Köhler et al, 2008;Liu et al, 2012b), the Arabian Sea (Bloemendal and deMenocal, 1989;deMenocal et al, 1991;Bloemendal et al, 1993;deMenocal, 1995;Hounslow and Maher, 1999), and the Red Sea Roberts et al, 2011) (for a review see Maher, 2011). Given the often discontinuous nature of the continental sedimentary record, these marine magnetic records of eolian dust deposition provide valuable sources of information on past climate variability in continental regions (Liu et al, 2012a).…”