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They found that the large ion lithophile and light rare earth elements, especially K, Rb, Pb, Th, U, Zr and Nb correlated positively with terrigenous components, such as mica, rutile, tourmaline and zircon and with the maturity index of a sedimentary rock, while ferromagnesian elements Fe, Ti, Mn, Se and V and small cations Na, Ca and Sr correlates positively with chemically unstable components such as volcanic lithic, epidote and feldspar.
Elements which show no systematic variations with SiO2 or Al2O3 content reflect minor compositional differences in common terrigenous components and/or external factors such as biogenic input or secondary alteration processes.
As mentioned above, the relative contribution of the biogenic versus terrigenous components to the sediment can also be inferred through Ca/Al and Sr/Al ratios that are controlled mainly by fluctuations in the production and dissolution of the carbonate fraction and dilution by terrigenous inputs; yet Ca/Al and Sr/ Al are less commonly used as proxies of palaeoproductivity (Sun et al, 2008; Reolid et al, 2012).
The contents of terrigenous components are in general rather small, being variable in the lower and more stable in the upper part of the sequence (Fig.
2] (Dol), and terrigenous component (Ter) were calculated according to the following formulas suggested by T.