Geochemical analyses of various components (foraminifera, coccoliths and siliciclastic fractions) of limestone and marl samples from the marine Trubi Formation (Early Pliocene) of southern Italy revealed subtle diagenetic contamination. The coccolith fraction is altered from its original value both in its trace element (Sr/Ca, Mg/Ca, Fe/Ca, Mn/Ca, Na/Ca all were higher) and isotopic ( 87 Sr / 86 Sr , δ 18 O , δ 13C) composition. Coccolith 87 Sr / 86 Sr values (limestones 0.709010; marls 0.708951) are lower than those of coeval Early Pliocene seawater (0.709025–60 Farrell, J.W., Clemens, S.C., Gromet, L.P., 1995. Improved chronostratigraphic reference curve of Late Neogene seawater 87 Sr / 86 Sr . Geology 23, 403–406) and similar to the 87 Sr / 86 Sr values of Messinian evaporites (0.70887 to 0.70896 Müller, D.W., Mueller, P.A., 1991. Origin and age of the Mediterranean Messinian evaporites: implications from Sr isotopes. Earth Planet. Sci. Lett. 107, 1-12). Foraminiferal calcite is unaltered and retains its elemental and isotopic composition, with 87 Sr / 86 Sr values (0.709052) within the range for Early Pliocene seawater. However, unaltered 87 Sr / 86 Sr values were obtained only when the foraminifera were cleaned in acid to remove all contaminating coccoliths. Simple hand-picking and ultrasonic cleaning in water is inadequate to remove adhering coccoliths and may result in erroneous 87 Sr / 86 Sr values being quoted.