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 ( 8 7 Sr/ 8 6 Sr, δ 1 8 O, δ 1 3 C) composition. Coccolith 8 7 Sr/ 8 6 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 8 7 Sr/ 8 6 Sr. Geology 23, 403-406]) and similar to the 8 7 Sr/ 8 6 Sr values of Messinian evaporites (0.70887 to 0.70896 [Muller, 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 8 7 Sr/ 8 6 Sr values (0.709052) within the range for Early Pliocene seawater. However, unaltered 8 7 Sr/ 8 6 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 8 7 Sr/ 8 6 Sr values being quoted.