Recognition of cyclic and non-cyclic environmental changes in the Mediterranean Pliocene: A palynological approach

Abstract

The interval between 2.8 and 2.3 Ma B.P. from the south Italian Singa section has been investigated for its dinoflagellate cyst and sporomorph contents. In order to facilitate palaeoenvironmental interpretation the following curves are derived from the data: the ratios, sporomorphs/dinoflagellate cysts, Protoperidinioid/Gonyaulacoid dinoflagellate cysts, warm/cold water indicating dinoflagellate cysts, inner neritic/oceanic dinoflagellate cysts, outer neritic/oceanic dinoflagellate cysts and the reworked dinoflagellate cysts per gram of sediment. Furthermore, the already available δ 18O curve has been used. Calibration of changes in the sporomorph/dinoflagellate ratio against the computed astronomical insolation curve, leads to an improved age-assessment for the section. Frequency analysis on the curves shows the 23, 41 and 100 ka frequency components to be most important. Phase and amplitude differences between the filtered 23, 41 and 100 ka frequency components are used for environmental interpretation. The 23 ka frequency band is best explained by changes in runoff induced transport. The 41 ka frequency components are classified in a group with short response time to orbital forcing and a group with longer response time. Those signals having a short response time are attributed to local, precipitation induced changes in runoff. Those signals having a longer response time are mainly attributed to changes in global temperature and to a lesser extent to changes in global ice volume. Finally, longer term cyclic and non-cyclic changes are mainly attributed to temperature and sea-level variation.