Orbital variations in planktonic foraminifera assemblages from the Ionian Sea during the Middle Pleistocene Transition

Abstract

The Middle Pleistocene Transition (1.2-0.7 Ma) is the most recent re-organization of the global climate system which includes variations in the frequency and amplitude of glacial/interglacial cycles, increased ice sheet volume, sea surface temperature cooling and a significant drop in the CO2 atmospheric levels. Here we present high-resolution planktonic foraminifera data (mean sampling resolution of about 780 years) from core LC10 recovered in the Ionian Sea (eastern Mediterranean), between 1.2 and 0.9 Ma. Selected taxa, among them G. ruber, T. quinqueloba and G. bulloides, show significant periodicities that can be associated to orbital cycles, mainly precession and obliquity. The planktonic foraminifera based paleoclimatic curve exhibits a cooling linear trend that can be associated to similar phenomena observed in the North Atlantic. On the other hand, we refer to the influence of the North African Monsoon the occurrence of two peaks of the low-salinity tolerant species G. quadrilobatus that fall in coincidence of sapropel layers. Finally, we discuss the distribution pattern of N. pachyderma sinistral coiling, with peaks up to about 20% between MIS 30 and 28, and compare it to middle-late Quaternary records of the Sicily Channel and western Mediterranean.