Figure F6. Continental signal. Relative contributions of freshwater diatoms (FD), chrysophycean cysts (CC), and phytoliths (Ph) based on the assumption that 100% continental signal is equal to the sum of individual percentages. PhFD index of Jansen and van Iperen (1991) vs. precessional oscillation of boreal summer insolation (July) at 15°N (data from Berger and Loutre, 1991). Head bars and columns denote SPECMAP oxygen isotope stages.