A new age model for the upper Miocene to Pliocene sedimentary section from Ocean Drilling Program (ODP) Hole 695A enables extrapolation of absolute ages of diatom datums and provides better understanding of paleoenvironmental conditions in the Weddell Sea. Sediment accumulation rates suggest the presence of a poly-thermal ice sheet in Antarctica during the early Pliocene. Peaks in abundance of Thalassionema nitzschioides and T. nitzschioides var. parva reflect fluctuations in the strength of latitudinal thermal gradients between the Antarctic and subantarctic sectors of the Weddell Sea and are correlated to intervals of climatic warming noted in the Kerguelen Plateau region of the Southern Ocean. (modif. auth. abstr.)