The PI's will delineate the involvement of intermediate water circulation changes in relation to the initiation of northern hemisphere glaciation by monitoring "middle" Pliocene circulation in the Atlantic and Pacific oceans with benthic foraminifera C-13 comparisons. Three depth transect will be used to reconstruct intermediate water during the middle Pliocene: the Rio Grande Rise (DSDP Leg 72), the Queensland Plateau (Leg 133) and the Bahamas.