Warm saline deep water production in the middle Eocene to early Oligocene Ellen E. Martin Dept. of Geological Sciences University of Florida Understanding the changes in weathering style and intensity associated with development of the Antarctic ice sheet has important implications for the global carbon cycle. Seawater Nd and Pb isotopes from Site 738 in the Indian sector of the Southern Ocean illustrate anomalies that coincide with intervals of ice rafted debris (IRD) (top figure). Evaluation of Pb isotopes from the seawater and sediment residues indicates that congruent, chemical weathering dominated during the greenhouse interval prior to ice sheet development, while mechanical, incongruent weathering dominated after the establishment of the ice sheet (bottom figure).