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Figure F5. Accumulation rate (Gartner, 1990), clay mineralogy (Bouquillon et al., 1990), Nd isotopic data (Derry and France-Lanord, 1996; France-Lanord et al., 1993; Galy et al., 1996), and total organic carbon isotopic composition (France-Lanord and Derry, 1994), ODP Holes 717C and 718C. Ages recalculated using timescale of Cande and Kent (1992). Low sedimentation rates, smectite-kaolinite clays, and organic carbon derived from C4 plants characterize the interval from 7.4 to 0.9 Ma. Nd isotopic composition does not change during the entire time recovered, suggesting the eroded source of material is not significantly changing. Biostratigraphic constraints on sediment accumulation are uncertain for the early Miocene. The apparent increase in sedimentation rate near 12 Ma could be an artifact of poor biostratigraphic control prior to that time.

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