Figure 4. Marine and terrestrial observations indicating an intensification of the monsoon in the late Miocene (10-8 Ma) and a model simulation of a possible evolution of monsoon runoff. A. Abundance of planktonic foraminifer Globigerina bulloides and radiolarian Actinoma spp. that indicate active upwelling induced by southwest monsoonal winds (from ODP Site 722, Arabian Sea). B. Oxygen and carbon isotopes measured in pedogenic carbonates from Pakistan indicating more seasonal climates and a decrease in atmospheric CO₂, possibly from monsoon-related weathering (data from Quade et al., 1989). Open circles = delta¹³C (‰); solid circles = delta ¹⁸O (‰). C. Normalized, mean terrigenous sediment flux to the northern Indian Ocean that suggests active uplift and fluvial deposition in the late Miocene (from Rea, 1992). D. A model simulation of monsoon runoff, relative to control simulation, using the Molnar model for uplift history (11-8 Ma) and the coupled effects of elevation change and orbitally induced solar radiation changes.

Figure 5

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