Figure 1. Climatology of the summer and winter monsoon circulation. Surface winds for the (A) winter (January) and (B) summer (July) seasons along with areas of high (H) and low (L) pressure, and precipitation (6 and >9 mm/day contours) for the (C) winter (January) and (D) summer (July) seasons. The pressure gradients and resulting wind and precipitation patterns reflect the land-sea heating contrasts, which are a function of solar radiation, elevation, and land surface boundary conditions. Monthly data for 1990-1997 from NOAA NCEP-NCAR CDAS-1 (Kalnay, et al., 1996).
Figure 2. Regional setting of the South China Sea (SCS) and the two areas of proposed coring locations (see Figs. 9 and 10 for closeups ofnorthern and southern drilling areas, respectively). Note that the SCS is connected to adjacent seas and the Pacific by shallow sills, with the deepest being the Bashi Strait (BS; 2600 m water depth).
Figure 3. Summary of some of the marine and terrestrial observations that indicate 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 radialarian 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 due to monsoon related weathering (data from Quade et al., 1989). C. Normalized, mean terrigenous sediment flux to the northern Indian Ocean that indicates active uplift and fluvial deposition in the late Miocene (from Rea, 1992). D. A model simulation of monsoon runoff using the Molnar model for uplift history (11-8 Ma) and the coupled effects of elevation change and orbitally-induced solar radiation changes (from Prell and Kutzbach, 1997).
Figure 4. The migration of the arid zones (black areas) in China during the Cenozoic. A. Paleocene. B. Neogene. C. The location of sites with paleobotanic and/or lithologic data (from Sun and Wang, pers. comm., 1998) that define the terrestrial climates.
Figure 5. Tectonic setting of
the South China Sea. A. Major tectonic elements of the
northern and central parts of the South China Sea. Thick dotted
line outlines the Central Basin with selected magnetic anomaly
lineaments. Thin dotted and solid lines are isobaths of 200 m and
2000 m (Hayes et al., 1995). Thick dashed box corresponds to
Figure 3. B. Geological framework of the northern margin
of the South China Sea (Ru et al., 1994). YGHB = Yinggehai Basin;
QDNB = Qiongdongnan Basin; BBWB = Baibiwan Basin; PRMB = Pearl
River Mouth Basin; SWTB = Southwest Taiwan Basin. Leg 184 sites
are located south of Dongsha Island on the continental margin
between the Pearl River Mouth Basin and the South China Sea
Figure 6. A composite stratigraphy from industrial wells in the eastern part of the Pearl River Mouth Basin, which lies on the shelf and uppermost continental slope northwest of the northern sites (PRMB in Fig. 5; see Fig. 9 for bathymetry). These wells provide the seismic reflector sequence and general age structure that we hope to correlate to the more marine ODP sites on the slope. Note the nonmarine sequence beginning from late Oligocene (modified from Jiang et al., 1994).
Figure 7. Conditions in the Western Pacific marginal seas at the last glacial maximum (LGM). A. Areas of emergent shelf (black) at the LGM (Wang et al., 1997). Area A = East China Sea Shelf; Area B = Sunda Shelf or the Great Asian Bank; Area C = Sahul Shelf or the Great Australian Bank. B. The patterns of SST seasonality (summer SST minus winter SST) in the South China Sea and its adjacent Western Pacific and marginal seas at the LGM (Wang, in press).
Figure 8. East Asian monsoon climate change in the northern SCS during the last glacial cycle from a core recovered during the SONNE 17940 cruise. The plots show are, from top to bottom, total grain size mode; clay content; stable oxygen isotope values from Globigerinoides ruber, and for reference, the oxygen isotope record from theGISO2 ice core. EHPB = Early Holocene/Pre Boreal; Y.D. = Younger Dryas; B/A = Boelling/Alleroed; O.D. = Oldest Dryas (data from Wang et al., in press).
Figure 9. Bathymetry of the northern margin of the SCS and the location of sites proposed for Leg 184 (solid circles). Contours are every 100 m. See Table 2 for exact locations and depths.
Figure 10. Bathymetry of the southern margin of the SCS and the location of sites proposed for Leg 184 (solid circles). Contours are every 100 m. See Table 2 for exact locations and depths.
Figure 11. Summary of water depths and expected ages of the intervals to be drilled during Leg 184. Also shown are the present day critical sill, lysocline, and CCD depths. Proposed Sites SCS 1 and SCS-2 form a Pliocene-Pleistocene depth transect, and SCS-4 and SCS-5C form a Miocene depth transect.
To 184 Site Time Estimates
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