This figure (after Fig. 8 of Deng et al., 2006, EPSL, v. 241, p. 255), shows correlation of magnetic hardness of the Jingbian loess/paleosol sequence with the marine oxygen isotope records. (a) SIRM. (b) MDF_SIRM. (c) SIRM_100mT/SIRM. (d) SIRM_100mT/ SIRM_30mT. (e) SIRM_100mT/ SIRM_60mT. (f) Composite d¹⁸O records. The d¹⁸O curve is a composite record of V19-30 (0 to 0.34 Ma) [Shackleton and Pisias, 1985], ODP 677 (0.34 to 1.811 Ma) [Shackleton et al., 1990], and ODP 846 (1.811 to 2.6 Ma) [Shackleton et al., 1995a, b]. These results show that the ratios of SIRM_100mT/SIRM, SIRM_100mT/SIRM_30mT and SIRM_100mT/SIRM_60mT all display a long-term up-section oscillatory decreasing trend in both glacial and interglacial periods over the Quaternary period. This long-term trend is attributed to a long-term decrease in the relative contributions of eolian hematite during glacial extrema and of pedogenic hematite during interglacial extrema. This long-term variation pattern is then interpreted to reveal a long-term decreasing trend in chemical weathering intensity in both glacial-stage source region (the Gobi and other deserts in northwestern China) and interglacial-stage depositional area (the Loess Plateau region) over the Quaternary period. This long-timescale variation also indicates a long-term increasing aridification and cooling during both glacial extrema in the source region and interglacial extrema in the depositional area over this period. In addition, the three ratios and the composite marine oxygen records show good correlation between glacial-interglacial climatic oscillations and/or long-term trends. In summary, the up-section gradual decrease of those ratios over the entire Jingbian loess/paleosol sequence possibly reflects an increasing aridification and cooling of the climate system in the Asia interior over the last 2.6 Myr.

References

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