Direct correlation of the marine oxygen isotope record with the Chinese Loess Plateau iron oxide and magnetic susceptibility records

Abstract

Monsoons are a major feature of global atmospheric circulation and derive heat and moisture from the oceans and transports much of that heat and moisture to nearby continents. The east Asian Monsoon derives its heat and moisture from the eastern equatorial Pacific and transfers it to Southeast Asia and the Loess Plateau of central China. In order to examine the phasing of marine and terrestrial climatic events associated with this monsoon we have analyzed a core from the western Pacific, V21-146, downwind from the Loess Plateau. Iron oxides and magnetic susceptibility were analyzed because they have been used as Loess Plateau paleoclimate proxies. Comparison of temporal changes in both iron oxide and susceptibility signals in V21-146, to the well-known Luochuan loess section, reveals an excellent correlation, both in the timing and direction of the variations. Comparison of our Loess Plateau paleoclimatic proxies in V21-146 to previously published oxygen isotope data from this core suggests that through Marine Isotope Stage (MIS) 9, coincident with Loess Plateau interglacial soil level 3 (S3), ocean temperature increases and the onset of monsoonal conditions on the Loess Plateau were synchronous. However, for MIS 11/12 (interglacial/glacial S4/L5) changes in the ocean appear to significantly lead those on land and there is a lack of correlation between MIS 13 and S5. These out of phase events may be a response to a reorganization of the ocean/atmosphere system as indicated by changes in the δ 13C record. It has previously been suggested that changes in eolian flux record eolian transport from the Loess Plateau, but we find little correlation between eolian flux and our Loess Plateau proxies, suggesting that some of the eolian sediments were derived from outside the Loess Plateau.