Evolution of clay minerals assemblages since Late Pliocene and its paleoenvironmental implications: Evidence from Core XT4 of the Philippine Sea Basin

Clay mineral assemblage data of Core XT4 from the Philippine Sea Basin in the western Philippine Sea is used by this paper as proxies to trace sediment provenance and transporting mechanisms so as to constrain past changes in Asian eolian input to the basin since 3.7 Ma. The clay minerals consist of illite (39%) and smectite (28%), with minor chlorite (18%) and kaolinite (15%). Provenance analysis suggests that smectite are sourced predominantly from the alteration of local volcanic rocks, while illite, chlorite, and kaolinite primarily derived from the central Asia continent by eolian origin. Thus, the illite/smectite ratio can be used as a proxy to seek for Asian dust input to the Philippine Sea Basin since 3.7 Ma, and to reconstruct the aridification history of the source region. On the whole, the illite/smectite ratio from Core XT4 shows three stages variation pattern, reflecting the glaciers expansion in the high latitudes of the Northern Hemisphere. This led to the intensification of drought in the middle latitudes of Asia. Within the three stages, the illite/smectite ratio is inversely related to the change in East Asian Summer Monsoon (EASM). The eolian dust flux carried by EAWM on tectonic timescales may be also controlled by the underlying surface conditions, which is in turn influenced by EASM rainfall. Our results preliminarily reveal the environmental evolution of arid and semi-arid areas in China since Late Pliocene, which is helpful to understand the dust cycle under the multisphere interaction and its biogeochemical effect.