Abstract. Among various climate drivers, direct evidence for the Intertropical
Convergence Zone (ITCZ) control of sediment supply on the millennial scale
is lacking, and the changes in ITCZ migration demonstrated in paleoclimate
records need to be better investigated. Here, we use clay minerals and Sr–Nd
isotopes obtained from a gravity core on the Ninetyeast Ridge to track the
corresponding source variations and analyze the relationship between
terrestrial material supply and climatic changes. On the
glacial–interglacial scale, chemical weathering weakened during the North
Atlantic cold-climate periods and falling sea level hindered the transport
of smectite into the study area due to the exposure of Andaman and Nicobar
Islands. However, the influence of the South Asian monsoon on the sediment
supply was not obvious on the millennial scale. We suggest that the
north–south migration of the ITCZ controlled the rainfall in Myanmar and
further directly determined the supply of clay minerals on the millennium
scale because the transport of smectite was highly connected with the ITCZ
location; thus, the regional shift of the ITCZ induced an abnormal increase
in the smectite percentage during the late Last Glacial Maximum (LGM) in our
records. The smectite percentage in the studied core is similar to distinct
ITCZ records but different in some periods, revealing that regional changes
in the ITCZ were significantly obvious, the ITCZ is not a simple
north–south displacement, and closer connections occurred between the
Northern–Southern Hemisphere in the eastern Indian Ocean during the late
LGM.