Early Pleistocene records of carbonate burial and terrestrial input in the Timor Sea and their paleoclimatic implications

Deep-sea carbonate burial is an important carbon sink of the Earth’s surface carbon reservoir. Its variations are closely related to that of atmospheric carbon dioxide. Paleo-environment reconstructions show that changes in atmospheric CO₂ concentration do not always correlate well with past temperature changes, implying that other factors may contribute to the past global change. We examined deep-sea sediments spanning the interval of 2～1.07 Ma retrieved from IODP Site U1482 located offshore northwestern Australia in the Timor Sea. Carbonate and elemental contents were analyzed to investigate the factors that influenced carbonate burial. The early Pleistocene records at Site U1482 indicate that all of our records including carbonate content, potassium content (a proxy of regional precipitation), log(Zr/Rb) (a proxy of aeolian dust input), benthic foraminiferal δ¹³C, and uranium content (proxies of paleoproductivity) show long-term changes punctuated at 1.63 Ma and 1.31 Ma, possibly related to the precipitation pattern over Indonesia-Australia modulated by Walker and Hadley circulations. The continuous decrease in carbonate content and increase in potassium content after 1.31 Ma likely implicate that the intensified aridification in the northwestern Australian hinterland was caused by strengthening of the Hadley circulation. Dilution by terrestrial sediments, mainly of riverine origin, is the predominant factor modifying carbonate content on orbital timescales. Spectral analysis shows that the carbonate record was dominated by 19 ka and 29 ka cycles, likely suggesting the effect of the obliquity-paced glacial/interglacial cyclicity on the regional precipitation and terrestrial input in addition to the precessional control.