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Relative palaeointensity (RPI) records can reflect the evolution of the Earth's axial dipole field and provide a suitable template for global stratigraphic correlation. Current RPI records are primarily obtained from the Atlantic and Pacific Oceans, particularly in the mid-latitudes of the Northern Hemisphere. Fewer RPI records originate from the Indian Ocean, particularly in low latitude areas, which limits sediment dating and geomagnetic evolution studies in these regions. In this study, we conduct a palaeomagnetic study on four sediment cores recovered from the western equatorial Indian Ocean (WEIO) to establish a new regional RPI stack from the past 500 ka for the global coverage of palaeointensity data, as well as a regional reference for palaeointensity-assisted stratigraphy. To estimate the RPI, the isothermal remanent magnetization is used as a normalizer. A chronological framework is constructed by correlating RPI records and environmental magnetic parameters (anhysteretic remanent magnetizationsaturation/isothermal remanent magnetization, ARM/SIRM) with PISO-1500 and LR04 δ18O curves, respectively. Our RPI stacked curve (WEIO-500) varies according to global and other regional high-resolution records. The five lows in the obtained RPI curve can be correlated with previously reported excursions. In addition, the mean inclination direction of each core is similar to the expected hypothetical geocentric axial dipole direction, with a negative inclination anomaly (mean Δ I) of −2.18° to −4.86°. The low mean Δ I and its reproducibility reflect the reliability of our chronological framework and stacked curve, thereby providing a new reference for correlating and calibrating RPI records from WEIO as well as other equatorial areas. [ABSTRACT FROM AUTHOR]

[Display omitted] • The non-carbonate sediments in the equatorial western Indian Ocean were mainly continental weathering materials. • Hydrothermal input contributed slightly to the sediments in the equatorial western Indian Ocean. • Significant Ce and Mn enrichment indicated a more oxidized environment due to the input of AABW. Sediments in the equatorial western Indian Ocean are mixed products from biological, terrigenous, autogenic, volcanic, and hydrothermal materials influenced by various circulation and water masses. The sediments record information of sources and sedimentary environments. To identify the different sources of non-carbonate components in the sediments of the equatorial western Indian Ocean and explore the factors influencing their sedimentary characteristics, surface sediments of the equatorial western Indian Ocean were analysed for clay minerals as well as major and rare earth elements following carbonate removal. Palygorskite, as an indicative mineral of aeolian dust from the North Africa-Arabian Peninsula, is ubiquitous in the sediment of the equatorial western Indian Ocean. These non-carbonate materials are mainly derived from the North Africa-Arabian Peninsula as well as the Indus River and Deccan Traps. The study area can be divided into two sedimentary zones according to the water depth, major element content, and related indexes of rare earth elements (δCe, δEu, LREE/HREE). The sediments of Zone II, being influenced by the Antarctic bottom water, are mainly calcareous clay and characterised by a significant positive Ce anomaly and relative MnO enrichment, with relatively high palygorskite, Al 2 O 3 content, and LREE/HREE ratio (mean values of 24%, 13.95% and 14.00). The sediments of Zone I are mainly clayey calcareous ooze, with a relatively weak positive Ce anomaly and a low palygorskite content (20%). Low Al/(Al + Fe + Mn) values in the sediments of Zone I demonstrate slight signs of hydrothermal input. This study revealed that continental weathering debris is an important source of non-carbonate sediments in the equatorial western Indian Ocean and established that the Antarctic bottom water is an integral factor affecting the sedimentary environment in this region. We present a complete regional sedimentological study of the equatorial western Indian Ocean and provide theoretical support for the reconstruction of the paleo-oceanic environment. [ABSTRACT FROM AUTHOR]

• The distribution of planktonic foraminifera was mainly influenced by the depth-controlled dissolution rate of carbonate, temperature, and salinity. • Strong correlations were found between the benthic foraminiferal distribution and organic carbon, the oxygen content, and the water mass. • Benthic foraminifera assemblage of Cibicidoides wuellerstorfi and Oridorsalis umbonatus indicated the influence and direction of oxygen-rich Antarctic Bottom Water. • The carbonate lysocline depth of the equatorial western Indian Ocean is ∼ 3900 m. • The western side of the Central Indian Ridge is relatively more productive than the eastern region, which reflects the influence of Seychelles-Chagos Thermocline Ridge. The numerous foraminifera in sediments near the equatorial western Indian Ocean act as historiographers that record abundant information about the marine environment. However, few studies have focused on the foraminiferal distribution in surface sediments within this area and the associated environmental and productivity implications. In this study, planktonic and benthic foraminifera were obtained from 28 surface sediments. The planktonic foraminifera were found to be mainly warm-water species; their distribution was mainly influenced by depth-controlled dissolution rate of carbonate, temperature, and salinity. Combined vertical distribution of foraminifera, fragment rate, resistant species rate, and Goborotalia menardii fragmentation index, the carbonate lysocline depth of the equatorial western Indian Ocean is ∼ 3900 m. The benthic foraminifera were mostly oxygen-rich and oligotrophic species. Their distribution and organic carbon, the oxygen content, and the water mass related. Four assemblages were identified: Assemblage 1, Cibicidoides wuellerstorfi , Oridorsalis umbonatus [indicative of Antarctic Bottom Water (AABW)]; Assemblage 2, Pullenia bulloides , Oridorsalis umbonatus (indicative of an oxygen-rich environment with intermediate to low productivity); Assemblage 3, Epistominella exigua , Turrilina cf. brevispira (indicating a pulsed organic matter input and seasonal fluctuations in productivity); Assemblage 4, Globocassidulina subglobosa , Astrononion novozealandicum (suggestive of a low-productivity environment). The overall productivity is low near the equatorial western Indian Ocean. The foraminifera species, TOC, and biogenic barium data show that the western side of the Central Indian Ridge is relatively more productive than the eastern region. These results can be used as a basis for reconstructing the distribution of paleo-AABW and productivity within the Indian Ocean. [ABSTRACT FROM AUTHOR]