Variations in the length and weight of Noelaerhabdaceae coccolith in the Late Quaternary tropical Western Pacific and their influencing factors

Sediment samples from core MD06-3050 in the Benham Rise in the Western Philippine Sea at the northern edge of the tropical Western Pacific Warm Pool were selected for Family Noelaerhabdaceae coccolith size analyses. Images were taken and synthesized using bidirectional circular polarization method. The average coccolith length and weight were automatically identified and measured by SYRACO artificial intelligence software. Results show that the average coccolith length and weight show strong similarities in the last 350000 years, with no obvious glacial-interglacial changes. The coccolith calcification index was estimated based on the length and weight of coccolith, and shows the same patterns of the morphological parameters, but presents a more obvious glacial-interglacial pattern. The coccolith calcification index was compared with the ice-core atmospheric pCO₂, which shows that the calcification of Noelaerhabdaceae coccoliths was weakened in the glaciation termination period and the early-middle interglacial periods when the atmospheric pCO₂ concentration was higher. The 23-ka filtering of the average coccolith length and weight agrees with the summer average solar radiation at 15°N, suggesting the regulation of the Earth's astronomical orbit parameters on the evolution of coccolithophores.