Provenance and environmental changes recorded in Holocene sediments from the Southern Yellow Sea, China

Abstract

Marine sediments in marginal seas serve as valuable archives of provenance and environmental changes. In this study, we investigate high-resolution Holocene variations in carbonate content using bulk samples and different particle sizes of carbonate distribution. Our analysis integrates benthic foraminiferal abundances, detrital minerals, and stable carbon and oxygen isotopic compositions from a well-dated sediment core, C02 (34°59.89΄N, 122°0.03΄E; water depth 52.5 m), in the southern Yellow Sea mud deposits. The bulk sample analysis reveals three distinct phases of sedimentation over the past 11.2 ka BP. The highest sediment carbonate content (averaging 4.53 %) occurred during the early Holocene. The majority of carbonate (about 80 %) is found in the <38 μm grain size fraction, indicating an offshore environment during stage III (11.2–10.1 ka BP) characterized by low coastal saline benthic foraminifera assemblages. In stage II (10.1–6.5 ka BP), the contribution of carbonate from the <38 μm grain size fraction decreased to 60 %, suggesting a slight decrease in sediment supply from the Yellow River but an increase compared to the Yangtze River. Stable carbon and oxygen isotopic compositions of benthic foraminifera support this. Additionally, our study has revealed that benthic foraminifera abundance increased during two peaks around 9 ka and 7.3 ka BP, corresponding to abrupt sea level rises during meltwater pulses (MWP)-1C and MWP-1D, respectively. During stage I (6.5–4 ka BP), sea level approached modern levels, and a modern-day circulation pattern was established. A period of non-deposition occurred over the last 4 ka BP, possibly linked to hydrological changes driven by the East Asian monsoon. The carbonate content, especially in different particle size fractions of the sediment, offers valuable insights into Holocene environmental evolution in marginal seas. These findings are crucial for understanding the paleoenvironmental history of the Yellow Sea and past global changes, underlining the significance of our study.