Provenance and Environmental Changes Recorded in Holocene Sediments from the Southern Yellow Sea, China

Abstract

Marine sediments in marginal seas record information on provenance and environmental changes. We present high-resolution Holocene variations in carbonate based on bulk samples and various particle sizes of carbonate distribution, integrating benthic foraminiferal abundances and stable carbon and oxygen isotopic compositions from the 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 carbonate content revealed three phases of sedimentation over the past 11 ka BP. The highest sediment carbonate content (average 4.53%) occurred during the early Holocene. About 80% carbonate occurs in the <38 um grain size fraction, which combined with the low coastal saline benthic foraminifera (BF) assemblage indicating an offshore environment during stage III (11-10.1 ka BP). During stage II (10.1-6.5 ka BP), the contribution of carbonate of the <38 mm grain size fraction decreased to 60%, suggesting that the sediment supply from the Yellow River decreased slightly but increased as compared to that from the Yangtze River. This is also supported by stable carbon and oxygen isotopic compositions of BF. Moreover, the benthic foraminifera abundance increased during two peaks around 9 ka and 7.3 ka BP, corresponding to abrupt increases in sea level during melt water pulse (MWP)-1C and MWP-1D, respectively. The sea-level approached modern levels and formed a modern-day circulation pattern during stage I (6.5-4 ka BP). A period of non-deposition occurred over the last 4 ka BP, which is possibly related to the hydrological changes caused by the East Asian monsoon. Carbonate content, especially the carbonate content of different particle size fractions of the sediment can provide new insights on the evolution of Holocene environments on marginal seas, providing more information on the paleoenvironmental history of the Yellow Sea and past global changes.

Keywords: carbonate content, particle size, carbonate contribution, Benthic foraminifera, isotopic composition, Holocene