Foraminifera Assemblage Characteristics And Palaeoenvironmental Evolvement Of The Core Sys-0701 From The South Yellow Sea Since Marine Isotope Stage 3

Based on the identification and statistics of 194 samples from the core SYS-0701 in the South Yellow Sea, 121 benthic foraminifera species which belong to 59 genera and very few planktonic foraminifera, only 6 species in 5 genera, total up 31428 were recognized.Q-mode factor analysis was made for the 52 benthic foraminifera species, and 5 varimax factors with a cumulative contribution of 87.44% were picked out. The species have the highest score will be used to name the assemblages. AssemblageⅠ- Ammonia beccarii vars. represents a coast environment of less than 20 m water depth; AssemblageⅡ-Schackoinella globosa reflects a littoral environment during 20 and 30 m water depth; AssemblageⅢ-Ammonia maruhasii indicates a shallow-sea environment with 20 to 50 m water depth; AssemblageⅣ-Nonion akitaense reveals a littoral environment in 20 to 30 m water depth with low-temperature and low-salinity alongshore currents or clod water mass; AssemblageⅤ-Protelphidium tuberculatum - Elphidium magellanicum shows a shallow-sea environment between 20 and 50 m water depth with alongshore currents or cold water mass.Combined with the characteristic of benthic foraminifera evolution from the core SYS-0701, data of AMS¹⁴C, shallow seismic profile A22, grain curve in the core and the research results of the core QC2, the conclusion has displayed the paleoenvironme -ntal changes since Marine Isotope Stage 3(MIS3): MIS3 is the sub-interglacial in the last glacial with warmer and unstable climate. Foraminifera assemblages displayed a shallow sea environment during the MIS3, then the climate became cold and Yellow sea alongshore currents and cold water mass started to act. A22 shallow seismic profiles reflects the development of underwater delta in the MIS3. So we conclude that the sediment environment was distal delta front in early MIS3, and late environment had become a near mouth of the delta front deposition. A continental river sediment environment had become, and a large number of deep valleys developed in the Western South Yellow Sea in MIS2. MIS1 is the postglacial with warmer climate, and the environment was the shallow water. In early MIS1, the South Yellow Sea continental shelf was submerged to become shallow coastal environment, affected by the Yellow alongshore currents, and terrigenous materials were carried by ancient Yellow River and other rivers to fill the deep valleys formed in MIS2. The sea level rised the highest in mid-MIS1. In late period, climate changed cold slightly, and the sea level dropped to the level of modern shallow water.