Evolution And Provenance Of Sedimentation On The Off-shore Shelf Of The Western Yellow Sea Since The Late Pleistocene

In this paper, unsubstantial field and area is chosen carry out our research. First, theseismic data on the Western South Yellow Sea and sedimentological and foraminiferdata the core SYS-0804sediments, to reveal their stratum and sedimentaryenvironment, so as to build the precipitation process and depositional system on theresidue deposition area of western south Yellow Sea since the late pleistocene. Thatwill lead to comprehensively comprehend on sedimentary evolution of the Westernsouth Yellow Sea since the late pleistocene. Second, Synthesizing the data of heavyminerals, light minerals and carbonate minerals from the sediments of core SYS-0701and clay minerals from sediments of the core SYS-0804, formed during MIS5-MIS1to reveal their provenance and influencing factors, so as to better understand thesediment sources and related environmental changes since late Pleistocene on theshelf of the western South Yellow Sea. Based on the data of oxygen isotope andcarbon isotope of the benthonic foraminifer in the core NYS-102on Wedge shapedsedimentary body of the northern Shandong peninsula off-shore, the sedimentaryenvironment evolution and sediment response on sea level fluctuations since the lastDeglacial was studied.Based on the lithology characteristic, AMS14C dating, micropaleontology of thecore SYS-0804on residue deposition area of western South Yellow Sea and combinedwith the Previous research results such as high-resolution seismic data, lithologycharacteristics of the core SYS-0701, SYS-0702and SYS-0803, AMS14C dating andoptical stimulated luminescence (OSL) dating to build the chronostratigraphic stratumof this area. Comprehensive analyses of high resolution seismic profiles andSYS-0804cores reveal the sedimentary sequence of the western SYS in response to sea-level changes since MIS6, with six characteristic bounding surfaces formedduring MIS5through MIS1. The strata formation and sedimentary environmentpreserved in the core SYS-0804including the epicontinental sea sedimentationinfluenced by the Cold Water Mass during early MIS5, coast and epicontinental seasedimentation during the late MIS5, the fluvial deposition during MIS4, coast andepicontinental sea sedimentation during MIS3and early MIS1transgression.Sea-level fluctuations, climatic changes, sediment supply, and shelf physiographyhave all been important factors controlling the shelf to coastal sedimentation and itspreservation in the western SYS during the Late Pleistocene.Core SYS-0701was recovered from the western South Yellow Sea. The previousresearches on the core focused on the sedimentology and chronology, revealing thesea-level changes and sedimentary evolution during the late Quaternary in the region.Based on the mineralogical data of the core section deposited since Marine IsotopeStage (MIS)5, the present paper aims to decipher the provenance of sediments ofsince MIS5and influencing factors of sediments mineral assemblage on the shelf ofthe western South Yellow Sea, so as to better understand relationships betweensediments mineral assemblage and the sediment supply and the environmentalchanges. According to the vertical content fluctuations of both heavy and lightminerals within a size fraction of0.25-0.063mm and carbonate minerals in bulksamples in addition to lithologic features, the upper part of core SYS-0701can bedivided intofive units named as DU1, DU4, DU5DU6and DU7respectivelyfollowing the nomenclature of previous literatures. The DU4(DU4-1and DU4-2)and DU1(DU1-1and DU1-2) could be further subdivided into two sub-units each.DU1was deposited during MIS1, and DU4and DU5were formed during MIS3. Allthe data of dominant heavy mineral assemblages, diagnostic minerals, ratios ofdiagnostic minerals such as ZTR, ATi, GZi and RuZi index indicate that the sedimentsof core SYS-0701are comparable with the Yellow River sediment. Light mineralassociations, textural maturities (quartz/feldspar), QFL diagram of light minerals,carbonate contents and ratio of dolomite and calcite also indicate that the sediments ofcore SYS-0701are comparable with the Yellow River sediment. All the features of detrital mineral assemblage indicate that the sediments in core SYS-0701mainlycame from the Yellow River provenance. The clay mineral assemblages of the coreSYS-0804is illite-smectite-kaolinite–chlorite which is similar to the Yellow Riversediments. The the triangular map with end members of illite, smectite andKaolinite+chlorite shows that the sediments of the core SYS-0804is close to theYellow River sediments. The mineral characteristic of the core SYS-0701andSYS-0804indicated that the sediments in the western SYS are derived largely fromthe Yellow River since the Late Pleistocene.Based on the data of oxygen and carbon isotope of the benthonic foraminifer(Elphidium asiaticum (Cushman) and (Ammonia beccarii (Linne）var.) in the coreNYS-102on Wedge shaped sedimentary body of the northern Shandong Peninsulaoff-shore, the paleosalinity of the studied area was calculated. Combining with the sealevel fluctuations since the last Deglacial we discussed the sedimentary environmentevolution of north Yellow Sea. At the early stage of deglacial, the paleosalinity wasabout3.24‰which was obviously affected by the fresh water from the Yellow River,and the studied area was the nearshore subtidal zone sedimentary environment.During the9.8-9.0cal kyr BP of the stage Meltwater pulse(MWP)-1C, thepaleosalinity of the the northern Shandong Peninsula off-shore rose up to26.6‰from3.24‰and the studied area was the Continental shelf shallow sea sedimentaryenvironment which was becoming more open and high salinity. After the Holoceneclimatic cooling and catastrophic sealevel-rise event, which occurred at8200cal BP,the paleosalinity of studied area have risen up to modern level from26.6‰. The depthof sea water exceed20m after7500cal yr BP and the content of Ammonia beccarii(Linne) var. decreased rapiddy. After6.5cal kyr BP, this region may affected by theYellow Sea warm current that bring ocean seawater with high salinity and dilutedWater that come from the Yellow River or stream nearby, so the value of salinityfluctuate frequently which lead to fluctuate the oxygen isotope.