Sedimentary Stratigraphic Framework And Environmental Evolution In The Coastal And Offshore Area Of Southern Shandong Peninsula During The Late Quaternary

The study area locates in the south of Shandong Peninsula and northwest ofSouth Yellow Sea. The South Yellow Sea is a typical semi-enclosed epicontinental seawith complicated depositional history. It had submerged by the sea for many times inthe late Quaternary history as a response to glacial cycles, which formed thecomplicated sea-land interactive deposits. There are plenty of informations ofdepositional environment characterstics and depositional evolution process insedimentary stratigraphy, through the study of which, it has great significance for usto understand the depositonal history of eastern China seas and paleo-envrionmentchanges, as well as provides important information for global climatic changes. Inaddition, through the study of coastal to shelfal sedimentary strata, it can play thelocational link function on the research and contrast to late Quaternary deposits of theland and deep sea as well as the ocean.Based on the core QDZ03and QDZ01and3046km high-resolution shallowseismic profiles recently acquired in the coastal and offshore area of southernShandong Peninsula, the article makes a detail division and discussion on thesedimentary structure since the late Quaternary.Core QDZ03is a fully coring drill locating in the shallow seismic profile. On theanalyses of lithology, micro-paleontolgy combination characteristic, grain sizecharacteristic as well as AMS14C and OSL dating, with contrast to the shallow seismicprofile, the core QDZ03is divided into5depositonal units, which are named DU1,DU3, DU4, DU5and DU6from up to down, of which environmental changes areto be interpreted happened during Holocene, MIS3to MIS2, MIS4, middle-late period of MIS5and MIS6or earlier. The same as above, the0-40.00m section ofcore QDZ01is divided into4depositional units, which are named DU2, DU3, DU5and DU6in descending order, of which environment changes are to be interpretedhappened during MIS2, MIS3, MIS5and MIS6.Based on interpretation of high resolution seismic profiles, using the contrastbetween seismic profiles and core QDZ03and QDZ01and the principle of sequencedivision, the seismic stratigraphy above the bedrock is divided into6seicmic untis,which are named SU1, SU2, SU3, SU4, SU5and SU6from up to down. Theseismic units are interpreted to be formed in Holocene, MIS2, MIS3, MIS4, MIS5and MIS6or earlier.On the basis of division of stratigraphic structure, this article focuses on theresearch of seismic unit SU1, which is the Holocene clinoform. The clinoform’sbottom boundary generally lies at15–40m below present sea level with its depthcontours roughly parallel to the coast and deepening seaward. The clinoform reachesits maximum thickness of22.5m near the coast and becomes thinner toward the sea,with its thickness contours generally parallel to the coastline. At the mouths of somebays, the clinoform takes the shape of a fan with its thickness greater than thesurrounding sediments. This clinoform came into being in the early Holocene, about11,200calibrated radiocarbon years before present (11.2cal kyr BP) and can bedivided into lower and upper depositional units (DU1-2and DU1-1, respectively).DU1-2, usually less than3m thick, formed under a low sedimentation rate, liesbeneath a Holocene maximum flooding surface (MFS), and represents the sediment ofa post-glacial transgressive systems tract; DU1-1, the main body of the clinoform,lies above the MFS and represents a highstand systems tract dating from middleHolocene time (about7–6cal kyr BP) to the present. The provenance of the clinoformsediment differs from typical sediments of the Yellow River and is interpreted as amixture of Yellow River and proximal coastal sediments of the Shandong Peninsula,with the Yellow River contribution increasing in the last1–2cal kyr BP. Theclinoform is coeval with clinoforms or subaqueous deltas off the northeastern Shandong Peninsula and in the northern South Yellow Sea, and it shares with them asimilar origin, history, and sediment provenance.Pollen analysis shows that the climate change process has undergo warm andwet-cool and dry-warm and dry-cold and dry-warm and wet since the lateQuaternary， and sea level experienced more than120m lift and down，and thesedimentary environment evolution experienced shallow sea to delta facies–terrestrial facies–coastal facies–fluvial facies and shallow sea facies.