HIGH RESOLUTION QUATERNARY SEISMIC SEQUENCE STRATIGRAPHY AND PALEOENVIRONMENTAL EVOLUTION IN THE NORTHERN SOUTH CHINA SEA: HIGH RESOLUTION QUATERNARY SEISMIC SEQUENCE STRATIGRAPHY AND PALEOENVIRONMENTAL EVOLUTION IN THE NORTHERN SOUTH CHINA SEA

Abstract

Based on the high-quality seismic profiles acquired from the northern South China Sea(SCS),we performed a detailed seismic sequence stratigraphic study.Correlation of the results with core samples and logging data from ODP Leg 184 and other deep sea records have been carried out to detect the difference and connection between geological and geophysical research methods,so as to reconstruct the sedimentary history of this area.About 14 seismic horizons are recognized by thin-bed tracking and seismic terminations analysis(including onlap,downlap,toplap,and truncation),including six continuous boundaries,three discontinuous boundaries,and five local boundaries.Then six seismic sequences are established.Detailed analyses of their reflecting characters,top and bottom ages,thickness and sedimentary rate helped build a Quaternary seismic stratigraphic framework at a resolution of ~10 ka.Consistency between seismic profiles and drilling data of ODP Sites 1144 and 1146 indicates that high resolution seismic analyses can produce a direct,detailed and reliable stratigraphic division scheme better than the traditional petrographic description sometimes.The correlation of seismic sequence framework with deep sea sediment records suggests that most of the reflector boundaries correspond to glacial periods or colder intervals of interglacial periods.6 continuous boundaries corresponding to large glacials in the Quaternary were identified.Besides,the seismic sequence results are correlated well with the climate change revealed by different proxies in marine sediment such as oxygen isotopes,carbon dust deposition,and water-layer structure.The most typical is SB 6 equivalent to the Middle Pleistocene Transition,a remarkable global climate event found in marine sediment,ice core,loess and geomagnetic records.Our results prove that integrated geological and geophysical researches can bring up a better understanding to the sedimentological evolution history of the studied area.