Sedimentary Record And Environment Evolution In South Coast Of Laizhou Bay From28Ka B.P

A borehole, named BH-2, drilled in south coast of Laizhou Bay,14.70m length, isemployed here for sedimentary process and environmental evolution. Compared withprevious work in study area, environmental evolution in other areas in North Chinaand the global climate change, sedimentary record, environmental change and drivingfactors are interpreted by using OSL dating method, grain size and clay mineral. Theresults show that1. Chronological framework of BH2, established mainly by OSL method, indicatesthe time limit of the14.70m length sediment is28ka. There is a sedimentarytransition in5.94ka B.P., with sediment rate highly increasing from0.14m/ka to1.97m/ka after this time. Compared with chronological framework of BH1and Lz908boreholes, this transition occurred widely in this area, mainly because of relative sealevel change and river discharge.2. Vertical change of this4types of clay mineral can be devided into3sections.Parent rocks were formed in low and very low metamorphism with the character ofcrystallinity of Illite, which is quanitified from0.198to0.399. Sediment from HuangRiver and loess from North Luzhong mountain are two important compositions.Vertical change of the number of swelling layer is consistent with the chemical index,show a potential information of environmental evolution.3. Grain size variations present sedimentary change, as grain size in pre-Holocene isfine, while that in Holocene is coarse. Mean grain size and standard deviation showthat with the sea level rising, the enengy of transportation in this area was in a quitelow level in a shallow sea environment, because of the mixture of current, wave andriver. Sea level falling led to a rapid deposition of river sediment, as the influence ofsea water decreased.4. The first factor of varimax-rotated Principle Component Analysis is the dominiting factor, as its contribution to variance of grain size is54.7%, while the contribution ofsecond factor is22.5%. F1score is consistent with fine grain size (<4μm), indicatingto the East Asian Winter Monsoon, while F2score is consistent with median-coarsegrain size (4~64μm), presenting to East Asian Summer Monsoon. EASM and EAWMare in-phase in the colder period, while the two are anti-phase in warmer period.