Sedimentary Characteristics And Sources, And Environmental Indications Of Late Quaternary In The Central North Yellow Sea

The North Yellow Sea which besets between Chinese mainland and Korea peninsula is a typical semi-closed shallow sea on continental shelf . In the littoral plain region and the adjacent continental shelf neritic province the incompact sediment layers had come into being since late Quaternary period, the thickness of which is from decades meters up to hundreds meters. Also during this time the climatic changes in temperature are frequent and the sea level changed greatly more than ten times. The sedimentary environment in this area is very complex and the multiplicative benthal sediments forming by the synthetical effect of diversified oceanic force, such as tideway, stormy waves and circumfluence, make up of the unique sedimentary character for this area. Based on the analysis of sedimentology on surface and core sediment of sedimentary area in central continental shelf and geochemistry, the thesis separately analyses the characteristic distributions of modern surface sediment and the lengthways distributions of sediment for different ages. And the significance of ancient circumstance and the information of sources , reflected by the sedimentary character, is elicited preliminarily. All of these indicate that the depositional pattern of study area is mainly controned by the variance of hydrodynamic conditions. Since the granularity constituent of sediment is the most distinctive indicate, which can reflect sedimentary effect, sedimentary circumstance, especially sedimentary driving condition, the thesis make a particular disquisition on the grain characteristic of the surface sediment. The analytic result for 103 grain samples indicates that the sedimentary types of surface sediment include gravelly sand, medium sand, fine sand, very fine sand, silty sand, sand-silt-clay, shaly sand, clayer silt and silty clay. According to the distributing characters of those sediments, the three sedimentary areas are measured off ulteriorly,therer are south silty sedimentary area, northeast sanded sedimentary area, northwest relict sedimentary area. And via analyzing the sediment samples on the granularity, mineral, and the constituent and distributing character of element, it was detected that the sedimentary character of surface sediment are mainly controlled by the sedimentary environments and source. The south area is effected by the water circulation of Yellow Sea, and the hydrodynamic power is more feeblish, so the sediment in this area is relatively fine, the content of heavy minerals is high . And from south to north, the grain is from fine to coarse by degree, which indicates the gradual increasing of hydrodynamic power. The North edge and most of the northeast area is effected by the strong tideway and the sediment are mainly medium sand, fine sand, very fine sand.the sediment in northeast is mainly coarse, the light minerals 'contents of feldspar and quartz are high. Due to the northwest area(section C)is just in the eroding circumstance, the unsymmetrical exposal of sediment in the late Pleistocene results in the different types of embedded sediment, such as very fine sand, silty sand, sand-silt-clay. Since the sample of surface layer only can provide the neoteric information, in order to probe into the ancient geological circumstance of Quaternary period, we must carry through the study of the deep stratum. Therefore, the thesis analyze the typical column sediment on their types, granularities, the age of C14, and the distributing character of the micro-paleontology in the stratum, and discussed the evolutive disciplinarian of ancient circumstance in researching area since late Quaternary period by coalescent with partition of pelagic foraminifer isotope stratum. According to the comparative results of column samples, the samples in researching area opened out the sediment of oxygenic isotope 3rd late phase, oxygenic isotope 2nd phase, and oxygenic isotope 1st phase. In oxygenic isotope 3rd late phase, researching area is delta environment, in oxygenic isotope 2nd phase, that is mainly the sediment environment of sea facies alongshore, such as firth and delta...