The Mineralogical Characteristics Of The Sediments And Its Environmental Significance In The Beibuwan Gulf

Beibuwan gulf is located in the northwest of South sea in China, with three sides surrounded by land, which is affected less by the ocean tides and wave current, but affected significantly by the east Asian monsoon. Based on the research of seabed clay and detrital sediments in the Beibuwan gulf, the seabed sediment mineral composition, distribution and mineral environment logo are proved in the Beibuwan gulf, in order to understand great significance of palaeoclimate reconstruction and monsoon research.Through studying the 325 clay and detrital samples from 312 surface sediments and 35 columnar sediments in the Beibuwan gulf, XRD analysis of clay minerals, determination of detrital minerals and 14 C dating of 20 samples from 9 sediments columnar are processed.The clay minerals of Beibuwan gulf are mainly I/S, Kaolin, Chlorite and Illite, especially large distribution area of I/S. The(I+C)/I/S parameter is a good logo to reflect the ancient climate. The distribution of the heavy minerals of surface sediments in Beibuwan gulf is along the coast with heavier minerals and is zonal from north to south with lighter minerals. This paper puts forward that the distribution of heavy minerals in this area has five types. The ZTR, stability index, Mc/Q, TF/Q, P/F parameters and so on are also calculated. The result shows that the TF/Q and P/F, ZTR, stability index and Mc/Q has three similar change trends, respectively. The 14 c dating of the sediments in the study area shows that the age of surface sediments are within 2700 a, the age of the columnar samples along the shadow coast are within 10000 a BP and the age of the columnar samples of deep western sea area are older, for example 24545 a BP with B123 sample. The source of sediments in Beibuwan gulf is mainly from adjacent land. The sediments from Zhujiang and Honghe rivers are also enter into the Beibuwan gulf along the Beibuwan circulation with counterclockwise throughout the year. The clay and detrital minerals record the palaeoclimate change. This study shows that the TF/Q parameter is especially more sensitive to environmental change than clay minerals(I + C)/I/S parameter does. And the stereogram of parameters may more clearly reflect the distribution of minerals in Beibuwan gulf. The distribution of clay and detrital minerals in Beibuwan gulf reflects the palaeoclimate change of source area. The climate change of columnar samples may be in good corresponding with the warm and cool weather events in China and around world.