| Provenance of the sedments is one of the major tasks of the madern sedimentary research. Also, it is a basic content of sedimentary geology. The provenance analysis has an important significance for determining the provenance locality, transportation route, sedimentation, and indicating depositional environmental changes as well. On the other hand, it has greatly practical significance for resource exploration and economic construction in the coast regions. REE of the sediments, mainly controlled by the parent rock, can be used to indicate the information of the parent rock. The sediments coming from the same source area are usually characterized by similar features of their REE. Therefore, the REE are tracer of the sediment origin.Based on the analyses of the REE compositions and sedimentary environments of the 2 boreholes, 40m for each, and comparison with potential provenance, this thesis discussed the provenance at the northwest Bohai Bay since the late Pleistocene Period.The geochemical element abundance is influenced by the grain size. In general, it is much coarser for the Borehole CH79, located in the north part of the studying area. Therefore, the contents of the REE are relatively small. By the contrast, Borehole XC66, located in the south, is relatively finer, therefore, the REE are much more abundant. This difference shows"Grain size effect on the elements".It is clearly, distribution of the element abundance in the west coast of Bohai Bay is influenced by the physical differentiation of the modern hydrodynamics. Measurements for bulk samples may be resulted in occurrence of the"Grain size effect", which will be misinterpreted provenance. In order to decrease the dilution effect of the coarse compositions, therefore, the samples, consisting of <0.063mm only, are measured in this thesis. Furthermore, the Al-normalization has been used for minimizing the"Grain size effect". As a subsided area, Bohai Bay has been a catch basin of numerous rivers. The origin of sediments in this area has three provenances, i.e. the Yanshan M, the Taihang M. and Huanghe. Variances of the geological background and parent rocks for such three provenances have differentiated elementary geochemical characteristics. Synergistic effect and mutual influence cause complexity of the provenances in the studying area.The REE, existing in the two boreholes, are normalized by chondrite and the North American shale, respectively. After the normalization, the two boreholes reveal concordance for the shape of the element distribution, which is quite similar with the compositions coming from the upper crust of the north China. So, it means that local sediments were terrigenours. Based on the REE abundance and parameters, comparing with the potential provenance, this thesis is able to indicate that the sediment origin of CH79 is relatively complicated and mainly come from the Yanshan M. However, this was affected by both the Taihang M. and Huanghe Rivers within different times. Borehole XC66, located in the south of the studying area, shows its sediments were basically run form the Huanghe R., with convergence of the Taihang M.Generally, provenances of the marine sediments in both cores are complicated. Influenced by rivers flowed into sea, and hydrodynamics,the REE of marine sediments may have remarkable difference. Conversely, the difference of REE of the terrestrial sediments is not as obvious as the sediments form marine.Alternation of various sedimentary depositions can produce fluctuation of the element compositions. Also, clear difference of the elements can be neutralized by mixture. Thus, it is puzzling our capacity to distinguish their provenances. For example, the mixture between Yanshan and Taihang Drainages may cause a similarity with the sediments form Huanghe R. Therefore, it is limited for geochemical analysis if the assessment is rarely given from REE. It is better to have comprehensive study with their back ground data available.
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