| Based on observation of field profiles, study of facies markers in rock profiles and paleontology, and analysis of geochemical data, it is suggested that in Yanshan area, Mesoproterozoic Gaoyuzhuang and Wumishan Formations are a set of marine carbonate rock bedded locally with marine clastic rock,in which there are obvious rhythms and cycles and various stromatolite structures. The formations can be divided into carbonate terrace facies and biohermal facies, and can be further subdivided into tidal flat and baffle-bond reef subfacies and into four microfacies: supratidal zone, intertidal zone, subtidal zone and baffle-bond reef. Among these subfacies,the carbonate tidal flat subfacies is dominat ed and baffle-bond reef subfacies only develops in the 9th and 10th Members of Gaoyuzhuang Formation. A sediment tation model of carbonate rock is established. Through statistical analysis on trace elements (V, Rb, Sr, Ba, Be and B) and invariable elements (Al, Si, Fe, Mg, Ca, K, Mn and P) in different sedimentary environments, it is shown that geochemical features of the carbonate rock are closely related with primary sedimentary environment in this area, which can be used as the effective mark to identify sedimentary environments. |
