GEOLOGICAL IMPLICATIONS AND APPLICATIONS OF STROMATOLITE

Stromatolite is regarded as biogenic sediments. There are divergent views on its geological implications. Some geologists emphasize that it is controlled by depositional environments and cannot be used in stratigraphical division and correlatiom while some maintain that it can be regarded as an index fossil. According to the results of the study of a large quantity of stromatolites col- lected by the author on a regional scale together with other results available, it is considered that as stromatolite is controlled to a certain extent by depo- sitional environments it is difficult to determine the ages of the strata and correlate them according to the disappearance of a certain genus and species. It is particularly the case with those strata whose rook facies and thickness vary greatly. As stromatolite also exhibits a direct proportional relation, it is necessary to integrate the data on a regional scale and the neighbouring assem- blages in the entire sequence. For example, from the Changzhougou Forma- tion to the Dahonggu Formation in Changcheng System, from the Jixian stra- totype section westwards, both lithofacies and thickness change greatly （excluding the Chuanlinggou Formation）. As viewed in the light of the change of stroma- tolite in the Duanshanzi Formation, various forms of Gruneria and Yanshania and Kussiella tuanshanziensis may only range up to Miyun; while Xiayiegella may range up to Changping; however, Cornoconophyton rugiformis and Collum- nacollenia in the lower part of the Duanshanzi Formation, Muskroomia sta- phophormis in the middle part and Gaoyuzhuangia at the top are commmon in the entire Yanshan area, while stromatolite is absent in the very thick sedi- ments of the Chuanlinggou Formation, in the vicinity of Jixian and Tulong. On the other hand, Nordia and Eucapsiphora are common from Pinggu and Miyun westwards to Xuanhua and southwards to the Taihang Mountains area, where the strata become thin abruptly. The Gaoyuzhuang Formation is cele- brated for the persistence of the lithofacies and thickness; Conophyton cylind- ricum, Tabuluconigera, Confusoconophyton and Gaoyuzhuangia are prevalent in it. This indicates that it is not right to establish the type stromatolite assmeblages of various beds only according to the data of a single section for the strata whose lithofacies and thickness are highly variable, but after they are verified, corrected and supplemented according to the results gained on a regional scale, the data still remain significant in stratigraphieal division and correlation.