INVESTIGATION OF CONTROLLING FACTORS FOR GROWTH IN STROMATOLITES OF THE MIDDLE NEOPROTEROZOIC WUMISHAN FORMATION,YONGDING RIVER VALLEY,BEIJING
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Abstract:
A large amount of stromatolites occur in the Wumishan Formation of Yongding River Valley in Beijing，which provide great materials for this study．In order to investigate the controlling factor for growth in stromatolites，the shape of stroma-tolites was measured and analyzed，and the radar map of dominant growth directions of stromatolites was gained，and then it was combined with the location of the North China palaeoplate，the direction of palaeo-currents inferred from ripple-mark structures，the direction of palaeo-tectonic stress．This study indicates that the growth of stromatolites of Wumishan Formation in Zhuang-huwa Section，Yongding River Valley was not controlled by sunlight mainly，because the location of North China palaeoplate was near the equator，and the main controlling factor was palaeo-current．Besides，soft-sediment deformations toward the deep sea induced by the seismic activities which were caused by palaeo-tectonic stress overlaid on stromatolites influenced the shape of them，and siliceous chert filling damaged stromatolites subsequently．By analyzing the controlling factors for growth in stromatolites，we can understand the mechanism of growth of stromatolites and the palaeoenvironment，it has important ecological significance．
