Abstract:

The Changzhougou Formation in the Proterozoic is a set of clastic rock unconformably on the Archean granite gneiss. On the coarse clastic rock of the bidirectional cross bedding lying on the bottom of Changzhougou Formation in Xingcheng, Liaoning Province, we found a large number of sandy microbial particles, size of which is between 0.1 mm and 0.2 mm, giving priority to spherical shape, as well as square and ship type. This paper argues that the cause of these sandy microorganisms particles is that the microbial matground in the relatively hydrodynamically quiet supratidal flat or high tide mud flat was damaged by the storm and tsunami disaster events by intense tectonic movement and high frequency sea level movement in the early transgression movement at the beginning of the Mesoproterozoic erathem. Then it was transported to the strong hydrodynamic and bimodal crossbedding developed area of the tidal channel with the tide flow and deposited with detrital material; in the process of transportation, these particles damaged by the storm were rounded and sorted. At the same time, on the basis of the primary sedimentary structure of these microbes and characteristics of sedimentary of the development of the Changzhougou Formation, we identified the formation environment of the Changzhougou Formation as the barrier islandtidal flat sedimentological system.

Key words: Xingcheng City of Liaoning Province, Mesoproterozoic erathem, sandy microorganisms particles, palaeoenvironment