Abstract:

The stromatolitic bioherm in the middle part of the Furongian Fengshan Formation at the Lutonggou section of Hebei Province was masked by a bed of stromatolite bioherm, and formed forced-regressive system tract within three-order sequences of drowning unconformity type, which suggested the stromatolite developed in a medium-high energy coastal sea. Macroscopically, this bioherm consisted dominantly of columnar stromatolite with the ambiguous lamination. Microscopically, the bioherm was characterized by dense micrite and microspar, and it was well seen in bioherm that involved peloids, benthic oolites and aggregate grains, all of which represented complicated microbial activities, thus it differed from the Precambrian stomatolites. Furthermore, more lithocodium-like colonies of calcified cyanobacteria remnants and some filamentous calcified cyanobacteria fossils developed in the dense micrite matrix of the stromatolitic bioherm, and it demonstrated the microbial mats forming stromatolite were composed of mats leading by cyanobacteria. In general, the complicated and special carbonate sedimentary fabrics within stromatolitic bioherm of the Fengshan Formation provided a precious geological case for the understanding of complicated microbial metabolism in the growth of stromatolites.

Key words: stromatolite, bioherm, microbial mat, Fengshan Formation, Lutonggou section