here are many silty dykes in peritidal silty muddy shales of the lower part of the Paleoproterozoic Chuanlinggou Formation at Jixian section in Tianjin. Particular configurations on bedding planes and on the surface perpendicular to the bedding planes lead to different explanations for the genesis of these silty dykes:(1)they are considered as the oldest trace fossils of metazoan according to the spindlecrack of siltstones on the bedding plane and the sandfilling tube configurations on the surface perpendicular to the bedding plane;(2)they are considered as the liquefied sandveins induced by earthquake according to the sinuous configuration of siltstone dykes on the surface perpendicular to the bedding plane and the obvious liquation feature. Several features indicate that these silty dykes were generated by the degassing and dewatering processes in the early diagenesis under the condition that the sedimentary surface was sealed by microbial mats， and can further be grouped into the microbial induced sedimentary structure(MISS). These features include:(1)the clear boundary being enriched with residue organic substance and the obvious fluidization feature shown by the relative accumulation of silty grains under the petrographic microscope;(2)the accompanied wrinkle structure and the palimpsest ripples which indicate the development of microbial mats on the sedimentary surface. 