The Discovery of Trace Fossils from the Lower Triassic Shabaowan Formation in the Guiyang Region,Guizhou and Their Significance

The abundant trace fossils are of widespread occurrence in the upper part of the Lower Shabaowan Formation in the Guiyang area, including four genera: Arenicolites. Psilonichnus, Skolithas and Thalassinoides. In addition. the Y-shaped burrows have also been identified in the formation, indicating that biologic activity may be traced in the course of deposition of the formation and that the water body in which the bottom beds were deposited may not be in a reducing environment. Occasionally, a small amount of pyrite are scattered in the limestones which contain the trace fossils, but this doesn＇t mean that the environments of the sedimentary rock beds which comprise a small amount of pyrite may be ascribed to the reducing ones. In fact, pyrite may result from diagenetic processes.
The“shallow-water”trace fossils—intraformational burrows have been recognized in the Shabaowan Formation which is ascribed to the shallow-sea shelf sediments. It follows that the trace fossil assemblages are not absolutely controlled by water depth, because the characteristics of the trace fossils are dependent not only upon water depth, but also upon bottom bed types, energy levels, food suply, preservation potential and the habits and characteristics of the organisms.