Geological Environment of Trace Fossil Assemblage in Yanchang Formation, Ordos Basin

Abstract:

Through the filed profiles and the trace fossil assemblages from well core, we found that the lake stratums of Yanchang Formation in Ordos Basin were mainly developed in eight relics types: vertical dwelling trace (Skolithos and Cylindricum), vertical browsing trace(Scoyenia), Utube trace (Arenicolites), burrow trace (Planolites, Chondrites and Teichichnus), horizontal trace (Protopaleodictyon), escape trace（Fugichnia）, nekton trace and root trace. It is shown that the distribution and assemblage of trace fossils matches the sedimentary environment of the Late Triassic lake basin in Ordos Basin, reflecting the geological value of the restoration of lithofacies palaeogeography by the use of trace fossil assemblages.

Key words:Ordos Basin; Late Triassic lake basin; trace fossil; paleoenvironment