Trace fossils from lower Cambrian Hongjingshao Formation, Yunnan, China: Taxonomy, palaeoecology, palaeoenvironment

The Hongjingshao Formation (Cambrian Series 2, Stage 3) yields abundant, complex trace fossils that have not been systematically investigated up till now. Our detailed ichnological study of the traces from this formation in Malong area, Yunnan, China, recognizes four groups: (1) simple horizontal or sub-horizontal burrows; (2) complex branched burrow systems; (3) arthropod trails and; (4) simple vertical burrows belonging to the Cruziana ichnofacies. A trophic web is reconstructed for the community in Hongjingshao Formation based on both trace and body fossils. The ichnological and sedimentological features of the formation indicate an intertidal setting. The trace fossil assemblage demonstrates that Early Cambrian organisms were able to colonize very shallow marine environments, which further supports the landward expansion of the Early Cambrian ecosystems.