Characteristics of the biogenic traces in the Lower Pearl River Delta Plain and their implication to paleoenvironment

Affected by both rivers and oceans, the Lower Pearl River Delta Plain has a wide variety of organisms and is sensitive to the environment, which reflects the characteristics of the sedimentary environment to some certain extent. By using three-dimensional reconstruction technology, the composition of biological traces in different microenvironments was studied n detail. The physic-chemical factors such as salinity, particle size, turbidity, and TOC in the biogenic traces were analyzed in the study area. Results are as follows. (1) The tracemakers in the study area included crustacean crabs, annelid Perinereis, bivalve river clams Corbicula fluminea, mudskippers Periophthalmus, and birds. Among them, the crabs and Perinereis were the main tracemakers. (2) The main biological traces in the study area included feeding and dwelling traces of Perinereis, dwelling and crawling traces of crabs, dwelling traces of Corbicula fluminea, dwelling and crawling traces of Periophthalmus, etc. The vertical burrows are mainly in I-, L-, Y- and U-shapes. (3) The burrow morphology in the study area was compared with the ichnofossils of Arenicolites, Cylindrichnus, Diplocraterion, Ophiomorpha, Palaeophycus, and Skolithos. They are analog with Skolithos ichnofacies. Meanwhile, the composition and distribution of the biogenic traces in the study areas were studied, and the distribution maps were analyzed. This study provided modern evidence for the sedimentological study in the Lower Pearl River Delta and implication to the identification of the ichnology and paleoenvironment in the ancient lower delta plain.