Keywords: 
• Biological traces /
• Ichnology /
• Tidal flat /
• Pearl River Delta

Abstract: [Objective] Organisms are extremely responsive to the environments in which they live, and the traces they create are the result of interactions between organisms and environments, and to a certain extent reflect the characteristics of the depositional environment. Biological sedimentary structures are a powerful tool in understanding the ecology and depositional processes of modern coastal sedimentary environments. [Methods]The composition and distribution characteristics of modern biogenic traces in the tidal flat environments of the Pearl River Delta were studied by field observations and 3D reconstruction. [Results]The following key understanding was obtained after the study: the distribution of organisms in the supratidal, intertidal and subtidal varies greatly, and the biological traces are mainly distributed in the intertidal zone. In the supratidal zone, there are mainly Ligia oceanica and Uca arcuata, and the main traces created are Uca arcuata level feeding traces, excretion traces, trackways, and intra-layer I-shape dwelling burrows. Biological traces in the intertidal mud flat environment mainly include feeding, excretion, and trackways and I-shaped dwelling burrows at the level of Uca arcuata; crawling traces and Y-, U-, and I-shaped dwelling burrows at the level of Periophthalmus cantonensis; trackways and I- and Y-shaped dwelling burrows at the level of Orisarma dehaani. Biological traces in the mixed intertidal flat environment mainly include excretion traces and intra-layer I-, U-, and Y-shaped dwelling burrows of Perinereis aibuhitensis, Y-, U-, and I-shaped dwelling burrows of Ligia oceanica, and crawling traces of Vittina coromandeliana and Neritina pulligera. Biological traces in the sandy intertidal environment include feeding and excretion traces at the level of Ocypode cordimand and intra-layer I-shaped dwelling traces. The subtidal environment was not accessible for observation and no biological traces were found. [Conclusions] The research work on modern intertidal biological traces in the Pearl River Delta has not only supplemented the modern sedimentological data on tidal flat environments in the Pearl River Delta, but also provided modern empirical evidence for paleohermitology and paleoenvironmental reconstruction.