The Composition and Distribution Characteristics of Perinereis Trace Fossils in Tidal Flat of Pearl River Delta and Their Indicative Role in the Sedimentary Environment

Key words: 
• Pearl River Delta /
• tidal flat /
• neoichnology of Perinereis /
• sedimentary environment

Abstract: [Objective] The sedimentary environment of the Pearl River Delta is complex. with abundant Perinereis trace fossils. The characteristics，distribution and assemblage of Perinereis and their relationships with sedimentary environment and sediment properties are significant for the study of trace fossils and palaeoenvironment. [Methods] Based on sedimentary and ichnological methods, grain size analysis, salinity, turbidity, total organic carbon (TOC), X-ray scans, and three-dimensional (3D) reconstruction were applied to the modern biogenic sedimentary structures in different microenvironments of the Pearl River Delta tidal flat, discussed the composition，assemblage and distribution characteristics of Perinereis in tidal flat of Pearl River Delta, and analyzed the relationship between the biological assemblage and the sedimentary environments. [Results] 1) The Perinereis mainly lives in the tidal flat area of the tidal channel and the interdistributary bay in the Pearl River Delta. 2) The remains of the Perinereis mainly have grazing trails and dwelling trails, but the grazing trails on the layer are hard to observe, and the dwelling trails in the layer mainly have simple Y-shaped, I-shaped and U-shaped and complex network structures, and there are bulges at the joints. 3) The Perinereis is suitable for living in the tidal flat or tidal channel of the interdistributary bay with low hydrodynamic conditions, low salinity, low turbidity and rich total organic carbon content. [Conclusions] The spatial distribution of Perinereis’ neoichnology is imbalanced, and multiple environmental conditions jointly control the abundance of Perinereis’ neoichnology. The habitat of Perinereis is similar to the trace fossil Polykladichnus, which can belong to both the Mermia and Glossifunites ichnofacies, the trace fossil assemblage of this relic mainly appears in the channel and tidal flat area, and this study supplements the biological data of modern neoichnology of Perinereis.