The Composition and Distribution Characteristics of Biogenic Sedimentary Structures in Tidal Flat of Yellow River Delta

Key words: 
• neoichnology /
• composition /
• distribution /
• tidal flat /
• Yellow River delta

Abstract: Ichnology in sediments is the result of interaction of organisms and environment,and it is a good indicator of both sedimentary and ecological environment. In this study,the results of fieldwork and experimental methods (box corer,grain analysis,X-ray computed tomography,three-dimensional reconstruction) revealed the composition and distribution of biogenic sedimentary structures in the tidal flat of the Yellow River delta. The two main results were:(1) The distribution of biogenic sedimentary structures varies at the micro-environment scale of the tidal flat. The biogenic sedimentary structures are mainly distributed in the intertidal flat. The abundance declines from mudflat to mixed-flat to sandflat. Specifically,there are feeding trails on the surface and Y-shaped and U-shaped burrows produced by Macrophthalmus japonicus in the supratidal zone. There are a number of feeding trail on the surface and Yshaped,U-shaped burrows produced by Macrophthalmus japonicus,crawling trails produced by Periophthalmus cantonensis,trails produced by Bullacta exarata on the surface,grazing trails produced by Nassarius succinctus,and a small number of crawling trails,grazing trails and vertical Y-shaped burrows in the mudflat. A large number of these occur in the sediment:grazing trails produced by Umbonium thomasi,vertical burrow produced by Mactra veneriformis Reeve,Bullacta exarata trails on the surface,and a small number of feeding trails and Yand U-shaped burrows in the sediment,grazing trails on the surface and Y-shaped burrow produced by Philyra pisum de Haan in the mixed flat,and vertical feeding and dwelling burrows of Solen gouldi,grazing trails of Turritella bacillum Kiener,and grazing trail produced by Nassaurius festiva.(2) We reconstructed the burrows of Macrophthalmus japonicus,Perinereis aibuhitensis and Mactra veneriformis Reeve to obtain three-dimensional images,providing an image basis for reconstructing the nature of burrows.