The Composition And Distribution Characteristics Of The Biogenic Sedimentary Structures In Yellow River Delta

The composition and distribution characteristics of modern biogenic sedimentary structures in the Yellow River delta plain and the delta front area are studied.The trace makers and their traces and burrows morphology are observed,and their related substrate,deposit environment and ecological environment are studied.Taking the three-dimensional reconstructed images of crab Macrophthalmus japonicus and worm Perinereis aibuhitensis as examples,this paper makes an analogy study with similar trace fossils,summarizes the characteristics of ichnocoenosis,and analyzes their substrate,sedimentary environment and ecological environment characteristics.There are four results:(1)The composition and distribution of modern biogenic sedimentary structures are observed in the Yellow River delta(except prodelta),including 15 species of trace makers.The trace makers in Yellow River delta plain includes: Mud beetle,Mole cricket,Red worms,Spider.The trace makers in Yellow River delta front includes:Macrophthalmus japonicus,Perinereis aibuhiteusis,Bullacta exarata,Periophthalmua cantonensis,Umbonium thomasi,Philyra pisum,Nassarius Succinctus,Nassaurius festiva,Solen gouldi,Mactra veneriformis,Turritella bacillum.(2)The ichnocoenosis of Yellow River delta plain and Yellow River delta front are summarized:(1)grazing trail produced by Mud beetle and Red worms ichnocoenosis in fresh water humid sedimentary environment;(2)grazing trail and crawling trail produced by Macrophthalmus japonicus and grazing trail produced by Bullacta exarata ichnocoenosis in brackish water sedimentary environment influced by river and tide;(3)grazing trail and burrow produced by Perinereis aibuhiteusis and burrow produced by Mactra veneriformis ichnocoenosis in salt water sedimentary environment dominated by tide.(3)The distribution of modern biogenic sedimentary structures is influenced by the grain size,exposure time,salinity and hydrodynamic condition.(4)By comparing the three dimension reconstructed burrow images of Macrophthalmus japonicus and Perinereis aibuhiteusis with analogous ichnofossils,this paper provides a realistic basis for the behavior study and the reconstruction of sedimentary environment of analogous ichnofossils.