The Biogenic Sedimentary Structures Of The Luanhe River Delta And Their Composition And Distribution Characters

Oil and gas reservoir resources are mainly related to delta sedimentary, however, due to the lack of boday fossils in the deltaic sediments, our understanding of the palaeoecological characteristics of the delta deposition system is deficient. Biogenic traces which is the record of biological activity in the sediment surface or its internal are good designator for the sedimentary environment.In this research, the modern Luanhe Delta was chosen for the neoichnology study in delta deposite. Through on-the-spot investigation, the morphological and ecological characteristics of the biogenic traces and their makers were observed, recorded, and compared with the similar ichnofossil. The distribution features of the modern biological traces were investigated. The modern ichnocoenosis was establish. The sedimentary and ecological environment characteristics were studied by test analysis. The physical control factors for the traces distribution and the relation between the ichnocoenosis and sedimentary environment were comprehensively analysised. The main results are as follows:(1) The morphological and ecological characteristics of the biogenic traces and their makers were carefully described.(2) Salinity, sediment and organic matter content and has important effect on morphology and distribution of the biogenic traces.(3) Four modern ichnocoenosis can be recognized in modern Luanhe delta: ?Ichnocenosis of freshwater lamellibranch feeding trails and mud beetles fodichnia reflects the fresh water controled wet deposite environments;? Ichnocenosis of mud beetles fodichnia and mole cricket burrow reflects the fresh-brinish water controled deposite environments ? Ichnocenosis of Nereid repichnia and crab burrow reflects tide controled tidal flat with slit-sand deposite environments. ?Ichnocenosis of nereid and crab burrow reflects the brinish water controled beach with corse-medium sand deposite environments.The results not only enrich the neoichnological research in China, but also provide the real empirical scientific basis for studying the ichnocoenosis and their formation background of delta sedimentary environment in geological history, and even for the ecological environment reconstruction.