The Bioturbated Structures And Their Geochemical Features From The Zhushadong Formation Of The Cambrian Series 2 In Dengfeng Area Of Western Henan

The disturbance of benthic animals on bottom can change the stabilities of near-surface sediments,topography and sediment roughness,affect the characters of benthic communities,the redox properties of sediment,the decomposition rate of organic matter,the chemical properties of seawater and the recycling of nutrient in modern marine environment.It also significantly affects the biogeochemical cycling.Abundant bioturbated structures dominated by Thalassinoides occurred in carbonate rocks of the the Cambrian Series 2 Zhushadong Formation in Dengfeng area of western Henan.The determination of carbon and nitrogen isotopes combining the analysis of sediment mixing formed by modern bioturbators can help us to get a further information about the influence of ancient bioturbation to sediment biogeochemical cycle.The determination results show that there is a great difference of the?¹³C_carb value between the Thalassinoides burrow fillings and matrix and the value of burrow fillings is obviously higher than that of matrix.The value also display a dramatic difference in different bioturbated intensity which increase with the bioturbated intensity.The results mean that the sediment reworking of bioturbation can greatly change the redox property,porosity and permeability of sediments.The changes may be related to the decrease of the proportion of authigenic carbonates caused by the increase of oxygen content in sediment pore water and enhancement of dolomitization during diagenesis.The sediment mixing and reworking formed by Thalassinoides bioturbators not only have significantly change the primary physical and chemical information and promote the biogeochemical cycle between seawater and sediment,but may have efficiently triggered the substrate revolution,acting as ecosystem engineers as well.