Abstract
Bioturbation plays a substantial role in sediment oxygen concentration, chemical cycling, regeneration of nutrients, microbial activity, and the rate of organic matter decomposition in modern oceans. In addition, bioturbators are ecosystem engineers which promote the presence of some organisms, while precluding others. However, the impact of bioturbation in deep time remains controversial and limited sediment mixing has been indicated for early Paleozoic seas. Our understanding of the actual impact of bioturbation early in the Phanerozoic has been hampered by the lack of detailed analysis of the functional significance of specific burrow architectures. Integration of ichnologic and sedimentologic evidence from North China shows that deep-tier Thalassinoides mazes occur in lower Cambrian nearshore carbonate sediments, leading to intense disruption of the primary fabric. Comparison with modern studies suggest that some of the effects of this style of Cambrian bioturbation may have included promotion of nitrogen and ammonium fluxes across the sediment-water interface, average deepening of the redox discontinuity surface, expansion of aerobic bacteria, and increase in the rate of organic matter decomposition and the regeneration of nutrients. Our study suggests that early Cambrian sediment mixing in carbonate settings may have been more significant than assumed in previous models.
Highlights
Bioturbation plays a substantial role in sediment oxygen concentration, chemical cycling, regeneration of nutrients, microbial activity, and the rate of organic matter decomposition in modern oceans
Precise evaluation of the actual impact of bioturbation early in the Phanerozoic has been hampered by the lack of detailed analysis of the functional significance of specific burrow architectures preserved in the fossil record
Integration of ichnologic and sedimentologic evidence from North China shows that intense bioturbation, mainly revealed by the ichnogenus Thalassinoides, took place in nearshore carbonate sediments during the early Cambrian, providing evidence of significant infaunalization and sediment mixing
Summary
Bioturbation plays a substantial role in sediment oxygen concentration, chemical cycling, regeneration of nutrients, microbial activity, and the rate of organic matter decomposition in modern oceans. Our study suggests that early Cambrian sediment mixing in carbonate settings may have been more significant than assumed in previous models Bioturbation, involving both particle and solute transport within burrows, into the surrounding sediment and across the sediment-water interface, is one of the most important factors in affecting oxygen concentration in the sediment, chemical cycling, regeneration of nutrients, microbial activity and the rate of organic matter decomposition in modern oceans[1,2,3]. Integration of ichnologic and sedimentologic evidence from North China shows that intense bioturbation, mainly revealed by the ichnogenus Thalassinoides, took place in nearshore carbonate sediments during the early Cambrian, providing evidence of significant infaunalization and sediment mixing Comparison of these burrow architectures with modern counterparts allows evaluating the role of these deep-tier bioturbators in sediment www.nature.com/scientificreports/. Two well-preserved trilobite faunas assigned to the Palaeolemis Zone and Redlichnia chinensis Zone indicate a late early Cambrian age (Cambrian Age 4)[8,9]
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