Abstract
Bioturbation plays a critical role in sediment mixing and biogeochemical cycling between sediment and seawater. An abundance of bioturbation structures, dominated by Thalassinoides, occurs in carbonate rocks of the Cambrian Series 2 Zhushadong Formation in the Dengfeng area of western Henan Province, North China. Determination of elemental geochemistry can help to establish the influence of burrowing activities on sediment biogeochemical cycling, especially on changes in oxygen concentration and nutrient regeneration. Results show that there is a dramatic difference in the bioturbation intensity between the bioturbated limestone and laminated dolostone of the Zhushadong Formation in terms of productivity proxies (Baex, Cu, Ni, Sr/Ca) and redox proxies (V/Cr, V/Sc, Ni/Co). These changes may be related to the presence of Thalassinoides bioturbators, which alter the particle size and permeability of sediments, while also increase the oxygen concentration and capacity for nutrient regeneration. Comparison with modern studies shows that the sediment mixing and reworking induced by Thalassinoides bioturbators significantly changed the primary physical and chemical characteristics of the Cambrian sediment, triggering the substrate revolution and promoting biogeochemical cycling between sediment and seawater.
Highlights
Bioturbation is a biological process that results in the disruption of primary physical sedimentary structures, in particular, stratification (Qi 1999; Seilacher 1999)
Intense bioturbation characterized by Thalassinoides occurs in the middle Zhushadong Formation (Member II; Figs. 2, 3)
Thalassinoides are preserved in full relief in limestone of the middle Zhushadong Formation, where the boundaries between the burrows and the host rock are clearly visible
Summary
Bioturbation is a biological process that results in the disruption of primary physical sedimentary structures, in particular, stratification (Qi 1999; Seilacher 1999). The occurrence of high-density and deep-tier Thalassinoides mazes penetrating several storm layers in the Cambrian Stage 4 of China is evidence that the increasing sediment reworking ability of bioturbators significantly modified the primary sedimentary fabric, and efficiently created new ecological space (Qi et al 2014; Zhang et al 2017). The activities of deep-tier bioturbators, e.g. Thalassinoides, can transport solutes within burrows to the surface (Zhang et al 2017), and increase the water content in sediments by extending the sedimentwater interface area, and resulting in physical redistribution of nutrients (Aller 1994; Michaud et al 2005, 2006). The bioturbation of sediments by benthic macrofauna imposes major changes on important sediment biogeochemical processes, such as fluid exchange between the water column and sediment, sediment redox properties and nutrient cycling (Mángano and Buatois 2014; Zhang et al 2017). Burrowing animals significantly modify the primary sedimentary fabric, efficiently contribute to nutrient cycling and serve as ecosystem engineers (Mángano and Buatois 2014)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
