Abstract
Globally mud areas on continental shelves are conduits for the dispersal of fluvial-sourced sediment. We address fundamental issues in sediment dynamics focusing on how mud is retained on the seabed on shallow inner shelves and what are the sources of mud. Through a process-based comprehensive study that integrates dynamics, provenance, and sedimentology, here we show that the key mechanism to keep mud on the seabed is the water-column stratification that forms a dynamic barrier in the vertical that restricts the upward mixing of suspended sediment. We studied the 1000 km-long mud belt that extends from the mouth of the Changjiang (Yangtze) River along the coast of Zhejiang and Fujian Provinces of China and ends on the west coast of Taiwan. This mud belt system is dynamically attached to the fluvial sources, of which the Changjiang River is the primary source. Winter is the constructive phase when active deposition takes place of fine-grained sediment carried mainly by the Changjiang plume driven by Zhe-Min Coastal Currents southwestward along the coast.
Highlights
There are eight types of mud deposition systems in the world based on the location of the depocenter on the shelf and their three-dimensional architecture
In this study we focus on a major mud deposition system on the inner shelf of East China Sea (ECS) that extends from the mouth of the Changjiang (Yangtze) River along the coast of Zhejiang and Fujian (Zhe-Min in brief in Chinese) Provinces into the Taiwan Strait (TS) and eventually terminates on the west coast of Taiwan (Fig. 1a)
Since the textural expression of this system on the seafloor is mud, we propose to call it Zhe-Min-Taiwan Strait Mud Belt (Z-M-TSMD)
Summary
There are eight types of mud deposition systems in the world based on the location of the depocenter on the shelf and their three-dimensional architecture. They include prodelta, subaqueous delta, mud patch, mud blanket, mud belt, shallow-water contourite drift, mud entrapment, and mud wedge[1] These systems are conduits linking the source (at river mouths), processes (waves, tides), and sinks (shelf depocenters on margins). Since fine-grained sediments are carriers of geochemical signals and environmental proxies[9], they preserve signals of river catchments and marine environments and the mud deposition systems act as archives of paleoclimatic and paleo- and modern-environmental changes and coastal evolution during deglaciation[10,11,12,13,14,15] Because of their archiving ability, they are sinks for terrestrial substances and pollutants[16,17,18], especially at depocenters. We combined the schematic maps of the mud areas based on data from Mainland China[24] and Taiwan[25,26] to make a schematic composite map to delineate the entirety of the mud belt system (Fig. 1a)
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