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Why do some continental shelves accumulate muddy sediments?

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continental shelf The broad, gentle pitch of the continental shelf gives way to the relatively steep continental slope. The more gradual transition to the abyssal plain is a sediment-filled region called the continental rise. The continental shelf, slope, and rise are collectively called the continental margin.

Continental shelves accumulate muddy sediments primarily when the supply of fine-grained material from rivers is sufficient to overcome the winnowing effects of wave energy and currents.1

The type of sediment found on a continental shelf is determined by the interplay between tectonic setting, the volume of sediment delivered by rivers, and ambient wave energy. On many shelves, high-energy forces like surf, storms, and monsoons typically rework the seafloor, winnowing out fine-grained materials and transporting them away from the shelf.1

However, muddy deposits accumulate on shelves where rivers draining large continental areas deliver enough sediment to keep pace with sea-level rise or to dominate the local wave-energy conditions. In these environments, the influx of silts and muds is high enough that these fine particles can settle and remain on the shelf surface rather than being carried into deeper waters. Conversely, shelves that lack large river inputs or are dominated by high-energy wave regimes are typically veneered with sand or erosional debris.1