Abstract
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Along most coasts, fine-grained sediments are winnowed
away by wave and current action, and landforms are rocky,
or composed of sand or gravel. However, there are substantial
sections of coast that are dominated by muddy sediments,
either in sheltered locations where low-energy
marine processes dominate, or where the supply of silt
and clay-sized sediment is so large that there is a positive
sediment budget. These muddy coasts are distinctive for
several reasons. Firstly, fine sediment behaves differently
from sand and gravel; it takes a long time to settle, but
interactions between grains, such as flocculation, accelerate
deposition and promote the cohesion of mud once
deposited, meaning it requires significantly higher energy
to resuspend. Secondly, these muddy sediments support
significant biological activity, including organisms within
the sediment (infauna) that bioturbate the sediments,
organisms on the surface (benthic epibiota) that form mats
and help bind the sediment, and important macrophyte
communities in the upper intertidal zone. Thirdly, the
accumulation of mud provides a sedimentary record of the
gradual accretion that has occurred on these coastlines,
providing the opportunity for palaeoenvironmental
reconstruction
of past habitats and the way in which they
have responded to altered boundary conditions, such as
sea-level change (see Chapter 1).