Coasts

Form of sediment is highly dependent on the effect of tides, wave activity and degree of clastic input from rivers.

Microtidal coasts: Usually stormed dominated. Coastal areas are dominated by sandy barrier island features, elongate parallel to the coast. Length of island increases with decreasing tide strength. Reworked rapidly during storms that cause breaks in islands and wash over into the tidal lagoon. Storms are capable of washing large volumes of sediments out on the shelf, producing sheets 5-10 cm thick and up to 50 km across. Inlets through island migrate rapidly due to daily current activity, 10s of m per years. Sediments fine rapidly offshore into shelf muds. Modern examples: Dutch coast Texas Gulf Coast, Carolinas.

Irish Atlantic coast, dune fields

Macrotidal coasts: No barrier islands but instead tidal flats. Sandy sediments develop wave ripple lamination, large scale dunes around river estuaries. Mud flat develop sandy ridges (Cheniers) where occasional storms activity sorts and reworks the flat sediment. Reworking by burrowing organisms is common. Current directions vary within the tidal zone resulting in sands with cross bedding showing flow in two opposite directions. “Tidal bundles” are formed in inter-tidal zones, due to settling of mud drapes over sandy dunes and ripples during the high tide. Spring and neap tides of varying strength can be traced through the strength of development of the tidal bundles. Shallow offshore is characterized by sand ridges running parallel to the tidal flow. Modern examples, English Channel, Bay of Fundy Canada, East China Sea.

Coastal zone morphology

Beach erosion or sedimentation?

Makran coast, an uplifting coastline

Coastal sedimentology-only for the dedicated.

Tidal ranges and coastal morphology

Barrier island response to sealevel rise

Tidal inlets, effect of tidal strength

Barrier island response to storm

Barrier island-wash-over fan

Barrier island-inlet migration

Barrier island-sealevel model

Barrier island-differing responses to sealevel change

Barrier island-storm erosion

Galveston Island, map

Galveston Island, barrier island

Beach progradational stratigraphy

Beach seasonal erosion example

Beach seasonal erosion model

Cape Hatteras, Barrier Island system

Chesil beach, England, a classic storm beach

Chesil beach, England, high wave energy coast

Texas coast - sediment fining offshore

Tidal dunes, Eastern England

Sandy tidal flats - North Sea coast of England, macrotidal

Tidal marshes - North Sea coast of England, macrotidal

Tidal flat sediment types - 1

Tidal flat sediment types - 2

Tidal bundles - tidal sedimentation

Tidal bundles - clay drape evidence of tidal sedimentation

Herringbone cross bedding - tidal sedimentation

Wave rippling-tidal flats