Coastal geoheritage: encompassing physical, chemical, and biological processes, landforms, and other geological features in the coastal zone

The coast is one of the most complex environments on the Earth’s surface, being a zone of intersection and interaction of land, sea, groundwater, and atmosphere and the processes therein, and carries processes and products that are either not present or only weakly developed elsewhere. With other matters such as lithology, structure, or geological framework being equal, the coastal zone is one that generally results in greater geodiversity than elsewhere. The range of interacting physical, chemical and biological processes in the coastal zone include: waves, tides, storms, and cyclonic activity (all resulting in erosion, sediment mobility, particle size sorting, sedimentary structures); development of a splash zone; onshore winds resulting in shore-directed wind waves and longshore drift, and in erosion, transport, particle sorting, lag deposits, and dune building; sedimentation mediated physically by fluvial influx, longshore and/or onshore transport, and tidal currents, or biologically by skeletal production; bioerosion; chemical erosion; salt weathering; tidal invasion of coastal sedimentary bodies by seawater; evaporation and transpiration; hydrochemical effects such as solution, or precipitation of carbonates, gypsum, or halite; fresh-water seepage and its effect on ecology and coastal erosion; sediment delivery fluvially; and biological effects including skeletal production, encrustation, biostrome and bioherm building, grain fragmentation, and bioturbation. A significant factor also is the prevailing nature of many of the processes therein. Coasts commonly exhibit shore-normal environmental gradients and hence a graded expression of processes, resulting in variation in complexity and geodiversity in physical, geochemical and biological products across the shore, and variation in fine- to small-scale stratigraphic sequences. To provide a perspective of the expression of any geodiversity of bedrock, and of the diversity and complexity of sedimentary systems in the coastal zone, selected coastal zones are compared with terrestrial environments for specific rock types, and specific sedimentary sequences – while there is overlap, coastal environments present greater complexity and geodiversity of physical, chemical and biological products. Because they interface with oceans, coastal deposits and coastal forms also can record a history of sea level, climate, and oceanic processes. It is the range of sedimentological and erosional features, expressed geomorphologically and stratigraphically along the coast, and their strength of development, that sets coastal geoheritage apart from continental (or inland) geoheritage