Geoheritage values of consanguineous wetland suites on the Swan Coastal Plain,Western Australia

A wide range of wetland types occur on the Swan Coastal Plain of Western Australia. They vary from basins, and flats, to slopes and channels, and vary in size, shape, water characteristics, sediment types, stratigraphy, vegetation, origin, and maintenance processes. The wetlands range from large linear lakes to small round or irregular seasonally damp wetland basins to seasonally flooded flats, to seasonally flooded or permanently flowing channels. Salinity ranges from fresh to saline to hyposaline; and recharge mechanisms from perching of surface-water to wetting and inundation by groundwater, as determined by regional features such as geology, geomorphology, soils, climate and hydrology, and local physical/chemical processes. The Swan Coastal Plain presents a bewildering array, diversity, and complexity of wetlands, but patterns and ordering can be recognised if the wetlands are aggregated into natural groups. The wetlands, in fact, have been aggregated into natural groupings termed ‘consanguineous suites’, resulting in some 30 different formally named wetland suites related to geomorphic setting varying, for instance, from interdune depressions on a beach-ridge plain (the Becher Suite), to karst-formed linear lakes in limestone-ridge country (the Yanchep Suite), to irregular to round, semi-interconnected basins on a quartz sand subdued dune system (the Jandakot Suite), to linear and round basins formed along the hydrological contact between limestone and quartz sand (the Bibra Suite), among others. The variety of wetland types on the Swan Coastal Plain represents geodiversity that needs to be addressed in geoheritage assessments of the State of Western Australia. Further, as repositories of Holocene to Pleistocene sedimentary sequences, the wetlands present significant reservoirs of information on wetland history, climate changes, and hydrochemical history, and are templates on wetland maintenance and functioning, diagnostic for their geologic/geomorphic setting useful for management of wetlands in Western Australia, nationally, and globally. From a global perspective, the diversity and array of consanguineous suites of the Swan Coastal Plain is unique. An understated aspect of the approach in identifying consanguineous suites of wetlands of the Swan Coastal Plain is that in their geological, geomorphological, and hydrological/hydrochemical setting they provide profound insights into gradual and uninterrupted wetland development, sedimentary filling and ecological functioning because, for a given east–west transect, they are located in the same climate setting but in different geologic/geomorphic and hydrochemical settings. They appear to be unrepresented globally, and therefore, in terms of geoheritage, are internationally significant.