Coastal forms and Quaternary processes along the arid Pilbara coast of northwestern Australia

Abstract

Abstract The Pilbara coast is set in the most arid part of coastal Australia. This coast and coastal plain, composed of riverine plains, deltas, tidal flats, coastal dunes and limestone barriers, relic deltas and archipelago/ria shores, is predominantly a terrigenous and carbonate sediment complex. The coastal landforms therein formed during the Quaternary through influence of ancestral landforms and fluvial and shoreline accretion, coastal erosion, and cementation. The pre-Holocene features controlled development of Holocene coastal forms and a variety of Holocene depositional styles. Climate also plays a significant part in the coastal processes and in the generation of sedimentary products through high evaporation rates coupled with the limited rainfall, cyclonic storms, wind, wind waves, and the limited sediment delivery to the coastal zone. This results in a distinctive range of stratigraphic sequences and chemical products. As a result, this arid coast is characterised by a range of features such as construction of arid-zone deltas, delta destruction and sediment redistribution during times of sediment depletion, cyclone-induced erosion and sedimentation, mangroves and their associated sedimentary deposits, evolution of coastal groundwater hypersalinity, formation of salt flats, and precipitation and cementation to form beachrocks, high-tidal crusts and gypsum precipitates. The Pilbara coastal stratigraphy and geomorphology suggests aridity was intricately involved in the sedimentation, geomorphic evolution, and pedogenic and diagenetic alteration of this coastal zone throughout the whole of the Holocene and Pleistocene.