Potential Geoheritage Values of Landscapes in the Australian Drylands

In this study, the landforms of Australia's desert country are assessed against National Heritage criteria. The landforms are grouped and discussed according to their dominant geomorphic theme: • astroblemes (impact structures); • sand deserts (derived from aeolian sediment transport) (sub-themes: basins; ridge-valley); • karst (created by the dissolution of soluble rocks); • arid coasts; • tectonic landforms (sub-themes: flexure; faulting; diapirism); • uplands; • regolith (sub-themes: vertisol plains and slopes; saprolite; silcrete and gibber plains; other duricrusts); • watercourses (sub-themes: sand-bed rivers; discontinuous ephemeral streams; anabranching rivers; mud-aggregate floodplains; freshwater basins; mound springs; banded vegetation sheetflow plains; floodouts; palaeodrainages; megaflood landforms; playa lakes and megalakes; post-European drainage incision). Twenty eight sites or indicative areas were identified which have either met the NHL criteria thresholds, or have been judged in this study to have potential to do so (Table 1, Fig. 1). Site clusters occur in the Amadeus Basin and the Lake Eyre Basin. Site or area NHL value is variously assessed as clear, likely, or probable (pending further investigation). The identification of these places does not, in itself, constitute a nomination, it is a recommendation that they be considered. The study area is generally under-researched, and particular knowledge gaps are identified in the Davenport-Murchison Ranges and the Great Sandy and Great Victoria Desert dunefields. Aridity, which is widely regarded as a defining characteristic of the Australian inland, is only the latest imprint of a long series of processes. It is now the most important condition modifying the landscape, but is not the reason that this landscape exists. The key drivers which have created the unique Australian desert landscapes are the length of time that the stable landscape has existed, the previous climates which have operated on that landscape, the development of aridity in geologically modern times, and the high degree to which these landscapes display features inherited from the past. These drivers are the context within which operate the agents that work upon the landscape: water, wind, gravity, plate tectonics, chemical reactions, and living things.