The lost city of north‐west Queensland: a test of the model of giant Grikeland development in semi‐arid Karst

Jennings and Sweeting's (1963) model of landscape evolution in the Limestone Ranges of Western Australia has been proposed as a general scheme of semi‐arid karstification by Williams (1978) and Ford and Williams (1989). The model involves an initial plateau surface which undergoes progressive karstic dissection. The resultant landscape is characterised first by giant grikelands, then by box valleys and finally by karst towers. The depth of dissection is governed by the altitude of successive levels of pediplanation adjacent to the karst, with each karst level representing the location of a former erosion surface. The Lost City, a giant grikeland in the Barkly karst of north‐west Queensland, has evolved by the karstic dissection and stripping of a gently dipping sequence of carbonates and cherts. By contrast with the type example, the depth of dissection, the altitude of successive surfaces, the form and even the location of the grikeland are all controlled by rock structure. Not only does this cast doubt on the general applicability of Jennings and Sweeting's model, it suggests that such landscapes may also be the result of structural control and that the role played by semi‐arid climates may be less important than has previously been proposed. Given our present poverty of knowledge of semi‐arid karstification, any attempt to identify type examples of semi‐arid karst may be premature.