THE LOST CITY OF NORTH-WEST QUEENSLAND - A TEST OF THE MODEL OF GIANTGRIKELAND DEVELOPMENT IN SEMIARID KARST

Jennings and Sweeting's (1963) model of landscape evolution in the Lim estone Ranges of Western Australia has been proposed as a general sche me of semi-arid karstification by Williams (1978) and Ford and William s (1989). The model involves an initial plateau surface which undergoe s progressive karstic dissection. The resultant landscape is character ised first by giant grikelands, then by box valleys and finally by kar st towers. The depth of dissection is governed by the altitude of succ essive 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 dippin g sequence of carbonates and cherts. By contrast with the type example , the depth of dissection, the altitude of successive surfaces, the fo rm and even the location of the grikeland are all controlled by rock s tructure. Not only does this cast doubt on the general applicability o f Jennings and Sweeting's model, it suggests that such landscapes may also be the result of structural control and that the role played by s emi-arid climates may be less important than has previously been propo sed. Given our present poverty of knowledge of semi-arid karstificatio n, any attempt to identify type examples of semi-arid karst may be pre mature.