Stability or change: a review of ideas on ancient drainage in Eastern New South Wales

Abstract

Summary Reconstruction of ancient drainage requires the determination of (i) ancient flow direction(s) and (ii) the age(s) when such palaeoflow directions were operative. One approach to these problems is ‘geological’ and generally uses lavas which have flowed down ancient river valleys to reconstruct former drainage. A second, ‘morphological’ approach is based on W. M. Davis's Cycle of Erosion and uses the morphology of river valleys to determine both the age and former flow directions of rivers. When applied to eastern N.S.W., the geological approach is usually conservative, concluding that ancient drainage generally parallels the modern, while the morphological concludes that there has been, major disruption to the river systems of eastern N.S.W. in the relatively recent past, with concomitant westward migration of the Divide.