『Abstract
　Escarpments are prominent morphological features along high-elevation passive margins. Recent studies integrating geomorphology, thermochronology, and cosmogenic nuclide-based denudation rate estimates suggest a rapid phase of denudation immediately after the earliest stages of seafloor spreading, and subsequent slow denudation rates since. To constrain the geomorphic evolution of passive margins, we have examined the development of the Sri Lankan escarpment. Cosmogenic nuclide data on river sediment along a north-south transect across the southern escarpment reveal that the landscape is eroding ten times more rapidly in the escarpment zone (26 to 71 mm kyr^-1) than in the high-elevation plateau above it and in the lowland plain beneath it (2.6 to 6.2 mm kyr^-1). Unlike these low denudation rate areas, the escarpment denudation is strongly and linearly hill slope-dependent. This shows that denudation and retreat are tightly interlinked within the escarpment, which suggests that the escarpment is evolving by rift-parallel retreat, rather than by escarpment downwearing. Supporting evidence is provided by the morphology of rivers draining the escarpment zone. These have steep bedrock channels which show sharp and prominent knickpoints along their longitudinal profiles. It appears that fluvial processes are driving escarpment retreat, as rivers migrate headwards were they incise into the high-elevation plateau. However, the average catchment-wide denudation rates of the escarpment zone are low compared to the denudation rates that are estimated for constant escarpment retreat since rifting. In common with other escarpments worldwide, causes for this slow down can be tectonic change related to flexural bending of the lithosphere, climate change that would vary the degree of precipitation focused into the escarpment, or the decrease in the contributing catchment area, which would reduce the stream power available for fluvial erosion.

Keywords: Escarpment retreat; Cosmogenic nuclides; Denudation rates; Erosion; Sri Lanka』

1. Introduction
2. Regional setting and sampling strategy
3. Methods
4. Results and discussion
　4.1. Total denudation rates from cosmogenic nuclides
　4.2. Mechanisms and rates of escarpment erosion
　4.3. Implications for long-term geomorphic evolution of the Sri Lankan Highlands
5. Conclusions
Acknowledgements
References

• 『To examine the mechanism of denudation across the Sri Lankan escarpment, we analysed the spatial correlation between the catchment-wide denudation rates and the fluvial erosion potential. As we have no direct measurement of fluvial erosion, we estimated the intensity of fluvial processes by applying the stream power model [38]. An index of fluvial erosion potential based on the stream power per unit area of bed, FEI, is then calculated as follows
  
  FEI = k A^m Sstrⁿ,
  
  where A is the catchment area, Sstr is the local stream gradient and k, m and n are constants. As we are only interested in relative differences in the intensity of fluvial erosion processes across the escarpment zones, we have chosen m, n and k as 0.5, 1 and 1, respectively [38, 39].』
• [38] Finlayson,D.P., Montgomery,D.R. and Hallet,B.(2002): Spatial coincidence of rapid inferred erosion with young metamorphic massifs in the Himalayas. Geology, 30, 219-222.
• [39] Dadson,S.J., Hovius,N., Chen,H.G., Dade,W.B., Hsieh,M.L., Willett,S.D., Hu,J.C., Horng,M.J., Chen,M.C., Stark,C.P., Lague,D. and Lin,J.C.(2003): Links between erosion, runoff variability and seismicity in the Taiwan orogen. Nature, 426, 648-651.