Morphologic analysis of scarp degradation can be used quantitatively to determine relative ages of different scarps formed in cohensionless materials, under the same climatic conditions. Scraps of tectonic origin as well as wavecut or rivercut terraces can be treated as topographic impulses that are attenuated by surface erosional processes. This morphological evolution can be modelled as the convolution of the initial shape with erosion (or degradation) function whose width increases with time. Such modelling applies well to scarps less than 10 m high, formed in unconsolidated fanglomerates. To a good approximation, the degradation function is Gaussian with a variance measuring the degree of rounding of the initial shape. This geometric parameter can be called the degradation coefficient. A synthetic experiment shows that the degradation coefficient can be obtained by least squares fitting of profiles levelled perpendicular to the scarp. Gravitational collapse of the free face is accounted for by assuming initial scarp slopes at the angle of repose of the cohesionless materials (30¿--35¿). Uncertainties in the measured profiles result in an uncertainty in degradation coefficient that can be evaluated graphically.

Because the degradation coefficient is sensitive to the regional slope and to three-dimensional processes (gullying, loess acumulation, stream incision. etc.), a reliable and accurate determination of degradation coefficient requires several long profiles across the same scarp. The linear diffusion model of scarp degradation is a Gaussian model in which the degradation coefficient is proportional to numerical age. In that case, absolute dating requires only determination of the proportionality constant, called the mass diffusivity constant. For Holocene scarps a few meters high, in loose aluvium under arid climatic conditions, mass diffusivity constants generally range between 1 and 6 m2/kyr. Morphologic analysis is a reliable method to compare ages of different scarps in a given area, and it can provide approximate absolute ages of Holocene scarplike landforms. ¿American Geophysical Union 1993