The Geomorphological Development of the Cotswold Hills, southern England: A Tectonic Perspective

• Main Author: Lane, Natalie F.
• Published: University of Oxford 2007
• Subjects: 551.4
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.487281

Scarp and Vale' topography is typified by the Cotswolds region with the present-day landscape being the aggregate of earlier tectonic movement and surface processes. The primary aim of this thesis is to disentangle these landscape components, the .feedbacks between them and their driving mechanisms. Modelling suggests that flexure, in response to denudational unloading, may account for ~35% of local Pleistocene relief. Shape-fitting, between the model and landscape observations, shows the local lithosphere to be relatively weak and the uplift to be spatially varying. River longitudinal profiles adjust to extrinsic variables, such as tectonic movement, base level change and climate fluctuation. Parametrisation of 66 Cotswold draining rivers revealed trends, in their concavity and steepness index, consistent with those of the modelled uplift. Similar trends were sought from geomorphic analysis of the fluvial sinuosity and basin hypsometry. There is a morphological control to channel sinuosity as it is found to be dependent upon flow orientation. A positive relationship is observed. between hypsometric integral and proposed uplift, for the dip-slope basins. The accumulated geomorphic evidence does not prove the flexure modelling results, however, they are consistent with it. Viscoelastic modelling calculates the rate of lithospheric relaxation. It predicts high ' initial uplift rates which decrease rapidly and the attainment of topographic equilibrium within ~2o-50 ka of unloading. This is significantly lower than the climate cycle duration of 100 ka. Linking this result with a terrace aggradation and incision model, a schematic model of landscape evolution is produced. This incorporates the regional background uplift, a fluctuating climate, and episodic incision to which there is a flexural feedback. It is concluded that the Pleistocene has experienced a number of 'incision - flexural uplift aggradation' cycles controlled temporally by the fluctuating climate.