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Original Article |
1 Department of Earth Sciences, Oxford University, Parks Road, Oxford OX1 3PR, UK
2 BGS Keyworth, Kingsley Dunham Centre, Keyworth, Nottingham NG12 5GG, UK (e-mail: tony{at}earth.ox.ac.uk)
We have used the NEXTMap Britain digital terrain model (DTM) to determine the lithospheric response to erosional unloading and the contribution of tectonics, in the form of elastic plate flexure, to the Cotswold ‘scarp and vale’ landscape. The calculations take into account lithology variations and along-strike changes in escarpment retreat. We show that flexural rock uplift as a result of erosional unloading varies spatially and may contribute up to 50% of the relief in the Cotswold region. This is supported by morphometric analysis, of concavity and steepness, for 66 longitudinal river profiles that drain the scarp and dip slope of the escarpment. Viscoelastic plate models suggest that the uplift is initially rapid (up to 8 m ka–1) and essentially complete within 50 ka. These initial rates are compatible with an early post-Anglian incision rate inferred from the Thames terraces. The ‘staircase’ terrace pattern suggests, however, that there have been a number of denudational isostatic events, each associated with a climate cycle. Finally, the analysis reveals an inherited ‘proto-landscape’ that has a subdued relief when compared with the modern DTM. Such a relief is consistent with an early extension of the River Thames, through the Vale of Moreton, to the north of the present-day Cotswold Hills.
