Linking Paleogene denudation and magmatic underplating beneath the British Isles

Abstract

A simple flexural model is used to explore the relationship between magmatic underplating and denudation. First, we show how denudation can be calculated as a function of underplating. The distribution and density of underplate are obviously important parameters in determining the wavelength and amplitude of denudation. However, the denudational pattern can be considerably modulated by the flexural rigidity of the lithosphere. Several other parameters also play a significant role. For example, we show how variations in pre-existing bathymetry and in present-day topography affect denudational calculations. We have applied our simple algorithm to the problem of Paleogene underplating beneath the British Isles. Forward and inverse modelling of travel-time data from a wide-angle seismic experiment which traversed the British Isles suggests that a large pod of high velocity material occurs at Moho depths beneath the Irish Sea. The shape and inferred density of this pod are used to calculate the amplitude and wavelength of denudation for different flexural rigidities. We compare our predictions with the observed pattern of Paleogene denudation and conclude that the bulk of the observed denudation can be accounted for by magmatic underplating associated in a general way with the Iceland Plume. Notwithstanding this agreement, there is compelling evidence for additional mild uplift events especially during the Neogene. These mild events may reflect fluctuating dynamic topography associated with the Iceland Plume.