[1] The Icelandic mantle plume generated maximum uplift in early Paleogene times. The Faroe-Shetland basin, which fringes the North Atlantic margin of Europe, was close to the center of early Paleogene Icelandic plume activity. Three-dimensional seismic reflection data from the Faroe-Shetland basin reveal sedimentary geometries that allow a phase of transient uplift to be accurately reconstructed and quantified. Close to the Paleocene/Eocene boundary (circa 56 Ma), rapid uplift resulted in fluvial incision into marine sediments. This unconformity was buried by nonmarine sediments, recording the decay of transient uplift. Relief on the unconformity was $550 m, constraining the minimum amount of surface uplift. Some 60 m of this uplift can be attributed to the isostatic response to erosional unloading. Tectonic uplift of over 490 m peaked and decayed within 3 Ma. Rates of waterloaded tectonic subsidence following peak uplift are several times greater than maximum expected postrift subsidence rates. The amplitude and duration of this transient effect is best explained by a mantle convective phenomenon. We suggest that a region of hot plume material flowed laterally beneath the lithosphere, producing transient uplift which decayed when plume material was advected farther away. Our analysis suggests that under certain circumstances, stratigraphic records can yield valuable quantitative information about aspects of mantle convective circulation.

No abstract

SUMMARY Magmatic underplating at the base of the continental crust is thought to be an important consequence of mantle plume activity. Geochemical evidence supports the hypothesis of underplating beneath the British Tertiary Igneous Province during Palaeocene times, a process that has been invoked to explain at least part of the observed pattern of Cenozoic denudation and consequent offshore deposition. This study uses receiver functions to independently test the results of modelling of four wide‐angle seismic lines across the British Isles, several of which indicate the presence of a lens of high‐velocity material at the base of the crust. This lens has been interpreted as evidence of Palaeogene magmatic underplating. Receiver functions were calculated for three permanent and two temporary three‐component broad‐band seismometers. In order to detect P‐to‐S conversions from intracrustal velocity discontinuities, high frequencies were preserved in the calculation of the receiver functions. Receiver functions were modelled using the delay times of the P‐to‐S converted arrivals only, with constraints on the VP and VP/VS structure imposed from controlled source data. This pragmatic method of interpreting receiver function data agrees well with the results of applying an established inversion technique. Resulting crustal velocity models are broadly consistent with the velocity models from the wide‐angle lines, showing evidence for a four‐layer crust with laterally varying Moho depths of between 33 ± 2.5 km beneath southwest Ireland, 32 ± 2.5 km beneath northern and eastern Ireland, 31 ± 2 km beneath the Isle of Man and 35 ± 3 km beneath northern England. While these velocity models are consistent with the presence of a lower crustal layer, receiver functions are insensitive to the P‐wave velocity structure, and so unfortunately they cannot be used to independently constrain the P‐wave velocity of the lower crust, which is an important diagnostic of the presence of magmatic underplating.