Isostatic compensation of Quaternary vertical crustal motions: coupling between uplift of Britain and subsidence beneath the North Sea

Abstract

New data from offshore and onshore regions confirm the view that the Quaternary uplift of Britain and subsidence beneath the North Sea are coupled, mediated by lower‐crustal flow induced by the lateral pressure gradient caused by climate‐driven surface processes. Most measured onshore uplift rates, in both upland and lowland localities, are only applicable since the Mid‐Pleistocene Revolution; beforehand, generally lower rates prevailed. Earlier (?Oligocene–Pliocene) phases of uplift and subsidence had typically even lower rates; furthermore, the western margin of the North Sea depocentre was ∼200 km farther from the modern coastline of north‐east England. In the earliest Cenozoic, complex isostatic adjustments occurred in response to the magmatism associated with the Iceland mantle plume; the contemporaneous land surface (relative to the present‐day rock column) in northern England was typically ∼1500 m OD. However, this activity died out during the Palaeogene; the main effect of these events on the modern isostatic configuration was via the emplacement of thick mafic underplating, which now constricts the mobile lower‐crustal layer, explaining the Late Cenozoic ultra‐stability of Ireland. The evidence enables interpretations of the present‐day topography of Britain as static, caused by the Iceland mantle plume, or actively developing in response to plate motions or plate boundary forces, to be excluded.

Early Cenozoic Denudation of Central West Britain in Response to Transient and Permanent Uplift Above a Mantle Plume

“…Westaway (, ) and Green et al () have suggested that Neogene exhumation was significant, driven by lower‐crustal flow due to rapid subsidence and deposition in the North Sea. Our study provides little clear evidence for a resolvable regional Late Cenozoic cooling.…”

“…Currently, there is little consensus on (i) the amount, timing, and spatial variability of rock uplift and denudation associated with the arrival of the proto‐Iceland mantle plume (Cogné et al, ; Davis et al, ; Green, , ; Lewis et al, ; Saunders et al, ); (ii) how it is apportioned between permanent and transient uplift (Cogné et al, ; Hartley et al, ; Tiley et al, ; White & Lovell, ); and (iii) the contribution of large scale plate tectonic processes in the Neogene (Hillis et al, ; Holford et al, ; Stoker et al, ) or lower‐crustal flow in response to lithostatic loading and subsidence in the adjacent offshore basins (Green et al, ; Westaway, , ).…”

Examining the geometry, age and genesis of buried Quaternary valley systems in the Midland Valley of Scotland, UK

“…Therefore, the age of the broad topographic expression of central and southern Scotland is likely to be of Late Miocene age, corresponding to a widespread unconformity that extends across much of Britain, the North Sea and Fennoscandia (Clausen & Huuse ; Clausen et al . ; Westaway , ; Lee et al . ).…”

“…Studies into the burial history of the Carboniferous rocks that are currently at the ground surface suggest that they only came close to the surface in the Neogene; prior to this they were buried up to 2.5 km deep (Vincent et al 2010). Therefore, the age of the broad topographic expression of central and southern Scotland is likely to be of Late Miocene age, corresponding to a wide spread unconformity that extends across much of Britain, the North Sea and Fennoscandia (Clausen & Huuse 1999;Westaway 2010Westaway , 2017Lee et al 2017). No pre-Quaternary saporolites or sediments have been found in the Midland Valleyof Scotland (Cameron & Stephenson 1985;M.…”

The Quaternary geology of the North Sea basin

“…The papers by Lamb et al . (), Buckley () and Westaway () tackle a number of issues regarding the Early to Middle Quaternary history of the North Sea (Fig. ).…”