A possible glacially-forced tectonic mechanism for late Neogene surface uplift and subsidence around the North Atlantic

Abstract

Analysis of old erosion surfaces and estimates of exhumation from apatite fission track data can be used to infer late Neogene surface uplift of Britain, Greenland, Norway and Svalbard of 1–2km. Subsidence and sedimentation in adjacent offshore basins can be found from interpretation of seismic and well log data. Various mechanisms for surface uplift have been proposed but the underlying cause remains unexplained. Since the multiple glaciations that took place during the late Neogene were a common factor, a possible glacially-forced tectonic mechanism to thicken the crust and produce surface uplift has been investigated. This could result from the relatively slow accumulation of ice that loads the crust as an ice sheet grows during a glacial period, followed by relatively rapid retreat and unloading around its periphery at the end. Unloading could create transient stresses that induce lateral flow in a ductile lower crust to thicken it onshore and produce surface uplift, with associated thinning beneath adjacent offshore basins, producing subsidence. Simple calculations show that the proposed mechanism is feasible and indicate that crustal thickening and surface uplift accumulated from a number of glacial cycles can account for the observed surface uplift, with an acceptable flow rate in the lower crust at the end of each cycle if the viscosity of ductile flow is sufficiently low.