Cenozoic uplift of southwest England

Abstract

AbstractThe uplift history of southwest England is inferred using a composite dataset including marine and fluvial terraces and karstic data. The estimated post‐Mid‐Pliocene uplift increases eastward from ∼130 m in west Cornwall and ∼135 m in south Devon to ∼150 m in the Hampshire Basin. The post‐Early‐Pleistocene uplift likewise increases eastward, from ∼55 m in west Cornwall to ∼60 m in south Devon and ∼80 m in Hampshire. Landscape and thermochronological evidence also indicates Eocene uplift, caused by the British Tertiary Igneous Province magmatism; this component tapers eastward from ∼300 m in west Cornwall to ∼50 m in south Devon, with subsidence in east Devon. This uplift accompanied magmatic underplating; the mafic layer added to the basal crust thins eastward from ∼6 km in west Cornwall to ∼2 km in south Devon, evidently tapering to zero farther east. The laterally variable crustal properties caused by this variation in underplating have affected the post‐Mid‐Pliocene uplift; the study region is thus intermediate, in terms of crustal strength and landscape evolution, between central‐southern England, with no underplating, and Ireland, where ∼10 km thick underplating has resulted in extreme Late Cenozoic landscape stability. The Eocene mantle‐plume‐related uplift is distinct from the post‐Mid‐Pliocene phase which, the modelling indicates, has been driven by surface processes and, thus, by climate change. Copyright © 2010 John Wiley & Sons, Ltd.