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Lookup NU author(s): Dr Rob Westaway,
Professor David Manning,
Professor Paul Younger
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The Cenozoic landscape development of Britain remains relatively poorly understood. On the one hand, 'plumists' have tried to explain the present-day topography as a consequence of effects of the Iceland mantle plume during the Palaeocene-Eocene British Tertiary Igneous Province (BTIP) magmatism, with little or no subsequent modification. On the other hand, abundant evidence exists from fluvial and marine terraces and superimposed karstic levels for significant vertical crustal motions during the Quaternary, which clearly has nothing to do with any mantle plume. To shed light on this issue, we present the first publication of data that constrain the Cenozoic thermal history of the North Pennine uplands of northern England, from apatite fission-track analysis of drill cuttings from the Eastgate Borehole in Weardale, in the western part of County Durham. Our results indicate similar to 650 m of regional denudation since the latest Oligocene/Early Miocene, plus the similar to 400 m of localized entrenchment that has created the modern Weardale valley. Before the latest Oligocene/Early Miocene, but following the BTIP magmatism, the crust in this region experienced significant cooling, mainly due to a decrease in the geothermal gradient from similar to 55 to 61 degrees C km(-1) to the present 38 degrees C km(-1), along with similar to 300 +/- 200 m of denudation. Although significant BTIP magmatism occurred in northern England, it thus had only a limited net effect; the crust experienced dramatic heating, but cooled back to its original thermal state within, at most, a few tens of millions of years. We suggest that this rapid cooling effect resulted from westward flow of relatively cold material within the mobile lower-crustal layer, driven by the lateral pressure gradient induced by earlier heating effects and effects of surface processes. Whatever topography developed during the Palaeogene, as a direct result of these heating effects, underplating at the base of the crust, and the associated modest denudation, was presumably also short-lived; significant changes to the crustal thickness, and thus to the topography, can be envisaged as a consequence of subsequent lower-crustal flow. (c) 2011 The Geologists' Association. Published by Elsevier Ltd. All rights reserved.
Author(s): Green PF, Westaway R, Manning DAC, Younger PL
Publication type: Article
Publication status: Published
Journal: Proceedings of the Geologists' Association
Print publication date: 01/06/2012
ISSN (print): 0016-7878
Publisher: Elsevier Ltd
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