Cenozoic cooling and denudation in the North Pennines (northern England, UK) constrained by apatite fission-track analysis of cuttings from the Eastgate Borehole

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 ∼650 m of regional denudation since the latest Oligocene/Early Miocene, plus the ∼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 ∼55 to 61 °C km−1 to the present 38 °C km−1, along with ∼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

A simulation model of consumer spending and housing demand

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Reply to comment by Rob Westaway on 'review of tufa deposition and palaeohydrological conditions in the White Peak, Derbyshire, UK : implications for Quaternary landscape evolution

We thank Westaway (2012) for his interesting discussion of the uplift rates derived from the Alport tufa and its geomorphological setting. In particular, Westaway (2012) questions the validity of the uplift rates that were presented within our original paper (Banks et al., 2012) and we welcome the opportunity to clarify this further. Analysis of his observations highlights the tentative nature of geological approaches to determining uplift rates in areas affected by both glacio-isostatic and tectonic processes. We therefore also welcome the opportunity to comment on the practicalities of determining uplift measurements from karst environments within the wider, long-term, tectonic evolution of the Peak District. To facilitate the discussion regarding the uplift rates determined from the Alport tufa and its geomorphological setting we have revised and updated Table 4 of Banks et al. (2012). Westaway (2012) makes reference to two of the cited incision rates (Table 4; Banks et al., 2012) that correspond with the late Ipswichian (MIS 5e) to present and the end of the Anglian (MIS 12) to present, then compares them with values that span the entire Quaternary. Banks et al. (2012) did not originally present an incision rate for the duration of the Quaternary and the assumptions regarding the elevations used in the calculations (Westaway, 2012) are incorrect. The time-averaged rate of incision for the entire Quaternary (Table 1) corresponds reasonably closely with the ∼0.06–0.07 mm a−1 calculated by Westaway (2012) from differences in the elevations of the tops of the tufas. It also corresponds with the post late-Miocene uplift rates (0.03–0.06 mm a−1) determined for the Peak District by Pound et al. (2012). The significant difference between these rates and the uplift rates (∼0.1–0.15 mm a−1) cited by [Westaway, 2009a] and [Westaway, 2012] warrants further consideration

An analysis of the impact of finite horizons on macroeconomic control

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