Ancient valleys buried beneath the UK

Kearsey, Timothy; Lee, Jonathan; Finlayson, Andrew; Gow, Hannah. 2019 Ancient valleys buried beneath the UK. [Poster] In: The Hydrogeology of the Superficial Deposits, Burlington House, London, 01 - 02 May 2019. (Unpublished)

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Official URL: https://www.hydrogroup.org.uk/hydrogeology-of-the-...

Abstract/Summary

Buried palaeo‐valleys have significant and often unexpected implications for groundwater, geothermal resources and can provide detailed archives of palaeoenvironmental and landscape change. The BGS has embarked on a program of work as part of the Quaternary Heterogeneities Project to study the applied and palaeoenvironmental significance of these features. In the Midland Valley of Scotland, numerous palaeo‐valleys have been identified historically although their age and genesis was poorly understood. This study utilized a digital data set of over 100,000 borehole records that penetrate the full thickness of Quaternary deposits. In total, the study identified 18 buried palaeo‐valleys, which range between 4-36 km length and 24-162 m depth. Geometric analysis using the borehole dataset has revealed four distinct valley morphologies, which were formed by a combination of subglacial and subaerial processes. In the Midland Valley, some palaeo‐valleys cross‐cut each other with the deepest features aligning east–west. These east–west features align with the reconstructed ice‐flow direction under maximum ice sheet conditions. The shallower features appear more aligned to ice‐flow direction during ice‐sheet retreat, and were therefore probably incised under more restricted ice‐sheet configurations. The infills of these palaeovalleys are equally variable ranging from less than 10% to over 50% sand and gravel and appear largely unrelated to the processes that formed them. Instead, infilling occurred predominantly during deglaciation in response to fluvial capture and/or sea-level change (drowning). Further work is being undertaken to characterise their geometry and infill and to identify and characterise other features elsewhere in the UK.