Quaternary domains : glacial drowned valley estuaries

This report provides a new interpretation of ‘Glacial Drowned Valley Estuaries’ as part of an ongoing upgrade of the BGS Quaternary Domains dataset. Glacial Drowned Valley Estuaries are major buried features found across the coastal area of GB. These features represent a fluvial landscape that has been dissected and deepened by multiple glaciations to form valleys that are in-part situated beneath modern sea-level. These buried glacial valleys have been and continue to be infilled with marine and estuarine sediment and are overlain by complex or fjord-type estuaries. They typically contain significant thicknesses of superficial sediment of up to 160 m and are often associated with major cities, ports, or industrial centres. Consequently, these features have important groundwater and engineering implications. This work uses a range of national-scale data sets to identify and map Glacial Drowned Valley Estuaries across GB. The identified Glacial Drowned Valley Estuaries are all in Scotland and occur north of the maximum known extent of Late Devensian glacial ice. The infill sequence predominantly comprises clay and silt with variable proportions of sand, gravel, and peat. The sediments are interpreted as glacial till, post-glacial marine and Holocene-aged estuarine sediments. The mapped extent of post-glacial marine sediment and key isostatically uplifted shorelines are used to define the boundary of the Glacial Drowned Valley Estuaries.