- Plymouth University, School of Geography, Earth & Environmental Sciences, Plymouth, United Kingdom of Great Britain – England, Scotland, Wales (mhart@plymouth.ac.uk)
In 2023, Plymouth City Council created the Plymouth Sound National Marine Park. While this declaration carries no conservation status, it is based on the European recognition of the area as a Special Area of Conservation in 2005 by Natural England. Marine Research Plymouth, in collaboration with Plymouth City Council, is promoting research into the development of Plymouth Sound since the Last Glacial Maximum. In 1988, two boreholes were drilled into the palaeo-channel of the River Tamar in the middle of Plymouth Sound. The buried channel, which had been located during a geophysical survey, recorded a succession of gravels, saltmarsh, inter-tidal mud flats and open marine sands: all of which contain diagnostic microfossil assemblages. A comparable succession has been recorded near Jersey in another series of marine boreholes in the base of which there is a peat that has been carbon dated as 8300 years b.p.
The Plymouth Sound and Jersey data record the Holocene rise in sea-level following the Last Glacial Maximum (LGM) (20,000–18,000 years b.p.) when the British-Irish ice sheet extended as far south as the north coast of Cornwall. At the LGM, sea level was 125–130 m below the present day and the coastline was almost at the edge of the Continental Shelf. The amelioration in climate and the Holocene sea-level rise generated the present sub-environments of Plymouth Sound and the other rias in South-West England. The present glacial/interglacial cycle is, however, only the latest of a series of climate cycles, numbering perhaps 20+ over the last 2 million years.
Before, and after, the LGM – when permafrost was extensive in South-West England – the caves of South Devon hosted both a significant megafauna and hominin remains and the combination of this terrestrial palaeontology and the marine (foraminiferal) record makes the area of great significance in understanding the Late Pleistocene and Holocene.
How to cite: Hart, M. and Smart, C.: Plymouth Sound Boreholes: a record of sea level rise in the Plymouth Sound National Marine Park (South-West England, U.K.) since the Last Glacial Maximum, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2883, https://doi.org/10.5194/egusphere-egu25-2883, 2025.
