Superficial geology of the Berwick-Spittal area, Northumberland

Revision mapping of superficial deposits and artificial ground has been completed for a 24 km2 area of Northumberland, including the area of Berwick-upon-Tweed south of the River Tweed and the coastal village of Spittal. The map compilation was funded by the Environment Agency in 2026, with fieldwork conducted in 2025 under commission as part of Project Groundwater Northumbria (PGN), a Defra-funded Flood and Coastal Resilience Innovation Programme project led by Gateshead Council.
Prior to this survey, the area was last surveyed in the 1920s. The revised mapping is based on new field observations combined with analysis of high-resolution digital terrain data, borehole records and aerial photographs. The distribution of superficial deposits has been revised, reflecting a stronger link between the form of the topography and extent of glacial till and overlying proglacial deposits. The proglacial deposits include a previously unmapped moraine and several areas of glaciolacustrine deposits.
The moraine comprises an undulating sandy ridge approximately 1.5 km in length, which likely reflects a former ice margin position during the westwards retreat of the Tweed ice stream at the close of the late Devensian glaciation (approx. 18 000 to 14 000 years ago). Glaciolacustrine deposits have been recognised in the depression formed to the west side of this moraine and in hollows within the undulating bedrock and till surface within the remainder of the area. These were likely filled by short-lived lakes soon after deglaciation and exhibit variable types of fill, including laminated silty clay, clayey sand and fine sand.
In the southern two-thirds of the mapped area, the till and associated proglacial deposits are relatively thin (less than 3 m) and patchy, with bedrock exposed at or near surface over approximately 40 per cent of the area. The bedrock is commonly highly weathered.
In the northern third of the area, underlying much of Berwick-upon-Tweed, the till cover is more consistent with thicker deposits (over 3 m) present. The till locally overlies glaciofluvial deposits that show evidence of weak deformation, indicating that a minor glacial re-advance may have occurred during the recession. Along the River Tweed, which forms the northern boundary of the area, a series of river terrace and estuarine deposits are developed. These, along with the coastal deposits underlying Spittal, show evidence of raised deposits at about 4 to 6 m above ordnance datum. This likely reflects deposits formed during a period of higher relative sea level soon after deglaciation.
The revised mapping, including both the distribution of deposits and their lithologies, has implications for the understanding of ground conditions and groundwater systems in the area. Further targeted work to characterise the engineering and hydrogeological properties of the deposits would be valuable. These applied applications would also benefit from improved understanding of the thickness of the deposits, which is relatively poorly known due to a lack of borehole coverage and few observable sections in the field. Use of geophysical surveying approaches may help to provide additional thickness constraint for the area.