The Fremington Clays - extent and source.

The Fremington potters clay is a small lacustrine deposit in the Taw estuary near Barnstaple — smooth, stone-free clay worked for centuries. A lot of writing treats the BGS Sheet 293 “boulder clay” / till polygon as if it were that lake bed, and then builds a high Irish Sea ice sheet on top of it. The borehole evidence does not support that.

The point in one line: clay tops show the Ice Age lake did not rise above about 30 m OD. There was an ice/debris dam at the shoreline on that scale, not a 100 m glacier storming ashore.

That matters for Stonehenge arguments that need a mighty wall of ice across Devon to reach Salisbury Plain.

See it on a map

Interactive gazetteer — classified boreholes, historic Combrew and Higher Gorse clay pits, OD cross-sections, 3D clay lens under LiDAR ground:

https://timdaw37.github.io/fremington-clay/

(Source: https://github.com/TimDaw37/fremington-clay)

The logged lacustrine outline is much smaller than the published till footprint. BH9–11 on the Hele–Bickington ridge sit well above the lake band and are head, not potters clay.

The papers

The write-ups below are the April 2026 reports. Copies on ResearchGate and Academia are the original PDFs and have not been updated with this interactive map / 3D work — use this blog and the gazetteer for the current figures.

OD analysis of the 1972 Brannam boreholes (and what that does to Sheet 293): https://www.sarsen.org/2026/04/constraining-fremington.html

Short summary of the same borehole constraint: https://www.sarsen.org/2026/04/new-borehole-analysis-sharply.html

Why most of the mapped “glacial” package is fluvial / periglacial, with only limited ice-marginal influence: https://www.sarsen.org/2026/04/caution-in-attributing-fremington-clay.html

How a composite ice–sediment dam can hold a ~30 m lake without a towering ice cliff: https://www.sarsen.org/2026/04/outwash-fan-heads-composite-dams-and.html

Erratics (mostly local; elevation constraints): https://www.sarsen.org/2025/11/the-fremington-clay-erratics.html

Read the data, not the wishful thinking.