The Iron Age warriors who built Uley Bury's ramparts were working with a material far older than themselves. The hilltop is a spur of the Cotswold escarpment, formed of thick beds of Inferior Oolitic limestone from the Jurassic period, sitting on top of Bridport Sands. Roughly 180 million years ago, this was a warm, shallow sea, and the evidence is literally underfoot.
Part of Uley Bury is designated a Site of Special Scientific Interest, not for its archaeology but for its geology. The key feature is the Cephalopod Bed, a stratum of Lower Jurassic age packed with the fossilised remains of ancient marine creatures. One horizon is particularly notable for its ammonites — the coiled, chambered shells of creatures related to modern nautiluses. The species found here indicate the strata belong to the early striatulum subzone. Below, in the Bridport Sand layers, a thin sandstone band contains specimens of Haugia variabilis, an ammonite species that is extremely rare elsewhere in Britain.
“The species found here indicate the strata belong to the early striatulum subzone.”
The site also supports unimproved limestone grassland, created by centuries of sheep grazing on the thin soils above the bedrock. The Cotswolds hold a nationally significant concentration of this habitat — 52 per cent of all unimproved Jurassic limestone grassland in the country. At Uley Bury, the combination is unusual: Iron Age earthworks, rare fossils, and ancient grassland ecology compressed into a single hilltop. The ramparts that once kept out rival tribes now protect a geological record stretching back to a time when the Cotswolds lay beneath a tropical ocean.
