Crûg Farm Quarry

Overview

A small disused limestone quarry north of Llandeilo, notified as a Site of Special Scientific Interest in 1980 and covering half a hectare. The Crûg Limestone exposed in it is the only conodont-rich horizon of its age in Britain, and the quarry is the type locality for a number of trilobite species — a site geologists have known for nearly 150 years and are still getting new data out of.

History

Nothing read for this record establishes when the quarry was opened, by whom, or for what — presumably lime or building stone, as with most small limestone workings in the Tywi valley. It was disused by the time the site was notified as a Site of Special Scientific Interest in 1980, with the notification confirmed in 1983. Its documented life is scientific rather than industrial, and long: the citation notes that Crûg Quarry has been known to geologists for nearly 150 years, which takes the record back to the middle of the 19th century, when the Ordovician rocks of this part of Wales were being described for the first time and the Llandeilo Series took its name from the town a mile or two to the south.

Geology

The quarry exposes the Crûg Limestone, a richly fossiliferous shelly limestone of Upper Ordovician age — the most recent estimate placing it in the Cautleyan, Zones 1 and 2. It carries abundant trilobites, brachiopods, conodonts and echinoderm fragments, and it is a key Upper Ordovician stratigraphic site for two reasons. It is the only conodont-rich horizon at this level anywhere in Britain: over thirty forms of conodont have been described from Crûg Farm, and the assemblage has been compared with strata of similar age in Central America — a reminder that Ordovician Wales sat far from where it does now. And it is the type locality of a number of trilobite species, making it a reference site rather than merely a good exposure.

Geological setting: Sedimentary Beds and Seams (surviving physical example)

Workings

A small quarry of half a hectare. Nothing read for this record describes the face, the depth or any plant, and the site's designation is for the section it exposes rather than for anything the quarrying left.

Closure

No closure date has been established. The quarry was disused when the site was notified in 1980 and nothing consulted here narrows it further.

What remains

A designated Site of Special Scientific Interest of 0.5 hectares, valued for the section and the fauna it exposes. The citation records that recent research was still producing new data from it — the conodont assemblage in particular — nearly a century and a half after geologists first took an interest.

The quarry face itself, which is the reason for the designation. Nothing read for this record describes a surviving quarry structure.

Related mines

• Smarts Quarry — Two Carmarthenshire quarries protected for what their faces expose rather than for anything they produced, and for opposite kinds of evidence: Crûg Farm for the body fossils in its Ordovician limestone, Smarts for the traces an animal left behind in Namurian sand.
• Talar Wen Quarry — Two small Carmarthenshire quarries notified as Sites of Special Scientific Interest for the Ordovician sections and faunas they expose rather than for anything they produced, both of them trilobite localities — Crûg Farm in the Upper Ordovician, Talar Wen in the Llandeilo.

Nearby mines

• Talar Wen Quarry — 8.1 km NE
• Birdshill Quarry — 9.3 km N
• Betws Colliery — 10.0 km S
• Wernos Colliery — 10.6 km S
• Garnant Colliery — 11.7 km SE

Straight-line distance, within 15 km. Show on the map.

Recorded claims

Individual factual claims, each attached to the source(s) that support it below. Where sources disagree, both are kept.

• Crûg Farm Quarry was notified as a Site of Special Scientific Interest in 1980, with a further notification in 1983, at national grid reference SN 627231, covering 0.5 ha. ¹
• The Crûg Limestone is the only conodont-rich horizon at this level in Britain, the most recent age estimate placing it in the Cautleyan Zones 1/2; it has yielded important trilobite material and is the type locality of a number of species, making it a key Upper Ordovician stratigraphic site. ¹
• Over thirty forms of conodont have been described from Crûg Farm, and comparisons of the sequence have been made with strata of a similar age from various locations in Central America. ¹
• Crûg Quarry has been known to geologists for nearly 150 years, and recent research is proving that the site still has a great deal of new data to offer. ^1,2

Photographs & further reading

Sources

1. (primary) Crûg Farm Quarry SSSI citation, Carmarthenshire — Countryside Council for Wales / Natural Resources Wales
2. (secondary) Crûg Farm Quarry — Wikipedia

Record created: 4 September 2026 · Last researched: 6 September 2026