Gilwern Quarry, Powys – Saturday 26th July 2018

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On Saturday 28th July, we landed at Gilwern Quarry, Powys, for the annual UKAFH trilobite fest!

Gilwern quarry is privately-owned and is situated on the edge of the Brecon Beacons, in beautiful and isolated terrain. Gilwern is known for its trilobites, which are generally very well preserved, and can be found in abundance. Gilwern Hill is made of Lower to Middle Ordovician volcaniclastic rock, which form part of the Builth Inlier. The site has rocks from the Llanvirn series (approximately 460 million years old) and exhibits the following beds:

  • Upper Didymographus murchisoni Shales.
  • Pale flinty, tuffaceous beds.
  • Main Rhyolitic tuffs, with Lower Didymographus murchisoni Shales.
  • Rhyolitic tuffs and agglomerates.
  • Upper Didymographus bifidus Beds.
  • Lower Didymographus bifidus Beds

The site has been interpreted as a near-shore, shallow water environment used as a breeding ground for the Ogyginus trilobite (pictured above), due to the number and range of ages of Ogyginus found here. However, other trilobite species such as Meadowtownella and Bettonolithus can be found, as well as graptolites.

Trilo wall

Emma, the lovely landowner, greeted us at the shepherd’s hut as we arrived with hot teas and coffees, which was a lovely surprise, and was very welcome after the long journey that many of us had made. First stop of the day was the “trilobite wall” – a stack of fossiliferous rocks lining the shepherd’s hut car park – you know it’ll be a good day when you find your first fossils in the car park!

Once we were suitably refreshed and kitted up, Sam and Aidan gave an introductory session on the quarry and showed the group some example fossils from previous hunts, including various species of trilobites, graptolites, orthocones and conulariids. We then moved up to the main quarry, where the good finds started rolling in!

Lingulella brachiopods:

Bettonolithus trilobites:

The quarry is packed full of loose rock so there was plenty of material for us to chisel and hammer our way through.

Although the weather looked promising on arrival, after several hours it had clouded over and distant rumbles of thunder could be heard. Unfortunately, this then developed into torrential rain and hailstones (in July!), which felt like being stoned to death with frozen peas! A mad dash to the safety of our cars was in order and with it, an unfortunately abrupt end to the hunt!

We would like to thank all for attending – we hope you had a fantastic day! A special thank you goes to Emma for her fabulous hospitality and we look forward to the next hunt!

Access to the quarry and rental of the self-catering shepherd’s hut can be requested via

For further information on Gilwern fossils, please refer to

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