On the edge of the Brecon Beacons, Upper Gilwern Hill is a site long known for its well-preserved and complete trilobites. The hill is made up of rocks from the Lower and Middle Ordovician, and the privately owned quarry is accessible to parties staying at the onsite Shepherd’s Hut self catering accommodation. The trilobite fossils here are plentiful and the chances of ﬁnding a good number is very high.
♦ To Access into Upper Gilwern quarry is through a very isolated and rural terrain. From Builth Wells, head north or, from Llandrindod Wells, head south, in each case to Howey. Turn east, where it is signposted ‘Hundred House’.
♦ After a one and a half to two and a half kilometres, there is an exceptionally steep hill and, at the top, is a cattle grid. You are then out onto open moorland.
♦ Take the second turning on your left (where there is a small signpost for Upper Gilwern). This is a single track road. Drive past a small cottage set away from the road and keep straight ahead. By now you will see the quarry on the hillside in front of you. Go through a gate and turn into the quarry or park next to the gate.
♦ Ref: 52.214417, -3.3313867
FIND FREQUENCY: ♦♦♦♦♦ – This private quarry is not only extremely productive for trilobites, but they are in remarkable preservation, often complete and are stable.
CHILDREN: ♦♦♦ – All ages welcome, must be supervised at all times by an adult.
ACCESS: ♦♦♦ – Upper Gilwern Quarry is on private land and is only permitted to those staying in the self catering hut. Bring hats, sun lotion and plenty of water, as this is an exposed site with no shade. Car parking is easy once the site has been found.
Many fossils can be found on the scree surface, but the use of a geological hammer and a bolster chisel to split the shale along the bedding plane will reveal many and often complete specimens. Safety goggles are essential. The sheer number of trilobite fossils indicates a rapid burial and death, probably from hot, burning ash raining down from sub-aerial volcanoes, followed by poisoning from noxious fumes.
The fauna here is dominated by the large asaphid trilobite, Ogyginus cordensis. Other common trilobites are the trinucleids, Bettonolithus chamberlaini and Trinucleus abruptus, as well as the rarer, Anebolithus simplicior. Other fossils include orthocones, sponges, brachiopods and graptolites.
Palaeontologist, Pete Lawrance, has been studying this unique location for over 30 years and interprets the site as a near-shore, shallow water environment, used annually as a breeding and nursery colony by the trilobite, Oxyginus. The rocks of the hill are Lower and Middle Ordovician age and the site has rocks from the Llanvirn Series of between 46.9 to 467myrs in age. The beds found at this quarry are:
• 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 best equipment for this site is a geological hammer and bolster or splitting chisels, together with safety goggles.
The faces of the quarry are fairly well sloped, making collecting safe, and the quarry is regularly maintained for collectors. However, as with all locations, care should be taken. Wear suitable footwear and ensure you always wear safety goggles when splitting rocks.
Only to those staying onsite at the brand new Upper Gilwern Quarry Hut, situated in a plot adjacent to the quarry, and is available for up to 4 people in two double beds. It has full electricity, under floor heating, a well equipped kitchenette, Freeview TV, bathroom with shower and lots of outside seating to enjoy the amazing peace and views. The cost of the Hut is £100 per night, with a minimum of two nights stay. This includes your guaranteed access and fee to the quarry on both days (normally £100 per couple). Contact firstname.lastname@example.org for booking and information, or goto www.uppergilwernquarryhut.co.uk