Sometimes referred to in literature as 'Bwlch y Gaseg' and in very close proximity to the area named as such on OS Map (six-inch to the mile) 1888-1913, the Cynwyd Forest Quarry is a Site of Special Scientific Interest (SSSI) located aside a track within the Cynwyd Forest near

Corwen Corwen is a town and community in the county of Denbighshire in Wales. Historically, Corwen is part of the county of Merionethshire. Corwen stands on the banks of the River Dee beneath the Berwyn mountains. The town is situated west of Llango ...

Denbighshire Denbighshire ( ; cy, Sir Ddinbych; ) is a county in the north-east of Wales. Its borders differ from the historic county of the same name. This part of Wales contains the country's oldest known evidence of habitation – Pontnewydd (Bontnewy ...

North Wales , area_land_km2 = 6,172 , postal_code_type = Postcode , postal_code = LL, CH, SY , image_map1 = Wales North Wales locator map.svg , map_caption1 = Six principal areas of Wales common ...

. It was described by Rushton ''et al.'' (2000) and exposes Late

Ordovician The Ordovician ( ) is a geologic period and System (geology), system, the second of six periods of the Paleozoic Era (geology), Era. The Ordovician spans 41.6 million years from the end of the Cambrian Period million years ago (Mya) to the start ...

micaceous siltstones and mudstones of the

Dolhir Formation The Dolhir Formation is a geologic formation in Wales. It preserves fossils dating back to the Ordovician period. See also * List of fossiliferous stratigraphic units in Wales This is a list of fossiliferous stratigraphic units in Wales. ...

( Ashgill Series, Rawtheyan Stage) which yields a rich shelly (

brachiopod Brachiopods (), phylum Brachiopoda, are a phylum of trochozoan animals that have hard "valves" (shells) on the upper and lower surfaces, unlike the left and right arrangement in bivalve molluscs. Brachiopod valves are hinged at the rear end, w ...

) fauna.

Trilobites Trilobites (; meaning "three lobes") are extinct marine arthropods that form the class Trilobita. Trilobites form one of the earliest-known groups of arthropods. The first appearance of trilobites in the fossil record defines the base of the At ...

are represented by several genera although the fauna is dominated by ''

Gravicalymene ''Gravicalymene'' Shirley, 1936, is a genus of trilobites belonging to the order Phacopida, suborder Calymenina and family Calymenidae. Species included in this genus have previously been allocated to '' Calymene'' Brongniart 1822,'' Flexicalyme ...

arcuata'' Price, 1982.

Bivalves Bivalvia (), in previous centuries referred to as the Lamellibranchiata and Pelecypoda, is a class of marine and freshwater molluscs that have laterally compressed bodies enclosed by a shell consisting of two hinged parts. As a group, bival ...

bryozoa Bryozoa (also known as the Polyzoa, Ectoprocta or commonly as moss animals) are a phylum of simple, aquatic invertebrate animals, nearly all living in sedentary colonies. Typically about long, they have a special feeding structure called a l ...

ns and various

Echinoderm An echinoderm () is any member of the phylum Echinodermata (). The adults are recognisable by their (usually five-point) radial symmetry, and include starfish, brittle stars, sea urchins, sand dollars, and sea cucumbers, as well as the sea ...

ata (

Crinoid Crinoids are marine animals that make up the class Crinoidea. Crinoids that are attached to the sea bottom by a stalk in their adult form are commonly called sea lilies, while the unstalked forms are called feather stars or comatulids, which are ...

s and

Cystoids Cystoidea is a class of extinct crinozoan echinoderms, termed cystoids, that lived attached to the sea floor by stalks. They existed during the Paleozoic Era, in the Middle Ordovician and Silurian Periods, until their extinction in the Devonian ...

) are also present. Examples of most of the fossils listed below are illustrated and briefly described (or remarked upon) in "Fossils of the Upper Ordovician" by Harper and Owen (Eds.).HARPER, D. A. T. and OWEN, A. W. (Eds.) 1996. Fossils of the Upper Ordovician. ''Palaeontological Association Field Guide to Fossils'' Volume: 7, 312 pages, 52 plates with b/w photos; 34 b/w photos and b/w line drawings.

Fossils include

Bryozoa Bryozoa (also known as the Polyzoa, Ectoprocta or commonly as moss animals) are a phylum of simple, aquatic invertebrate animals, nearly all living in sedentary colonies. Typically about long, they have a special feeding structure called a l ...

: * ''Pinnatoporella carinata'' (Etheridge) * ''Phylloporina'' sp. * ''Graptodictya'' sp.

Brachiopod Brachiopods (), phylum Brachiopoda, are a phylum of trochozoan animals that have hard "valves" (shells) on the upper and lower surfaces, unlike the left and right arrangement in bivalve molluscs. Brachiopod valves are hinged at the rear end, w ...

a: * ''Leptaena'' sp.

Cephalopod A cephalopod is any member of the molluscan class Cephalopoda (Greek plural , ; "head-feet") such as a squid, octopus, cuttlefish, or nautilus. These exclusively marine animals are characterized by bilateral body symmetry, a prominent head ...

a: * ''Zitteloceras costatum'' Teichert.

Trilobita Trilobites (; meaning "three lobes") are extinction, extinct marine arthropods that form the class (biology), class Trilobita. Trilobites form one of the earliest-known groups of arthropods. The first appearance of trilobites in the fossil reco ...

: * ''Gravicalymene arcuata'' Price * ''Illaenus (Parillaenus) davisii'' (Salter) * ''Remopleurides cf. nicholsoni'' Reed * ''Pseudospaerexochus cf. conformis'' (Angelin) * ''Pseudospaerexochus octolobatus'' (McCoy) * ''Calyptaulax'' sp. * ''Tretaspis'' sp.

ea: * ''Cupulocorona rugosa'' Donovan and Paul

Cystoidea Cystoidea is a class of extinct crinozoan echinoderms, termed cystoids, that lived attached to the sea floor by stalks. They existed during the Paleozoic Era, in the Middle Ordovician and Silurian Periods, until their extinction in the Devonian ...

* ''Regulaecystis inconstans'' Paul

Gallery

File:Cynwyd Forest Quarry 20-07-2021.jpg, Cynwyd Forest Quarry - photo taken July 20, 2021. File:Cynwyd Forest Quarry 20-July-2021.jpg, Cynwyd Forest Quarry, 20-July-2021.

Fossils include

Gallery

References

See also