FOSSILS IRELAND: FOSSIL SITES IN IRELAND - Section 3-3 - County Clare - mid-west

Contents - Fossils sites in Ireland

Chapter 1 - Introduction
Section 1-1 - Fossil collecting in Ireland
Section 1-2 - Where are the dinosaurs?
Section 1-3 - The good news

Chapter 2 - Fossils from different ages
Section 2-1 - Precambrian/Cambrian
Section 2-2 - Ordovician
Section 2-3 - Silurian
Section 2-4 - Devonian
Section 2-5 - Carboniferous/Mississippian
Section 2-6 - Carboniferous/Pennsylvanian

Chapter 3 - Fossil sites in Ireland
Section 3-1 - County Wexford - Hook Head - Mississippian
Section 3-2 - County Clare - Burren - Mississippian
Section 3-3 - County Clare - mid-west - Pennsylvanian
Section 3-4 - County Sligo - Streedagh Point - Mississippian

Resources

Chapter 3 - Fossil sites in Ireland

by Jutta Kruse, version April 2025

This chapter gives examples of fossil specimens from several sites in Ireland. Each location is covered in a separate section. Full citations at Resources.

The locations are relatively easy to find, accessible and open to the public.

Visits to all locations are taken at your own risk. Coastal rocks can be very slippery at times, especially when wet. Winds, tides and large waves add risk factors. Please inform yourself on local conditions and always be safe.

Please leave fossils in Ireland where you find them. Search, find, identify, photograph and post them online, but do not specify the exact location where they were found to protect them from damage.

If you spot any errors or omissions, please let me know, Jutta at info@fossils.ie

Images ⓒ Jutta Kruse unless otherwise noted.

Section 3-3 - County Clare - mid-west - Pennsylvanian

Fig. 3-3.1 - Location of the mid-west county Clare region.

The Burren, with its Mississippian limestone, is located, as described in Section 3-2, in northern county Clare. Pennsylvanian rocks, many originating in the Namurian North-West European regional stage, are exposed from south of the Doolin area and are spectacularly exposed at the Cliffs of Moher (Best & Wignall, 2016, Chapter 10), (Parkes et al., 2005), also see [Fig. 3-3.1.1].

Fig. 3-3.1.1 - The white White arrows indicate the Namurian (German: Namurium) in the chronostratigraphic division of the Carboniferous in Europe (table adapted from: Menning & Hendrich, STDK, 2022. Used with permission of the DSK).

Fig. 3-3.2 - Cliffs of Moher, looking north from Hag's Head. The rocks here belong partly to the Namurian cyclothems.

The Cliffs of Moher, as well as the rocks in county Clare extending south from here to the Loop Head lighthouse, were formed from the early Pennsylvanian onwards as the sedimentary fill of a tropical basin near the equator [Fig. 3-3.3] and lie unconformably on the Mississippian limestones (McNamara, 2009), (Holland & Sanders, 2009, Chapter 11) (Meere et al., 2020, pp 154-180) (Best & Wignall, 2016, pp 1-47).

This basin is sometimes called the 'Shannon Basin' or the 'Clare Basin', also the 'West Clare Namurian Basin' or the 'Western Irish Namurian Basin'. 'Shannon Basin' is used here.

Fig. 3-3.3 - Palaeogeographic setting of the Namurian geology of the Shannon Basin.

The fossils from this area originate in a series of Namurian (particularly Bashkirian) sequences, also called cyclothems, that represent a section of the sedimentary infill of the Shannon Basin.

This group of five cyclothems is called the 'Central Clare Group'. It is found in outcrops along the coast between and including the Cliffs of Moher and the Loop Head peninsula. Some locations of interest are Killard Point, Seafield beach, Spanish Point and Liscannor Bay. The rocks are mostly sandstone, mudstone and siltstone.

Fig. 3-3.4 - The bedrock at Spanish Point, county Clare, originates in the Central Clare Group of cyclothems.

The ancient habitats were constantly changing and therefore fossils from different biotopes are found here. The dynamic conditions in the Shannon Basin at that time have been compared to those of the present-day Mississippi delta (Rider, 1969).

Trace fossils reflect these ancient environments (overview of trace fossils: (Rygel & Quinton, 2024, Chapter 9.6). Marine environments can be traced by the presence of trace fossils such as Skolithos, Arenicolites, Taenidium, Lockeia, Thalassinoides, Zoophycos, Planolites, Helminthoida and Ophiomorpha.

Plants and animals from terrestrial environments, alternating between subaerial and submerged by fresh water from rivers or lakes, left traces like Diplichnites (trackways), diverse burrows and traces of plant roots.

Terrestrial plant fossils were deposited in deltaic, fluvial environments in silty and sandy sediments, for example Lepidodendron, Stigmaria, Calamites, Psaronius and Sigillaria.

Numerous ammonoids (e.g. the goniatite Bilinguites), brachiopods and bivalves (e.g. Dunbarella, Posidonia) are found in the fully-marine bands which separate the cyclothems.

Chronological comparisons over large areas can be made using ammonoid faunas. It has been discovered that contemporaneous Namurian sediments are found in many European regions, for example in the German Ruhr area, as well as in northern England, southern Portugal, Belgium and Poland (Korn, 2007).

The fossils from the mid-west county Clare area are here divided into three sections: plant fossils, trace fossils and ammonoids - goniatites - nautiloids - bivalves - gastropods.

Section 3-3.1 - Plant fossils - mid-west county Clare

Calamites

Fig. 3-3.5 - Reconstruction of Calamites. Image credit: Par Falconaumanni — Travail personnel, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=56797814.

Calamites are the fossil remains from an extinct genus of large, arborescent (tree-like) horsetails (Sphenopsids). They are related to our much smaller, modern horsetails (Equisetum).

Fig. 3-3.6 - Calamites stem from the Namurian of mid-west county Clare.

Fig. 3-3.7 - Calamites from the Namurian of mid-west county Clare.

Fig. 3-3.8.1 - Calamites fragment in a beach pebble from the Namurian of mid-west county Clare.

Lycopods

Fossils from diverse kinds of arborescent (tree-like) club mosses (lycopods) are preserved as a wide variety of plant fossils, for example Lepidodendron, Lepidophloios and Sigillaria.

Fig. 3-3.8.2 - Reconstruction of some lycopods. From left: juvenile Lepidodendron, mature Lepidodendron, Lepidophloios, Synchysidendron, Diaphorodendron, Sigillaria. Image credit: Falconaumanni - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=46906747.

Stigmaria is the name given to fossil parts of the root systems of club mosses.

Fig. 3-3.8.3 - Reconstruction of a stigmarian root system. Image credit: adapted from (Hetherington et al., 2016, Fig. 4).

Fig. 3-3.9 - Stigmaria from the Namurian of mid-west county Clare.

Fig. 3-3.10 - Detailed view of Stigmaria rootlet scars from the Namurian of mid-west county Clare. Scars are about 3mm in diameter.

Fig. 3-3.11 - Stigmaria from the Namurian of mid-west county Clare. Scars are about 3mm in diameter.

Fig. 3-3.12 - Stigmaria from the Namurian of mid-west county Clare.

Fig. 3-3.13 - Plant remains from the Namurian of mid-west county Clare.

Fig. 3-3.14 - Periderm from the Namurian of mid-west county Clare.

Fig. 3-3.15 - Inner bark of a lycopod (Knorria imbricata) from the Namurian of mid-west county Clare.

Fig. 3-3.16 - Periderm from the Namurian of mid-west county Clare.

Fig. 3-3.17 - Periderm from the Namurian of mid-west county Clare. For scale 1-Euro coin.

Fig. 3-3.18 - Lepidodendron from the Namurian of mid-west county Clare. For scale 2-Euro coin.

Fig. 3-3.19 - Sigillaria from the Namurian of mid-west county Clare.

Fig. 3-3.20 - Artisia (pith casts of cordaitalean stems) from the Namurian of mid-west county Clare.

Fig. 3-3.21 - Lepidodendron or Psaronius? from the Namurian of mid-west county Clare.

Fig. 3-3.22 - Lepidodendron from the Namurian of mid-west county Clare.

Fig. 3-3.23 - Periderm with branch scars from the Namurian of mid-west county Clare.

Fig. 3-3.24 - Large lycopod ? trunk from the Namurian of mid-west county Clare.

Ferns

Fern fossils are not common in mid-west county Clare and I have never found them in situ. One quite well-preserved specimen came from a field wall that had collapsed onto a beach.

Fig. 3-3.25 - Fern (Mariopteris?) frond from the Namurian of mid-west county Clare.

Section 3-3.2 - Trace Fossils - mid-west county Clare

Fig. 3-3.25 - Trace fossil Psammichnites plummeri (formerly Olivellites) from the Namurian of mid-west county Clare.

Slabs of sandstones bearing the trace fossil Psammichnites plummeri (formerly Olivellites) are often called 'Liscannor Flags' after the small port in county Clare from which they were once shipped all over the world.

They were traditionally used for roofing and flooring in houses, especially near the quarries around the Cliffs of Moher. Today they are still used for indoor flooring, outdoor public paths and field walls. The marks are typically between 1 and 2cm wide. For a discussion of the naming of these trace fossils, see (Mángano et al., 2002).

Fig. 3-3.26 - Liscannor flag roofs near the Cliffs of Moher, mid-west county Clare.

Fig. 3-3.27 - Trace fossil Thalassinoides from the Namurian of mid-west county Clare.

Fig. 3-3.28 - Trace fossil Helminthoides from the Namurian of mid-west county Clare. For scale 1-Euro coin.

Fig. 3-3.29 - Trace fossil Zoophycos from the Namurian of mid-west county Clare.

Fig. 3-3.30 - Trace fossils in a sideritic concretion from the Namurian of mid-west county Clare.

Fig. 3-3.31 - Trace fossil Lockeia from the Namurian of mid-west county Clare. The oval resting traces of bivalves are each about 2cm long.

Fig. 3-3.32 - Trace fossil Lockeia from the Namurian of mid-west county Clare. For scale the tip of a boot size UK 6.

Fig. 3-3.33.1 - Trace fossil Ophiomorpha nodosa from the Namurian of mid-west county Clare. The front part of the burrow, which is lined with oval fecal pellets from the trace producer (probably a crustacean such as a shrimp), has broken away, exposing the pyritized burrow infill. Diameter of burrow c. 15mm.

Fig. 3-3.33.2 - Trace fossil Asterosoma from the Namurian of county Clare. Fossil diameter c. 5cm.

Section 3-3.3 - Ammonoids - goniatites - nautiloids - bivalves - gastropods

Fig. 3-3.34 - Goniatite Bilinguites bilinguis and bivalve Dunbarella from the Namurian of mid-west county Clare.

Fig. 3-3.35 - Goniatite from the Namurian of mid-west county Clare. Diameter c. 2.2cm.

Fig. 3-3.36 - Septarian concretion with orthocone nautiloid and goniatites from the Namurian of mid-west county Clare. Length of the orthocone c. 7cm.

Fig. 3-3.37 - Nautiloid in a concretion from the Namurian of mid-west county Clare. Diameter of the nautiloid c. 8cm.

Fig. 3-3.38 - Septarian concretion with goniatites and an orthocone nautiloid (left) from the Namurian of mid-west county Clare.

Fig. 3-3.39 - Iron-coated septarian concretion with goniatites from the Namurian of mid-west county Clare.

Fig. 3-3.40 - Septarian concretion with goniatites from the Namurian of mid-west county Clare. The light-coloured lines are desiccation cracks which filled with minerals (often calcite) from surrounding water.

Fig. 3-3.41 - Goniatite in a septarian concretion from the Namurian of mid-west county Clare.

Fig. 3-3.42 - Goniatites Bilinguites bilinguis from the Namurian of mid-west county Clare. The white lines are modern salt crystals that form on sunny days at low tide in the cracks of the brittle shale. The barnacles are also recent.