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Earth Science Conservation Review
| Belshaw’s Quarry – Clay-with-Flints |
| Site number: | 1301 | ||
| Locality Type: | Status: | ASSI | |
| Grid Reference: | J22856705 | ||
| Google maps: | 54.5369,-6.10279 | ||
| County: | Council area: | Lisburn & Castlereagh City Council | |
| Period: | Cretaceous, Tertiary | ||
| Site Description | |
|---|---|
| Introduction: | |
Chalk extraction ceased in about 1950 and in recent years the quarry was designated as a Nature Reserve by the Northern Ireland Environment Agency of the Department of the Environment (NI), whereby it is managed and the main features of the wildlife, habitat and geology are protected and conserved. While the main face of the quarry is clean and well exposed, albeit largely inaccessible, the thin strip of the face representing the Clay-with-Flints horizon is almost completely covered by vegetation and therefore difficult to see and to access (Photograph 5). This situation could be rectified at the western end of the quarry where the Clay-with- Flints is already partly exposed and safely accessible, just beside the top section of the wooden steps that lead to the bottom of the quarry. Periodic judicious clearing of the thin layer of soil and vegetation covering the Clay-with-Flints horizon there would present unequivocal evidence of its presence, composition and its stratigraphical position in the quarry (Photograph 6). | |
| Description: | |
Site Geology: Ulster White Limestone Formation: According to Manning, Robbie and Wilson (1970), the Late Cretaceous Ulster White Limestone Formation hereabouts is just over 10m thick. Fletcher (1977) redefined the lithostratigraphy of the chalk in the quarry and recognised the Portrush Chalk and Ballymagarry Chalk members of the Ulster White Limestone Formation. Both members belong to the Post-Larry Bane Chalk and are of Late Campanian age (Figures 2 and 3). The basal beds of the chalk in this area unconformably overlie red-bed sedimentary rocks of the Late Triassic Mercia Mudstone Group. Although the sub-Cretaceous unconformity is not exposed in the quarry it is probably present less than a metre below the basal chalk. Clay-with-Flints: Unconformably overlying the chalk, the best and most accessiblesection in the Clay-with-Flints is found in the western part of the quarry. Antrim Lava Group: The upper part of the quarry comprises sub-horizontalPalaeogene basalt lava flows of the Lower Basalt Formation of the Antrim LavaGroup. At the southwest end of the quarry a 2m thick vertical Palaeogene doleritedyke intrudes the basalt lava flows and continues to the SSE baking the chalk and the Clay-with-Flints. In the immediate vicinity of the dyke, organic material in the Clay-with-Flints has been blackened due to secondary heating in excess of 200oC. Quaternary Deposits: The thickness of glacial till (boulder clay) overlying rock head varies from a few centimetres to 4m around the top of the quarry. The Clay-with-Flints detail: The section in the Clay-with-Flints illustrated below is just over 80cm thick and was measured in the western part of Belshaw’s Quarry (Figure 8). Removal of a thin soil cover revealed the contacts with the overlying basal lava and with the underlying chalk. Within this section of the Clay-with-Flints three subtle divisions are evident, defined largely by the size, density and distribution of the flint nodules. In the lowest 40cm of the bed the clay matrix is a deep bluish grey colour and contains scattered small to medium flints which show no internal staining. In the succeeding 30cm the clay matrix is conspicuously lighter grey in colour and its base is marked by the presence of large whole flints up to 16cm long which have developed a thick white crust and internal purplish pink staining. The top 20cm of the bed, just below the base of the basalt lava flow, becomes darker bluish grey towards the top with small to medium sized flints that are still stained internally but are matrix supported. Palaeontology: Two samples of clay from Belshaw’s Quarry were prepared for palynological examination (Figure 8). Both samples yielded abundant organic residues and palynofloras, with the floras dominated overwhelmingly by dinoflagellate cysts of Late Cretaceous aspect (Figure 5). The palynomorph assemblages, and the associated kerogen comprising comminuted wood and other plant debris, are intensely blackened as a result of the close proximity of this part of the outcrop of the Clay-with-Flints to a Palaeogene dolerite dyke. Miospores in the clay samples from Belshaw’s Quarry are rare and of extremely low diversity. However, in both samples dinoflagellate cysts of Late Cretaceous aspect dominate the palynoflora. Although the assemblages include many long ranging forms a few critical taxa help define the age of the Late Cretaceous chalk from which they were derived by dissolution. Those forms are as follows: Alisocysta circumtabulata Cannosphaeropsis utinensis (Figure 5, Fossil 1) Hystrichodinium pulchrum Neoeurysphaeridium glabrum (Figure 5, Fossil 2) Odontochitina operculata (Figure 5, Fossil 3) Palaeoperidinium pyrophorum (Figure 5, Fossil 4) Palaeotetradinium silicorum Rottnestia wetzelii Wilsonisphaera petila Of the above forms, C. utinensis, P. silicorum, R. wetzelii and W. petila are typical of the latest Santonian to Maastrichtian. N. glabrum is characteristic of the Campanian - Maastrichtian boundary. Importantly, the range top of H. pulchrum, O. operculata and N. glabrum is in the Lower Maastrichtian while the range base of A. circumtabulata is intra-Lower Maastrichtian. Therefore the overlapping ranges of the dinoflagellate cysts A. circumtabulata, N. glabrum and O. operculata are indicative of an Early Maastrichtian age (Belemnitella lanceolata Zone). In Belshaw’s Quarry, the youngest chalk, the Ballymagarry Chalk Member, is latest Campanian in age. The presence of a Lower Maastrichtian palynoflora seems to indicate that chalk of the B. lanceolata Zone, of Early Maastrichtian age, was formerly present in this area but was eroded in later Cretaceous times, prior to the formation of the Clay-with-Flints. Thus the palynofloras are exclusively allochthonous, derived by dissolution of the Ulster White Limestone Formation. Given the relative fragility of the dinoflagellate cysts it is unlikely that they were either reworked or transported immediately after being released from the chalk. However, their presence in clay samples from the lower 0.35 m of the Clay-with-Flints indicates a degree of reworking, mixing and preservation by the volcanic ash derived from the initial volcanic eruption. | |
| Conclusions: | |
In Belshaw’s Quarry, although the Clay-with-Flints is poorly exposed, this could be remedied by cleaning a section that is partially exposed at present at the western end of the site just beside the top of the wooden steps and is only covered by a thin layer of soil. At this section the clay matrix from near the base of the Clay-with-Flints has yielded an assemblage of remarkably preserved Late Cretaceous dinoflagellate cysts. That the remains of the cysts are black in colour is highly unusual but merely reflects the effects on organic material of heat emanating from a nearby Palaeogene dolerite dyke. | |
| Notes: | |
The full series of Clay-with-Flints records is as follows: Record no. 1300 Introduction to Clay-with-Flints of Northern Ireland Record no. 1301 Belshaw’s Quarry – Clay-with-Flints Record no. 1302 Gibson’s Quarry, Portadown – Clay-with-Flints Record no. 1303 Devlin’ Quarry, Moneymore – Clay-with-Flints Record no. 1304 Glenshane Pass – Clay-with-Flints Record no. 1305 Donald’s Hill – Clay-with-Flints Record no. 1306 Tircrevan Burn – Clay-with-Flints Record no. 1307 Ballycastle – Clay-with-Flints Record no. 1308 Demesne Quarry, Glenarm – Clay-with-Flints Record no. 1309 Magheramorne Quarry, Larne – Clay-with-Flints Record no. 1310 Bellevue, Belfast, Co Antrim – Clay-with-Flints Record no. 1311 Soldierstown Quarry, Moira – Clay-with-Flints | |
| Keywords | |
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| Rocks: | Chalk, Clay, Flint, Basalt |
| Access | |
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| Approach: | Publically accessible. Disused quarry (Photograph 4) and Nature Reserve, Knocknadona Townland [Grid Ref: J2285 6705], 4.75km NW of Lisburn City centre, Co. Down (Figures 6 and 7). |
| Record type: | ESCR report | ||
| Entered by: | I J Enlander | ||
| Last updated: | 28 Mar 2019 | ||
| Enlander, I., Dempster, M. & Doughty, P., 2026. Belshaw’s Quarry – Clay-with-Flints, County , site details. [In] Earth Science Conservation Review. https://www.habitas.org.uk/escr/site.php?item=1301. Accessed on 2026-11-05. |
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