Earth Science Conservation Review
| Clarehill Quarry | Down |
| Site Type: | Quarry (disused) |
| Site Status: | ASSI |
| Council area: | Lisburn Borough Council |
| Grid Reference: | J154603 |
| Google maps: | 54.47848,-6.21967 |
| Rocks | |
|---|---|
| Rock Age: | Cretaceous (Campanian, Maastrichtian) |
| Rock Name: | Ballymagarry Chalk Member, Garron Chalk Member, Portrush Chalk Member, Tanderagee Chalk Member, Ulster White Limestone Formation |
| Rock Type: | Flint, Limestone |
| Interest | |
| Fossil Groups: | Belemnite, Sponge |
| Other interest: | paramoudras, Marine sediments |
Summary of site:
This disused quarry is important for two reasons. The first is its historical association with William Buckland, the English clergyman geologist, Reader in Mineralogy and later Geology at Oxford University and subsequently Dean of Westminster. On a geological expedition through Ireland he visited the quarry and saw for the first time cylindrical or tapering flints up to 60 cm long and 35 cm in diameter, often nesting one on top of another. The name he employed to describe them in his paper of 1817 was paramoudra, thought to have been the word given by Irish speaking quarrymen when asked what they were. Quite how accurately he rendered it is not known and there have been two speculative interpretations from similar sounding Irish words meaning “ugly Paddies” and “sea pears”.
The second reason is the limited representation of the Ulster White Limestone Formation here. In the total sequence of the formation there are 14 members but at Clarehill only four are present. These four lie unconformably on top of Triassic rocks. There is a time interval of roughly 130 million years between the Triassic foundations and the first chalk member which is the Garron Chalk. In the quarry it is a bed 90cm thick, mostly chalk with green glauconite grains but with some phosphatized pebbles; it also incorporates broken fragments of the Mercia Mudstone Formation, the Triassic rock immediately below. The Portrush Chalk Member follows, 2.7m thick, with the lower part being much disturbed by contemporary erosion and the activity of sediment-feeding animals. The top of the member is well bedded and contains many fossils as well as flint nodules. The lowest paramoudras mark the base of the Ballymagarry Chalk Member, 13m thick here and with much greater overall flint content than the others. Immediately below its top, marked by a prominent and laterally extensive bedding plane, is an horizon full of the distinctive broken shell fragments of the large marine bivalve mollusc Inoceramus. The final member is the Tanderagee Chalk, 3.4m thick, weathering into slabby beds with plentiful fossils and tabular flints.
The pattern of invasion of what is now north-east Northern Ireland by the Cretaceous sea was very complicated. The rocks in Clarehill Quarry show that this was one of the last areas to be submerged, around 80 million years ago, and the sea was never very deep. The Portrush Chalk, for example, shows clear evidence of emergence and shallow water conditions in its lower part.
The historic interest of the quarry is of national significance and the condensed sequence of Ulster White Limestone members adds further importance. The site clearly meets the criteria for ASSI designation and should be preserved. The obvious threat is from dumping.
The second reason is the limited representation of the Ulster White Limestone Formation here. In the total sequence of the formation there are 14 members but at Clarehill only four are present. These four lie unconformably on top of Triassic rocks. There is a time interval of roughly 130 million years between the Triassic foundations and the first chalk member which is the Garron Chalk. In the quarry it is a bed 90cm thick, mostly chalk with green glauconite grains but with some phosphatized pebbles; it also incorporates broken fragments of the Mercia Mudstone Formation, the Triassic rock immediately below. The Portrush Chalk Member follows, 2.7m thick, with the lower part being much disturbed by contemporary erosion and the activity of sediment-feeding animals. The top of the member is well bedded and contains many fossils as well as flint nodules. The lowest paramoudras mark the base of the Ballymagarry Chalk Member, 13m thick here and with much greater overall flint content than the others. Immediately below its top, marked by a prominent and laterally extensive bedding plane, is an horizon full of the distinctive broken shell fragments of the large marine bivalve mollusc Inoceramus. The final member is the Tanderagee Chalk, 3.4m thick, weathering into slabby beds with plentiful fossils and tabular flints.
The pattern of invasion of what is now north-east Northern Ireland by the Cretaceous sea was very complicated. The rocks in Clarehill Quarry show that this was one of the last areas to be submerged, around 80 million years ago, and the sea was never very deep. The Portrush Chalk, for example, shows clear evidence of emergence and shallow water conditions in its lower part.
The historic interest of the quarry is of national significance and the condensed sequence of Ulster White Limestone members adds further importance. The site clearly meets the criteria for ASSI designation and should be preserved. The obvious threat is from dumping.
| Enlander, I., Dempster, M. & Doughty, P., 2024. Clarehill Quarry, County Down, site summary. [In] Earth Science Conservation Review. https://www.habitas.org.uk/escr/summary.php?item=1217. Accessed on 2024-12-26 |
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