ESCR - Tircrevan Burn – Clay-with-Flints

Earth Science Conservation Review

Summary Full report
Tircrevan Burn – Clay-with-Flints

Site number:	1306
Locality Type:		Status:	ASSI
Grid Reference:	C70313220
Google maps:	55.13247,-6.89781
County:		Council area:	Causeway Coast & Glens Borough Council
Period:	Cretaceous, Tertiary

Site Description
Highlights:
In Tircrevan Burn, the lithostratigraphy of the sedimentary rocks that occur stratigraphically between the Cretaceous chalk and the succeeding Palaeogene basalt lavas is unique in that it includes a thin interval of lacustrine sediments overlying lithologies typical of the Clay-with-Flints. Although the section is poorly exposed it is believed that there is a disconformity below the lacustrine sediments, indicating a time gap after the deposition of the Clay-with-Flints. The lacustrine sediments are unnamed. Nevertheless, their presence is unusual and warrants the inclusion of this locality in an assessment of the Claywith-Flints in Northern Ireland.
Introduction:
The intermittent exposures in Tircrevan Burn constitute one of the best sections of Mesozoic and Cenozoic sedimentary rocks in this part of Northern Ireland. Consequently, the Geological Survey of Northern Ireland nominated some 800m of Tircrevan Burn, south of Tircrevan Bridge, as a Site of Special Scientific Interest, with special reference to the Early Jurassic Waterloo Mudstone Formation and the Late Cretaceous Hibernian Greensands and Ulster White Limestone formations. All parts of the steep sided valley south of Tircrevan Bridge show signs of recent episodes of land slip. This primarily affects the layer of glacial till (boulder clay), at least 6m thick, which caps the sides of the valley and from which the layer of soil masking much of the valley sides has been derived. Large blocks of chalk and basalt choke the stream and lower sides of the valley. Indeed, Photograph 28 not only shows features of the Clay-with-Flints at Site 6 but also demonstrates the initial development of a back scar above an area of landslip just above the site. Because of the inherent instability of the valley sides it is likely that the area of Clay-with-Flints exposed from year to year will vary considerably. At the present locality the Clay-with-Flints is partially covered by plant growth, sporadic thin and discontinuous patches of slipped soil and thin scree of black lignitic clay from the overlying organic deposit.
Description:
Site Geology: Ulster White Limestone Formation: About 10m of white chalk representing the Late Cretaceous Ulster White Limestone Formation in Tircrevan Burn is representative of the eponymous Londonderry Shelf (Figures 2 and 3). This was an area of shallow water sedimentation developed during late Santonian and Campanian times that was prone to episodes of uplift and non-deposition, thereby interrupting the depositional sequence of chalk members that characterises the deeper basins (Fletcher, 1977). As a consequence, the sequence of chalk members that were deposited on the Londonderry Shelf is incomplete and condensed when compared to the adjacent basins and many of the members recorded there, when present on the shelf area, are correspondingly attenuated. In Tircrevan Burn the base of the Ulster White Limestone Formation is represented by the Galboly Chalk Member which is overlain by a succession comprising the Creggan Chalk, Ballintoy Chalk, Garron Chalk with the Portrush Chalk Member at the top. Clay-with-Flints: There is one known exposure of the Clay-with-Flints in Tircrevan Burn overlying chalk of the Ulster White Limestone Formation. Antrim Lava Group: As for Site 5, the basalt lavas overlying the Clay-with-Flints in Tircrevan Burn may belong to either the Lower Basalt or Upper Basalt Formation of the Early Palaeogene Antrim Lava Group. The assignment will depend largely on whether or not the 13m thick layer of deeply weathered greenish coloured basalt or lithomarge in the quarry near Site 5 is recognised as the Interbasaltic Formation. The contact of the Clay-with-Flints and the basalt lavas is not exposed. The Clay-with-Flints detail: Because of the imperfect exposure of the Clay-with-Flints in Tircrevan Burn, little new information is available that differs from other exposures of the unit. The lower part of the section is typical of the Clay-with-Flints and consists of between 1m and 1.2m of soft, brown to khaki coloured clay, apparently structureless, containing large intact flint nodules (Photograph 29). All nodules show a slight pink staining of the external white crust while internally are the greyish brown colour so typical of flint still in the chalk host rock. Unique to Site 6 however, is the preservation of fine-grained, organic-rich sediments above the flint-rich lower section, which were deposited in a lacustrine environment (Photograph 30). At the base of these sediments the lignite and lignitic clay appear to drape the uneven top surface of the Clay-with-Flints (Figure 21). Their upper contact with the base of the basalt lava flows of the Antrim Lava Group is not exposed. Palaeontology Organic residues from the lignite and lignitic clay contain plant tissue, wood fragments and extremely sparse, low diversity miospore floras dominated by long-ranging Cretaceous and Palaeogene spores and pollen. The association of pollen including Caryapollenites simplex, Triatriopollenites, Tricolporopollenites and Trivestibulopollenites betuloides (Figure 5, Fossil 5) is of Palaeogene aspect. The range base of Carya pollen is in the Paleocene. Based on an age of about 60 million years for the first basalt lava flow, the lignitic beds are probably Danian. The palynofloras are indicative of low-lying swamp conditions with a cool temperate climate.
Conclusions:
Few details are available for the main part of the Clay-with-Flints in Tircrevan Burn. However, what is unusual and unique about this site is the presence of a thin interval of lacustrine sediments, including clay and lignite, overlying the normal flint-rich multicoloured clay that is so typical of the Clay-with-Flints. Low diversity pollen assemblages provide clues as to the climate at the time of lake formation and constrain the age of the deposit to the Danian Stage of the Paleocene.
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
Rocks:	Chalk, Clay, Flint, Basalt

Access
Approach:	Private land. Located within the deeply incised, steep sided and heavily vegetated gully created by the Tircrevan Burn, SSE of Tircrevan Bridge (Photograph 28), is a single exposure of the Clay-with-Flints [Grid Ref: C7031 3220] positioned just above river level, 720m SSE of Tircrevan Bridge. Access to the exposure is possible either by following the river course and the narrow, vegetated river banks upstream from Tircrevan Bridge or from agricultural land on the east flank of the gully with a steep, potentially hazardous, climb down to river level. The valley of the Tircrevan Burn is the boundary between Tircrevan and Lower Ballyleighery townlands and the site is located 2.3km NNE from the Triangulation Point at Binevenagh and 9.6km NNE of Limavady town centre, Co. Londonderry (Figures 19 and 20).
Restrictions:	Private land

Access

Approach:

Private land. Located within the deeply incised, steep sided and heavily vegetated gully created by the Tircrevan Burn, SSE of Tircrevan Bridge (Photograph 28), is a single exposure of the Clay-with-Flints [Grid Ref: C7031 3220] positioned just above river level, 720m SSE of Tircrevan Bridge. Access to the exposure is possible either by following the river course and the narrow, vegetated river banks upstream from Tircrevan Bridge or from agricultural land on the east flank of the gully with a steep, potentially hazardous, climb down to river level. The valley of the Tircrevan Burn is the boundary between Tircrevan and Lower Ballyleighery townlands and the site is located 2.3km NNE from the Triangulation Point at Binevenagh and 9.6km NNE of Limavady town centre, Co. Londonderry (Figures 19 and 20).

Restrictions:

Private land


Record type:	ESCR report
Entered by:	I J Enlander
Last updated:	28 Mar 2019

Enlander, I., Dempster, M. & Doughty, P., 2026. Tircrevan Burn – Clay-with-Flints, County , site details. [In] Earth Science Conservation Review.
https://www.habitas.org.uk/escr/site.php?item=1306. Accessed on 2026-11-07.