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Earth Science Conservation Review
| Tircreven Burn (Mesozoic stratigraphy) | Londonderry |
| Site number: | 1206 | ||
| ESCC: | EO | ||
| Locality Type: | Stream section | Status: | ASSI |
| Grid Reference: | C701328 End(s) of linear site | ||
| Google maps: | 55.13789,-6.9008 | ||
| County: | Londonderry | Council area: | Causeway Coast & Glens Borough Council |
| Period: | Cretaceous, Jurassic | ||
| Stages: | Cenomanian, Hettangian, Santonian, Sinemurian | ||
| Lithostrat: | Hibernian Greensands Formation, Lias Undivided, Lower, Tircrevan Sandstone Member, Ulster White Limestone Formation, Waterloo Mudstone Formation | ||
| Site Description | |
|---|---|
| Highlights: | |
The exposures in the deeply incised Tircreven Burn include the type section of the Tircreven Sandstone Member of the Waterloo Mudstone Formation together with good exposures of the Cretaceous strata. | |
| Introduction: | |
The Tircreven Burn section is 9km NE of Limavady Co. Londonderry. The upper part of the Lias sequence, including the Tircreven Sandstone Member, and the Cretaceous strata are well exposed upstream of Tircreven Bridge. Best approached at times of low flow this stream section if the best locality in the NW of N. Ireland for the Lias and the lower part of the Upper Cretaceous. The amount of grey Liassic mudstone visible varies from year to year depending on the stream activity. The area was surveyed by Portlock (1843) who gave details of the Lias and Cretaceous strata and mentioned trials made for coal. Nolan and Egan (1885) carried out the next geological survey but concluded that Liassic strata did not crop out below the greensand. Hancock (1961) briefly described the Cretaceous rocks but the most detailed account is given in Bazley et al. (1996). | |
| Description: | |
The total thickness of the Lias in this area is probably about 180m of which about 52m are exposed in this section. The lower part of the Waterloo Mudstone Formation is seen in the Magilligan borehole. The Tircreven Burn section consists largely of calcareous mudstone with about 13m of sandstone forming the Tircreven Sandstone Member. About 13m below the sandstone the mudstones contain a massive 0.25m thick limestone with Gryphaea. Several of the mudstones have a `pseudobrecciated' structure possibly due to a combination of periglacial and landslip movement. Fossils are present but not very common. The Tircreven Sandstone Member forms pavements over which the river flows. The lower contact is sharp with sand-filled burrows penetrating into the mudstones below and indicating a non- sequence. The lowest 5.8m is composed of thick beds of soft, weathered, fine-grained, micaceous, silty grey and brown sandstone, with abundant worm burrows and plant fragments. The next 4.6m consists of mainly clean, well sorted, fine-grained, white or light brown sand in beds up to 0.33m thick. The beds above the Tircreven Sandstone Member are ~24m thick and include the youngest Lias proved west of Coleraine and consist of dark grey calcareous mudstones and thin limestones. The Liassic strata are summarised below: WATERLOO MUDSTONE FORMATION Mudstone, tough, calcareous, olive-brown, very fossiliferous, 0.13m Shale, dark blue-grey, calcareous; very fossiliferous with crinoid columnals; Gryphaea arcuata, Oxytoma inequivalvis, pyritised Arnioceras semicostatum, Euagassiceras sp., 0.74m Limestone, earthy, clayey, hard; very poorly fossiliferous, crinoid ossicles and indeterminate bivalves, 0.15m Shale, blue/grey, calcareous, finely micaceous, poorly fissile; few macrofossils, ostracods, 1.50m Concealed strata under tallus, ~1.50m Shale, disturbed, fragments of poorly fossiliferous blue-grey calcareous shale in matrix of slickensided clay, small bivalves, a 0.13m micrite bed is represented by separated blocks, Plagiostoma giganteum, 0.91m Concealed strata under till, ~4.50m Shale, medium blue-grey, calcareous, pseudobrecciated; small bivalves, 2.44m Mudstone, compact, poorly fissile, calcareous; Calcirhynchia sp., poorly preserved bivalves including G. arcuata, Oxytoma inequivalvis, P. giganteum, 0.18m Shale, as above, ~0.30m Concealed strata under boulders, ~0.90m Shale, fine, blue-grey, calcareous; abundant small bivalves, 0.18m Concealed strata under boulders, ~6.40m Shale, pseudobrecciated blue-grey, calcareous, in slickensided clay matrix; some lighter micaceous mudstone, ~1.20m Concealed strata beneath boulders and till, ~3.00m Shale, as above, ~0.30m Concealed strata beneath boulders and till, ~3.00m TIRCREVEN SANDSTONE MEMBER Siltstone, soft, brown, decalcified; Gryphaea arcuata and Plagiostoma?, 0.15m Sandstone, hard, calcareous, shelly, 0.15m Sandstone, soft, calcareous, dark brown, weathered, some harder lenses; poorly fossiliferous, P. giganteum, 0.66m Sand, hard, calcareous rib; Plicatula sp., Cenoceras sp., 0.15m Sandstone, soft, calcareous, dark brown, weathered; some hard fresh calcareous nodules, ~0.30m Sandstone, hard, calcareous rib, ~0.08m Sandstone, soft, brown, ~0.18m Sandstone, hard, calcareous rib; irregular nodule, ~0.06m Sandstone, soft, brown, ~0.13m Sandstone, fine-grained, grey, indurated, calcareous; or sandy limestone, 0.08m Sandstone, soft, brown, silty, micaceous, 0.50m Sandstone, quartzose, fine-grained, indurated, grey, calcareous, or sandy limestone; sharp base; Pleuromya sp., Ptychomphalus solaroides, 0.11m Sandstone, quartzose, soft, brown, fine-grained, micaceous, calcareous; a 0.05m lens of hard calcareous sandstone 0.32m up, 0.53m Sandstone, quartzose, hard, highly calcareous, or sandy limestone; irregular surface; Pinna sp., P. giganteum, Ptychomphalus solaroides, Zoophycus, 0.15m Sandstone, soft, brown, silty, micaceous; Antiquilima antiquata, Pholadomya sp., 0-0.10m Sandstone, quartzose, hard, compact, pale brown, fine to medium-grained, calcareous or sandy limestone; poorly fossiliferous; in places decalcified to a fine reddish sand, 0.35m Sand, silty, medium brown and grey, 0.13m Sand, medium brown, fine, micaceous, 0.10m Sand, light brown, silty; alternating with dark brown, clayey silt, 0.10m Sand, fine, light brown, 0.13m Sand, light brown, silty; alternating with dark brown silty clay, 0.15m Sand, fine, silty with thin silty clay partings, 0.18m Sand, black and dark brown, silty, 0.01m Sand, fine, light brown to white, 0.28m Silt, micaceous, clayey, 0.02m Sand, fine, light brown, 0.33m Sand, fine, light brown; alternating with dark brown silty clay, 0.07m Sandstone, grey, silty, micaceous, 0-0.08m Sand, fine, light brown, 0.15m Concealed strata beneath till, ~1.20m Sand, light brown, fine; with thin siltstone alternations, 0.30m Siltstone, grey, with thin beds of fine white sandstone, 0.35m Sand, fine, clean, white, with thin clay beds, 0.61m Clay, brown; alternating with fine white sand, 0.10m Sand, fine, clean, white, 0.32m Sandstone (subgreywacke), soft, fine, micaceous, silty non-calcareous, grey to brown grading into siltstone; carbonaceous plant fragments and worm burrows abundant, 2.90m Concealed strata, ~2.74m Sandstone, medium brown, silty; worm burrows infilled with fine white sand, and fragmentary vegetation, 0.15m WATERLOO MUDSTONE FORMATION Shale, light grey, silty, micaceous; worm burrows infilled with grey silt, and fragmentary vegetation, 0.30m Concealed strata, ~1.20m Shale, silty, grey, partly micaceous, pseudobrecciated; abundant lignitic fragments, 0.46m Concealed strata beneath boulders, ~1.80m Mudstone, soft, grey, calcareous, poorly fissile, pseudobrecciated; fossiliferous, 0.30m Limestone, irregular, silty, shelly micaceous, or calcareous sandstone, richly fossiliferous, Cardinia listeri, Liostrea hisingeri and Schlotheimia sp., 0.01-0.04m Mudstone, medium grey, calcareous, poorly fissile, pseudobrecciated; ostrocods, Pteromya sp., vague plant remains, 0.30m Concealed strata beneath boulders, ~1.20m Mudstone, shaly, micaceous, silty, poorly calcareous, poorly fissile, pseudobrecciated with thin alternations and lenses of light grey and fawn micaceous, cross-laminated, pyritous, calcareous siltstone with ripple marks or worm tracks; plant fragments common; occasional flat brown limestone nodules with plant fragments, ~5.18m Shale, medium grey, poorly calcareous, pseudo-brecciated; fossiliferous with Gryphaea arcuata, contact with bed above faulted and slickensided, 1.14m Shale, medium to dark grey, shelly, calcareous, poorly fissile, transitional base, crinoid columns, abundant Gryphaea arcuata, P. giganteum, 0.10m Limestone, light grey shelly, Calcirhynchia calcaria, abundant Gryphaea arcuata and Plagiostoma?, 0.25m Shale, fine, light grey, calcareous, pseudobrecciated; with bivalves, 1.22m At Tircreven Burn, where pre-Basalt erosion removed most of the White Limestone, the total Cretaceous succession is only some 10m thick. The sequence, here on the Londonderry Shelf, is much condensed compared with the Rathlin Basin (see Cretaceous sites) and the Cretaceous rocks lie unconformably on the Waterloo Mudstone Formation. The Hibernian Greensands Formation in Tircreven Burn is quite different from that developed in East Antrim and the members defined there cannot be recognised. The succession is complex but can be divided into two or perhaps three lithological units of potential member status. The sequence below lies in a series of faulted or rotationally slipped blocks: HIBERNIAN GREENSANDS FORMATION Sandstone or sandy limestone, light green, glauconitic, abundant cherty nodules and Thallasinoides burrows throughout, sometimes of irregular shape; Inoceramus plates (Bed 74), 0.70m Sandstone, or sandy limestone, laminated and flaggy; no nodules (Bed 73), 0.03m Sandstone or sandy limestone, light green, glauconitic, cherty nodules and Thallasinoides burrows in lowest 0.3m; top becomes laminated; Inoceramus plates (Bed 72), 0.55m Sandstone or sandy limestone, laminated; no nodules (Bed 71), 0.05m Sandstone or sandy limestone, light green, glauconitic, cherty nodules and Thallasinoides burrows in lowest 0.3m; top becomes laminated; Inoceramus plates, broken echinoid and small belemnite (Bed 70), 0.53m Sandstone, hard, medium grained, glauconitic, light green; occasional small quartz pebbles; few cherty nodules and vertical burrows (about 0.01m diameter) up to 0.25m long; Inoceramus sp., Micraster sp., Exogyra sp., (Bed 69), 0.43m Clay, dark green, weathering brown (Bed 68), 0.006m Sandstone, dark green, glauconitic, friable; small quartz pebbles; Exogyra sp., Inoceramus sp., `Isomicraster' sp., fish teeth, small belemnites including Actinocamax verus, Liostrea sp., irregular piped and bored contact with bed below (Bed 67), 0.4-0.55m Sandstone, hard, fawn, compact, calcareous, or sandy limestone; a few small pebbles; bivalve fauna including large Inoceramus sp., fragments (Bed 66), 0.36-0.55m Sandstone, soft, fawn, friable, fine-grained, calcareous; numerous rounded and polished granules and pebbles of quartz; basal 0.08m is coarse and pebbly with numerous rolled derived Lias fossils and phosphatic faecal pellets, including fish teeth, reptile and/or amphibian bones, Gryphaea arcuata and Pentacrinites sp. (Bed 65), 0.30m The basal unit (Beds 65 & 66) comprises fossiliferous calcareous brown glauconitic sandstones resting on a basal 'bone-bed' and grading up into hard highly fossiliferous sparsely glauconitic white or buff coloured calcareous sandstones with a bored erosion surface. The age of this unit is uncertain. The basal 'bone-bed' contains rolled small teeth and bones together with reworked Gryphaea arcuata and columnals of Pentacrinites sp. derived from the underlying Lias. In addition there are diminutive gastropods and bivalves (1-3mm max. dimension) which may either be of Liassic or Cretaceous age. The friable brown sandstone contains thick fragments of inoceramid shell, Ctenoids sp., Oxytoma sp., Spondylus spp. and small pycnodonteine and exogyrine oysters; this bed has also yielded an incomplete large thin-shelled flat inoceramid. The fauna of the overlying pale coloured sandstones is significantly different, but many of the fossils are partly or wholly decalcified rendering determination difficult. It is a fauna of high diversity characterised by abundant small pectinaceans (Syncyclonema sp.) and the livid Limatula cf. fittoni d'Orbigny together with irregularly shaped bivalves tentatively attributed to Anomia and/or Placunopsis. Other fossils present include Camptonectes cf. virgatus (Nilsson), Limea? sp., Neithea sp., Pseudoptera sp., bryozoa, small lophine and exogyrine oysters, chelae of the 'shrimp' Protocallianassa, and indeterminate echinoderm fragments. These basal sandstones of uncertain age are overlain with an erosive and unconformable contact by friable pale green calcareous glauconitic sandstones containing the spinose exogyrine oyster Castagyra laciniata (Goldfuss) and the small belemnite Actinocamax verus Miller. Additional members of the fauna include Gryphaeostrea canaliculata (T. Sowerby) Limatula Semisulcata (Nilsson), Plagiostoma sp., Spondylus spinosus, pieces of inoceramid shell, Micraster ex gr. gibbus Lamarck and reworked phosphatised bivalve steinkerus and Selechian teeth such as Squalicorax galcatus (Agassiz). Overlying the basal greensands (Beds 67-69) with their faunas of apparently southern affinities, is a sequence of beds (Beds 70-74) with Thalassinoides burrow-form cherts, including laminated beds completely void of cherts. Apart from thick pieces of inoceramid shell (Platyceramus?) and poorly preserved sponges, this cherty unit contains few obvious macrofossils. Immediately above the lowest bed with cherts, however, the chert-free laminated bed yielded a large flat Micraster (M. rogalae Nowak) and Actinocamax verus. The section through the Ulster White Limestone is: ULSTER WHITE LIMESTONE FORMATION Limestone, white, hard, fractured irregularly, pink flint nodules; poorly fossiliferous with Belemnitella sp.; very poorly exposed (Bed 78), 5.40m Stromatolite, reddish yellow (Bed 77), 0.01m Limestone, hard, poorly glauconitic, rubbly fractured, becomes massive near top, transitional base (Bed 76), 1.05m Limestone, light green, sandy glauconitic, massive; irregular fawn phosphate nodules in upper part; fossiliferous with Micraster bed, Echinocorys sp., large and small belemnites including Gonioteuthis sp., Porosphaera sp., ribbed bivalve, Liostrea sp., (Bed 75), 1.50m The Ulster White Limestone succession comprises Beds 75-78 inclusive, but the sequence is more complex than is implied by this classification. Bed 75 can be divided into a lower part without pebbles, and a higher part containing small phosphatised and weakly glauconitised pebbles, many of which are poorly preserved, and fragmentary hexactinellid sponges. Inoceramid shell sheets are conspicuous 0.25m above the base and at 0.45m there is a level with large decalcified flat Micraster sp., possibly the M. rogalae found near the base of the cherty part of the Hibernian Greensands, but too poorly preserved for certain determination. An Echinocorys, likewise decalcified, from near the base of the band with phosphatised pebbles, is incomplete but the straight-sided and flat-topped profile is suggestive of variants characterising a low level in the Vintacrinus socialis Zone in chalk facies. The sponges at this level have not all been identified, but include several Callopegma obconicum Hinde and a calcisponge, Porosphaera. The lower part of the pebble-rich band yields Actinocamax verus, a species which thus ranges up from the Costagyra laciniata band (Bed 66) near the base of the Hibernian Greensands. Gonioteuthis enters within the pebble-rich band 80-85cm above the base of Bed 75 and is conspicuous at 0.85m above the base. The Gonioteuthis have Riedel Quotients falling within the range of G. quadrata and at the limit between G. granulatoquadrata (Stolley) and G. quadrata. The pebble bed is overlain by a unit with closely spaced sub-horizontal glauconitised surfaces: a Gonioteuthis from just above the base falls within the range of G. quadrata. No fossils have been collected from the hard splintery glauconitic limestone forming the higher part of bed 76, but inoceramid shell debris has been noted just beneath the Algal Bed. The post-Algal Bed succession comprises three thin flintless limestone units each terminating in a glauconitised erosion surface, overlain by flinty chalk. The top surface is much more strongly mineralised and convolute than the two lower surfaces and is covered by remani‚ mineralised pebble fossils including Echinocorys ex gr. gibba (Lamarck), Cardiotaxis neberle (Cotteau) Procardia cordata (Tate) and Patagiosites griffithi (Sharpe). | |
| Importance: | |
The site is of national importance as the type section for the Tircreven Sandstone Member of the Waterloo Mudstone Formation. It is the most westerly outcrop of the Lias in N. Ireland. The site also is representative of the condensed Londonderry Shelf Cretaceous sequence. | |
| Interpretation: | |
From the Tircreven Sandstone Member, the marine fauna included crinoid fragments, Antiquilima, Cardinia, Gryphaea, Phaladomya, Pinna, Plagiostoma, Pleuromya, Plicatula, Ptychomphalus solaroides and Cenoceras sp. A specimen of Euagassiceras seuzeannum in the Queen's University, Belfast collection suggests that the Tircreven Sandstone may include beds of sauzeannum Subzone age. The beds above the sandstone include the youngest Lias of Lower Sinemurian age, proved west of Coleraine. Ammonites from just below the Cretaceous include fragments attributed to late species of Coroniceras, Arnioceras semicostatum and Euagassiceras indicating the sauzeannum Subzone of the semicostatum Zone. The basal Cretaceous strata rest unconformably on beds ranging in age from Triassic to early Liassic. This major unconformity occurs throughout N. Ireland, with no rocks remaining representative of the long period between the deposition of the Lower Lias and the renewal of sedimentation at the beginning of the late Cretaceous (Cenomanian). At the top of the Cretaceous is another major erosion surface with pockets of a solution residue of chalk, comprising mostly flint debris underlying early Palaeogene basaltic lava flows. Both Cretaceous formations contain a diverse macrofauna, of which the echinoids, belemnites and, to a lesser extent, the sponges and ammonites have proved the most useful for correlative purposes. No strata older than Santonian (Micraster coranguinum Zone) have been proved, but there is evidence that the basal Cretaceous beds at Tircreven Burn may be considerably older, perhaps of Turonian or even Cenomanian age. The fragments of thick-shelled inoceramids found in Bed 65 have their closest parallels in the inoceramids of Inoceramus Bands of the Coniacian portion of the Kilcoan Sands Member of East Antrim and the occurrence of Spondylus spp. including a possible S. spinosus (T. Sowerby) would also support such a correlation. The thin-shelled inoceramid from this level could then be comparable with an early Coniacian Cremnoceramus. The fauna of the pale coloured sandstones, however, is similar to that of parts of the Collinwell Sands Member of the Belfast area, particularly in the occurrence of Syncyclonema sp. and Protocallianassa sp., and this could point to a late Cenomanian or Turonian age, although the fauna is, strictly speaking, a non-diagnostic facies fauna. The microfaunal evidence is equally inconclusive. Bed 65 contained a very sparse fauna broken and corroded foraminiferids including Arenobulimina advena (Cushman), Bavelinella intermedia (Berthelin) and Tritaxia pyramidata Reuss. A sample from the higher bed yields a sparse fauna dominated by G. intermedia, with subordinate Marssonella Ozawai Cushman and I. pyramidata. No planktonic species were present in either sample. Both assemblages indicate a Cenomanian or possibly latest Albian age. Of the species present, A. advena, G. intermedia and I. pyramidata all range up to the late Cenomanian Metoicoceras geslinianum Zone in chalk facies, whilst M. ozawai does not reach the top of the early Cenomanian Mantelliceras mantelli Zone. It is difficult to reconcile the macrofossil evidence from Bed 65 with the evidence for an Albian- Cenomanian age for both Beds 65 and 66 based on microfossils, but the broken and corroded character of the microfossils suggests that they could have been reworked from pre-existing sediment. In contrast to the apparently younger age indicated by the macro- fossils from Bed 65, the macrofossil assemblage of Bed 66 has a pronounced Cenomanian aspect. The friable pale green calcareous glauconitic sandstones are of unequivocal Santonian age. Actinocamax verus first appears in chalk facies in the higher (Santonian) part of the Micraster coranguinum Zone and is particularly common in, and characteristic of, the overlying Vintacrinus socialis Zone. Castagyra laciniatar likewise indicates a Santonian age, and is found in abundance in late Santonian and basal Campanian arenaceous sediments in the Munster 'Basin' of western Germany. The Micraster from these basal greensands were attributed by Reid (1971) in part to Isomicraster senonensis Lambert [= M. gibbus Lamarck], implying a correlation with the Sponge Beds of the east coast. Although this correlation may be correct in view of the relative abundance of the associated Actinocamax verus, the Micraster in question are quite distinct from the true M. gibbus of the Cloghfin Sponge Beds, and are in fact quite unlike any described species. In common with M. gibbus they are gibbous (i.e. tending to a conical profile) but are characterised by extremely long, narrow and parallel sided ambulacral areas with numerous and relatively widely-spaced pore-pairs. There is no apparent subanal fasciole and the labrum is relatively advanced. Other distinguishing characteristics are the retracted posterior, the relatively posterior position of the apical disc, and the tendency (particularly in Hancock's two specimens from Bed 69) to a nearly circular rather than heart-shaped outline. Micraster with long petals are typically found in more southern and presumably warmer water environments, and it is tempting to speculate that these remarkable Tircreven forms may represent a southern geographical subspecies or warm water ecomorph of M. gibbus, an indication supported by the presence of warm water oysters such as Costagyra. The discovery of M. rogalae in Bed 71 overlying a unit with an apparently warm water macrofaunal assemblage was both unexpected and remarkable, as this species characterises the equivalent of the highest part of the coranguinum Zone in western Germany, Poland and the former USSR, areas which are normally considered to have been situated in a relatively northern palaeogeographical position. In Germany, this distinctive species is sufficiently common to be used as a zonal index. Though the Santonian age of these Tircreven chert-free and over- lying cherty greensands cannot be disputed, it is far from clear how the succession should be correlated either with Santonian successions elsewhere in N. Ireland (Kilcoan Sands and Cloghfin Sponge Beds of east Antrim) or with Santonian chalk successions in England or Germany. There is a clear distinction between the beds with Micraster ex gr. gibbus and Costagyra below and the overlying poorly fossiliferous cherty sequence with M. rogalae, the only fossil in common being Actinocamax verus. A. verus enters within the equivalent of the M. rogalae Zone in the southern English (Anglo-Paris Basin) chalk succession, and its occurrence in the Costagyra bed is thus anomalous in this context. On the other hand M. gibbus, whilst never common, is best represented in that part of the corangiunum Zone which underlies the equivalent of the rogalae Zone. It is therefore possible that the M. ex gr. gibbus of Tircreven are warm water ecomorphs occupying this stratigraph- ical level and that the belemnites are entering in western Ireland earlier and in greater abundance than elsewhere. On this tentative evidence, the Tircreven Hibernian Greensands could be attributed to the M. coranguinum Zone of the standard Chalk facies zonal scheme, and correlated with the higher part of the Kilcoan Sands and basal Cloghfin Sponge Beds of the east Antrim sequences. The other possibility is that the generally late Santonian age of A. verus and C. laciniata should be taken as the diagnostic criterion in which case both the chert free and cherty greensands with A. verus (and no Gonioteuthis) could be attributed to the equivalent of the U. socialis Zone Galboly Chalk of the standard succession. FURTHER TEXT TO BE ADDED | |
| Conclusions: | |
As the stratotype for the best developed sandstones in the Lias of Northern reland, the Tircreven Burn section should be conserved. | |
| Notes: | |
For information on other Jurassic sites see Key Site 16 - Waterloo and Key Site 1205 - Portrush - Jurassic. For general information on the Jurassic System in N. Ireland see Key Site 1193 - The Jurassic System in N. Ireland - Introduction. | |
| Keywords | |
|---|---|
| Rocks: | Limestone, Mudstone, Sand, Sandstone, Shale, Siltstone |
| Fossil Groups: | Ammonite, Annelid, Belemnite, Bivalve, Crinoid, Crustacea, Echinoderm, Fish, Foraminifera, Gastropod, Goniatite, Polyzoan, Sponge, Trace fossil |
| Access | |
|---|---|
| Approach: | Acces to the site is from Tircreven Bridge. The section is steeply incised and care should be taken at all times. Periods of high water levels are to be avoided. |
| Record type: | ESCR report | ||
| Entered by: | E M Porter | ||
| Enlander, I., Dempster, M. & Doughty, P., 2026. Tircreven Burn (Mesozoic stratigraphy), County Londonderry, site details. [In] Earth Science Conservation Review. https://www.habitas.org.uk/escr/site.php?item=1206. Accessed on 2026-11-07. |
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