| Previous Site | Next Site |
Earth Science Conservation Review
| Toome | Londonderry |
| Site number: | 1252 | ||
| Locality Type: | Field, Subcrop | Status: | ASSI |
| Grid Reference: | H98929098 | ||
| Google maps: | 54.75675,-6.46379 | ||
| County: | Londonderry | Council area: | Mid Ulster District Council |
| Period: | Quaternary | ||
| Stages: | Holocene | ||
| Site Description | |
|---|---|
| Highlights: | |
Toome is a small remnant of the once extensive diatomite deposits of the Lough Neagh and Lower Bann. Recording the environmental history of the area through part of the Holocene, the deposits are of importance to a number of research specialisms. | |
| Introduction: | |
The area is of special scientific interest because of its deposits of diatomite and associated materials. Diatomite consists of accumulated diatom frustules with differing amounts of clay, silt, sand and peat. Diatoms are microscopic aquatic plants, surrounded by a silica box, or frustule, of various shapes, depending on the species. The diatomite (also known as Kieselguhr or Bann clay) deposits in Northern Ireland were one of the most extensive freshwater diatomite sequences of post-glacial age in Ireland or Britain. Past commercial exploitation in the Lough Neagh basin has reduced the area of intact material to a small number of localities. | |
| Description: | |
At Toome the diatomite forms part of the lowest lake terrace of Lough Neagh and is up to 2m above the present lough level. The strati graphic record shows a change in dominance from benthic (bottom dwelling) species of diatom to planktonic (free floating) species, indicating a transition to a deeper water environment. The former is of late Boreal age (pre - 7500 years BP). Deposition continued here beyond 5000 years BP (sub-Boreal) as indicated by the pollen record in the upper layers. This site contains the longest total sequence of diatomite and associated deposits (3-4m thick in places) encountered in a recent survey of the remaining diatomite deposits of the Bann valley. In addition, the site shows associations with organic material (early reed swamp peats) and geomorphological features (sandbanks together with former river channels or lagoons). This location is also of importance as any geomorphological changes here would have had considerable influence on water levels in the lough, given its position as the sole outlet for the entire Lough Neagh basin since post glacial times. | |
| Importance: | |
The diatomite is of international importance for biological, geological, hydrological and climatological reasons. Its archaeological significance is also considerable given its contemporaneous links with sites of early human settlement in Ireland. This assemblage gives a record of past water levels in the Lough Neagh basin, and of climatic change. These remaining sites are amongst the most important deposits of freshwater diatomite in the British Isles, and are unique when considered with the associated materials. | |
| Interpretation: | |
The deposits were mainly formed between 7500 and 5000 years before present (BP), and are found in low lying land around the northern shore of Lough Neagh and in the Lower Barm valley. Although diatomite was formed in water and represents the extent of a former, larger Lough Neagh, the presence in the deposits of archaeological remains shows that these marginal areas were only seasonally inundated. | |
| Conclusions: | |
The diatomite deposits of the Lough Neagh and Lower Bann areas have mainly been lost through commercial extraction. The remaining locations are of considerable significance to a range of research specialisms as well as their association with a lost industry. | |
| Notes: | |
Diatomite, also known locally as Bann Clay, occurs in a deposit up to 0.9 m thick in the valley of the River Bann between Toome [H 990 907] and Portglenone [C 980 039]. It was deposited in freshwater lakes during early post-glacial times and consists of the microscopic siliceous skeletons of diatoms. When dry, it is a friable, white, chemically inert powder that can be used as a filler in paint, plastic and rubber manufacture, but also as an absorbent in animal litter, an abrasive for metal polish, an insulant, and as a filtration agent in the food and pharmaceutical industries. Diatomite was extracted manually on a small scale until the late 1960s but is no longer worked. (GSNI source) See also site reports for Ballymacombs More (Record no. 1250) and Culnafay (Record no. 1251) and Introduction to the diatomite deposits of Northern Ireland (Record no. 1253) | |
| Keywords | |
|---|---|
| Minerals: | Diatomite |
| Rocks: | Diatomite |
| Fossil Groups: | Diatoms |
| Access | |
|---|---|
| Approach: | No public access. Field adjoining the Lough Neagh Fishermen's Co-operative Society |
| Restrictions: | Private land |
| Management: | |
Agricultural land used for grazing and silage production | |
| Threats: | Activities that change the host environment or physically disturb the deposits. Land drainage, deep ploughing, afforestation , development |
| Record type: | ESCR report | ||
| Entered by: | I J Enlander | ||
| Last updated: | 27 Mar 2019 | ||
| Enlander, I., Dempster, M. & Doughty, P., 2026. Toome, County Londonderry, site details. [In] Earth Science Conservation Review. https://www.habitas.org.uk/escr/site.php?item=1252. Accessed on 2026-11-07. |
| Previous Site | Next Site |