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Earth Science Conservation Review
| Copney Hill | Tyrone |
| Site number: | 584 | ||
| ESCC: | EO | ||
| Locality Type: | Crags | Status: | ESCR |
| Grid Reference: | H600777 Centroid | ||
| Google maps: | 54.64434,-7.07061 | ||
| County: | Tyrone | Council area: | Fermanagh & Omagh District Council |
| Period: | Ordovician | ||
| Lithostrat: | Tyrone Volcanic Group, Copney Pillow-lava Formation | ||
| Site Description | |
|---|---|
| Highlights: | |
Copney Hill contains numerous outcrops of a variety of the rock types of the Tyrone Volcanic Group | |
| Introduction: | |
Copney Hill is a prominent feature in otherwise flat ground lying directly south of the main Omagh to Cookstown Road (A505), ~3km west southwest of Creggan. Access to the site is via a farm lane to the dwelling at [36025 37800] henceforth over poorly drained bogland and fenced rough pasture. This is an extensive site with outcrops of interest on several crags extending from the partially exposed stone circles at the foot of the northern face of Copney to the summit of Copney Hill. On Portlock's geological map of the area, (1843) the rocks at Copney are classified as "metamorphic rocks of hornblendic type". Portlock used lithological qualifiers on the map to differentiate porphyritic rocks, "traps" and granitic rocks. On the first edition of the one-inch to the mile geological map Sheet 26 (Draperstown, Geological Survey of Ireland, 1882) the rocks at Copney Hill were represented as "pyroxenic rocks" and were loosely classified as being of "Lower Silurian age". In the accompanying memoir, Nolan (1884) described a variety of rock types in the vicinity of Copney including quartz porphyry and "compact green rock". When Hartley (1933) published the first detailed lithological map and description of the central Tyrone Ordovician volcanic plutonic terrane, he included the rocks at Copney Hill within a broad belt of tuffs and andesites which he referred to as the Tyrone Igneous Series. On the second edition of Sheet 26 (Draperstown, Geological Survey of Northern Ireland, 1995), various lithologies are mapped on Copney Hill including quartz porphyry and feldspar phyric andesitic intrusions. Stratigraphically these lavas and tuffs form part of the Copney Pillow Lava Formation (Tyrone Volcanic Group). The Tyrone Volcanic Group is a major component of the Tyrone-Girvan Sub-Terrane of the Midland Valley Terrane (Bluck, 1992) and is broadly equivalent in age to the ophiolitic-volcanic associations at Girvan-Ballintrae (Scotland) and Clew Bay (County Mayo) | |
| Description: | |
The main lithologies at this site can be viewed by making a north-south traverse starting at the partially excavated stone circles [2600 3780] and examining various crags on the approach to Copney Hill from the north. The lower slopes, c.200m, contain outcrops of an acid porphyry rock which is a continuation of a larger quartz-feldspar-hornblende porphyry that outcrops extensively to the southwest in the vicinity of Loughmacrory Hill The most northerly crag at the Copney Hill site is Cloghanawack (270m OD). This consists primarily of splintery fine-grained mid-grey basaltic rock. These are mainly non-porphyritic lavas which locally have developed pillow structure. Wherever they can be seen the pillows are generally slightly flattened in the northeast-southwest trending plane of the regional stratigraphy. The outcrop is weathered to a variable extent and in parts is cross-cut by elaborate green and yellow epidote vein networks. On the south side of Cloghanawack lavas are interbedded with volcanic breccia and tuff. These pale grey and white rocks are conspicuously fragmental and consist of unsorted angular to sub angular mainly pale "acid" fragments up to 2-5cm diameter in a coarse-grained tuff matrix. Southeast of Cloghanawack, extending to the summit of Copney Hill, there are numerous outcrops of a distinctive pale grey porphyritic rock containing abundant 1-2mm long euhedral plagioclase feldspars and minor pyroxene? in a fine-grained matrix. Exposure of contact relationships of this rock with the surrounding lithologies (pillow lava and lapillae tuff) is poor and it is therefore not immediately obvious whether this is a lava or a hypabyssal volcanic rock. Outcrops in the vicinity of Copney Hill summit consist of lava, feldspar porphyritic rock and lapillae tuff. Once more, contact relationships between the two principal rock types are poorly exposed in the field. | |
| Importance: | |
Copney Hill is a site of national geological importance. The site provides access to high quality outcrop of a variety of lithologies typical of the Tyrone Volcanic Group. The distinctive grey, feldspar porphyry rock at Copney is unique to this area. | |
| Interpretation: | |
Copney Hill contains exposures of a diverse suite of igneous rocks which formed as a result of passive and explosive volcanic activity in an island arc or back arc environment and as a result of hypabyssal intrusion at deeper levels in the earth's crust. Arc formation was related to the progressive closure of the Iapetus Ocean which once separated the north American continental plate (Laurentia) from southern Britain (Avalonia). Arc magmatism was generated by the north-westerly directed subduction of the Iapetus oceanic crust along the Laurentian continental margin. | |
| Conclusions: | |
Copney Hill is a site of national importance. It is a valuable educational and research resource providing access to high quality outcrops of a variety of the lavas and tuff which represent a distinctive eruptive phase in the development of the Tyrone Volcanic Group. | |
| Notes: | |
For information and references on sites within the Tyrone Basic Plutonic Complex see the following sites: Key Site 580 - Black Rock Key Site 581 - Scalp Hill For information and references on other sites within the Tyrone Volcanic Group see the following sites: Key Site 582 - Mveela More Key Site 583 - Creggan Key Site 585 - Beaghbeg Key Site 586 - Bonnety Bush, Altihaskey Key Site 587 - Tullybrick Key Site 588 - Stuhanleanantawey Burn For information and references on Granitoid sites within the Caledonian Complexes of N. Ireland see the following sites: Key Site 589 - Cashel Rock Key Site 590 - Craigballyharky and Craigbardahessiagh Key Site 591 - Craiganawork, Pomeroy Key Site 592 - Tintagh, Slieve Gallion Key Site 593 - Loughmacrory Key Site 594 - Cushendun For general information and references on the Caledonian Igneous Complexes of N. Ireland, and for directions to other regional sites, see the following site: Key Site 595 - Introduction to the Caledonian Igneous Complexes of N. Ireland | |
| Keywords | |
|---|---|
| Rocks: | Feldspar porphyry, Pillow lava, Porphyry, Quartz porphyry |
| Structures: | Caledonian, pillow lava |
| Relations: | Extrusion |
| Access | |
|---|---|
| Approach: | Access to the site is via a farm lane to the dwelling at [36025 37800] henceforth over poorly drained bogland and fenced rough pasture. |
| Management: | |
Copney Hill encompasses a number of rocky knolls and outcrops in an area of partially fenced rough pasture. Currently the land is used to graze stock. The uneven and rocky nature of the area means that the site is unlikely to come under direct threat from building development. The state of vegetation and overgrowth of the site is currently at an acceptable level. The exposed and windswept nature of the site is likely to prevent serious overgrowth. The rocks of the Tyrone Volcanic Group are considered to be prospective for a number of minerals including base metals and gold. Licensed mineral exploration has previously been carried out throughout central Tyrone. The area which includes this site is likely to attract further exploration activity in the future. | |
| Uses | |
| Uses: | Rough pasture |
| Map(s): | GEOLOGICAL SURVEY OF IRELAND, 1882. 1:63,360 Geological Sheet 26 (Draperstown). (Dublin, Ordnance Survey for the Geological Survey of Ireland). GEOLOGICAL SURVEY OF NORTHERN IRELAND, 1995. Draperstown. Northern Ireland Sheet 26. Solid and Drift Geology. 1:50,000. (Keyworth, Nottingham: British Geological Survey). | ||
| Record type: | ESCR report | ||
| Entered by: | E M Porter | ||
| Last updated: | 04 MAR 2001 | ||
| Enlander, I., Dempster, M. & Doughty, P., 2026. Copney Hill, County Tyrone, site details. [In] Earth Science Conservation Review. https://www.habitas.org.uk/escr/site.php?item=584. Accessed on 2026-11-06. |
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