Earth Science Conservation Review
| Black Rock | Tyrone |
| Site Type: | Inland exposure |
| Site Status: | ESCR |
| Grid Reference: | H685836 |
| Google maps: | 54.69624,-6.93759 |
| Rocks | |
|---|---|
| Rock Age: | Ordovician |
| Rock Name: | Tyrone Volcanic Group |
| Rock Type: | Gabbro, Tuff, Dacite |
| Interest | |
| Minerals: | Epidote |
| Other interest: | Caledonian, phenocrysts, Intrusion |
Introduction:
Black Rock is a prominent topographic feature in otherwise flat-lying country about 2.5km north of Dunnamore and 400m south of the stone circles at Beaghmore. Access to the eastern side of the site is from the Blackrock Road while access to the southern and western sides is from the Beaghmore Road.
On Portlock's early geological map of the area, (1843) all rocks in the vicinity of Black Rock were included within the category "metamorphic rocks of hornblendic type". Portlock's map did not delineate individual rock types but did include specific lithological qualifiers for "trap", "diallage", "slate" and "porphyry."
On the first edition of the one-inch to the mile scale geological map (Sheet 26, Draperstown, Geological Survey of Ireland, 1882) the rocks at Black Rock were grouped together and referred to as "Pyroxenic Rocks". These formed part of the "Metamorphic and Igneous Rocks" on the map and were referred to as being "Probably of Pre-Cambrian or Upper Laurentian Age". In the memoir which accompanied the map, Nolan (1884) referred to the "wonderful variety in the rocks" occurring at Black Rock.
Hartley (1933) published the first detailed lithological map and description of the central Tyrone Ordovician volcanicplutonic terrane. He incorporated the rocks at Black Rock within a division which he referred to as the "Crush Complex", part of what he termed the "Tyrone Igneous Series". The crush complex occurs immediately north and south of the Central Tyrone Metamorphic Inlier. Hartley characterized the crush complex by the close intermingling of many igneous lithologies.
On the second edition (1:50,000 scale) of Sheet 26(Draperstown) (Geological Survey of Northern Ireland, 1995), the rocks at Black Rock are included within the Tyrone Plutonic Group which is broadly equivalent to Hartley's Crushed Complex. The Tyrone Plutonic Complex surrounds and is in faulted contact with the high grade metamorphic inlier (Corvanaghan Formation) The Tyrone Plutonic Group forms part of the Tyrone Ophiolite Complex, interpreted as being a fragment of Ordovician island arc or back-arc oceanic crust (Hutton et al., 1985). These rocks form part of the Tyrone-Girvan Sub-Terrane of the Midland Valley Terrane as defined by Bluck et al. (1992 and can broadly be correlated with comparable ophiolitic rocks at Ballintrae in Scotland and Clew Bay in western Ireland.
On Portlock's early geological map of the area, (1843) all rocks in the vicinity of Black Rock were included within the category "metamorphic rocks of hornblendic type". Portlock's map did not delineate individual rock types but did include specific lithological qualifiers for "trap", "diallage", "slate" and "porphyry."
On the first edition of the one-inch to the mile scale geological map (Sheet 26, Draperstown, Geological Survey of Ireland, 1882) the rocks at Black Rock were grouped together and referred to as "Pyroxenic Rocks". These formed part of the "Metamorphic and Igneous Rocks" on the map and were referred to as being "Probably of Pre-Cambrian or Upper Laurentian Age". In the memoir which accompanied the map, Nolan (1884) referred to the "wonderful variety in the rocks" occurring at Black Rock.
Hartley (1933) published the first detailed lithological map and description of the central Tyrone Ordovician volcanicplutonic terrane. He incorporated the rocks at Black Rock within a division which he referred to as the "Crush Complex", part of what he termed the "Tyrone Igneous Series". The crush complex occurs immediately north and south of the Central Tyrone Metamorphic Inlier. Hartley characterized the crush complex by the close intermingling of many igneous lithologies.
On the second edition (1:50,000 scale) of Sheet 26(Draperstown) (Geological Survey of Northern Ireland, 1995), the rocks at Black Rock are included within the Tyrone Plutonic Group which is broadly equivalent to Hartley's Crushed Complex. The Tyrone Plutonic Complex surrounds and is in faulted contact with the high grade metamorphic inlier (Corvanaghan Formation) The Tyrone Plutonic Group forms part of the Tyrone Ophiolite Complex, interpreted as being a fragment of Ordovician island arc or back-arc oceanic crust (Hutton et al., 1985). These rocks form part of the Tyrone-Girvan Sub-Terrane of the Midland Valley Terrane as defined by Bluck et al. (1992 and can broadly be correlated with comparable ophiolitic rocks at Ballintrae in Scotland and Clew Bay in western Ireland.
| Enlander, I., Dempster, M. & Doughty, P., 2024. Black Rock, County Tyrone, site summary. [In] Earth Science Conservation Review. https://www.habitas.org.uk/escr/summary.php?item=580. Accessed on 2024-12-26 |
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