Earth Science Conservation Review
| Bonnety Bush, Altihaskey | Londonderry |
| Site Type: | Inland exposure |
| Site Status: | ESCR |
| Grid Reference: | H726888 |
| Google maps: | 54.74237,-6.87272 |
| Rocks | |
|---|---|
| Rock Age: | Ordovician |
| Rock Name: | Tyrone Volcanic Group |
| Rock Type: | Chert, Jasper |
| Interest | |
| Other interest: | Caledonian |
Introduction:
Bonnety Bush is located at Altihaskey in the Townland of Tullybrick. The site comprises several isolated outcrops and boulders which form a low rise on the otherwise flat glacial-outwash plain south of Lough Fea. Access is via a track which runs southwest from [27380 38930] on the Tullybrick Road and then across open moorland, a total distance of about 1km. Alternative access is via a farm track south from the Davagh Road.
On Portlock's early geological map of the area, (1843) the rocks in the vicinity of Bonnety Bush were represented as "mica schists" and grouped with the metamorphic rocks of the Sperrin Mountains "of hornblendic type". In the text, Portlock referred to "micaceous iron ore at Tullybrick ... disposed on iron flint and quartz; in the latter case in veins in the mica-slate, associated with iron jasper".
The first edition of the one inch to one mile scale geological map (Sheet 26, Draperstown, Geological Survey of Ireland, 1882) represented rocks at Bonnety Bush as "chloritic, Talcose & Micaceous Schists of Lower Silurian age" and did not differentiate them from the mica schists of the Sperrin Mountains to the north of the site.
Hartley (1933) published the first detailed lithological map and description of the central Tyrone Ordovician volcanicplutonic terrane. He included the rocks at Bonnety Bush in a division which he referred to as the "Phyllites and Chloritic Schists of Tullybrick" part of the volcanic tuff and lava (volcanic) series into which they grade. Hartley also noted that elsewhere in the vicinity the ferruginous chert was found in association with haematite for example in Glenscallip Burn and on the south side of Slieve Gallion. On the second edition (1:50,000 scale) of the geological map (Sheet 26, Draperstown, Geological Survey of Northern Ireland, 1995), the rocks at Bonnety Bush are included within the Tyrone Volcanic Group.
The Tyrone Volcanic Group is an arc-volcanic type geological sequence, which formed along the Laurentian foreland at the northern margin of the Iapetus Ocean during closure of the Iapetus Ocean during Ordovician times. In a regional tectono-stratigraphic context, the Tyrone Volcanic Group forms part of the Tyrone-Girvan Sub-Terrane of the Midland Valley Terrane as designated by Bluck et al. (1992).
On Portlock's early geological map of the area, (1843) the rocks in the vicinity of Bonnety Bush were represented as "mica schists" and grouped with the metamorphic rocks of the Sperrin Mountains "of hornblendic type". In the text, Portlock referred to "micaceous iron ore at Tullybrick ... disposed on iron flint and quartz; in the latter case in veins in the mica-slate, associated with iron jasper".
The first edition of the one inch to one mile scale geological map (Sheet 26, Draperstown, Geological Survey of Ireland, 1882) represented rocks at Bonnety Bush as "chloritic, Talcose & Micaceous Schists of Lower Silurian age" and did not differentiate them from the mica schists of the Sperrin Mountains to the north of the site.
Hartley (1933) published the first detailed lithological map and description of the central Tyrone Ordovician volcanicplutonic terrane. He included the rocks at Bonnety Bush in a division which he referred to as the "Phyllites and Chloritic Schists of Tullybrick" part of the volcanic tuff and lava (volcanic) series into which they grade. Hartley also noted that elsewhere in the vicinity the ferruginous chert was found in association with haematite for example in Glenscallip Burn and on the south side of Slieve Gallion. On the second edition (1:50,000 scale) of the geological map (Sheet 26, Draperstown, Geological Survey of Northern Ireland, 1995), the rocks at Bonnety Bush are included within the Tyrone Volcanic Group.
The Tyrone Volcanic Group is an arc-volcanic type geological sequence, which formed along the Laurentian foreland at the northern margin of the Iapetus Ocean during closure of the Iapetus Ocean during Ordovician times. In a regional tectono-stratigraphic context, the Tyrone Volcanic Group forms part of the Tyrone-Girvan Sub-Terrane of the Midland Valley Terrane as designated by Bluck et al. (1992).
| Enlander, I., Dempster, M. & Doughty, P., 2024. Bonnety Bush, Altihaskey, County Londonderry, site summary. [In] Earth Science Conservation Review. https://www.habitas.org.uk/escr/summary.php?item=586. Accessed on 2024-12-26 |
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