Earth Science Conservation Review
| Craiganawork, Pomeroy | Tyrone |
| Site Type: | Inland exposure |
| Site Status: | ESCR |
| Grid Reference: | H26773758 |
| Google maps: | 54.28608,-7.59001 |
| Rocks | |
|---|---|
| Rock Age: | Devonian, Ordovician |
| Rock Name: | Old Red Sandstone, Pomeroy Granite, Tyrone Plutonic Group |
| Rock Type: | Granite, Sandstone |
| Interest | |
| Other interest: | Caledonian, pluton, Intrusion |
Introduction:
The Craiganawork site is located ~4km northwest of Pomeroy, County Tyrone.
The first edition of the Ballygawley (Sheet 34) one-inch to the mile geological map (Geological Survey of Ireland, 1913 Edition) shows an intrusive granite body intruded into hornblendic and pyroxenic country rocks northwest of Pomeroy. The Sheet 34 memoir (Nolan, 1878) describes an extensive tract of granite, including that exposed around Beragh and Carrickmore. The granite was considered to be of Old Red Sandstone age; an age based on contact relationships and apparent thermal metamorphism.
The second edition off Sheet 34 (renamed Pomeroy) represented the Pomeroy Granite as an elongate pluton aligned parallel to the dominant Caledonian strike (Geological Survey of Northern Ireland, 1979). The pluton was emplaced into gabbros and dolerites of the Tyrone Basic Plutonic Complex; a relationship demonstrated by the occurrence of a narrow thermal aureole. The Beragh and Carrickmore plutons are shown intruding into gneissose rocks of the Corvanaghan Formation. This relationship is shared by the Slieve Gallion intrusion which lies further to the northeast in south Londonderry. The summary of the geological history of the Pomeroy Sheet relates the Pomeroy pluton to the intrusions at Beragh and Carrickmore and suggests that the granites pre-date the Tyrone Volcanic Group (Ordovician). Although research on these granites is limited, the current belief is that these intrusions most closely resemble the younger Caledonian granites (late Ordovician or Silurian age). The contact relationship of the granite with Lower, Middle and Upper Devonian sequences that overly the granites, seems to support this younger Caledonian age for the suite. This is in contrast with the early Caledonian age proposed for the Craigballyharky tonalite (Key Site 590 - Craigballyharky and Craigbardahessiagh) and the porphyritic dacite at Cushendun (Key Site 594 - Cushendun). It should however be noted, that these granites are not seen to intrude Ordovician sediments so could be of a similar age to Craigballyharky tonalite. It is hoped that radiometric age dating studies of the Pomeroy Granite (work in progress) will shed light on the age and contact relationships of the granite.
The first edition of the Ballygawley (Sheet 34) one-inch to the mile geological map (Geological Survey of Ireland, 1913 Edition) shows an intrusive granite body intruded into hornblendic and pyroxenic country rocks northwest of Pomeroy. The Sheet 34 memoir (Nolan, 1878) describes an extensive tract of granite, including that exposed around Beragh and Carrickmore. The granite was considered to be of Old Red Sandstone age; an age based on contact relationships and apparent thermal metamorphism.
The second edition off Sheet 34 (renamed Pomeroy) represented the Pomeroy Granite as an elongate pluton aligned parallel to the dominant Caledonian strike (Geological Survey of Northern Ireland, 1979). The pluton was emplaced into gabbros and dolerites of the Tyrone Basic Plutonic Complex; a relationship demonstrated by the occurrence of a narrow thermal aureole. The Beragh and Carrickmore plutons are shown intruding into gneissose rocks of the Corvanaghan Formation. This relationship is shared by the Slieve Gallion intrusion which lies further to the northeast in south Londonderry. The summary of the geological history of the Pomeroy Sheet relates the Pomeroy pluton to the intrusions at Beragh and Carrickmore and suggests that the granites pre-date the Tyrone Volcanic Group (Ordovician). Although research on these granites is limited, the current belief is that these intrusions most closely resemble the younger Caledonian granites (late Ordovician or Silurian age). The contact relationship of the granite with Lower, Middle and Upper Devonian sequences that overly the granites, seems to support this younger Caledonian age for the suite. This is in contrast with the early Caledonian age proposed for the Craigballyharky tonalite (Key Site 590 - Craigballyharky and Craigbardahessiagh) and the porphyritic dacite at Cushendun (Key Site 594 - Cushendun). It should however be noted, that these granites are not seen to intrude Ordovician sediments so could be of a similar age to Craigballyharky tonalite. It is hoped that radiometric age dating studies of the Pomeroy Granite (work in progress) will shed light on the age and contact relationships of the granite.
| Enlander, I., Dempster, M. & Doughty, P., 2024. Craiganawork, Pomeroy, County Tyrone, site summary. [In] Earth Science Conservation Review. https://www.habitas.org.uk/escr/summary.php?item=591. Accessed on 2024-12-26 |
| Previous Site | Next Site |