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Earth Science Conservation Review
| Prehen Quarry - Structural | Londonderry |
| Site number: | 644 | ||
| Locality Type: | Quarry (disused) | Status: | ESCR |
| Grid Reference: | C423147 Centroid | ||
| Google maps: | 54.97847,-7.33934 | ||
| County: | Londonderry | Council area: | Derry City & Strabane District Council |
| Period: | Precambrian | ||
| Stages: | Dalradian | ||
| Lithostrat: | Londonderry Formation | ||
| Site Description | |
|---|---|
| Introduction: | |
This site is a disused and partially overgrown quarry at Prehen on the right bank of the River Foyle approximately 2km SSW of the centre of Londonderry (Fig. 10). The quarry is surrounded by recent housing development and access is via a path through woodland at the northern end of Prehen Park. The site contains turbidite facies rocks, which are relatively weakly deformed and metamorphosed under lower greenschist facies conditions. There are many excellent examples of cleavage/bedding relationships and preserved sedimentary structures. | |
| Description: | |
This disused quarry contains excellent examples of cleavage/bedding relationships in turbidite facies rocks belonging to the Londonderry Formation (Upper Dalradian). The locality is on the NW-facing southern limb of the Lough Foyle Syncline in an area of comparatively low tectonic strain. The dominant cleavage (S2) is broadly coplanar with an earlier S1 surface, and dips northwards at a consistently higher angle than bedding (S0). At Prehen, the regional metamorphism, which accompanied the deformation, was relatively low-grade. The common occurrence of quartz-chlorite-epidote assemblages in these rocks is consistent with metamorphism having taken place in the quartz-albite-muscovite-chlorite subfacies of the Greenschist Facies. | |
| Notes: | |
For general information on the Structural Geology of Northern Ireland, directions to other Structural Geology sites and an extensive reference list see Key Site 641 - Introduction to the Structural Geology of N. Ireland. See also Key Site 153 - Prehen Quarry [Precambrian Stratigraphic block]. | |
| Keywords | |
|---|---|
| Minerals: | Chlorite, Epidote, Quartz |
| Rocks: | Turbidite |
| Structures: | bedding, cleavage |
| Access | |
|---|---|
| Approach: | Access is via a path through woodland at the northern end of Prehen Park. |
| Record type: | ESCR report | Recorded by: | T.P. Johnston |
| Entered by: | E M Porter | ||
| Last updated: | 23/09/03 | ||
| Enlander, I., Dempster, M. & Doughty, P., 2026. Prehen Quarry - Structural, County Londonderry, site details. [In] Earth Science Conservation Review. https://www.habitas.org.uk/escr/site.php?item=644. Accessed on 2026-11-08. |
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