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Earth Science Conservation Review
| Straduff Quarry - Structural | Tyrone |
| Site number: | 658 | ||
| Locality Type: | Quarry (disused), Quarry (working) | Status: | ASSI |
| Grid Reference: | H343666 Centroid | ||
| Google maps: | 54.54703,-7.46996 | ||
| County: | Tyrone | Council area: | Fermanagh & Omagh District Council |
| Period: | Carboniferous | ||
| Stages: | Westphalian B | ||
| Lithostrat: | Drumlish Conglomerate Formation, Slievebane Group | ||
| Site Description | |
|---|---|
| Introduction: | |
Straduff Quarry is located on the southern side of the B4 road between Omagh and Kesh, about 7km east of Lack (Fig. 29). The quarry operates only intermittently. Points of structural interest within the quarry include vertical bedding, which helps constrain Variscan tectonic upheavals locally to post-Westphalian B times. The presence of a thick conglomerate unit is also taken as evidence of substantial syn-depositional subsidence accommodated along faults during the Variscan. | |
| Description: | |
Straduff Quarry contains cross-dip exposure of about 70m of massive, virtually unbedded conglomerate. The conglomerates are pebble to cobble grade, clast to matrix supported rocks belonging to the lower level of the Drumlish Formation (Slievebane Group, Westphalian B, Carboniferous). Despite the overall massive nature of the outcrop, bedding is clearly defined in the east face of the quarry where thin layers of hard, purple-grey, fine-grained calcareous sandstone, siltstone and red-purple shale are interbedded with the conglomerate. These strata are near vertical and young towards the south. The presence of this thick and consistently coarse suite of conglomerates and sandstones within the succession is evidence that throughout the period of sedimentation, there was a persistent topographic contrast maintained between the sediment source area and the alluvial fan depositional environment. This contrast was maintained by syn-depositional movement along faults at the basin margin. Straduff Quarry lies just 300m south of the trace of the Omagh Fault, a late Caledonian thrust fault known to have been reactivated locally during Variscan times. Movements on these faults are believed to have been precisely contemporaneous with a period of dextral transpression in the Maritime Provinces of eastern Canada and the propagation of rift basins in Greenland and the Arctic region (Mitchell, 1995). | |
| 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 250 - Straduff Quarry [Carboniferous Stratigraphic block]. | |
| Keywords | |
|---|---|
| Rocks: | Conglomerate, Sandstone, Shale, Siltstone |
| Structures: | bedding |
| Uses | |
|---|---|
| Uses: | Intermittently actice quarry. |
| 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. Straduff Quarry - Structural, County Tyrone, site details. [In] Earth Science Conservation Review. https://www.habitas.org.uk/escr/site.php?item=658. Accessed on 2026-11-08. |
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