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Earth Science Conservation Review
| Ballyharry - site of local interest | Down |
| Site number: | 702 | ||
| Locality Type: | Railway cutting | Status: | local interest |
| Grid Reference: | J501753,J501754 End(s) of linear site | ||
| Google maps: | 54.60405,-5.67714 | ||
| County: | Down | Council area: | Ards & North Down Borough Council |
| Period: | Silurian, Ordovician | ||
| Stages: | Ashgill, Caradoc, Lower Silurian | ||
| Lithostrat: | Strangford Group, Drumhirk Formation, Lessans Formation | ||
| Site Description | |
|---|---|
| Highlights: | |
The old railway cutting at Ballyharry exposes outcrops of the Upper Ordovician Lessans Formation and the succeeding Lower Silurian Drumhirk Formation of the Strangford Group. The Lessans Formation section exposes blue-black mudstones overlain by grey, blocky, silty mudstones. The section is fossiliferous and contains Pleurograptus linearis Zone graptolites, indicating an age that spans the Caradoc-Ashgill boundary. | |
| Description: | |
The rocks exposed at the disused railway cutting at Ballyharry in northeast Newtownards form part of the Upper Ordovician Lessans Formation and the succeeding Lower Silurian Drumhirk Formation of the Strangford Group. Exposure of the Lessans Formation is restricted to isolated inliers which are usually fault-bounded and contain black graptolitic mudstones, grey barren mudstones and siltstones. The formation ranges in age from Llandeilo to Caradoc with the Ballyharry section exposing rocks towards the younger part of this range. At Ballyharry the Lessans Formation consists of blue-black mudstones, some finely laminated and slaty, overlain by grey, blocky, silty mudstones. The dark mudstones are fossiliferous and during the Geological Survey’s resurvey of the area during the 1970’s the following graptolite assemblage was collected: ?Arachniograptus sp. Climacograptid {with basal spines} Climactograptus cf. tubuliferus Lapworth Glyptograptus sp. ?Lasiograptus sp. Leptograptus aff. macer Elles and Wood Orthograptus amplexicaulis (Hall) cf. abbreviatus Elles and Wood This fauna indicates an assemblage in the Pleurograptus linearis Zone that spans the Caradoc-Ashgill boundary. The dark mudstones also contain a thin discontinuous buff coloured claystone probably representing a volcanic ash fall. These argillaceous beds are succeeded, apparently conformably, by turbidite sandstones which contain mostly acid and intermediate volcanic and plutonic rock fragments together with subordinate basic volcanic and metasedimentary clasts. These turbidite sandstones are included in the Lessans Formation and appear to pass conformably up into the Drumhirk Formation, which is taken here as the base of the Strangford Group. | |
| Importance: | |
The site is of scientific significance because of the good exposure of the Lessans Formation and the rich fauna that has been collected from it. This fauna indicates an assemblage in the Pleurograptus linearis Zone that spans the Caradoc-Ashgill boundary. | |
| Keywords | |
|---|---|
| Rocks: | Mudstone, Sandstone, Turbidite |
| Fossil Groups: | Graptolite |
| Fossil List: | Arachniograptus sp., Climactograptus cf. tubuliferus Lapworth, Glyptograptus sp., Lasiograptus sp., Leptograptus aff. macer Elles and Wood, Orthograptus amplexicaulis Hall |
| Access | |
|---|---|
| Approach: | Old railway cutting in northeast Newtownards. |
| Uses | |
| Educ. Level: | The site is of limited educational value. |
| Record type: | SLNCI Report | ||
| Entered by: | E M Porter | ||
| Last updated: | 09/10/03 | ||
| Enlander, I., Dempster, M. & Doughty, P., 2026. Ballyharry - site of local interest, County Down, site details. [In] Earth Science Conservation Review. https://www.habitas.org.uk/escr/site.php?item=702. Accessed on 2026-11-05. |
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