Earth Science Conservation Review
| Rosemount - site of local interest | Down |
| Site Type: | Quarry (disused) |
| Site Status: | local interest |
| Council area: | Ards Borough Council |
| Grid Reference: | J591675 |
| Google maps: | 54.5313,-5.54222 |
| Rocks | |
|---|---|
| Rock Age: | Silurian (Llandovery) |
| Rock Name: | Tullykevin Formation |
| Rock Type: | Greywacke, Mudstone, Siltstone |
| Interest | |
| Other interest: | bedding, cross-bedding, ripple marks, cleavage, load marks |
Description:
The Tullykevin Formation extends from Tullykevin townland southwest to Greyabbey. The disused quarries at Rosemount provide good exposures of the formation. The Tullykevin Formation is a predominantly argillaceous unit outcropping at the core of a northeast trending syncline which is overturned towards the northwest. Along its south-eastern limit, the Tullykevin Formation is apparently conformable with greywackes of the Strangford (Gala) Group whereas it appears to be in faulted contact with the Strangford Group to the northwest. These factors combine to make estimation of the thickness of the Tullykevin Formation difficult.
At Rosemount the Tullykevin Formation consists of hard bluish-grey fissile mudstone, soft black micaceous mudstone and laminated siltstone. A very strong closely spaced regional cleavage (S1) is parallel or subparallel to bedding resulting in a rock which is easily split and which, in the past, was used locally as roofing material. Interbedded with the mudstones and siltstones are a few horizons of greywacke, generally 0.1-0.2m thick but up to 2m thick. These coarser-grained sediments contain sedimentary structures such as load-marks, loaded ripples and cross-laminations which provide important indicators of younging direction in an otherwise monotonous argillaceous sequence. One greywacke unit has, at its base, a thin intraformational breccia with an erosion surface, which cuts down into underlying siltstones.
The total absence of fauna from the Tullykevin Formation makes dating the sequence difficult though it is probably of mid-late Llandovery age.
At Rosemount the Tullykevin Formation consists of hard bluish-grey fissile mudstone, soft black micaceous mudstone and laminated siltstone. A very strong closely spaced regional cleavage (S1) is parallel or subparallel to bedding resulting in a rock which is easily split and which, in the past, was used locally as roofing material. Interbedded with the mudstones and siltstones are a few horizons of greywacke, generally 0.1-0.2m thick but up to 2m thick. These coarser-grained sediments contain sedimentary structures such as load-marks, loaded ripples and cross-laminations which provide important indicators of younging direction in an otherwise monotonous argillaceous sequence. One greywacke unit has, at its base, a thin intraformational breccia with an erosion surface, which cuts down into underlying siltstones.
The total absence of fauna from the Tullykevin Formation makes dating the sequence difficult though it is probably of mid-late Llandovery age.
| Enlander, I., Dempster, M. & Doughty, P., 2024. Rosemount - site of local interest, County Down, site summary. [In] Earth Science Conservation Review. https://www.habitas.org.uk/escr/summary.php?item=750. Accessed on 2024-12-26 |
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