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Earth Science Conservation Review
| Milltown | Armagh, Tyrone |
| Site number: | 1201 | ||
| ESCC: | EO | ||
| Locality Type: | Stream section | Status: | ASSI |
| Grid Reference: | H804516 End(s) of linear site | ||
| Google maps: | 54.40709,-6.76181 | ||
| County: | Armagh, Tyrone | Council area: | Armagh City, Banbridge & Craigavon Borough Council |
| Period: | Triassic, Carboniferous | ||
| Stages: | Dinantian, Middle Triassic, Scythian | ||
| Lithostrat: | Derrycreevy Sandstone Formation, Milltown Conglomerate Formation, Sherwood Sandstone Group, Tyrone Group | ||
| Site Description | |
|---|---|
| Highlights: | |
The exposures at Milltown, County Armagh are the type localities for the Milltown Conglomerate Formation and the Derrycreevy Sandstone Formation. | |
| Introduction: | |
This site lies along the River Blackwater for 800m west from Milltown and is 1.25km SW of Benburb, Co. Tyrone. The Triassic sediments, comprising the Milltown Conglomerate Formation and the Derrycreevy Sandstone Formation of the Sherwood Sandstone Group overlie the fossiliferous marine limestones, shales, sandstones and mudstones of the Carboniferous Tyrone Group. Egan (1873) attributed the basal conglomerate to the Lower Permian. He described it as 'slight exposures of light purple sandstone, some of which passes to a hard fine breccia; this is overlain by thin bedded purple shales, all being calcareous'. He also described 'a fine brownish red brecciated conglomerate'. To the west, he assigned the sandstones to the Upper Mottled Sandstone (Bunter). Following the resurvey of the area, the newly published map (GSNI, 1985) gave a Triassic age for both formations. | |
| Description: | |
This is the type section for the Milltown Conglomerate Formation which occurs on the north bank of the River Blackwater, and also in its bed, opposite the mill factory at Milltown. Here the strata are about 12m thick. The conglomerates are grey or pink- stained, usually fine-grained and occur in beds up to 50cm thick separated by partings of friable, coarse-grained, red to purple sandstone up to 5cm thick. Pebble diameter is usually in the order of 1cm although some of the flatter limestone pieces may be up to 2-3cm in length. All the pebbles are well rounded with vein quartz the dominant type, although examples of chert, micrite limestone and fine-grained greywackes of Lower Palaeozoic age are common. The type section of the Derrycreevy Sandstone Formation is located on the north bank of the River Blackwater, between the mill factory at Milltown and the weir, 800m to the NW, in the townlands of Derrycreevy and Drumflugh. About 150m of sediment occur in the type section. The formation base is recognised by the rapid disappearance of conglomerates of the underlying Milltown Formation and the appearance of finer-grained sediments with a characteristic brick-red colour. The upper limit is not exposed in the area, but was probably represented by a passage zone of upward-fining sediments accompanied by the appearance of gypsum bands, which are assigned to the Mercia Mudstone Group. | |
| Importance: | |
The site is of national importance as the type section for the Triassic Milltown Conglomerate Formation and the Derrycreevy Sandstone Formation. The range of sedimentary structures enable environments of deposition of the Sherwood Sandstone Group to be determined. Also because of the importance of the group in hydrogeology and petroleum exploration, it is important that the site is conserved. | |
| Interpretation: | |
No fauna or flora have been recovered from these rocks and it is assumed, by analogy with modern environments, that the original sediments were deposited in desert conditions. The existence of temporary fluviatile conditions is indicated by the development of ripple-marked bedding surfaces with worm tracks. In contrast to the iron staining that produces the characteristic red colour of these rocks and is indicative of the oxidising nature of palaeo-desert conditions, thin bands of white or pale green sediment suggest that reducing conditions existed in temporary lakes. Small amounts of poorly preserved woody debris were recovered from these white sandstones during palynological analysis, but no spores or pollen. It seems likely that most organic material was selectively winnowed-out from these sediments by current action during their deposition. Rare examples of large scale cross-bedding up to 1m thick probably originated as aeolian deposits in the form of low sand dunes. The age of these rocks has been subject to debate. The Milltown Conglomerate Formation was previously interpreted as Lower Permian in age, but the most recent suggestion is that these are Triassic in age. | |
| Conclusions: | |
The sections are some of the best exposures in the Triassic conglomerates and sandstones in N. Ireland, and are some of the most westerly occurrences. The site should be conserved. Exposure varies depending on the water level in the River Blackwater. Access is either from the mill factory or via a track from the farm in Drumflugh townland. | |
| Notes: | |
For information on other Triassic sites see Key Site 1197 - Brown's Bay, Island Magee Key Site 1198 - Cloghfin Port, Island Magee Key Site 1199 - Collin Glen Key Site 1200 - Scrabo Hill - Triassic Key Site 1202 - Drapersfield Quarry Key Site 1203 - Lissan Water Key Site 1204 - Curraghlane. For general information on the Triassic System in N. Ireland see Key Site 1192 - The Triassic System in N. Ireland - Introduction. | |
| Keywords | |
|---|---|
| Rocks: | Conglomerate, Sand, Sandstone |
| Fossil Groups: | Trace fossil, Wood |
| Structures: | cross-bedding, ripple marks |
| Relations: | Aeolian sediment, Fluvial sediments, Lacustrine sediments |
| Paleoenv: | desert |
| Measurements | |||||
|---|---|---|---|---|---|
| Length: | 800 m | Width: | Height: | ||
| Depth: | Area: | ||||
| Access | |
|---|---|
| Approach: | West of Milltown and 1.25km SW of Benburb. |
| References (1) | |||
|---|---|---|---|
| Egan, F.W., 1873. Explanatory memoir to accompany Sheet 47 of the maps of the Geological Survey of Ireland, including the country around Armagh. Memoirs of the Geological Survey of Ireland, Dublin. | |||
| Map(s): | GSNI (1985) 1:50,000 Geological Sheet 49 (Armagh). | ||
| Record type: | ESCR report | ||
| Entered by: | E M Porter | ||
| Enlander, I., Dempster, M. & Doughty, P., 2026. Milltown, County Armagh, Tyrone, site details. [In] Earth Science Conservation Review. https://www.habitas.org.uk/escr/site.php?item=1201. Accessed on 2026-11-06. |
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