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Spincha Burn, Cluntygeeragh TownlandLondonderry
Headwaters of Spincha Burn, Cluntygeeragh Townland, Co.Londonderry, exposing Iniscarn Sandstone Formation.
Summary Full report
Site Type: Stream section
Site Status: PASSI
District: Limavady Borough Council
Grid Reference: C72980316
Rocks
Rock Age: Carboniferous (Tournasian)
Rock Name: Iniscarn Sandstone Formation, Tyrone Group
Rock Type: Arkose, Conglomerate
Interest
Other interest: No data, Fluvial sediments, alluvial fan

Summary of site:

Spincha Burn is the most westerly tributary of the dendritic stream system draining the northern slopes of White Mountain. The system occupies the amphitheatre that dominates the landscape to the south of the westerly descent from the Glenshane Pass.

The Carboniferous outcrop, which is the subject of this account, forms a 5 m high waterfall which exposes massive, feebly-bedded cobble and boulder conglomerates. The individual cobbles, of white vein quartz and quartzite, have little or no matrix supporting them and they rarely exceed 7 cm in diameter but there is the occasional boulder up to 40 cm long. The lip of the waterfall is a bed of pale, purple-red coarse sandstone 45 cm thick inclined 10 degrees to the south east. The actual base of the formation is not exposed in the stream bed but can only be a matter of metres below the lowest exposure. It rests on an unconformity, a considerable break in time, on the ancient Precambrian Dalradian rocks. At the time of preparation of the Full Report for this site it was considered to be the base of the Iniscarne Sandstone Formation, part of the Tyrone Group of the early Carboniferous. It is now known to be older and has been given its own formation name. It is now the Spincha Burn Conglomerate Formation of the Roe Valley Group and is the earliest, or among the earliest, Carboniferous rocks of Northern Ireland. It is dated to the Courceyan stage, slightly over 350 million years old. The Spincha Burn rocks were formed on the southern shores of a continent called Laurentia (containing parts of what are now North America, Greenland and northern Europe) as the seas began to invade a landscape carved into ancient Dalradian rocks. Laurentia straddled the equator of the time and the British Isles area was on the southern side with equatorial climatic conditions. The isolation of this site in difficult terrain offers useful protection.


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