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Cushendun - Cave House (south of)Antrim
Interbedded conglomerates and sandstones at the top of the Cushendun Formation, south of Cave House, Cushendun, Co.Antrim.
Summary Full report
Site Type: Coastal section
Site Status: PASSI
District: Moyle District Council
Grid Reference: D25373232
Rocks
Rock Age: Devonian (Lower Devonian)
Rock Name: Cross Slieve Group, Cushendun Conglomerate
Rock Type: Conglomerate, Mudstone, Sand, Sandstone
Interest
Other interest: cross-bedding, dessication cracks, No Data

Summary of site:

This locality, 150m south of Cave House, shows the transition between the lower and upper units of the Cushendun Formation (part of the Devonian Cross Slieve Group). The lower unit is mainly massive conglomerates (thick pebble and cobble beds) with some sandstones and thin mudstones. The upper unit is largely coarse sandstones with thin conglomerates. The transition is composed of conglomerates of quartz cobbles, several metres thick, standing on sandstone. The conglomerates appear to erode the upper surface of the sandstone which contains cross bedding. Within the sandstone are discontinuous, thin layers of green mudstone which are curled, concave upwards, into plates of mud defined by polygonal cracks that formed in the intense and desiccating desert heat.

The rocks were formed on a fan of coarse material washed out of an upland desert wadi by violent flash flooding. Despite the upland desert environment, water (in the form of rare torrential downpours) is the dominant shaper of landforms in this kind of terrain. Green mudstones have yielded microscopic spores in other Devonian rocks but here they are sterile, so there is no incontrovertible evidence of their supposed age. This is a coastal cliff and beach locality with no threats except from marine erosion.


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