GC2R793 Q is for Quarry (Traditional Cache) in Ulster, Ireland created by fastfox

This cache has been archived.

Cuilcagh: The cache owner is not responding to issues with this geocache, so I must regretfully archive it.

Please note that if geocaches are archived by a reviewer or Geocaching HQ for lack of maintenance, they are not eligible for unarchival.

Cuilcagh - Community Volunteer Reviewer for Geocaching HQ (Ireland)

GC2R793 ▼

A cache by fastfox Message this owner

Hidden : 3/30/2011

Difficulty:

Terrain:

Size: Size: micro (micro)

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Geocache Description:

Craig Hill Quarry is situated on the County Antrim Basalt Plateau, on the northeast side of Ballyclare. The basalt within it forms part of the 'Lower Basalt Formation'. The quarry is no longer in use and land to the west is currently being redeveloped for housing. There is a large lake in the basin of the quarry. The cache ( replaced October 20 )is a small magnetic tube containing a log and a pencil. Please remove and replace carefully. Parking is available within 20m.

There is no public access to the actual quarry but the cache which is placed outside the site provides a location giving very good views of the lake and disused quarry. Geological information The Antrim Lava Group (Palaeogene) is subdivided into three formations: the Lower Basalt Formation, the Interbasaltic Formation and the Upper Basalt Formation. By far the best exposures of the Lower Basalt Formation in the Ballyclare area are to be found at Craig Hill Quarry The two flows seen here display a number of unusual features. The upper flow was the principal one worked. It is at least 18m thick and generally massive and coarse-grained. A strong platy jointing with steeply dipping joint-planes is developed on parts of the north and south faces of the eastern section of the quarry. On the north face joints sometimes curve round to horizontal, but are thought to be cooling joints rather than part of a magmatic roll. On the south face of the quarry the joints pass upwards into blocky basalt and are, therefore, not due to faulting. The top of the lower flow appears at the foot of the face due to a fault downthrowing to the west. The upper flow is markedly finer grained for at least 1m above the base, but is not sharply demarcated from the highly vesicular basalt beneath. The upper 4m of the lower flow is highly vesicular with an irregular upper surface. A strong banding is due to variations in the size and shape of the vesicles. Sometimes the banding dips steeply. Generally the vesicles are rounded or almond-shaped and contain chiefly chabazite, brown or clear calcite and some fibrous zeolite minerals, probably thomsonite. A few vesicles contain levyne with an overgrowth of calcite. An undulating grey-brown band of tuffisite occurs parallel to and about 1m from the top of the lower flow. The band is up to 2cm thick and can be traced for at least 200m. In places it is merely rotten basalt and zeolite but often it is finely banded with scattered crystals of olivine and glass fragments. Below the upper 4m of vesicular basalt are at least 8m of fairly coarse basalt with vesicular bands and patches up to 1m thick. Importance: The site is of scientific value as it provides by far the best exposures of the Lower Basalt Formation in the Ballyclare area and the quarry preserves a number of unusual features within the basalt. The site has some educational significance for the third level education sector and offers opportunities for examination of a number of unusual features within the Lower Basalt Formation. A detailed mineral report can be found at: www.mindat.org/locdetailed-186325.html

Additional Hints (Decrypt)

Abj ng ybj yriry.

Decryption Key

A|B|C|D|E|F|G|H|I|J|K|L|M
-------------------------
N|O|P|Q|R|S|T|U|V|W|X|Y|Z

(letter above equals below, and vice versa)