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Locally Important Geological and Geomorphological Sites

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Edgmond - Quarry (disused) - SJ 714 194

Interest:

Sedimentology/Stratigraphy

Stratigraphy:

Permo-Trias: Chester Pebble Beds. Sheet 139.


Date of Last Survey: 07/01/2002

This is a first rate large site which has many interesting features. The rock is essentially a coarse red sandstone, distinctly bright where the faces are fresh. Within it are scattered pebbles, mainly vein quartz and quartzite. At the base of the main north face are thick beds a metre or so in thickness. Above 2 m there is a marked change to cross-bedded units, very well displayed. These are mostly low-angle, 10-15 and multi-directional, indicating shifting currents. Within the cross beds the sandstone is finely laminated and contains more pebbles showing some alignment. The boundary at 2 m is very definite. The pebbles are sub-rounded to angular, maximum length being 70 mm. Because of recesses, it is possible to see the cross-beds in 3-D which is useful for working out palaeo-currents. At a height of about 5 m, at the top of the quarry face, the strata become more thinly bedded with horizontal partings. Both vertical and oblique joints are evident as are at least 3 faults with displacement of 40-50 mm. On the south side is an interesting irregular collapsed fault or joint where cross-beds have steeper dip. No evidence of mineralisation or slickensided surfaces were found. Slump structures and graded lamination can be identified in the sandstone. At the east end of the quarry are two major recesses at two levels. These appear to correspond with the presence of a dark red/brown fissile, shaly marl containing mica flakes and finely bedded with horizontal partings. At the higher horizon, the marl was up to 0.5 m thick.


Access:

A public footpath goes through and access to faces is excellent.

References:

No specific mention known. Site familiar to Mike Rayner for many years.

 

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