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Blackbush Farm

Exposed units: Bishop’s Frome Limestone, Raglan Mudstone

This L-shaped quarry gives the best exposures of the Bishop’s Frome Limestone in the area. The quarry exposes a good section of the mature calcrete that characterises the unit.

The Bishop’s Frome Limestone here comprises blue-red nodular limestones with pale red and cream-coloured solution channels. The unit has ahigh clay content in the bottom 2.5m of the unit but grades into a more pure limestone towards the top.   The silage clamp on the west side of the quarry contains a fault plane with well-developed slickensides, suggestive of fault activity with downwards movement to east, although the extent of displacement is unknown. One part of the quarry exposes a small Quaternary U-shaped drainage channel that is seen to cut down into the Bishop’s Frome Limestone.

There are no key references for this site.

Terminology

Slickensides – A smoothly polished surface caused by frictional movement between rocks along a fault plane.

Photos

Red-coloured, blocky calcrete of the Bishop’s From Limestone. The red staining is due to the presence of oxidised iron in the rock, indicating the unit’s formation in an arid, well-oxygenated environment.

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