Geological significance of dolyhir and nash scar limestone

This is not to say that Wales has no classic minerals, but is perhaps a reflection of collecting habits and the preference for large, brightly coloured crystals. Wales has a long history of mining dating back to, at least, the Bronze Age, but, unlike some other regions, there does not appear to have been a desire by miners to extract mineral specimens for sale.

Geological significance of dolyhir and nash scar limestone

Click here to request data March 6th, Exposed units: The quarry exposes a good section of the mature calcrete that characterises the unit. The unit has ahigh clay content in the bottom 2.

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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. There are no key references for this site.

Terminology Slickensides — A smoothly polished surface caused by frictional movement between rocks along a fault plane. Upper Ludlow Shales The quarry faces extend over 60m from east to west and expose an almost continuous section across the Silurian Ludlow — Pridoli boundary.

In the eastern part of the quarry, the uppermost beds of the Upper Ludlow Shales are exposed. These beds, also known as the Whitcliffe Beds, are predominantly calcareous siltstones with occasional limestone horizons.

At the very top, the siltstones give way to 6m of thinly bedded, micaceous, current rippled sandstones with shale partings. About three quarters of the way along the face, the transition from marine to non-marine sedimentation is shown by a change from the siltstone with marine fossils to the river sediments of the Downton Castle Formation.

Geological significance of dolyhir and nash scar limestone

In the western part of the quarry, a small section through the Downton Castle Sandstone is exposed, overlying the weathered surface of the Upper Ludlow Shales. The rocks are fine-grained, buff coloured and comprise quartz, muscovite and limonite.

They are thought to have been deposited in a fluviatile environment.

GB3D Type Fossils | High resolution photographs and digital models of British type fossils

The Whitcliffe Beds here contain an abundant fauna including brachiopods Protochonetes and Camarotoechia as well as mollusca. The Downtonian contains only the brachiopod Lingula which may occur in the sandstone bands and occasional plant material.

Click here to request data March 6th, Exposed Units: The rock units at this locality are grey-green limestones that are slightly nodular at the base of the outcrop. Above this zone of nodular limestone, the beds are thinly layered 20cm width and are made of a fine grained material which is possibly bentonitic in origin.

This small face contains beds with abundant brachiopod fossils, a species of bivalve that may be related to the pectinoid family.

The core of the fold could lie at the base of the exposure. There is also a regular series of radiating fractures related to the fold axis that would correspond to coeval cleavage plane development. The structures preserved at this locality are important in understanding the 3D geometry of rocks in the surrounding area, as the site forms part of a larger fold structure called the Ledbury Anticlinorium.

Terminology Slickenside - a smoothly polished surface caused by frictional movement between rocks along the two sides of a fault, which is normally striated in the direction of movement. A diagram showing the various features associated with folding in sedimentary rocks. Aymestry Limestone Conservation Status: Both of the quarries display fine examples of the Aymestry Limestone Formation.

The quarries are large, with the northern quarry being long and narrow at 40m long and 8m deep, with m high rock faces. The southern quarry is 30m wide, 40m deep and has rock face that reaches m.

Both quarries display bedded nodular clay-rich limestones and calcareous calcium carbonate rich siltstones that are typical of Aymestry Limestone Formation exposures. The nodules are more pronounced in the northern quarry, where weathering has eroded away much of the lime cement, which allows for the shapes of the nodules to be seen more clearly.

Both quarries also contain thin layers cm thick of calcareous siltstones. These thin siltstones are separated by approximately 2m of the nodular limestones.

Due to their soft compositions they have weathered preferentially in comparison to the harder limestones and therefore can be easily identified.

This dip is attributed to the fact that the rocks in this area are sitting on the southern limb of large anticlinal fold.These include the Buildwas Formation (Wenlock Edge, Shropshire), Woolhope Limestone (Woolhope and May Hill inliers and Malvern Hills of Herefordshire, Gloucestershire and Worcestershire), Barr Limestone (Walsall, West Midlands), lower Brinkmarsh Beds (Tortworth, Gloucestershire) and Dolyhir/Nash Scar Limestone (Old Radnor, Powys).

Sutton, M.D., Briggs, D.E.G., Siveter, David J. and Siveter, Derek J. The geological significance of the Dolyhir and Nash Scar limestone (Silurian) of the Welsh Borderland.

Tarmac Papers 4, Briggs, D.E.G., Evershed, R.P. and Lockheart, M.J. The biomolecular paleontology of continental fossils. These include the Buildwas Formation (Wenlock Edge, Shropshire), Woolhope Limestone (Woolhope and May Hill inliers and Malvern Hills of Herefordshire, Gloucestershire and Worcestershire), Barr Limestone (Walsall, West Midlands), lower Brinkmarsh Beds (Tortworth, Gloucestershire) and Dolyhir/Nash Scar Limestone (Old Radnor, Powys).

Geological Significance of Dolyhir and Nash Scar Limestone The geological significance of the Dolyhir and Nash Scar limestone (Silurian) of the Welsh Borderland Introduction and History Ther regions of Old Radnor and Presteigne (Fig. Distribution of the Geological Conservation Review sites for the Wenlock Series, set against the palaeogeographical elements of Silurian Britain.

GCRv19c04f (in the distance and the centre of the photo) in the Basement Beds of the Much Wenlock Limestone Formation, beneath which is the uppermost part of the Coalbrookdale Formation. The present day operations encompass the former Yat-Hill Quarry and numerous unnamed smaller quarries that worked the Wenlock Age, Dolyhir Limestone in the northern corner of the modern workings.

Wenlock stratigraphy and palaeogeography of Wales and the Welsh Borderland - ScienceDirect