NS3778 : Cornstone outcrop

near to Renton, West Dunbartonshire, Great Britain

Cornstone outcrop
Cornstone outcrop
This outcrop is very similar in appearance to one that is to be found on Dumbarton Muir (NS4480 : Cornstone outcrop); in both cases, the grikes (water-worn fissures) are a prominent feature.

See NS3778 : Cornstone outcrop for another view, and for comments on its relation to the underlying cornstone deposits.

This is just one of several large outcrops that can be seen in this area along a line running from east to west (many smaller outcrops and individual boulders also occur on that line). At the western extremity, there is a former cornstone workings (NS3678 : Former cornstone workings on Carman Muir); see that item for a description of the nature of cornstone, and its use.

Like other cornstone outcrops in this area, it is host to a particular lime-loving species of spleenwort (a fern); see NS3778 : Maidenhair spleenwort (Asplenium trichomanes). Lichen species that I encountered here included Ochrolechia tartarea ( LinkExternal link ), which was growing here on mosses, rather than directly on the rock surface.

The background is largely obscured by haze, but the escarpment of the Kilpatrick Hills appears on the skyline, and the housing scheme that just barely visible at the foot of the hills is Bellsmyre.
Carman Muir: outcrops and old quarry pits
See LinkExternal link for an annotated satellite view on which various features of geological interest (as well as traces of associated industries and other antiquities) are marked, as described below.

The topography of the parts of Carman Muir to the south of Cardross Road is determined to a large extent by cornstone deposits, which outcrop in places. Cornstone is an impure granular limestone, a fossil soil. Old quarry pits (probably worked before the nineteenth century) and possible test pits can be seen along the lines of these deposits; they are indicated by light blue marker pins on the annotated satellite view, and the cornstone outcrops are marked by orange pins.

This area, lying to the south of Cardross Road, exemplifies what the British Geological Survey refers to as the Kinnesswood Formation (see LinkExternal link at the BGS website for more information); this formation contains cornstone deposits.

Beside and to the north of Cardross Road are outcrops of sandstone rather than cornstone. The sandstone is best seen along a line of outcrops and pits beside the road (these are indicated by reddish marker pins on the annotated satellite view). Another prominent example lies at the ENE end of that line: a large disused red sandstone quarry, the old Fairy Knowe Quarry (later known as Carman Quarry) LinkExternal link at NS36967900. This area beside and to the north of the road exemplifies the Stockiemuir Sandstone Formation (see LinkExternal link at the BGS website for further details).

Both north and south of the road, the strata in this area generally dip at an angle of from 10 to 20 from the horizontal, descending towards the SSE; the Stockiemuir Sandstone Formation that is exposed beside and to the north of the road underlies the cornstone-containing Kinnesswood Formation to the south of the road.

The annotated satellite view also includes markers for various antiquities in the area:

● Ancient cairns: LinkExternal link
● Hut circle: LinkExternal link
● Carman (house): LinkExternal link
● Carman (enclosure): LinkExternal link
● Carman (field system): LinkExternal link
Creative Commons Licence [Some Rights Reserved]   © Copyright Lairich Rig and licensed for reuse under this Creative Commons Licence.
year taken
2009
1:50,000 Modern Day Landranger(TM) Map © Crown Copyright
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1:50,000 Modern Day Landranger(TM) Map © Crown Copyright
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NS3778, 170 images   (more nearby )
Photographer
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Image classification?
Supplemental image
Date Taken
Wednesday, 15 April, 2009   (more nearby)
Submitted
Wednesday, 15 April, 2009
Geographical Context
Geological interest 
Category
Rock outcrops   (more nearby)
Subject Location
OSGB36: geotagged! NS 3752 7838 [10m precision]
WGS84: 55:58.2504N 4:36.3039W
Photographer Location
OSGB36: geotagged! NS 3752 7838
View Direction
East-southeast (about 112 degrees)
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Cornstone  Limestone 

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