Editing Cheviot — early Devonian volcanic rocks, granite and basement - an excursion

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Walk along the road to Langleeford, then the track on the north side of the burn.
 
Walk along the road to Langleeford, then the track on the north side of the burn.
  
==== Locality 8 [NT 9450 2168] ====
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==== Locality 8 [NT 9450 2168] ====
  
Near the edge of the wood on the north of the track is the first exposure of granite in the burn. It is pink and medium grained with pink feldspar, translucent quartz and black shiny flakes of biotite. There are 1 cm thick veins of sugary-textured '''aplite''' and 2–3 mm thick veinlets of black tourmaline. The granite intrusion has been divided into three main components arranged more or less concentrically. The Marginal Variety is not easy to access, but the Granophyric Variety of the next zone in is the one exposed here and for the next 2.5 km along the burn. It is a true granite in composition.
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Near the edge of the wood on the north of the track is the first exposure of granite in the burn. It is pink and medium grained with pink feldspar, translucent quartz and black shiny flakes of biotite. There are 1 cm thick veins of sugary-textured aplite and 23 mm thick veinlets of black tourmaline. The granite intrusion has been divided into three main components arranged more or less concentrically. The Marginal Variety is not easy to access, but the Granophyric Variety of the next zone in is the one exposed here and for the next 2.5 km along the burn. It is a true granite in composition.
  
==== Locality 9 [NT 9333 2089] is at the gate across the track above Langleeford Hope ====
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==== Locality 9 [NT 9333 2089] is at the gate across the track above Langleeford Hope ====
  
 
On both sides of the valley there is a spread of till. Looking south the spread ends where the hillside suddenly steepens. The till forms scarp faces along the burn, indented by landslides and their scars. This is the principle mechanism of erosion of the till sheet, the slipped material being dumped into the stream and carried away to be redeposited in the alluvial floodplain. A secondary process is solifluction, forming terrace-like features commonly described as sheep tracks. These are best seen upstream of the farm.
 
On both sides of the valley there is a spread of till. Looking south the spread ends where the hillside suddenly steepens. The till forms scarp faces along the burn, indented by landslides and their scars. This is the principle mechanism of erosion of the till sheet, the slipped material being dumped into the stream and carried away to be redeposited in the alluvial floodplain. A secondary process is solifluction, forming terrace-like features commonly described as sheep tracks. These are best seen upstream of the farm.
  
==== Locality 10 [NT 9279 2029] is the first waterfall in Harthope Burn ====
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==== Locality 10 [NT 9279 2029] is the first waterfall in Harthope Burn ====
  
The contact between the Granophyric Variety and the Standrop Variety at the centre of the intrusion occurs in this area. Fine to medium-grained '''granophyric''' biotite granite occurs in the falls, containing areas of blotchy '''porphyry''' that have been described as volcanic '''xenoliths'''. Above the falls, near the stone sheep fold, the Standrop Variety appears. This is an even, medium-grained rock rich in dark minerals. Compositionally, it is a '''granodiorite''' and the commonest dark mineral is the pyroxene '''diopside'''. This rock continues upstream for some distance.
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The contact between the Granophyric Variety and the Standrop Variety at the centre of the intrusion occurs in this area. Fine to medium-grained granophyric biotite granite occurs in the falls, containing areas of blotchy porphyry that have been described as volcanic xenoliths. Above the falls, near the stone sheep fold, the Standrop Variety appears. This is an even, medium-grained rock rich in dark minerals. Compositionally, it is a granodiorite and the commonest dark mineral is the pyroxene diopside. This rock continues upstream for some distance.
  
 
=== Upper Coquet Valley ===
 
=== Upper Coquet Valley ===

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