Editing Geology of the North Tyne and Saughtree - an excursion

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Return to the road and turn left towards Kidder Village. 1 km beyond the village, the North Tyne, here reduced to a shallow stream due to headwater capture by the Liddel Water across the Border, is crossed on a stone bridge. After a further 2.4 km stop on the nearside verge opposite a pair of houses.
 
Return to the road and turn left towards Kidder Village. 1 km beyond the village, the North Tyne, here reduced to a shallow stream due to headwater capture by the Liddel Water across the Border, is crossed on a stone bridge. After a further 2.4 km stop on the nearside verge opposite a pair of houses.
  
==== Locality 10, Deadwater [NY 604 969] ====
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==== Locality 10, Deadwater [NY 604 969] ====
  
 
Below to the west is a large area of peat moss that forms the watershed of the Tyne and the Liddel Water. Quarries on the hillside beyond worked Middle Border Group freestone (sandstone) and limestone.
 
Below to the west is a large area of peat moss that forms the watershed of the Tyne and the Liddel Water. Quarries on the hillside beyond worked Middle Border Group freestone (sandstone) and limestone.
  
Continue on the road, crossing the border and passing a large double-arch lime kiln on the left. Limestone was worked in shallow quarries on the hillside beyond, but the beds are thin and the overburden increases rapidly into the hillside. After 2.5 km the road emerges from the forest, crosses a stone bridge and a cattle grid. Turn right immediately into a level grassy area by the stream.
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Continue on the road, crossing the border and passing a large double-arch lime kiln on the left. Limestone was worked in shallow quarries on the hillside beyond, but the beds are thin and the overburden increases rapidly into the hillside. After 2.5 km the road emerges from the forest, crosses a stone bridge and a cattle grid. Turn right immediately into a level grassy area by the stream.
  
==== Locality 11, Caddroun Burn [NY 584 985] ====
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==== Locality 11, Caddroun Burn [NY 584 985] ====
  
The burn flows southeast before it turns sharply to join Liddel Water, and was probably once a tributary of the North Tyne. A small exposure of sandstone dipping downstream, largely under water, at the downstream end of the large circular culvert represents the oldest exposed Carboniferous sediments in the Lower Border Group. Climb over the railway embankment. On its upstream side are exposures of the earliest Carboniferous Birrenswark Lavas below the sandstone. These are '''olivine basalts''', often vesicular especially towards the tops of flows, and usually highly weathered. Continue 250 m upstream of the culvert to a small cliff on the west bank showing 5–6 m of Upper Old Red Sandstone. This exposure is loose and overhanging. Traces of drilling suggest it was quarried, probably for railway construction. The O.R.S. here consists mainly of red and mottled sandstones with subordinate mudstones and sandy shales. There are two horizons of '''calcrete''', one at the base approximately 10 cm thick and another near the top of the succession about 1.1 m thick. The base of the lavas is visible at the top of the exposure and can be inspected safely in a smaller exposure 20 m upstream where it is vesicular and exhibits spheroidal weathering. The lavas appear to be conformable with the O.R.S. and dip downstream at about . If time permits, further good exposures of the O.R.S. can be seen 400 m upstream in the Caddroun Pots, a series of scour holes in the stream bed.
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The burn flows southeast before it turns sharply to join Liddel Water, and was probably once a tributary of the North Tyne. A small exposure of sandstone dipping downstream, largely under water, at the downstream end of the large circular culvert represents the oldest exposed Carboniferous sediments in the Lower Border Group. Climb over the railway embankment. On its upstream side are exposures of the earliest Carboniferous Birrenswark Lavas below the sandstone. These are olivine basalts, often vesicular especially towards the tops of flows, and usually highly weathered. Continue 250 m upstream of the culvert to a small cliff on the west bank showing 5–6 m of Upper Old Red Sandstone. This exposure is loose and overhanging. Traces of drilling suggest it was quarried, probably for railway construction. The O.R.S. here consists mainly of red and mottled sandstones with subordinate mudstones and sandy shales. There are two horizons of calcrete, one at the base approximately 10 cm thick and another near the top of the succession about r.1 m thick. The base of the lavas is visible at the top of the exposure and can be inspected safely in a smaller exposure 20 m upstream where it is vesicular and exhibits spheroidal weathering. The lavas appear to be conformable with the O.R.S. and dip downstream at about 5. If time permits, further good exposures of the O.R.S. can be seen 400 m upstream in the Caddroun Pots, a series of scour holes in the stream bed.
  
 
Rejoin the road. Continue southwest to the second of two prominent rock scars on the left, parking at a lay-by just before a stone wall meets the road at right-angles.
 
Rejoin the road. Continue southwest to the second of two prominent rock scars on the left, parking at a lay-by just before a stone wall meets the road at right-angles.
  
==== Locality 12, Hudshouse [NY 576 978] ====
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==== Locality 12, Hudshouse [NY 576 978] ====
  
 
The scar is steep and unstable and it should be examined from the near bank of the stream. It exhibits two different aspects. On the left are thinly bedded dark shales, mudstones, siltstones and limestones probably of the Middle Border Group. On the right the rock is mostly unstratified and blocky, with rounded corners where weathering has penetrated. This is a dolerite dyke trending approximately northwest–southeast, almost parallel to the face and probably of Tertiary age. The field relations here may appear confusing, but the dyke is not truly vertical and steps back as it rises, while part of it has been undercut by the river and has fallen away to reveal the sediments behind.
 
The scar is steep and unstable and it should be examined from the near bank of the stream. It exhibits two different aspects. On the left are thinly bedded dark shales, mudstones, siltstones and limestones probably of the Middle Border Group. On the right the rock is mostly unstratified and blocky, with rounded corners where weathering has penetrated. This is a dolerite dyke trending approximately northwest–southeast, almost parallel to the face and probably of Tertiary age. The field relations here may appear confusing, but the dyke is not truly vertical and steps back as it rises, while part of it has been undercut by the river and has fallen away to reveal the sediments behind.
  
Return to the road and note on the northwest side a succession of roughly semicircular landslip scars, probably formed at a time when the river was higher and was actively cutting into the lower slope. Apart from soil creep shown by terracettes these old slips are now reasonably stable. However, within the next 400 m along the road, notice that cuts have been made to widen the road and numerous small scarps show that movements have been reactivated. The slopes above are relatively gentle and are underlain by drift which has probably been soliflucted.
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Return to the road and note on the northwest side a succession of roughly semicircular landslip scars, probably formed at a time when the river was higher and was actively cutting into the lower slope. Apart from soil creep shown by terracettes these old slips are now reasonably stable. However, within the next 400 m along the road, notice that cuts have been made to widen the road and numerous small scarps show that movements have been reactivated. The slopes above are relatively gentle and are underlain by drift which has probably been soliflucted.
  
Continue to Saughtree and turn right at the T-junction [NY 561 967] on to the B6357. Cross a small stone bridge and notice further examples of landslipping on the drift slopes to the left. Cross a cattle grid and park in a lay-by, immediately after a stone bridge which crosses the stream to the left.
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Continue to Saughtree and turn right at the T-junction [NY 561 967] on to the B6357. Cross a small stone bridge and notice further examples of landslipping on the drift slopes to the left. Cross a cattle grid and park in a lay-by, immediately after a stone bridge which crosses the stream to the left.
  
==== Locality 13, Dawston Burn [NY 568 981] ====
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==== Locality 13, Dawston Burn [NY 568 981] ====
  
This is the site of a BCR viaduct, demolished when the line was closed. Looking downstream from the bridge, outcrops dipping downstream at low angles are of Lower Border Group sandstones, possibly the equivalent of the Whita Sandstone of the Langholm area. These beds underlie the drift in the slopes to the right, but above the line of the old railway, scattered stream exposures are mainly in the O.R.S. The hills that form the northwest skyline (Saughtree Fell) are underlain by Silurian greywackes. The oldest rocks thus occupy the highest ground. The field relations in this area are obscure due to the lack of exposure but some outcrops of the O.R.S. have vertical bedding, suggesting faulting or '''monoclinal folding''', or both.
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This is the site of a BCR viaduct, demolished when the line was closed. Looking downstream from the bridge, outcrops dipping downstream at low angles are of Lower Border Group sandstones, possibly the equivalent of the Whita Sandstone of the Langholm area. These beds underlie the drift in the slopes to the right, but above the line of the old railway, scattered stream exposures are mainly in the O.R.S. The hills that form the northwest skyline (Saughtree Fell) are underlain by Silurian greywackes. The oldest rocks thus occupy the highest ground. The field relations in this area are obscure due to the lack of exposure but some outcrops of the O.R.S. have vertical bedding, suggesting faulting or monoclinal folding, or both.
  
The same succession is discontinuously exposed in the Dawston Burn for 1 km upstream of the bridge, but is difficult to see if the water is high. Unless the transport can follow, it may be best to examine the lower part of the section, return to the lay-by and then drive to Locality 14.
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The same succession is discontinuously exposed in the Dawston Burn for 1 km upstream of the bridge, but is difficult to see if the water is high. Unless the transport can follow, it may be best to examine the lower part of the section, return to the lay-by and then drive to Locality 14.
  
As in the Caddroun Burn, the beds dip downstream and older strata are encountered upstream. The Lower Border Group is represented mainly by sandstone, although there are a few exposures of shales. A dyke which may be the extension of the Hudshouse Dyke cuts the section. The Birrenswark Lavas crop out approximately 400 m upstream of the bridge and may be traced up the slope southeast of the road. Sandstones of the Upper O.R.S. underlie the lavas but differ little in lithology from some of the Carboniferous sandstones.
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As in the Caddroun Burn, the beds dip downstream and older strata are encountered upstream. The Lower Border Group is represented mainly by sandstone, although there are a few exposures of shales. A dyke which may be the extension of the Hudshouse Dyke cuts the section. The Birrenswark Lavas crop out approximately 400 m upstream of the bridge and may be traced up the slope southeast of the road. Sandstones of the Upper O.R.S. underlie the lavas but differ little in lithology from some of the Carboniferous sandstones.
  
From the lay-by continue 1 km up the road to the end of the safety fence. Here the stream swings away from the road and it is possible to park on a grassy track to the left.
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From the lay-by continue 1 km up the road to the end of the safety fence. Here the stream swings away from the road and it is possible to park on a grassy track to the left.
  
==== Locality 14 [NY 574 989] ====
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==== Locality 14 [NY 574 989] ====
  
On the slope across the stream there is a rather vegetated exposure of the O.R.S. which dips downstream at about 20° and consists of planar and cross-bedded red sandstones with some pebbly horizons, particularly towards the base. To the right of this, and in the stream bed, Silurian greywackes crop out, dipping downstream at 55–60°. These are greywacke-siltstones and mudstones of Wenlock age with poorly developed '''cleavage'''. The unconformity between the O.R.S. and the Silurian is not exposed.
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On the slope across the stream there is a rather vegetated exposure of the O.R.S. which dips downstream at about 20° and consists of planar and cross-bedded red sandstones with some pebbly horizons, particularly towards the base. To the right of this, and in the stream bed, Silurian greywackes crop out, dipping downstream at 55–60°. These are greywacke-siltstones and mudstones of Wenlock age with poorly developed cleavage. The unconformity between the O.R.S. and the Silurian is not exposed.
  
If continuing up the valley, as the road climbs, further exposures of weathered greywackes will be seen along the roadside. 200 m beyond the cattle grid stop on the left at the entrance to a disused quarry. In clear weather, the Tyne-Liddel watershed can be seen beyond the deep valley of the Caddroun Burn.
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If continuing up the valley, as the road climbs, further exposures of weathered greywackes will be seen along the roadside. 200 m beyond the cattle grid stop on the left at the entrance to a disused quarry. In clear weather, the Tyne-Liddel watershed can be seen beyond the deep valley of the Caddroun Burn.
  
 
== [[Northumbrian rocks and landscape: a field guide#Glossary|Glossary]] ==
 
== [[Northumbrian rocks and landscape: a field guide#Glossary|Glossary]] ==

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