Editing Millstone Grit of Almscliff Crag and Harlow Car, near Harrogate - an excursion

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From the A658 Harrogate–Otley road, take the signposted road uphill to North Rigton. At the west end of the village, turn into Crag Lane and continue past Almscliff Crag to Locality 1. Park by the road [SE 265 491].
 
From the A658 Harrogate–Otley road, take the signposted road uphill to North Rigton. At the west end of the village, turn into Crag Lane and continue past Almscliff Crag to Locality 1. Park by the road [SE 265 491].
  
==== Locality 1 [SE 265 491] - at the roadside ====
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==== Locality 1 [SE 265 491] is at the roadside ====
  
 
Seen from here, the Crag is clearly made up of two cliffs, each about 15 m high, separated by a flattish slack. Big blocks have fallen off the cliffs. Walk up the footpath to the lower crag.
 
Seen from here, the Crag is clearly made up of two cliffs, each about 15 m high, separated by a flattish slack. Big blocks have fallen off the cliffs. Walk up the footpath to the lower crag.
  
==== Locality 2 - the lower crag ====
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==== Locality 2 is the lower crag ====
  
 
Climb up and proceed anticlockwise round the top of it. The Almscliff Grit is a coarse to very coarse-grained sandstone with scattered pebbles of '''quartz'''. The major bedding planes '''dip''' northeast at about 22°. Approximately 1 m wide trough '''cross-bedding''' sets clearly indicate sand transport by currents flowing from the northeast. The cross-bedding can be seen below overhangs and on the top (dip slope) surface of the lower crag.
 
Climb up and proceed anticlockwise round the top of it. The Almscliff Grit is a coarse to very coarse-grained sandstone with scattered pebbles of '''quartz'''. The major bedding planes '''dip''' northeast at about 22°. Approximately 1 m wide trough '''cross-bedding''' sets clearly indicate sand transport by currents flowing from the northeast. The cross-bedding can be seen below overhangs and on the top (dip slope) surface of the lower crag.
  
==== Locality 3 - across the flattish slack area at the foot of the upper crag ====
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==== Locality 3 is just across the flattish slack area at the foot of the upper crag ====
  
 
The bedding on this face looks flat, but continue anticlockwise round the base of the cliff until the relationship between cross-bedding and '''tectonic''' dip again becomes clear. Both are much the same as in the lower crag. Good cross-bedding troughs, again pointing southwest, can be seen on the dip slope of this crag also.
 
The bedding on this face looks flat, but continue anticlockwise round the base of the cliff until the relationship between cross-bedding and '''tectonic''' dip again becomes clear. Both are much the same as in the lower crag. Good cross-bedding troughs, again pointing southwest, can be seen on the dip slope of this crag also.
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Walk down the path to the road at Crag Farm and turn left.
 
Walk down the path to the road at Crag Farm and turn left.
  
==== Locality 4 - on the road by Cliff House ====
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==== Locality 4 is on the road by Cliff House ====
  
 
Look up the dip slope towards the crag. The difference in dip direction, and the fact that the crag sandstone underlies the sandstone of the dip slope, can both be appreciated from here. Proceed along the road as far as the first houses in North Rigton and take the footpath on the left, leading back towards Almscliff Crag.
 
Look up the dip slope towards the crag. The difference in dip direction, and the fact that the crag sandstone underlies the sandstone of the dip slope, can both be appreciated from here. Proceed along the road as far as the first houses in North Rigton and take the footpath on the left, leading back towards Almscliff Crag.
  
==== Locality 5 [SE 276 491] - at the start of the footpath ====
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==== Locality 5 [SE 276 491] is at the start of the footpath ====
  
 
At first this runs along the top of the dip slope but eventually it slants across the crest on to the scarp side. Like many of the features formed by sandstones in this area, the ridge is low and rounded, with no clear indication of where the base of the sandstone might lie. This is due to glacial action, which has smoothed off the finer topographical details and smeared a layer of till over all but the highest parts of the ridges. The position of the base of the grit on the map is therefore approximate.
 
At first this runs along the top of the dip slope but eventually it slants across the crest on to the scarp side. Like many of the features formed by sandstones in this area, the ridge is low and rounded, with no clear indication of where the base of the sandstone might lie. This is due to glacial action, which has smoothed off the finer topographical details and smeared a layer of till over all but the highest parts of the ridges. The position of the base of the grit on the map is therefore approximate.
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About 200 m short of the crag, the ridge sticks up out of the till, and small quarries reveal sandstone dipping at 15–20° southeast. It is clear that the angle of the dip slope is somewhat less than the dip of the strata. Bevelled dip slopes of this sort are very common in Millstone Grit scenery. Proceed along the ridge to where it joins the crag.
 
About 200 m short of the crag, the ridge sticks up out of the till, and small quarries reveal sandstone dipping at 15–20° southeast. It is clear that the angle of the dip slope is somewhat less than the dip of the strata. Bevelled dip slopes of this sort are very common in Millstone Grit scenery. Proceed along the ridge to where it joins the crag.
  
==== Locality 6 - a small quarry with a pond in it ====
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==== Locality 6 is a small quarry with a pond in it ====
  
 
Poorly bedded sandstone dips to the southeast, whilst immediately to the north, the northeasterly dipping sandstones of the crag appear. There is no obvious dividing line between the two sets of strata, suggesting that the slumped sandstone was still soft when the overlying sandstone was laid down on it, so that the two have blurred into each other. Continue anticlockwise round the north side of the crag. A noticeable break of slope at the foot of the crag here marks the likely position of the slump fault.
 
Poorly bedded sandstone dips to the southeast, whilst immediately to the north, the northeasterly dipping sandstones of the crag appear. There is no obvious dividing line between the two sets of strata, suggesting that the slumped sandstone was still soft when the overlying sandstone was laid down on it, so that the two have blurred into each other. Continue anticlockwise round the north side of the crag. A noticeable break of slope at the foot of the crag here marks the likely position of the slump fault.
  
==== Locality 7 - at the foot of the overhanging cliff====
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==== Locality 7 is at the foot of the overhanging cliff====
  
 
Here a mud-flake '''conglomerate''' can be seen. Irregularly shaped holes, up to 10 cm across, show where mudstone pebbles have weathered out. The pebbles are scattered through a 1 to 2 m thickness of sandstone.
 
Here a mud-flake '''conglomerate''' can be seen. Irregularly shaped holes, up to 10 cm across, show where mudstone pebbles have weathered out. The pebbles are scattered through a 1 to 2 m thickness of sandstone.
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From the centre of Harrogate take the B6162 towards Beckwithshaw. On the outskirts of town, follow the signs for Harlow Car Gardens and turn off down Crag Lane. Park opposite the entrance to the Gardens [SE 281 542], and walk down Crag Lane. Take the first side road on the left, past the Harrogate Arms. At the gates to Harlow Car Study Centre, follow the marked footpath leading off right, along the bank of Harlow Car Beck. The stream gradually cuts deeper until it forms a small ravine, exposing the beds that lie immediately under the Almscliff Grit. The dip is steep, so that about 270 m of these beds crop out over a distance of 400 m. Exposure is not continuous, and the location of the clearest sections varies from year to year, depending on accidents of stream erosion.
 
From the centre of Harrogate take the B6162 towards Beckwithshaw. On the outskirts of town, follow the signs for Harlow Car Gardens and turn off down Crag Lane. Park opposite the entrance to the Gardens [SE 281 542], and walk down Crag Lane. Take the first side road on the left, past the Harrogate Arms. At the gates to Harlow Car Study Centre, follow the marked footpath leading off right, along the bank of Harlow Car Beck. The stream gradually cuts deeper until it forms a small ravine, exposing the beds that lie immediately under the Almscliff Grit. The dip is steep, so that about 270 m of these beds crop out over a distance of 400 m. Exposure is not continuous, and the location of the clearest sections varies from year to year, depending on accidents of stream erosion.
  
==== Locality 8 [SE 2773 5425] - a chalybeate (iron-rich) spring, covered by a rounded stone canopy ====
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==== Locality 8 [SE 2773 5425] is a chalybeate (iron-rich) spring, covered by a rounded stone canopy ====
  
 
The water emerging is clear, but it gives rise to a rusty deposit as it flows away. This is one of numerous mineral springs that rise in the axial area of the Harrogate Anticline; the Harrogate spa waters are the sulphurous ones. Sandstones and siltstones crop out in the stream bed below, and are exposed at intervals to Locality 9, where access is better.
 
The water emerging is clear, but it gives rise to a rusty deposit as it flows away. This is one of numerous mineral springs that rise in the axial area of the Harrogate Anticline; the Harrogate spa waters are the sulphurous ones. Sandstones and siltstones crop out in the stream bed below, and are exposed at intervals to Locality 9, where access is better.
  
==== Locality 9 [SE 2757 5437] - at a wooden footbridge below a fork in the path ====
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==== Locality 9 [SE 2757 5437] is at a wooden footbridge below a fork in the path ====
  
 
The bridge gives easy access to the stream bed. The base of the Almscliff Grit crosses the stream about too m below the bridge, but is not well exposed. The beds below the grit can be seen in the sections on both sides of the bridge. They are dark grey argillaceous siltstones with a great variety of paler-coloured sandstone interbeds, ranging from a few millimetres to over a metre in thickness. Some of the sandstone beds are graded, with '''sole structures''', and are probably turbidites. All suggest rapid deposition on a delta slope fed from the mouth of a large river. Instability of these deposits, giving a tendency to collapse under their own weight, is likely to have caused the slump-faulting observed at Almscliff Crag.
 
The bridge gives easy access to the stream bed. The base of the Almscliff Grit crosses the stream about too m below the bridge, but is not well exposed. The beds below the grit can be seen in the sections on both sides of the bridge. They are dark grey argillaceous siltstones with a great variety of paler-coloured sandstone interbeds, ranging from a few millimetres to over a metre in thickness. Some of the sandstone beds are graded, with '''sole structures''', and are probably turbidites. All suggest rapid deposition on a delta slope fed from the mouth of a large river. Instability of these deposits, giving a tendency to collapse under their own weight, is likely to have caused the slump-faulting observed at Almscliff Crag.
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Follow the path, which climbs up the east bank of the stream to the lip of Oakdale and along a ridge marking the outcrop of the Almscliff Grit.
 
Follow the path, which climbs up the east bank of the stream to the lip of Oakdale and along a ridge marking the outcrop of the Almscliff Grit.
  
==== Locality 10 [SE 2774 5463] - just before the path meets Crag Lane, by Birk Crag House ====
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==== Locality 10 [SE 2774 5463] is just before the path meets Crag Lane, by Birk Crag House, where there are some crags of Almscliff Grit with small quarries ====
  
There are some crags of Almscliff Grit with small quarries. The rock is very coarse-grained (coarser than most of the sandstones in the underlying beds), with small quartz pebbles. The bedding dips steeply (at 45–70°) into the valley, and this side of Oakdale is essentially a bevelled dip slope on the top of the main part of the grit. Trough cross-bedding can be seen on top of some of the steeply dipping beds indicating southwestwards flow, as at Almscliff Crag. The path continues along strike, past more gritstone outcrops at Birk Crag [SE 2795 5480], to Cornwall Road, an alternative point of access [SE 2842 5516].
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The rock is very coarse-grained (coarser than most of the sandstones in the underlying beds), with small quartz pebbles. The bedding dips steeply (at 45–70°) into the valley, and this side of Oakdale is essentially a bevelled dip slope on the top of the main part of the grit. Trough cross-bedding can be seen on top of some of the steeply dipping beds indicating southwestwards flow, as at Almscliff Crag. The path continues along strike, past more gritstone outcrops at Birk Crag [SE 2795 5480], to Cornwall Road, an alternative point of access [SE 2842 5516].
  
 
Walk back to Harlow Car by the direct route, along Crag Lane.
 
Walk back to Harlow Car by the direct route, along Crag Lane.

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