Editing Geology and landscape of Upper Teesdale - an excursion

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== Excursion details ==
 
== Excursion details ==
  
=== Locality 1, Eggleston Burn [NY 989 252] ===
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=== Locality 1, Eggleston Burn [NY 989 252] ===
  
Approach from Eggleston village via either the B6282 (Middleton-in-Teesdale road) or B6278 (Stanhope road) and the linking minor road ([[:File:YGS_NORTROCK_FIG_16_2.jpg|Figure 16.2]]). Park on the roadside [NY 990 249], 150 m east of the spectacular gritstone viaduct across Eggleston Burn. Walk along the narrow path on the north side of the road (just to the east of the viaduct) for 100 m to a small ill-defined quarry. Here the Cleveland Dyke crosses the valley and burn in an east–west direction, emplaced into coarse '''feldspathic''' gritstones around the level of the Firestone Sill (Upper Carboniferous). The '''porphyritic tholeiitic''' dolerite of this minor intrusion has been modestly quarried on the east side of the burn for roadstone (trackways lead southwards from the lower section near the burn) and there are signs that the adjacent grits have also been quarried for local walling.
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Approach from Eggleston village via either the B6282 (Middleton-in-Teesdale road) or B6278 (Stanhope road) and the linking minor road ([[:File:YGS_NORTROCK_FIG_16_2.jpg|Figure 16.2]]). Park on the roadside [NY 990 249], 150 m east of the spectacular gritstone viaduct across Eggleston Burn. Walk along the narrow path on the north side of the road (just to the east of the viaduct) for too m to a small ill-defined quarry. Here the Cleveland Dyke crosses the valley and burn in an east–west direction, emplaced into coarse '''feldspathic''' gritstones around the level of the Firestone Sill (Upper Carboniferous). The '''porphyritic tholeiitic''' dolerite of this minor intrusion has been modestly quarried on the east side of the burn for roadstone (trackways lead southwards from the lower section near the burn) and there are signs that the adjacent grits have also been quarried for local walling.
  
The full c.15 m thickness of the dyke is best seen in the river cliff on the west side of the valley, where it has chilled ('''tachylitic''') margins and the adjacent grits have been mildly contact '''metamorphosed'''. It is, however, difficult from a distance to distinguish the sedimentary bedding of the host rock from the horizontal '''joints''' of the dyke. In the quarry on the east side of the burn the marginal contacts are not well exposed, but the quarry face does exhibit good examples of spheroidal weathering in the dyke.
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The full c.15 m thickness of the dyke is best seen in the river cliff on the west side of the valley, where it has chilled ('''tachylitic''') margins and the adjacent grits have been mildly contact '''metamorphosed'''. It is, however, difficult from a distance to distinguish the sedimentary bedding of the host rock from the horizontal '''joints''' of the dyke. In the quarry on the east side of the burn the marginal contacts are not well exposed, but the quarry face does exhibit good examples of spheroidal weathering in the dyke.
  
=== Locality 2, Whistle Crag [NY 978 247] ===
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=== Locality 2, Whistle Crag [NY 978 247] ===
  
 
From the lay-by on the B6282 is a panoramic view southwards of the southern marginal area of the Alston Block. Crags of Whin Sill can be seen below the skyline to the right, whilst the Lunedale–Butterknowle Fault runs just below the skyline on the left and out through the Lune Valley to the south. The Tees valley in the foreground is filled by late Quaternary tills and outwash alluvial deposits.
 
From the lay-by on the B6282 is a panoramic view southwards of the southern marginal area of the Alston Block. Crags of Whin Sill can be seen below the skyline to the right, whilst the Lunedale–Butterknowle Fault runs just below the skyline on the left and out through the Lune Valley to the south. The Tees valley in the foreground is filled by late Quaternary tills and outwash alluvial deposits.

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