Editing Lower Carboniferous of Bewcastle and Gilsland - an excursion

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== Excursion details ==
 
== Excursion details ==
  
=== Locality 1, Ashy Cleugh [NY 565 770]–[NY 570 767]; ([[:File:YGS_NORTROCK_FIG_05_2.jpg|Figure 5.2]]) ===
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=== Locality 1, Ashy Cleugh [NY 565 770]–[NY 570 767]; ([[:File:YGS_NORTROCK_FIG_05_2.jpg|Figure 5.2]]) ===
  
 
Permission for access should be sought from Stockastead Farm. Park by the track, near the disused limekiln.
 
Permission for access should be sought from Stockastead Farm. Park by the track, near the disused limekiln.
  
==== Locality 1a [NY 565 770] ====
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==== Locality 1a [NY 565 770] ====
  
Here the stream exposes the uppermost Lynebank Formation and the Bewcastle Formation. The lowermost unit of the latter, the 11 m thick Bogside Limestone Member, forms a series of small waterfalls and in the past has been quarried from this locality for lime. The Bogside Limestone is one of the thickest limestones developed in either the Lower Border or Cementstone groups over the area covered by this guide. It was deposited below normal wave base in a shallow marine environment. Thin bands packed with fossils were formed when occasional storms stirred up the sea floor and winnowed out the shelly material in the muddy sediment. The fossil fauna is dominated by '''brachiopods''' (mainly ''Antiquatonia teres), ''brachiopod spines, and '''crinoid''' fragments. The thin shale horizon towards the middle of the unit contains a moderately diverse '''bivalve''' fauna.
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Here the stream exposes the uppermost Lynebank Formation and the Bewcastle Formation. The lowermost unit of the latter, the it m thick Bogside Limestone Member, forms a series of small waterfalls and in the past has been quarried from this locality for lime. The Bogside Limestone is one of the thickest limestones developed in either the Lower Border or Cementstone groups over the area covered by this guide. It was deposited below normal wave base in a shallow marine environment. Thin bands packed with fossils were formed when occasional storms stirred up the sea floor and winnowed out the Shelly material in the muddy sediment. The fossil fauna is dominated by brachiopods (mainly ''Antiquatonia teres), ''brachiopod spines, and crinoid fragments. The thin shale horizon towards the middle of the unit contains a moderately diverse bivalve fauna.
  
Above the Bogside Limestone, shales with occasional sandstones and thin limestones, some of which are marine, crop out in the stream bed and banks ([[:File:YGS_NORTROCK_FIG_05_2.jpg|Figure 5.2]]). The persistent can reach Ashy Cleugh Locality 1b by following the stream through the trees.
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Above the Bogside Limestone, shales with occasional sandstones and thin limestones, some of which are marine, crop out in the stream bed and banks ([[:File:YGS_NORTROCK_FIG_05_2.jpg|Figure 5.2]]). The persistent can reach Ashy Cleugh Locality t b by following the stream through the trees.
  
 
==== Locality 1b ====
 
==== Locality 1b ====
  
From the limekiln, walk up around the south side of the quarry and along the edge of the small conifer plantation. Upstream from the edge of the plantation [NY 570 767] the upper part of the Bewcastle Formation, from the New House Limestone Member to the Junction Limestone Member ([[:File:YGS_NORTROCK_FIG_05_2.jpg|Figure 5.2]]), is exposed in the stream bed and in a series of low, shaley bluffs. This part of the formation is dominated by shales, with only a few sandstone and limestone beds, most of which are less than 1 m in thickness. Some of the shales are brecciated and probably represent the collapsed remains of '''evaporite''' beds, now leached away. Marine fossils are uncommon except in the 2.6 m thick Ashy Cleugh Limestone Member; its fauna is similar to that of the Bogside Limestone Member, although rather impoverished, and it was probably deposited in a similar environment. Occasional thin beds of '''oolite''' indicate high energy marine conditions, but the general absence of fully marine fossils from this part of the Bewcastle Formation, and the more common occurrences of bivalves, including ''Modiolus, '''''ostracodes,''' vermiform ''''gastropods'''', '''algae''', and abundant fragmentary plant remains suggest that marine influence was limited at this time.
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From the limekiln, walk up around the south side of the quarry and along the edge of the small conifer plantation. Upstream from the edge of the plantation [NY 570 767] the upper part of the Bewcastle Formation, from the New House Limestone Member to the Junction Limestone Member ([[:File:YGS_NORTROCK_FIG_05_2.jpg|Figure 5.2]]), is exposed in the stream bed and in a series of low, shaley bluffs. This part of the formation is dominated by shales, with only a few sandstone and limestone beds, most of which are less than 1 m in thickness. Some of the shales are brecciated and probably represent the collapsed remains of evaporite beds, now leached away. Marine fossils are uncommon except in the 2.6 m thick Ashy Cleugh Limestone Member; its fauna is similar to that of the Bogside Limestone Member, although rather impoverished, and it was probably deposited in a similar environment. Occasional thin beds of oolite indicate high energy marine conditions, but the general absence of fully marine fossils from this part of the Bewcastle Formation, and the more common occurrences of bivalves, including ''Modiolus, ''ostracodes, vermiform 'gastropods', algae, and abundant fragmentary plant remains suggest that marine influence was limited at this time.
  
 
=== Locality 2, Birky Cleugh [NY 588 754] – [NY 593 754]; (Figure 5.3) ===
 
=== Locality 2, Birky Cleugh [NY 588 754] – [NY 593 754]; (Figure 5.3) ===

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