Editing Lower Carboniferous of Bewcastle and Gilsland - an excursion

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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.
 
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) ===
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=== Locality 2, Birky Cleugh [NY 588 754] – [NY 593 754]; (Figure 5.3) ===
  
Birky Cleugh is an '''S.S.S.I.''' and prior permission for access should be sought (see Logistics); ''hammering is not permitted ''but loose fossils may be collected. From Bewcastle church, take the road over the river past the Limekiln Inn. After 200 m go through the gate by the post-box on the left and take the right-hand track for about 2.5 km to High Grains House; park by the track. ''Note: ''The track to High Grains can be muddy and is very rough in places.
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Birky Cleugh is an S.S.S.I. and prior permission for access should be sought (see Logistics); ''hammering is not permitted ''but loose fossils may be collected. From Bewcastle church, take the road over the river past the Limekiln Inn. After 200 m go through the gate by the post-box on the left and take the right-hand track for about 2.5 km to High Grains House; park by the track. ''Note: ''The track to High Grains can be muddy and is very rough in places.
  
In the shallow gorge below the house the High Grains Sandstone Member of the uppermost Bewcastle Formation can be seen. Walk round the north side of the house and take the track down to the stream. Upstream from the point where the track crosses Birky Cleugh [NY 588 754] the whole of the Main Algal Formation and the lower part of the overlying Cambeck Formation is exposed as a series of low bluffs and waterfalls. The prominent orange weathering limestone in the first bluff is Main Algal Limestone Member 1 ([[:File:YGS_NORTROCK_FIG_05_3.jpg|Figure 5.3]]), which contains small but well developed algal-vermiform 'gastropod' patch reefs. The thick limestone in the waterfall 150 m upstream is the Birky Cleugh Limestone Member. Most of the limestones of the Main Algal Formation are algal in character and well developed algal nodules and encrusting mats are exposed at various horizons in Birky Cleugh. At the time of their deposition this area was a warm, shallow marine gulf with fluctuating salinity and minimal tidal activity. The lower parts of the Cambeck Formation exposed in the higher reaches of the stream ([[:File:YGS_NORTROCK_FIG_05_3.jpg|Figure 5.3]]) contain a more fully marine shelly fauna dominated by the brachiopod ''Antiquatonia teres.''
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In the shallow gorge below the house the High Grains Sandstone Member of the uppermost Bewcastle Formation can be seen. Walk round the north side of the house and take the track down to the stream. Upstream from the point where the track crosses Birky Cleugh [NY 588 754] the whole of the Main Algal Formation and the lower part of the overlying Cambeck Formation is exposed as a series of low bluffs and waterfalls. The prominent orange weathering limestone in the first bluff is Main Algal Limestone Member 1 ([[:File:YGS_NORTROCK_FIG_05_3.jpg|Figure 5.3]]), which contains small but well developed algal-vermiform 'gastropod' patch reefs. The thick limestone in the waterfall 150 m upstream is the Birky Cleugh Limestone Member. Most of the limestones of the Main Algal Formation are algal in character and well developed algal nodules and encrusting mats are exposed at various horizons in Birky Cleugh. At the time of their deposition this area was a warm, shallow marine gulf with fluctuating salinity and minimal tidal activity. The lower parts of the Cambeck Formation exposed in the higher reaches of the stream ([[:File:YGS_NORTROCK_FIG_05_3.jpg|Figure 5.3]]) contain a more fully marine shelly fauna dominated by the brachiopod ''Antiquatonia teres.''
  
 
=== Locality 3, River Black Lyne – Oakshaw Ford [NY 513 766] ===
 
=== Locality 3, River Black Lyne – Oakshaw Ford [NY 513 766] ===

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