Editing Carboniferous (Namurian and Westphalian) of the Cliviger Valley, Todmorden - an excursion

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The Gastrioceras cancellatum Marine Band is exposed in a small shale cliff and on the water-worn ledges at stream level at this location in the lower reaches of Ratten Clough. The shales of the marine band have been cemented to form a hard, resistant lithology.
 
The Gastrioceras cancellatum Marine Band is exposed in a small shale cliff and on the water-worn ledges at stream level at this location in the lower reaches of Ratten Clough. The shales of the marine band have been cemented to form a hard, resistant lithology.
  
A short distance upstream, the Lower Haslingden Flags form a small waterfall. Only 10   thick here, this sandstone is considerably thicker further to the southwest around Rochdale and Bury where it is quarried for flagstone.
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A short distance upstream, the Lower Haslingden Flags form a small waterfall. Only 10 m thick here, this sandstone is considerably thicker further to the southwest around Rochdale and Bury where it is quarried for flagstone.
  
 
=== Locality 2 [SD 890 267] ===
 
=== Locality 2 [SD 890 267] ===
  
Ascend the increasingly steep and eventually precipitous Ratten Clough to the base of a superb cliff section of the Rough Rock — the quintessential example of a Millstone Grit, a coarse, '''feldspathic''' sandstone. In the lower, most accessible part of the cliff, the thin beds of fine sandstone belong to the Upper Haslingden Flags. This again is the rather feeble development of a sandstone which is thicker to the southwest. The Rough Rock, in contrast, occurs throughout the Pennines. At this locality it can be seen to erode down into the Upper Haslingden Flags for 10 cm, but on a larger scale the down-cutting is more spectacular. At Beater Clough, 600 m south of this locality, the erosion has cut down to a level nearly 15 m lower than that seen in Ratten Clough. The basal beds of the Rough Rock contain numerous stems of ''Calamites ''which probably occurred as log-jams in the fast-flowing rivers that deposited the Rough Rock. The abundant '''cross-beds''' seen in the cliff face represent cross-sections through sand bars within these river channels.
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Ascend the increasingly steep and eventually precipitous Ratten Clough to the base of a superb cliff section of the Rough Rock — the quintessential example of a Millstone Grit, a coarse, feldspathic sandstone. In the lower, most accessible part of the cliff, the thin beds of fine sandstone belong to the Upper Haslingden Flags. This again is the rather feeble development of a sandstone which is thicker to the southwest. The Rough Rock, in contrast, occurs throughout the Pennines. At this locality it can be seen to erode down into the Upper Haslingden Flags for to cm, but on a larger scale the down-cutting is more spectacular. At Beater Clough, 600 m south of this locality, the erosion has cut down to a level nearly 15 m lower than that seen in Ratten Clough. The basal beds of the Rough Rock contain numerous stems of ''Calamites ''which probably occurred as log-jams in the fast-flowing rivers that deposited the Rough Rock. The abundant cross-beds seen in the cliff face represent cross-sections through sand bars within these river channels.
  
 
=== Locality 3 [SD 888 267] ===
 
=== Locality 3 [SD 888 267] ===
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Those who have the stamina can make their way around the Rough Rock escarpment to the headwaters of Ratten Clough where the Gastrioceras subcrenatum Marine Band occurs. This contains goniatites and bivalves, and is taken as the boundary between the Namurian and the Westphalian.
 
Those who have the stamina can make their way around the Rough Rock escarpment to the headwaters of Ratten Clough where the Gastrioceras subcrenatum Marine Band occurs. This contains goniatites and bivalves, and is taken as the boundary between the Namurian and the Westphalian.
  
It is instructive to view the hillside on the opposite side of the Cliviger Valley from this point. A series of ridges with steep southeasterly and gentle northwesterly slopes represents the expression of several Westphalian cyclothems '''dipping''' at around 20° to the west — sandstones form the ridge-tops. This is in contrast to the strata just examined on the southwest side of the valley which dip very gently to the southwest. The change in dip and '''strike''' occurs across the Cliviger Fault which runs along the line of the railway line in this part of the valley. This is a major fault with a '''downthrow''' of over 200 m to the north, along which patchy deposits of galena have been mined.
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It is instructive to view the hillside on the opposite side of the Cliviger Valley from this point. A series of ridges with steep southeasterly and gentle northwesterly slopes represents the expression of several Westphalian cyclothems dipping at around 20° to the west — sandstones form the ridge-tops. This is in contrast to the strata just examined on the southwest side of the valley which dip very gently to the southwest. The change in dip and strike occurs across the Cliviger Fault which runs along the line of the railway line in this part of the valley. This is a major fault with a downthrow of over 200 m to the north, along which patchy deposits of galena have been mined.
  
 
For the second half of the excursion, cars are best parked in Cornholme for there is little parking space in the Pudsey Clough valley. Make your way up this valley, noting the impressive crags of the Reddish Shore Rocks at the head of the Clough. This is the Rough Rock again which is here curiously weathered into very large rounded blocks.
 
For the second half of the excursion, cars are best parked in Cornholme for there is little parking space in the Pudsey Clough valley. Make your way up this valley, noting the impressive crags of the Reddish Shore Rocks at the head of the Clough. This is the Rough Rock again which is here curiously weathered into very large rounded blocks.
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=== Locality 5 [SD 905 271] ===
 
=== Locality 5 [SD 905 271] ===
  
Coal Clough shows a sharp deviation in its course as it cuts down through a thin sandstone, the Ganister Rock. Several interesting features can be demonstrated at this outcrop which help us to understand Coal Measure deposition. The basal contact of the sandstone is erosive, cutting down into the shale (which here contains siderite nodules) for up to 40 cm. Clearly, sand deposition was preceded by an interval of erosion. Within the lower beds of sandstone there are large 'rafts' of coal, a few centimetres thick and up to 3 m wide. The coal does not represent ''in situ ''growth of plants as there are no roots developed beneath it. However the rafts are too large to have been carried far from their original site of formation. This sandstone probably accumulated in a river channel which was undercutting its peaty banks, causing large pieces to fall into the channel.
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Coal Clough shows a sharp deviation in its course as it cuts down through a thin sandstone, the Ganister Rock. Several interesting features can be demonstrated at this outcrop which help us to understand Coal Measure deposition. The basal contact of the sandstone is erosive, cutting down into the shale (which here contains siderite nodules) for up to 40 cm. Clearly, sand deposition was preceded by an interval of erosion. Within the lower beds of sandstone there are large 'rafts' of coal, a few centimetres thick and up to 3 m wide. The coal does not represent ''in situ ''growth of plants as there are no roots developed beneath it. However the rafts are too large to have been carried far from their original site of formation. This sandstone probably accumulated in a river channel which was undercutting its peaty banks, causing large pieces to fall into the channel.
  
 
=== Locality 6 [SD 904 273] ===
 
=== Locality 6 [SD 904 273] ===
  
If permission has been obtained at Coal Clough Farm, ascend the upper reaches of Coal Clough to where an impressive 100 m long cliff section displays a variety of Coal Measure shales. At the base of the cliff, the Lower Mountain Mine coal seam is developed with a sandstone rib at its centre. This is directly overlain by the Gastrioceras listeri Marine Band, which contains goniatites and several species of bivalve including the spectacular, radially ribbed ''Dunbarella papyracea. ''The marine band contains large bullions (carbonate concretions) which formed early in the burial history of the shale, thereby preserving the goniatites in an uncompacted state. Occasionally the chambers of the goniatites contain a viscous, green oil rather like ''Swarfega, ''presumably the decomposed remains of the goniatite animal itself.
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If permission has been obtained at Coal Clough Farm, ascend the upper reaches of Coal Clough to where an impressive i oo m long cliff section displays a variety of Coal Measure shales. At the base of the cliff, the Lower Mountain Mine coal seam is developed with a sandstone rib at its centre. This is directly overlain by the Gastrioceras listeri Marine Band, which contains goniatites and several species of bivalve including the spectacular, radially ribbed ''Dunbarella papyracea. ''The marine band contains large bullions (carbonate concretions) which formed early in the burial history of the shale, thereby preserving the goniatites in an uncompacted state. Occasionally the chambers of the goniatites contain a viscous, green oil rather like ''Swarfega, ''presumably the decomposed remains of the goniatite animal itself.
  
 
The following sections in Paul Clough can either be examined by returning to Locality 4 or, as described here, by crossing the moorland from Locality 6 to Stiperden House and walking downstream. The dip of the rocks in Paul Clough is rather steep which means that an exceptionally large amount of Namurian stratigraphy can be seen over a relatively short distance.
 
The following sections in Paul Clough can either be examined by returning to Locality 4 or, as described here, by crossing the moorland from Locality 6 to Stiperden House and walking downstream. The dip of the rocks in Paul Clough is rather steep which means that an exceptionally large amount of Namurian stratigraphy can be seen over a relatively short distance.
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=== Locality 8 [SD 907 276] ===
 
=== Locality 8 [SD 907 276] ===
  
The third sandstone, the Holcombe Brook Grit, and its overlying shales, is rather better exposed. In many parts of this region this Grit is capped by a good-quality coal, one of the oldest hereabouts. However at this locality a cannel coal is developed, a much poorer quality shaly coal that is formed by the transport and deposition of vegetation in pools and ponds. The cannel coal sits on a '''seatearth''' containing curious lumpy concretions.
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The third sandstone, the Holcombe Brook Grit, and its overlying shales, is rather better exposed. In many parts of this region this Grit is capped by a good-quality coal, one of the oldest hereabouts. However at this locality a cannel coal is developed, a much poorer quality shaly coal that is formed by the transport and deposition of vegetation in pools and ponds. The cannel coal sits on a seatearth containing curious lumpy concretions.
  
Around 30 m downstream from the top bedding plane of the Holcombe Brook Grit, the Gastrioceras cancellatum Marine Band occurs at stream level. The fossils are rather poorly preserved at this locality.
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Around 30 m downstream from the top bedding plane of the Holcombe Brook Grit, the Gastrioceras cancellatum Marine Band occurs at stream level. The fossils are rather poorly preserved at this locality.
  
 
=== Locality 9 [SD 907 273] ===
 
=== Locality 9 [SD 907 273] ===
  
Further downstream, the Lower Haslingden Flags intersect the stream. Around 2 m above the top of the sandstone a hard-weathering, fissile, black shale sits on a horizon of contorted shale. The appearance of this shale and its geochemical attributes are identical to that of marine band black shales; this is the newly discovered Owd Bett's Marine Band. It is named after a type locality north of Bury. The only marine fauna consists of rare '''conodont''' microfossils. More of these marine bands without goniatites probably await discovery in the Pennines. The Gastrioceras cumbriense Marine Band occurs a further 2 m above the Owd Bett's Marine Band at the top of the section ([[:File:YGS_YORKROCK_FIG_08_03.jpg|Figure 8.3]]).
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Further downstream, the Lower Haslingden Flags intersect the stream. Around 2 m above the top of the sandstone a hard-weathering, fissile, black shale sits on a horizon of contorted shale. The appearance of this shale and its geochemical attributes are identical to that of marine band black shales; this is the newly discovered Owd Bett's Marine Band. It is named after a type locality north of Bury. The only marine fauna consists of rare conodont microfossils. More of these marine bands without goniatites probably await discovery in the Pennines. The Gastrioceras cumbriense Marine Band occurs a further 2 m above the Owd Bett's Marine Band at the top of the section ([[:File:YGS_YORKROCK_FIG_08_03.jpg|Figure 8.3]]).
  
 
=== Locality 10 [SD 907 272] ===
 
=== Locality 10 [SD 907 272] ===
  
This splendid gorge in the Rough Rock allows nearly the entire 34 m thickness of the sandstone to be examined. In the upper part of the section, cross sets up to 8 m in height can be discerned — testimony to the presence of large dunes or bars that must have formed in a channel of appreciable depth.
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This splendid gorge in the Rough Rock allows nearly the entire 34 m thickness of the sandstone to be examined. In the upper part of the section, cross sets up to 8 m in height can be discerned — testimony to the presence of large dunes or bars that must have formed in a channel of appreciable depth.
  
 
== [[Yorkshire rocks and landscape: a field guide#Glossary|Glossary]] ==
 
== [[Yorkshire rocks and landscape: a field guide#Glossary|Glossary]] ==

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