Editing Upper Carboniferous of the Halifax area - an excursion

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The excursion can be completed in one short day as all the localities occur within 10 km to the south and southwest of Halifax ([[:File:YGS_YORKROCK_FIG_09_01.jpg|Figure 9.1]]) and are easily accessible by road. Very little off-road walking is required and the distances involved at individual outcrops are less than 1 km, mostly over footpaths and rough tracks. Care must be excercised when visiting outcrops in quarries and road cuttings, and hard hats are recommended for safety. Private transport is an advantage but not essential, and parking facilities are available at all localities. The excursion is not suitable for large parties.
 
The excursion can be completed in one short day as all the localities occur within 10 km to the south and southwest of Halifax ([[:File:YGS_YORKROCK_FIG_09_01.jpg|Figure 9.1]]) and are easily accessible by road. Very little off-road walking is required and the distances involved at individual outcrops are less than 1 km, mostly over footpaths and rough tracks. Care must be excercised when visiting outcrops in quarries and road cuttings, and hard hats are recommended for safety. Private transport is an advantage but not essential, and parking facilities are available at all localities. The excursion is not suitable for large parties.
  
Prior permission should be sought for access to Clockface Quarry from Marshalls, Brier Lodge, Southowram, Halifax.
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Prior permission should be sought for access to Clockface Quarry from Marshalls, Brier Lodge, Southowram, Halifax, HX3 9SY (tel. 01422 306000].
  
 
== Maps ==
 
== Maps ==
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=== Locality 3, Elland Road Cutting [SE 103 215] ===
 
=== Locality 3, Elland Road Cutting [SE 103 215] ===
  
The road cutting lies on the A629 Elland bypass (Calderdale Way), some 4 km south of Halifax town centre, and illustrates a fluvially dominated prograding delta system. Because of heavy traffic, and its location on a bend in the road, care must be taken when examining the outcrop. The safest, most convenient parking is on the extensive grass verge at the southern end of the cutting. The cutting varies in height from 15 to 30 m and can be traced laterally for some 500 m. The outcrop, which is orientated north-northeast–south-southwest, approximately parallel to the local and regional palaeoflow direction, consists of three well-defined channel sandbodies overlying finer-grained rippled sandstones and siltstones forming an overall coarsening-upward sequence ([[:File:YGS_YORKROCK_FIG_09_02.jpg|Figure 9.2]]b). The sandstones and siltstones are sharply overlain by medium-grained micaceous sandstones, internally structured by downcurrent-dipping bedding surfaces, defining downstream accreting beds, containing trough cross-stratification and occasional plane lamination. The sandstone and siltstone beds at the base of the outcrop were deposited in the distal part of a delta system with the overlying coarser-grained sands laid down in a more proximal (landward) mouth bar setting as the delta prograded basinwards.
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The road cutting lies on the A629 Elland bypass (Calderdale Way), some 4 km south of Halifax town centre, and illustrates a fluvially dominated prograding delta system. Because of heavy traffic, and its location on a bend in the road, care must be taken when examining the outcrop. The safest, most convenient parking is on the extensive grass verge at the southern end of the cutting. The cutting varies in height from 15 to 30 m and can be traced laterally for some 500 m. The outcrop, which is orientated north-northeast–south-southwest, approximately parallel to the local and regional palaeoflow direction, consists of three well-defined channel sandbodies overlying finer-grained rippled sandstones and siltstones forming an overall coarsening-upward sequence ([[:File:YGS_YORKROCK_FIG_09_02.jpg|Figure 9.2]]b). The sandstones and siltstones are sharply overlain by medium-grained micaceous sandstones, internally structured by downcurrent-dipping bedding surfaces, defining downstream accreting beds, containing trough cross-stratification and occasional plane lamination. The sandstone and siltstone beds at the base of the outcrop were deposited in the distal part of a delta system with the overlying coarser-grained sands laid down in a more proximal (landward) mouth bar setting as the delta prograded basinwards.
  
The mouth bar sands are overlain by two coarse to very coarse, mainly trough cross-stratified, erosive, channel sandbodies forming concave lenses up to 7 m thick and 300 m wide, interpreted as delta distributary channel sandbodies deposited by palaeocurrents flowing to the southeast. The top of these amalgamated sandbodies is truncated by the sediments above, or conformably overlain by a locally developed thin lens of fine sandstone and siltstone indicative of channel shifting and abandonment. The upper channel sandbody differs from those below in its multistorey sheet-like geometry and internal scour surfaces, commonly strewn with wood fragments. It is an erosively based, coarse to very coarse, granular, '''feldspathic''' sandstone, internally dominated by trough and solitary planar cross-stratification, deposited by palaeocurrents flowing south. Deformed foresets occur near the top of the outcrop.
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The mouth bar sands are overlain by two coarse to very coarse, mainly trough cross-stratified, erosive, channel sandbodies forming concave lenses up to 7 m thick and 300 m wide, interpreted as delta distributary channel sandbodies deposited by palaeocurrents flowing to the southeast. The top of these amalgamated sandbodies is truncated by the sediments above, or conformably overlain by a locally developed thin lens of fine sandstone and siltstone indicative of channel shifting and abandonment. The upper channel sandbody differs from those below in its multistorey sheet-like geometry and internal scour surfaces, commonly strewn with wood fragments. It is an erosively based, coarse to very coarse, granular, feldspathic sandstone, internally dominated by trough and solitary planar cross-stratification, deposited by palaeocurrents flowing south. Deformed foresets occur near the top of the outcrop.
  
 
The sandstone is correlated with the Rough Rock, and is thought to have been deposited in a braided river channel characterized by low to moderate discharge fluctuations. The thickness and lateral continuity of the sediments at this locality indicate that the delta supplied by this river system was probably of the shallow water, lobate type.
 
The sandstone is correlated with the Rough Rock, and is thought to have been deposited in a braided river channel characterized by low to moderate discharge fluctuations. The thickness and lateral continuity of the sediments at this locality indicate that the delta supplied by this river system was probably of the shallow water, lobate type.
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=== Locality 4, Woodside Quarry [SE 099 209] ===
 
=== Locality 4, Woodside Quarry [SE 099 209] ===
  
Easiest access to the quarry is from Woodlands Lane, off the B61 12 Holywell Green Road. The Rough Rock exposed in the quarry face consists of braided river sandbodies showing '''tectonically''' induced deformation features, and occurs at about the same stratigraphic level as the outcrop in Greetland Quarry. Good views of Greetland Quarry and especially the Elland Road cut section can he seen from this locality. The outcrop exposed in the quarry face is up to 13 m high and can be traced laterally for some 150 m. The lower part of the outcrop consists of a coarse-grained, plant-rich channel sandstone with low-angle trough cross-stratification and rare solitary planar sets, deposited by palaeocurrents flowing south-southwest. The top of the sandstone is characterized by a laterally persistent 1.5 m thick zone of deformed cross-stratification ([[:File:YGS_YORKROCK_FIG_09_02.jpg|Figure 9.2]]c) showing local flexuring of foresets, oversteepened foresets, overturned and recumbently folded foresets, and convolute foresets. The thickness and lateral persistence of this unit suggests that deformation may be related to contemporaneous tectonic activity.
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Easiest access to the quarry is from Woodlands Lane, off the B61 12 Holywell Green Road. The Rough Rock exposed in the quarry face consists of braided river sandbodies showing tectonically induced deformation features, and occurs at about the same stratigraphic level as the outcrop in Greetland Quarry. Good views of Greetland Quarry and especially the Elland Road cut section can he seen from this locality. The outcrop exposed in the quarry face is up to 13 m high and can be traced laterally for some 150 m. The lower part of the outcrop consists of a coarse-grained, plant-rich channel sandstone with low-angle trough cross-stratification and rare solitary planar sets, deposited by palaeocurrents flowing south-southwest. The top of the sandstone is characterized by a laterally persistent 1.5 m thick zone of deformed cross-stratification ([[:File:YGS_YORKROCK_FIG_09_02.jpg|Figure 9.2]]c) showing local flexuring of foresets, oversteepened foresets, overturned and recumbently folded foresets, and convolute foresets. The thickness and lateral persistence of this unit suggests that deformation may be related to contemporaneous tectonic activity.
  
  
The lower sandstone is overlain by a much coarser-grained, erosively based channel sandbody downcutting to the southwest ([[:File:YGS_YORKROCK_FIG_09_02.jpg|Figure 9.2]]c). Concentrated along the erosion surface are granules and small pebbles of '''quartz''', and shale and siltstone '''intraclasts''' and lenses, together with abundant plant material including well-preserved ''Calamites ''stems. Internally the sandstone is structured by trough cross-stratification, except at the southwestern end where it contains a 2 m thick bed of ripple cross-laminated fine sandstone with rare small trough cross-stratification ([[:File:YGS_YORKROCK_FIG_09_02.jpg|Figure 9.2]]c).
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The lower sandstone is overlain by a much coarser-grained, erosively based channel sandbody downcutting to the southwest ([[:File:YGS_YORKROCK_FIG_09_02.jpg|Figure 9.2]]c). Concentrated along the erosion surface are granules and small pebbles of quartz, and shale and siltstone intraclasts and lenses, together with abundant plant material including well-preserved ''Calamites ''stems. Internally the sandstone is structured by trough cross-stratification, except at the southwestern end where it contains a 2 m thick bed of ripple cross-laminated fine sandstone with rare small trough cross-stratification ([[:File:YGS_YORKROCK_FIG_09_02.jpg|Figure 9.2]]c).
  
 
=== Locality 5, Upper Elland Edge [SE 118 204] ===
 
=== Locality 5, Upper Elland Edge [SE 118 204] ===
  
This outcrop of a prograding shallow water delta system is best accessed by the footpath leading off the B6114 Mirfield Road by the Eurogas Depot. The outcrop is orientated north-northeast–south-southwest and consists of some 15 m of black shale coarsening upwards at the top into a 30 cm thick zone of silty shale and ripple cross-laminated micaceous siltstone and fine sandstone, sharply overlain by the 80 Yard Rock ([[:File:YGS_YORKROCK_FIG_09_02.jpg|Figure 9.2]]d) which are only accessible at the southernmost end of the outcrop. The black shales are usually finely laminated and contain ironstone nodules and nodular layers that decrease in thickness and abundance upward through the succession, a thin coal seam, and 3 thin non-marine bivalve bands ([[:File:YGS_YORKROCK_FIG_09_02.jpg|Figure 9.2]]d). The overlying 80 Yard Rock comprises fine, locally burrowed, micaceous sandstones, containing ripple cross-lamination with some plane lamination, low-angle lamination and cross-stratification deposited by currents flowing to the southwest. The sequence occurs at the top of the ''Anthraconaia lenisulcata ''non-marine bivalve '''Biozone''', and is interpreted as the prodelta shales and delta front sands of a prograding shallow water delta system.
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This outcrop of a prograding shallow water delta system is best accessed by the footpath leading off the B6114 Mirfield Road by the Eurogas Depot. The outcrop is orientated north-northeast–south-southwest and consists of some 15 m of black shale coarsening upwards at the top into a 30 cm thick zone of silty shale and ripple cross-laminated micaceous siltstone and fine sandstone, sharply overlain by the 80 Yard Rock ([[:File:YGS_YORKROCK_FIG_09_02.jpg|Figure 9.2]]d) which are only accessible at the southernmost end of the outcrop. The black shales are usually finely laminated and contain ironstone nodules and nodular layers that decrease in thickness and abundance upward through the succession, a thin coal seam, and 3 thin non-marine bivalve bands ([[:File:YGS_YORKROCK_FIG_09_02.jpg|Figure 9.2]]d). The overlying 80 Yard Rock comprises fine, locally burrowed, micaceous sandstones, containing ripple cross- lamination with some plane lamination, low-angle lamination and cross-stratification deposited by currents flowing to the southwest. The sequence occurs at the top of the ''Anthraconaia lenisulcata ''non- marine bivalve Biozone, and is interpreted as the prodelta shales and delta front sands of a prograding shallow water delta system.
  
 
== [[Yorkshire rocks and landscape: a field guide#Glossary|Glossary]] ==
 
== [[Yorkshire rocks and landscape: a field guide#Glossary|Glossary]] ==
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{{EWwalks}}
 
{{EWwalks}}
  
[[Category:Yorkshire rocks and landscape: a field guide ]]
 
 
[[Category:8. The Pennines and adjacent areas]]
 
[[Category:8. The Pennines and adjacent areas]]

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