Editing Geology and landscape of Upper Teesdale - an excursion

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The end-Carboniferous Variscan Orogeny led to reactivation of basement faults and general uplift of the Northern Pennines area. A late orogenic extensional phase resulted in the injection of basic '''magma''' into deep-seated fault zones, some of which acted as feeder dykes for the extensive Whin Sill, a very important '''doleritic''' intrusion in North East England. Upper Teesdale, the southern limit of this '''igneous''' body, was where the intrusive nature of a sill was first recognized by Adam Sedgwick in 1827. The important Northern Pennines mineralization is chronologically associated with this reheating of the basement rocks of the block areas by these basic magmas (Dunham 1990). '''Mineral veins''' (base metals lead, zinc and iron with a little copper, silver and cobalt) are to be found in fault zones cutting the Carboniferous sediments and indeed replacing some of the limestones in particular. The legacy of intensive mining in the past litters the Teesdale landscape.
 
The end-Carboniferous Variscan Orogeny led to reactivation of basement faults and general uplift of the Northern Pennines area. A late orogenic extensional phase resulted in the injection of basic '''magma''' into deep-seated fault zones, some of which acted as feeder dykes for the extensive Whin Sill, a very important '''doleritic''' intrusion in North East England. Upper Teesdale, the southern limit of this '''igneous''' body, was where the intrusive nature of a sill was first recognized by Adam Sedgwick in 1827. The important Northern Pennines mineralization is chronologically associated with this reheating of the basement rocks of the block areas by these basic magmas (Dunham 1990). '''Mineral veins''' (base metals lead, zinc and iron with a little copper, silver and cobalt) are to be found in fault zones cutting the Carboniferous sediments and indeed replacing some of the limestones in particular. The legacy of intensive mining in the past litters the Teesdale landscape.
  
Post-Variscan faulting in the Teesdale area is complicated by subsequent tectonic episodes (Triassic, intra-Jurassic, early Tertiary and even late Quaternary '''eustatic''' movements) so many faults show different phases and directions of movement and there are some cases of fault inversion. Into one such fault zone were injected basic magmas believed to have originated from the early Tertiary (Palaeocene) Mull volcanic centre. This Cleveland-Armathwaite Dyke '''echelon''' is well represented in Upper Teesdale.
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Post-Variscan faulting in the Teesdale area is complicated by subsequent tectonic episodes (Triassic, intra-Jurassic, early Tertiary and even late Quaternary eustatic movements) so many faults show different phases and directions of movement and there are some cases of fault inversion. Into one such fault zone were injected basic magmas believed to have originated from the early Tertiary (Palaeocene) Mull volcanic centre. This Cleveland-Armathwaite Dyke echelon is well represented in Upper Teesdale.
  
Only features associated with the latest Quaternary (Devensian) glaciation are represented in Upper Teesdale but these have had a profound effect. Much of the landscape is masked by deposits of '''till''' which is of local (Pennine) origin except in the Lunedale and Middleton-in-Teesdale area where distinctive glacial '''erratics''' of Shap Granite and green '''andesitic tuffs''' (Borrowdale Volcanic Group) witness the passage of Lake District ice through the Stainmore pass and Lunedale area onto the South Durham–North Yorkshire plains. Geomorphological features in Upper Teesdale suggest a late Quaternary valley glacier phase with marginal '''moraines''', linear ice moulded debris, glacial '''spillways''' and modified river patterns, as well as outwash sand and gravel deposits which choke the Tees valley.
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Only features associated with the latest Quaternary (Devensian) glaciation are represented in Upper Teesdale but these have had a profound effect. Much of the landscape is masked by deposits of till which is of local (Pennine) origin except in the Lunedale and Middleton-in-Teesdale area where distinctive glacial erratics of Shap Granite and green andesitic tuffs (Borrowdale Volcanic Group) witness the passage of Lake District ice through the Stainmore pass and Lunedale area onto the South Durham–North Yorkshire plains. Geomorphological features in Upper Teesdale suggest a late Quaternary valley glacier phase with marginal moraines, linear ice moulded debris, glacial spillways and modified river patterns, as well as outwash sand and gravel deposits which choke the Tees valley.
  
 
== Excursion details ==
 
== Excursion details ==

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