Editing Acadian Orogeny, Devonian, Northern England

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== Skiddaw Group structure ==
 
== Skiddaw Group structure ==
The dominant structural feature is a series of polyphase fault-and-thrust zones that trend approximately east-north-east across the main Skiddaw Group outcrop, roughly parallel to the regional strike of bedding and cleavage. Of these, the Causey Pike Fault has the longest demonstrable history and a geographical extent that spans the main Lake District inlier and extends as far as the Cross Fell inlier 30 km to the east. It has a profound stratigraphical effect (equivalent to at least 2 km vertical downthrow to the south), separating discrete parts of the Skiddaw Group succession with marked differences in sedimentary provenance and slump-fold orientation; hence it may well have had a synsedimentary role, partitioning the original depositional basin. Some sinistral strike-slip movement seems likely during the Early Devonian transpressive phase, whilst south-directed thrust movement cutting across the approximately 400 Ma Crummock Water thermal aureole is likely to be an Acadian (sensu stricto) effect.
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The dominant structural feature is a series of polyphase fault-and-thrust zones that trend approximately east-north-east across the main Skiddaw Group outcrop, roughly parallel to the regional strike of bedding and cleavage. Of these, the Causey Pike Fault has the longest demonstrable history and a geographical extent that spans the main Lake District inlier and extends as far as the Cross Fell inlier 30<br>km to the east. It has a profound stratigraphical effect (equivalent to at least 2<br>km vertical downthrow to the south), separating discrete parts of the Skiddaw Group succession with marked differences in sedimentary provenance and slump-fold orientation; hence it may well have had a synsedimentary role, partitioning the original depositional basin. Some sinistral strike-slip movement seems likely during the Early Devonian transpressive phase, whilst south-directed thrust movement cutting across the approximately 400 Ma Crummock Water thermal aureole is likely to be an Acadian (sensu stricto) effect.
  
 
Farther north, the Gasgale, Loweswater and Watch Hill thrust faults were all most probably initiated as the slide planes of large-scale, synsedimentary slumps. Thereafter, subsequent reactivation during Acadian deformation has created a situation such that, in the hanging walls, minor, upright folds have an axial-plane cleavage that progressively swings into an alignment parallel with the thrust plane, but is then crenulated by a uniformly shallow-dipping cleavage. The Watch Hill thrust is a particularly complex structure and is most probably a compound plexus of faults having different attitudes, movement senses, and ages.
 
Farther north, the Gasgale, Loweswater and Watch Hill thrust faults were all most probably initiated as the slide planes of large-scale, synsedimentary slumps. Thereafter, subsequent reactivation during Acadian deformation has created a situation such that, in the hanging walls, minor, upright folds have an axial-plane cleavage that progressively swings into an alignment parallel with the thrust plane, but is then crenulated by a uniformly shallow-dipping cleavage. The Watch Hill thrust is a particularly complex structure and is most probably a compound plexus of faults having different attitudes, movement senses, and ages.

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