Editing Craven Fault Zone — Malham to Settle - an excursion

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The Carboniferous (Dinantian, Namurian) palaeogeography of the North of England was greatly influenced by structurally controlled blocks of Lower Palaeozoic basement, which under a regime of largely extensional rifting, produced depositional settings of ramp, rimmed shelf and basin. The Craven Faults, and in particular the Middle Craven Fault (MCF), defined the southern margin of the Askrigg Block, a northward-dipping tilt-block of isostatically buoyant (granite-cored) Lower Palaeozoic basement. This block formed a site suitable for shallow water limestone deposition, and contrasted markedly with the subsiding area to the south, where deeper water environments were formed, characterized by both mudstone and limestone deposition.
 
The Carboniferous (Dinantian, Namurian) palaeogeography of the North of England was greatly influenced by structurally controlled blocks of Lower Palaeozoic basement, which under a regime of largely extensional rifting, produced depositional settings of ramp, rimmed shelf and basin. The Craven Faults, and in particular the Middle Craven Fault (MCF), defined the southern margin of the Askrigg Block, a northward-dipping tilt-block of isostatically buoyant (granite-cored) Lower Palaeozoic basement. This block formed a site suitable for shallow water limestone deposition, and contrasted markedly with the subsiding area to the south, where deeper water environments were formed, characterized by both mudstone and limestone deposition.
  
By late Dinantian times there was a clear differentiation between a rimmed carbonate shelf developed on the Askrigg Block, with marginal carbonate build-ups (the Cracoean 'reef' limestones), and the deeper water settings of the Craven Basin. These build-ups had a unique set of '''facies''' and supported a prolific invertebrate fauna. The '''dip''' of the Malham Formation in the '''hanging wall''' of the MCF is always greater than that on the adjacent '''footwall''', and implies northward rotation of the hanging wall. The rotation is a reflection of a concavity in the MCF plane, with the fault plane flattening out with depth; such fault geometries are described as listric. In detail, the Visean (late Dinantian) depositional history of the shelf-edge was complex, and involved syndepositional (extensional) 'growth faulting' along the MCF, followed by a major erosive phase instigated by a '''strike-slip''' component on the Craven faults with localized compressional effects. Mudstones of the Bowland Shales progressively covered these disrupted Dinantian limestones, burying the 'reefs' and lapping over the MCF; the Bowland Shales passing up into the siltier and sandier Pendle Grit Formation. After further structural upheaval and erosion, widespread across the Askrigg Block, the deltaic, pebbly, coarse-grained sandstones of the Grassington Grit Formation extended southwards across the Block and into the Craven Basin.
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By late Dinantian times there was a clear differentiation between a rimmed carbonate shelf developed on the Askrigg Block, with marginal carbonate build-ups (the Cracoean 'reef' limestones), and the deeper water settings of the Craven Basin. These build-ups had a unique set of facies and supported a prolific invertebrate fauna. The dip of the Malham Formation in the hanging wall of the MCF is always greater than that on the adjacent footwall, and implies northward rotation of the hanging wall. The rotation is a reflection of a concavity in the MCF plane, with the fault plane flattening out with depth; such fault geometries are described as listric. In detail, the Visean (late Dinantian) depositional history of the shelf-edge was complex, and involved syndepositional (extensional) 'growth faulting' along the MCF, followed by a major erosive phase instigated by a strike-slip component on the Craven faults with localized compressional effects. Mudstones of the Bowland Shales progressively covered these disrupted Dinantian limestones, burying the 'reefs' and lapping over the MCF; the Bowland Shales passing up into the siltier and sandier Pendle Grit Formation. After further structural upheaval and erosion, widespread across the Askrigg Block, the deltaic, pebbly, coarse-grained sandstones of the Grassington Grit Formation extended southwards across the Block and into the Craven Basin.
  
 
== Excursion details ==
 
== Excursion details ==

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