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[[File:Lothian Geology cover.jpg|thumb|100px|right|[http://www.edinburghgeolsoc.org/p_sales.html#lothiangeology Buy the book]]]
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Dunbar – an excursion
'''By E.H. Francis. From: [[Lothian Geology: an excursion guide|Lothian geology: an excursion guide]]. Edited by A.D. McAdam and E.N.K. Clarkson. 1996.'''
 
  
=== Dunbar ===
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'''By E.H. Francis. From: Lothian geology and excursion guide. Edited by A.D. McAdam and E.N.K. Clarkson. 1996.'''
  
 
From the car parking areas at the Barracks (NT 677 791) or Victoria Harbour (NT 679 793), the walking distance is about 4 km (3 km if the Dove Rock is excluded), with 2 km to walk back through the town to the starting point.
 
From the car parking areas at the Barracks (NT 677 791) or Victoria Harbour (NT 679 793), the walking distance is about 4 km (3 km if the Dove Rock is excluded), with 2 km to walk back through the town to the starting point.
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Dove Rock is a small plug of basanite surrounded by a narrow inner zone of tuff and an outer zone of partly brecciated inwardly dipping sandstone bounded by a ring fracture. Further incipient ring fractures are seen beyond it. As similar rocks and structures can be seen elsewhere, and as the bathing pool makes access difficult, it is suggested that if time is short both this locality and the seaward side of Castle Rocks could be omitted.
 
Dove Rock is a small plug of basanite surrounded by a narrow inner zone of tuff and an outer zone of partly brecciated inwardly dipping sandstone bounded by a ring fracture. Further incipient ring fractures are seen beyond it. As similar rocks and structures can be seen elsewhere, and as the bathing pool makes access difficult, it is suggested that if time is short both this locality and the seaward side of Castle Rocks could be omitted.
 
[[File:DunbarExcursionMap.jpg|300px|thumbnail|Dunbar - excursion map.]]
 
  
 
==== 8. Castle Rocks ====
 
==== 8. Castle Rocks ====
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==== 10. Old Harbour Neck ====
 
==== 10. Old Harbour Neck ====
  
The neck underlying the Old Harbour is most clearly delineated on its eastern side where the flanking sandstones form a wall rising above the volcanic rocks. This wall, which inclines in towards the neck at between 500 and 60°, is vertically fluted and polished and represents a plane of movement cutting off the bedding. Veins of intrusion tuff can be seen in the sandstone. Followed seawards, the margin swings west beneath the Old Harbour wall and reappears between the two harbours where it has a south-westerly trend. Beneath the drawbridge on the east wall of Victoria Harbour the outer flanking sediments comprise red marls and cementstones with interbedded yellow and green tuffs. They arc crumpled and tilted steeply towards the neck, swinging round from there to dip conformably northward beneath a basalt underlying the Battery. South of the inter-harbour area the neck margin is built over but a few exposures of tuff can still be seen west and south of the Old and Victoria harbours respectively.
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The neck underlying the Old Harbour is most clearly delineated on its eastern side where the flanking sandstones form a wall rising above the volcanic rocks. This wall, which inclines in towards the neck at between 500 and 60°, is vertically fluted and polished and represents a plane of movement cutting off the bedding. Veins of intrusion tuff can be seen in the sandstone. Followed seawards, the margin swings west beneath the Old Harbour wall and reappears between the two harbours where it has a south-westerly trend. Beneath the drawbridge on the east wall of Victoria Harbour the outer flanking sediments comprise red marls and cement­stones with interbedded yellow and green tuffs. They arc crumpled and tilted steeply towards the neck, swinging round from there to dip conformably northward beneath a basalt underlying the Battery. South of the inter-harbour area the neck margin is built over but a few exposures of tuff can still be seen west and south of the Old and Victoria harbours respectively.
  
The neck filling consists of red or, locally, green lapilli-tuffs which are bedded in the north and west, where they strike parallel to the walls and dip inwards at angles ranging from 45° to vertical, East of the Old Harbour wall. However, they have a heterogeneous aspect. This derives partly from the presence, close to the margin, of basaltic blocks and masses of country rock up to 2·5 m in diameter, and partly from the breakdown of original bedding. The bedded relics, some of them intensely crumpled do not form discrete blocks, but merge instead into an apparently structureless rock. The peripheral tuffs are laced by anastomosing vein lets of hematite and there are, in addition, sills and dykes of similar material up to 60 cm thick. A linear breccia lies to the cast of the neck. It has a north-easterly alignment decreasing in width as it is traced from the margin towards low water mark. Like the linear breccia at Belhaven it is derived from the local sediments (sandstones in this instance); it occupies a faulted trough and in places contains marginally orientated blocks. By way of contrast, however, it appears to be related to the adjacent neck, for there is no well defined margin between the two, and the western part of the breccia is penetrated by red tuffs which are similar to the unbedded variety in the neck. The sandstones in the breccia and along the neck margin show typical carious weathering as described from the eastern margin of the Parade Neck.
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The neck filling consists of red or, locally, green lapilli­tuffs which are bedded in the north and west, where they strike parallel to the walls and dip inwards at angles ranging from 45° to vertical, East of the Old Harbour wall. However, they have a heterogeneous aspect. This derives partly from the presence, close to the margin, of basaltic blocks and masses of country rock up to 2·5 m in diameter, and partly from the breakdown of original bedding. The bedded relics, some of them intensely crumpled do not form discrete blocks, but merge instead into an apparently structureless rock. The peripheral tuffs are laced by anastomosing vein lets of hematite and there are, in addition, sills and dykes of similar material up to 60 cm thick. A linear breccia lies to the cast of the neck. It has a north-easterly alignment decreasing in width as it is traced from the margin towards low water mark. Like the linear breccia at Belhaven it is derived from the local sediments (sandstones in this instance); it occupies a faulted trough and in places contains marginally orientated blocks. By way of contrast, however, it appears to be related to the adjacent neck, for there is no well defined margin between the two, and the western part of the breccia is penetrated by red tuffs which are similar to the unbedded variety in the neck. The sandstones in the breccia and along the neck margin show typical carious weathering as described from the eastern margin of the Parade Neck.
  
 
==== 11. Cryptovolcanic Ring Structures ====
 
==== 11. Cryptovolcanic Ring Structures ====
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==== 14. Kirk Hill Neck ====
 
==== 14. Kirk Hill Neck ====
  
The Kirk Hill Neck is cut off to the cast by the Dunbar-Gifford Fault, but to west and south the margin is vertical and has an irregular outline. The neck filling is again similar to the tuffs of the Old Harbour and bedding is more apparent towards the margins than at the centre. The strike of the bedding is approximately parallel to the neck margin to east and west, but adjacent to the southern margin the strike is variable. The bedding is vertical in the east, but dips westwards away from the centre of the neck at 40-70° in the west. In the north-western part of the neck there is a raft of sandstone measuring 2·5 x 6 m and south-west of the raft there is a 30 cm dyke of sandstone. The latter does not contain flow-banding like the dykes of the Parade Neck. At the indented south margin, tongues of red tuff penetrate the brecciated sandstone wall-rock and the yellow lapilli in this tuff are clearly aligned in flow structure against the sandstone.
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The Kirk Hill Neck is cut off to the cast by the Dunbar­-Gifford Fault, but to west and south the margin is vertical and has an irregular outline. The neck filling is again similar to the tuffs of the Old Harbour and bedding is more apparent towards the margins than at the centre. The strike of the bedding is approximately parallel to the neck margin to east and west, but adjacent to the southern margin the strike is variable. The bedding is vertical in the east, but dips west­wards away from the centre of the neck at 40-70° in the west. In the north-western part of the neck there is a raft of sandstone measuring 2·5 x 6 m and south-west of the raft there is a 30 cm dyke of sandstone. The latter does not contain flow-banding like the dykes of the Parade Neck. At the indented south margin, tongues of red tuff penetrate the brecciated sandstone wall-rock and the yellow lapilli in this tuff are clearly aligned in flow structure against the sandstone.
 
 
{{EGwalks}}
 
 
 
 
 
[[category:5. Midland Valley of Scotland]]
 

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