Editing Carboniferous rocks of the Roman Wall and Haltwhistle Burn - an excursion

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=== Sewing Shields–Cawfields ===
 
=== Sewing Shields–Cawfields ===
  
From Newcastle, take the A69 to Heddon on the Wall. Turn onto the B6318 (Military Road), which from Heddon to Chollerford is almost wholly along the foundations of the Roman Wall. The ditch on the north side and the vallum with the two accompanying mounds on the south can often be clearly seen. Continue westwards, until beyond the fort of Carrawburgh ''(Brocolitia) [NY  859 712]'', the dip and scarp topography of the 'Roman Wall Area' is seen ahead. At Turret T33B [NY 821 706] the road leaves the line of the wall which climbs up to the scarp edge of the Whin Sill at Sewing Shields.
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From Newcastle, take the A69 to Heddon on the Wall. Turn onto the B6318 (Military Road), which from Heddon to Chollerford is almost wholly along the foundations of the Roman Wall. The ditch on the north side and the vallum with the two accompanying mounds on the south can often be clearly seen. Continue westwards, until beyond the fort of Carrawburgh ''(Brocolitia) [NY 859 712]'', the dip and scarp topography of the 'Roman Wall Area' is seen ahead. At Turret T33B [NY 821 706] the road leaves the line of the wall which climbs up to the scarp edge of the Whin Sill at Sewing Shields.
  
 
==== Locality 1 ====
 
==== Locality 1 ====
  
From the telephone exchange on the south side of the road [NY 816 702], the view west consists of the Whin escarpment, overlain on the lower part of the slope by the Scar Limestone, a peat filled depression, then the conspicuous scarp of the sandstone between the Scar and Five Yard Limestones which the road traverses ([[:File:YGS_NORTROCK_FIG_11_1.jpg|Figure 11.1]]). Westwards, the scarp and outcrop of the Five Yard Limestone runs parallel to the south side of the road as far as Moss Kennels [NY 803 691] just west of which the features break down which suggests '''faulting'''. Although no fracture has been located, the Whin to the north shows a large break in outcrop and transgression at this point. Housesteads ''(Vercovicium) [NY 793 784]'' can be seen 1 km west on the dip slope of the Whin. The car park is built on the scarp of the sandstone between the Five and Three Yard Limestones and the road continues at this level. To the north the scenery is dominated by the top surface of the Whin, dipping at about 12°, and to the south by the strong scarp feature of the sandstone between the Three Yard and Four Fathom Limestones. Only the upper half of the scarp feature is composed of sandstone, a marked change in vegetation indicating the junction with the underlying shale. The top of the Three Yard Limestone can be seen at the west end of the escarpment [NY 783 676]. The Whin Sill escarpment is heavily indented, particularly at the site of Milecastle 39 [NY 760 767] which has recently been excavated and consolidated. The indentations are probably due to small faults crossing the sill which tend to shatter and weaken the brittle '''dolerite'''. The most westerly of the indentations is larger and better defined [NY 753 675] and can clearly be seen to have acted as a water channel at the end of the last glaciation, draining a lake which lay on the north side of the escarpment, a remnant of which persists as Crag Lough.
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From the telephone exchange on the south side of the road [NY 816 702], the view west consists of the Whin escarpment, overlain on the lower part of the slope by the Scar Limestone, a peat filled depression, then the conspicuous scarp of the sandstone between the Scar and Five Yard Limestones which the road traverses ([[:File:YGS_NORTROCK_FIG_11_1.jpg|Figure 11.1]]). Westwards, the scarp and outcrop of the Five Yard Limestone runs parallel to the south side of the road as far as Moss Kennels [NY 803 691] just west of which the features break down which suggests faulting. Although no fracture has been located, the Whin to the north shows a large break in outcrop and transgression at this point. Housesteads ''(Vercovicium) [NY 793 784]'' can be seen 1 km west on the dip slope of the Whin. The car park is built on the scarp of the sandstone between the Five and Three Yard Limestones and the road continues at this level. To the north the scenery is dominated by the top surface of the Whin, dipping at about 12°, and to the south by the strong scarp feature of the sandstone between the Three Yard and Four Fathom Limestones. Only the upper half of the scarp feature is composed of sandstone, a marked change in vegetation indicating the junction with the underlying shale. The top of the Three Yard Limestone can be seen at the west end of the escarpment [NY 783 676]. The Whin Sill escarpment is heavily indented, particularly at the site of Milecastle 39 [NY 760 767] which has recently been excavated and consolidated. The indentations are probably due to small faults crossing the sill which tend to shatter and weaken the brittle dolerite. The most westerly of the indentations is larger and better defined [NY 753 675] and can clearly be seen to have acted as a water channel at the end of the last glaciation, draining a lake which lay on the north side of the escarpment, a remnant of which persists as Crag Lough.
  
 
==== Locality 2 ====
 
==== Locality 2 ====

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