Eyemouth - an excursion - Revision history

Scotfot at 21:50, 6 November 2015

2015-11-06T21:50:04Z

← Older revision		Revision as of 22:50, 6 November 2015
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	'''By D.C.Greig. From Scottish Borders geology: an excursion guide edited by A.D. McAdam, E.N.K. Clarkson, P. Stone. Edinburgh : Scottish Academic Press (for [http://www.edinburghgeolsoc.org/ Edinburgh Geological Society]), 1992.'''		'''By D.C.Greig. From [[Scottish Borders geology: an excursion guide]] edited by A.D. McAdam, E.N.K. Clarkson, P. Stone. Edinburgh : Scottish Academic Press (for [http://www.edinburghgeolsoc.org/ Edinburgh Geological Society]), 1992.'''

	O.S. 1:50 000 Sheet 67 Duns and Dunbar		O.S. 1:50 000 Sheet 67 Duns and Dunbar

JenniferFindlay1 at 19:07, 27 July 2015

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	==== 2. Hairy Ness<ref>The headland of Hairy Ness may be taken as the first locality, reached by a shorter path along the seaward side of the large caravan site, between it and Eyemouth Fort.</ref> : Lava and Agglomerate ====		==== 2. Hairy Ness<ref>The headland of Hairy Ness may be taken as the first locality, reached by a shorter path along the seaward side of the large caravan site, between it and Eyemouth Fort.</ref> : Lava and Agglomerate ====
	The rocks forming the cliffs east of the bay, leading north-eastwards to ~~HairyNess1~~ appear to be mainly andesitic lava but coarse agglomerate is seen at many points. In places the two rock-types alternate in bands upwards of 3 m thick, but no consistent direction of dip has been observed. The lavas differ from those of St Abb's Head in the common occurrence of small phenocrysts of plagioclase feldspar. The altered ferromagnesian phenocrysts are most commonly after pyroxenes, but at the headland of Hairy Ness hornblende predominates, in unusually well-banded rock. The agglomerates are most clearly recognised on the clean sea-washed intertidal rocks, since, being made up largely of lava fragments, their clastic character is readily concealed at higher levels by weathering or the growth of lichen. Many of them are believed to be auto-breccias, broken up by the irregular movement of the partly solidified lava-flow. The rocks are much faulted by fractures running ENE and, on the west-facing cliff, by others running NNE, parallel to the cliff-line. The development of the headland, and the absence of an extensive foreshore as in the bay to west, underline the difference between the more durable lavas and agglomerates and the heterogeneous and broken rocks of the volcanic vent, whose limit is drawn close to the foot of the cliff along the south-eastern end of the bay. Within 100 m or so south-west of Hairy Ness many fractures are seen in the lava, and at one point a north-westward dip is indicated by both flow-banding and the orientation of the apparent base of a flow. Just south-east of this point, on the east-facing cliff, is a rectangular exposure of agglomerate at least 20 m by 40 m in area. Calcite veins are common in the adjacent lavas. The intertidal platform south of Hairy Ness is composed mainly of lava, locally amygdaloidal, varying in hardness and resistance to erosion, locally closely jointed, and with pockets of agglomerate.		[[File:P000809.jpg\|300px\|thumbnail\|left\|Oblique aerial view of Hairy Ness, Eyemouth taken from the north-east. Berwickshire. The headland is made up of andesitic and basaltic lavas of Lower Old Red Sandstone age with some beds of coarse agglomerate. The less prominent rocks of Killiedraught Bay on the right, are a mixed volcanic assemblage probably filling an old volcanic vent. The outskirts of Eyemouth can be seen beyond the headland. P000809]]The rocks forming the cliffs east of the bay, leading north-eastwards to Hairy Ness appear to be mainly andesitic lava but coarse agglomerate is seen at many points. In places the two rock-types alternate in bands upwards of 3 m thick, but no consistent direction of dip has been observed. The lavas differ from those of St Abb's Head in the common occurrence of small phenocrysts of plagioclase feldspar. The altered ferromagnesian phenocrysts are most commonly after pyroxenes, but at the headland of Hairy Ness hornblende predominates, in unusually well-banded rock. The agglomerates are most clearly recognised on the clean sea-washed intertidal rocks, since, being made up largely of lava fragments, their clastic character is readily concealed at higher levels by weathering or the growth of lichen. Many of them are believed to be auto-breccias, broken up by the irregular movement of the partly solidified lava-flow. The rocks are much faulted by fractures running ENE and, on the west-facing cliff, by others running NNE, parallel to the cliff-line. The development of the headland, and the absence of an extensive foreshore as in the bay to west, underline the difference between the more durable lavas and agglomerates and the heterogeneous and broken rocks of the volcanic vent, whose limit is drawn close to the foot of the cliff along the south-eastern end of the bay. Within 100 m or so south-west of Hairy Ness many fractures are seen in the lava, and at one point a north-westward dip is indicated by both flow-banding and the orientation of the apparent base of a flow. Just south-east of this point, on the east-facing cliff, is a rectangular exposure of agglomerate at least 20 m by 40 m in area. Calcite veins are common in the adjacent lavas. The intertidal platform south of Hairy Ness is composed mainly of lava, locally amygdaloidal, varying in hardness and resistance to erosion, locally closely jointed, and with pockets of agglomerate.

	==== 3. Eyemouth Fort: Upper Old Red Sandstone ====		==== 3. Eyemouth Fort: Upper Old Red Sandstone ====
	To the east the cliffs below Eyemouth Fort are capped by a brighter red rock, a coarse conglomerate with bands of sandstone, of the Devono-Carboniferous Upper Old Red Sandstone. On a northward promontory near the western end of the outcrop 12 m of this rock is exposed, overlying slabby-jointed purple lava in the lower part of the cliff. The sediments consist largely of conglomerate, including angular fragments of purple lava and pale green sandstone, with a lenticular bed of cross-bedded sandstone between 2.5 and 5 m. from the top. The junction with the lavas is generally flat-lying, with local variations, as on the western side of the promontory, where it dips to south-east at 45°, and on the headland, where it rises abruptly to the north-East of the promontory the level of the base falls and conglomerate is extensively exposed on the rocky foreshore north of the cliffs. The process is interrupted by a 9-m NNE fault along the east side of the bay east of the promontory, which raises the lavas to the level of the base of the cliffs. Within a further 50 m to the east however the base of the conglomerate descends and swings across the foreshore to north, cutting off the outcrop of the lavas. For 75 m along the cliff, within 100 m west of the main headland, lava crops out in narrow inliers bounded to north and west by faults striking ENE and NNE, parallel to others seen farther to west. At most states of the tide it will be advisable, if not necessary, to retrace one's steps to the west, regain the cliff-top and descend on the south side of the Fort by a rough rocky path in the embayment 170 m south-west of the northwards headland. A scramble 80 m northwards among the very large fallen blocks of conglomerate at the foot of the cliff will bring one to a fine exposure of the unconformity of the conglomerate on purple lava. The conglomerate includes many clasts of pink 'porphyry' up to 0.6 m in size, as well as of green and brown sandstone, and there are a few lenticular bands of cross-bedded sandstone up to 1.5 m thick. Slabby jointing is a notable feature in the underlying lavas. Both rocks are cut by calcite veins, and secondary tufa has been precipitated at several points from the conglomerate. In this area the base of the conglomerate drops gradually northwards.[[File:P005900.jpg\|thumb\|200px\|right\|Eyemouth Fort. SW view. Glacial deposits. Boulder clay rests on bedded gravel with thick band of bedded sand. On left the lower beds abut against pale purple lavas of Lower Old Red Sandstone age, marking the south-east limit of a channel. The drift deposits are c. 13 m. thick.[http://194.66.252.158/asset-bank/action/viewAsset?id=5149 P005900]]]		To the east the cliffs below Eyemouth Fort are capped by a brighter red rock, a coarse conglomerate with bands of sandstone, of the Devono-Carboniferous Upper Old Red Sandstone. On a northward promontory near the western end of the outcrop 12 m of this rock is exposed, overlying slabby-jointed purple lava in the lower part of the cliff. The sediments consist largely of conglomerate, including angular fragments of purple lava and pale green sandstone, with a lenticular bed of cross-bedded sandstone between 2.5 and 5 m. from the top. [[File:P005900.jpg\|thumb\|300px\|right\|Eyemouth Fort. SW view. Glacial deposits. Boulder clay rests on bedded gravel with thick band of bedded sand. On left the lower beds abut against pale purple lavas of Lower Old Red Sandstone age, marking the south-east limit of a channel. The drift deposits are c. 13 m. thick.[http://194.66.252.158/asset-bank/action/viewAsset?id=5149 P005900]]]The junction with the lavas is generally flat-lying, with local variations, as on the western side of the promontory, where it dips to south-east at 45°, and on the headland, where it rises abruptly to the north-East of the promontory the level of the base falls and conglomerate is extensively exposed on the rocky foreshore north of the cliffs. The process is interrupted by a 9-m NNE fault along the east side of the bay east of the promontory, which raises the lavas to the level of the base of the cliffs. Within a further 50 m to the east however the base of the conglomerate descends and swings across the foreshore to north, cutting off the outcrop of the lavas. For 75 m along the cliff, within 100 m west of the main headland, lava crops out in narrow inliers bounded to north and west by faults striking ENE and NNE, parallel to others seen farther to west. At most states of the tide it will be advisable, if not necessary, to retrace one's steps to the west, regain the cliff-top and descend on the south side of the Fort by a rough rocky path in the embayment 170 m south-west of the northwards headland. A scramble 80 m northwards among the very large fallen blocks of conglomerate at the foot of the cliff will bring one to a fine exposure of the unconformity of the conglomerate on purple lava. The conglomerate includes many clasts of pink 'porphyry' up to 0.6 m in size, as well as of green and brown sandstone, and there are a few lenticular bands of cross-bedded sandstone up to 1.5 m thick. Slabby jointing is a notable feature in the underlying lavas. Both rocks are cut by calcite veins, and secondary tufa has been precipitated at several points from the conglomerate. In this area the base of the conglomerate drops gradually northwards.
	The lavas to the south are predominantly agglomeratic and include brecciated dacite, the most acid of all these St Abbs-Eyemouth rocks. It is well exposed on a minor promontory below the southern limit of the conglomerate, where it is developed as an accumulation of disoriented subangular blocks of rather soft greyish rock with prominent flow-oriented small feldspars. Small knots of malachite occur locally. This auto-brecciated lava is highly homogeneous, but the exposures scattered across the foreshore to south consist most commonly of blocks of lava embedded in an igneous matrix C At one point on the cliff the volcanic rocks are channelled by a sequence of gravel and sand 10 m thick, overlain by 3 m of boulder clay. The lower deposits, in part clearly stratified and showing some rounding of pebbles, are considered to mark the course of a stream prior to the last (Devensian) glaciation.		The lavas to the south are predominantly agglomeratic and include brecciated dacite, the most acid of all these St Abbs-Eyemouth rocks. It is well exposed on a minor promontory below the southern limit of the conglomerate, where it is developed as an accumulation of disoriented subangular blocks of rather soft greyish rock with prominent flow-oriented small feldspars. Small knots of malachite occur locally. This auto-brecciated lava is highly homogeneous, but the exposures scattered across the foreshore to south consist most commonly of blocks of lava embedded in an igneous matrix C At one point on the cliff the volcanic rocks are channelled by a sequence of gravel and sand 10 m thick, overlain by 3 m of boulder clay. The lower deposits, in part clearly stratified and showing some rounding of pebbles, are considered to mark the course of a stream prior to the last (Devensian) glaciation.

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	==== 5. John's Roads and Agate Point: Folded Greywackes ====		==== 5. John's Roads and Agate Point: Folded Greywackes ====
	From Elgy Rocks return southward along the cliff-top. From a point nearly opposite the end of the playing field track an open anticline can be seen on the shore below in which both limbs are nearly vertical and the hinge plunges steeply northwards. The angle between the bedding and the axial-plane cleavage in some of the beds is maintained across this fold, the cleavage being related to the widely prevalent WSW-plunging folds, which in this example seem to have been refolded by the strike-slip shear event. Southwards for 100 m, to the head of the inlet south-west of John's Roads, a general anticlinal structure may be followed on the foreshore, with steep plunge both to north and, downward-facing, to south. This north-south line of folding, with associated faulting, marks the western limit of a zone of complicated structure which extends 160 m to east, to Agate Point, whence a parallel fault, sinistral or reversed, can be traced southwards to an inlet 180 m west of Whalt Point. On the minor headland west of Agate Point the spectacular structures result from interference of essentially ENE-WSW (Caledonoid) compression and penecontemporaneous strike-slip shear. Later faulting causes further complications. At the seaward end of the headland at least 6 folds are seen, plunging to NE at 25°, which, by a study of grading in the greywackes and few ill-defined under-surface structures, can readily be shown to be downward-facing. A cross-strike fault cuts these folds within a few metres to south-west, beyond which point concentric fold axes are seen, varying in plunge from south-westward through vertical to north-eastward. Different parts of this variation are seen on opposite sides of the promontory. The prima facie interpretation is that the downward-facing folds, plunging to NE, have been overfolded along their axes from SW to NE. If however the inversion of the folds and the overfolding are ascribed to one stage the direction of overfolding is seen to be from NE to SW.		[[File:P218976.jpg\|300px\|thumbnail\|left\|Eyemouth, Agate Point. Downward view to N. Folds in Silurian greywacke. The rounded crest of an anticline in centre plunges almost vertically to south-west. The figure is standing on the axis of a tight syncline with a more gentle parallel plunge. P218976]]From Elgy Rocks return southward along the cliff-top. From a point nearly opposite the end of the playing field track an open anticline can be seen on the shore below in which both limbs are nearly vertical and the hinge plunges steeply northwards. The angle between the bedding and the axial-plane cleavage in some of the beds is maintained across this fold, the cleavage being related to the widely prevalent WSW-plunging folds, which in this example seem to have been refolded by the strike-slip shear event. Southwards for 100 m, to the head of the inlet south-west of John's Roads, a general anticlinal structure may be followed on the foreshore, with steep plunge both to north and, downward-facing, to south. This north-south line of folding, with associated faulting, marks the western limit of a zone of complicated structure which extends 160 m to east, to Agate Point, whence a parallel fault, sinistral or reversed, can be traced southwards to an inlet 180 m west of Whalt Point. On the minor headland west of Agate Point the spectacular structures result from interference of essentially ENE-WSW (Caledonoid) compression and penecontemporaneous strike-slip shear. Later faulting causes further complications. At the seaward end of the headland at least 6 folds are seen, plunging to NE at 25°, which, by a study of grading in the greywackes and few ill-defined under-surface structures, can readily be shown to be downward-facing. A cross-strike fault cuts these folds within a few metres to south-west, beyond which point concentric fold axes are seen, varying in plunge from south-westward through vertical to north-eastward. Different parts of this variation are seen on opposite sides of the promontory. The prima facie interpretation is that the downward-facing folds, plunging to NE, have been overfolded along their axes from SW to NE. If however the inversion of the folds and the overfolding are ascribed to one stage the direction of overfolding is seen to be from NE to SW.

	These structures were first described in detail by Dearman and others (1962, p.279)<ref>Dearman, W.R., Shiells, K.A.G.,and Larwood, G.P. 1962. Refolded folds in the Silurian rocks of Eyemouth, Berwickshire. Proc. Yorks. Geol. Soc. 33, 373-268.</ref>, as were those at Agate Point, 100 m to east, where a close series of folds on NE axes also exhibits extreme and locally abrupt variations in plunge. Where the plunge is to NE the folds are seen to be downward-facing, in contrast to upward-facing folds which plunge towards SW. Vertical fold hinges are locally prominent, and faults are abundant both, across and parallel to the fold trend. As at John's Roads, and more obviously here, the secondary overturning of the folds is from NE to SW. At neither locality are the details of structural complexity immediately apparent. Towards the south-east side of Agate Point, and for 200 m to the south, several intrusions of porphyrite or lamprophyre may be seen. They vary between 30 cm and 1 m in thickness and some are not readily distinguishable from the greywackes, being approximately concordant with the bedding.		These structures were first described in detail by Dearman and others (1962, p.279)<ref>Dearman, W.R., Shiells, K.A.G.,and Larwood, G.P. 1962. Refolded folds in the Silurian rocks of Eyemouth, Berwickshire. Proc. Yorks. Geol. Soc. 33, 373-268.</ref>, as were those at Agate Point, 100 m to east, where a close series of folds on NE axes also exhibits extreme and locally abrupt variations in plunge. Where the plunge is to NE the folds are seen to be downward-facing, in contrast to upward-facing folds which plunge towards SW. Vertical fold hinges are locally prominent, and faults are abundant both, across and parallel to the fold trend. As at John's Roads, and more obviously here, the secondary overturning of the folds is from NE to SW. At neither locality are the details of structural complexity immediately apparent. Towards the south-east side of Agate Point, and for 200 m to the south, several intrusions of porphyrite or lamprophyre may be seen. They vary between 30 cm and 1 m in thickness and some are not readily distinguishable from the greywackes, being approximately concordant with the bedding.

	==== 6. Whalt Point - Dove Cave: Folded Greywackes ====		==== 6. Whalt Point - Dove Cave: Folded Greywackes ====
	Southwards from the complexities of Agate Point to Whalt Point the strata are more regularly folded, with hinge plunges between 75° SW and vertical. These folds can readily be studied by descending the steep cliffs south of Whalt Point, where the strata, mainly dipping into the cliff, offer good holds for hands and feet, and only a modicum of agility is needed to attain the tide-line. Folding is repeated at close intervals, on average every 3 or 4 m, the NW-facing limbs being rather wider and less steep than those facing SE, the respective dips being around 70° NW as against 90°, or overturned in some cases. The folds plunge consistently to WSW at between 40° and 70°. The total effect is of a succession of asymmetric anticline-syncline fold pairs in beds dipping generally at a high angle towards the north-west. In any one fold pair the anticline is to the north of the syncline; the folds are therefore often described as south-verging. Most of the beds have been folded without change of thickness, in a parallel manner, but in many cases the thinner, finer-grained members have been distorted near the fold axis, by extenuation along the axial plane or by multiple folding. Axial-plane faulting seems to be of little significance, but some beds of greywacke are conspicuously brecciated near fold axes. These conditions can be readily examined between Whalt Point and Dove Cave and are known to persist as far as Fancove Head, beyond which point the structures are obscured by igneous intrusions.		Southwards from the complexities of Agate Point to Whalt Point the strata are more regularly folded, with hinge plunges between 75° SW and vertical. [[File:P002933.jpg\|300px\|thumbnail\|right\|Oblique aerial view from the east-south-east taken at Whalt Point - Willie Anderson, Eyemouth shore, Berwickshire. The rocks, typical turbidites, are an alternating series of greywackes and siltstones in beds seldom exceeding 0.5 m. in thickness. They are predominantly grey in colour. The folds in the rocks north of Whalt Point are markedly more complex than the folds south of the point. The folding occurred during the Caledonian Orogeny towards the end of the Silurian, the geosyncline, a large sedimentary basin was compressed from the north-north-west and south-south-east, folded, faulted, and elevated to form a chain of mountains which have subsequently been eroded. A typical coastal view showing faulted Silurian greywackes, the faults are picked out by erosion, the strike of beds is north-east - south-west. P002933]]These folds can readily be studied by descending the steep cliffs south of Whalt Point, where the strata, mainly dipping into the cliff, offer good holds for hands and feet, and only a modicum of agility is needed to attain the tide-line. Folding is repeated at close intervals, on average every 3 or 4 m, the NW-facing limbs being rather wider and less steep than those facing SE, the respective dips being around 70° NW as against 90°, or overturned in some cases. The folds plunge consistently to WSW at between 40° and 70°. The total effect is of a succession of asymmetric anticline-syncline fold pairs in beds dipping generally at a high angle towards the north-west. In any one fold pair the anticline is to the north of the syncline; the folds are therefore often described as south-verging. Most of the beds have been folded without change of thickness, in a parallel manner, but in many cases the thinner, finer-grained members have been distorted near the fold axis, by extenuation along the axial plane or by multiple folding. Axial-plane faulting seems to be of little significance, but some beds of greywacke are conspicuously brecciated near fold axes. These conditions can be readily examined between Whalt Point and Dove Cave and are known to persist as far as Fancove Head, beyond which point the structures are obscured by igneous intrusions.

	==== 7. Scout Cave: Dolerite Dyke ====		==== 7. Scout Cave: Dolerite Dyke ====

Scotfot: /* Excursion B. East of Eyemouth */

2015-03-08T17:35:50Z

Excursion B. East of Eyemouth

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	For the part of the excursion east of Eyemouth vehicles may be most conveniently parked on the east side of the harbour, near its mouth and the old mansion of Gunsgreen (NT 9475 6437), reached by turning left off the road to Berwick immediately after crossing the river. Gunsgreen can be reached on foot from the town by following the quays round the harbour.		For the part of the excursion east of Eyemouth vehicles may be most conveniently parked on the east side of the harbour, near its mouth and the old mansion of Gunsgreen (NT 9475 6437), reached by turning left off the road to Berwick immediately after crossing the river. Gunsgreen can be reached on foot from the town by following the quays round the harbour.

	The Silurian rocks which occupy the coast between Eyemouth and Burnmouth are greywackes and siltstones of the Hawick Group, highly folded and faulted, occurring in beds generally less than 1 m thick and notably thinner than in the Fast Castle Gala Group outcrop. The Hawick Group rocks are also on average more finely grained, have a higher proportion of quartz grains to feldspathic and lithic fragments, and are more commonly bound by a calcareous cement. Interbedded red mudstone is also a characteristic feature of the Hawick Group succession in the Eyemouth area. The folding of the Eyemouth rocks is more complex than the relatively simple succession of broad synclines and anticlines which characterises the northern outcrop. The dominant pattern of NW-SE (Caledonoid) compression continued, but superimposed on it was contemporaneous sinistral strike-slip shear vector; the combined effect was a system of fold hinges showing marked changes in plunge along their length. Some spectacular examples of hinge plunge variation are seen in the Eyemouth section. It should be stressed that they are not the product of two discrete superimposed fold episodes but rather record the variable interaction of compressive and strike-slip movements. However, there are some examples of steeply plunging hinges about which the cleavage and more gently-plunging hinges are folded. These steep structures are related entirely to the strikeslip shear event and usually have a sinistral sense. Sedimentation structures are similar to those described in the Fast Castle rocks, and the main source of sediment appears statistically to have lain to ENE. No fossils have yet been recorded from this outcrop, a feature which, added to certain lithological characteristics, reinforces the correlation with the Silurian Hawick Group of other parts of southern Scotland (Greig 1988).		The Silurian rocks which occupy the coast between Eyemouth and Burnmouth are greywackes and siltstones of the Hawick Group, highly folded and faulted, occurring in beds generally less than 1 m thick and notably thinner than in the Fast Castle Gala Group outcrop. The Hawick Group rocks are also on average more finely grained, have a higher proportion of quartz grains to feldspathic and lithic fragments, and are more commonly bound by a calcareous cement. Interbedded red mudstone is also a characteristic feature of the Hawick Group succession in the Eyemouth area. The folding of the Eyemouth rocks is more complex than the relatively simple succession of broad synclines and anticlines which characterises the northern outcrop. The dominant pattern of NW-SE (Caledonoid) compression continued, but superimposed on it was contemporaneous sinistral strike-slip shear vector; the combined effect was a system of fold hinges showing marked changes in plunge along their length. Some spectacular examples of hinge plunge variation are seen in the Eyemouth section. It should be stressed that they are not the product of two discrete superimposed fold episodes but rather record the variable interaction of compressive and strike-slip movements. However, there are some examples of steeply plunging hinges about which the cleavage and more gently-plunging hinges are folded. These steep structures are related entirely to the strikeslip shear event and usually have a sinistral sense. Sedimentation structures are similar to those described in the Fast Castle rocks, and the main source of sediment appears statistically to have lain to ENE. No fossils have yet been recorded from this outcrop, a feature which, added to certain lithological characteristics, reinforces the correlation with the Silurian Hawick Group of other parts of southern Scotland (Greig 1988)<ref>Greig, D.C. 1988. Geology of the Eyemouth district. Mem. Brit. Geol. Surv. Hutton, J. 1795. Theory of the Earth. William Creech, Edinburgh.</ref>.

	==== 4. Elgy Rocks: Folded Greywackes ====		==== 4. Elgy Rocks: Folded Greywackes ====

Scotfot at 17:34, 8 March 2015

2015-03-08T17:34:23Z

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	'''By D.C.Greig. From Scottish Borders geology: an excursion guide edited by A.D. McAdam, E.N.K. Clarkson, P. Stone. Edinburgh : Scottish Academic Press (for [http://www.edinburghgeolsoc.org/ Edinburgh Geological Society]), ~~1972~~.'''		'''By D.C.Greig. From Scottish Borders geology: an excursion guide edited by A.D. McAdam, E.N.K. Clarkson, P. Stone. Edinburgh : Scottish Academic Press (for [http://www.edinburghgeolsoc.org/ Edinburgh Geological Society]), 1992.'''

	O.S. 1:50 000 Sheet 67 Duns and Dunbar		O.S. 1:50 000 Sheet 67 Duns and Dunbar

Scotfot at 21:59, 7 March 2015

2015-03-07T21:59:54Z

← Older revision		Revision as of 22:59, 7 March 2015
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	'''By D.C.Greig. From Scottish Borders geology: an excursion guide edited by A.D. McAdam, E.N.K. Clarkson, P. Stone. Edinburgh : Scottish Academic Press, 1972.'''		'''By D.C.Greig. From Scottish Borders geology: an excursion guide edited by A.D. McAdam, E.N.K. Clarkson, P. Stone. Edinburgh : Scottish Academic Press (for [http://www.edinburghgeolsoc.org/ Edinburgh Geological Society]), 1972.'''

	O.S. 1:50 000 Sheet 67 Duns and Dunbar		O.S. 1:50 000 Sheet 67 Duns and Dunbar

Scotfot: /* 3. Eyemouth Fort: Upper Old Red Sandstone */

2015-03-07T21:51:17Z

3. Eyemouth Fort: Upper Old Red Sandstone

← Older revision		Revision as of 22:51, 7 March 2015
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	==== 3. Eyemouth Fort: Upper Old Red Sandstone ====		==== 3. Eyemouth Fort: Upper Old Red Sandstone ====
	To the east the cliffs below Eyemouth Fort are capped by a brighter red rock, a coarse conglomerate with bands of sandstone, of the Devono-Carboniferous Upper Old Red Sandstone. On a northward promontory near the western end of the outcrop 12 m of this rock is exposed, overlying slabby-jointed purple lava in the lower part of the cliff. The sediments consist largely of conglomerate, including angular fragments of purple lava and pale green sandstone, with a lenticular bed of cross-bedded sandstone between 2.5 and 5 m. from the top. The junction with the lavas is generally flat-lying, with local variations, as on the western side of the promontory, where it dips to south-east at 45°, and on the headland, where it rises abruptly to the north-East of the promontory the level of the base falls and conglomerate is extensively exposed on the rocky foreshore north of the cliffs. The process is interrupted by a 9-m NNE fault along the east side of the bay east of the promontory, which raises the lavas to the level of the base of the cliffs. Within a further 50 m to the east however the base of the conglomerate descends and swings across the foreshore to north, cutting off the outcrop of the lavas. For 75 m along the cliff, within 100 m west of the main headland, lava crops out in narrow inliers bounded to north and west by faults striking ENE and NNE, parallel to others seen farther to west. At most states of the tide it will be advisable, if not necessary, to retrace one's steps to the west, regain the cliff-top and descend on the south side of the Fort by a rough rocky path in the embayment 170 m south-west of the northwards headland. A scramble 80 m northwards among the very large fallen blocks of conglomerate at the foot of the cliff will bring one to a fine exposure of the unconformity of the conglomerate on purple lava. The conglomerate includes many clasts of pink 'porphyry' up to 0.6 m in size, as well as of green and brown sandstone, and there are a few lenticular bands of cross-bedded sandstone up to 1.5 m thick. Slabby jointing is a notable feature in the underlying lavas. Both rocks are cut by calcite veins, and secondary tufa has been precipitated at several points from the conglomerate. In this area the base of the conglomerate drops gradually northwards.		To the east the cliffs below Eyemouth Fort are capped by a brighter red rock, a coarse conglomerate with bands of sandstone, of the Devono-Carboniferous Upper Old Red Sandstone. On a northward promontory near the western end of the outcrop 12 m of this rock is exposed, overlying slabby-jointed purple lava in the lower part of the cliff. The sediments consist largely of conglomerate, including angular fragments of purple lava and pale green sandstone, with a lenticular bed of cross-bedded sandstone between 2.5 and 5 m. from the top. The junction with the lavas is generally flat-lying, with local variations, as on the western side of the promontory, where it dips to south-east at 45°, and on the headland, where it rises abruptly to the north-East of the promontory the level of the base falls and conglomerate is extensively exposed on the rocky foreshore north of the cliffs. The process is interrupted by a 9-m NNE fault along the east side of the bay east of the promontory, which raises the lavas to the level of the base of the cliffs. Within a further 50 m to the east however the base of the conglomerate descends and swings across the foreshore to north, cutting off the outcrop of the lavas. For 75 m along the cliff, within 100 m west of the main headland, lava crops out in narrow inliers bounded to north and west by faults striking ENE and NNE, parallel to others seen farther to west. At most states of the tide it will be advisable, if not necessary, to retrace one's steps to the west, regain the cliff-top and descend on the south side of the Fort by a rough rocky path in the embayment 170 m south-west of the northwards headland. A scramble 80 m northwards among the very large fallen blocks of conglomerate at the foot of the cliff will bring one to a fine exposure of the unconformity of the conglomerate on purple lava. The conglomerate includes many clasts of pink 'porphyry' up to 0.6 m in size, as well as of green and brown sandstone, and there are a few lenticular bands of cross-bedded sandstone up to 1.5 m thick. Slabby jointing is a notable feature in the underlying lavas. Both rocks are cut by calcite veins, and secondary tufa has been precipitated at several points from the conglomerate. In this area the base of the conglomerate drops gradually northwards.[[File:P005900.jpg\|thumb\|200px\|right\|Eyemouth Fort. SW view. Glacial deposits. Boulder clay rests on bedded gravel with thick band of bedded sand. On left the lower beds abut against pale purple lavas of Lower Old Red Sandstone age, marking the south-east limit of a channel. The drift deposits are c. 13 m. thick.[http://194.66.252.158/asset-bank/action/viewAsset?id=5149 P005900]]]

	The lavas to the south are predominantly agglomeratic and include brecciated dacite, the most acid of all these St Abbs-Eyemouth rocks. It is well exposed on a minor promontory below the southern limit of the conglomerate, where it is developed as an accumulation of disoriented subangular blocks of rather soft greyish rock with prominent flow-oriented small feldspars. Small knots of malachite occur locally. This auto-brecciated lava is highly homogeneous, but the exposures scattered across the foreshore to south consist most commonly of blocks of lava embedded in an igneous matrix C At one point on the cliff the volcanic rocks are channelled by a sequence of gravel and sand 10 m thick, overlain by 3 m of boulder clay. The lower deposits, in part clearly stratified and showing some rounding of pebbles, are considered to mark the course of a stream prior to the last (Devensian) glaciation.		The lavas to the south are predominantly agglomeratic and include brecciated dacite, the most acid of all these St Abbs-Eyemouth rocks. It is well exposed on a minor promontory below the southern limit of the conglomerate, where it is developed as an accumulation of disoriented subangular blocks of rather soft greyish rock with prominent flow-oriented small feldspars. Small knots of malachite occur locally. This auto-brecciated lava is highly homogeneous, but the exposures scattered across the foreshore to south consist most commonly of blocks of lava embedded in an igneous matrix C At one point on the cliff the volcanic rocks are channelled by a sequence of gravel and sand 10 m thick, overlain by 3 m of boulder clay. The lower deposits, in part clearly stratified and showing some rounding of pebbles, are considered to mark the course of a stream prior to the last (Devensian) glaciation.

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	'''By D.C.Greig. From Scottish Borders geology: an excursion guide edited by A.D. McAdam, E.N.K. Clarkson, P. Stone. Edinburgh : Scottish Academic Press, 1972.'''		'''By D.C.Greig. From Scottish Borders geology: an excursion guide edited by A.D. McAdam, E.N.K. Clarkson, P. Stone. Edinburgh : Scottish Academic Press, 1972.'''



	O.S. 1:50 000 Sheet 67 Duns and Dunbar		O.S. 1:50 000 Sheet 67 Duns and Dunbar

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	* west of the town - 3 km, mainly on roads and cliff-top paths, 1 km of it on rough rocky shore		* west of the town - 3 km, mainly on roads and cliff-top paths, 1 km of it on rough rocky shore
	* east of the town - 6 km divided about equally between roads and cliff-top paths, with short rocky traverses at the numbered localities; the Redhall diversion adds 1.7 km on roads and across fields		* east of the town - 6 km divided about equally between roads and cliff-top paths, with short rocky traverses at the numbered localities; the Redhall diversion adds 1.7 km on roads and across fields
	[[File:EyemouthExcursionMap.jpg\|thumb\|350px\|~~center~~\|Eyemouth - an excursion map]]		[[File:EyemouthExcursionMap.jpg\|thumb\|350px\|right\|Eyemouth - an excursion map]]
	=== Excursion A. West of Eyemouth ===		=== Excursion A. West of Eyemouth ===
	==== 1. Killiedraught Bay: Volcanic Vent ====		==== 1. Killiedraught Bay: Volcanic Vent ====

Scotfot at 21:44, 7 March 2015

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← Older revision		Revision as of 22:44, 7 March 2015
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	* west of the town - 3 km, mainly on roads and cliff-top paths, 1 km of it on rough rocky shore		* west of the town - 3 km, mainly on roads and cliff-top paths, 1 km of it on rough rocky shore
	* east of the town - 6 km divided about equally between roads and cliff-top paths, with short rocky traverses at the numbered localities; the Redhall diversion adds 1.7 km on roads and across fields		* east of the town - 6 km divided about equally between roads and cliff-top paths, with short rocky traverses at the numbered localities; the Redhall diversion adds 1.7 km on roads and across fields
	[[File:EyemouthExcursionMap.jpg\|thumb\|~~600px~~\|center\|Eyemouth - an excursion map]]		[[File:EyemouthExcursionMap.jpg\|thumb\|350px\|center\|Eyemouth - an excursion map]]
	=== Excursion A. West of Eyemouth ===		=== Excursion A. West of Eyemouth ===
	==== 1. Killiedraught Bay: Volcanic Vent ====		==== 1. Killiedraught Bay: Volcanic Vent ====

Scotfot at 21:44, 7 March 2015

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← Older revision		Revision as of 22:44, 7 March 2015
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	* west of the town - 3 km, mainly on roads and cliff-top paths, 1 km of it on rough rocky shore		* west of the town - 3 km, mainly on roads and cliff-top paths, 1 km of it on rough rocky shore
	* east of the town - 6 km divided about equally between roads and cliff-top paths, with short rocky traverses at the numbered localities; the Redhall diversion adds 1.7 km on roads and across fields		* east of the town - 6 km divided about equally between roads and cliff-top paths, with short rocky traverses at the numbered localities; the Redhall diversion adds 1.7 km on roads and across fields
			[[File:EyemouthExcursionMap.jpg\|thumb\|600px\|center\|Eyemouth - an excursion map]]
	=== Excursion A. West of Eyemouth ===		=== Excursion A. West of Eyemouth ===
	==== 1. Killiedraught Bay: Volcanic Vent ====		==== 1. Killiedraught Bay: Volcanic Vent ====