Langholm and Canonbie - an excursion - Revision history

Scotfot at 19:43, 6 November 2015

2015-11-06T19:43:12Z

← Older revision		Revision as of 20:43, 6 November 2015
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	By S K Monro. Excursion 1. From: Stone, P (editor). 1996. [[Geology in south-west Scotland: an excursion guide.]] Keyworth, Nottingham: British Geological Survey.		By S K Monro. Excursion 1. From: Stone, P (editor). 1996. [[Geology in south-west Scotland: an excursion guide\|Geology in south-west Scotland: an excursion guide.]] Keyworth, Nottingham: British Geological Survey.

	== Langholm and Canonbie: the evolution of a sedimentary basin ==		== Langholm and Canonbie: the evolution of a sedimentary basin ==

Scotfot at 19:41, 6 November 2015

2015-11-06T19:41:46Z

← Older revision		Revision as of 20:41, 6 November 2015
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	By S K Monro. Excursion 1. From: Stone, P (editor). 1996. Geology in south-west Scotland: an excursion guide. Keyworth, Nottingham: British Geological Survey.		By S K Monro. Excursion 1. From: Stone, P (editor). 1996. [[Geology in south-west Scotland: an excursion guide.]] Keyworth, Nottingham: British Geological Survey.

	== Langholm and Canonbie: the evolution of a sedimentary basin ==		== Langholm and Canonbie: the evolution of a sedimentary basin ==

JenniferFindlay1 at 09:14, 6 October 2015

2015-10-06T09:14:11Z

← Older revision		Revision as of 10:14, 6 October 2015
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	From Langholm turn NW off the A7 and follow the B709 up the valley of the River Esk. Peden's View Quarry (NY 345 862) is 5 km from Langholm on the right.		From Langholm turn NW off the A7 and follow the B709 up the valley of the River Esk. Peden's View Quarry (NY 345 862) is 5 km from Langholm on the right.

	The rocks here belong to the Hawick Group (Carghidown Formation) of Wen-lock age and form part of the old basement of the Northumberland Trough. Beds of greywacke are dominant, a poorly sorted and immature sandstone, interbedded with shales. They were deposited by turbidity currents which flowed across the sea bed, mostly from the NE along the axis of the Silurian sedimentary basin. Each bed of greywacke represents an event when a turbidity current, charged with sediment, deposited its load. The base of the greywacke bed is generally coarse grained but as the current slackened progressively finer sediment was deposited (see Figure 6) to produce graded bedding. The effects of a turbidity current on the soft, fine-grained sediment deposited during a previous flow can be seen in the erosional sedimentary structures. In Peden's View Quarry large bedding planes are exposed along which groove casts are seen to have bifurcated, and grooves within grooves have developed. These features give a real impression of the direction of flow of the turbidity current and some idea of its erosive power. Prod marks can also be seen. These result when debris carried in the current scores the underlying unconsolidated mud before being plucked back into the current. Load casts can also be seen where the denser greywacke, once deposited, has sunk into the soft mud below. Ripple marks are less common but may also be seen here.		The rocks here belong to the Hawick Group (Carghidown Formation) of Wen-lock age and form part of the old basement of the Northumberland Trough. Beds of greywacke are dominant, a poorly sorted and immature sandstone, interbedded with shales. They were deposited by turbidity currents which flowed across the sea bed, mostly from the NE along the axis of the Silurian sedimentary basin. Each bed of greywacke represents an event when a turbidity current, charged with sediment, deposited its load. The base of the greywacke bed is generally coarse grained but as the current slackened progressively finer sediment was deposited (see Figure 6) to produce graded bedding. The effects of a turbidity current on the soft, fine-grained sediment deposited during a previous flow can be seen in the erosional sedimentary structures. In Peden's View Quarry large bedding planes are exposed along which groove casts are seen to have bifurcated, and grooves within grooves have developed. These features give a real impression of the direction of flow of the turbidity current and some idea of its erosive power.[[File:P218294.jpg\|300px\|thumbnail\|left\|Pedens View Quarry, 2.6 km. NW of Langholm. Groove casts, bifurcating and groove in groove structure. P218294]] Prod marks can also be seen. These result when debris carried in the current scores the underlying unconsolidated mud before being plucked back into the current. Load casts can also be seen where the denser greywacke, once deposited, has sunk into the soft mud below. Ripple marks are less common but may also be seen here.

	These sedimentary structures are useful in determining the environment of deposition but they can also tell which way up the strata are resting. From the steeply inclined orientation of the bedding planes it is clear that the strata have been compressed and folded, but to determine the nature of the folding in terms of anticlines or synclines it ''is ''necessary to know the way up of the strata. Groove casts, prod marks and load casts are features only found on the ''bottom ''of a greywacke bed. Using this knowledge it can be seen that the beds here are upside down, with the beds getting younger downwards. This conclusion may be tested by looking for other sedimentary structures: graded bedding and ripple marking should confirm it.		These sedimentary structures are useful in determining the environment of deposition but they can also tell which way up the strata are [[File:P218281.jpg\|300px\|thumbnail\|right\|Peden's View Quarry, 2.6 km. NW of Langholm. Tight fold in massive and flaggy greywackes. P218281]] resting. From the steeply inclined orientation of the bedding planes it is clear that the strata have been compressed and folded, but to determine the nature of the folding in terms of anticlines or synclines it ''is ''necessary to know the way up of the strata. Groove casts, prod marks and load casts are features only found on the ''bottom ''of a greywacke bed. Using this knowledge it can be seen that the beds here are upside down, with the beds getting younger downwards. This conclusion may be tested by looking for other sedimentary structures: graded bedding and ripple marking should confirm it.

	The rocks have been folded and the orientation of the bedding here can be determined by measuring the dip and strike of the bedding planes. However, other planar surfaces are also present in these rocks. The process of folding has produced new platy minerals which have grown with the plates perpendicular to the principal direction of stress. These planes are cleavage planes and they are often orientated approximately parallel to the axial plane of the folds. Measuring the orientation (dip and strike) of the cleavage plane thus allows you also to determine the orientation of the axial plane of the folds. The next locality will develop this concept further.		The rocks have been folded and the orientation of the bedding here can be determined by measuring the dip and strike of the bedding planes. However, other planar surfaces are also present in these rocks. The process of folding has produced new platy minerals which have grown with the plates perpendicular to the principal direction of stress. These planes are cleavage planes and they are often orientated approximately parallel to the axial plane of the folds. Measuring the orientation (dip and strike) of the cleavage plane thus allows you also to determine the orientation of the axial plane of the folds. The next locality will develop this concept further.
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	==== 3 Skipper's Bridge: Birrenswark lavas ====		==== 3 Skipper's Bridge: Birrenswark lavas ====
	Return to Langholm and head south on the A7 for 3 km. At Skipper's Bridge continue south on to the B6318 immediately before the A7 turns right on to the bridge. Park on the roadside (NY 371 833). Access to the rocks is by a gate on the west side of the bridge. The section can be examined for about 1.5 km downstream from the bridge. '''Extreme care should be taken if the river is in flood.'''		[[File:P220173.jpg\|300px\|thumbnail\|right\|River Esk, Skipper's Bridge, Langholm. Birrenswark Lavas, forming the foundations for Skipper's Bridge, Langholm. P220173]]Return to Langholm and head south on the A7 for 3 km. At Skipper's Bridge continue south on to the B6318 immediately before the A7 turns right on to the bridge. Park on the roadside (NY 371 833). Access to the rocks is by a gate on the west side of the bridge. The section can be examined for about 1.5 km downstream from the bridge. '''Extreme care should be taken if the river is in flood.'''

	The Birrenswark lavas can be seen on the riverside at Skipper's Bridge. The main lava lithology is olivine-rich microporphyritic basalt, with olivines or pyroxenes less than 2 mm in size. The lavas are rarely fresh and often the olivine or pyroxene is replaced by reddish brown iron oxides. The upper parts of individual lava flows are commonly amygdaloidal, with former gas bubbles in the lava now filled by secondary minerals, usually calcite. The thickness of lavas here is at least 50 m. At Skipper's Pool (NY 3703 8328), sedimentary rocks can be seen interbedded with the basaltic lavas. These are iron-rich, water-laid deposits formed by reworking the weathered rubbly tops of the lavas. Angular blocks of basalt, probably locally derived, can also be seen in these strata.		The Birrenswark lavas can be seen on the riverside at Skipper's Bridge. The main lava lithology is olivine-rich microporphyritic basalt, with olivines or pyroxenes less than 2 mm in size. The lavas are rarely fresh and often the olivine or pyroxene is replaced by reddish brown iron oxides. The upper parts of individual lava flows are commonly amygdaloidal, with former gas bubbles in the lava now filled by secondary minerals, usually calcite. The thickness of lavas here is at least 50 m. At Skipper's Pool (NY 3703 8328), sedimentary rocks can be seen interbedded with the basaltic lavas. These are iron-rich, water-laid deposits formed by reworking the weathered rubbly tops of the lavas. Angular blocks of basalt, probably locally derived, can also be seen in these strata.
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	[[File:LangholmCanonbieCarboniferousSectionLiddelWater.jpg\|thumbnail\|The Carboniferous section in the Liddel Water at Penton Linns (Locality 4).]]		[[File:LangholmCanonbieCarboniferousSectionLiddelWater.jpg\|thumbnail\|The Carboniferous section in the Liddel Water at Penton Linns (Locality 4).]]

	The limestones were deposited in a shallow- marine environment and are made up of organic fragments, some large and recognisable and others broken down to fine-grained carbonate sediment. Large productoid brachiopods, Gigantoproductus sp., and large solitary corals are common in the Penton Limestone. Near the top of this bed occur algal patches, ''Girvanella, ''and a trace fossil, ''Zoophycos caudagalli. ''The Bridge Limestone is only sparsely fossiliferous but near the top ''Zoophycos caudagalli ''occurs together with large crinoid stems and the colonial coral ''Siphonodendron pauciradiale. ''The Linns Limestone is sandy at its base and has the characteristic ochreous colour of a dolomitic limestone. The top of the Linns Limestone is red, iron-rich and knobbly. The Tombstone Limestone is poorly fossiliferous but the mudstone immediately above contains a diverse marine fauna including corals, brachiopods, gastropods, bivalves and goniatites. In the Gastropod Limestone at Loup Pool (NY 430 774) crinoid columnals, brachiopods, gastropods, bivalves and trilobite fragments can be found. The Harelawhill Limestone crops out on the prominent tree-covered island. This limestone is sparsely fossiliferous but crinoid columnals and corals including ''Siphonodendron junceum ''are present; near the top are several beds of nodular chert.		[[File:P220174.jpg\|300px\|thumbnail\|left\|Penton Linns, Liddell Water, 2.5 m. ENE of Canonbie. Steeply-dipping limestones (Upper Liddlesdale Group). P220174]]The limestones were deposited in a shallow- marine environment and are made up of organic fragments, some large and recognisable and others broken down to fine-grained carbonate sediment. Large productoid brachiopods, Gigantoproductus sp., and large solitary corals are common in the Penton Limestone. Near the top of this bed occur algal patches, ''Girvanella, ''and a trace fossil, ''Zoophycos caudagalli. ''The Bridge Limestone is only sparsely fossiliferous but near the top ''Zoophycos caudagalli ''occurs together with large crinoid stems and the colonial coral ''Siphonodendron pauciradiale. ''The Linns Limestone is sandy at its base and has the characteristic ochreous colour of a dolomitic limestone. The top of the Linns Limestone is red, iron-rich and knobbly. The Tombstone Limestone is poorly fossiliferous but the mudstone immediately above contains a diverse marine fauna including corals, brachiopods, gastropods, bivalves and goniatites. In the Gastropod Limestone at Loup Pool (NY 430 774) crinoid columnals, brachiopods, gastropods, bivalves and trilobite fragments can be found. The Harelawhill Limestone crops out on the prominent tree-covered island. This limestone is sparsely fossiliferous but crinoid columnals and corals including ''Siphonodendron junceum ''are present; near the top are several beds of nodular chert.

	The faunas in the limestones and overlying mudstones indicate that the depositional environment of these strata was a warm, shallow sea, probably close to a shoreline supplying fine-grained detritus. The presence of corals is a good indicator of shallow-water conditions, as these organisms require sunlight to survive.		The faunas in the limestones and overlying mudstones indicate that the depositional environment of these strata was a warm, shallow sea, probably close to a shoreline supplying fine-grained detritus. The presence of corals is a good indicator of shallow-water conditions, as these organisms require sunlight to survive.

Scotfot at 18:23, 29 March 2015

2015-03-29T18:23:11Z

← Older revision		Revision as of 19:23, 29 March 2015
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	[[File:Langholm and Canonbie excursion map.jpg\|300px\|thumbnail\|Locality map for the Langholm and canonbie excursion]]		[[File:Langholm and Canonbie excursion map.jpg\|300px\|thumbnail\|Locality map for the Langholm and canonbie excursion]]
	Langholm lies on the north margin of a Permo-Carboniferous sedimentary basin, the Northumberland Trough. The objective of this excursion is to look at the rocks filling the basin, to determine their characteristics and the environment in which they formed, and to piece these observations together into a model for the evolution of the northern margin of the Northumberland Trough through time. The Northumberland Trough contains rocks which range in age from early Carboniferous to Permian (Tables 1 and 2); they were deposited under changing environmental conditions which started as a shallow tropical sea and ended as a desert. The trough itself resulted from the stretching and down-faulting of sedimentary rocks of Silurian age, which had already been extensively folded and faulted during the Caledonian Orogeny. The range of rocks of differing lithology, and age makes Langholm an exciting area in which to investigate how a sedimentary basin starts, how it evolves and how sediments fill it through time. The area is described in detail by Lumsden et al. (1967).		Langholm lies on the north margin of a Permo-Carboniferous sedimentary basin, the Northumberland Trough. The objective of this excursion is to look at the rocks filling the basin, to determine their characteristics and the environment in which they formed, and to piece these observations together into a model for the evolution of the northern margin of the Northumberland Trough through time. The Northumberland Trough contains rocks which range in age from early Carboniferous to Permian (Tables 1 and 2); they were deposited under changing environmental conditions which started as a shallow tropical sea and ended as a desert. The trough itself resulted from the stretching and down-faulting of sedimentary rocks of Silurian age, which had already been extensively folded and faulted during the Caledonian Orogeny. The range of rocks of differing lithology, and age makes Langholm an exciting area in which to investigate how a sedimentary basin starts, how it evolves and how sediments fill it through time. The area is described in detail by Lumsden et al. (1967).

			=== Excursion ===

	==== 1 Peden's View Quarry: Hawick Group greywackes ====		==== 1 Peden's View Quarry: Hawick Group greywackes ====

Scotfot: /* 6 Canonbie: Permian to Triassic */

2015-03-29T16:14:25Z

6 Canonbie: Permian to Triassic

← Older revision		Revision as of 17:14, 29 March 2015
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	From Gilnockie Bridge, return to Canonbie via the new bypass and at its junction with the old A7, turn left, heading north. Continue through the village and, immediately after crossing the bridge over the River Esk, turn right and park at the churchyard (NY 395 763). Access to the riverbank is by a public footpath.		From Gilnockie Bridge, return to Canonbie via the new bypass and at its junction with the old A7, turn left, heading north. Continue through the village and, immediately after crossing the bridge over the River Esk, turn right and park at the churchyard (NY 395 763). Access to the riverbank is by a public footpath.

	Walking along the eastern bank of the River Esk affords views of the red sandstones, thought to be of Permian to Triassic age, on the opposite bank between Dead Neuk (NY 3923 7621) and Prior Linn (NY 3927 7615). Large-scale dune cross-bedding can be seen with individual foresets in the order of 3 m high. Note that the tops of the foresets are truncated by bounding surfaces and each group of foresets represents the migration of an individual sand dune. The nature and significance of these bounding surfaces and the detailed sedimentary structures and grain characteristics of wind-blown sedimentary rocks in general, are described in Excursion 9. For a closer examination of these rocks at Canonbie, the opposite river bank must be accessed at Prior Linn on the A7 at the south edge of the village (394 759). Like those at Locharbriggs (Excursion 9, locality 1), the sandstones at Canonbie are coarse grained and well sorted with well-rounded 'millet-seed' grains. These characteristics are typical of wind-transported sands.		Walking along the eastern bank of the River Esk affords views of the red sandstones, thought to be of Permian to Triassic age, on the opposite bank between Dead Neuk (NY 3923 7621) and Prior Linn (NY 3927 7615). Large-scale dune cross-bedding can be seen with individual foresets in the order of 3 m high. Note that the tops of the foresets are truncated by bounding surfaces and each group of foresets represents the migration of an individual sand dune. The nature and significance of these bounding surfaces and the detailed sedimentary structures and grain characteristics of wind-blown sedimentary rocks in general, are described in Excursion 9. For a closer examination of these rocks at Canonbie, the opposite river bank must be accessed at Prior Linn on the A7 at the south edge of the village (NY 394 759). Like those at Locharbriggs (Excursion 9, locality 1), the sandstones at Canonbie are coarse grained and well sorted with well-rounded 'millet-seed' grains. These characteristics are typical of wind-transported sands.

	The red sandstones are the last evidence for the filling of the Northumberland Trough which had become completely terrestrial, with desert conditions prevailing. However, these Permian strata were deposited in basins, like the Dumfries Basin and the Vale of Eden, which are elongated NNW-SSE and opened up in response to a new extensional regime. There is some evidence that this transition was preceded by a tectonic inversion, probably towards the end of the Carboniferous, when compression of the strata of the Northumberland Trough took place prior to the extension which established the new Permian basins.		The red sandstones are the last evidence for the filling of the Northumberland Trough which had become completely terrestrial, with desert conditions prevailing. However, these Permian strata were deposited in basins, like the Dumfries Basin and the Vale of Eden, which are elongated NNW-SSE and opened up in response to a new extensional regime. There is some evidence that this transition was preceded by a tectonic inversion, probably towards the end of the Carboniferous, when compression of the strata of the Northumberland Trough took place prior to the extension which established the new Permian basins.

Scotfot: /* 6 Canonbie: Permian to Triassic */

2015-03-29T16:14:08Z

6 Canonbie: Permian to Triassic

← Older revision		Revision as of 17:14, 29 March 2015
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	==== 6 Canonbie: Permian to Triassic ====		==== 6 Canonbie: Permian to Triassic ====
	From Gilnockie Bridge, return to Canonbie via the new bypass and at its junction with the old A7, turn left, heading north. Continue through the village and, immediately after crossing the bridge over the River Esk, turn right and park at the churchyard (395 763). Access to the riverbank is by a public footpath.		From Gilnockie Bridge, return to Canonbie via the new bypass and at its junction with the old A7, turn left, heading north. Continue through the village and, immediately after crossing the bridge over the River Esk, turn right and park at the churchyard (NY 395 763). Access to the riverbank is by a public footpath.

	Walking along the eastern bank of the River Esk affords views of the red sandstones, thought to be of Permian to Triassic age, on the opposite bank between Dead Neuk (NY 3923 7621) and Prior Linn (NY 3927 7615). Large-scale dune cross-bedding can be seen with individual foresets in the order of 3 m high. Note that the tops of the foresets are truncated by bounding surfaces and each group of foresets represents the migration of an individual sand dune. The nature and significance of these bounding surfaces and the detailed sedimentary structures and grain characteristics of wind-blown sedimentary rocks in general, are described in Excursion 9. For a closer examination of these rocks at Canonbie, the opposite river bank must be accessed at Prior Linn on the A7 at the south edge of the village (394 759). Like those at Locharbriggs (Excursion 9, locality 1), the sandstones at Canonbie are coarse grained and well sorted with well-rounded 'millet-seed' grains. These characteristics are typical of wind-transported sands.		Walking along the eastern bank of the River Esk affords views of the red sandstones, thought to be of Permian to Triassic age, on the opposite bank between Dead Neuk (NY 3923 7621) and Prior Linn (NY 3927 7615). Large-scale dune cross-bedding can be seen with individual foresets in the order of 3 m high. Note that the tops of the foresets are truncated by bounding surfaces and each group of foresets represents the migration of an individual sand dune. The nature and significance of these bounding surfaces and the detailed sedimentary structures and grain characteristics of wind-blown sedimentary rocks in general, are described in Excursion 9. For a closer examination of these rocks at Canonbie, the opposite river bank must be accessed at Prior Linn on the A7 at the south edge of the village (394 759). Like those at Locharbriggs (Excursion 9, locality 1), the sandstones at Canonbie are coarse grained and well sorted with well-rounded 'millet-seed' grains. These characteristics are typical of wind-transported sands.

	The red sandstones are the last evidence for the filling of the Northumberland Trough which had become completely terrestrial, with desert conditions prevailing. However, these Permian strata were deposited in basins, like the Dumfries Basin and the Vale of Eden, which are elongated ~~NNW—SSE~~ and opened up in response to a new extensional regime. There is some evidence that this transition was preceded by a tectonic inversion, probably towards the end of the Carboniferous, when compression of the strata of the Northumberland Trough took place prior to the extension which established the new Permian basins.		The red sandstones are the last evidence for the filling of the Northumberland Trough which had become completely terrestrial, with desert conditions prevailing. However, these Permian strata were deposited in basins, like the Dumfries Basin and the Vale of Eden, which are elongated NNW-SSE and opened up in response to a new extensional regime. There is some evidence that this transition was preceded by a tectonic inversion, probably towards the end of the Carboniferous, when compression of the strata of the Northumberland Trough took place prior to the extension which established the new Permian basins.

	===References===		===References===

Scotfot at 16:12, 29 March 2015

2015-03-29T16:12:56Z

← Older revision		Revision as of 17:12, 29 March 2015
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	[[File:LangholmCanonbieCarboniferousSectionLiddelWater.jpg\|thumbnail\|The Carboniferous section in the Liddel Water at Penton Linns (Locality 4).]]		[[File:LangholmCanonbieCarboniferousSectionLiddelWater.jpg\|thumbnail\|The Carboniferous section in the Liddel Water at Penton Linns (Locality 4).]]

	The limestones were deposited in a shallow- marine environment and are made up of organic fragments, some large and recognisable and others broken down to fine-grained carbonate sediment. Large productoid brachiopods, Gigantoproductus sp., and large solitary corals are common in the Penton Limestone. Near the top of this bed occur algal patches, ''Girvanella, ''and a trace fossil, ''Zoophycos caudagalli. ''The Bridge Limestone is only sparsely fossiliferous but near the top ''Zoophycos caudagalli ''occurs together with large crinoid stems and the colonial coral ''Siphonodendron pauciradiale. ''The Linns Limestone is sandy at its base and has the characteristic ochreous colour of a dolomitic limestone. The top of the Linns Limestone is red, iron-rich and knobbly. The Tombstone Limestone is poorly fossiliferous but the mudstone immediately above contains a diverse marine fauna including corals, brachiopods, gastropods, bivalves and goniatites. In the Gastropod Limestone at Loup Pool (430 774) crinoid columnals, brachiopods, gastropods, bivalves and trilobite fragments can be found. The Harelawhill Limestone crops out on the prominent tree-covered island. This limestone is sparsely fossiliferous but crinoid columnals and corals including ''Siphonodendron junceum ''are present; near the top are several beds of nodular chert.		The limestones were deposited in a shallow- marine environment and are made up of organic fragments, some large and recognisable and others broken down to fine-grained carbonate sediment. Large productoid brachiopods, Gigantoproductus sp., and large solitary corals are common in the Penton Limestone. Near the top of this bed occur algal patches, ''Girvanella, ''and a trace fossil, ''Zoophycos caudagalli. ''The Bridge Limestone is only sparsely fossiliferous but near the top ''Zoophycos caudagalli ''occurs together with large crinoid stems and the colonial coral ''Siphonodendron pauciradiale. ''The Linns Limestone is sandy at its base and has the characteristic ochreous colour of a dolomitic limestone. The top of the Linns Limestone is red, iron-rich and knobbly. The Tombstone Limestone is poorly fossiliferous but the mudstone immediately above contains a diverse marine fauna including corals, brachiopods, gastropods, bivalves and goniatites. In the Gastropod Limestone at Loup Pool (NY 430 774) crinoid columnals, brachiopods, gastropods, bivalves and trilobite fragments can be found. The Harelawhill Limestone crops out on the prominent tree-covered island. This limestone is sparsely fossiliferous but crinoid columnals and corals including ''Siphonodendron junceum ''are present; near the top are several beds of nodular chert.

	The faunas in the limestones and overlying mudstones indicate that the depositional environment of these strata was a warm, shallow sea, probably close to a shoreline supplying fine-grained detritus. The presence of corals is a good indicator of shallow-water conditions, as these organisms require sunlight to survive.		The faunas in the limestones and overlying mudstones indicate that the depositional environment of these strata was a warm, shallow sea, probably close to a shoreline supplying fine-grained detritus. The presence of corals is a good indicator of shallow-water conditions, as these organisms require sunlight to survive.

Scotfot at 16:11, 29 March 2015

2015-03-29T16:11:46Z

← Older revision		Revision as of 17:11, 29 March 2015
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	The red sandstones are the last evidence for the filling of the Northumberland Trough which had become completely terrestrial, with desert conditions prevailing. However, these Permian strata were deposited in basins, like the Dumfries Basin and the Vale of Eden, which are elongated NNW—SSE and opened up in response to a new extensional regime. There is some evidence that this transition was preceded by a tectonic inversion, probably towards the end of the Carboniferous, when compression of the strata of the Northumberland Trough took place prior to the extension which established the new Permian basins.		The red sandstones are the last evidence for the filling of the Northumberland Trough which had become completely terrestrial, with desert conditions prevailing. However, these Permian strata were deposited in basins, like the Dumfries Basin and the Vale of Eden, which are elongated NNW—SSE and opened up in response to a new extensional regime. There is some evidence that this transition was preceded by a tectonic inversion, probably towards the end of the Carboniferous, when compression of the strata of the Northumberland Trough took place prior to the extension which established the new Permian basins.

			===References===

			<References/>
	{{EGwalks}}		{{EGwalks}}
			[[Category:6. The South of Scotland]]

	[[~~category~~:6. The South of Scotland]]

Scotfot at 15:50, 29 March 2015

2015-03-29T15:50:03Z

← Older revision		Revision as of 16:50, 29 March 2015
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	By S K Monro. From: Stone, P (editor). 1996. Geology in south-west Scotland: an excursion guide. Keyworth, Nottingham: British Geological Survey.		By S K Monro. Excursion 1. From: Stone, P (editor). 1996. Geology in south-west Scotland: an excursion guide. Keyworth, Nottingham: British Geological Survey.

	== Langholm and Canonbie: the evolution of a sedimentary basin ==		== Langholm and Canonbie: the evolution of a sedimentary basin ==

Scotfot: /* 4 Liddel Water: Upper Liddesdale Group, Penton Anticline */

2015-03-29T14:48:12Z

4 Liddel Water: Upper Liddesdale Group, Penton Anticline

← Older revision		Revision as of 15:48, 29 March 2015
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	\| '''Rhynchonellid Sandstone'''\|\|		\| '''Rhynchonellid Sandstone'''\|\|
	\|-		\|-
	\| sandstone, rooty \|\|0.81\|\|		\| sandstone, rooty \|\|0.81
	\|-		\|-
	\| sandstone and siltstone, thinly bedded\|\|2.98		\| sandstone and siltstone, thinly bedded\|\|2.98