Bedrock Geology UK North: Cenozoic - Revision history

Dbk at 12:33, 30 January 2015

2015-01-30T12:33:08Z

← Older revision		Revision as of 13:33, 30 January 2015
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	'''The initial, fissure eruptions''' produced mostly mafic lava but the later lava eruption from central volcanoes was accompanied by pyroclastic activity, which contributed to the sedimentary sequences accumulating in offshore basins. There, in the North Sea and Faroes–Shetland basins, more-or-less continuous Palaeogene and Neogene sequences of sandstone and mudstone reach thicknesses of 3000 and 4000 m, respectively. Post-volcanic Palaeogene sequences are preserved onshore only in Northern Ireland and may never have been extensive.		'''The initial, fissure eruptions''' produced mostly mafic lava but the later lava eruption from central volcanoes was accompanied by pyroclastic activity, which contributed to the sedimentary sequences accumulating in offshore basins. There, in the North Sea and Faroes–Shetland basins, more-or-less continuous Palaeogene and Neogene sequences of sandstone and mudstone reach thicknesses of 3000 and 4000 m, respectively. Post-volcanic Palaeogene sequences are preserved onshore only in Northern Ireland and may never have been extensive.

	<gallery widths=~~250px~~ heights=~~200px~~>		<gallery widths=200px heights=180px>
	Image:P000770.jpg\|Jointing in the upper part of the lava flow is chaotic but is spectacularly regular in the lower part, which rests on a bed of volcaniclastic rock. [http://geoscenic.bgs.ac.uk/asset-bank/action/viewAsset?id=2068&index=0&total=1&view=viewSearchItem P000770.]		Image:P000770.jpg\|Jointing in the upper part of the lava flow is chaotic but is spectacularly regular in the lower part, which rests on a bed of volcaniclastic rock. [http://geoscenic.bgs.ac.uk/asset-bank/action/viewAsset?id=2068&index=0&total=1&view=viewSearchItem P000770.]
	Image:P580487.jpg\|The hills of northern Arran, composed of Palaeogene granite from the Arran Central Complex. P580487.		Image:P580487.jpg\|The hills of northern Arran, composed of Palaeogene granite from the Arran Central Complex. P580487.

Dbk at 12:32, 30 January 2015

2015-01-30T12:32:40Z

← Older revision		Revision as of 13:32, 30 January 2015
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	'''The initial, fissure eruptions''' produced mostly mafic lava but the later lava eruption from central volcanoes was accompanied by pyroclastic activity, which contributed to the sedimentary sequences accumulating in offshore basins. There, in the North Sea and Faroes–Shetland basins, more-or-less continuous Palaeogene and Neogene sequences of sandstone and mudstone reach thicknesses of 3000 and 4000 m, respectively. Post-volcanic Palaeogene sequences are preserved onshore only in Northern Ireland and may never have been extensive.		'''The initial, fissure eruptions''' produced mostly mafic lava but the later lava eruption from central volcanoes was accompanied by pyroclastic activity, which contributed to the sedimentary sequences accumulating in offshore basins. There, in the North Sea and Faroes–Shetland basins, more-or-less continuous Palaeogene and Neogene sequences of sandstone and mudstone reach thicknesses of 3000 and 4000 m, respectively. Post-volcanic Palaeogene sequences are preserved onshore only in Northern Ireland and may never have been extensive.

	<gallery widths=250px>		<gallery widths=250px heights=200px>
	Image:P000770.jpg\|Jointing in the upper part of the lava flow is chaotic but is spectacularly regular in the lower part, which rests on a bed of volcaniclastic rock. [http://geoscenic.bgs.ac.uk/asset-bank/action/viewAsset?id=2068&index=0&total=1&view=viewSearchItem P000770.]		Image:P000770.jpg\|Jointing in the upper part of the lava flow is chaotic but is spectacularly regular in the lower part, which rests on a bed of volcaniclastic rock. [http://geoscenic.bgs.ac.uk/asset-bank/action/viewAsset?id=2068&index=0&total=1&view=viewSearchItem P000770.]
	Image:P580487.jpg\|The hills of northern Arran, composed of Palaeogene granite from the Arran Central Complex. P580487.		Image:P580487.jpg\|The hills of northern Arran, composed of Palaeogene granite from the Arran Central Complex. P580487.

Dbk at 12:32, 30 January 2015

2015-01-30T12:32:22Z

← Older revision		Revision as of 13:32, 30 January 2015
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	'''The initial, fissure eruptions''' produced mostly mafic lava but the later lava eruption from central volcanoes was accompanied by pyroclastic activity, which contributed to the sedimentary sequences accumulating in offshore basins. There, in the North Sea and Faroes–Shetland basins, more-or-less continuous Palaeogene and Neogene sequences of sandstone and mudstone reach thicknesses of 3000 and 4000 m, respectively. Post-volcanic Palaeogene sequences are preserved onshore only in Northern Ireland and may never have been extensive.		'''The initial, fissure eruptions''' produced mostly mafic lava but the later lava eruption from central volcanoes was accompanied by pyroclastic activity, which contributed to the sedimentary sequences accumulating in offshore basins. There, in the North Sea and Faroes–Shetland basins, more-or-less continuous Palaeogene and Neogene sequences of sandstone and mudstone reach thicknesses of 3000 and 4000 m, respectively. Post-volcanic Palaeogene sequences are preserved onshore only in Northern Ireland and may never have been extensive.

	<gallery ~~mode~~=~~"packed"~~>		<gallery widths=250px>
	Image:P000770.jpg\|Jointing in the upper part of the lava flow is chaotic but is spectacularly regular in the lower part, which rests on a bed of volcaniclastic rock. [http://geoscenic.bgs.ac.uk/asset-bank/action/viewAsset?id=2068&index=0&total=1&view=viewSearchItem P000770.]		Image:P000770.jpg\|Jointing in the upper part of the lava flow is chaotic but is spectacularly regular in the lower part, which rests on a bed of volcaniclastic rock. [http://geoscenic.bgs.ac.uk/asset-bank/action/viewAsset?id=2068&index=0&total=1&view=viewSearchItem P000770.]
	Image:P580487.jpg\|The hills of northern Arran, composed of Palaeogene granite from the Arran Central Complex. P580487.		Image:P580487.jpg\|The hills of northern Arran, composed of Palaeogene granite from the Arran Central Complex. P580487.

Dbk at 14:21, 29 January 2015

2015-01-29T14:21:24Z

← Older revision		Revision as of 15:21, 29 January 2015
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	'''Across much of Scotland''', the Palaeogene and Neogene periods were a time of erosion and deep weathering but, in north-east Scotland, sedimentary accumulations from that interval make up the Buchan Gravels Formation (N). The deposits are up to about 25 m thick with clasts, commonly of flint, quartzite and weathered granite, contained in a kaolinitic, silty-clay matrix; they have suffered pervasive, subaerial weathering under warm, humid conditions. A fluvial origin is possible for the younger quartzite-rich gravels. The older gravels contain mostly flint and granite clasts and, though now about 120 m above sea level, probably originated as a beach accumulation when sea level was much higher.		'''Across much of Scotland''', the Palaeogene and Neogene periods were a time of erosion and deep weathering but, in north-east Scotland, sedimentary accumulations from that interval make up the Buchan Gravels Formation (N). The deposits are up to about 25 m thick with clasts, commonly of flint, quartzite and weathered granite, contained in a kaolinitic, silty-clay matrix; they have suffered pervasive, subaerial weathering under warm, humid conditions. A fluvial origin is possible for the younger quartzite-rich gravels. The older gravels contain mostly flint and granite clasts and, though now about 120 m above sea level, probably originated as a beach accumulation when sea level was much higher.

			==Bedrock Geology UK North - contents==
			{{bedrockNorth}}


	[[Category:Bedrock Geology UK North\| 09]]		[[Category:Bedrock Geology UK North\| 09]]

Dbk at 09:02, 19 June 2014

2014-06-19T09:02:54Z

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			__NOTOC__
	{{BedN}}		{{BedN}}
	==65 million years ago to the present day==		==65 million years ago to the present day==

Dbk: Protected "Bedrock Geology UK North: Cenozoic" ([Edit=Allow only administrators] (indefinite) [Move=Allow only administrators] (indefinite)) [cascading]

2014-06-11T12:22:11Z

Protected "Bedrock Geology UK North: Cenozoic" ([Edit=Allow only administrators] (indefinite) [Move=Allow only administrators] (indefinite)) [cascading]

← Older revision	Revision as of 13:22, 11 June 2014
(No difference)

Dbk: /* Central, subvolcanic complexes and dyke swarms */

2014-05-21T12:57:54Z

Central, subvolcanic complexes and dyke swarms

← Older revision		Revision as of 13:57, 21 May 2014
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	[[Image:P001078.jpg\|thumb~~\|left~~\|200px\|A Palaeogene dolerite dyke left standing by the erosion of the Devonian sandstone into which it was intruded, Great Cumbrae, Firth of Clyde. [http://geoscenic.bgs.ac.uk/asset-bank/action/viewAsset?id=2376&index=0&total=1&view=viewSearchItem P001078.]]]		[[Image:P001078.jpg\|thumb\|200px\|A Palaeogene dolerite dyke left standing by the erosion of the Devonian sandstone into which it was intruded, Great Cumbrae, Firth of Clyde. [http://geoscenic.bgs.ac.uk/asset-bank/action/viewAsset?id=2376&index=0&total=1&view=viewSearchItem P001078.]]]

	'''Many of the mafic dykes''' that make up the regional swarms are less than a metre across, although dykes up to 10 m across are fairly common ('''Plate P001078'''). A few even broader ones have been recorded but these may be composite intrusions. Nearly all of the dykes consist of basalt and/or dolerite. The Skye and Mull central complexes were the major sources of dyke swarms that extend from the Outer Hebrides and St Kilda (itself formed by a Palaeogene central complex) south-east across southern Scotland and into northern England. Dykes in Northern Ireland focus on the Slieve Gullion Ring-complex and the Mourne Mountains plutonic centres, but the regional swarms extend from Rockall (another Palaeogene granite) in the north west, to Wales and the English Midlands in the south-east.		'''Many of the mafic dykes''' that make up the regional swarms are less than a metre across, although dykes up to 10 m across are fairly common ('''Plate P001078'''). A few even broader ones have been recorded but these may be composite intrusions. Nearly all of the dykes consist of basalt and/or dolerite. The Skye and Mull central complexes were the major sources of dyke swarms that extend from the Outer Hebrides and St Kilda (itself formed by a Palaeogene central complex) south-east across southern Scotland and into northern England. Dykes in Northern Ireland focus on the Slieve Gullion Ring-complex and the Mourne Mountains plutonic centres, but the regional swarms extend from Rockall (another Palaeogene granite) in the north west, to Wales and the English Midlands in the south-east.

Dbk: /* 65 million years ago to the present day */

2014-05-21T12:56:39Z

65 million years ago to the present day

← Older revision		Revision as of 13:56, 21 May 2014
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	[[Image:P006482.jpg\|thumb\|200px\|Columnar jointing in Palaeogene mafic lava forms the Giant's Causeway. The top of the Grand Causeway in the foreground, with the cliffs of Roveran Valley Head and Spaniard Rock in the background. [http://geoscenic.bgs.ac.uk/asset-bank/action/viewAsset?id=5542&index=0&total=1&view=viewSearchItem P006482.]]]		[[Image:P006482.jpg\|thumb\|200px\|Columnar jointing in Palaeogene mafic lava forms the Giant's Causeway. The top of the Grand Causeway in the foreground, with the cliffs of Roveran Valley Head and Spaniard Rock in the background. [http://geoscenic.bgs.ac.uk/asset-bank/action/viewAsset?id=5542&index=0&total=1&view=viewSearchItem P006482.]]]

			[[Image:P580464.jpg\|thumb\|left\|200px\|Columnar jointing in a thick Palaeogene basalt lava flow, Staffa (and Fingal's Cave). P580464.]]
	'''At the end of the Cretaceous Period uplift''' in southern Britain was associated with the first stirrings of the Alpine Orogeny—the deformation episode driven by collision between the European and African plates, which had separated with the break-up of Pangaea. The main Alpine structural effects were imposed during the Palaeogene Period, but had little impact beyond southern England and Wales. Farther north, a very different Palaeogene history unfolded. Here, regional uplift and erosion late in the Cretaceous preceded the major episode of magmatism that produced intrusive subvolcanic complexes and the extensive and largely subaerial Palaeogene lava fields (G ) that are seen across the Hebridean region of western Scotland and Northern Ireland ('''Figure P785804'''). Magmatism spanned an interval from about 62 Ma to about 55 Ma, and marked the first, failed attempts at continental break-up in an extensional episode of crustal thinning that culminated in the successful opening and spreading, farther west, of the Atlantic Ocean. Coarse, clastic sedimentary rocks are intercalated with the earliest of the lavas and suggest that the latter were erupted onto a land surface with considerable local relief. The climate was warm temperate to subtropical and plant remains from the sedimentary beds associated with the lavas confirm that they were erupted across surface environments that ranged from upland forests down to low-lying swamps and lakes. In one spectacular example from Mull, the cast of a large conifer—known as MacCulloch’s Tree—is encased in columnar basalt lava ('''Plate P580468''').		'''At the end of the Cretaceous Period uplift''' in southern Britain was associated with the first stirrings of the Alpine Orogeny—the deformation episode driven by collision between the European and African plates, which had separated with the break-up of Pangaea. The main Alpine structural effects were imposed during the Palaeogene Period, but had little impact beyond southern England and Wales. Farther north, a very different Palaeogene history unfolded. Here, regional uplift and erosion late in the Cretaceous preceded the major episode of magmatism that produced intrusive subvolcanic complexes and the extensive and largely subaerial Palaeogene lava fields (G ) that are seen across the Hebridean region of western Scotland and Northern Ireland ('''Figure P785804'''). Magmatism spanned an interval from about 62 Ma to about 55 Ma, and marked the first, failed attempts at continental break-up in an extensional episode of crustal thinning that culminated in the successful opening and spreading, farther west, of the Atlantic Ocean. Coarse, clastic sedimentary rocks are intercalated with the earliest of the lavas and suggest that the latter were erupted onto a land surface with considerable local relief. The climate was warm temperate to subtropical and plant remains from the sedimentary beds associated with the lavas confirm that they were erupted across surface environments that ranged from upland forests down to low-lying swamps and lakes. In one spectacular example from Mull, the cast of a large conifer—known as MacCulloch’s Tree—is encased in columnar basalt lava ('''Plate P580468''').

	[[Image:P785804.jpg\|thumb\|left\|200px\|Present-day distribution of lava fields and subvolcanic complexes of the Hebridean Province. P785804.]]		[[Image:P785804.jpg\|thumb\|left\|200px\|Present-day distribution of lava fields and subvolcanic complexes of the Hebridean Province. P785804.]]
	~~[[Image:P580464.jpg\|thumb\|left\|200px\|Columnar jointing in a thick Palaeogene basalt lava flow, Staffa (and Fingal's Cave). P580464.]]~~

	'''The initial, fissure eruptions''' produced mostly mafic lava but the later lava eruption from central volcanoes was accompanied by pyroclastic activity, which contributed to the sedimentary sequences accumulating in offshore basins. There, in the North Sea and Faroes–Shetland basins, more-or-less continuous Palaeogene and Neogene sequences of sandstone and mudstone reach thicknesses of 3000 and 4000 m, respectively. Post-volcanic Palaeogene sequences are preserved onshore only in Northern Ireland and may never have been extensive.		'''The initial, fissure eruptions''' produced mostly mafic lava but the later lava eruption from central volcanoes was accompanied by pyroclastic activity, which contributed to the sedimentary sequences accumulating in offshore basins. There, in the North Sea and Faroes–Shetland basins, more-or-less continuous Palaeogene and Neogene sequences of sandstone and mudstone reach thicknesses of 3000 and 4000 m, respectively. Post-volcanic Palaeogene sequences are preserved onshore only in Northern Ireland and may never have been extensive.

	<gallery mode="packed">		<gallery mode="packed">
	~~Image:P580464.jpg\|Columnar jointing in a thick Palaeogene basalt lava flow, Staffa (and Fingal's Cave). P580464.~~
	Image:P000770.jpg\|Jointing in the upper part of the lava flow is chaotic but is spectacularly regular in the lower part, which rests on a bed of volcaniclastic rock. [http://geoscenic.bgs.ac.uk/asset-bank/action/viewAsset?id=2068&index=0&total=1&view=viewSearchItem P000770.]		Image:P000770.jpg\|Jointing in the upper part of the lava flow is chaotic but is spectacularly regular in the lower part, which rests on a bed of volcaniclastic rock. [http://geoscenic.bgs.ac.uk/asset-bank/action/viewAsset?id=2068&index=0&total=1&view=viewSearchItem P000770.]
	Image:P580487.jpg\|The hills of northern Arran, composed of Palaeogene granite from the Arran Central Complex. P580487.		Image:P580487.jpg\|The hills of northern Arran, composed of Palaeogene granite from the Arran Central Complex. P580487.

Dbk: /* 65 million years ago to the present day */

2014-05-21T12:55:51Z

65 million years ago to the present day

← Older revision		Revision as of 13:55, 21 May 2014
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	[[Image:P785804.jpg\|thumb\|left\|200px\|Present-day distribution of lava fields and subvolcanic complexes of the Hebridean Province. P785804.]]		[[Image:P785804.jpg\|thumb\|left\|200px\|Present-day distribution of lava fields and subvolcanic complexes of the Hebridean Province. P785804.]]
			[[Image:P580464.jpg\|thumb\|left\|200px\|Columnar jointing in a thick Palaeogene basalt lava flow, Staffa (and Fingal's Cave). P580464.]]

	'''The initial, fissure eruptions''' produced mostly mafic lava but the later lava eruption from central volcanoes was accompanied by pyroclastic activity, which contributed to the sedimentary sequences accumulating in offshore basins. There, in the North Sea and Faroes–Shetland basins, more-or-less continuous Palaeogene and Neogene sequences of sandstone and mudstone reach thicknesses of 3000 and 4000 m, respectively. Post-volcanic Palaeogene sequences are preserved onshore only in Northern Ireland and may never have been extensive.		'''The initial, fissure eruptions''' produced mostly mafic lava but the later lava eruption from central volcanoes was accompanied by pyroclastic activity, which contributed to the sedimentary sequences accumulating in offshore basins. There, in the North Sea and Faroes–Shetland basins, more-or-less continuous Palaeogene and Neogene sequences of sandstone and mudstone reach thicknesses of 3000 and 4000 m, respectively. Post-volcanic Palaeogene sequences are preserved onshore only in Northern Ireland and may never have been extensive.

Dbk at 09:14, 20 May 2014

2014-05-20T09:14:34Z

← Older revision		Revision as of 13:56, 21 May 2014
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	[[Image:P006482.jpg\|thumb\|200px\|Columnar jointing in Palaeogene mafic lava forms the Giant's Causeway. The top of the Grand Causeway in the foreground, with the cliffs of Roveran Valley Head and Spaniard Rock in the background. [http://geoscenic.bgs.ac.uk/asset-bank/action/viewAsset?id=5542&index=0&total=1&view=viewSearchItem P006482.]]]		[[Image:P006482.jpg\|thumb\|200px\|Columnar jointing in Palaeogene mafic lava forms the Giant's Causeway. The top of the Grand Causeway in the foreground, with the cliffs of Roveran Valley Head and Spaniard Rock in the background. [http://geoscenic.bgs.ac.uk/asset-bank/action/viewAsset?id=5542&index=0&total=1&view=viewSearchItem P006482.]]]

			[[Image:P580464.jpg\|thumb\|left\|200px\|Columnar jointing in a thick Palaeogene basalt lava flow, Staffa (and Fingal's Cave). P580464.]]
	'''At the end of the Cretaceous Period uplift''' in southern Britain was associated with the first stirrings of the Alpine Orogeny—the deformation episode driven by collision between the European and African plates, which had separated with the break-up of Pangaea. The main Alpine structural effects were imposed during the Palaeogene Period, but had little impact beyond southern England and Wales. Farther north, a very different Palaeogene history unfolded. Here, regional uplift and erosion late in the Cretaceous preceded the major episode of magmatism that produced intrusive subvolcanic complexes and the extensive and largely subaerial Palaeogene lava fields (G ) that are seen across the Hebridean region of western Scotland and Northern Ireland ('''Figure P785804'''). Magmatism spanned an interval from about 62 Ma to about 55 Ma, and marked the first, failed attempts at continental break-up in an extensional episode of crustal thinning that culminated in the successful opening and spreading, farther west, of the Atlantic Ocean. Coarse, clastic sedimentary rocks are intercalated with the earliest of the lavas and suggest that the latter were erupted onto a land surface with considerable local relief. The climate was warm temperate to subtropical and plant remains from the sedimentary beds associated with the lavas confirm that they were erupted across surface environments that ranged from upland forests down to low-lying swamps and lakes. In one spectacular example from Mull, the cast of a large conifer—known as MacCulloch’s Tree—is encased in columnar basalt lava ('''Plate P580468''').		'''At the end of the Cretaceous Period uplift''' in southern Britain was associated with the first stirrings of the Alpine Orogeny—the deformation episode driven by collision between the European and African plates, which had separated with the break-up of Pangaea. The main Alpine structural effects were imposed during the Palaeogene Period, but had little impact beyond southern England and Wales. Farther north, a very different Palaeogene history unfolded. Here, regional uplift and erosion late in the Cretaceous preceded the major episode of magmatism that produced intrusive subvolcanic complexes and the extensive and largely subaerial Palaeogene lava fields (G ) that are seen across the Hebridean region of western Scotland and Northern Ireland ('''Figure P785804'''). Magmatism spanned an interval from about 62 Ma to about 55 Ma, and marked the first, failed attempts at continental break-up in an extensional episode of crustal thinning that culminated in the successful opening and spreading, farther west, of the Atlantic Ocean. Coarse, clastic sedimentary rocks are intercalated with the earliest of the lavas and suggest that the latter were erupted onto a land surface with considerable local relief. The climate was warm temperate to subtropical and plant remains from the sedimentary beds associated with the lavas confirm that they were erupted across surface environments that ranged from upland forests down to low-lying swamps and lakes. In one spectacular example from Mull, the cast of a large conifer—known as MacCulloch’s Tree—is encased in columnar basalt lava ('''Plate P580468''').

	[[Image:P785804.jpg\|thumb\|left\|200px\|Present-day distribution of lava fields and subvolcanic complexes of the Hebridean Province. P785804.]]		[[Image:P785804.jpg\|thumb\|left\|200px\|Present-day distribution of lava fields and subvolcanic complexes of the Hebridean Province. P785804.]]
	~~[[Image:P580464.jpg\|thumb\|left\|200px\|Columnar jointing in a thick Palaeogene basalt lava flow, Staffa (and Fingal's Cave). P580464.]]~~

	'''The initial, fissure eruptions''' produced mostly mafic lava but the later lava eruption from central volcanoes was accompanied by pyroclastic activity, which contributed to the sedimentary sequences accumulating in offshore basins. There, in the North Sea and Faroes–Shetland basins, more-or-less continuous Palaeogene and Neogene sequences of sandstone and mudstone reach thicknesses of 3000 and 4000 m, respectively. Post-volcanic Palaeogene sequences are preserved onshore only in Northern Ireland and may never have been extensive.		'''The initial, fissure eruptions''' produced mostly mafic lava but the later lava eruption from central volcanoes was accompanied by pyroclastic activity, which contributed to the sedimentary sequences accumulating in offshore basins. There, in the North Sea and Faroes–Shetland basins, more-or-less continuous Palaeogene and Neogene sequences of sandstone and mudstone reach thicknesses of 3000 and 4000 m, respectively. Post-volcanic Palaeogene sequences are preserved onshore only in Northern Ireland and may never have been extensive.

	<gallery mode="packed">		<gallery mode="packed">
	~~Image:P580464.jpg\|Columnar jointing in a thick Palaeogene basalt lava flow, Staffa (and Fingal's Cave). P580464.~~
	Image:P000770.jpg\|Jointing in the upper part of the lava flow is chaotic but is spectacularly regular in the lower part, which rests on a bed of volcaniclastic rock. [http://geoscenic.bgs.ac.uk/asset-bank/action/viewAsset?id=2068&index=0&total=1&view=viewSearchItem P000770.]		Image:P000770.jpg\|Jointing in the upper part of the lava flow is chaotic but is spectacularly regular in the lower part, which rests on a bed of volcaniclastic rock. [http://geoscenic.bgs.ac.uk/asset-bank/action/viewAsset?id=2068&index=0&total=1&view=viewSearchItem P000770.]
	Image:P580487.jpg\|The hills of northern Arran, composed of Palaeogene granite from the Arran Central Complex. P580487.		Image:P580487.jpg\|The hills of northern Arran, composed of Palaeogene granite from the Arran Central Complex. P580487.

← Older revision		Revision as of 10:14, 20 May 2014
Line 1:		Line 1:
	{{BedN}}		{{BedN}}
	==65 million years ago to the present day==		==65 million years ago to the present day==
	[[Image:P785813.jpg\|thumb\|200px\|~~[http://bgsintranet/asset-bank/action/viewFullSizedImage?id=379957&size=1000~~ P785813.]]]		[[Image:P785813.jpg\|thumb\|200px\|P785813.]]
	[[Image:P580468.jpg\|thumb\|200px\|MacCulloch's Tree: the cast of a large coniferous tree-trunk caught up in Palaeogene lava at Ardmeanach, Mull. ~~[http://bgsintranet/asset-bank/action/viewFullSizedImage?id=126003&size=1000~~ P580468.]]]		[[Image:P580468.jpg\|thumb\|200px\|MacCulloch's Tree: the cast of a large coniferous tree-trunk caught up in Palaeogene lava at Ardmeanach, Mull. P580468.]]
	[[Image:P006482.jpg\|thumb\|200px\|Columnar jointing in Palaeogene mafic lava forms the Giant's Causeway. The top of the Grand Causeway in the foreground, with the cliffs of Roveran Valley Head and Spaniard Rock in the background. [http://~~bgsintranet~~/asset-bank/action/~~viewFullSizedImage~~?id=5542&~~size~~=~~1000~~ P006482.]]]		[[Image:P006482.jpg\|thumb\|200px\|Columnar jointing in Palaeogene mafic lava forms the Giant's Causeway. The top of the Grand Causeway in the foreground, with the cliffs of Roveran Valley Head and Spaniard Rock in the background. [http://geoscenic.bgs.ac.uk/asset-bank/action/viewAsset?id=5542&index=0&total=1&view=viewSearchItem P006482.]]]

	'''At the end of the Cretaceous Period uplift''' in southern Britain was associated with the first stirrings of the Alpine Orogeny—the deformation episode driven by collision between the European and African plates, which had separated with the break-up of Pangaea. The main Alpine structural effects were imposed during the Palaeogene Period, but had little impact beyond southern England and Wales. Farther north, a very different Palaeogene history unfolded. Here, regional uplift and erosion late in the Cretaceous preceded the major episode of magmatism that produced intrusive subvolcanic complexes and the extensive and largely subaerial Palaeogene lava fields (G ) that are seen across the Hebridean region of western Scotland and Northern Ireland ('''Figure P785804'''). Magmatism spanned an interval from about 62 Ma to about 55 Ma, and marked the first, failed attempts at continental break-up in an extensional episode of crustal thinning that culminated in the successful opening and spreading, farther west, of the Atlantic Ocean. Coarse, clastic sedimentary rocks are intercalated with the earliest of the lavas and suggest that the latter were erupted onto a land surface with considerable local relief. The climate was warm temperate to subtropical and plant remains from the sedimentary beds associated with the lavas confirm that they were erupted across surface environments that ranged from upland forests down to low-lying swamps and lakes. In one spectacular example from Mull, the cast of a large conifer—known as MacCulloch’s Tree—is encased in columnar basalt lava ('''Plate P580468''').		'''At the end of the Cretaceous Period uplift''' in southern Britain was associated with the first stirrings of the Alpine Orogeny—the deformation episode driven by collision between the European and African plates, which had separated with the break-up of Pangaea. The main Alpine structural effects were imposed during the Palaeogene Period, but had little impact beyond southern England and Wales. Farther north, a very different Palaeogene history unfolded. Here, regional uplift and erosion late in the Cretaceous preceded the major episode of magmatism that produced intrusive subvolcanic complexes and the extensive and largely subaerial Palaeogene lava fields (G ) that are seen across the Hebridean region of western Scotland and Northern Ireland ('''Figure P785804'''). Magmatism spanned an interval from about 62 Ma to about 55 Ma, and marked the first, failed attempts at continental break-up in an extensional episode of crustal thinning that culminated in the successful opening and spreading, farther west, of the Atlantic Ocean. Coarse, clastic sedimentary rocks are intercalated with the earliest of the lavas and suggest that the latter were erupted onto a land surface with considerable local relief. The climate was warm temperate to subtropical and plant remains from the sedimentary beds associated with the lavas confirm that they were erupted across surface environments that ranged from upland forests down to low-lying swamps and lakes. In one spectacular example from Mull, the cast of a large conifer—known as MacCulloch’s Tree—is encased in columnar basalt lava ('''Plate P580468''').

	[[Image:P785804.jpg\|thumb\|left\|200px\|Present-day distribution of lava fields and subvolcanic complexes of the Hebridean Province. ~~[http://bgsintranet/asset-bank/action/viewFullSizedImage?id=379948&size=1000~~ P785804.]]]		[[Image:P785804.jpg\|thumb\|left\|200px\|Present-day distribution of lava fields and subvolcanic complexes of the Hebridean Province. P785804.]]

	'''The initial, fissure eruptions''' produced mostly mafic lava but the later lava eruption from central volcanoes was accompanied by pyroclastic activity, which contributed to the sedimentary sequences accumulating in offshore basins. There, in the North Sea and Faroes–Shetland basins, more-or-less continuous Palaeogene and Neogene sequences of sandstone and mudstone reach thicknesses of 3000 and 4000 m, respectively. Post-volcanic Palaeogene sequences are preserved onshore only in Northern Ireland and may never have been extensive.		'''The initial, fissure eruptions''' produced mostly mafic lava but the later lava eruption from central volcanoes was accompanied by pyroclastic activity, which contributed to the sedimentary sequences accumulating in offshore basins. There, in the North Sea and Faroes–Shetland basins, more-or-less continuous Palaeogene and Neogene sequences of sandstone and mudstone reach thicknesses of 3000 and 4000 m, respectively. Post-volcanic Palaeogene sequences are preserved onshore only in Northern Ireland and may never have been extensive.

	<gallery mode="packed">		<gallery mode="packed">
	Image:P580464.jpg\|Columnar jointing in a thick Palaeogene basalt lava flow, Staffa (and Fingal's Cave). ~~[http://bgsintranet/asset-bank/action/viewFullSizedImage?id=125991&size=1000~~ P580464.]		Image:P580464.jpg\|Columnar jointing in a thick Palaeogene basalt lava flow, Staffa (and Fingal's Cave). P580464.
	Image:P000770.jpg\|Jointing in the upper part of the lava flow is chaotic but is spectacularly regular in the lower part, which rests on a bed of volcaniclastic rock. [http://~~bgsintranet~~/asset-bank/action/~~viewFullSizedImage~~?id=2068&~~size~~=~~1000~~ P000770.]		Image:P000770.jpg\|Jointing in the upper part of the lava flow is chaotic but is spectacularly regular in the lower part, which rests on a bed of volcaniclastic rock. [http://geoscenic.bgs.ac.uk/asset-bank/action/viewAsset?id=2068&index=0&total=1&view=viewSearchItem P000770.]
	Image:P580487.jpg\|The hills of northern Arran, composed of Palaeogene granite from the Arran Central Complex. ~~[http://bgsintranet/asset-bank/action/viewFullSizedImage?id=126058&size=1000~~ P580487.]		Image:P580487.jpg\|The hills of northern Arran, composed of Palaeogene granite from the Arran Central Complex. P580487.
	Image:P580475.jpg\|Well-developed mineral layering in a Palaeogene gabbro from the Cuillin sector of the Skye Central Complex, Maell na Cuilce, Skye. ~~[http://bgsintranet/asset-bank/action/viewFullSizedImage?id=126022&size=1000~~ P580475.]		Image:P580475.jpg\|Well-developed mineral layering in a Palaeogene gabbro from the Cuillin sector of the Skye Central Complex, Maell na Cuilce, Skye. P580475.
	</gallery>		</gallery>

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	[[Image:P001078.jpg\|thumb\|left\|200px\|A Palaeogene dolerite dyke left standing by the erosion of the Devonian sandstone into which it was intruded, Great Cumbrae, Firth of Clyde. [http://~~bgsintranet~~/asset-bank/action/~~viewFullSizedImage~~?id=2376&~~size~~=~~1000~~ P001078.]]]		[[Image:P001078.jpg\|thumb\|left\|200px\|A Palaeogene dolerite dyke left standing by the erosion of the Devonian sandstone into which it was intruded, Great Cumbrae, Firth of Clyde. [http://geoscenic.bgs.ac.uk/asset-bank/action/viewAsset?id=2376&index=0&total=1&view=viewSearchItem P001078.]]]

	'''Many of the mafic dykes''' that make up the regional swarms are less than a metre across, although dykes up to 10 m across are fairly common ('''Plate P001078'''). A few even broader ones have been recorded but these may be composite intrusions. Nearly all of the dykes consist of basalt and/or dolerite. The Skye and Mull central complexes were the major sources of dyke swarms that extend from the Outer Hebrides and St Kilda (itself formed by a Palaeogene central complex) south-east across southern Scotland and into northern England. Dykes in Northern Ireland focus on the Slieve Gullion Ring-complex and the Mourne Mountains plutonic centres, but the regional swarms extend from Rockall (another Palaeogene granite) in the north west, to Wales and the English Midlands in the south-east.		'''Many of the mafic dykes''' that make up the regional swarms are less than a metre across, although dykes up to 10 m across are fairly common ('''Plate P001078'''). A few even broader ones have been recorded but these may be composite intrusions. Nearly all of the dykes consist of basalt and/or dolerite. The Skye and Mull central complexes were the major sources of dyke swarms that extend from the Outer Hebrides and St Kilda (itself formed by a Palaeogene central complex) south-east across southern Scotland and into northern England. Dykes in Northern Ireland focus on the Slieve Gullion Ring-complex and the Mourne Mountains plutonic centres, but the regional swarms extend from Rockall (another Palaeogene granite) in the north west, to Wales and the English Midlands in the south-east.