Wales - an introduction - Revision history

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	TRUEMAN, A E. 1924. The species concept in palaeontology. ''Geological Magazine'', Vol. 61, 335–340.		TRUEMAN, A E. 1924. The species concept in palaeontology. ''Geological Magazine'', Vol. 61, 335–340.

	{{British regional geology of Wales - contents}}		{{British regional geology of Wales - contents}}
	[[Category:Regional Geology of Wales]]		[[Category:Regional Geology of Wales]]

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	[[File:P916142.jpg\|thumbnail\|Geology of Wales. P916142.]]		[[File:P916142.jpg\|thumbnail\|Geology of Wales. P916142.]]
	[[File:P916143.jpg\|thumbnail\|Topography of Wales and adjacent area. P916143.]]		[[File:P916143.jpg\|thumbnail\|Topography of Wales and adjacent area. P916143.]]
	[[File:P662385.jpg\|thumbnail\|Snowdon massif viewed from the east, at Curig Hill across Llynnau Mymbyr to the Snowdon Horseshoe, Llewedd, Yr Wyddfa, Crib y Ddysgl and Crib Goch. (MFH P662385. ]]		[[File:P662385.jpg\|thumbnail\|Snowdon massif viewed from the east, at Curig Hill across Llynnau Mymbyr to the Snowdon Horseshoe, Llewedd, Yr Wyddfa, Crib y Ddysgl and Crib Goch. (MFH P662385). ]]
	[[File:P662386.jpg\|thumbnail\|North Pembrokeshire coast viewed westwards from Carn Llidi, across Whitesands Bay to Ramsey Island (C D R Evans P662386. ]]		[[File:P662386.jpg\|thumbnail\|North Pembrokeshire coast viewed westwards from Carn Llidi, across Whitesands Bay to Ramsey Island (C D R Evans P662386). ]]
	[[File:P662387.jpg\|thumbnail\|Great Ormes Head, Llandudno. The Loggerheads Limestone Formation is exposed in the main cliff face with a capping of the Cefn Mawr Limestone and Red Wharf Limestone formations (MFH P662387. ]]		[[File:P662387.jpg\|thumbnail\|Great Ormes Head, Llandudno. The Loggerheads Limestone Formation is exposed in the main cliff face with a capping of the Cefn Mawr Limestone and Red Wharf Limestone formations (MFH P662387). ]]
	This book describes the geology of Wales that is shown on the 1:625 000 scale geological map of the Principality of Wales and replaces earlier editions of this series in which north and south Wales were described in separate volumes. Unlike the earlier editions, some of the most pertinent data, retrieved in recent years, from the offshore areas, Liverpool Bay, Caernarfon Bay, Cardigan Bay and the Bristol Channel, have been included. These data serve to complete the geological history and context of Wales and especially so in reference to plate tectonic models.		This book describes the geology of Wales that is shown on the 1:625 000 scale geological map of the Principality of Wales and replaces earlier editions of this series in which north and south Wales were described in separate volumes. Unlike the earlier editions, some of the most pertinent data, retrieved in recent years, from the offshore areas, Liverpool Bay, Caernarfon Bay, Cardigan Bay and the Bristol Channel, have been included. These data serve to complete the geological history and context of Wales and especially so in reference to plate tectonic models.

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	~~__NOTOC__~~
	'''From: Howells, M F. 2007. [[British regional geology: Wales\|British regional geology: Wales]]. Keyworth, Nottingham: British Geological Survey.'''		'''From: Howells, M F. 2007. [[British regional geology: Wales\|British regional geology: Wales]]. Keyworth, Nottingham: British Geological Survey.'''

	'''Maps:'''		'''Maps:'''

	[http://www.bgs.ac.uk/data/maps/maps.cfc?method=viewRecord&mapId=12075 1:250~~ ~~000 map of Wales]		[http://www.bgs.ac.uk/data/maps/maps.cfc?method=viewRecord&mapId=12075 1:250,000 map of Wales]

	[http://www.bgs.ac.uk/data/maps/home.html Other maps including the 1:50~~ ~~000 maps covering Wales]		[http://www.bgs.ac.uk/data/maps/home.html Other maps including the 1:50,000 maps covering Wales]

	[http://www.bgs.ac.uk/discoveringGeology/geologyOfBritain/viewer.html Geology of Britain viewer]		[http://www.bgs.ac.uk/discoveringGeology/geologyOfBritain/viewer.html Geology of Britain viewer]
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	Within Wales and the adjacent sea, elements of all the major geological systems are to be found [[Media:P916216.jpg\|(P916216)]], and for much of the country the differences in the geology [[Media:P916142.jpg\|(P916142)]] and map in back pocket) are reflected in the topography [[Media:P916143.jpg\|(P916143)]] and the scenery. The main exception is the low-lying coastal area of south Wales, between south Glamorgan and Pembrokeshire, which is underlain by folded Palaeozoic rocks but lacks the topographical features of similar strata at higher elevations inland. The contrast reflects a difference in the erosional history, with the coastal areas having been submerged and repeatedly eroded by the sea in more recent geological times.		Within Wales and the adjacent sea, elements of all the major geological systems are to be found [[Media:P916216.jpg\|(P916216)]], and for much of the country the differences in the geology [[Media:P916142.jpg\|(P916142)]] and map in back pocket) are reflected in the topography [[Media:P916143.jpg\|(P916143)]] and the scenery. The main exception is the low-lying coastal area of south Wales, between south Glamorgan and Pembrokeshire, which is underlain by folded Palaeozoic rocks but lacks the topographical features of similar strata at higher elevations inland. The contrast reflects a difference in the erosional history, with the coastal areas having been submerged and repeatedly eroded by the sea in more recent geological times.

	In Anglesey and Llŷn, there is the largest outcrop of Precambrian rocks in southern Britain, and smaller outcrops occur in Pembrokeshire, Carmarthenshire and Radnorshire. However, Wales is dominated by Lower Palaeozoic rocks — the Cambrian and Ordovician in Llŷn, Snowdonia National Park and north Pembrokeshire and the Silurian over much of central Wales. The sequence is mainly of marine sedimentary rocks, and the recognition of distinctive facies and thickness changes across the outcrops has allowed detailed reconstruction of a marine basin and its shorelines throughout this time. Within the Cambrian, the sedimentary rocks range from silty mudstone, such as those displayed in the great quarries between Nantlle and Bethesda in the north Wales slate belt, and coarse-grained sandstone, as exposed in the castellated ridges of the Rhinog Mountains. The basin in which the sediments accumulated was initiated by major fractures in the Precambrian basement and its evolution was controlled by periodic tectonic activity along these fractures, causing both uplift and subsidence. During Ordovician times, volcanic activity was a major feature and the thick accumulations of widely variable volcanic rocks profoundly modified the sedimentary environments. The spectacular scenery throughout the Snowdonia National Park is due largely to the volcanic rocks and their resistance to weathering [[Media:P662385.jpg\|(P662385)]]. Similarly, in Pembrokeshire, the indented coastline around the northern headland of St Bride’s Bay [[Media:P662386.jpg\|(P662386)]] reflects the differing resistance to erosion of the volcanic rocks and the interbedded, less competent sedimentary rocks. In late Ordovician and Silurian times, when major volcanic activity had ceased, sedimentation was dominated by fine silt and mud which, when lithified, uplifted and eroded, produced the characteristically smooth profiles of the hills through much of central Wales and the Denbigh moors (Mynydd Hiraethog).		In Anglesey and Llŷn, there is the largest outcrop of Precambrian rocks in southern Britain, and smaller outcrops occur in Pembrokeshire, Carmarthenshire and Radnorshire. However, Wales is dominated by Lower Palaeozoic rocks — the Cambrian and Ordovician in Llŷn, Snowdonia National Park and north Pembrokeshire and the Silurian over much of central Wales. The sequence is mainly of marine sedimentary rocks, and the recognition of distinctive facies and thickness changes across the outcrops has allowed detailed reconstruction of a marine basin and its shorelines throughout this time. Within the Cambrian, the sedimentary rocks range from silty mudstone, such as those displayed in the great quarries between Nantlle and Bethesda in the north Wales slate belt, and coarse-grained sandstone, as exposed in the castellated ridges of the Rhinog Mountains. The basin in which the sediments accumulated was initiated by major fractures in the Precambrian basement and its evolution was controlled by periodic tectonic activity along these fractures, causing both uplift and subsidence. During Ordovician times, volcanic activity was a major feature and the thick accumulations of widely variable volcanic rocks profoundly modified the sedimentary environments. The spectacular scenery throughout the Snowdonia National Park is due largely to the volcanic rocks and their resistance to weathering [[Media:P662385.jpg\|(P662385)]]. Similarly, in Pembrokeshire, the indented coastline around the northern headland of St Bride’s Bay [[Media:P662386.jpg\|(P662386)]] reflects the differing resistance to erosion of the volcanic rocks and the interbedded, less competent sedimentary rocks. In late Ordovician and Silurian times, when major volcanic activity had ceased, sedimentation was dominated by fine silt and mud which, when lithified, uplifted and eroded, produced the characteristically smooth profiles of the hills through much of central Wales and the Denbigh moors (Mynydd Hiraethog).

	During late Silurian and early Devonian times, the Lower Palaeozoic basin contracted and the rocks were folded and uplifted in the final phase (Acadian) of the Caledonian orogeny to form part of a continental surface that extended from the position of the Bristol Channel into northern Britain; at this time the sea lay to the south. The major folds of this orogeny in Wales, such as the Harlech and Berwyn ‘domes’ and the intervening Central Wales Syncline, can be discerned in the current topography. Similarly, the line of the Bala Fault Zone and its branch along Tal y Llyn and the Dysynni valley is well featured. The emergent land was the site of fluvial, alluvial and lacustrine sedimentation, which produced the Old Red Sandstone continental facies in late Silurian and Devonian times. These Old Red Sandstone rocks are well exposed from Pembrokeshire in the west, through the scarp feature of the Black Mountains and Brecon Beacons, to Herefordshire in the east, and for much of this outcrop they lie with marked discordance on the eroded surface of the folded Lower Palaeozoic sequence. The rich agricultural terrain in the lower ground of the Old Red Sandstone outcrops contrasts sharply with the relatively impoverished ground at similar altitudes in the Lower Palaeozoic outcrops. The absence of Middle Devonian rocks across Wales reflects uplift, possibly the final expression of the Caledonian orogeny. As a result, the Upper Old Red Sandstone sequence is incomplete and everywhere rests unconformably on older strata. The appearance of marine fossils towards the top of this sequence indicates the initiation of a marine transgression, from the south, which reached its full expression in early Carboniferous times.		During late Silurian and early Devonian times, the Lower Palaeozoic basin contracted and the rocks were folded and uplifted in the final phase (Acadian) of the Caledonian orogeny to form part of a continental surface that extended from the position of the Bristol Channel into northern Britain; at this time the sea lay to the south. The major folds of this orogeny in Wales, such as the Harlech and Berwyn ‘domes’ and the intervening Central Wales Syncline, can be discerned in the current topography. Similarly, the line of the Bala Fault Zone and its branch along Tal y Llyn and the Dysynni valley is well featured. The emergent land was the site of fluvial, alluvial and lacustrine sedimentation, which produced the Old Red Sandstone continental facies in late Silurian and Devonian times. These Old Red Sandstone rocks are well exposed from Pembrokeshire in the west, through the scarp feature of the Black Mountains and Brecon Beacons, to Herefordshire in the east, and for much of this outcrop they lie with marked discordance on the eroded surface of the folded Lower Palaeozoic sequence. The rich agricultural terrain in the lower ground of the Old Red Sandstone outcrops contrasts sharply with the relatively impoverished ground at similar altitudes in the Lower Palaeozoic outcrops. The absence of Middle Devonian rocks across Wales reflects uplift, possibly the final expression of the Caledonian orogeny. As a result, the Upper Old Red Sandstone sequence is incomplete and everywhere rests unconformably on older strata. The appearance of marine fossils towards the top of this sequence indicates the initiation of a marine transgression, from the south, which reached its full expression in early Carboniferous times.
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	TRUEMAN, A E. 1924. The species concept in palaeontology. ''Geological Magazine'', Vol. 61, 335–340.		TRUEMAN, A E. 1924. The species concept in palaeontology. ''Geological Magazine'', Vol. 61, 335–340.
	{{British regional geology of Wales}}
			{{British regional geology of Wales - contents}}
	[[Category:Regional Geology of Wales]]		[[Category:Regional Geology of Wales]]

Dbk at 07:36, 14 April 2016

2016-04-14T07:36:20Z

← Older revision		Revision as of 08:36, 14 April 2016
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			__NOTOC__
	'''From: Howells, M F. 2007. [[British regional geology: Wales\|British regional geology: Wales]]. Keyworth, Nottingham: British Geological Survey.'''		'''From: Howells, M F. 2007. [[British regional geology: Wales\|British regional geology: Wales]]. Keyworth, Nottingham: British Geological Survey.'''

	'''Maps:'''		'''Maps:'''

	[http://www.bgs.ac.uk/data/maps/maps.cfc?method=viewRecord&mapId=12075 1:250,000 map of Wales]		[http://www.bgs.ac.uk/data/maps/maps.cfc?method=viewRecord&mapId=12075 1:250 000 map of Wales]

	[http://www.bgs.ac.uk/data/maps/home.html Other maps including the 1:50,000 maps covering Wales]		[http://www.bgs.ac.uk/data/maps/home.html Other maps including the 1:50 000 maps covering Wales]

	[http://www.bgs.ac.uk/discoveringGeology/geologyOfBritain/viewer.html Geology of Britain viewer]		[http://www.bgs.ac.uk/discoveringGeology/geologyOfBritain/viewer.html Geology of Britain viewer]
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	[[File:P662386.jpg\|thumbnail\|North Pembrokeshire coast viewed westwards from Carn Llidi, across Whitesands Bay to Ramsey Island (C D R Evans P662386. ]]		[[File:P662386.jpg\|thumbnail\|North Pembrokeshire coast viewed westwards from Carn Llidi, across Whitesands Bay to Ramsey Island (C D R Evans P662386. ]]
	[[File:P662387.jpg\|thumbnail\|Great Ormes Head, Llandudno. The Loggerheads Limestone Formation is exposed in the main cliff face with a capping of the Cefn Mawr Limestone and Red Wharf Limestone formations (MFH P662387. ]]		[[File:P662387.jpg\|thumbnail\|Great Ormes Head, Llandudno. The Loggerheads Limestone Formation is exposed in the main cliff face with a capping of the Cefn Mawr Limestone and Red Wharf Limestone formations (MFH P662387. ]]
	This book describes the geology of Wales that is shown on the 1:625 000 scale geological map of the Principality of Wales and replaces earlier editions of this series in which north and south Wales were described in separate volumes. Unlike the earlier editions, some of the most pertinent data, retrieved in recent years, from the offshore areas, Liverpool Bay, Caernarfon Bay, Cardigan Bay and the Bristol Channel, have been included. These data serve to complete the geological history and context of Wales and especially so in reference to plate tectonic models.		This book describes the geology of Wales that is shown on the 1:625 000 scale geological map of the Principality of Wales and replaces earlier editions of this series in which north and south Wales were described in separate volumes. Unlike the earlier editions, some of the most pertinent data, retrieved in recent years, from the offshore areas, Liverpool Bay, Caernarfon Bay, Cardigan Bay and the Bristol Channel, have been included. These data serve to complete the geological history and context of Wales and especially so in reference to plate tectonic models.

	Within Wales and the adjacent sea, elements of all the major geological systems are to be found [[Media:P916216.jpg\|(P916216)]], and for much of the country the differences in the geology [[Media:P916142.jpg\|(P916142)]] and map in back pocket) are reflected in the topography [[Media:P916143.jpg\|(P916143)]] and the scenery. The main exception is the low-lying coastal area of south Wales, between south Glamorgan and Pembrokeshire, which is underlain by folded Palaeozoic rocks but lacks the topographical features of similar strata at higher elevations inland. The contrast reflects a difference in the erosional history, with the coastal areas having been submerged and repeatedly eroded by the sea in more recent geological times.		Within Wales and the adjacent sea, elements of all the major geological systems are to be found [[Media:P916216.jpg\|(P916216)]], and for much of the country the differences in the geology [[Media:P916142.jpg\|(P916142)]] and map in back pocket) are reflected in the topography [[Media:P916143.jpg\|(P916143)]] and the scenery. The main exception is the low-lying coastal area of south Wales, between south Glamorgan and Pembrokeshire, which is underlain by folded Palaeozoic rocks but lacks the topographical features of similar strata at higher elevations inland. The contrast reflects a difference in the erosional history, with the coastal areas having been submerged and repeatedly eroded by the sea in more recent geological times.
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	TRUEMAN, A E. 1924. The species concept in palaeontology. ''Geological Magazine'', Vol. 61, 335–340.		TRUEMAN, A E. 1924. The species concept in palaeontology. ''Geological Magazine'', Vol. 61, 335–340.
			{{British regional geology of Wales}}
	{{British regional geology of Wales ~~- contents~~}}
	[[Category:Regional Geology of Wales]]		[[Category:Regional Geology of Wales]]

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	{{British regional geology of Wales - contents}}		{{British regional geology of Wales - contents}}
	[[Category:Regional Geology of Wales]]		[[Category:Regional Geology of Wales]]
	~~[[Category:Wales]]~~

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	{{British regional geology of Wales - contents}}		{{British regional geology of Wales - contents}}
			[[Category:Regional Geology of Wales]]
	[[Category:Wales]]		[[Category:Wales]]

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← Older revision		Revision as of 08:20, 14 April 2016
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	TRUEMAN, A E. 1924. The species concept in palaeontology. ''Geological Magazine'', Vol. 61, 335–340.		TRUEMAN, A E. 1924. The species concept in palaeontology. ''Geological Magazine'', Vol. 61, 335–340.

	{{~~Regional~~ geology of Wales - contents}}		{{British regional geology of Wales - contents}}

	[[Category:Wales]]		[[Category:Wales]]

Dbk at 07:19, 14 April 2016

2016-04-14T07:19:28Z

← Older revision		Revision as of 08:19, 14 April 2016
Line 57:		Line 57:

	TRUEMAN, A E. 1924. The species concept in palaeontology. ''Geological Magazine'', Vol. 61, 335–340.		TRUEMAN, A E. 1924. The species concept in palaeontology. ''Geological Magazine'', Vol. 61, 335–340.

			{{Regional geology of Wales - contents}}

	[[Category:Wales]]		[[Category:Wales]]

Dbk: 1 revision imported

2016-04-14T06:37:46Z

1 revision imported

← Older revision	Revision as of 07:37, 14 April 2016
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← Older revision		Revision as of 09:14, 14 April 2016
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	[[File:P916142.jpg\|thumbnail\|Geology of Wales. P916142.]]		[[File:P916142.jpg\|thumbnail\|Geology of Wales. P916142.]]
	[[File:P916143.jpg\|thumbnail\|Topography of Wales and adjacent area. P916143.]]		[[File:P916143.jpg\|thumbnail\|Topography of Wales and adjacent area. P916143.]]
	[[File:P662385.jpg\|thumbnail\|Snowdon massif viewed from the east, at Curig Hill across Llynnau Mymbyr to the Snowdon Horseshoe, Llewedd, Yr Wyddfa, Crib y Ddysgl and Crib Goch. (MFH P662385. ]]		[[File:P662385.jpg\|thumbnail\|Snowdon massif viewed from the east, at Curig Hill across Llynnau Mymbyr to the Snowdon Horseshoe, Llewedd, Yr Wyddfa, Crib y Ddysgl and Crib Goch. (MFH P662385). ]]
	[[File:P662386.jpg\|thumbnail\|North Pembrokeshire coast viewed westwards from Carn Llidi, across Whitesands Bay to Ramsey Island (C D R Evans P662386. ]]		[[File:P662386.jpg\|thumbnail\|North Pembrokeshire coast viewed westwards from Carn Llidi, across Whitesands Bay to Ramsey Island (C D R Evans P662386). ]]
	[[File:P662387.jpg\|thumbnail\|Great Ormes Head, Llandudno. The Loggerheads Limestone Formation is exposed in the main cliff face with a capping of the Cefn Mawr Limestone and Red Wharf Limestone formations (MFH P662387. ]]		[[File:P662387.jpg\|thumbnail\|Great Ormes Head, Llandudno. The Loggerheads Limestone Formation is exposed in the main cliff face with a capping of the Cefn Mawr Limestone and Red Wharf Limestone formations (MFH P662387). ]]
	This book describes the geology of Wales that is shown on the 1:625 000 scale geological map of the Principality of Wales and replaces earlier editions of this series in which north and south Wales were described in separate volumes. Unlike the earlier editions, some of the most pertinent data, retrieved in recent years, from the offshore areas, Liverpool Bay, Caernarfon Bay, Cardigan Bay and the Bristol Channel, have been included. These data serve to complete the geological history and context of Wales and especially so in reference to plate tectonic models.		This book describes the geology of Wales that is shown on the 1:625 000 scale geological map of the Principality of Wales and replaces earlier editions of this series in which north and south Wales were described in separate volumes. Unlike the earlier editions, some of the most pertinent data, retrieved in recent years, from the offshore areas, Liverpool Bay, Caernarfon Bay, Cardigan Bay and the Bristol Channel, have been included. These data serve to complete the geological history and context of Wales and especially so in reference to plate tectonic models.