Bedrock Geology UK South: Cenozoic - Revision history

Dbk at 16:10, 28 July 2015

2015-07-28T16:10:08Z

← Older revision		Revision as of 17:10, 28 July 2015
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	[[Image:P785840.jpg\|thumb\|200px\|P785840.]]		[[Image:P785840.jpg\|thumb\|200px\|P785840.]]

	'''The Cenozoic Era is named from the Greek meaning ‘new life’''', and is the time when modern life forms as we know them began to ~~flourish—mammals~~, grass, the flowering plants and the insects that pollinate them. At the start of this era many Mesozoic forms became extinct, not only the dinosaurs but also ammonites, belemnites, many bivalves and chalk-forming nanoplankton.		'''The Cenozoic Era is named from the Greek meaning ‘new life’''', and is the time when modern life forms as we know them began to flourish — mammals, grass, the flowering plants and the insects that pollinate them. At the start of this era many Mesozoic forms became extinct, not only the dinosaurs but also ammonites, belemnites, many bivalves and chalk-forming nanoplankton.

	'''At the beginning of the Cenozoic the British Isles''' lay at a latitude of 43º to 47ºN, and since then has moved north to its present position ([[:File:P785800.jpg\|'''Figure P785800g''']]). The climate has cooled progressively since the late Cretaceous, and may have been somewhat arid at times, but in the early part of the Palaeogene it was warm, supporting a lush vegetation.		'''At the beginning of the Cenozoic the British Isles''' lay at a latitude of 43º to 47ºN, and since then has moved north to its present position ([[:File:P785800.jpg\|'''Figure P785800g''']]). The climate has cooled progressively since the late Cretaceous, and may have been somewhat arid at times, but in the early part of the Palaeogene it was warm, supporting a lush vegetation.
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	[[Image:P649780.jpg\|thumb\|left\|200px\|Alum Bay, Isle of Wight. P649780.]]		[[Image:P649780.jpg\|thumb\|left\|200px\|Alum Bay, Isle of Wight. P649780.]]

	'''The Thanet Sand Formation''' (up to 30m thick) is a pale yellowish grey colour where it is weathered near the surface, and has been burrowed extensively by marine creatures so that few bedding structures remain. At the base is the Bullhead Bed, flint pebbles and cobbles in a matrix of clay with sand grains that are likely to have had their source in the Moine and Dalradian rocks of the Scottish Highlands. The Lambeth Group (G2) is up to 20m thick and has three formations. The Upnor Formation contains an abundance of well-rounded flint pebbles, shoreface deposits, and tidal sands ('''Plate P211781'''). Most of the mineral grains have a Scottish origin, but some indicate a different provenance, perhaps Armorica, Ardennes or the granites of south-west England. The Woolwich Formation, in the east, is a marine facies and shows a strong cyclicity in the pattern of sand, clay, pebble and shell beds. The shell beds have provided an abundance of fossils for the local museums over the years. The Reading Formation, in the west, was deposited on an alluvial plain where soil developed when conditions allowed. The sediments are particularly well exposed on the west coast of the Isle of Wight where they weather to a range of ~~colours—yellow~~, brown, orange, red and ~~purple—depending~~ on the iron minerals that are present in the silty or sandy clay.		'''The Thanet Sand Formation''' (up to 30m thick) is a pale yellowish grey colour where it is weathered near the surface, and has been burrowed extensively by marine creatures so that few bedding structures remain. At the base is the Bullhead Bed, flint pebbles and cobbles in a matrix of clay with sand grains that are likely to have had their source in the Moine and Dalradian rocks of the Scottish Highlands. The Lambeth Group (G2) is up to 20m thick and has three formations. The Upnor Formation contains an abundance of well-rounded flint pebbles, shoreface deposits, and tidal sands ('''Plate P211781'''). Most of the mineral grains have a Scottish origin, but some indicate a different provenance, perhaps Armorica, Ardennes or the granites of south-west England. The Woolwich Formation, in the east, is a marine facies and shows a strong cyclicity in the pattern of sand, clay, pebble and shell beds. The shell beds have provided an abundance of fossils for the local museums over the years. The Reading Formation, in the west, was deposited on an alluvial plain where soil developed when conditions allowed. The sediments are particularly well exposed on the west coast of the Isle of Wight where they weather to a range of colours — yellow, brown, orange, red and purple — depending on the iron minerals that are present in the silty or sandy clay.

	'''The Harwich Formation''' (up to 10m thick; G3) is the oldest part of the Thames Group and consists of clay, cementstone and ash beds in the Harwich area with sand and pebbles in the London Basin. In places pebbles dominate and form stacked channel infills with large foresets and imbrication. Calcareous mollusc fossils and scattered sharks’ teeth are typical fossils. The London Clay Formation is present in both the London and Hampshire basins, and is up to 130m thick. It is a grey to blue-grey clay that weathers to a brown colour. The clay was deposited entirely in marine conditions during a number of transgressive-regressive episodes that can be correlated between the two basins.		'''The Harwich Formation''' (up to 10m thick; G3) is the oldest part of the Thames Group and consists of clay, cementstone and ash beds in the Harwich area with sand and pebbles in the London Basin. In places pebbles dominate and form stacked channel infills with large foresets and imbrication. Calcareous mollusc fossils and scattered sharks’ teeth are typical fossils. The London Clay Formation is present in both the London and Hampshire basins, and is up to 130m thick. It is a grey to blue-grey clay that weathers to a brown colour. The clay was deposited entirely in marine conditions during a number of transgressive-regressive episodes that can be correlated between the two basins.
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	= Cimmerian–Alpine cycle =		= Cimmerian–Alpine cycle =

	[[Image:P005798.jpg\|thumb\|200px\|Alpine folds in Jurassic and Lower Cretaceous strata, Lulworth Cove. [http://geoscenic.bgs.ac.uk/asset-bank/action/viewAsset?id=5054&index=0&total=1&view=viewSearchItem P005798.]]]		[[Image:P005798.jpg\|thumb\|200px\|Alpine folds in Jurassic and Lower Cretaceous strata, Lulworth Cove. [http://geoscenic.bgs.ac.uk/asset-bank/action/viewAsset?id=5054&index=0&total=1&view=viewSearchItem P005798.]]]

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	[[Image:P785829.jpg\|thumb\|center\|600px\|Schematic cross-section of the Wessex Basin. P785829.]]		[[Image:P785829.jpg\|thumb\|center\|600px\|Schematic cross-section of the Wessex Basin. P785829.]]

	'''The major processes that have influenced the rock record''' in the ~~past—continental~~ rifting, thermal uplift and subsidence, compression, climate change, sea-level change and oceanic circulation—have all affected the Cenozoic rocks and serve to illustrate how narrow our picture of the earlier periods really is, and how difficult it is to separate the various effects of these processes.		'''The major processes that have influenced the rock record''' in the past — continental rifting, thermal uplift and subsidence, compression, climate change, sea-level change and oceanic circulation—have all affected the Cenozoic rocks and serve to illustrate how narrow our picture of the earlier periods really is, and how difficult it is to separate the various effects of these processes.

	==Bedrock Geology UK South - contents==		==Bedrock Geology UK South — contents==
	{{bedrockSouth}}		{{bedrockSouth}}


	[[Category:Bedrock Geology UK South\| 10]]		[[Category:Bedrock Geology UK South\| 10]]

Dbk at 14:30, 29 January 2015

2015-01-29T14:30:05Z

← Older revision		Revision as of 15:30, 29 January 2015
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	'''The major processes that have influenced the rock record''' in the past—continental rifting, thermal uplift and subsidence, compression, climate change, sea-level change and oceanic circulation—have all affected the Cenozoic rocks and serve to illustrate how narrow our picture of the earlier periods really is, and how difficult it is to separate the various effects of these processes.		'''The major processes that have influenced the rock record''' in the past—continental rifting, thermal uplift and subsidence, compression, climate change, sea-level change and oceanic circulation—have all affected the Cenozoic rocks and serve to illustrate how narrow our picture of the earlier periods really is, and how difficult it is to separate the various effects of these processes.

			==Bedrock Geology UK South - contents==
			{{bedrockSouth}}


	[[Category:Bedrock Geology UK South\| 10]]		[[Category:Bedrock Geology UK South\| 10]]

Dbk at 12:33, 19 June 2014

2014-06-19T12:33:08Z

← Older revision		Revision as of 13:33, 19 June 2014
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	[[Category:Bedrock Geology UK South\| 1]]		[[Category:Bedrock Geology UK South\| 10]]

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

2014-06-19T12:31:33Z

65 million years ago to the present day

← Older revision		Revision as of 13:31, 19 June 2014
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	'''The Cenozoic Era is named from the Greek meaning ‘new life’''', and is the time when modern life forms as we know them began to flourish—mammals, grass, the flowering plants and the insects that pollinate them. At the start of this era many Mesozoic forms became extinct, not only the dinosaurs but also ammonites, belemnites, many bivalves and chalk-forming nanoplankton.		'''The Cenozoic Era is named from the Greek meaning ‘new life’''', and is the time when modern life forms as we know them began to flourish—mammals, grass, the flowering plants and the insects that pollinate them. At the start of this era many Mesozoic forms became extinct, not only the dinosaurs but also ammonites, belemnites, many bivalves and chalk-forming nanoplankton.

	'''At the beginning of the Cenozoic the British Isles''' lay at a latitude of 43º to 47ºN, and since then has moved north to its present position ('''Figure P785800g'''). The climate has cooled progressively since the late Cretaceous, and may have been somewhat arid at times, but in the early part of the Palaeogene it was warm, supporting a lush vegetation.		'''At the beginning of the Cenozoic the British Isles''' lay at a latitude of 43º to 47ºN, and since then has moved north to its present position ([[:File:P785800.jpg\|'''Figure P785800g''']]). The climate has cooled progressively since the late Cretaceous, and may have been somewhat arid at times, but in the early part of the Palaeogene it was warm, supporting a lush vegetation.

	[[Image:P785826.jpg\|thumb\|200px\|Early Palaeogene palaeogeographical sketch map. P785826.]]		[[Image:P785826.jpg\|thumb\|200px\|Early Palaeogene palaeogeographical sketch map. P785826.]]

Dbk at 12:27, 19 June 2014

2014-06-19T12:27:58Z

← Older revision		Revision as of 13:27, 19 June 2014
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			__NOTOC__
	{{BedS}}		{{BedS}}
	==65 million years ago to the present day==		==65 million years ago to the present day==

Jeth1 at 09:51, 17 June 2014

2014-06-17T09:51:32Z

← Older revision		Revision as of 10:51, 17 June 2014
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	'''The Cenozoic Era is named from the Greek meaning ‘new life’''', and is the time when modern life forms as we know them began to flourish—mammals, grass, the flowering plants and the insects that pollinate them. At the start of this era many Mesozoic forms became extinct, not only the dinosaurs but also ammonites, belemnites, many bivalves and chalk-forming nanoplankton.		'''The Cenozoic Era is named from the Greek meaning ‘new life’''', and is the time when modern life forms as we know them began to flourish—mammals, grass, the flowering plants and the insects that pollinate them. At the start of this era many Mesozoic forms became extinct, not only the dinosaurs but also ammonites, belemnites, many bivalves and chalk-forming nanoplankton.

	'''At the beginning of the Cenozoic the British Isles''' lay at a latitude of 43º to 47ºN, and since then has moved north to its present position ('''Figure 4g'''). The climate has cooled progressively since the late Cretaceous, and may have been somewhat arid at times, but in the early part of the Palaeogene it was warm, supporting a lush vegetation.		'''At the beginning of the Cenozoic the British Isles''' lay at a latitude of 43º to 47ºN, and since then has moved north to its present position ('''Figure P785800g'''). The climate has cooled progressively since the late Cretaceous, and may have been somewhat arid at times, but in the early part of the Palaeogene it was warm, supporting a lush vegetation.

	[[Image:P785826.jpg\|thumb\|200px\|Early Palaeogene palaeogeographical sketch map. P785826.]]		[[Image:P785826.jpg\|thumb\|200px\|Early Palaeogene palaeogeographical sketch map. P785826.]]

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

2014-06-11T12:27:35Z

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

← Older revision		Revision as of 13:27, 11 June 2014
(No difference)

Dbk at 10:09, 20 May 2014

2014-05-20T10:09:32Z

Dbk: /* Cimmerian–Alpine cycle */

2014-05-16T07:37:55Z

Cimmerian–Alpine cycle

← Older revision		Revision as of 08:37, 16 May 2014
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	= Cimmerian–Alpine cycle =		= Cimmerian–Alpine cycle =

	~~{\| class="wikitable" width="100pt" style="margin-left~~:~~40px; margin-right:0px; margin-bottom:10px; float:right; text-align:left;"~~		[[Image:P005798.jpg\|thumb\|200px\|Alpine folds in Jurassic and Lower Cretaceous strata, Lulworth Cove. [http://bgsintranet/asset-bank/action/viewFullSizedImage?id=5054&size=1000 P005798.]]]
	\| ~~<img src="http://bgsintranet/asset-bank/action/directLinkImage?assetId=5054&width=200&height=150">~~
	\|-
	\| Alpine folds in Jurassic and Lower Cretaceous strata, Lulworth Cove. [http://bgsintranet/asset-bank/action/viewFullSizedImage?id=5054&size=1000 P005798.]
	\|}

	'''The break up of the continent of Pangaea''' and the opening of the North Atlantic has dominated the tectonic history of the UK since Permian times. Extensional faults, many of which were reactivated older structures, controlled the development of the Mesozoic sedimentary basins of Cleveland, Cheshire, Worcester and Wessex. Sediments accumulated in these intracontinental sags during the Triassic and Jurassic, while considerably thicker sequences collected in the deeper offshore rifts of the North Sea and Irish Sea. In mid Jurassic times, thermal doming in the North Sea resulted in uplift and erosion over much of northern and eastern Britain, producing the Mid Cimmerian unconformity. As the thermal energy dissipated, subsidence and sedimentation continued into the late Jurassic and early Cretaceous when a further period of uplift and erosion occurred, marked by the Late Cimmerian unconformity. Regional subsidence during the Cretaceous resulted in gradual submergence of most of Britain. Compression and basin inversion at the end of the Cretaceous Period brought this episode of basin development to a close.		'''The break up of the continent of Pangaea''' and the opening of the North Atlantic has dominated the tectonic history of the UK since Permian times. Extensional faults, many of which were reactivated older structures, controlled the development of the Mesozoic sedimentary basins of Cleveland, Cheshire, Worcester and Wessex. Sediments accumulated in these intracontinental sags during the Triassic and Jurassic, while considerably thicker sequences collected in the deeper offshore rifts of the North Sea and Irish Sea. In mid Jurassic times, thermal doming in the North Sea resulted in uplift and erosion over much of northern and eastern Britain, producing the Mid Cimmerian unconformity. As the thermal energy dissipated, subsidence and sedimentation continued into the late Jurassic and early Cretaceous when a further period of uplift and erosion occurred, marked by the Late Cimmerian unconformity. Regional subsidence during the Cretaceous resulted in gradual submergence of most of Britain. Compression and basin inversion at the end of the Cretaceous Period brought this episode of basin development to a close.
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	'''Igneous rocks of north-west Britain''' are associated with contemporary rifting and the development of the North Atlantic. Only the outer reaches of the Palaeogene dyke swarm are found in England and Wales ('''Figure P785826'''), but altered volcanic ash within the sediments of the London and Hampshire basins also reflects distant volcanic activity. Wolf Rock intrusion south-west of Land’s End shows an earlier phase of igneous activity that is better developed offshore on the continental shelf.		'''Igneous rocks of north-west Britain''' are associated with contemporary rifting and the development of the North Atlantic. Only the outer reaches of the Palaeogene dyke swarm are found in England and Wales ('''Figure P785826'''), but altered volcanic ash within the sediments of the London and Hampshire basins also reflects distant volcanic activity. Wolf Rock intrusion south-west of Land’s End shows an earlier phase of igneous activity that is better developed offshore on the continental shelf.

	~~<center>~~		[[Image:P785829.jpg\|thumb\|center\|600px\|Schematic cross-section of the Wessex Basin. [http://bgsintranet/asset-bank/action/viewFullSizedImage?id=379973&size=1000 P785829.]]]
	{\| ~~class="wikitable" width="100pt" style="margin-left:0px; margin-right:40px; margin-bottom:10px; float:~~center~~; text-align:left;"~~
	~~\| <img src="http://bgsintranet/asset-bank/action/directLinkImage?assetId=379973&width=503&height=121">~~
	\|-
	\| Schematic cross-section of the Wessex Basin. [http://bgsintranet/asset-bank/action/viewFullSizedImage?id=379973&size=1000 P785829.]
	\|}
	~~</center>~~

	'''The major processes that have influenced the rock record''' in the past—continental rifting, thermal uplift and subsidence, compression, climate change, sea-level change and oceanic circulation—have all affected the Cenozoic rocks and serve to illustrate how narrow our picture of the earlier periods really is, and how difficult it is to separate the various effects of these processes.		'''The major processes that have influenced the rock record''' in the past—continental rifting, thermal uplift and subsidence, compression, climate change, sea-level change and oceanic circulation—have all affected the Cenozoic rocks and serve to illustrate how narrow our picture of the earlier periods really is, and how difficult it is to separate the various effects of these processes.

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

2014-05-16T07:36:08Z

65 million years ago to the present day

← Older revision		Revision as of 08:36, 16 May 2014
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	==65 million years ago to the present day==		==65 million years ago to the present day==

	~~{\| class="wikitable" width="100pt" style="margin-left~~:~~40px; margin-right:0px; margin-bottom:10px; float:right; text-align:left;"~~		[[Image:P785840.jpg\|thumb\|200px\|[http://bgsintranet/asset-bank/action/viewFullSizedImage?id=379984&size=1000 P785840.]]]
	\| ~~<img src="http://bgsintranet/asset-bank/action/directLinkImage?assetId=379992&width=200&height=200">~~
	\|-
	\| [http://bgsintranet/asset-bank/action/viewFullSizedImage?id=379984&size=1000 P785840.]
	\|}

	'''The Cenozoic Era is named from the Greek meaning ‘new life’''', and is the time when modern life forms as we know them began to flourish—mammals, grass, the flowering plants and the insects that pollinate them. At the start of this era many Mesozoic forms became extinct, not only the dinosaurs but also ammonites, belemnites, many bivalves and chalk-forming nanoplankton.		'''The Cenozoic Era is named from the Greek meaning ‘new life’''', and is the time when modern life forms as we know them began to flourish—mammals, grass, the flowering plants and the insects that pollinate them. At the start of this era many Mesozoic forms became extinct, not only the dinosaurs but also ammonites, belemnites, many bivalves and chalk-forming nanoplankton.
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	'''At the beginning of the Cenozoic the British Isles''' lay at a latitude of 43º to 47ºN, and since then has moved north to its present position ('''Figure 4g'''). The climate has cooled progressively since the late Cretaceous, and may have been somewhat arid at times, but in the early part of the Palaeogene it was warm, supporting a lush vegetation.		'''At the beginning of the Cenozoic the British Isles''' lay at a latitude of 43º to 47ºN, and since then has moved north to its present position ('''Figure 4g'''). The climate has cooled progressively since the late Cretaceous, and may have been somewhat arid at times, but in the early part of the Palaeogene it was warm, supporting a lush vegetation.

	~~{\| class="wikitable" width="100pt" style="margin-left~~:~~0px; margin-right:40px; margin-bottom:10px; float:left; text-align:left;"~~		[[Image:P785826.jpg\|thumb\|200px\|Early Palaeogene palaeogeographical sketch map. [http://bgsintranet/asset-bank/action/viewFullSizedImage?id=379970&size=1000 P785826.]]]
	\| ~~<img src="http://bgsintranet/asset-bank/action/directLinkImage?assetId=379970&width=199&height=136">~~
	\|-
	\| Early Palaeogene palaeogeographical sketch map. [http://bgsintranet/asset-bank/action/viewFullSizedImage?id=379970&size=1000 P785826.]
	\|}

	'''Most of the British Isles has been land throughout the Cenozoic'''. Volcanic and intrusive igneous rocks are an important feature of the geology of Northern Ireland and western Scotland where they are part of the North Atlantic igneous province. This major episode of igneous activity is represented only sparsely in England and Wales by the outer reaches of a dyke swarm that includes the Cleveland Dyke (intruding Jurassic strata in North Yorkshire), tholeiitic dolerite (intruding the Mercia Mudstone north of Shrewsbury), dykes on Anglesey and Lleyn and offshore (including the Fleetwood Dyke), and granite on Lundy Island in the Bristol Channel ('''Figure P785826'''). The Palaeogene suite of western Scotland and Northern Ireland is dated at 62 to 55Ma. Thus, it largely predates the Cenozoic sediments that are found in the south of England, but numerous ash beds recorded within the sediments show that volcanic activity continued in the North Atlantic province.		'''Most of the British Isles has been land throughout the Cenozoic'''. Volcanic and intrusive igneous rocks are an important feature of the geology of Northern Ireland and western Scotland where they are part of the North Atlantic igneous province. This major episode of igneous activity is represented only sparsely in England and Wales by the outer reaches of a dyke swarm that includes the Cleveland Dyke (intruding Jurassic strata in North Yorkshire), tholeiitic dolerite (intruding the Mercia Mudstone north of Shrewsbury), dykes on Anglesey and Lleyn and offshore (including the Fleetwood Dyke), and granite on Lundy Island in the Bristol Channel ('''Figure P785826'''). The Palaeogene suite of western Scotland and Northern Ireland is dated at 62 to 55Ma. Thus, it largely predates the Cenozoic sediments that are found in the south of England, but numerous ash beds recorded within the sediments show that volcanic activity continued in the North Atlantic province.
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	'''The Cenozoic sediments are preserved in two major basins''', the London and Hampshire basins. Other, smaller outcrops occur in Devon along the line of the Sticklepath–Lustleigh Fault at Bovey Tracey and Petrockstowe (G5) with smaller outcrops farther west in Cornwall (N1). At Mochras on the west coast of Wales, there is a thick succession concealed beneath younger glacial deposits. Elsewhere there are residual deposits of Cenozoic sediments, such as ‘clay-with-flints’, preserved in fissures and hollows in the underlying strata, and particularly in irregular karstic hollows developed on the top of the Chalk Group.		'''The Cenozoic sediments are preserved in two major basins''', the London and Hampshire basins. Other, smaller outcrops occur in Devon along the line of the Sticklepath–Lustleigh Fault at Bovey Tracey and Petrockstowe (G5) with smaller outcrops farther west in Cornwall (N1). At Mochras on the west coast of Wales, there is a thick succession concealed beneath younger glacial deposits. Elsewhere there are residual deposits of Cenozoic sediments, such as ‘clay-with-flints’, preserved in fissures and hollows in the underlying strata, and particularly in irregular karstic hollows developed on the top of the Chalk Group.

	~~{\| class="wikitable" width="100pt" style="margin-left~~:~~40px; margin-right:0px; margin-bottom:10px; float:right; text-align:left;"~~		[[Image:P785828.jpg\|thumb\|200px\|Deposition of the Lambeth Group in the London Basin. [http://bgsintranet/asset-bank/action/viewFullSizedImage?id=379972&size=1000 P785828.]]]
	\| ~~<img src="http://bgsintranet/asset-bank/action/directLinkImage?assetId=379972&width=308&height=166">~~
	\|-
	\| Deposition of the Lambeth Group in the London Basin. [http://bgsintranet/asset-bank/action/viewFullSizedImage?id=379972&size=1000 P785828.]
	\|}

	'''The London and Hampshire basins are asymmetrical synclines''', each with a gently dipping northern limb and steeply dipping southern limb. They are separated by the Pewsey and Weald anticlines. The sediments in these basins were formerly part of a large Cenozoic sedimentary basin covering southern England ('''Figure P785826'''), and during times of higher sea level there was intermittent connection with deeper grabens developing in the North Sea to the east and the Atlantic Ocean to the west. During intervals of low sea level, the basin was an area of swamp traversed by braided rivers, and thus the Palaeogene and Neogene strata of southern England record alternating transgressions and regressions ('''Figure P785828''').		'''The London and Hampshire basins are asymmetrical synclines''', each with a gently dipping northern limb and steeply dipping southern limb. They are separated by the Pewsey and Weald anticlines. The sediments in these basins were formerly part of a large Cenozoic sedimentary basin covering southern England ('''Figure P785826'''), and during times of higher sea level there was intermittent connection with deeper grabens developing in the North Sea to the east and the Atlantic Ocean to the west. During intervals of low sea level, the basin was an area of swamp traversed by braided rivers, and thus the Palaeogene and Neogene strata of southern England record alternating transgressions and regressions ('''Figure P785828''').
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	'''The succession, from base to top''', in the London Basin comprises the Thanet Sand Formation (G1), Lambeth Group (G2; Paleocene–Eocene), Harwich Formation (G3), Thames Group (G3) and the Bagshot Formation (G4). In the Hampshire Basin, the Thanet Sand Formation is absent and the succession consists of the Lambeth (Eocene), Thames, Bracklesham and Barton groups (G4; Eocene), and the Solent Group (G5; mainly Oligocene). The lithologies within the basins are generally similar but differ in detail; these are the sediments to delight children of all ages for there is mud, sand and pebbles in a range of vivid and unlikely colours, and fossils.		'''The succession, from base to top''', in the London Basin comprises the Thanet Sand Formation (G1), Lambeth Group (G2; Paleocene–Eocene), Harwich Formation (G3), Thames Group (G3) and the Bagshot Formation (G4). In the Hampshire Basin, the Thanet Sand Formation is absent and the succession consists of the Lambeth (Eocene), Thames, Bracklesham and Barton groups (G4; Eocene), and the Solent Group (G5; mainly Oligocene). The lithologies within the basins are generally similar but differ in detail; these are the sediments to delight children of all ages for there is mud, sand and pebbles in a range of vivid and unlikely colours, and fossils.

	{\| ~~class="wikitable" width="100pt" style="margin-~~left~~:0px; margin-right:40px; margin-bottom:10px; float:left; text-align:left;"~~		[[Image:P211781.jpg\|thumb\|left\|200px\|Pebble beds interfingering with mustard-coloured sand in the Upnor Formation, Lambeth Group, Essex. [http://bgsintranet/asset-bank/action/viewFullSizedImage?id=20333&size=1000 P211781.]]]
	~~\| <img src="http://bgsintranet/asset-bank/action/directLinkImage?assetId=20333&width=200&height=150">~~		[[Image:P649780.jpg\|thumb\|left\|200px\|Alum Bay, Isle of Wight. [http://bgsintranet/asset-bank/action/viewFullSizedImage?id=47487&size=1000 P649780.]]]
	\|-
	\| Pebble beds interfingering with mustard-coloured sand in the Upnor Formation, Lambeth Group, Essex. [http://bgsintranet/asset-bank/action/viewFullSizedImage?id=20333&size=1000 P211781.]
	\|-
	\| ~~<img src="http://bgsintranet/asset-bank/action/directLinkImage?assetId=47487&width=200&height=150">~~
	\|-
	\| Alum Bay, Isle of Wight. [http://bgsintranet/asset-bank/action/viewFullSizedImage?id=47487&size=1000 P649780.]
	\|}

	'''The Thanet Sand Formation''' (up to 30m thick) is a pale yellowish grey colour where it is weathered near the surface, and has been burrowed extensively by marine creatures so that few bedding structures remain. At the base is the Bullhead Bed, flint pebbles and cobbles in a matrix of clay with sand grains that are likely to have had their source in the Moine and Dalradian rocks of the Scottish Highlands. The Lambeth Group (G2) is up to 20m thick and has three formations. The Upnor Formation contains an abundance of well-rounded flint pebbles, shoreface deposits, and tidal sands ('''Plate P211781'''). Most of the mineral grains have a Scottish origin, but some indicate a different provenance, perhaps Armorica, Ardennes or the granites of south-west England. The Woolwich Formation, in the east, is a marine facies and shows a strong cyclicity in the pattern of sand, clay, pebble and shell beds. The shell beds have provided an abundance of fossils for the local museums over the years. The Reading Formation, in the west, was deposited on an alluvial plain where soil developed when conditions allowed. The sediments are particularly well exposed on the west coast of the Isle of Wight where they weather to a range of colours—yellow, brown, orange, red and purple—depending on the iron minerals that are present in the silty or sandy clay.		'''The Thanet Sand Formation''' (up to 30m thick) is a pale yellowish grey colour where it is weathered near the surface, and has been burrowed extensively by marine creatures so that few bedding structures remain. At the base is the Bullhead Bed, flint pebbles and cobbles in a matrix of clay with sand grains that are likely to have had their source in the Moine and Dalradian rocks of the Scottish Highlands. The Lambeth Group (G2) is up to 20m thick and has three formations. The Upnor Formation contains an abundance of well-rounded flint pebbles, shoreface deposits, and tidal sands ('''Plate P211781'''). Most of the mineral grains have a Scottish origin, but some indicate a different provenance, perhaps Armorica, Ardennes or the granites of south-west England. The Woolwich Formation, in the east, is a marine facies and shows a strong cyclicity in the pattern of sand, clay, pebble and shell beds. The shell beds have provided an abundance of fossils for the local museums over the years. The Reading Formation, in the west, was deposited on an alluvial plain where soil developed when conditions allowed. The sediments are particularly well exposed on the west coast of the Isle of Wight where they weather to a range of colours—yellow, brown, orange, red and purple—depending on the iron minerals that are present in the silty or sandy clay.

← Older revision		Revision as of 11:09, 20 May 2014
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	==65 million years ago to the present day==		==65 million years ago to the present day==

	[[Image:P785840.jpg\|thumb\|200px\|~~[http://bgsintranet/asset-bank/action/viewFullSizedImage?id=379984&size=1000~~ P785840.]]]		[[Image:P785840.jpg\|thumb\|200px\|P785840.]]

	'''The Cenozoic Era is named from the Greek meaning ‘new life’''', and is the time when modern life forms as we know them began to flourish—mammals, grass, the flowering plants and the insects that pollinate them. At the start of this era many Mesozoic forms became extinct, not only the dinosaurs but also ammonites, belemnites, many bivalves and chalk-forming nanoplankton.		'''The Cenozoic Era is named from the Greek meaning ‘new life’''', and is the time when modern life forms as we know them began to flourish—mammals, grass, the flowering plants and the insects that pollinate them. At the start of this era many Mesozoic forms became extinct, not only the dinosaurs but also ammonites, belemnites, many bivalves and chalk-forming nanoplankton.
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	'''At the beginning of the Cenozoic the British Isles''' lay at a latitude of 43º to 47ºN, and since then has moved north to its present position ('''Figure 4g'''). The climate has cooled progressively since the late Cretaceous, and may have been somewhat arid at times, but in the early part of the Palaeogene it was warm, supporting a lush vegetation.		'''At the beginning of the Cenozoic the British Isles''' lay at a latitude of 43º to 47ºN, and since then has moved north to its present position ('''Figure 4g'''). The climate has cooled progressively since the late Cretaceous, and may have been somewhat arid at times, but in the early part of the Palaeogene it was warm, supporting a lush vegetation.

	[[Image:P785826.jpg\|thumb\|200px\|Early Palaeogene palaeogeographical sketch map. ~~[http://bgsintranet/asset-bank/action/viewFullSizedImage?id=379970&size=1000~~ P785826.]]]		[[Image:P785826.jpg\|thumb\|200px\|Early Palaeogene palaeogeographical sketch map. P785826.]]

	'''Most of the British Isles has been land throughout the Cenozoic'''. Volcanic and intrusive igneous rocks are an important feature of the geology of Northern Ireland and western Scotland where they are part of the North Atlantic igneous province. This major episode of igneous activity is represented only sparsely in England and Wales by the outer reaches of a dyke swarm that includes the Cleveland Dyke (intruding Jurassic strata in North Yorkshire), tholeiitic dolerite (intruding the Mercia Mudstone north of Shrewsbury), dykes on Anglesey and Lleyn and offshore (including the Fleetwood Dyke), and granite on Lundy Island in the Bristol Channel ('''Figure P785826'''). The Palaeogene suite of western Scotland and Northern Ireland is dated at 62 to 55Ma. Thus, it largely predates the Cenozoic sediments that are found in the south of England, but numerous ash beds recorded within the sediments show that volcanic activity continued in the North Atlantic province.		'''Most of the British Isles has been land throughout the Cenozoic'''. Volcanic and intrusive igneous rocks are an important feature of the geology of Northern Ireland and western Scotland where they are part of the North Atlantic igneous province. This major episode of igneous activity is represented only sparsely in England and Wales by the outer reaches of a dyke swarm that includes the Cleveland Dyke (intruding Jurassic strata in North Yorkshire), tholeiitic dolerite (intruding the Mercia Mudstone north of Shrewsbury), dykes on Anglesey and Lleyn and offshore (including the Fleetwood Dyke), and granite on Lundy Island in the Bristol Channel ('''Figure P785826'''). The Palaeogene suite of western Scotland and Northern Ireland is dated at 62 to 55Ma. Thus, it largely predates the Cenozoic sediments that are found in the south of England, but numerous ash beds recorded within the sediments show that volcanic activity continued in the North Atlantic province.
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	'''The Cenozoic sediments are preserved in two major basins''', the London and Hampshire basins. Other, smaller outcrops occur in Devon along the line of the Sticklepath–Lustleigh Fault at Bovey Tracey and Petrockstowe (G5) with smaller outcrops farther west in Cornwall (N1). At Mochras on the west coast of Wales, there is a thick succession concealed beneath younger glacial deposits. Elsewhere there are residual deposits of Cenozoic sediments, such as ‘clay-with-flints’, preserved in fissures and hollows in the underlying strata, and particularly in irregular karstic hollows developed on the top of the Chalk Group.		'''The Cenozoic sediments are preserved in two major basins''', the London and Hampshire basins. Other, smaller outcrops occur in Devon along the line of the Sticklepath–Lustleigh Fault at Bovey Tracey and Petrockstowe (G5) with smaller outcrops farther west in Cornwall (N1). At Mochras on the west coast of Wales, there is a thick succession concealed beneath younger glacial deposits. Elsewhere there are residual deposits of Cenozoic sediments, such as ‘clay-with-flints’, preserved in fissures and hollows in the underlying strata, and particularly in irregular karstic hollows developed on the top of the Chalk Group.

	[[Image:P785828.jpg\|thumb\|200px\|Deposition of the Lambeth Group in the London Basin. ~~[http://bgsintranet/asset-bank/action/viewFullSizedImage?id=379972&size=1000~~ P785828.]]]		[[Image:P785828.jpg\|thumb\|200px\|Deposition of the Lambeth Group in the London Basin. P785828.]]

	'''The London and Hampshire basins are asymmetrical synclines''', each with a gently dipping northern limb and steeply dipping southern limb. They are separated by the Pewsey and Weald anticlines. The sediments in these basins were formerly part of a large Cenozoic sedimentary basin covering southern England ('''Figure P785826'''), and during times of higher sea level there was intermittent connection with deeper grabens developing in the North Sea to the east and the Atlantic Ocean to the west. During intervals of low sea level, the basin was an area of swamp traversed by braided rivers, and thus the Palaeogene and Neogene strata of southern England record alternating transgressions and regressions ('''Figure P785828''').		'''The London and Hampshire basins are asymmetrical synclines''', each with a gently dipping northern limb and steeply dipping southern limb. They are separated by the Pewsey and Weald anticlines. The sediments in these basins were formerly part of a large Cenozoic sedimentary basin covering southern England ('''Figure P785826'''), and during times of higher sea level there was intermittent connection with deeper grabens developing in the North Sea to the east and the Atlantic Ocean to the west. During intervals of low sea level, the basin was an area of swamp traversed by braided rivers, and thus the Palaeogene and Neogene strata of southern England record alternating transgressions and regressions ('''Figure P785828''').
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	'''The succession, from base to top''', in the London Basin comprises the Thanet Sand Formation (G1), Lambeth Group (G2; Paleocene–Eocene), Harwich Formation (G3), Thames Group (G3) and the Bagshot Formation (G4). In the Hampshire Basin, the Thanet Sand Formation is absent and the succession consists of the Lambeth (Eocene), Thames, Bracklesham and Barton groups (G4; Eocene), and the Solent Group (G5; mainly Oligocene). The lithologies within the basins are generally similar but differ in detail; these are the sediments to delight children of all ages for there is mud, sand and pebbles in a range of vivid and unlikely colours, and fossils.		'''The succession, from base to top''', in the London Basin comprises the Thanet Sand Formation (G1), Lambeth Group (G2; Paleocene–Eocene), Harwich Formation (G3), Thames Group (G3) and the Bagshot Formation (G4). In the Hampshire Basin, the Thanet Sand Formation is absent and the succession consists of the Lambeth (Eocene), Thames, Bracklesham and Barton groups (G4; Eocene), and the Solent Group (G5; mainly Oligocene). The lithologies within the basins are generally similar but differ in detail; these are the sediments to delight children of all ages for there is mud, sand and pebbles in a range of vivid and unlikely colours, and fossils.

	[[Image:P211781.jpg\|thumb\|left\|200px\|Pebble beds interfingering with mustard-coloured sand in the Upnor Formation, Lambeth Group, Essex. [http://~~bgsintranet~~/asset-bank/action/~~viewFullSizedImage~~?id=20333&~~size~~=~~1000~~ P211781.]]]		[[Image:P211781.jpg\|thumb\|left\|200px\|Pebble beds interfingering with mustard-coloured sand in the Upnor Formation, Lambeth Group, Essex. [http://geoscenic.bgs.ac.uk/asset-bank/action/viewAsset?id=20333&index=0&total=1&view=viewSearchItem P211781.]]]
	[[Image:P649780.jpg\|thumb\|left\|200px\|Alum Bay, Isle of Wight. ~~[http://bgsintranet/asset-bank/action/viewFullSizedImage?id=47487&size=1000~~ P649780.]]]		[[Image:P649780.jpg\|thumb\|left\|200px\|Alum Bay, Isle of Wight. P649780.]]

	'''The Thanet Sand Formation''' (up to 30m thick) is a pale yellowish grey colour where it is weathered near the surface, and has been burrowed extensively by marine creatures so that few bedding structures remain. At the base is the Bullhead Bed, flint pebbles and cobbles in a matrix of clay with sand grains that are likely to have had their source in the Moine and Dalradian rocks of the Scottish Highlands. The Lambeth Group (G2) is up to 20m thick and has three formations. The Upnor Formation contains an abundance of well-rounded flint pebbles, shoreface deposits, and tidal sands ('''Plate P211781'''). Most of the mineral grains have a Scottish origin, but some indicate a different provenance, perhaps Armorica, Ardennes or the granites of south-west England. The Woolwich Formation, in the east, is a marine facies and shows a strong cyclicity in the pattern of sand, clay, pebble and shell beds. The shell beds have provided an abundance of fossils for the local museums over the years. The Reading Formation, in the west, was deposited on an alluvial plain where soil developed when conditions allowed. The sediments are particularly well exposed on the west coast of the Isle of Wight where they weather to a range of colours—yellow, brown, orange, red and purple—depending on the iron minerals that are present in the silty or sandy clay.		'''The Thanet Sand Formation''' (up to 30m thick) is a pale yellowish grey colour where it is weathered near the surface, and has been burrowed extensively by marine creatures so that few bedding structures remain. At the base is the Bullhead Bed, flint pebbles and cobbles in a matrix of clay with sand grains that are likely to have had their source in the Moine and Dalradian rocks of the Scottish Highlands. The Lambeth Group (G2) is up to 20m thick and has three formations. The Upnor Formation contains an abundance of well-rounded flint pebbles, shoreface deposits, and tidal sands ('''Plate P211781'''). Most of the mineral grains have a Scottish origin, but some indicate a different provenance, perhaps Armorica, Ardennes or the granites of south-west England. The Woolwich Formation, in the east, is a marine facies and shows a strong cyclicity in the pattern of sand, clay, pebble and shell beds. The shell beds have provided an abundance of fossils for the local museums over the years. The Reading Formation, in the west, was deposited on an alluvial plain where soil developed when conditions allowed. The sediments are particularly well exposed on the west coast of the Isle of Wight where they weather to a range of colours—yellow, brown, orange, red and purple—depending on the iron minerals that are present in the silty or sandy clay.
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	= Cimmerian–Alpine cycle =		= Cimmerian–Alpine cycle =

	[[Image:P005798.jpg\|thumb\|200px\|Alpine folds in Jurassic and Lower Cretaceous strata, Lulworth Cove. [http://~~bgsintranet~~/asset-bank/action/~~viewFullSizedImage~~?id=5054&~~size~~=~~1000~~ P005798.]]]		[[Image:P005798.jpg\|thumb\|200px\|Alpine folds in Jurassic and Lower Cretaceous strata, Lulworth Cove. [http://geoscenic.bgs.ac.uk/asset-bank/action/viewAsset?id=5054&index=0&total=1&view=viewSearchItem P005798.]]]

	'''The break up of the continent of Pangaea''' and the opening of the North Atlantic has dominated the tectonic history of the UK since Permian times. Extensional faults, many of which were reactivated older structures, controlled the development of the Mesozoic sedimentary basins of Cleveland, Cheshire, Worcester and Wessex. Sediments accumulated in these intracontinental sags during the Triassic and Jurassic, while considerably thicker sequences collected in the deeper offshore rifts of the North Sea and Irish Sea. In mid Jurassic times, thermal doming in the North Sea resulted in uplift and erosion over much of northern and eastern Britain, producing the Mid Cimmerian unconformity. As the thermal energy dissipated, subsidence and sedimentation continued into the late Jurassic and early Cretaceous when a further period of uplift and erosion occurred, marked by the Late Cimmerian unconformity. Regional subsidence during the Cretaceous resulted in gradual submergence of most of Britain. Compression and basin inversion at the end of the Cretaceous Period brought this episode of basin development to a close.		'''The break up of the continent of Pangaea''' and the opening of the North Atlantic has dominated the tectonic history of the UK since Permian times. Extensional faults, many of which were reactivated older structures, controlled the development of the Mesozoic sedimentary basins of Cleveland, Cheshire, Worcester and Wessex. Sediments accumulated in these intracontinental sags during the Triassic and Jurassic, while considerably thicker sequences collected in the deeper offshore rifts of the North Sea and Irish Sea. In mid Jurassic times, thermal doming in the North Sea resulted in uplift and erosion over much of northern and eastern Britain, producing the Mid Cimmerian unconformity. As the thermal energy dissipated, subsidence and sedimentation continued into the late Jurassic and early Cretaceous when a further period of uplift and erosion occurred, marked by the Late Cimmerian unconformity. Regional subsidence during the Cretaceous resulted in gradual submergence of most of Britain. Compression and basin inversion at the end of the Cretaceous Period brought this episode of basin development to a close.
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	'''Igneous rocks of north-west Britain''' are associated with contemporary rifting and the development of the North Atlantic. Only the outer reaches of the Palaeogene dyke swarm are found in England and Wales ('''Figure P785826'''), but altered volcanic ash within the sediments of the London and Hampshire basins also reflects distant volcanic activity. Wolf Rock intrusion south-west of Land’s End shows an earlier phase of igneous activity that is better developed offshore on the continental shelf.		'''Igneous rocks of north-west Britain''' are associated with contemporary rifting and the development of the North Atlantic. Only the outer reaches of the Palaeogene dyke swarm are found in England and Wales ('''Figure P785826'''), but altered volcanic ash within the sediments of the London and Hampshire basins also reflects distant volcanic activity. Wolf Rock intrusion south-west of Land’s End shows an earlier phase of igneous activity that is better developed offshore on the continental shelf.

	[[Image:P785829.jpg\|thumb\|center\|600px\|Schematic cross-section of the Wessex Basin. ~~[http://bgsintranet/asset-bank/action/viewFullSizedImage?id=379973&size=1000~~ P785829.]]]		[[Image:P785829.jpg\|thumb\|center\|600px\|Schematic cross-section of the Wessex Basin. P785829.]]

	'''The major processes that have influenced the rock record''' in the past—continental rifting, thermal uplift and subsidence, compression, climate change, sea-level change and oceanic circulation—have all affected the Cenozoic rocks and serve to illustrate how narrow our picture of the earlier periods really is, and how difficult it is to separate the various effects of these processes.		'''The major processes that have influenced the rock record''' in the past—continental rifting, thermal uplift and subsidence, compression, climate change, sea-level change and oceanic circulation—have all affected the Cenozoic rocks and serve to illustrate how narrow our picture of the earlier periods really is, and how difficult it is to separate the various effects of these processes.