Category:Southern Province Chalk nomenclature - Revision history

Jeth1 at 17:07, 5 February 2015

2015-02-05T17:07:40Z

Jeth1 at 16:27, 5 February 2015

2015-02-05T16:27:48Z

Dbk: Protected "Category:Southern Province Chalk nomenclature" ([Edit=Allow only administrators] (indefinite) [Move=Allow only administrators] (indefinite)) [cascading]

2014-06-11T12:00:22Z

Protected "Category:Southern Province Chalk nomenclature" ([Edit=Allow only administrators] (indefinite) [Move=Allow only administrators] (indefinite)) [cascading]

← Older revision	Revision as of 13:00, 11 June 2014
(No difference)

Testuser at 11:51, 11 June 2014

2014-06-11T11:51:47Z

← Older revision		Revision as of 12:51, 11 June 2014
Line 1:		Line 1:
	[[Image:P895004.jpg\|thumb\|400px\| The Chalk Group provinces of England. P895004.]]		[[Image:P895004.jpg\|thumb\|400px\| The Chalk Group provinces of England. P895004.]]
	~~test~~ The '''Chalk Group''' has been in use informally for a number of years. Its first formal use was by Rhys (1974) [Fig.11/1] to cover the Chalk in the North Sea and by Wood and Smith (1978) [Fig.2/7 and Fig.6/5] to cover the whole of the Chalk succession in the ‘Northern Province’ but this also included the Red Chalk (now excluded from the definition as the Hunstanton Formation). Rawson et al. (1978) utilised the term Chalk Formation to cover the whole of the Chalk (Cenomanian to Maastrichtian). Robinson (1986) [Fig.2/9, Fig.3/2 and Fig.5a/8] in the North Downs and Mortimore (1986) [Fig.2/8, Fig.3/3 and Fig.5a/9], by implication, in the South Downs, used the term Chalk Group to cover the succession from the basal unconformity to the youngest known chalk beneath the Palaeogene unconformity in those areas. Bristow et al. (1997) [Fig.2/10, Fig.3/5 and Fig.5a/10] used Chalk Group to include Lower, Middle and Upper Chalk Formations. Rawson et al. (2001) [Fig.2/11, Fig3/6 and Fig.5a/11] formalised the terminology, agreed at the November 1999 meeting, using Chalk Group to cover a lower Grey Chalk Subgroup and a higher White Chalk Subgroup. These divided further into formations.		The '''Chalk Group''' has been in use informally for a number of years. Its first formal use was by Rhys (1974) [Fig.11/1] to cover the Chalk in the North Sea and by Wood and Smith (1978) [Fig.2/7 and Fig.6/5] to cover the whole of the Chalk succession in the ‘Northern Province’ but this also included the Red Chalk (now excluded from the definition as the Hunstanton Formation). Rawson et al. (1978) utilised the term Chalk Formation to cover the whole of the Chalk (Cenomanian to Maastrichtian). Robinson (1986) [Fig.2/9, Fig.3/2 and Fig.5a/8] in the North Downs and Mortimore (1986) [Fig.2/8, Fig.3/3 and Fig.5a/9], by implication, in the South Downs, used the term Chalk Group to cover the succession from the basal unconformity to the youngest known chalk beneath the Palaeogene unconformity in those areas. Bristow et al. (1997) [Fig.2/10, Fig.3/5 and Fig.5a/10] used Chalk Group to include Lower, Middle and Upper Chalk Formations. Rawson et al. (2001) [Fig.2/11, Fig3/6 and Fig.5a/11] formalised the terminology, agreed at the November 1999 meeting, using Chalk Group to cover a lower Grey Chalk Subgroup and a higher White Chalk Subgroup. These divided further into formations.

	'''It should be emphasised that the use of the Southern Province terms throughout the Transitional Province must be tested as these areas come up for revision'''. It is known with some certainty that Southern Province formations can be readily applied throughout the Chilterns and northwards into Cambridgeshire within the scarp facing west over the River Ouse/Wash Basin. The continuity of these formations beneath the thick Quaternary superficial deposits to the east and north needs to be tested. Geophysical borehole records and the interpretations of Murray (1986) show that there is a continuity of widespread identifiable marls seams in Essex, southern Suffolk and further north which confirm a framework of events that are correlated to marker beds in the Southern Province. Of course these geophysical results show inflections interpreted as marls and do not give comprehensive information on the nature of the intervening chalk lithologies. These lithologies need to be characterised to be certain of the use of Southern Province terms but it is envisaged that the formational framework may still be applied widely beneath East Anglia; and that variations in chalk successions may be better attributed to locally named units. It is suggested that such units as are identified be designated as members principally because their ‘mappability’ beneath the Quaternary cover may merely reflect an inappropriate borehole spread unrelated to their true extent.		'''It should be emphasised that the use of the Southern Province terms throughout the Transitional Province must be tested as these areas come up for revision'''. It is known with some certainty that Southern Province formations can be readily applied throughout the Chilterns and northwards into Cambridgeshire within the scarp facing west over the River Ouse/Wash Basin. The continuity of these formations beneath the thick Quaternary superficial deposits to the east and north needs to be tested. Geophysical borehole records and the interpretations of Murray (1986) show that there is a continuity of widespread identifiable marls seams in Essex, southern Suffolk and further north which confirm a framework of events that are correlated to marker beds in the Southern Province. Of course these geophysical results show inflections interpreted as marls and do not give comprehensive information on the nature of the intervening chalk lithologies. These lithologies need to be characterised to be certain of the use of Southern Province terms but it is envisaged that the formational framework may still be applied widely beneath East Anglia; and that variations in chalk successions may be better attributed to locally named units. It is suggested that such units as are identified be designated as members principally because their ‘mappability’ beneath the Quaternary cover may merely reflect an inappropriate borehole spread unrelated to their true extent.

Testuser at 11:51, 11 June 2014

2014-06-11T11:51:33Z

← Older revision		Revision as of 12:51, 11 June 2014
Line 1:		Line 1:
	[[Image:P895004.jpg\|thumb\|400px\| The Chalk Group provinces of England. P895004.]]		[[Image:P895004.jpg\|thumb\|400px\| The Chalk Group provinces of England. P895004.]]
	The '''Chalk Group''' has been in use informally for a number of years. Its first formal use was by Rhys (1974) [Fig.11/1] to cover the Chalk in the North Sea and by Wood and Smith (1978) [Fig.2/7 and Fig.6/5] to cover the whole of the Chalk succession in the ‘Northern Province’ but this also included the Red Chalk (now excluded from the definition as the Hunstanton Formation). Rawson et al. (1978) utilised the term Chalk Formation to cover the whole of the Chalk (Cenomanian to Maastrichtian). Robinson (1986) [Fig.2/9, Fig.3/2 and Fig.5a/8] in the North Downs and Mortimore (1986) [Fig.2/8, Fig.3/3 and Fig.5a/9], by implication, in the South Downs, used the term Chalk Group to cover the succession from the basal unconformity to the youngest known chalk beneath the Palaeogene unconformity in those areas. Bristow et al. (1997) [Fig.2/10, Fig.3/5 and Fig.5a/10] used Chalk Group to include Lower, Middle and Upper Chalk Formations. Rawson et al. (2001) [Fig.2/11, Fig3/6 and Fig.5a/11] formalised the terminology, agreed at the November 1999 meeting, using Chalk Group to cover a lower Grey Chalk Subgroup and a higher White Chalk Subgroup. These divided further into formations.		test The '''Chalk Group''' has been in use informally for a number of years. Its first formal use was by Rhys (1974) [Fig.11/1] to cover the Chalk in the North Sea and by Wood and Smith (1978) [Fig.2/7 and Fig.6/5] to cover the whole of the Chalk succession in the ‘Northern Province’ but this also included the Red Chalk (now excluded from the definition as the Hunstanton Formation). Rawson et al. (1978) utilised the term Chalk Formation to cover the whole of the Chalk (Cenomanian to Maastrichtian). Robinson (1986) [Fig.2/9, Fig.3/2 and Fig.5a/8] in the North Downs and Mortimore (1986) [Fig.2/8, Fig.3/3 and Fig.5a/9], by implication, in the South Downs, used the term Chalk Group to cover the succession from the basal unconformity to the youngest known chalk beneath the Palaeogene unconformity in those areas. Bristow et al. (1997) [Fig.2/10, Fig.3/5 and Fig.5a/10] used Chalk Group to include Lower, Middle and Upper Chalk Formations. Rawson et al. (2001) [Fig.2/11, Fig3/6 and Fig.5a/11] formalised the terminology, agreed at the November 1999 meeting, using Chalk Group to cover a lower Grey Chalk Subgroup and a higher White Chalk Subgroup. These divided further into formations.

	'''It should be emphasised that the use of the Southern Province terms throughout the Transitional Province must be tested as these areas come up for revision'''. It is known with some certainty that Southern Province formations can be readily applied throughout the Chilterns and northwards into Cambridgeshire within the scarp facing west over the River Ouse/Wash Basin. The continuity of these formations beneath the thick Quaternary superficial deposits to the east and north needs to be tested. Geophysical borehole records and the interpretations of Murray (1986) show that there is a continuity of widespread identifiable marls seams in Essex, southern Suffolk and further north which confirm a framework of events that are correlated to marker beds in the Southern Province. Of course these geophysical results show inflections interpreted as marls and do not give comprehensive information on the nature of the intervening chalk lithologies. These lithologies need to be characterised to be certain of the use of Southern Province terms but it is envisaged that the formational framework may still be applied widely beneath East Anglia; and that variations in chalk successions may be better attributed to locally named units. It is suggested that such units as are identified be designated as members principally because their ‘mappability’ beneath the Quaternary cover may merely reflect an inappropriate borehole spread unrelated to their true extent.		'''It should be emphasised that the use of the Southern Province terms throughout the Transitional Province must be tested as these areas come up for revision'''. It is known with some certainty that Southern Province formations can be readily applied throughout the Chilterns and northwards into Cambridgeshire within the scarp facing west over the River Ouse/Wash Basin. The continuity of these formations beneath the thick Quaternary superficial deposits to the east and north needs to be tested. Geophysical borehole records and the interpretations of Murray (1986) show that there is a continuity of widespread identifiable marls seams in Essex, southern Suffolk and further north which confirm a framework of events that are correlated to marker beds in the Southern Province. Of course these geophysical results show inflections interpreted as marls and do not give comprehensive information on the nature of the intervening chalk lithologies. These lithologies need to be characterised to be certain of the use of Southern Province terms but it is envisaged that the formational framework may still be applied widely beneath East Anglia; and that variations in chalk successions may be better attributed to locally named units. It is suggested that such units as are identified be designated as members principally because their ‘mappability’ beneath the Quaternary cover may merely reflect an inappropriate borehole spread unrelated to their true extent.

Dbk at 10:45, 11 June 2014

2014-06-11T10:45:15Z

← Older revision		Revision as of 11:45, 11 June 2014
Line 1:		Line 1:
	[[Image:P895004.jpg\|thumb\|400px\| The Chalk Group provinces of England. ~~[http://bgsintranet/asset-bank/action/viewFullSizedImage?id=482033&size=1000~~ P895004.]]]		[[Image:P895004.jpg\|thumb\|400px\| The Chalk Group provinces of England. P895004.]]
	The '''Chalk Group''' has been in use informally for a number of years. Its first formal use was by Rhys (1974) [Fig.11/1] to cover the Chalk in the North Sea and by Wood and Smith (1978) [Fig.2/7 and Fig.6/5] to cover the whole of the Chalk succession in the ‘Northern Province’ but this also included the Red Chalk (now excluded from the definition as the Hunstanton Formation). Rawson et al. (1978) utilised the term Chalk Formation to cover the whole of the Chalk (Cenomanian to Maastrichtian). Robinson (1986) [Fig.2/9, Fig.3/2 and Fig.5a/8] in the North Downs and Mortimore (1986) [Fig.2/8, Fig.3/3 and Fig.5a/9], by implication, in the South Downs, used the term Chalk Group to cover the succession from the basal unconformity to the youngest known chalk beneath the Palaeogene unconformity in those areas. Bristow et al. (1997) [Fig.2/10, Fig.3/5 and Fig.5a/10] used Chalk Group to include Lower, Middle and Upper Chalk Formations. Rawson et al. (2001) [Fig.2/11, Fig3/6 and Fig.5a/11] formalised the terminology, agreed at the November 1999 meeting, using Chalk Group to cover a lower Grey Chalk Subgroup and a higher White Chalk Subgroup. These divided further into formations.		The '''Chalk Group''' has been in use informally for a number of years. Its first formal use was by Rhys (1974) [Fig.11/1] to cover the Chalk in the North Sea and by Wood and Smith (1978) [Fig.2/7 and Fig.6/5] to cover the whole of the Chalk succession in the ‘Northern Province’ but this also included the Red Chalk (now excluded from the definition as the Hunstanton Formation). Rawson et al. (1978) utilised the term Chalk Formation to cover the whole of the Chalk (Cenomanian to Maastrichtian). Robinson (1986) [Fig.2/9, Fig.3/2 and Fig.5a/8] in the North Downs and Mortimore (1986) [Fig.2/8, Fig.3/3 and Fig.5a/9], by implication, in the South Downs, used the term Chalk Group to cover the succession from the basal unconformity to the youngest known chalk beneath the Palaeogene unconformity in those areas. Bristow et al. (1997) [Fig.2/10, Fig.3/5 and Fig.5a/10] used Chalk Group to include Lower, Middle and Upper Chalk Formations. Rawson et al. (2001) [Fig.2/11, Fig3/6 and Fig.5a/11] formalised the terminology, agreed at the November 1999 meeting, using Chalk Group to cover a lower Grey Chalk Subgroup and a higher White Chalk Subgroup. These divided further into formations.

Dbk at 10:44, 11 June 2014

2014-06-11T10:44:39Z

← Older revision		Revision as of 11:44, 11 June 2014
Line 1:		Line 1:
	[[Image:P895004.~~png~~\|thumb\|400px\| The Chalk Group provinces of England. [http://bgsintranet/asset-bank/action/viewFullSizedImage?id=482033&size=1000 P895004.]]]		[[Image:P895004.jpg\|thumb\|400px\| The Chalk Group provinces of England. [http://bgsintranet/asset-bank/action/viewFullSizedImage?id=482033&size=1000 P895004.]]]
	The '''Chalk Group''' has been in use informally for a number of years. Its first formal use was by Rhys (1974) [Fig.11/1] to cover the Chalk in the North Sea and by Wood and Smith (1978) [Fig.2/7 and Fig.6/5] to cover the whole of the Chalk succession in the ‘Northern Province’ but this also included the Red Chalk (now excluded from the definition as the Hunstanton Formation). Rawson et al. (1978) utilised the term Chalk Formation to cover the whole of the Chalk (Cenomanian to Maastrichtian). Robinson (1986) [Fig.2/9, Fig.3/2 and Fig.5a/8] in the North Downs and Mortimore (1986) [Fig.2/8, Fig.3/3 and Fig.5a/9], by implication, in the South Downs, used the term Chalk Group to cover the succession from the basal unconformity to the youngest known chalk beneath the Palaeogene unconformity in those areas. Bristow et al. (1997) [Fig.2/10, Fig.3/5 and Fig.5a/10] used Chalk Group to include Lower, Middle and Upper Chalk Formations. Rawson et al. (2001) [Fig.2/11, Fig3/6 and Fig.5a/11] formalised the terminology, agreed at the November 1999 meeting, using Chalk Group to cover a lower Grey Chalk Subgroup and a higher White Chalk Subgroup. These divided further into formations.		The '''Chalk Group''' has been in use informally for a number of years. Its first formal use was by Rhys (1974) [Fig.11/1] to cover the Chalk in the North Sea and by Wood and Smith (1978) [Fig.2/7 and Fig.6/5] to cover the whole of the Chalk succession in the ‘Northern Province’ but this also included the Red Chalk (now excluded from the definition as the Hunstanton Formation). Rawson et al. (1978) utilised the term Chalk Formation to cover the whole of the Chalk (Cenomanian to Maastrichtian). Robinson (1986) [Fig.2/9, Fig.3/2 and Fig.5a/8] in the North Downs and Mortimore (1986) [Fig.2/8, Fig.3/3 and Fig.5a/9], by implication, in the South Downs, used the term Chalk Group to cover the succession from the basal unconformity to the youngest known chalk beneath the Palaeogene unconformity in those areas. Bristow et al. (1997) [Fig.2/10, Fig.3/5 and Fig.5a/10] used Chalk Group to include Lower, Middle and Upper Chalk Formations. Rawson et al. (2001) [Fig.2/11, Fig3/6 and Fig.5a/11] formalised the terminology, agreed at the November 1999 meeting, using Chalk Group to cover a lower Grey Chalk Subgroup and a higher White Chalk Subgroup. These divided further into formations.

Line 6:		Line 6:
	A digest of the development of terminology in the Southern Province (and for the South-east Devon and Norfolk sequences) is given in Figures 5a-c.		A digest of the development of terminology in the Southern Province (and for the South-east Devon and Norfolk sequences) is given in Figures 5a-c.

	[[Image:P895005.~~png~~\|thumb\|left\|400px\| The development of the terminology in the Southern Province. ~~[http://bgsintranet/asset-bank/action/viewFullSizedImage?id=482034&size=1000~~ P895005.]]]		[[Image:P895005.jpg\|thumb\|left\|400px\| The development of the terminology in the Southern Province. P895005.]]
	[[Image:P895006.~~png~~\|thumb\|left\|400px\|The development of the terminology in south-east Devon (Southern Province). ~~[http://bgsintranet/asset-bank/action/viewFullSizedImage?id=482035&size=1000~~ P895006.]]]		[[Image:P895006.jpg\|thumb\|left\|400px\|The development of the terminology in south-east Devon (Southern Province). P895006.]]
	[[Image:P895007.~~png~~\|thumb\|left\|400px\| The development of the terminology in Norfolk (Transitional Province). ~~[http://bgsintranet/asset-bank/action/viewFullSizedImage?id=482036&size=1000~~ P895007.]]]		[[Image:P895007.jpg\|thumb\|left\|400px\| The development of the terminology in Norfolk (Transitional Province). P895007.]]
	The '''Grey Chalk Subgroup''' is defined as the succession from the basal Cenomanian unconformity up to the base of the Plenus Marl Member of the succeeding White Chalk Subgroup. It comprises two Formations a lower West Melbury Marly Chalk Formation and an upper Zig Zag Chalk Formation with the boundary between placed at the base of the Cast Bed. Historically this succession has been included within the Lower Chalk which itself has been further subdivided. A short review of the development of the terminology for this subgroup is given below.		The '''Grey Chalk Subgroup''' is defined as the succession from the basal Cenomanian unconformity up to the base of the Plenus Marl Member of the succeeding White Chalk Subgroup. It comprises two Formations a lower West Melbury Marly Chalk Formation and an upper Zig Zag Chalk Formation with the boundary between placed at the base of the Cast Bed. Historically this succession has been included within the Lower Chalk which itself has been further subdivided. A short review of the development of the terminology for this subgroup is given below.

Dbk at 13:56, 11 February 2014

2014-02-11T13:56:50Z

← Older revision		Revision as of 14:56, 11 February 2014
Line 6:		Line 6:
	A digest of the development of terminology in the Southern Province (and for the South-east Devon and Norfolk sequences) is given in Figures 5a-c.		A digest of the development of terminology in the Southern Province (and for the South-east Devon and Norfolk sequences) is given in Figures 5a-c.

	[[Image:P895005.png\|thumb\|left\|~~300px~~\| The development of the terminology in the Southern Province. [http://bgsintranet/asset-bank/action/viewFullSizedImage?id=482034&size=1000 P895005.]]]		[[Image:P895005.png\|thumb\|left\|400px\| The development of the terminology in the Southern Province. [http://bgsintranet/asset-bank/action/viewFullSizedImage?id=482034&size=1000 P895005.]]]
	[[Image:P895006.png\|thumb\|left\|~~300px~~\|The development of the terminology in south-east Devon (Southern Province). [http://bgsintranet/asset-bank/action/viewFullSizedImage?id=482035&size=1000 P895006.]]]		[[Image:P895006.png\|thumb\|left\|400px\|The development of the terminology in south-east Devon (Southern Province). [http://bgsintranet/asset-bank/action/viewFullSizedImage?id=482035&size=1000 P895006.]]]
	[[Image:P895007.png\|thumb\|left\|~~300px~~\| The development of the terminology in Norfolk (Transitional Province). [http://bgsintranet/asset-bank/action/viewFullSizedImage?id=482036&size=1000 P895007.]]]		[[Image:P895007.png\|thumb\|left\|400px\| The development of the terminology in Norfolk (Transitional Province). [http://bgsintranet/asset-bank/action/viewFullSizedImage?id=482036&size=1000 P895007.]]]
	The '''Grey Chalk Subgroup''' is defined as the succession from the basal Cenomanian unconformity up to the base of the Plenus Marl Member of the succeeding White Chalk Subgroup. It comprises two Formations a lower West Melbury Marly Chalk Formation and an upper Zig Zag Chalk Formation with the boundary between placed at the base of the Cast Bed. Historically this succession has been included within the Lower Chalk which itself has been further subdivided. A short review of the development of the terminology for this subgroup is given below.		The '''Grey Chalk Subgroup''' is defined as the succession from the basal Cenomanian unconformity up to the base of the Plenus Marl Member of the succeeding White Chalk Subgroup. It comprises two Formations a lower West Melbury Marly Chalk Formation and an upper Zig Zag Chalk Formation with the boundary between placed at the base of the Cast Bed. Historically this succession has been included within the Lower Chalk which itself has been further subdivided. A short review of the development of the terminology for this subgroup is given below.

Dbk at 13:48, 11 February 2014

2014-02-11T13:48:41Z

← Older revision		Revision as of 14:48, 11 February 2014
Line 6:		Line 6:
	A digest of the development of terminology in the Southern Province (and for the South-east Devon and Norfolk sequences) is given in Figures 5a-c.		A digest of the development of terminology in the Southern Province (and for the South-east Devon and Norfolk sequences) is given in Figures 5a-c.

	[[Image:P895005.png\|thumb\|300px\| The development of the terminology in the Southern Province. [http://bgsintranet/asset-bank/action/viewFullSizedImage?id=482034&size=1000 P895005.]]]		[[Image:P895005.png\|thumb\|left\|300px\| The development of the terminology in the Southern Province. [http://bgsintranet/asset-bank/action/viewFullSizedImage?id=482034&size=1000 P895005.]]]
	[[Image:P895006.png\|thumb\|300px\| The development of the terminology in south-east Devon (Southern Province). [http://bgsintranet/asset-bank/action/viewFullSizedImage?id=482035&size=1000 P895006.]]]		[[Image:P895006.png\|thumb\|left\|300px\|The development of the terminology in south-east Devon (Southern Province). [http://bgsintranet/asset-bank/action/viewFullSizedImage?id=482035&size=1000 P895006.]]]
	[[Image:P895007.png\|thumb\|300px\| The development of the terminology in Norfolk (Transitional Province). [http://bgsintranet/asset-bank/action/viewFullSizedImage?id=482036&size=1000 P895007.]]]		[[Image:P895007.png\|thumb\|left\|300px\| The development of the terminology in Norfolk (Transitional Province). [http://bgsintranet/asset-bank/action/viewFullSizedImage?id=482036&size=1000 P895007.]]]
	The '''Grey Chalk Subgroup''' is defined as the succession from the basal Cenomanian unconformity up to the base of the Plenus Marl Member of the succeeding White Chalk Subgroup. It comprises two Formations a lower West Melbury Marly Chalk Formation and an upper Zig Zag Chalk Formation with the boundary between placed at the base of the Cast Bed. Historically this succession has been included within the Lower Chalk which itself has been further subdivided. A short review of the development of the terminology for this subgroup is given below.		The '''Grey Chalk Subgroup''' is defined as the succession from the basal Cenomanian unconformity up to the base of the Plenus Marl Member of the succeeding White Chalk Subgroup. It comprises two Formations a lower West Melbury Marly Chalk Formation and an upper Zig Zag Chalk Formation with the boundary between placed at the base of the Cast Bed. Historically this succession has been included within the Lower Chalk which itself has been further subdivided. A short review of the development of the terminology for this subgroup is given below.

Dbk at 13:48, 11 February 2014

2014-02-11T13:48:04Z

← Older revision		Revision as of 14:48, 11 February 2014
Line 6:		Line 6:
	A digest of the development of terminology in the Southern Province (and for the South-east Devon and Norfolk sequences) is given in Figures 5a-c.		A digest of the development of terminology in the Southern Province (and for the South-east Devon and Norfolk sequences) is given in Figures 5a-c.

			[[Image:P895005.png\|thumb\|300px\| The development of the terminology in the Southern Province. [http://bgsintranet/asset-bank/action/viewFullSizedImage?id=482034&size=1000 P895005.]]]
			[[Image:P895006.png\|thumb\|300px\| The development of the terminology in south-east Devon (Southern Province). [http://bgsintranet/asset-bank/action/viewFullSizedImage?id=482035&size=1000 P895006.]]]
			[[Image:P895007.png\|thumb\|300px\| The development of the terminology in Norfolk (Transitional Province). [http://bgsintranet/asset-bank/action/viewFullSizedImage?id=482036&size=1000 P895007.]]]
	The '''Grey Chalk Subgroup''' is defined as the succession from the basal Cenomanian unconformity up to the base of the Plenus Marl Member of the succeeding White Chalk Subgroup. It comprises two Formations a lower West Melbury Marly Chalk Formation and an upper Zig Zag Chalk Formation with the boundary between placed at the base of the Cast Bed. Historically this succession has been included within the Lower Chalk which itself has been further subdivided. A short review of the development of the terminology for this subgroup is given below.		The '''Grey Chalk Subgroup''' is defined as the succession from the basal Cenomanian unconformity up to the base of the Plenus Marl Member of the succeeding White Chalk Subgroup. It comprises two Formations a lower West Melbury Marly Chalk Formation and an upper Zig Zag Chalk Formation with the boundary between placed at the base of the Cast Bed. Historically this succession has been included within the Lower Chalk which itself has been further subdivided. A short review of the development of the terminology for this subgroup is given below.