Chalk of the UK - Appendix 3: Redundant terms on BGS maps and other schemes used in the ‘Southern Province’

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There are a number of entries that appear in the BGS Lexicon and within commonly quoted references that need to be understood in terms of the lithostratigraphical framework presented herein. Lexicon style entries are given for terms that have appeared on BGS maps but are now considered to be redundant. A further set of terms from four of the principal references concerned with the definition of the Chalk are also given.

The following entries cover terms utilised on BGS maps and, mostly, those that appear in the Lexicon. For the most part these are now redundant terms and frequently poorly defined with respect to formal lithostratigraphies or unit status. Their closest equivalent term in the New Chalk Stratigraphy is given if possible. They are shown in alphabetical order.

Contents

BLANDFORD CHALK MEMBER

Name

The term Blandford Chalk Member was used by Bristow et al. (1995) to describe the succession between the Lewes Nodular Chalk and Tarrant Chalk of the Shaftsbury area where they could not distinguish the Seaford Chalk and Newhaven Chalk members.

Type section

General area around Blandford Forum, Dorset.

Primary Reference Section

Old railway cutting on the military sidings, Blandford, (see Bristow, et al. 1995).

Formal subdivision

None but now regarded as the Seaford and Newhaven Chalk formations undivided.

Lithology

Firm, smooth, white flinty chalk; some thin marl seams present.

Definition of upper boundary

Conformable at the incoming of soft to firm smooth white chalk with conspicuous large flint seams and including the fauna indicative of the quadrata Zone.

Definition of lower boundary

Conformable at the change from hard nodular chalk, to firm smooth chalk.

Thickness

75 to 90m in the Shaftsbury area.

Distribution

Confined to the Shaftsbury Geological Sheet 313 area.

Previous names

None but would now be considered to be an amalgamation of the Seaford Chalk Formation and the Newhaven Chalk Formation undivided. Term is redundant except for its use on the Shaftsbury sheet area.

Parent

White Chalk Subgroup.

Age and biostratigraphy

Upper Cretaceous, Coniacian, Santonian and basal Campanian. Micraster coranguinum to Offaster pilula Zones.

References

Barton (1991); Bristow et al. (1995); Gaster (1944); Bristow (1990a). Mortimore (1986).

BRANDON FLINT SERIES

Name

First called the Horizon of the Brandon Flint Series in Hewitt (1935) and used as the Brandon Flint Series in the Bury St. Edmunds memoir (Bristow, 1990b).

Type section

Named after Grimes Graves flint Mines near Brandon.

Primary Reference Section

Skertchly (1879) refers to pits at Lingheath (Brandon Park), Santon Downham, Broomhill, Icklingham and Elvedon.

Formal subdivision

None but divided into a number named flint and marl beds.

Lithology

Massive bedded chalks with marl seams and tabular and nodular flints.

Definition of upper boundary

Conformable below the hard yellow nodular chalk of the Chalk Rock.

Definition of lower boundary

Conformable, below the lowest major flint seam (the Rough and Smooth Blacks), which occur below the Grimes Graves Marl. A position that is regarded as marking the base of the plana Zone.

Thickness

Between 12 and 15 m at Lingheath (Skertchly, 1879; Bristow, 1990b).

Distribution

Central East Anglia around Bury St. Edmunds within the Transitional Province. Its extent is not mapped.

Previous names

Brandon Flints

Parent

Lewes Nodular Chalk Formation.

Age and biostratigraphy

Upper Cretaceous, Turonian. Sternotaxis plana (now Plesiocorys plana) Zone.

References

Skertchly (1879);. Hewitt (1935); Bristow (1990b).

CHALK MARL

Name

Informal term as part of the terminology for used in the traditional scheme as exemplified in Jukes-Browne and Hill (1903) but in existence prior to that date.

Type section

Folkestone in Kent, Compton Bay on the Isle of Wight.

Primary Reference Section

See above

Formal subdivision

None but contains some informally named units.

Lithology

Rhythmically bedded marly chalk (argillaceous limestone) and marl (silty calcareous mudstone) with no flint.

Definition of upper boundary

Disconformable beneath the erosion surface at the base of the Totternhoe Stone (see also Chilton Stone) of the ‘Transitional’ Province as defined by Jukes-Browne and Hill (1903) and its lateral equivalent of the ‘Cast Bed’ of the Southern Province.

Definition of lower boundary

Conformable at an indistinct horizon at the contact between the ‘Chloritic’ Marl (Glauconitic Marl) and the Chalk Marl as defined in Jukes-Browne and Hill (1903). In modern usage this would equate to the top of the Glauconitic Marl Member (Southern Province) or the Cambridge Greensand Member (‘Transitional’ Province).

Thickness

Generally in the range 15 to 40 m throughout the Southern and ‘Transitional’ Provinces. Becomes thin or absent in basin margin situations such as the mid-Dorset Swell and in Devon.

Distribution

The term was used widely within the Southern and Transitional provinces to denote the lower part of the Lower Chalk.

Previous names

Longstanding term from the ‘Traditional’ scheme of Chalk nomenclature, Lower Chalk (Chalk Marl), also referred to as the Lower Beds (Chalk Marl) on the Cambridge Sheet (188). The unit is approximately equivalent to the West Melbury Marl Chalk Formation and the basal Zig Zag Chalk Formation but with important differences as to the definition of its lower and upper boundaries.

Parent

Not definable in new terminology forms part of the Lower Chalk of the traditional scheme.

Age and biostratigraphy

Upper Cretaceous, Cenomanian. Mantelliceras mantelli to Acanthoceras rhotomagense Zones.

References

Jukes-Browne and Hill (1903), for its usage by the Geological Survey, but the term had been in existence for some considerable time prior to that publication in both Survey publications and in journals.

CHILTON STONE

Name

First used by Jukes-Browne (1889) to denote a bed that was equated to the Totternhoe Stone of the Chilterns.

Type section

Railway cutting east of Chilton, Oxfordshire.

Primary Reference Section

As above

Formal subdivision

None

Lithology

Brownish grey limestone. Rough to the touch (‘gritty’) with many phosphatic nodules.

Definition of upper boundary

Commonly indistinct conformable boundary within the Zig Zag Chalk Formation (Lower Chalk, Grey Chalk unit). Upward reversion to softer, finer grained more typical chalk or marly chalk. May be difficult to locate, even in sections.

Definition of lower boundary

Commonly indistinct conformable boundary with the underlying West Melbury Marly Chalk Formation (Lower Chalk, Chalk Marl unit) but there may be an erosion surface with concentration of phosphatic pebbles in base. May be difficult to locate, even in sections.

Thickness

0.6m at its type-site in the cutting east of Chilton on the Didcot to Newbury railway line. Distribution

Limited to a small area of Berkshire.

Previous names

Equivalent to the Totternhoe Stone of the Chilterns and regarded as the most southwesterly outcrop of that unit.

Parent

Zig Zag Chalk Formation.

Age and biostratigraphy

Upper Cretaceous, Cenomanian. Acanthoceras rhotomagense Zone.

References

Jukes-Browne (1889); Jukes-Browne and Hill (1889).

LOWER CHALK

Name

The term is used for the lowest part of the traditional tripartite scheme of the Chalk (Jukes-Browne and Hill, 1903) and as used is equivalent to a formation.

Type section

Chiltern Hills area utilised to define the Lower Chalk in much of the early literature (Hill and Jukes-Browne, 1886, Jukes-Browne and Hill, 1903).

Primary Reference Section

Compton Bay, Isle of White

Beachy Head to Eastbourne in Sussex

Folkestone towards Dover in Kent.

Formal subdivision Divided into the Glauconitic Marl, Chalk Marl, Totternhoe Stone (where present), Grey Chalk, ‘White Bed’ and Plenus Marls in the traditional scheme.

Lithology

A grey marly chalk with marl content decreasing upwards. No flint. Comprises a thin basal bed of glauconitic marl (Glauconitic Marl, Melbury Sandstone or Cambridge Greensand) overlain by more typical Lower Chalk sequence that is usually divided into a lower "Chalk Marl"(see West Melbury Marly Chalk Formation entry) with rhythmic alternations of chalk and marl, and an upper "Grey Chalk" (see Zig Zag Chalk Formation entry) separated by a distinctive hard band (Cast Bed or Totternhoe Stone). (See entries for Grey Chalk and White Chalk Subgroups).

Definition of upper boundary

Conformable at the top of the highest marl within the Plenus Marls Member. (Refer to entries for

Zig Zag Chalk and Holywell Nodular Chalk Formations).

Definition of lower boundary

At an unconformity at the base of Glauconitic Marl, Melbury Sandstone or Cambridge Greensand ‘Members’ at the base of the West Melbury Marly Chalk Member (see reference to Grey Chalk Subgroup and West Melbury Marly Chalk Formation).

Thickness

45 to 100m in the Southern and ‘Transitional’ Provinces. Thinner sequences known towards the margins of the Chalk basin and over synsedimentary highs.

Distribution

Throughout the Southern and Transitional provinces and prior to Wood and Smith (1978) used in the Northern Province.

Previous names

Lower Chalk, formerly applied throughout the Chalk outcrop in England but now only utilised to describe those chalks within the Southern and ‘Transitional’ Provinces beneath the Melbourn Rock in the traditional scheme. Have constituent parts of the Glauconitic Marl, Chalk Marl, Totternhoe Stone (where present), Grey Chalk, ‘White Bed’ and Plenus Marls. Its use is not recommended for descriptive purposes and should be replaced by the term Grey Chalk Subgroup (but see definition) or the constituent Formations within the new scheme.

Lower Chalk (Grey Chalk)

Lower Chalk Formation as utilised in Bristow, Mortimore and Wood (1997) in an early version of the new Chalk stratigraphy, is the direct equivalent of the Lower Chalk of the traditional scheme.

Lower Chalk without flints as utilised on the Selby Sheet (71) and Chalk without flint as on the York Sheet (63) (Revision of these sheets will follow the Northern Province terminology). This term is also prevalent in the 19th century literature where it can include the lower flint-free part of the traditional Middle Chalk depending on the author and the area within which the chalks are described.

Lower Beds (Chalk Marl, h5a1) and Upper Beds (h5a2) as utilised on the Cambridge Sheet (188) to denote those beds below and above the Totternhoe Stone.

Parent

Chalk Group.

Age and biostratigraphy

Upper Cretaceous, Cenomanian. Mantelliceras mantelli to Metoicoceras geslinianum Zones.

References

Penning and Jukes-Browne (1881); Rawson et al. (1978).

LOWER CHALK FORMATION

Name

This term was erected by Bristow, Mortimore and Wood (1997) to cover the interval of their West Melbury Marly Chalk Member and Zig Zag Chalk Member in recognition of the widespread use of the Lower Chalk in the traditional scheme. It use is not recommended and is now redundant.

Type section

At the type sections of its constituent members.

Primary Reference Section

Compton Bay, Isle of White

Beachy Head to Eastbourne in Sussex

Folkestone towards Dover in Kent.

Formal subdivision

Divided into the West Melbury Marly Chalk Member and the Zig Zag Chalk Member.

Age and biostratigraphy

Upper Cretaceous, Cenomanian. Mantelliceras mantelli to Metoicoceras geslinianum Zones.

Lithology

A grey marly chalk with marl content decreasing upwards. No flint. Comprises a thin basal bed of glauconitic marl (Glauconitic Marl, Melbury Sandstone or Cambridge Greensand) overlain by more typical Lower Chalk sequence that is usually divided into a lower "Chalk Marl"(see West Melbury Marly Chalk Formation entry) with rhythmic alternations of chalk and marl, and an upper "Grey Chalk" (see Zig Zag Chalk Formation entry) separated by a distinctive hard band. (Cast Bed or Totternhoe Stone). (See entries for Grey Chalk and White Chalk subgroups).

Definition of upper boundary

Conformable at the top of the highest marl within the Plenus Marls Member. (Refer to entries for Grey Chalk Subgroup, White Chalk Subgroup, Zig Zag Chalk and Holywell Nodular Chalk Formations).

Definition of lower boundary

At an unconformity at the base of Glauconitic Marl, Melbury Sandstone or Cambridge Greensand ‘Members’ at the base of the West Melbury Marly Chalk Member (see reference to Grey Chalk Subgroup and West Melbury Marly Chalk Formation).

Thickness

45 to 100m in the Southern and ‘Transitional’ Provinces. Thinner sequences known towards the margins of the Chalk basin and over synsedimentary highs.

Distribution

Throughout the Southern and Transitional provinces.

Previous names

Lower Chalk of the traditional scheme.

Chalk without flints used on the York Sheet (63) and Lower Chalk (without flints) used on the Selby Sheet (71) Sheet due for revision when the newer Yorkshire/Lincolnshire terminology will be applied (Hunstanton and Ferriby Chalk Formations). This term is also prevalent in the 19th century literature where it can include the lower flint-free part of the traditional Middle Chalk depending on the author and the area within which the chalks are described.

Lower Chalk (Grey Chalk).

Parent

Chalk Group

References

Bristow, Mortimore and Wood (1997); Rawson et al. (1978).

MIDDLE CHALK

Name

The term is used for the middle part of the traditional tripartite scheme of the Chalk (Jukes-Browne and Hill, 1903) and as used is equivalent to a formation.

Type section

Chiltern area utilised to define the Lower Chalk in much of the early literature (Hill and Jukes-Browne, 1886).

Primary Reference Section

Compton Bay, Isle of White; Beachy Head to Eastbourne in Sussex and Folkestone towards Dover in Kent.

Formal subdivisions

Included the Melbourn Rock as its basal unit.

Lithology

White pure chalk with some flint seams and very shelly beds. Comprises from base: hard indurated chalk with flaser marls (Melbourn Rock) to exceptionally shelly chalk with flints into chalk with well defined marl seams.

Definition of upper boundary

Bedding plane beneath the Chalk Rock in the Chilterns (‘Transitional Province) and beneath the equivalent beds containing the ‘reussianum fauna’ elsewhere in the Southern Province.

Definition of lower boundary

Conformable at the base of Melbourn Rock above highest marl within Plenus Marls.

Thickness

75 - 95m in the Southern and ‘Transitional’ Provinces. Thinner sequences known towards the margins of the Chalk basin and over synsedimentary highs.

Distribution

Throughout the Southern and Transitional provinces.

Previous names

Chalk with few flints.

Chalk with flints (Middle Chalk) on the York Sheet (63) and Middle Chalk with flint on the Selby Sheet (71). Sheets due for revision when the newer Yorkshire/Lincolnshire terminology will be applied (Hunstanton and Ferriby Chalk Formations). This term is also prevalent in the 19th century literature where it can include the lower flint-free part of the traditional Middle Chalk depending on the author and the area within which the chalks are described.

Parent

Chalk Group.

Age and biostratigraphy

Upper Cretaceous Cenomanian and Turonian. Neocardioceras juddii to Terebratulina lata Zones.

References

Penning and Jukes-Browne (1881).

MIDDLE CHALK FORMATION

Name

This term was erected by Bristow, Mortimore and Wood (1997) to cover the interval of their Holywell Nodular Chalk Member and New Pit Chalk Member in recognition of the widespread use of the Middle Chalk in the traditional scheme. It use is not recommended and is now redundant.

Type section

At the type sections of its constituent members.

Primary Reference Section

Compton Bay, Isle of White; Beachy Head to Eastbourne in Sussex and Folkestone towards Dover in Kent.

Formal subdivision

Includes the Melbourn Rock as its basal unit.

Lithology

White pure chalk with some flint seams and very shelly beds. Comprises from base: hard indurated chalk with flaser marls (Melbourn Rock) to exceptionally shelly chalk with flints into chalk with well defined marl seams. Holywell Nodular Chalk Member and New Pit Chalk Member are its constituent parts.

Definition of upper boundary

Coincident with the base of the Lewes Nodular Chalk Member. Conformable at the incoming of nodular chalk and regular flint seams.

Definition of lower boundary

Conformable at the base of the Melbourn Rock.

Thickness

75 - 95m in the Southern and ‘Transitional’ Provinces. Thinner sequences known towards the margins of the Chalk basin and over synsedimentary highs.

Distribution

Throughout the Southern and Transitional provinces.

Previous names

Middle Chalk of the traditional scheme.

Chalk with few flints

Chalk with flints (Middle Chalk) on the York Sheet 63 and Middle Chalk with flints on the Selby Sheet 71. Sheets due for revision when the newer Yorkshire/ Lincolnshire terminology will be applied. This term is also prevalent in the 19th century literature.

Parent

Chalk Group

Age and biostratigraphy

Upper Cretaceous Cenomanian and Turonian. Neocardioceras juddii to Terebratulina lata Zones.

References

Bristow, Mortimore and Wood (1997); Rawson et al. (1978).

RED CHALK

Name

The term Red Chalk is of great antiquity being used since the middle of the 19th century. It has been used generally subsequently often including Hunstanton in its title. Now redefined as the Hunstanton Formation.

Type section

Hunstanton Cliff [TF 6725 4130 to TF 6786 4238], north Norfolk (Owen, 1995; Gallois, 1994).

Primary Reference Section

South Ferriby Quarry [SE 9915 2045], Lincolnshire (Gaunt et al., 1992).

Formal subdivision

None

Lithology

Rubbly to massive chalks with marl bands; typically pink to brick-red in colour (due to disseminated hematite), but locally upper part grey due to secondary alteration of the iron minerals. Commonly sandy, particularly in lower part.

Definition of upper boundary

Erosion surface, locally developed as a hardground, overlain by nodular chalk (lowest Cenomanian) of Paradoxica (or Sponge) Bed or (in Cleveland Basin) Crowe’s Shoot Member (Mitchell, 1995); this horizon (the base of the Lower Chalk in Norfolk, or elsewhere of the Ferriby Formation) may or may not correspond with the upper limit of red chalks.

Definition of lower boundary

Sharp or [apparently] gradational boundary of marly chalks with ferruginous sandstones of Carstone Formation in the Transitional Province, Lincolnshire and Yorkshire or (in Cleveland Basin) with mudstone of Speeton Clay Formation; commonly marked by a line of phosphatic nodules (burrow-fills).'

Thickness

c. 1 m at type section in Norfolk, typically 3 m in Lincolnshire and south Yorkshire, thinning over Market Weighton High but expanding up to c. 30 m in Cleveland Basin with c. 24 m in cliffs at Speeton.

Distribution

North Norfolk, Lincolnshire and Yorkshire in the Northern Province.

Previous names

Red Chalk; Red Chalk Member as part of the Ferriby Formation as per Wood and Smith (1978); Red Chalk (Hunstanton Member) as above. Hunstanton Limestone; Hunstanton Red Rock; Hunstanton Chalk Formation; Hunstanton Red Chalk Formation (Owen, 1995); Hunstanton Chalk Member (Wood and Smith, 1978).'

Parent

Not definable in the new terminology, as the Hunstanton Formation it is a stand-alone unit excluded from the Chalk Group. Part of the Ferriby Chalk Formation of Wood and Smith (1978).

Age and biostratigraphy

Lower Cretaceous, Albian.

References

Owen (1995), as modified herein (see entry for Hunstanton Chalk Formation).

UINTACRINUS BAND

Name

A term used on the Faversham and Ramsgate Geological Sheets to denote a mappable boundary within the Upper Chalk.

Type section

Graves in St. Peters churchyard [TR 3779 6862].

Primary Reference Section

Top of Cliff at Foreness Point (see Rasmussen, 1961).

Formal subdivision

None

Lithology

Soft white chalk with some flints.

Definition of upper boundary

At the incoming of the Offaster pilula index fossil.

Definition of lower boundary

At the incoming of the zonal index fossil.

Thickness

2 to 3m at the top of the Zone of Marsupites Testudinarius as originally defined in Kent.

Distribution

Confined to the Faversham and Ramsgate geological sheets.

Previous names

None

Parent

Newhaven Chalk Formation.

Age and biostratigraphy

Upper Cretaceous, Campanian. Uintacrinus anglicus Zone.

References

Shephard-Thorn (1988).

UPPER CHALK

Name

The term is used for the highest part of the traditional tripartite scheme of the Chalk (Jukes-Browne and Hill, 1903) and as used is equivalent to a formation.

Type section

Type areas of East Kent Cliffs, Sussex Cliffs, Isle of Wight and Dorset cliffs.

Primary Reference Section

See above

Formal subdivision

Includes the Chalk Rock as its basal unit.

Lithology

Generally soft white chalk with flints and marl seams throughout. Variation in the relative proportions of marl and flint seams indicative of major constituent units. Hard nodular chalks at base.

Definition of upper boundary

Unconformable and limited by the pre-Palaeogene erosion surface.

Definition of lower boundary

Conformable and placed at the base of the Chalk Rock in the ‘Transitional’ Province and at the lowest nodular chalk containing the Hyphantoceras reussianum fauna in the Southern Province, or at the base of the ‘Basal Complex’ in East Kent. When used in the Northern Province the boundary is at a horizon marking the base of the Sternotaxis plana (now Plesiocorys plana) Zone.

Thickness

Variable depending on degree of post-Cretaceous erosion and the relative development of its constituent formations. Onshore the thickest development is within the Hampshire/Sussex area of the Southern Province, where up to about 470 to 515m of strata are preserved; the most chronostratigraphically complete succession is in Norfolk but is thought there to be only some 350m thick; within the Northern Province up to 500m are preserved but the thickest succession is within the North Sea area where about 800 to 1100m are preserved.

Distribution

Throughout the Southern and Transitional provinces.

Previous names

Upper Chalk with flint of BGS usage and is also prevalent in the 19th century literature.

Substantially equivalent to the Upper Chalk Formation of Bristow, Mortimore and Wood (1997), and the White Chalk Subgroup of Rawson, Allen and Gale (2001).

Parent

Chalk Group.

Age and biostratigraphy

Upper Cretaceous, Turonian to Maastrichtian. Sternotaxis plana (now Plesiocorys plana) Zone to highest belemnite zones preserved.

References

Jukes-Browne and Hill (1903, 1904).

UPPER CHALK FORMATION

Name

This term was erected by Bristow, Mortimore and Wood (1997) to cover the interval of their Lewes Nodular Chalk Member to the Portsdown Chalk Member in recognition of the widespread use of the Upper Chalk in the traditional scheme. It use is not recommended and is now redundant.

Type section

At the type sections of its constituent members.

Primary Reference Section

Compton Bay, Isle of White; Beachy Head to Eastbourne in Sussex and Folkestone towards Dover in Kent.

Formal subdivision

Includes the Lewes Nodular Chalk Member, Seaford Chalk Member, Newhaven Chalk Member, Tarrant Chalk Member, Spetisbury Chalk Member and Portsdown Chalk Member.

Lithology

Generally soft white chalk with flints and marl seams throughout. Variation in the relative proportions of marl and flint seams indicative of major constituent units. Hard nodular chalks at base.

Definition of upper boundary

Unconformable and limited by the pre-Palaeogene erosion surface.

Definition of lower boundary

Conformable, coincident with the base of the Lewes Nodular Chalk Member (of Bristow, Mortimore and Wood, 1997) and the Lewes Nodular Chalk Formation (of Rawson, Allen and Gale, 2001). It is placed at the incoming of hard nodular chalks and regular well-developed flint seams. This horizon is known to be diachronous in the Southern and ‘Transitional’ Provinces.

Thickness

Variable depending on degree of post-Cretaceous erosion and the relative development of its constituent formations. Onshore the thickest development is within the Hampshire/Sussex area of the Southern Province, where up to about 470 to 515m of strata are preserved; the most chronostratigraphically complete succession is in Norfolk but is thought there to be only some 350m thick; within the Northern Province up to 500m are preserved but the thickest succession is within the North Sea area where about 800 to 1100m are preserved.

Distribution

Throughout the Southern and Transitional provinces.

Previous names

Upper Chalk.

Upper Chalk with flints.

Parent

Chalk Group.

Age and biostratigraphy

Upper Cretaceous, Turonian to Maastrichtian. Terebratulina lata Zone to highest belemnite zones preserved.

References

Bristow, Mortimore and Wood (1997); Rawson et al. (1978).

The following is a list of terms appearing in the major lithostratigraphical papers. They are terms that are infrequently utilised in BGS descriptive texts. An attempt has been made to give the relevant parent unit or approximate correlative term within the New Chalk Stratigraphy. For the most part these terms can be considered as being at Member or Bed level

Mortimore (1986)

This paper essentially deals with the beds attributable to the Middle and Upper Chalk of the Traditional Scheme for which he adopted the term the Sussex White Chalk Formation and which he further divided into six members. The units so described are designated from his study of the thicker ‘basinal’ chalk sequences exposed on the coast and in large inland sites in the South Downs, Hampshire/Wiltshire ‘Downs’ and the Isle of Wight. The Lower Chalk of the area was not considered in this paper. The essential elements of this study formed the basis for the mapping scheme whose development resulted in the presently accepted unified scheme (Rawson, Allen and Gale, 2001). It follows that many of the terms described below (i.e. Formation, Member and Bed) would be considered at the next higher level in the unified scheme. Numerous marker flint, marl, hardground and other units at bed level are given codes in the BGS Lexicon for use in borehole coding. They are not defined further in the lexicon and reference should always be made to Mortimore (1986) for their understanding.

Sussex White Chalk Formation

Base is at the junction of the Melbourn Rock and the underlying Plenus Marls as traditionally defined, with the top of the formation limited beneath the sub-Palaeogene erosion surface. Essentially equivalent to the White Chalk Subgroup with the proviso that the Plenus Marls are excluded from the Sussex White Chalk Formation.

Ranscombe Chalk Member

The basal member of the Sussex White Chalk Formation whose lower boundary is coincident with the base of the Melbourn Rock. This unit covers the majority of the Middle Chalk of the traditional scheme and is equivalent to the Holywell Nodular Chalk Formation (excluding the Plenus Marls Member) and the New Pit Chalk Formation. Overlain by the Lewes Nodular and Flinty Chalk Member.

'Melbourn Rock The basal unit of the Ranscombe Chalk Member and the Sussex White Chalk Formation. As defined is most closely equivalent to the traditional understanding of the Melbourn Rock of the Chilterns and Thames valley. Base placed at the Foyle Marl.'

Holywell Beds As originally defined the beds are divided into Lower, Middle and Upper units whose bases are placed respectively at the Meads Marl 1, Gun Gardens Marl 1 and the Gun Gardens Main Marl. This was modified (Mortimore and Pomerol, 1996) with the Upper unit considered to be equivalent to the lowest part of the New Pit Chalk Member as defined in BGS mapping. With the Melbourn Rock, the Lower and Middle Holywell Beds are equivalent to the Holywell Chalk Member of Bristow, Mortimore and Wood (1997) and with the further addition of the Plenus Marls Member equivalent to the Holywell Nodular Chalk Formation of Rawson, Allen and Gale (2001)

New Pit Beds As originally defined the beds covered the interval from the Malling Street Marls to the Glynde Marl 1. This was modified (Mortimore and Pomerol, 1996) with the Upper unit of the Holywell Beds considered to be equivalent to the lowest part of the New Pit Chalk Member, and the top of the Member being taken at the incoming of nodular chalks, as defined in BGS mapping (Bristow, Mortimore and Wood, 1997), which is invariably in the Glynde Marl 4 to Southerham Marl 1 interval. The New Pit Chalk Member so defined is the direct equivalent of the New Pit Chalk Formation of Rawson, Allen and Gale (2001).

Lewes Nodular and Flinty Chalk Member

As originally defined the Member covered the interval between the Glynde Marl 1 and the uppermost of the Shoreham Marls including most of the nodular flinty chalks of Turonian and Coniacian age. The member includes an informal Lower and Upper part. This was modified in Mortimore and Pomerol (1996) with the Lower Lewes Nodular Chalk defined as the sequence from the inception of nodularity (immediately above the Glynde Marl 4 in Sussex) to the Lewes Marl; and (presumably) the Upper Lewes Nodular Chalk from the Lewes Marl to the Shoreham Marl 2. In total this member has the same definition as the Lewes Nodular Chalk Member of Bristow, Mortimore and Wood (1997) and accords with the definition of the Lewes Nodular Chalk Formation of Rawson, Allen and Gale (2001) as applied to the basinal sequences of the Southern Province. The inception of nodularity becomes younger northwards into the Transitional Province i.e. the base of the Formation is diachronous up to approximately the level of the Ringmer/Kingston Beds.

Glynde Beds Basal marker is Glynde Marl 1. This interval contains the boundary between the New Pit Chalk and Lewes Nodular Chalk Formations of Rawson, Allen and Gale (2001) as defined in the Southern Province.

Caburn Beds Basal marker Southerham Marl 1.

Ringmer Beds Basal marker the Caburn Marl. In the Transitional Province the Caburn Marl is the lateral equivalent of the Reed Marl, which is beneath the inception of nodularity (the Chalk Rock Member) in the Reed Quarry. Known as the Bridgewick Beds (Mortimore, 1983).

Kingston Beds Basal marker the Bridgewick Marl 1, includes the distinctive fauna of the Chalk Rock Member.

South Street Beds Basal marker Lewes Marl. Known as Lewes Beds (Mortimore, 1983).

Navigation Beds Basal marker Snowdrop Flint 1.

Cliffe Beds Basal marker the upper Navigation Marl.

Hope Gap Beds Basal marker the top surface of the Cliffe Hardground.

Beeding Beds Basal marker the top surface of the Hope Gap Hardground.

Light Point Beds Basal marker the top surface of the Beeding Hardground.

Beachy Head Beds Basal marker the top surface of the uppermost Light Point Hardground.

Seaford Chalk Member

As originally defined the Member covered the interval between the Shoreham Marl 2 and the Buckle Marl 1. This is equivalent to the member concept in Bristow, Mortimore and Wood (1997) and the Seaford Chalk Formation of Rawson, Allen and Gale (2001).

Belle Tout Beds Basal marker the Shoreham Marl 2

Cuckmere Beds Basal marker the Seven Sisters Flint.

Haven Brow Beds Basal marker the Michel Dean Flint. Known as Seaford Head Beds (Mortimore, 1983).

Newhaven Chalk Member

As originally defined the Member covered the interval between the Buckle Marl 1 and the Castle Hill Marl 2. This is equivalent to the member concept of Bristow, Mortimore and Wood (1997) with the proviso that in full sequences in structural lows additional marls are strongly developed (the Pepper Box Marls) above the Castle Hill Marls. This higher level marks the mapping boundary in this situation.

Splash Point Beds Basal marker the Buckle Marl 1.

Old Nore Beds Basal marker the Brighton Marl.

Peacehaven Beds Basal marker the Old Nore Marl.

Meeching Beds Basal marker the Peacehaven Marl.

Bastion Steps Beds Basal marker the Meeching Paired Marl.

Culver Chalk Member

As originally defined the member covered the interval between the Castle Hill Marl 2 and the Portsdown Marl. This is equivalent to the member concept of Bristow, Mortimore and Wood (1997) with the proviso that the mapping base may be slightly lower at the Arundel Sponge Beds or slightly higher at the Pepper Box Marls. It conforms to the definition of the Culver Chalk Formation of Rawson, Allen and Gale (2001).

Castle Hill Beds Basal marker the Castle Hill Marl 2.

Sompting Beds Basal marker the Lancing Flint.

Whitecliff Beds Basal marker the Whitecliff Marl.

Portsdown Chalk Member

As originally defined the member covered the interval from the Portsdown Marl up to the sub-Palaeogene unconformity in the Southern Province. This upper level is some distance (c. 8m) above the Shide Marl as exposed at Whitecliffe Bay on the Isle of White (as in Mortimore, 1986) but younger chalks are known at this locality (Mortimore, Wood and Gallois, 2001) and elsewhere on the Isle of Wight and in Dorset. Gale, Wood and Bromley (1987) introduced the term of Studland Chalk of ‘member’ status to define the marl-free soft white chalk with large flints in the upper part of the chalk exposed in Scratchells Bay and Alum Bay and on the Dorset coast in Studland Bay. It is not discernible from the published literature at what level the division of the Portsdown and Studland ‘members’ of Gale, Wood and Bromley (1987) occurs in the highest preserved chalk sequence. This doubt together with the lack of exposure and geomorphological expression of the member has led to the BGS reverting to the original concept of the Portsdown Chalk Member (Bristow, Mortimore and Wood, 1997). This is also the position stated in Rawson, Allen and Gale (2001) and thus the Portsdown Chalk Formation covers all of the chalk up to the sub-Palaeogene erosion surface in the Southern Province.

Redoubt Beds Basal marker the Portsdown Marl

Robinson (1986)

This paper describes and erects a lithostratigraphical terminology for the chalk of the North Downs. The paper reclassifies the Lower, Middle and Upper Chalk of the Traditional Scheme on the basis of distinct types of chalk and associations. The sequence is divided completely into five formations and nine members with a large part of the lowest formation being undivided at member level. It is not easy to correlate the divisions of Robinson to biostratigraphical terminology without significant knowledge of the literature, however the sequence is essentially the same and can be described using the terms as defined in Sussex by Mortimore (1986). Thus the work is largely redundant in terms of the new agreed lithostratigraphical framework.

East Wear Bay Chalk Formation

Defined on the coastal section between Copt Point [TR 242 365], near Folkestone, and Hay Cliff [TR 301 394] where it is approximately 58m thick. Its base is at the erosional contact beneath the Glauconitic Marl Member and its top is defined as the base of the overlying Hay Cliff Member of the Abbots Cliff Formation and placed at the “omission surface beneath the lowest ‘layer’ containing laminated structures”. The formation is undivided above the Glauconitic Marl Member. The formation is essentially equivalent to all of the Lower Chalk of the Traditional Scheme beneath the Jukes-Browne Bed 7. The ‘Cast Bed’ is present in the sequence (but not utilised to divide the sequence) and demonstrates that the Formation is equivalent to all of the West Melbury Marly Chalk Formation and the lower half if the Zig Zag Chalk Formation. Equivalent to the Mantelliceras mantelli Zone to the very basal Acanthoceras jukesbrownei Zone.

Glauconitic Marl Member

This is the basal member of the East Wear Bay Chalk Formation and is defined at Copt Point where it is about 5m thick. Its top is placed above a nodular bed equated to be that of Bed ‘h’ in Band 1 of Kennedy (1969). Equivalent to the Neostlingoceras carcitanense Subzone.

Abbots Cliff Chalk Formation

The formation (and its constituent members) is named from (and its stratotype at) the Abbots Cliff path [TR 268 385] where it is 22m thick. The Formation is divided into two members, the lower, Hay Cliff Member being overlain by the Capel-le-Ferne Member. The base is defined at the “omission surface beneath the lowest ‘layer’ containing laminated structures” and its top coincident with the base of the Plenus Marl Formation. Is equivalent to the Jukes-Browne Bed 7 and ‘White Bed’ (JB Bed 8) of the Traditional Scheme and to the upper half of the Zig Zag Chalk Formation. Equivalent to the Acanthoceras jukesbrownei Zone and Calycoceras guerangeri Zone

Hay Cliff Member

Indurated calcarenite equivalent to the Jukes-Browne Bed 7 of the Traditional Scheme, basal Acanthoceras jukesbrownei Zone. The base is defined at the “omission surface beneath the lowest ‘layer’ containing laminated structures”

Capel-le-Ferne Member

Bioturbated soft white Chalk equivalent to the ‘White Bed’ (JB Bed 8) of the Traditional Scheme and the Falling Sands ‘Member’ of Mortimore, Pomerol and Foord (1990) (or ‘Beds’ of Bristow, Mortimore and Wood, 1997). Topmost Acanthoceras jukesbrownei Zone and Calycoceras guerangeri Zone. The top defined as being coincident with the base of the Plenus Marl Formation at the sub-plenus erosion surface of Hill and Jukes-Browne (1886).

Plenus Marl Formation

This unit is directly equated to the Actinocamex plenus (now Praeactinocamax plenus) Subzone of Jefferies (1963) defined at Merstham [TQ 295 542] with the proposal that Shakespeare Cliff [TR 307 398] be designated its primary reference section. Here it is 2.67m thick. Base marked by the sub-plenus erosion surface with a top above the highest of the Plenus Marl ‘Beds’ of Jefferies (1963), the Foyle Marl of Mortimore (1986). It is equivalent to the Plenus Marls (Jukes-Browne Bed 9) of the Traditional Scheme and the Plenus Marls Member of the Holywell Nodular Chalk Formation in the new scheme. Equivalent to most of the Metoicoceras geslinianum Zone.

Dover Chalk Formation

This formation is divided into three constituent parts; the Shakespeare Cliff, Aycliffe and Akers Steps members, each containing and limited by named marker beds, with the stratotype designated as Akers Steps [TR 297 394] where 66.9m of beds are present. The base is taken at the base of the Melbourn Rock Beds and the top placed at the Crab Bay Marl. The formation is equivalent to the Bed 4 and Bed 5 units defined by Whitaker, Bristow and Hughes (1872) and most of the Middle Chalk of the Traditional Scheme. It is equivalent to the Holywell Nodular Chalk Member (but not the newly defined Formation of that name which includes the Plenus Marls Member), New Pit Chalk Formation and the lower part of the Lewes Nodular Chalk Formation. As defined the formation covers the Neocardioceras juddii to Terebratulina lata Zones.

Shakespeare Cliff Member

The Melbourn Rock Beds (c. 12m) form the lowest part of the Shakespeare Cliffe Member, which terminates upwards at the Warren Marl 1. The member being 26.5 m thick at its stratotype. The member is typically composed of beds of nodular and intraclastic chalk with spectacular concentrations of shell-detrital chalks containing Mytiloides within which the Round Down Marl is the only named marker. This member is equivalent to the ‘Grit Beds’ in the early literature and the Holywell Nodular Chalk Member of Bristow, Mortimore and Wood (1997).

Aycliff Member

This member is 17.5m thick at its stratotype and comprises essentially flintless white chalk with marl seam and weakly nodular chalk. The lower boundary is placed at the Warren Marl 1, which is the lateral equivalent of the New Pit Marl 1 in the Sussex succession, and the top is placed, rather unsatisfactorily, at the base of the first persistent flint up-sequence from the Maxton Marls. These marls being the lateral equivalent of the Glynde Marls in Sussex. Thus the member is essentially the equivalent of the New Pit Chalk Formation, as defined in Sussex, with the proviso that nodular chalks, characteristic of the Lewes Nodular Chalk Formation, are not encountered in Kent until only a few metres below the Langdon Bay Marls (the Southerham Marls of Sussex) higher still in the sequence. The member is entirely within the Terebratulina lata Zone.

Akers Steps Member

This unit is 17.5 m thick at its stratotype at Akers Steps and includes the inception of nodularity as seen in the North Downs successions. The first nodular beds appear approximately 5 m below the Langdon Bay Marls, which are equivalent to the Southerham Marls in the Sussex sequence, but the base of the member is placed lower (c. 15 m lower) at the first persistent flint below the Lydden Spout Flint. The top of the member is defined as the basal surface of the Crab Bay Marl that is the lateral equivalent of the Caburn Marl in the Sussex sequence. As the inception of nodularity indicates the base of the Lewes Nodular Chalk Formation in mapping terms, the lower part (c 10 m) of this member is to be considered as part of the New Pit Chalk Formation (but is the lateral equivalent of the Glynde Beds of the Sussex chalk). The upper part of the member is equivalent to the Caburn Beds of the Sussex Chalk. The member is entirely within the Terebratulina lata Zone.

Ramsgate Chalk Formation=

This formation is divided into three constituent parts, the St. Margarets, Broadstairs and Margate members each containing and limited by named marker beds. The stratotype is composite from the Dover to Thanet coast of Kent (see member entries) where about 120 m of beds are seen. The base is taken at the base of the Crab Bay Marl with the top limited by the sub-Palaeogene erosion surface. The formation is equivalent to the Bed 3, Bed 2 (Broadstairs Chalk) and Bed 1 (Margate Chalk) units defined by Whitaker, Bristow and Hughes (1872). The formation covers the highest beds of the Middle Chalk and all of the known Upper Chalk (in the North Downs) of the Traditional Scheme. It is equivalent to the middle and upper part of the Lewes Nodular Chalk Formation, the Seaford Chalk Formation and the lower part of the Newhaven Chalk Formation. As defined the formation covers the Terebratulina lata to Offaster pilula Zones.

St Margarets Member

This member is defined at the Langdon Stairs [TR 345 425] stratotype where 38.3 m of beds are encountered. The base is at the Crab Bay Marl (Caburn Marl) and its top placed at the East Cliff Marl 2 (Shoreham Marl 2). The member comprises nodular chalks with mineralised hardgrounds and regular strong nodular flint seams. It is equivalent to the ‘middle’ and ‘upper’ Lewes Nodular Chalk Formation

Broadstairs Member

Defined at four sites representing a composite stratotype at St Margarets Bay [TR 371 446], Kingsdown Rifle Range [TR 380 473], Pegwell Bay [TR 368 640] and Joss Bay [TR 398 702] where it has a combined thickness 58.5m. The base is placed at the East Cliff Marl 2 (Shoreham Marl 2) and its top at the upper surface of the Barrois Sponge Bed. As defined it is the direct equivalent of the Seaford Chalk Formation.

Margate Member

The member is defined at two sites which constitute the composite stratotype at White Ness [TR 396 710] and Foreness Point [TR 384 716] on the Isle of Thanet in Kent where 22.5m are preserved beneath the sub-Palaeogene erosion surface. The base is at the Barrois Sponge Bed. The member comprises soft white, marl-free, flint-poor chalk. Because of its lithological differences the Margate Member is retained in the new lithostratigraphical scheme within the Newhaven Chalk Formation that is thicker and stratigraphically more extensive (with significant marls) elsewhere.

Jarvis & Woodroof (1984)/Jarvis & Tocher (1987)

The sequence of Upper Cretaceous sediments in south-east Devon is lithologically distinct principally because of its presumed proximity to the basin margin and synsedimentary structural control. The succession is divided into two formations and six members with numerous named marker beds. In the 1984 paper the highest beds described are from the Beer Roads Flinty Chalk Member up to ‘Rowe’s Two Foot Band’ (Common Hill Marl, locally; or New Pit Marl 1 in the main basin). In the later (1987) paper the higher chalks describing the higher part of the Beer Roads Flinty Chalk Member and beds equated to the St. Margarets and Broadstairs Members of the North Downs (Robinson, 1986, see above) succession are described. The whole succession is however better understood by comparison to the Sussex sequence (see Mortimore, 1986; Mortimore, Wood and Gallois, 2001).

Beer Head Limestone Formation

The formation is divided into four members (but each not present everywhere) each defined by lithostratigraphical markers determined from stratotype sections between Branscombe [SY 204 882] and Seaton/White Cliff [SY 233 893] in Devon. Because of the marked lithological differences, condensation and omission in this marginal setting the term is utilised instead of the West Melbury Marly Chalk and Zig Zag Formations in BGS descriptive texts with the proviso that the highest, Pinnacles Member is demonstrably equivalent to the Plenus Marls Member and Melbourn Rock Member and therefore excluded from the Beer Head Limestone Formation. Thus the BGS usage accords with the Cenomanian Limestone as adjusted in Smith (1965) and Beds A1, A2 and B of Jukes-Browne and Hill (1903). It is equivalent to the Zig Zag and West Melbury Marly Chalk Formations or the Grey Chalk Subgroup.

Pounds Pool Sandy Limestone Member

The ‘stratotype’ for this member is at Pounds Pool Beach [SY 227 881] where it is 3.5 m thick. Its base is placed on the surface of the Small Cove Hardground of the Upper Greensand Formation with its top on the upper surface of the Weston Hardground. The member comprises yellowish brown very coarse calcareous sandstone passing up into indurated sandy bioclastic limestone. Biostratigraphically the member is reported to be in the Neostlingoceras carcitanensis Subzone, Mantelliceras mantelli Zone of the Lower Cenomanian. The member is equivalent to Bed A1 of Jukes-Browne and Hill (1903) and Smith (1965) and the lower part of the West Melbury Marly Chalk Formation.

Hooken Nodular Limestone Member

Named after Hooken Cliffs adjacent to the Beer Stone Adit [SY 219 879] where the member achieves its maximum thickness of 5 m. The base of the member is placed at the upper surface of the Weston Hardground and its top on the upper surface of the King’s Hole Hardground. It is composed of grey, shell-detrital rubbly limestone at various stages of induration. Inland the lateral equivalent of this member is termed the Wilmington Sand Facies (or member of some authors), which is composed of decalcified sand and sandy calcarenite overlain by highly fossiliferous sand with a chalky matrix (‘Grizzle’). Kennedy (1970) regarded this member as being of Mantelliceras saxbii Subzone Mantelliceras mantelli Zone age. There is a major hiatus between this and the succeeding member. The member is equivalent to Bed A2 of Jukes-Browne and Hill (1903) and Smith (1965) and the upper part of the West Melbury Marly Chalk Formation.

Little Beach Bioclastic Limestone Member

The member is thickest (1.75 m) at the Beer Stone Adit but seen to advantage in fallen blocks on Little Beach. It is a greatly condensed and complex bioclastic limestone sequence commencing with the ‘cavernous hardground’. The base is at the King’s Hole Hardground surface and its top at the Humble Point Hardground. Records show the member to be of Turrilites costatus Subzone (Acanthoceras rhotomagense Zone) to Acanthoceras jukesbrownei Zone with reworked material from older zones at the base and therefore is of Middle Cenomanian age. There is a major hiatus between this and the succeeding member. The member is equivalent to Bed B of Jukes-Browne and Hill (1903) and Smith (1965) and to much of the Zig Zag Chalk Formation.

Pinnacles Glauconitic Limestone Member

Named after the Pinnacles, which stand proud of the Hooken Cliffs, the member attains a maximum thickness there of 2.3 m. The member is confined between the top surfaces of the Humble Point Hardground and the Haven Cliff Hardground. Biostratigraphically the member contains a reworked fauna representing a part of the Middle and Upper Cenomanian and an indigenous fauna of Metoicoceras geslinianum Zone with Neocardioceras juddii Zone in the Haven Cliff Hardground. The member is equivalent to Bed C of Jukes-Browne and Hill (1903) and Smith (1965) and the basal Plenus Marls and Melbourn Rock members of the Holywell Nodular Chalk Formation.

Seaton Chalk Formation

The formation is divided into two members each defined by marker beds determined from the White Cliff stratotype between Beer and Seaton [SY 233 886]. The formation is equivalent to the Middle Chalk of the Traditional Scheme and the Holywell Nodular Chalk and New Pit Formations of the new scheme.

Connett’s Hole Nodular Chalk Member

Defined at White Cliff where 13.5 m of beds are preserved. The base is placed at the surface of the Haven Cliff Hardground and the top at the upper surface of the last nodular bed (the Flinty Hardground 5). The member is characterised by nodular chalk with hardgrounds, glauconitic and sandy at the base, and is poorly-flinty above the Branscombe Hardground. The Beer Stone, an important architectural freestone, is derived from a particularly pure, grey, fine-grained calcarenite lens in the lower part of the sequence. The obvious West Ebb Marl is and important marker in the sequence above the Beer Stone. There is a marked non-sequence beneath the Beer Roads Flinty Chalk Member over much of the outcrop that cuts out the highest beds down to the level of the Branscombe Hardground. This hardground itself cuts out the lower part of the sequence entirely, to the west, where it sits on the Pinnacles Member. Biostratigraphically it covers the Mytiloides spp Zone and is equivalent to the Holywell Nodular Chalk Formation.

Beer Roads Flinty Chalk Member

Named after the eastern side of Beer Beach [SY 232 892]. The base is at the surface of the Flinty Hardground 5 and the top at the inception of nodularity a metre or so below the Whitlands Marl on the Pinhay Cliffs (see Jarvis and Tocher, 1987). The member is characterised by soft white chalks with numerous flint and marl seams. Flint is less prominent to the east where the sequence becomes more like the New Pit Chalk Formation of Sussex. The distinct marker beds known as Rowe’s Two Foot and Four Foot bands are equated to the New Pt 1 and 2 marls in Sussex. Biostratigraphically the member is equivalent to the Terebratulina lata Zone and thus essentially the New Pit Chalk Formation.

Johansen & Surlyk (1990)

This paper dealing principally with the distribution of brachiopods within the upper Campanian and lower Maastrichtian chalk in Norfolk formalises, in lithostratigraphical terms and with some additions, the essentially biostratigraphical work of Peake and Hancock (1970); a paper which also describes the entire chalk sequence in the county (see also Brydone, 1908). In this earlier paper these chalks are referred to the ‘Zone of Belemnitella mucronata’, which they equate to the ‘Norwich Chalk’ of previous authors. This Norwich Chalk term is again used, informally but presumably implying formation status, by Mortimore, Wood and Gallois (2001), to cover all of the chalk of Norfolk above the Portsdown Chalk Formation. The Norwich Chalk (and the stratigraphically higher Trimmingham Chalk) is the lateral equivalent of the Rowe Chalk Formation, as defined, of the Northern Province.

The Basal mucronata Chalk ‘Member’

This is noted as the unit below their formally defined units and the name is taken from Peake and Hancock (1970). Its base is not formally defined but presumed to be at the base of the Zonal index belemnite. Peake and Hancock estimate it to be 50 feet (15.2m) of firm white chalk with frequent flints. Also known as the lower part of the pre-Weybourne Chalk.

Eaton Chalk Member

This overlies the ‘Basal mucronata chalk’ and is the oldest unit formally described. The base is ill defined within the Belemnitella mucronata sensu stricto Zone (at the base of the Echinocorys marginata approaching subglobosa ‘zone’, Peake and Hancock, 1961,1970). The member is also known as the upper part of the pre-Weybourne Chalk. Peake and Hancock estimate it to be 50 feet (15.2m) of soft chalks with irregularly scattered flints.

Weybourne Chalk Member

The base of this member is placed at the top of the sponge-bed hardground above Flint Z in the section at Weybourne Hope. Peake and Hancock estimate it to be 75 feet (22.8 m) of chalk with bands of strongly developed flints. It is mostly coincident to the Belemnitella woodi Zone of Christensen (1995, 1999).

Catton Sponge Bed

This is the topmost unit of the Weybourne Chalk Member. The base is marked by the incoming of sponges and its top is placed above the hardground. It varies between 0.3 m and a few metres in thickness and comprises one to three yellow stained hardgrounds and soft chalk with flint.

Beeston Chalk Member

The lower boundary placed at the surface above the Catton Sponge Bed whilst the upper boundary is poorly defined at a hardground on the coast at West Runton. The member comprises soft white chalk with irregular seams of large flints. Together with the Catton Sponge Bed below the beds cover most of the Belemnitella minor I Zone of Christensen (1995, 1999). Peake and Hancock estimate it to be 75 feet (22.8 m) thick.

Paramudra Chalk Member

The lower boundary is placed at the hardground described above but the top is ill defined in glacially disturbed masses but conventionally placed at the Overstrand Pyramidata Hardground. The member comprises soft white chalk with large vertical, cylindrical ‘Paramudra’ flints and repeated hardgrounds. It is equivalent for the most part with the Belemnitella minor II Zone of Christensen (1995, 1999). Peake and Hancock estimate it to be 75 feet (22.8 m) thick.

Sidestrand Chalk Member

Lower boundary placed at the Overstrand Pyramidata Hardground with the top at the hardground labelled ‘O’ in Peake and Hancock (1970, fig 7). The member includes the Sidestrand Chalk and Porosphaera Beds of Peake and Hancock (1970), which they equated with the Belemnella lanceolata ‘zone’, in the lowermost Maastrichtian. The member is between 10 and 12 m of white soft infrequently nodular chalk with regular flint seams. Forms part of the Belemnella lanceolata, B. psuedobtusa and B. obtusa Zones of Christensen (1999).

Trimingham Sponge Beds Member

Lower boundary at the top of the Sidestrand Chalk Member and a top at the marl band (the ‘greasy’ marl) labelled ‘G’ in Peake and Hancock (1970, fig 7). Equivalent to the ‘Sponge Beds’ of Brydone (1908) and Peake and Hancock (1970). The member is 2.9m of lithified chalk with green-coated pebbles, several erosion surfaces and four flint seams. The boundary between the Belemnella obtusa and B. sumensis Zones falls within this member.

Little Marl Point Chalk Member

The lower boundary is at the ‘greasy marl’ with the top at the base of the first soft grey chalk beds labelled ‘A’ by Peake and Hancock (1970, fig 7). This unit is equivalent to the ‘White Chalk with Ostrea lunata of Peake and Hancock (1970). Comprises 5 to 6 m of soft white chalk with four flint seams and two marls. Within the Belemnella sumensis Zone of Christensen (1999).

Beacon Hill Grey Chalk Member

Lower boundary bed ‘A’ by Peake and Hancock (1970, fig 7). Equivalent to the ‘Grey Beds’ of Peake and Hancock (1970). The member is at least 5 m thick and comprises grey chalk with five flint bands. Within the Belemnella sumensis Zone of Christensen (1999).