OR/14/009 Stratigraphy
| Woods, M A. 2014. Stratigraphical interpretations of Chalk Group macrosfossils from Sheet 254 (Henley-on-Thames) Autumn 2013. Nottingham, UK, British geological Survey. (OR/14/009) |
Localities from which Chalk group macrofossils were collected, and their stratigraphical interpretations, are described below.
| (1) | Old chalk pit 430 m ENE of Homer Farm, south of Nuffield, Oxfordshire. | ||
| Specimen nos: | WMD 16635 – 16639 | 1:10 000 SU68NE | |
| NGR: SU 66649 85892 | |||
The locality was also visited and collected in 2011 (WMD 15411 – 15433). The fauna includes the bivalves Platyceramus' and ?Volviceramus involutus (right valve fragment), and a cidarid echinoid spine fragment. The fauna occurs in soft and locally hard, nodular, sponge-bearing chalk.
Conclusion: White Chalk Subgroup, ?lower Seaford Chalk Formation; ?Coniacian, ?lower M. coranguinum Zone.
A fauna suggestive of the mid to upper Seaford Chalk Formation was collected from a nearby locality by MAW in 2011 [SU 66125 85756].
| (2) | Old chalk pit adjacent to South Oxfordshire Way, 360 m NW of Watlington Hill farm, near Christmas Common, Oxfordshire. | ||
| Specimen nos: | WMD 16640 – 16644 | 1:10 000 SU79SW | |
| NGR: SU 71190 93781 | |||
The fauna includes a cidarid echinoid spine fragment, the sponge Porosphaera and the bivalve Cremnoceramus?. The succession from which the material was collected comprises bands of hard, nodular, sponge-bearing chalk, and horizons of softer chalk, with carious nodular flints.
Conclusion: White Chalk Subgroup, ?upper Lewes Nodular Chalk; ?Coniacian, ?upper M. cortestudinarium Zone.
| (3) | Old chalk pit SW of Hammond's Wood and c. 200 m North of A4074, just north of Woodcote, Oxfordshire. | ||
| Specimen nos: | WMD 16645 – 16654; 16673 – 16678; 16826 – 16828 | ||
| 1:10 000 SU68SW | |||
| NGR: SU 64389 82952 | |||
The fauna is as follows:
| Bivalvia: | ?Cremnoceramus denselamellatus |
| Cremnoceramus' ex gr. waltersdorfensis | |
| Echinoidea: | Micraster? (test fragments) |
| ?Plesiocorys placenta | |
| Plesiocorys? (test fragments) | |
| Ichnofossils: | Zoophycos (in marl preservation) |
Most of the material was collected from distinctly soft chalk with Zoophycos. The section also includes patchily hard, iron-stained, sponge-rich chalk, thin, anastomosing sheet flints, highly carious nodular flints and hollow-centred tubular flints.
Interpretation: The association of the above fauna with soft chalk containing marl-preserved Zoophycos suggests the equivalent of the Cuilfail Zoophycos in the upper P. (S.) plana Zone.
Conclusion: White Chalk Subgroup, mid Lewes Nodular Chalk Formation; late Turonian, upper P. (S.) plana Zone.
| (4) | Old chalk pit near Hammond's End, just north of road to Checkendon, and c. 100 m NW of Wheeler's Farm, near Woodcote, Oxfordshire. | ||
| Specimen nos: | WMD 16655 – 16659 | 1:10 000 SU68SE | |
| NGR: SU 65495 83854 | |||
The fauna, includes a shell fragment of the bivalve Cremnoceramus? and the echinoid Micraster sp. (in patchily hard chalk).
Conclusion: White Chalk Subgroup, ?upper Lewes Nodular Chalk; ?Coniacian, ?M.' cortestudinarium Zone.
| (5) | Old chalk pit 270 m WNW of Wheeler's Farm, north of Woodcote, Oxfordshire. | ||
| Specimen nos: | WMD 16660 – 16672 | 1:10 000 SU68SE | |
| NGR: SU 65287 83861 | |||
The fauna comprises shell fragments of the bivalve Cremnoceramus, including C. crassus.
Interpretation: Cremnoceramus crassus is typical of the M. cortestudinarium Zone, and the higher part of the Lewes Nodular Chalk can be inferred. However, the succession from which the material was collected is not typical of the Lewes Nodular Chalk, comprising soft, smooth- textured chalk with large nodular and semitabular flints.
Conclusion: White Chalk Subgroup, equivalent to upper Lewes Nodular Chalk Formation; Coniacian, M. cortestudinarium Zone.
| (6) | Old chalk pit on Nuffield Hill, on north side of road, 500 m WNW of Nuffield church, Oxfordshire. | ||
| Specimen nos: | WMD 16679 – 16694 | 1:10 000 SU68NE | |
| NGR: SU 66367 87634 | |||
The fauna comprises the oyster Pycnodonte vesiculare, common shell fragments of the inoceramid bivalve Platyceramus and the echinoid Micraster sp. (fragment). The material was collected from a c. 1 m interval of soft, flinty, locally very sponge-rich chalk.
Interpretation: Platyceramus' occurs at and above the M. coranguinum Zone. Field relationships for nearby localities favour the M. coranguinum Zone (see (23) to (26) below), and the Seaford Chalk Formation might be inferred.
Conclusion: White Chalk Subgroup, Seaford Chalk Formation; ?Coniacian, M. coranguinum Zone.
| SE face of large old quarry now used for storage of rubbish skips. 250 m SE of Potter's Farm, SE of Ewelme, Oxfordshire. | |||
| Specimen nos: | WMD 16695 – 16702 | 1:10 000 SU68NE | |
| NGR: SU 65600 89175 | |||
The material was collected from a c. 5 m section comprising weakly nodular chalk with marl seams in the lower part, passing upwards into strongly nodular chalk capped by glauconitised hardgrounds (Fig. 1). Horizon details refere to Fig. 1.
| Horizon: | I. cuvieri Horizon |
| Brachiopoda: | Terebratulina lata |
| Bivalvia: | Inoceramus cuvieri |
| Horizon: | Fognam Marl |
| Foramninifera: | Labyrinthydoma'' |
| Bivalvia: | Inoceramus cuvieri |
There is a sharp downward change below the Fognam Marl to distinctly less nodular chalk.
Interpretation: The presence of Labyrinthidoma confirms the identity of the Fognam Marl (= Southerham Marl 1 of Mortimore, 1986) and the fauna is characteristic of the upper T. lata Zone. Lithologically, the section largely equates with the basal Lewes Nodular Chalk Formation, although the weakly nodular chalk with marl seams in the lower part of the section is probably coeval with upper New Pit Chalk seen elsewhere in the Chilterns. The hardgrounds at the top of the section represent the lower part of the Chalk Rock Member.
Conclusion: White Chalk Subgroup, ?topmost New Pit Chalk Formation and basal Lewes Nodular Chalk Formation (including Chalk Rock Member); Turonian, upper T. lata Zone.
| (8) | Burrow brash on west side of footpath (Grindon Lane), c. 560 m NNE of Potter's Farm, near Ewelme, Oxfordshire. | ||
| Specimen nos: | WMD 16703 – 16708 | 1:10 000 SU69SE | |
| NGR: SU 65651 90058 | |||
The material comprises hard, shelly chalk with the bivalve Mytiloides, including Mytiloides mytiloides.
Conclusion: White Chalk Subgroup, Holywell Nodular Chalk Formation; lower Turonian, Mytiloides spp. Zone.
| (9) | Brash from pipe trench dug along field margins adjacent to Swan's Way, Grindon Lane, and un-named track running E-W on southern boundary of field; c. 600 m NNE of Potter's Farm, near Ewelme, Oxfordshire. | ||
| Specimen nos: WMD 16709 – 16714 | 1:10 000 SU69SE | ||
| NGR: SU 65800 90000 | |||
The fauna is a generalised collection from the extensive spoil seen at this locality. Subsequent collections (see (10) to (12) below) are more localised. The material includes a thin-shelled inoceramid and the echinoid Cardiaster sp.
Conclusion: None possible.
| (10) | Brash from pipe trench dug along field margins adjacent to Swan's Way, Grindon Lane, and un-named track running E-W on southern boundary of field; c. 600 m NNE of Potter's Farm, near Ewelme, Oxfordshire. | ||
| Specimen nos: | WMD 16715 – 16717 | 1:10 000 SU68NE | |
| NGR: SU 65703 89932 | |||
The fauna includes the brachiopod Terebratulina lata and an indeterminate inoceramid shell fragment.
Interpretation: Field relationships wirh material collected at (8) (above) suggest assignment to the basal T. lata Zone, and the basal New Pit Chalk Formation might be inferred.
Conclusion: White Chalk Subgroup, basal New Pit Chalk Formation; Turonian, basal T. lata Zone.
| (11) | Brash from pipe trench dug along field margins adjacent to Swan's Way, Grindon Lane, and un-named track running E-W on southern boundary of field; c. 600 m NNE of Potter's Farm, near Ewelme, Oxfordshire. | ||
| Specimen nos: | WMD 16718 – 16721 | 1:10 000 SU69SE | |
| NGR: SU 66265 90504 | |||
The material comprises chalk with shell fragments of the inoceramid bivalve Mytiloides.
Interpretation: The fauna, and field relationships with (8) and (10) above, suggest assignment to the Mytiloides spp. Zone and the Holywell Nodular Chalk Formation.
Conclusion: White Chalk Subgroup, Holywell Nodular Chalk Formation; lower Turonian,
| (12) | Brash from pipe trench dug along field margins adjacent to Swan's Way, Grindon Lane, and un-named track running E-W on southern boundary of field; c. 600 m NNE of Potter's Farm, near Ewelme, Oxfordshire. | ||
| Specimen nos: | WMD 16722 – 16724 | 1:10 000 SU68NE | |
| NGR: SU 65837 89860 | |||
The fauna includes the inoceramid bivalve Mytiloides ex gr. hercynicus – subhercynicus.
Conclusion: White Chalk Subgroup, basal New Pit Chalk Formation; Turonian, basal T. lata Zone.
| (13) | Trench and spoil for new house development at Well Place, Oxfordshire (Locality 1). | ||
| Specimen nos: | WMD 16725 – 16728 | 1:10 000 SU68NE | |
| NGR: SU 65578 85631 | |||
The fauna is as follows:
| Bivalvia: | Cremnoceramus waltersdorfensis hannoverensis? |
| Cremnoceramus? (fragment) | |
| Inoceramus lusatiae | |
| Inoceramus sp. |
Conclusion: White Chalk Subgroup, middle Lewes Nodular Chalk Formation; early Coniacian, basal M. cortestudinarium Zone. The material probably represents a level at or slightly above the Navigation Marls of Sussex.
| (14) | Trench and spoil for new house development at Well Place, Oxfordshire (Locality 2). | ||
| Specimen nos: | WMD 16729 – 16734 | 1:10 000 SU68NE | |
| NGR: 65554 85619 | |||
The fauna includes the bivalve Cremnoceramus waltersdorfensis hannoverensis? and the echinoid Micraster sp.
Conclusion: As for (13) above.
| (15) | Trench and spoil for new house development at Well Place, Oxfordshire (Locality 3). | ||
| Specimen no.: | WMD 16735 | 1:10 000 SU68NE | |
| NGR: SU 65536 85616 | |||
The specimen is the echinoid Micraster (specifically indeterminate), glauconitised and associated with a hardground.
Interpretation: The hardground is inferred to represent the highest unit (Hitch Wood Hardground) of the Chalk Rock Member. In more basinal settings, the so-called 'large forms' of Micraster leskei (M. leskei magna) are associated with a marl (Lewes Marl) that overlies strongly nodular chalks that are coeval with the Hitch Wood Hardground. The lowermost hardground of the inferred Chalk Rock was seen at [SU 65513 85602] (Locality 4), faulted, with a downthrow of c. 0.4 m into the hillside.
Conclusion: White Chalk Subgroup, lower Lewes Nodular Chalk Formation; late Turonian, P. (S.) plana Zone.
| (16) | Trench and spoil for new house development at Well Place, Oxfordshire (Locality 5). | ||
| Specimen no.: | WMD 16736 | 1:10 000 SU68NE | |
| NGR: SU 65509 85599 | |||
The material, collected from a plastic-textured marl, includes the brachiopod Terebratulina lata and questionable specimens of the giant agglutinating foraminifer Labyrinthydoma.
Interpretation: The above fauna, lithology and field relationships strongly suggest that the marl seam is the Fognam Marl (= Southerham Marl 1 of Mortimore 1986) in the upper T. lata Zone, and the basal Lewes Nodular Chalk might be inferred.
Conclusion: White Chalk Subgroup, basal Lewes Nodular Chalk; upper T. lata Zone, basal Lewes Nodular Chalk Formation.
| (17) | Trench and spoil for new house development at Well Place, Oxfordshire (Locality 6). | ||
| Specimen nos: | WMD 16737 – 16739 | 1:10 000 SU68NE | |
| NGR: SU 65504 85597 |
The material comprises specimens of the inoceramid bivalve Inoceramus cuvieri, collected from the succession just below the inferred Fognam Marl at (16) (above).
Interpretation: The record of common Inoceramus cuvieri at this locality and also (7) (above) is notable. At some localities a hardground (Ogbourne Hardground) is present below the Fognam Marl, and was stated by Gale (1996) to eliminate the higher part of the New Pit Chalk containing the acme of I. cuvieri. Slightly lower in the succession at this locality, at [SU 65492 85583], is a thick (0.17 m), grey marl associated with typical New Pit Chalk.
Conclusion: White Chalk Subgroup, basal Lewes Nodular Chalk Formation; Turonian, uppermost T. lata Zone.
| (18) | Tree roots exposure of Chalk adjacent to track in Icknieldbank Plantation, east of Ewelme, Oxfordshire. | ||
| Specimen nos: | WMD 16740 – 16744 | 1:10 000 SU69SE | |
| NGR: SU 66870 91501 | |||
The material comprises specimens of the bivalve Inoceramus cuvieri?.
Conclusion: White Chalk Subgroup, ?New Pit Chalk Formation; ?Turonian, ?T. lata Zone.
| (19) | Overgrown exposure of Chalk adjacent to footpath on Watlington Hill, c. 200 m WSW of car park on Watlington Hill, Oxfordshire. | ||
| Specimen nos: | WMD 16745 – 16747 | 1:10 000 SU79SW | |
| NGR: SU 70771 93456 | |||
The fauna is indeterminate.
Conclusion: None possible.
| (20) | Small, overgrown quarry on Watlington Hill adjacent to footpath, c. 670 m along path from SW edge of National Trust land (at SU 70010 93199), near Watlington, Oxfordshire | ||
| Specimen nos: | WMD 16748 – 16762 | 1:10 000 SU79SW | |
| NGR: SU 70644 93430 | |||
The fauna, collected from patchily hard and soft chalk with nodular and thin sheet flints, is as follows:
| Bryozoa: | bryozoan | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Bivalvia: | Cremnoceramus? (shell fragments) | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| ?C. deformis erectus | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Echinoidea: | indeterminate test fragment | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| cidarid spine
Conclusion: White Chalk Subgroup, ?upper Lewes Nodular Chalk Formation; ?Coniacian, ?M. cortestudinarium Zone. The presence of thin sheet flints is consistent with this speculative conclusion.
The fauna is as follows:
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