Notes on the high-level (?marine), late Anglian Woolpit Beds, Suffolk

NOTES ON THE HIGH-LEVEL, (? MARINE), LATE-ANGLIAN WOOLPIT BEDS, SUFFOLK

C. R.

BRISTOW

and Miss D . M .

GREGORY

'Brickearth' at Woolpit has been worked since at least the 16th Century (Whitaker, Bennett and Blake, 1881; Northeast, 1972) and was the source for the locally-famous bricks known as Woolpit or Suffolk Whites. Düring 1978 this area was re-surveyed by one of us (CRB) at the six-inch-to-the-mile scale (1:10 560 Sheet T L 96SE). This survey showed that the 'brickearth' overlies chalky Boulder Clay, and is locally overlain by Glacial Sand and Gravel and/or chalky Boulder Clay. The lower Boulder Clay is part of the extensive sheet of Anglian age which forms the plateau area of much of East Anglia. At Sicklesmere, some 11 km west of Woolpit, this Boulder Clay is overlain by Hoxnian deposits (Turner, 1973). In 1978 two I G S continuous flight auger holes' (Woolpit 1 & 2) were drilled into the 'brickearth'. Samples from these boreholes yielded a sparse marine Pleistocene foraminiferal fauna. This unanticipated result led to a third borehole (Woolpit 3) being drilled by taking continuous U4s ; , in order to obtain better, uncontaminated samples. In view of the distinct lithology and fauna it is here proposed to name the 'brickearth' at Woolpit as the Woolpit Beds. The Woolpit 3 borehole not only penetrated the füll thickness of the Woolpit Beds, but also continued through the Crag. The foraminifera recovered from the Crag are also listed in the faunal chart (Table 1) to enable comparison to be made between the faunas from the Woolpit Beds and the Crag, and in particular, to see whether the former could have been derived from the latter.

Stratigraphy The 'brickearth' occupies a depression in the Boulder Clay surface of approximately 1 km diameter. The deposits are at their highest around the margin where they attain a maximum height of 60 m O D . Numerous pits have been opened in the 'brickearth'; those at the margin appear to have stripped off the brickearth completely, leaving hollows now floored and flanked by chalky Boulder Clay. The largest pit [TL 982 622], and the last one 1 C o n t i n u o u s flight a u g e r — t h i s is in reality a giant screw which can be used in two d i f f e r e n t ways to obtain samples: a. by driiling into the g r o u n d without withdrawing the bit, in which case the s a m p l e travels up the a u g e r flight to the surface. This is a very quick driiling m e t h o d , but the resultant d e p t h s of the s a m p l e s a r e not k n o w n with precision. b. t h e a u g e r is drilled into the g r o u n d to fill the flights with sample and t h e n w i t h d r a w n a n d the s a m p l e r e m o v e d ; the process is t h e n r e p e a t e d . This m e t h o d gives m u c h b e t t e r control of sample d e p t h , but the driiling process is much slower as t h e r e is m u c h coupling and uncoupling of driiling stems.

2 U 4 — t h i s is the Standard t e r m for an u n d i s t u r b e d s a m p l e of 4 inches diam. S a m p l e s are o b t a i n e d by this m e t h o d by banging the U 4 tube into the Sediment until filled; it is w i t h d r a w n and the s a m p l e e x t r u d e d f r o m the U 4 t u b e .

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NOTES O N T H E H I G H - L E V E L ( ? M A R I N E ) , LATE A N G L I A N WOOLPIT BEDS

31 1

to close (c. 1940), lies on the south side of the old main road to Woolpit. some 800 m ESE of Woolpit Church. The southern part of the pit has now been infilled, but poor exposures in the weathered uppermost 2 m of buff, laminated silts, fine-grained sands, silty clays, and clayey siltscan still be seen on the western side of the pit. In 1978 two IGS continuous flight-auger holes were drilled in the northern part of the pit. The Woolpit 1 Borehole (TL 96 SE/131) [9814 6228] failed to bottom the silts and the silty clays at a depth of 19.5m. Woolpit 2 Borehole (TL 96 SE/132) [9844 6217] proved 18.0 m of silts and silty clays above stiff bluish black chalky Boulder Clay. The boreholes passed from buff and yellow weathered material into unweathered bluish black deposits at depths of 15 m and 7 m in each borehole respectively. The generalised sequence encountered in the Woolpit 3 Borehole (TL 96SE/158) [9820 6238] is as follows: Thickness m 1.55

MadeGround Woolpit Beds Clay and clayey sand, yellowish brown, sandy. with a fine-grained sand at the base.

Depth m 1.55

7.65

9.20

Clay, grey and yellowish grey and silty laminated clay with scattered small chalk grains (up to 3 mm). bioturbated.

0.85

10.05

Silt, clayey pale grey with small chalk grains, bioturbated and laminated in part.

0.35

10.40

Silt and sand, fine-grained, locally laminated pale grey.

1.04

11.44

Clay, silty with scattered chalk grains, bioturbated dark grey.

0.19

11.63

Silt, clayey with fine-grained quartz sand and some fine-grained chalk, laminated.

0.27

11.90

Clay, silty, scattered chalk pebbles up to 8 mm, pale to medium grey.

0.32

12.22

Sand, fine-grained, buff, micaceous.

0.28

12.50

Clay, silty, medium grey

0.12

12.62

Sand, fine-grained, buff, micaceous, locally crossbedded, bioturbated.

3.33

15.95

Breccia, clay pale to medium grey with angular flint chips up to 7 mm; chalk pebbles up to 1 cm. Sharp junction with bed below.

0.05

16.00

Sand, very fine-grained, silty; scattered chalk pebbles up to 2 cm, some angular flint chips.

0.40

16.40

Clay and silt, dark grey: chalk pebbles and flint chips up to 2 cm: scattered rounded quartzite pebbles up to 1 cm.

0.20

16.60

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Clay, silty with fine-grained sand partings.

0.03

16.63

Sand, fine-grained, finely laminated, buff-grey.

2.27

18.90

Silt and clay with chalk pebbles, rounded quartzites, (?Jurassic) oyster fragment with a d h e r e n t worm tubes.

0.10

19.00

C o r e loss.

0.70

19.70

Sand, fine-grained, buff-grey, h o m o g e n e o u s .

1.70

21.40

C o r e loss.

2.20

23.60

Sand, fine-grained with a little chalk.

1.20

24.80

c. 0.40

c.25.20

3.70

28.90

1.60

30.50

Boulder Clay Clay, silty dark olive grey with chalk pebbles up t o i cm. " ' Crag Coarse-grained shelly sand (see Bristow, 1983).

U p p e r Chalk Soft white chalk.

T h e intervals 16.40-16.63 m and 18.90-19.00 m appear to be typical chalky Boulder Clay. It thus appears as if the Woolpit Beds have a gradational contact with the underlying Boulder Clay.

W h i t a k e r , Bennett and Blake (1881, p. 13) refer to Boulder Clay above the •brickearth' in a pit 'half a mile east of the Church' [?983 625] and in "the other brickyards'. In the pit at C r a n m o r e Bridge [?9905 6235] the above authors recorded 1.5 m of Boulder Clay of a light marly character containing many chalk stones, resting on 1.2 m of dark bluish grey clay which in turn overlies 3.0 m of laminated buff-coloured brickearth [Woolpit Beds]. At a third pit at Crossways, 'half a mile north-east of Woolpit' [79790 6285] they recorded 3.6 m of brown brickearth resting on 0.6 m of black earth consisting of much c a r b o n a c e o u s m a t t e r , leaves, pieces of wood etc, together with pieces of bones (including Bos and Cervus), which in turn overlay a shell marl containing Planorbis, Lymnaea and Valvata piscinalis (see p. 313 for comment).

U p p e r Glacial Sand and Gravel of uncertain age appears to overlie the Woolpit Beds near the C r a n m o r e Bridge pit [around 9905 6235], near a n o t h e r old pit [9885 6275] 1.5 km east-north-east of Woolpit Church and also at a n o t h e r nearby pit [9910 6245], now backfilled. Fine-grained sand overlies the brickearth at the Crossways pit. Elsewhere the relationship of the Woolpit Beds to the adjacent strata is less certain.

Palaeontology Samples were collected f r o m the unweathered material of all three boreholes and were submitted for micropalaeontological analysis. They all proved to be barren of dinoflagellates and ostracods, but did yield a n u m b e r of foraminifera. Additionally, f r a g m e n t s of Baianus, crinoid columnals, bryozoa,

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Nat. Soc.

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313

gastropods and bivalves (including a mytilacean fragment) of uncertain origin (i.e. derived or in situ) were recovered in samples from the Woolpit Beds of Woolpit 3. The foraminifera from the Woolpit Beds of the three boreholes, together with those from the Crag of Woolpit 3 are set out in the following chart (Table 1).

It is difficult to decide whether the fauna is in situ or derived. The distribution of the foraminifera in Table 1 should suggest that whilst the isolated occurrences of some specimens in the Woolpit Beds (e.g. Elphidiella hannai and Cibicides lobatulus) are probably derived from the Crag in whieh they are more abundant, the presence of other species e.g. Protelphidium anglicum and P. cf. orbiculare) in the Woolpit Beds and their absence from the Crag indicates that even though they may still be derived. the Crag was not their source. Indeed the dominance of Elphidium clavatum and the Virtual absence of Elphidiella hannai in the Woolpit Beds set this fauna apart from the Crag faunas recorded at Ludham (Funnell, 1961), Easton Bavents (Funnell and West. 1962) and Bramerton (Funnell, Norton and West. 1979).

Many other post-Anglian deposits including Glacial Silts from the Bury St. Edmunds area have been examined by the Palaeontology Unit of the IGS. Where fossiliferous, the indigenous fauna consists of freshwater molluscs and ostracods. No Pleistocene foraminifera have ever been found, and it therefore seems unlikely that the above fauna has been derived from the Boulder Clay, although there are many derived Jurassic and Cretaceous foraminifera associated with the Woolpit Beds fauna. Gregory (1922; reproduced in Boswell, 1929), however, recorded Pleistocene foraminifera from the Boulder Clay of the Ballingdon Grove Brick Pit, Sudbury, and concluded that the Boulder Clay had formed by the melting of ice in sea water. The Ballingdon Grove Pit is of interest as here 'brickearth', locally overlain and underlain by chalky Boulder Clay, was formerly exposed (see Boswell 1929 Fig. 11).

It is possible that the Woolpit Beds do represent a local deposit of ice-transported Pleistocene sea-bed material deposited in a lake formed in a hollow on the Boulder Clay surface. An alternative explanation is that these beds represent in situ marine deposits, but this seems unlikely. The present day height (60 m OD) and the isolated position of the Woolpit Beds 35 km from the nearest part of the present day coast, and 45 km from the nearest marine Middle Pleistocene deposits in the Nar Valley (maximum height of 30 m OD) to the north-west, are difficult to explain. If the former hypothesis of transported and redeposited Pleistocene sea-bed material is correct then its contained fauna would be approximately contemporaneous with its deposition; it should not differ significantly in age from that deposited under truly marine late glacial or interstadial conditions. If it is an in situ or neo-contemporaneous fauna the presence of Elphidium clavatum is indicative of cold, shallow water conditions, although Protelphidium anglicum indicates some moderating influence at least at this horizon.

The presence of fresh-water molluscs and mammalian bones in the Crossways pit is not incompatible with our conclusion that the Woolpit Beds contain a marine fauna since the earlier collecting came from near-surface deposits at the margin of the basin (possibly from a separate deposit to the

Trans. Suffolk Nat. Soc. 18 part 4.

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Trans. Suffolk Nat. Soc. 18 part 4.

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Suffolk Natural History, Vol. 18, Part 4

Woolpit Beds), whereas our faunas came from the lower part of boreholes drilled in the centre of the basin and presumably stratigraphically lower.

Conclusions The Woolpit Bedsoceur over an areaof approximately 1km. diameter. From the evidence of Woolpit 3 Borehole there appears to be an intermittent upward passage of the Woolpit Beds from the underlying Boulder Clay, with the two lithologies interbedded over the 8-m interval between the depths of 15.95 and 24.8 m. At nearby localities, Boulder Clay has been recorded above the brickearth, and locally Upper Glacial Sand and Gravel spreads over both the Upper Boulder Clay and the Woolpit Beds. The fauna, if in situ, indicates deposition mainly under cold shallow-water conditions with some indication of deposition under slightly warmer conditions in the upper part of the deposits. The present topographical position of the Woolpit Beds is difficult to explain. We feel that at the moment we have insufficient evidence to put forward a viable hypothesis to account for this distribution, but nevertheless wish to record our preliminary findings of this interesting deposit.

The authors are most grateful to Mr. O. Baker, the owner of the former brickworks, for his ready Cooperation during the drilling programme without which this study would not have been possible.

This paper is published by permission of the Director, Institute of Geological Sciences ( N . E . R . C . ) .

References Boswell, P. G . H. (1929). The Geology of the country around Sudbury (Suffolk). Mem. Geol. Surv. G. B. Bristow, C. R. (1983). The stratigraphy and structure of the Crag of mid-Suffolk. Proc. Geol. Am., 19, 1.

Funnell, B. M. (1961). The Palaeogene and early Pleistocene of Norfolk.

Trans. Norfolk and Norwich Nat. Soc.. 19, 340.

Funneil, B. M. & West, R. G . (1962). The early Pleistocene of Easton Bavents, Suffolk. Q. Jnlgeol. Soc. Lond.,\\\, 125.

Funneil, B. M., Norton, P. E. P. & West, R. G. (1979). The crag at Bramerton, near Norwich, Norfolk. Phil. Trans. Roy. Soc. (B.), 287, 489.

Gregory, J. W. (1922). Evolution of the Essex rivers and of the Lower Thames. Colchester: Benham and Co. Northeast, P. (1972). Woolpit Brick. Ms Document (4 pp). Local Studies Collection. Suffolk Record Office, Bury St. Edmunds.

T u r n e r , C. (1973). Eastern England in Mitchell, G . F. et al. A correlation of Quaternary deposits in the British Isles. Geol. Soc. Lond., Special Report No. 4, 8.

Whitaker, W., Bennett, F. J. & Blake, J. H. (1881). Geology of the Neighbourhood of Stowmarket. Mem. Geol. Surv. G. B. Trans. Suffolk Nat. Soc. 18 part 4.

NOTES ON THE HIGH-LEVEL (?MARINE), LATE ANGLIAN WOOLPIT BEDS 317

C. R. Bristow, Institute of Geological Sciences, St. Just, 30 Pennsylvania Rd..

Exeter EX4 6BX D.M. Gregory, Institute of Geological Sciences, Ring Road, Haiton, Leeds LS15 8TQ

Trans. Suffolk Nat. Soc. 18 part4.