Proceedings of the Geologists’ Association 122 (2011) 514–523

Field Meeting to the Bawdsey Peninsula, Suffolk, England, 22nd May 2010,to examine London Clay, Coralline Crag and Red Crag depositsLeaders: Roger Dixon and Bob Markham

Roger Dixon *

The White House, 7 Chapel Street, Woodbridge, Suffolk IP12 4NF, United Kingdom

A R T I C L E I N F O

Article history:

Received 27 July 2010

Received in revised form 8 February 2011

Accepted 11 February 2011

Available online 16 March 2011

Keywords:

Pliocene

Coralline Crag

Red Crag

Rockhall Wood

‘Pliocene Forest’

Mollusc faunas

A B S T R A C T

A one-day Geologists’ Association field excursion to the Bawdsey Peninsula in coastal Suffolk is

described, with a guided tour of ‘The Pliocene Island’ at Sutton Knoll and visits to examine coastal

erosion, the London Clay and Red Crag at Bawdsey East Lane, and the Red Crag at Alderton and Ramsholt.

The depositional environments indicated by the Crag sediments and faunas are discussed, and non-

derived Red Crag mollusc faunas at Sutton and sand-wave mollusc assemblages from Ramsholt are

described.

� 2011 The Geologists’ Association. Published by Elsevier Ltd. All rights reserved.

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journa l homepage: www.e lsev ier .com/ locate /pgeola

1. Introduction

With the barometer rising, temperatures soaring into the 20sand not a breath of wind, 26 members of the Geologists’Association and the GeoSuffolk team met on a gloriously sunnyday for an excursion to the Bawdsey Peninsula in coastal Suffolk.The Geologists’ Association last visited the area in April 2004 for along week-end (Dixon, 2005) – this was a visit to see just some ofthe locations not seen then (Fig. 1).

The stratigraphy seen during the day consisted of: EoceneLondon Clay underlies the area and is unconformably overlain byoutliers of mid-Pliocene Coralline Crag. Late Pliocene Red Cragunconformably overlies both these deposits, and there is evidenceof the later Early and early Middle Pleistocene proto-ThamesKesgrave Sands and Gravels.

After a short briefing at Sutton Heath (National Grid ReferenceTM 306475), the group drove the short distance to Sutton Knoll.Here was held a ‘mass opening’ of the new enclosure, funded by theCurry Fund of the Geologists’ Association, for an expanded‘Pliocene Forest’. The group held on to a length of red ribbon,which was snipped by Curry Fund committee member David Bone,who spoke about the work of the Curry Fund (Fig. 2).

* Corresponding author.

E-mail address: redcragrocdoc@btinternet.com.

0016-7878/$ – see front matter � 2011 The Geologists’ Association. Published by Else

doi:10.1016/j.pgeola.2011.02.002

2. Locality 1: Sutton Knoll [TM 305440]

This famous site, which includes Rockhall Wood Site of SpecialScientific Interest (SSSI), has been studied for over 170 years, longknown as an island of Coralline Crag during Red Crag sea times,with its Coralline Crag cliffs and boulders ‘buried’ in Red Crag. Theclassic description was by Prestwich (1871a,b), some of the figuresof which were reproduced by Boswell (1928), but Balson (1999)gives an excellent recent description and discussion. Other recentdescriptions include Balson and Long (1988) and Balson et al.(1990, 1993) describe the stratigraphy of the Coralline Crag as awhole. Dixon (2006, 2007, 2009a) describes recent developments.

The locality has frequently been visited by field groups and hasoften been used for educational purposes, including undergraduateproject work. English Nature (now Natural England) cleared facesin 2006 as part of their ‘Facelift’ programme and members of thelocal GeoSuffolk group have been actively maintaining anddeveloping sections. Furthermore, new research by GeoSuffolkmembers is currently underway to help interpret the site from amore modern perspective (Fig. 3).

2.1. Coralline Crag

Suffolk’s Pliocene Coralline Crag, deposited approximately 3.75million years ago, outcrops as a 12 km inlier ridge running from thenorth of Aldeburgh south-westwards to the Butley River, withfurther small outliers, including Sutton, to the southwest, and rests

vier Ltd. All rights reserved.

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Fig. 1. Location map of the sites visited during the Geologists’ Association field

excursion on May 22nd, 2010. 1, Sutton Knoll; 2, Bawdsey, East Lane; 3, Alderton

House Pit; 4, Tarrant’s Pit.

R. Dixon / Proceedings of the Geologists’ Association 122 (2011) 514–523 515

unconformably on the London Clay (see Fig. 4). The bioclasticsands, about 20 m thick, can be broadly divided into threesedimentary and faunal units, two of which outcrop at Sutton: alower Ramsholt Member and an overlying Sudbourne Member

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Fig. 2. David Bone cutting the ribbon to open the new exten

(seen also at Richmond Farm (TM 413493) and Crag Farm (TM428523) SSSIs and elsewhere). The beds are possibly best knownfor their bryozoan fossils (‘Corallines’) and the common occurrenceof one of Britain’s largest fossil brachiopods, ‘Terebratula grandis’.Over 300 species of mollusc have been recorded from these beds bySearles Wood and others, many extant forms having ‘southern’ orLusitanic distributions, and suggest summer water temperaturesapproaching 17–20 8C and winter temperatures of 6–9 8C. Howev-er, ‘mixed signals’ are given by different faunal elements (Williamset al., 2009) and there is no consensus of opinion. A useful overviewand discussion of Neogene correlation and environmental inter-pretation, with particular reference to the role of ostracods is givenby Wood (2009).

The group first examined the lower beds of the SudbourneMember at the North Face. This 50 m long, 3 m high section on thenorthern edge of the Knoll was cleared by GeoSuffolk members in2008/2009. The beds contain small and medium scale sand-waveswith mud drapes and laminations, possibly of tidal origin, andabundant infaunal burrow types, including those of worms,crustaceans and spatangoid echinoids, and a good bryozoan fauna.The beds yield a predominance of smaller, more fragile shells (e.g.Lucina, Venus, Aloidis, Pteromeris and Anomia) with abundantforaminifera, which possibly have been deposited selectively bycurrents. A well-preserved 3 m solution hollow was clearlyobserved (Suffolk’s own karstic landscape); infill is mostly ofmore recent structureless and unfossiliferous regolith, makingdating of it impossible, but the hollow itself may pre-date the RedCrag, when subaerial processes prevailed. A bed of finer grainedsilty Crag at the base of the face marks the boundary between theSudbourne and underlying Ramsholt Members.

Following the work by English Nature, the lower part of theBullockyard Pit, seen next by the party on the eastern side of theKnoll, currently exposes about 5 m of silty/muddy sands of theRamsholt Member, possibly dating to as old as c.4.2 Ma (Wood,2009), making the section better than it has been since the daysthis when was a working pit. Exploratory excavations haveextended below the water-table to the London Clay. Medium-scalesand-waves are evident, although often indistinct, with mud-drapes, smaller ripples and extensive bioturbation, indicatingweaker currents and slow depositional rates. Estimates of waterdepth vary between <20 m and >50 m, but the sedimentary

sion to the ‘Pliocene Forest’ (Photo: R Gwyn-Thomas).

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Fig. 3. Sutton Knoll site plan. The area of Site of Special Scientific Interest is stippled.

R. Dixon / Proceedings of the Geologists’ Association 122 (2011) 514–523516

structures clearly indicate a depth shallower than storm base. Anabundant benthic fauna of molluscs and bryozoans is present, anddifferences occur in the faunas from different beds. Well-definedaccumulations of larger, more robust shells (e.g. the bivalvesArctica islandica, Cardita senilis, Pecten spp, Astarte spp, Venus spp,Glycimeris glycimeris and brachiopod Terebratula), often articulat-ed, form shell-beds (currently exposed in a drainage sump). Thecorals Spenotrochus and Cryptangia and fish otoliths are notuncommon in the shell beds; other common mollusc speciesinclude Aloidis gibba, Pecten tigrinus, P. maximus, Lucina borealis andCardita scalaris. The presence of a full size range for many species;articulated valves of juveniles of many species, includingTerebratula; entire echinoid tests, including the full size range ofTemnechinus, with fragments of Echinus sp. and Spatangid seaurchins; and a good fauna of smaller species indicate that theseshell beds may represent non-derived shell-gravel faunas.

Later in the morning, the group stopped to view the CorallineCrag ‘Rock Bed’, found on the north-western side of the Knoll in theQuarry Pit. About 5 m of shelly sands (Sudbourne Member) areexposed, cemented to form a relatively durable limestone, withevident bioturbation. The member exhibits well-developed medi-um- and large-scale trough cross-bedding, which is interpreted asstorm and tidal sand-waves migrating in relatively shallow water(c.30–50 m) in a generally south to south-west direction. In thisbed, post-depositional solution processes have dissolved aragoniteshells, and re-precipitated carbonate in the form of calcite to form a

cement. The ‘Rock Bed’ processes occurred before the deposition ofthe later Red Crag, as pebbles and boulders of ‘Rock Bed’ are foundin the Red Crag, and the term has no other stratigraphicimplication. It was often used locally as a building stone in farmwalls, including on the Sutton Estate, and in other structures suchas the river walls. It can also be seen as major components innearby Chillesford and Wantisden churches, and Orford Castle.Joint sets are well developed in the ‘Rock Bed’ and can be seen inthe pit walls; they may be related to the flexuring of the North SeaBasin. Occasional infilled solution pipes can be seen extendingdown from the surface.

2.2. Red Crag

The Red Crag is of late Pliocene age, around 2.5 Ma,unconformably overlying the Coralline Crag and London Clay(Fig. 5). It was formed in a high energy, shallowing sea dominatedby strong tidal currents, with submarine sand waves piling upagainst the shoreline to the west; the bedforms are consideredclassic of their type. It is dominated by molluscan shell gravelassemblages, which indicate climatic conditions similar to those ofBritain today: Glycimeris-Tapes assemblages occur at Walton-on-the-Naze and elsewhere in the south, with Spisula, Macoma, Mya

and Mytilus assemblages in the Deben/Butley area (Dixon, 1979).Until recently surprisingly little was known about the Red Crag

at Sutton, and no modern (post-war) quantitative or detailed

[()TD$FIG]

Fig. 4. Illustrative sketch section of the Coralline Crag ‘island’ at Sutton during the time of the Red Crag sea (first published in Dixon, 2007 and used on the interpretive panel at

the site).

R. Dixon / Proceedings of the Geologists’ Association 122 (2011) 514–523 517

molluscan studies or sedimentological studies have been done.However, it is now clear that very different localised molluscancommunities were able to develop in the different micro-environments that must have existed around the ‘island’ (Dixon,2007, 2009a).

The Red Crag abutting and unconformable on Coralline Crag isbest seen on the east face of the ‘island’ at the southern end of theBullockyard Pit, but is much overgrown. Prestwich (1871a)recorded over 2 m of Red Crag and his sketch sections show RedCrag banked up against a cliff of Coralline Crag. It contains muchderived Coralline Crag fauna, and even pebbles of that Cragencrusted with Red Crag barnacles. The ‘Facelift’ clearance work

[()TD$FIG]

Fig. 5. The basal Red Crag pebble bed of phosphatic nodules a

exposed over 13 m of the wave-cut platform cut by the Red Cragsea into the Coralline Crag. It dips southwards at over 108 andblocks of Coralline Crag can be seen resting on it. The preciseboundary is not easy to see at first sight because of the amount ofderived Coralline Crag material within the Red Crag, and it takes awell-practised eye to trace it laterally. When cleared in 2006 it wasprobably the first time it had been exposed for over 100 years!Colonies of Mytilus edulis and Neptunea contraria are found at thebase of the Red Crag adjacent to the Red Crag/Coralline Cragboundary, and indeed were noted by Prestwich. In fact, they canhelp to identify the boundary itself when the two lithologies mayat first sight appear so similar. The valves are articulated and

nd Boxstones overlies London Clay at Bawdsey, East Lane.

[()TD$FIG]

Fig. 6. The Bone Tooth – a rare Red Crag rhino molar found in the Red Crag at

Bawdsey, East Lane (Photo: A Bone).

R. Dixon / Proceedings of the Geologists’ Association 122 (2011) 514–523518

closed, and the full size range is present, juveniles as well as adults.Mytilus is typically an intertidal rocky shore species, attachingitself to firm substrates by means of its byssal thread, and thecommunities discovered at Sutton are undoubtedly in their lifepositions (Fig. 6).

Group members then walked over the knoll, pausing at thesummit to find quartz and quartzite pebbles. These may suggestthe former presence of Kesgrave Sands and Gravels, depositedbetween 0.6 and 1 Ma before the Anglian glaciation. The gravels,found in much of eastern Suffolk and Essex, mark the position ofthe former course of the proto-Thames.

A further stop was made at the southern end of the SSSI to viewfrom a distance Ramsholt Rocks, a further small outlier of CorallineCrag on the left bank of the River Deben, and to discuss the CragBasement Pebble Bed (seen later at Bawdsey). At the base of bothCrags is often found a discontinuous basal lag or remanie pebblebed containing cetacean remains, shark teeth and other fishremains, flints, ‘boxstones’ (rounded pebbles of late Miocene/earlyPliocene sandstone, c.6 Ma old), crustaceans and, importantly,phosphatic nodules (mistakenly called ‘coprolites’) derived fromthe London Clay. These ‘coprolites’ were excavated on a large scalefrom Sutton and elsewhere in the local area during the mid-nineteenth century for making phosphate fertiliser. The wastematerial of flints and ‘boxstones’ was used as a building material inthe nineteenth century restoration of Sutton and Shottishamchurches and in some other local buildings, including barns on theSutton Estate.

Of particular interest was the recording by Prestwich (1871a) inthis layer of a ton porphyry block from a trial pit in 1860 on thewestern flank of the Knoll, a site just visible from our view-point. Itwas the only known coprolite pit dug in the Coralline Crag (ratherthan Red Crag), but did not prove profitable and was filled in by themid-1860s. It is not known what happened to the porphyry

boulder – there is apparently no record of its whereabouts and itdoes not appear to be on the Estate. It may well still be buried. Thelocation of the pit has been discovered using old map records andby ‘walking the ground’, and it is hoped that geophysical methodsmay be able to detect the boulder at depth – the pit was 22 feet(6.7 m) deep – and that it can subsequently be retrieved.

In 2006 the Red Crag/London Clay boundary was temporarilyexposed in the Chicken Pit ‘pond’, actually an exploratoryexcavation originally dug by Bob Markham in September 1989.The entire exposed London Clay outcrop surface, about 2 m � 2 m,is marked by abundant Zirfaea burrows, c.50 mm deep andc.40 mm apart. Occurrence in these numbers is unique for theRed Crag – only isolated examples of Zirfaea burrows have beenfound before at other localities. Zirfaea crispata is an infralittoralbivalve, commonly found from extreme low water spring tide to adepth of c.10 m. It mechanically bores into soft rock, firm clays,shales, silts, peat and wood. It is evident that the monospecificcommunity thrived in this habitat before being overwhelmed bysand-waves. Prestwich also comments that Pholas (Zirfaea) wasfound boring into Coralline Crag in the Bullock-yard pit.

Careful clearing in and around Barry’s pit, at the western end ofthe Chicken Pit, has revealed another unique fauna. The sectionshows blocks of Coralline Crag, which evidently littered the RedCrag beach/cliff zone, dominated by articulated Mytilus-richassemblages. Many shells and cobbles of Coralline Crag haveRed Crag barnacles attached. The blocks are interspersed bypockets of relatively clean sand, which reveal many perfectlypreserved shells, including articulated Tapes and the brachiopodTerebratula apparently in the life position and with adult andjuvenile forms present. Articulated Ensis and Macoma have alsobeen found. Anomia, Buccinum, Capulus, Colus, Neptunea and theNaticidae family are also particularly well represented. It is evidentthat the fallen cliff blocks provided an ideal sheltered micro-environment for this unusual assemblage. Tapes typically occurs inshallow (extreme low water spring tide and below) sublittoralshell gravels and coarse sand. This important localised non-derivedfauna is the subject of current research by GeoSuffolk members.

Away from the ‘island’, exploratory excavations by EnglishNature for interpretive research, described by Dixon (2009a),revealed shelly sand-wave facies containing many phosphaticnodules. Because of the nature of the excavations, bedforms wereindistinct at best. It is clear, however, that a sand-wave faciesoccurs away from the ‘island’, and sand-waves can be seen in themore permanently exposed faces of the Chicken Pit. From these, itcan be observed that although variable, current directions trendgenerally towards the southwest, as elsewhere. Shell beds andother shell-rich layers probably represent shell avalanche materialaccumulating at the base of sand-wave foresets, again seen betterin nearby sections. Pebble beds are lag and remanie deposits, leftbehind after currents have swept finer material away; the lagdeposits indicate that current velocities must frequently been wellin excess of c.0.5 m/s, scouring the sea bed surface and winnowingsediment.

Offshore shell gravel assemblages dominate the mollusc fauna.Glycimeris-Venerupis assemblages tend to be found lower down thesequence, those two species making nearly 25% of some samples.Glycimeris is well-adapted to the physically rigorous conditions of acurrent-swept sand wave; associated Aloidis gibba, specialised forlife in the muddy bottomset sands between sand-waves, is alsocommon. Spisula shell gravel assemblages occur higher up thesequence, Spisula itself making over 20% of some samples. ExtinctSpisula ovalis is possibly an eco- or phenotype of the extant S. solida

(Long, 2000), which occurs in coarse sand from low beach toshallow depths, frequently in shell beds. Extinct Macoma speciesalso become more frequent. Gastropod frequencies tend to besomewhat variable – they are easily rolled and winnowed by

R. Dixon / Proceedings of the Geologists’ Association 122 (2011) 514–523 519

currents. Indeed, although the assemblages are good indicators ofthe original mollusc communities, it is clear that they have beensignificantly modified by sedimentary processes.

The vertical change in faunal assemblages can be identifiedelsewhere in the Red Crag basin, with Glycimeris-Venerupis

assemblages being associated with older Red Crag outcroppingto the south of the Deben and at depth, and younger Spisula

assemblages outcropping to the north. This sequence can be takento indicate a general shallowing during Red Crag times. Changes inthe nature of sedimentary structures seen in better exposures innearby pits also lead to this conclusion. It is also evident that theinfluence of the island rocky shore becomes more importanttowards the top of the sequence with a greater influx of Mytilus andother shoreline species, presumably being swept offshore bycurrents.

A general picture builds up, then, of an initial Red Crag seatransgression with a period of intense scouring of the sea bed bystrong currents, and erosion of the London Clay and Coralline Cragsurfaces. Coarse pebble beds were left behind as remanie deposits.There then followed a period of sand-wave migration, thesedimentary structures and shell gravel faunas indicating ashallowing, regressive sequence. As the Crag basin becameshallower the ‘island’ became a more positive feature and possiblyemergent, with the development of non-derived shoreline andinfralittoral faunas where suitable conditions allowed, but withmuch material being washed out to sea. It was at this stage that the‘fossil’ cliffs, wave-cut platform and ‘beach’ were formed. It shouldbe noted that this interpretation was the subject of somediscussion by group members!

After visiting the Quarry Pit, and ignoring demands for a lunchbreak (it was only 12.30 after all), the leader handed over the groupto Barry Hall, who was celebrating his 25th wedding anniversarythat day, for a guided tour of ‘The Pliocene Forest’.

2.3. ‘The Pliocene Forest’

In March 2009 GeoSuffolk applied for, and was awarded, a £372grant from the Curry Fund of the Geologists’ Association to create a‘Pliocene Forest’ – a plantation of representative plant genera thathad existed during Coralline Crag times. Inspired by a pollenanalysis from a borehole site near Orford by Andrew and West(1977) and, later, by Gibbard and Pegler (1988) from Sutton itself,the concept arose as part of a continuing programme of sitedevelopment and enhancement. Pollen analyses are uncommonfor the Crags – preservation is very poor (if at all) in the coarse,oxidised sediments, and British Pliocene Crag floras are stillrelatively poorly known. However, pollen analyses from theCoralline Crag have shown Pinus-dominated assemblages withSequoia, Picea, Sciadopitys, Abies, Tsuga and others, includingLiquidambar and Juniper, with heathers and grasses. They indicatea nearby Pliocene landscape dominated by forests containing asignificant number of exotic genera now native to Eastern Asia andNorth America.

GeoSuffolk member Barry Hall, a horticulturalist by profession,guided the work on the project. Deer and rabbits are a major threatto the plants in their early years; this meant the erection ofprotective fencing, creating a 10 m � 4 m safe enclosure. A specialmanure-based compost and weathered bonfire ash was used ateach planting site to improve water retention and the structure ofthe free-draining sandy soil. Continued nurturing and mainte-nance was needed until the plants become truly established.

After discussion with Professor Richard West, GeoSuffolkplanted four extant ‘Coralline Crag trees’ near the explanatorypanel and close to the public footpath, using 2 m ‘standards’ toprovide immediate visual impact: Sciadopitys verticillata (JapaneseUmbrella Pine), having a fossil record that goes back some 230 Ma

and already in decline by the mid-Cretaceous; Liquidambar

styraciflua (Sweetgum), with a similar form found in the Mioceneof Europe; Tsuga heterophylla (Western Hemlock); and Tsuga

canadensis (Eastern Hemlock). By the end of the year, additionaldonations had provided the two grasses, Stipa gigantea and S.

tenuissima, and the shrub Atriplex halimus (Salt-bush, whichperished in the harsh winter of 2009/2010) with the contrastingannual A. hortensis ‘rubra’ (Red Orach).

The project was described by the author in the Magazine of theGeologists’ Association (Dixon, 2009b).

The innovative original forest has aroused considerable interestamong visitors and field groups that have visited the site. So muchso that GeoSuffolk decided to seek to expand the ‘Pliocene Forest’on a much larger scale and longer timescale. In August 2009 thelandowner of Sutton Knoll, during a guided visit with his family tothe ‘Pliocene Island’ by GeoSuffolk members, gave approval forGeoSuffolk’s ongoing Site Management Plan in general and theexpansion of the ‘Pliocene Forest’ in particular. As Sutton Knoll[Rockhall Wood] is a SSSI, GeoSuffolk, through the landowner, alsoapplied to Natural England for consent to make these changes,justified on scientific, educational, aesthetic and general interestgrounds.

In March 2010 a further grant of £1692 was awarded by theCurry Fund to fence an expanded planting area of some 800–900 m2, centred more or less on the original enclosure, the workbeing carried out by Jeff Redgrave, a local geologist. Planting isarranged to have multiples of the same plant at different growthstages with a sub-theme of strong contrast between species of thesame genera (e.g. Atriplex hortensis ‘Rubra’ and A. halimus).Additional representative species include Pinus coulteri (largestcones) and Cryptomeria japonicum ‘Sekkan-sugi’ (foliage andcolour). Bush and shrub forms of some of the tree genera arealso being planted as understorey.

Helped by further fundraising, the spring 2010 season saw theplanting of several donated and sponsored trees: Tsuga canadensis

(Eastern Hemlock, tree form); Abies nordmanniana (Caucasian Fir –after a spell of duty as a Christmas tree); Cryptomeria japonica ‘Lobiinana’ (dwarf form); C. japonica ‘Sekkan-sugi’ (foliage); Platycarya

strobilacea (Caucasian Walnut); Sciadopitys verticillata; Microbiota

decussata (dwarf Cypress native to Siberia); Cunninghamia

lanceolata (China Fir); Picea breweriana; P. omorika; P. pungens

‘Hoopsii’; Quercus suber; Betula utilis var. ‘Jacquemontii’; Metase-

quoia glyptostroboides (Dawn Redwood); Ostrya carpinifolia (HopHornbeam).

Barry Hall is maintaining a ‘Forest’ database, which includes:name, type of plant, height & spread at planting, date of planting,location, source and cost, and donor/sponsor. Many other speciesof tree and shrub are under consideration. Monitoring andrecording of rainfall has been initiated and the height of thewater table being measured.

3. Locality 2: Bawdsey East Lane [TM 356397]

The group then drove to East Lane car park, where lunch wastaken amid remains of concrete bunkers from World War Two,prior to examining the foreshore south of the Martello Tower.

3.1. The London Clay

A brief description of the London Clay was given by David Bone.The London Clay comprises brown and grey predominantly siltyclays that were deposited in a shallow sea that covered much ofsouth-east England during the Eocene Epoch about 53 millionyears ago. England had a warm subtropical climate, with luxuriantrain forest and coastal mangrove swamps. Large sluggish riverscarried sediment and plant debris out to sea, where it settled and

R. Dixon / Proceedings of the Geologists’ Association 122 (2011) 514–523520

compacted on the sea floor. Plant debris, logs and branches, seedsand fruits, are now preserved as pyritised fossils. Walton-on-the-Naze, only 16 km away, is a key locality for the study of Palaeogeneplants in Britain and has considerable potential for future research.A useful summary of the sections at Walton, Harwich andWrabness is given by Daley (1999, pp. 61–72). Indeed, the LondonClay exposed at Bawdsey is very similar to that exposed on theforeshore at Walton. Many species of sharks and other fish swam inthe seas, and other vertebrates including turtles, have been found.Walton is also an internationally important site for finds of tinybird bones – also found at Bawdsey. A small invertebrate (mostlymollusc) fauna also occurs.

Well records show the London Clay at Bawdsey Manor to be87 feet (26.5 m) thick (Whitaker, 1906) and Davis and Elliot (1951)refer to between 11 and 20 feet (3.4–6.6 m) of blue London Clay,overlain by Red Crag, to be seen in the cliff one mile north-east ofBawdsey Ferry (i.e. East Lane). Currently about 5 m of blue-greysilty London Clay is well exposed in the cliff and on the foreshore atEast Lane, just to the south of the Martello tower, and is activelybeing eroded by the sea. When viewing the wave-cut platformfrom the beach or cliff top, the bedding can be picked out quiteclearly, showing that the London Clay has been gently folded withsome small faults. Calcareous mudstone concretions, ‘septaria’,once used locally for making ‘Roman’ cement, occur in thin bandswithin the London Clay.

No evidence was found for the thin layers of pale creamyyellowish rust-coloured sediment of volcanic ash; it was suggestedduring discussion that the sequence at East Lane overlies the ashhorizons, seen at Bawdsey Manor Cliffs and further south. The ashoriginated from ocean floor volcanoes as the North Atlantic openedup and with the break-up of the Greenland-Rockall plate, and waswind-blown from these volcanoes into the North Sea area. The ashdeposits can be correlated over the North Sea Basin and similarbands are found in Denmark & NW Germany. Over 30 layers arerecognised in Suffolk and northern Essex and correlate withGreenland volcanic events at 53 Ma (Daley, 1999, pp 14–21).

Much pyritized debris was found washed out on the beach;there are also pockets of drifted woody material which containfruits, diatoms and radiolaria. The foraminifera Astrorhiza isabundant. The teeth of the sharks Carcharias hopei, C. teretidens,

[()TD$FIG]

Fig. 7. At the time of the emplacement of the ‘rock armour’ to protect the Martello Topwer

slowly degrading. The shingle is now entirely removed; there is rapid basal cliff erosio

Striatolamia macrota and Otodus obliquus, and fish vertebrae can befound.

In the cliff, the London Clay/Red Crag unconformity was wellexposed. It is highly irregular, partly due to later cryoturbation, butin many ways resembles the eroded London Clay surface of thepresent wave-cut platform. There is c.2.5 m of Glycimeris-rich Cragwith a well-developed but discontinuous basal pebble bed ofphosphatic nodules and containing Boxstones, large flints andmaterial derived from the London Clay. Several shark teeth,including that of the shark Isurus hastalis, fragments of ray palateand cetacean bone fragments were found, but the find of the daywas undoubtedly that by David Bone of an extremely rare molarfrom the lower jaw of a rhinoceros, Dicerorhinus megarhinus

(Shreve pers. commun.).

3.2. Coastal defences

The Martello Tower was built in 1809 with 750,000 bricks at acost of £9784 to help protect the shore from Napoleon’s forces. It isone of only 17 left on the East coast. Twenty years ago it wasprotected by a large expanse of shingle beach (c.20 m) and 25 m ofland, and wooden groynes restricted long-shore drift. It wasbought by architect John Fell-Clark, restored and converted into a2-floor dwelling, now let as a holiday home.

In 1996 a new erosional cycle started; a big storm in 1997removed all the beach and some of the cliff. By 2005 the towerstood only 10 m from the cliff top. Following the storm, SuffolkCoastal District Council approved emergency funding for limitedboulder-style defence work in front of the tower, but this served toexacerbate erosion immediately to the south. Furthermore, EastLane Point is considered of key strategic importance in controllingthe movement of shingle between Aldeburgh and Felixstowe.

Bawdsey scored low on Department of the Environment andEnvironment Agency priority lists for coastal defences. Conse-quently, the East Lane Trust was formed to raise privately theestimated £2.2m needed for sea defence work to give greaterprotection to farm land, homes and the tower. Locally ownedfarmland in surrounding villages (Hollesley, Bawdsey, Alderton)was donated to the Trust, which then sold it off for housingdevelopment. Special governmental consent was given in 2007

in 2009 a shingle beach and talus afforded some protection to the cliffs, which were

n with cliff falls assisted by water seepage at the London Clay/Red Crag junction.

Table 1Percentage frequencies of dominant Red Crag molluscan species and ecological

groupings of all species from selected sample points at Alderton House Pit.

Bed 1 Bed 2 Bed 3

Intertidal rocky shore

Mytilus edulis 9.0 8.9 13.5

Total 9.0 9.3 14.3

Intertidal sandy shore

Mya arenaria 0.0 0.0 3.9

Total 0.0 1.0 4.4

Infralittoral 0.0 1.2 1.0

Sublittoral shell gravel

Glycimeris glycimeris 5.0 4.1 4.3

Venerupis spp 7.4 9.5 0.0

Total 13.0 14.9 6.1

Sublittoral muddy sand

Aloidis gibba 9.3 8.1 1.7

Total 9.6 8.5 2.0

Sublittoral clean sand

Dosinia exoleta 2.0 2.8 1.2

Total 3.1 3.3 1.4

Sublittoral mud tolerant

Turritella triplicata 6.9 13.5 8.9

Total 7.2 14.0 9.2

Sublittoral epifauna

Buccinum undatum 0.0 0.0 1.1

Neptunea contraria 0.0 0.0 1.1

Total 1.0 0.0 2.8

Miscellaneous

Chlamys opercularis 0.0 0.0 3.6

Venus ovata 1.0 1.1 0.0

Total 2.5 2.2 4.5

Extinct

Nassa granulata 0.0 0.0 3.3

Natica multipunctata 0.0 0.0 1.1

Polinices hemiclausa 0.0 0.0 1.1

Nucella lapillus 0.0 0.0 4.0

Astarte obliquata 1.9 1.7 0.0

Cardita corbis 2.2 1.0 0.0

C. scalaris 2.9 2.2 0.0

Cardium interuptum 1.3 1.4 1.0

Macoma obliqua 2.2 1.6 2.2

M. praetenuis 2.9 4.6 4.9

Spisula ovalis 27.1 14.6 16.3

Venus imbricata 1.7 1.4 0.0

Total 46.2 36.6 44.1

Unidentifiable 6.0 9.3 9.3

Total species 57 73 81

% of 1 individual 0.22 0.16 0.14

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allowing residential development on some of the plots that layoutside the ‘Local Plan’.

In 2008 this privately funded project was finally given the go-ahead – it is believed to be unique in England, and work began inSeptember. 22,000 tonnes of ‘granite’ (according to the press) werebrought by barge from Norway, each boulder weighing c.6 tonnes,to make ‘rock armour’ for c.350 m of cliff. In fact, much of thematerial is Larvikite and Gabbro, with a large proportion of FrenchCarboniferous Limestone, complete with crinoids, corals andbrachiopods. Work was completed in June 2009 at a cost of c.£2.4m.

Although some of the excellent exposure of London Clay andphosphatic basal Red Crag pebble bed had been lost as a result ofthe work and subsequent slope degradation, the focus of erosionhas merely shifted slightly, c.150 m southwards, for within 2months of completion, waves still reached the base of the cliffs andfalls were still taking place.

In February 2010 a further 12,000 tonnes of rock was brought infrom Northern France to reinforce coastal protection north of thetower to prevent flooding of low-lying farmland at a projected cost,using ‘emergency funding’, of £1.5 million.

Although the ‘rock armour’ was ‘‘holding up well andperforming as intended’’ (Fell-Clark, letter to the Editor, EastAnglian Daily Times 6.2.10), at the present time the entire shinglebeach has been removed by storms and the cliff section is activelybeing rapidly eroded – it has never looked better! (Fig. 7).

4. Locality 3: Alderton House Pit [TM 328412]

Members then drove the short distance to Locality 3, an old RedCrag section, now much overgrown, comprising an ‘old’ face and a‘new’ 3 m face lying some 50 m to the west, first exposed in the1950s. The older eastern section shows c.1.3 m thickness of large-scale sand-wave foresets [Bed 2], indicating a current direction of230–2408, the regional trend. It is stratigraphically overlain byabout 60 cm of trough cross-bedded shelly Crag [Bed 3].

The ‘new’ face shows medium-scale cross-bedding, demon-strating subordinate 2608 regional current directions, but domi-nant cross-cutting tidal flow directions towards 0808, withchannelling, mud drapes and other shallow water sedimentarystructures [Bed 2]. Some small, thin endogenetic tubes/burrows(provisionally attributed to an amphipod) occur and bioturbationis common in silty partings. It would appear that Bed 2 of the ‘new’face represents an accumulation of inter-ripple trough-zonesediments formed at the same time as the larger scale foresetsof the ‘old’ face. A pebble lag deposit occurs at the base of the shell-rich uppermost horizon [Bed 3], rich in phosphatic nodules andflints (including a flint belemnite and flint Terebratula). About35 cm is currently exposed. Large fragments of Echinocardium

cordatum test have been found in this horizon (Dixon, 2001a).Bed 2 in both faces is underlain by a further 1.8 m of sands [Bed

1] with comminuted shells interbedded with bioturbated siltscontaining Arenicola-type tubes, now completely obscured by talusbut exposed in the 1970s.

The Crag is rich in shells and this was a good opportunity formembers to sieve material and collect. The mollusc fauna isdominated by Spisula shell gravel assemblages in all horizons – thefrequencies of dominant species from selected spot samples aregiven in Table 1. The method used was given by Dixon (1977) butall species found were divided into their ‘ecological groups’ – thetotal frequency in each group is also given. It can be seen that thereis a significant increase in intertidal Mytilus and Mya frequencies,and a corresponding decrease in sublittoral Glycimeris andVenerupis in the upper beds, reflecting the regional trend ofshallowing water depths. There is also a notable abundance of thePea Urchin, Echinocyamus pusillus (Dixon, 2001b), and the solitary

corals Sphenotrochus and Balanophyllia are common here. Rolledbryozoans, derived from the Coralline Crag, are much in evidence,and shark and ray teeth are not uncommon. Of particular note isthe finding of a Pika tooth, Prolagus, by Bob Markham from Bed 3 ofthe ‘new’ face (Markham pers. com.) and the presence ofScrobicularia plana in the upper beds (Dixon, 1976). In manyrespects, the sequence and mollusc assemblages resemble those atVale Farm and Buckanay Farm, both seen during the Geologists’Association excursion in 2004.

5. Locality 4: Tarrants Pit, Ramsholt [TM 303422]

It was only a short drive to the final stop of the day, an 8 m deepworking Red Crag pit. There can be seen medium- and large-scalesand-waves with beds of shelly material, small-scale sand-waves,mud drapes, pebbly lag deposits – at least four, with phosphaticnodules, flint pebbles and convex-up Glycimeris valves (best seen inthe west and east faces). The section thus shows a series ofsuperimposed sand-waves: pebble beds demonstrating episodesof inter-sand-wave scouring, followed by small-scale sand-waveswith associated mud drapes forming as bottomsets in trough

[()TD$FIG]

Fig. 8. One of the pebbly lag deposits at Tarrant’s Pit; it indicates scour prior to bottomset deposition. Note the convex-up position of the Glycimeris valves.

R. Dixon / Proceedings of the Geologists’ Association 122 (2011) 514–523522

zones, and finally larger scale foresets with shell avalanchematerial at their base. Reactivation surfaces can also be seen – awell-defined such surface can be seen in the east face, with a 2 msand-wave above it. Current directions are predominantly towardsthe south-west and west, as is the regional trend, but subordinatecross-cutting directions towards the north-east are significant(Fig. 8).

Although not at first sight rich in shells, even a cursory searchyields Spisula/Macoma/Mytilus-rich assemblages – a shallow waterfauna typical of the upper part of the Red Crag in the Ramsholt/Alderton area. An abundance of small, thin, wiry tube-like tracefossils can be seen in some horizons, usually cleaner sands, as seenat Alderton House; they possibly belong to amphipods but theirorigin is uncertain. The top-most 1–1.5 m of Crag is decalcified.Two small reverse faults can be seen in the centre of the south face,with a combined throw of c.40 cm.

Several members sieved material and collected an interestingrange of fossils – of note were many Nucella and some phosphaticnodules encrusted with barnacles found in the pebbly lag horizons.One member found a much-rolled belemnite. Other molluscspecies found included Glycimeris glycimeris, Arctica islandica,Chlamys opercularis, Pygocardia rustica, Neptunea contraria, N.

‘despecta’, Nucella lapillus, N. tetragona, Nassa reticosa and Scaphella

lamberti.The pit was last visited by Geologists’ Association on Sunday

20th July, 1947, the final stop on a long week-end excursion basedat the Crown and Anchor Hotel, Ipswich. The pit was not named,but stated as ‘‘. . .a quarry north-west of Ramsholt Church. . .’’. TheCrag was described as intermediate between Newbournian andButleyan and many well-preserved fossils were collected (Oveyand Pitcher, 1948).

The meeting closed at about 17.30, after a good day enjoyed byall.

Acknowledgements

Sutton Knoll is privately owned; GeoSuffolk would like to thankSutton Hall Farms for innumerable access permissions and theircontinuing kind support. Mr. James Adeane kindly granted accesspermission for both Alderton House Pit and Tarrants Pit, both alsoprivately owned. Thanks go to Jim Rose and the two peer

reviewers, Jan Zalasiewicz and Peter Riches – the manuscripthas greatly benefited from their critical appraisal and is now muchimproved. Thanks also go to David Bone, who commented onearlier drafts of the London Clay at Bawdsey. Barry Hall is to becommended for guiding the party around the ‘Pliocene Forest’.Very special thanks go to Bob Markham, whose input as co-leaderwas greatly appreciated and who made many useful suggestionson the first draft of this report.

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