Field Meeting on the Lower Tertiariesat Swanscombe, Kent

1 May 1960

Report by the Director: DENNIS CURRY

Received 3 March 1961

THE MAIN PURPOSE of the Field Meeting was to visit the celebrated road­cutting on the Watling Street at Swanscombe Park. This was originallyexcavated between 1922 and 1924, and the Association visited it twiceduring that period (Brown & Priest, 1924). After it had been completed,the cutting was grassed over and the sections which it had displayed werecovered up. In the early part of 1960, to provide an extra carriageway, thecutting was widened by about a hundred feet on the south side. As a resultthe magnificent section through the Woolwich and Blackheath Beds,originally described by Brown & Priest, became visible once more.

About thirty members and friends assembled at Swanscombe Haltstation and proceeded southwards along the High Street, Stanhope andSouthfleet Roads towards Watling Street, passing a large chalk pit on theirright-hand side. A short visit was paid to the southern end of this pit in theneighbourhood of map reference 613730.1 Here was seen an inconstantseries of sands and gravels containing Woolwich and Blackheath fossilslying on a very irregular surface of Chalk. The Chalk was exposed to adepth of about thirty feet. Although it contained quantities of flints, thesewere not disposed in layers but were scattered at random throughout thewhole mass of Chalk exposed. The party discussed at length the pheno­mena revealed and it was decided that the whole thickness of Chalk visiblehad been much disturbed, while the overlying sands must have travelleddownhill some distance from the higher ground around.

A very short distance (at 613729) from this disturbed section was seen asmall section in pale, fine sands of the Thanet Beds which showed no signsof disturbance whatever. At the corner of Southfleet Road and WatlingStreet the Director pointed out a transformer station which had recentlybeen erected and stated that a total thickness of at least thirty feet oftypical Thanet sands had been visible during the course of its construction.These also showed no signs of disturbance.

Leaving Southfleet Road, the party proceeded westwards along WatlingStreet to the Swanscombe Park road cutting (596727 to 603727). Here thefollowing section was seen:

1 All grid references lie within the 100 Ion. square.

261

262 DENNIS CURRY

ft. in.BASE OF {G b I . h '" 'I Ab 2 0WNDON CLAY rey rown cay Wit out 10SS1 s out

{

Yellow and white sands with seams and lenticles rich inBLACKHEATH battered and well-rounded flint pebbles and molluscanBEDS shells About 12 0

Buff and grey sandy laminated clay 4 0Grey clays, becoming sandy in the lowest 3 feet. A

WOOLWICH discontinuous band of grey-green marl, up to 3 inchesBEDS thick, about 6 feet from the top. Many fossils 11 0

Grey sandy clays as above 3 0Shelly grey-green sand with Corbicula 2 6Ferruginous sand with oysters 0 9Purple loam, carbonaceous in parts 0 6Buff sand About 5 0

WOOLWICH Pebbly glauconitic sand, seen in floor of road at eastBOTTOM BED end of section Thickness not ascertained

The above account is based on a section originally compiled by Mr.S. W. Hester in 1924, with modifications by Mr. Hester and Miss E. W.Andrews in 1960. Thanks are rendered to the Director, Geological Surveyand Museum, for permission to publish details from this section.

The fauna of the Woolwich Beds consists almost entirely of molluscs.These are beautifully preserved, but of relatively few species. Corbiculacuneiformis occurs in myriads throughout the fossiliferous beds while incertain bands Corbicula cordata, Brotia melanioides, Tympanotonusfunatus and Ostrea tenera are common. The marl bed in the middle of themain clay seam proved to be rich in very small molluscs, includingPlanorbis hemistoma, Bithinella websteri and Lapparentia pygmaea. A mostinteresting record from this bed was the discovery (believed to be the firstrecord from the Woolwich Beds) of fruits of Charophytes. Dr. L. Grambastof Paris kindly reports that these are of a new species of Stephanochara, agenus not hitherto known below the Upper Eocene.

The Blackheath Beds have yielded a rich series of molluscs of about fiftyspecies. They are for the most part very fragile and must be transportedwith care (preferably in dry sand) and be treated with a hardening solution.The commonest species are the lamellibranchs, Glycymeris plumstediensisand Nemocardium plumstedianum, with Pitar obliquus and Corbiculacuneiformis. The gastropods Aporrhais sowerbii, Brotia melanioides, Sigaticaabducta and Calyptraea sp, are not rare. Sharks' teeth also are fairlycommon.

The Director drew attention to the composition of the fauna of theBlackheath Beds, pointing out that it contains a mixture of marine andestuarine forms and that the proportion of estuarine forms diminishesfrom west to east. In this respect the fauna at Swanscombe was stated to

FIELD MEETING AT SWANSCOMBE 263

be intermediate between that of Abbey Wood on the one hand and Upnorand High Halstow on the other.

Members of the party spent some time in examining and collecting fromthe section in the road-cutting. Afterwards they proceeded southwardsthrough a wood to the face of a quarry at 599725. Here were seen aboutthirty feet of grey-brown unfossiliferous silty clay forming the lowest bedsof the London Gay. It then became apparent that the wood through whichthe party had walked covered the floor of the quarry, which was lastworked by the Associated Portland Cement Company Ltd. over fortyyears ago. The quarry floor coincided approximately with the base of theLondon Clay and workings came to an end when further extension wouldhave threatened a reservoir at 599724.

The party walked back to Swanscombe for tea, during which Dr. J. M.Hancock, on behalf of members, thanked the Director for organising theexcursion.

NEW FOSSIL RECORDS

A very full list of fossils was given by Wrigley & Davis (in Brown &Priest, 146, 147). Most of the species there recorded have been rediscovered.The following have been found in addition.

Woolwich Beds. Ostrea tenera J. Sby., Scrobiculabra condamini (Morris),Lapparentia pygmaea (Morris), Bithine//a websteri (Morris), Pollia cf. lata(J. Sby.), Stephanochara sp.

Blackheath Beds. Phacoides uncinatus (Defr.), Psammobia sp. Mactralevesquei d'Orb.

ACKNOWLEDGMENTS

Thanks are due to Mr. J. Collins, who first drew attention to the newsection, and to the County Surveyor, Kent County Council, and Messrs.T. H. Contractors Hire (Chiswick) Ltd. for permission to visit the site.

REFERENCEBROWN, E. E. S. & S. PRIEST. 1924. The Watling Street Sections through Swanscombe

Hill, with Report of Excursions. Proc, Geol. Ass., Lond., 35, 142-9.