THE WATLING STREET SECTIONS THROUGHSWANSCOMBE HILL.

WITH REPORTS OF THE EXCURSIONS OF 14TH SEPTEMBER, 1922,AND 30TH JUNE, 1923.

By E. E. S. BROWN, F.G.S., AND S. PRIEST, F.G.S.

PLATES 15 AND 16.

THE construction during 1922-23 of a new main road fromDartford to Strood, along the ancient Watling Street,

resulted in deep excavations through the heart of Swans combeHill, and for some months magnificent sections were exposed.The geology of this outlier was described in detail in 1920,*and further information furnished by the new sections is recordedhere.

The excavations afforded continuous sections rom ThanetSands to London Clay and, on the approaches to the hill,Pleistocene material of various kinds resting on Upper Chalkand ater deposits. As the cuttings into the hill proceeded,it was found that the Eocene Beds varied considerably in litho­logy end in thickness. The following description of these bedsis therefore a generalisation of continuous observationsrather than a precise account of the sections as seen on anyone visit. The details and measurements were compiled fromcuttings on the western side of the hill where the absence ofar.y considerable slipping afforded the best series of sectionsfor this purpose. Important variations in the beds in thecentre and towards the eastern side of the hill are describedseparately.

1. LANDENIAN.WOOLWICH BEDS.

Feet.1. (Top.) Thick dark-blue clays remarkably con­

stant in texture and generally crowded withfairly well-preserved shells 9 - 10

2. Brownish-green sands, frequently iron-stained,passing upward into light-coloured loamscrowded with crushed shells 3 - 3t

3. Brown and buff sands containing a constantband, 12" - 18" thick, of plant-remains in theform of powdery lignite. . 2

4. Firm grey sands with sparsely-scattered smallflint p bbles. No fossils observed. Seen for 6

• L. D. Stamp and S. Priest, The Geology of the Swanscombe Eocene Outlier, Kent, andReport of Excursion, Proc, Geol, Assoc., vol. xxxi., pp. 187-199.

WATLING STREET SECTIONS. 143

Bed 3 is undoubtedly the equivalent of the lignite bed sostrongly developed at Shame Wood. * The highest beds of theWoolwich Series are here absent as is frequently the caseelsewhere.

In the centre of the hill two 6in. bands of plant-remainswere seen, with zft. 6in. of shelly loams of Bed 3 between them.A little farther east this bed contained only one band of plant­remains, one foot thick, but formed of more compact Iigniticmaterial,

Of the two main divisions of the Woolwich Series, " a lowerBottom Bed sandy division and an upper Shell Bed clayeydivision,"] Bed 4 represents the top of the former and BedsI -3 the latter.

THANET SANDS.

Although not reached in the western cutting of the hillthese beds were exposed between Mounts Road and the firstslopes of the outlier. They occurred in wide hollows on theirregular Chalk floor, often separated by large pinnacles of Chalkand frequently let down into the latter by wide pipes. Theyappear to have been much disturbed by extensive solution ofthe Chalk but the portions preserved definitely belong to theloamy glauconitic base of the Thanet Sands, and the BullheadBed was generally in place.

On the eastern side of the outlier a lower series in theLandenian was exposed but, owing to slipping and the absenceof vertical sections, accurate measurements could not be obtained.The sequence of the beds was as follows, the numbering beingretained as above :-

I - 3. Extensive shell beds, the upper portions being dis-turbed by the overlying gravels.

4. Firm grey sands.5. Thin seams of stiff dark pipeclay.6. Sandy loams quickly weathering to a greenish tint.7. Basement pebble bed.8. Thanet Sands, upper portion only exposed.Bed 6 contained numerous concretions with bright red or

ochreous centres that rapidly disintegrated when broken, leav­ing reddish-brown patches similar to the iron-staining of theThanet Sands. Some of the concretions, however, containedlayers of hard black limonite.

Bed 7. The base of this bed was composed of crowdedpebbles with irregular pockets extending into the Thanet Sandsbelow. The junction appears to agree precisely with that

• R. H. Chandler, 1923, The Tertiary Section at Shorne Wood, Cobham, Kent, with Reportof Excursion, Proc. Geol; Assoc., vol. xxxiv., P. 139.

t Stamp and Priest, o-p. ca., p. 18g.

144 E. E. S. BROWN AND S. PRIEST,

described at Shome Wood* and illustrates the unconformitybetween the Woolwich Series and the Thanet Sands.]

z. YPRESIAN.Feet.

I. (Top.) London Clay, typical slaty-blue clay,withselenite and occasional septaria, weathering toa reddish-brown above, where it is affected byhill-slip and the surface deposits .. Up to zo

z. Passage Beds, mostly light brown in colour.The change from sand at the base, through sandyloams to the true London Clay, is very even.A few pebbles scattered in the lower portion. . 6 - 7

3. Well-marked pebble-band consisting of typicalsmall Blackheath pebbles in a fine white sand.Fish teeth common t - I

4. Yellowish brown sand with scattered pebbles. . zt5. Clean white sand. . Seen for 5 - 6From the above sequence it is not easy to determine the

exact division (if any) between the London Clay and the Black­heath and Oldhaven Beds. Bed z has therefore been called" passage beds" in view of the complete gradation from the lowersand and pebble series to the stiff blue clay above. The scatteredpebbles at the base of Bed z suggest a similarity to the lithologyof these beds in the HerneBay-Reculver section.t but there theyoccur at the base of the true London Clay, which rests" fairlyregularly" on the Oldhaven Beds. The greater part of Bed zis comparable with the "sandy clay" of the London ClayBasement Bed in the centre and western part of the LondonBasin§ and, if its location in the series is correct, it graduallybecomes unrepresented eastward in accordance with Dr. Stamp'spaper.

As the cutting proceeded eastward through the hill, Beds 3and 4 were seen to thicken to a maximum of 6ft., and becomecrowded with fossils, from which the specimens, enumerated inthe second of the appended lists, were collected. SimilarlyBed 5 thickened to a maximum of 8ft. 6ins., due to theincoming of large lenticles of small pebbles similar to Mr.Chandler's Bed 10 at Shorne Wood.] A little to the eastof the centre of the hill, near the top of Bed 3 butdefinitely contained in it, there occurred numerous cementedblocks, exceedingly hard and crowded with fossils'. Theseblocks were in the form of irregular slabs up to zft. in

• Chandler, op. cit, p. 137.t Stamp, 1921, Geol, Mag., vol, lviii., pp. 108-112.

t L. D. Stamp, 1921, The Beds at the Base of the Ypresian, etc., Proc, Geol: Assoc., vol.xxxii., p. 63.

I tus., pp. 59-63.II Chandler, op, cit., p. 139.

WATLING STREET SECTIONS. 145

thickness and of considerable area, necessitating blasting opera­tions for their removal. They are identical with those describedby Dr. Stamp and Mr. Priest as seen in a small excavation inthe floor of the A.P.C.:\L London Clay pit adjacent to the sectionsnow described. It is realised that their position in Bed 3 modi­fies their previous assignment to the London Clay BasementBed; but their occurrence in sit« has been observed for severalmonths along more than 100 yards of the sections now described,and it is clear that they are locally-hardened masses of theupper part of the Blackheath and Oldhaven Beds. It will beseen later that the palseontological evidence confirms theseobservations in every respect.

Still further eastward in the cutting, Beds 3 and 4 were seento decrease in thickness and pass into a clayey pebble bed; but,owing to the slope of the hill, the cutting downward of higherdeposits, and considerable slips, it was not possible to determinesatisfactorily the total thickness of the Blackheath and OldhavenBeds on this side.

3. PLEISTOCENE.In the early stages of the excavations good sections were

exposed of the usual surface deposits found in this district, whichhave frequently been described by previous writers in thesePROCEEDINGS. Only two sections in these deposits, exposedin the actual cutting of the outlier, require special mention.

On the extreme west of the hill a channel-course, some rzft.wide, filled with coarse drift material, was seen to have cutthrough the Upper Woolwich Beds deeply into the firm greysands (Bed 4 of the Landenian Series of this paper). Thetrend of the channel was northward to the Thames.

On the eastern slopes of the hill a wide hollow 50ft. acrossin the Landenian Series was filled with brickearth to a depthof at least roft. Mr. Whitaker has kindly furnished the followingnote on this occurrence ;-

(These deposits) .. "are hardly what would beexpected to result from downwash of the slope, mainly consist­ing of London Clay, and it occured to me that they had somelikeness to parts of the Erith-Crayford brickearth, etc.-an oldThames deposit. The Erith brickearth is bundled up sharplyagainst Chalk and Thanet Sands, and on the eastern side of theSwanscombe outlier, a little northward of Watling Street, therehave been found traces of beds which apparently are old Thamesdrift. In one place a large mass of London Clay has slippedover river gravel, just as at Erith masses of the Lower LondonTertiaries have done. It looks possible therefore that thesepeculiar Thames drifts may have reached as far as the easternface of the Swanscombe outlier. . ."

Unfortunately careful search in these deposits failed to revealeither implements, fossils or other useful evidence.

146 E. E. S. BROWN AND S. PRIEST,

PALEONTOLOGICAL NOTES.

By A. \VRIGLEY AND A. G. DAVIS.

FAUNA OF THE WOOLWICH BEDS.(Bed 1. Landenian Series.)

C = common. A = abundant.

C. Cytheridea muelleri Mimst. C. Hydrobia sp.Do. var, torosa Jones. C. Planorbis hemistoma Sow.

C. Tympanotomus [unatus (Mant.) C. Modiola sp. (all crushed).A. Melanatria inquinata (Defr.) (in- C. Cyrena (Corbicula) cuneijormis

eluding its juvenile form which Fer.has been described as Ceri- A. Cyrena (Corbicula) cordata Mar.thium gracile Mor.) Corbula regulbiensis Mar.

Melanopsis sp. Membranipora eocena Busk.[Neritina] Theodoxus sp.

C.

A. Cdfyptraea sp. ~* For explanatory footnotes see opposite.

FAUNA OF THE BLACKHEATH AND OLDHAVEN BEDS.(Beds 3 and 4. Ypresian Series).

C. Teeth of Odontaspis elegans (Ag.) A. [Neritina] Theodoxus globulus" " " cuspidata(Ag.) (Fer.)

Otoliths (earbones) of fish. .. " subornatus d'Orb.C. Aporrhais sowerbyi (Marrt.). mut. Actaion. 2 spp. (sutures de corti-

triangulata, Gard. cated).Hemipleurotoma cancellata (Desh.) Ringicula minor Desh.

ef. infraeocenica Cossm. Roxania ef. cincta (Desh).cf, laubr ierei Cossm. Planorbis hemistoma Sow.

" n. sp. I. Ostrea bellouacina Lam." n. sp. 2* Pecten (Propeamusium) prest-

C. Siphonalia maria: (Mellv.) wichii Mar.C. Paruisipho n. sp. (ef. infraeo- Area (Barbatia) striatularis Desh.

cenica Cossm.) A. [Pectunculus] Glycymeris plum-Tritonidea lata (Sow.)t steadiensis (Sow).[Pyrula] Ficus concinnus (Edw, Nucuia [ragilis Desh.

MS)-near tricostata Desh. Astarte n. sp. (ef. the Recent A.Pseudoliva fissurata Desh. eliiptica Brown).

" laudunensis Defr. (= A. Protocardium ptumsteadianumsemicostata Desh.) (Sow.)

[Cancellaria] Admete sp. C. Cyrena (Corbicula) cuneiformisOdontostomia prima-ua Desh. Fer.Eulima subnitida dOrb. " (Tellinocycl"s) tellinella Fer,[Cerithium] Benoistia lunni Cyprina sp.

(Mor.) C. Meretrix (Pitaria) n. sp. (ef.<::. Tvmpanotomus [unatus (Mant.) obliqua Desh.)§C. Melanatria inquinata (Defr.) Dosiniopsis bellovacensis (Desh.)C. Melanopsis buccinoidea Fer. Tellina sp.

" sp. Panopea intermedia Sow.[Scalaria] Acirsa [uniculosa Corbula regulbiensis Mar.

(Desh.) Corbulomya antiqua Desh.Hydrobia sp. Teredo sp.Adeorbis lucidus Cossm. Membranipora eocena Busk.

C. Natica (Naticina) abducta Desh. Serpula sp.repanda Desh. Ophioglypha soetherelli (Forb.)labellata Lam. Clione erodens,

WATLING STREET SECTIONS. 147

The fauna of the hard concretions occurring in the upper part of theOldhaven Beds comprised the majority of the above species of mollusca,including the brackish-water forms C. cuneijormis, C. tellinella, M. inquinata,and T. [unatus, The only species found in the concretions and not in thepe bbly sand was Cyrtodaria rutupiensis (Mor.), a fragile shell not likely to bepreserved unless supported by a hard matrix. It will be seen that theabove fauna is predominantly marine, but with a noticeable brackish-waterelement. Only four of the species (Pan. intermedia, Pseudo fissurata andlaudunensis, and N at.labellata) range above the London Clay Basement Bed,while the majority occur in the Thanetian of Northern France.

REPORT OF EXCURSION ON 14TH SEPTEMBER, 1922.

S. PRIEST, Director.

The morning party proceeded from Dartford Station toEast Hill, where the general topography was seen, and theneastward along the London Road, visiting numerous pits in theDartford Heath (roo-Foot Terrace) gravels, the more importantof which have been described previously.* Road-wideningoperations about half-a-mile west of Horn's Cross exposed CoombeRock deposits replacing sections of the gravels. At Howe HillPit the erratics again aroused interest. The igneous rock men­tioned in earlier reports was compared by Mr. C. E. N. Brame­head to some teschenite basalts at Arthur's Seat, while Mr. G. S.Sweeting has determined a slice as an olivine basalt. Tourma­line grits and tough Bunter quartzites were also noticed.

The afternoon party joined the others at Greenhithe andproceeded southward to Watling Street, reaching the newsections near St. James's Lane. Here a considerable thicknessof Chalk (Micraster corangtcinuni zone) had been exposed by thenew road excavations. The Chalk was strongly jointed andexamples of slickensiding were seen with gash seams of secondarysilica. Some layers of the Chalk showed distinct lenticularformation.

Many large pipes occurred filled with the usual mixed Eoceneand drift material, and a number were found to be in the formof continuous trenches running from south to north. Fourvertical sections (north and south sides of cutting and north andsouth sides of the temporary" island" in centre of road-cutting)

"S. Priest, 1915, Excursion to Greenhithc and Stone, Proc. Geol, Assoc q vol, xxvi., pp.78-85.

Explanatory footnotes from opposite page.• This and the four preceding species of H emipteurotoma were determined from a collection

of about 100 unbroken specimens, which included other members of this genus, apparently distinct,but too worn for a certain identification. We are indebted to Mr. I. L. Staadt for confirmingthese anti other detcrmina tions of species found in the French Thanetian.

t This species belongs to an Eocene group placed hy Cossmann in Tritoni-iea, but which differsmarkedly from the Recent genus of that name.

t Distinguishable from C. aperta (Sol.) not merely by the (in this genus) uncertain charactersof fonn and ornament, hut by the. lip, which. is thickened towards the columella where it is bentback and partly covers an umbilical ca vity.

9 A form universally common in thc London Clay Basement Bed.