145

EXCURSION TO BEXLEY AND BEXLEYHEATH.

SATURDAY, MARCH 6TH, 1920.

PART I.

REPORT BY S. PRIEST, F.G.S., Director of the Excursion.

EIGHTEEN members and a few Dartford Field Club friends metat Bexley Station at 2.18, and walked through High Streetto the River Cray. Here the Director gave details of the peatbed revealed by trench sections in 1912. Resting on Craygravel, and overlain by marsh clay, its thickness was 14 to 18inches at the railway bridge, thinning out entirely at BourneRoad. It yielded bones of living species (including boar tusks)and an iron spear head (Saxon). Evidence of vivianite wasafforded by a bluish white coloration on the bones, intensifyingto blue on exposure and drying. Along North Cray Road,trenches have shown loamy downwash, with lenticles of shellydebris, derived from Eocene beds of neighbouring slopes. ALcs Eyzies flake obtained here by the writer has been recordedby R. H. Chandler.* Mount Mascal consists almost entirelyof Thanet Sand. The President said there was a little Wool­wich material on the top. The party turned northwards by Wol­lett Hall and re-crossed the Cray. Peaty alluvium was here recog­nised; it was characteristically black, and nourishes a richflora of marsh plants. The marshy belt was noted as being ratherwide for a river of the size of the R. Cray. In the rising groundtowards the railway, Thanet Sands and the Bottom Bed of theWoolwich Series come in, but are much obscured by a pebblywash from Blackheath Beds higher up the slope. At the Loop­Line crossing (between Bexley and Sidcup), steps had been cutin the Woolwich Shell Bed, and Cyrena were abundant. In thecutting to the West, Oldhaven (Blackheath) Beds-sands andpebbles-were formerly seen to rest erosively on the WoolwichShell Bed.j Fossils occurred in the former ncar the bridge. Thehighest ground is occupied by London Clay, which tends to formhills as , for example, near the Hurst. The President pointed outthat hereabouts the Eocene Beds are not covered by Drift. In Bex­ley Park Woods, the dry Blackheath Pebble Beds cropping outalong the unmade Camden Road, afforded better walking thanthe London Clay recently left. Along Park Wood Road, cleanBlackheath sands are seen beneath the Pebble Beds.

On descending Park Hill Road to Gad Bridge, the Shuttle.R. H. Chandler, U Implements of a Us Eyzies Type, etc. in the River Cray Valley,"

Proc. Prebisr. Soc. East A nglia, vol. ii, part i, 1915, PP. 80·98.nV. Whitaker, "Geology of London," vel. i, p. '39, Met«, Geol, Surv. (,889).

146 L. D. STA:\1P,

tributary was seen to have developed quite a considerable­valley; but it was remembered that Eocene Beds are compara­tively easy to erode. Near Bridgen, Arbuthnot Lane and suc­ceeding fieldpaths were followed north-westwards to PincottRoad (Bexley Heath). over Blackheath Beds practically thewhole distance. In summer, spurrey flourishes on this land andindicates its loose, dry character.

From Bexley Heath Broadway, Long Lane was reachedvia Woolwich Road. At the bridge over the Bexley HeathRail­way, Woolwich Shell Beds were exposed, and they arc also knownto occur at the local Isolation Hospital. Typical fossils previous­ly collected by the Director were examined, and Mr. Stampmade some remarks on the section (see below). The sharpestshower of the afternoon now caused the party to hasten, viaLong Lane and May Place Road, back to the Broadway for tea,after which, the President, with all his usual cheery kindliness,thanked the Director for his services on the Excursion.

Along the Broadway, towards Christ Church, recent trenchesshowed more dry, permeable Blackheath Pebble Beds, their oc­currence over this broad tract favouring the rapid developmentof a healthy residential township.

On the South side of Bexley Heath Station, a small bankshowing London Clay (reddish-brown, sandy Basement Bed)had been left. Just a few inches of slippery London Clay wereseen above.

Members left Bexley Heath by the 6.19 train.Mr. E. E. S. Brown acted as Excursion Secretary.

PART II.

~OTE OX THE SECTIOX EXPOSED I~ THERAILWAY CUTTI~G BETWEE~ BEXLEY HEATlf

A~D BARNEHURST STATIOXS.

L. DUDLEY STAMP., M.Sc., F.G.S.

Although the Association were not able to walk along thiscutting, and the glimpse which they obtained from Long LaneBridge was by no means improved by the inclemency of theweather, it may be of some use to give a few details of the section.

The cutting was made in 1892-3, after the publication of theMemoir on the London District, so that geologists have not,in this case, the advantage of Mr. Whitaker's lucid descriptions,The only account of the section, so far as the writer is aware,is in a report of an " Excursion along the New Railway fromBlackheath to Bexley Heath" by Mr. T. V. Holmes. * Mr..

·Proc. Geol. Assoc., vol. xiii (i893), p. 152.

Ostrea sp.Aporrhais Soieerbyi Mant.Natica sp.Pvrula Smithii Sow.r~usus sp.

EXCURSIO~ TO BEXLEY .Axn BEXLEY HEATH. 149

Whitaker visited the section soon after it was made, and he hasvery kindly allowed me to see his unpublished notes, which Ihave freely incorporated with my own observations.

Bexley Heath Station, built in a shallow cutting, is situatedtowards the eastern margin of a small outlier of London Clay.The greatest thickness seen of the Clay was not more than tenfeet; in the upper part there are a few septaria. The Clay isvery sandy in the lower part and there is a pebble bed about afoot thick at or ncar the base. Mr. Whitaker, during theconstruction of the railway, noticed that this bed was cementedinto a hard shelly conglomerate at one point. Following hisnotes, I have now located the spot. On the north side of thecutting IS yards west of the bridge at the west end of BexleyHeath Station.: the hardened Basement Bed is seen projectingfrom the partly grassed slope. The following fossils were obtainedin a very short time :-

Axinaa plumsteadiensis Sow.Panopcea intermedia Sow.Protocardium plumsteadiense Sow.Cytherea ? orbicularis Edw.Cytherea? tenuistriata Lamk.Cytherea cf obliqua Lamk.Further investigation of this bed would require ,certain

precautions and the express permission of the Railway Com­pany. This occurrence in situ is of particular interest in thatit removes any doubt as to the horizon, from which the well­known fossiliferous blocks * in the brickearth at C.H. Norris'sPit, North End, Erith, have been derived. The latter are al­most identical lithologically and faunally and the two localitiesare only about a mile and a half apart.

Below are seen sandy Blackheath Pebble Beds, some ofthe pebbles being of large size-c-up to 8 inches in length but, asusual, perfectly rounded. From Bexley Heath Station, east­wards for half-a-mile the cutting is in Blackheath Beds. Theyare strongly false-bedded and consist of alternating obliquelayers. of coarse and fine pebbly beds. The" false-dip" of thelayers is between IS and 20 degrees to the West. A mile anda half to the north-west at Erith, the " dip" is to the South­east, at Elmstead it is to the North, whilst on Blackheath it issaid to be in all directions. t This illustrates the varying cur­rents and disturbed conditions which prevailed in the Black­heath Sea. No fossils have been observed in this cutting in theBlackheath Beds.

A short distance to the West of Long Lane Bridge WoolwichShell Beds are seen beneath the Blackheath Beds; and a small

.OR. H. Chandler and A. L. Leach, Proc; Geol, Assoc., vol, xxiii( I9I21. p. I88.tHo M. De la Condarn.inc, Q.].G.S., vol. vi, (I850), p, 440.

L. D. STAMP,

fault, running a little north of west to south of east with a down­throw on the North, cuts obliquely across the line.

Between Long Lane Bridge and Barnehurst Station thebeds are roughly horizontal, but the railway slopes gently east­wards, so that lower beds appear. As far eastwards as ThreeCorner Wood (between the Erith Road Bridge and BarnehurstStation) the upper part of the cutting is in Blackheath Beds,which rest irregularly, as usual, on different members of theWoolwich Series. Their lower part tends to be sandy and thepebbles small, the sand being doubtless largely derived from re­sorted material of underlying beds.

Rising up as hummocks into the pebble beds are a few patchesof well-bedded light-coloured loams, full of plant-fragments,and corresponding in lithology and position with the" leaf-beds"of Lewisham and the "striped loams " of Charlton. One ofthese patches can be seen on the south side midway betweenLong Lane Bridge and Erith Road Bridge. Below is a bed ofsand now very much obscured and frequently eroded away beforethe deposition of the Blackheath Beds. This bed cannot bemore than a foot or so in thickness.

Below come Woolwich Shell Beds, dark, well-laminatedclays, about 5 or 6 feet in thickness. They are roughly divisibleinto three la.yers; the upper full of Cyrena cuneiformis, Cyrenacordata, Potamides funatus, M dania inquinata and Ostrea,the middle consisting almost entirely of Ostrea, the lower againof Cyrena, etc. Harder calcareous bands occur, especially inthe upper part, and the fossils, as usual, arc much crushed.The species of Ostrea seems to be O. tenera. I was unable tofind any undoubted fragments of O. bellovacensis.

Below the shell beds come the Bottom Bed of the WoolwichSeries. At least 6 to 8 feet are exposed in the eastern portionof the cutting. It consists of sand, extremely rich in glauconitein the upper part (now altered to dark red-brown limonite exceptin patches). In the lower part it is less rich in glauconite andconsequently paler in colour. The base of this bed is not seenas the ground round Barnehurst Station is disturbed and confusedby slipping. The embankment cast of the station, however,rests on Thanet Sand.

This section is of interest as affording yet another exampleof the irregular way in which the Blackheath Beds rest on theWoolwich Beds. The writer can conceive no adequate set ofconditions which -would allow the deposition of isolated patchesof well bedded loams (without pebbles) at widely separated local­ities like Lewisham, Charlton and Barnehurst, contemporane­ously with the surrounding pebble-beds. The only adequatehypothesis seems to be that the bedded loams were laid down

EXCURSION TO BEXLEY AND BEXLEY HEATH. 149

over the whole area and subsequently removed before the deposi­tion of the Blackheath Beds. In other words, the BlackheathBeds are absolutely distinct from the Woolwich Beds and thereis a well marked pre-Blackheath (pre-Oldhaven) erosion.

REFERENCES.

Maps.-lin. Ordnance, Sheet 116, Large Sheet Series.6in. Ordnance, Sheets Kent 8N.E., 8S.E., 2S.W.lin. Geological Survey, London, Sheet 4.

VISIT TO HORNIMANS MUSEUM, FOREST HILL, S.E.

SATURDAY, :MARCH 13TH, 1920.

A VERY interesting Demonstration was given by the Curator,Dr. H. S. Harrison, on the domestic and warlike implementsused by primitive man from the Palseolithic period to the presentday, of which the Museum possesses a very representativecollection. The method of using them was also well representedby the exhibits.

After this Mr. Milligan gave a: Demonstration on the speci­mens collected to show motion in animals, and conducted theparty through the Aquarium, the only one now existing inLondon.