Excursion to Norbury, Mitcham Common and Beddington: Saturday
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E XCURSIO N TO NO RBURY, MITCH A)! COMMON AND BE DD Il"GTON 75 Valley . Here th e great difference in level between the gravels just examined and th e glacial gravels and boulder clay of the district immediately to the north was pointed out . The road to Radlett was then taken, where th e party arrived in good time for the train. REF ER E~ C ES. 19q . Summary of Progress of the Geological S urvey for 1913. p. 33. 191 5. I bid. for 1914. P·33· EXCuRSION TO NORBuRY, MITCHAM CO:\n ION AND BEDDlNGTON. S .HURD AY, APRIL 1 2 TH, 1 919 . REPOR T BY G. MACDoNALD D AVIES, l\I.sC. , F.G.S., Director 0/ the Excursion. 1. Routc.-At Norbury Tram Terminus, where th e boundary between th e County of London and th e Borough of Croydon crosses the main road to Brighton , th e Norbury Brook was seen (Section II. , below). Passin g a corner of th e London County Coun cil's housin g estate, where the disused clay pits and kilns for making bricks on the spot (Section IlL) were noticed, the par ty walked south-westward along Man or Road to Mitcham Common. This road is in part un metalled, and here the surface conditio ns associated with London Clay in rain y weather were studied with car e and interest.A tiny stream was crossed, which runs from near Thornton Heath' Pond to the Norbury Brook. The wide spread of WandIe gravel was rea ched at Mitcham Common. A lane nearl y oppo site th e cemetery in Mitcham Road brought th e party past a quantity of captured guns and war material and over the Croydon and Wirnbl edon railway (on the site of th e old Surrey Ir on Rail Road) to the British Portland Cement Manufacturers' works. Here sections were seen in gravel (Section IV.) and London Clay (Section V.). F rom the cement works th e party followed Beddington Lane southward, and reached th e Than et Sand just beyond the Wandie. Messrs. J esse Clack and Sons' pit in Sandy Lane, Beddingt on, Was visited (Section V1.), and tea was taken at the Harvest Home, where Mr. Prescott Row exhibited local flint implements (Section VIL), and Mr. W. Wright moved a vot e of thanks to th e Director. Th e path beside the Wandle Was th en followed, where many springs were seen at the junction of the Chalk and the Thanet Sand , and from th e bridge near Waddon Station, th e nature of the Chalk and Tertiary outcrop was noti ced (Section VIIL). The party returned to town by G. MACDONALD DAVIES, the 7.33 p.m. train from Waddon. Miss M. S. Johnston, F.G.S., acted as excursion secretary, and members of the Croydon and Wimbledon Natural History Societies joined the Association party. II. The Norbury Broo1?-The Norbury Brook is gradually being covered in, as houses take the place of the meadows through which it once flowed. The process, however, has not gone so far as in the case of the Effra, which was visited by the Association in 1912.5* The Effra has its source in a patch of Plateau Gravel on the London Clay hills of Upper Norwood, and the Norburv Brook rises in the Lower London Tertiaries at Addiscombe ;'but a far more important water-bearing horizon than either of these is the junction of the Chalk and Tertiaries, whence the Wandle derives most of its wa tel'. In 1918" members of the Association saw how the water from the Blackheath Beds on the Tertiary escarpment flows over the clayey Woolwich and Reading Beds and disappears on reaching the unsaturated Thanet Sand. On the dip-slope the streams have a. longer course, and the Norbury Brook flows through Addiscombe, Selhurst, Thornton Heath. Norbury and Lower Tooting, to join the Wandie near Merton. Its length is about seven miles, and in its lower course it is known as the River Graveney (from Tooting Graveney, where Graveney is a family name). III. Brickmaking tram the London Clay.-The brick making experiment at Norbury is not the only instance in Croydon's history of "the wickedness and deceitfulness" of the London Clay troubling the brick-makers. When the Whit gift Hospital in the centre of the town was being built. Samuel Finch, vicar of Croydon, kept the Archbishop informed of the progress of the work. On the 8th February, 1596, he wrote" "Weeks the bricklayer hath bene at your brick-clamps and commendes them for verie good"; but on the 7th March he has a tale of woe. "Rednap came hither this day; and assone as ever he came into the yarde and sawe the bricks, his harte was deade; he went to them, and chose here one and there, and knockt on it and said, 'he hoped there war better to be founde in the Parke.' To the parke we came, and there went from c1ampe to c1ampe, and here we founde and there some one or moe good, but not to the purpose of his owne expec tation. Fain he woulde have excused himselfe, but his handie worke spake against him, and we ware soe rounde with him, that he burste out into teares, sayinge, 'he was never the like served in anie worke; he was ashamde of it, he coulde not excuse it ; yt was the wickednesse and deceitfulnesse of the yearth. , Well, then to the lome pitts beyond Dubber's hill we came, neere Halinge-gate, where bricks had been made in tyme past. There • For References see end of Report. EXCURSION TO NORBURY, MITCHAM COMMON AND BEDDINGTON. 77 he founde such moulde as contented him." Bv " the Parke," the neighbourhood of Park Hill is meant, where there is an outlier of London Clay. At Dubber's (Duppas) Hill gravel rests on Thanet Sand, with a patch of Woolwich and Reading Beds on the northern side. "\Ve have our sande from Dubber's Hill," says Finch, "for the Parke favleth." IV. The Mitcham Gravel.-The Mitcham gravel forms a sheet I~- to 3 miles wide, with a surface level about 100 feet above Ordnance Datum at Mitcham Common, rising toward Croydon and falling toward Merton. It is a gravel of the WandIe, which practically forms its boundary on the south and west. Eastward it is separated by a slope of London Clay, etc., from an older Wandle gravel at Croydon and Thornton Heath, with an elevation of about 180 feet. Still farther east or north-east, the plateau gravel of Upper Norwood reaches 350 feet. The gravels were recently re-surveyed on the six-inch scale by Mr. Dewey", who correlates the Mitcham gravel with the Taplow (or 50-foot) terrace, and the Croydon gravel with the Boyn Hill terrace (the roo-toot terrace of the lower Thames valley). An inlier of London Clay rises like an island from the Mitcham gravel flat and forms a low hill at the Croydon Fever Hospital. Typical sections of the Mitcham gravel were seen about 200 yards south-east of the Cement Works in Beddington Lane. It consists chiefly of coarse, partially rolled flints, with some Tertiary flint pebbles, in a pale sandy matrix. A few green coated flints from the Bull-Head Bed and concretions from the underlying London Clay were seen. There was also a block of Lower Greensand chert in the pit, but this had probably been brought by human agency. Bands and lentic1es of sand are of frequent occurrence. They show varied and irregular forms, some of which appear to be due to current-bedding, while others would have been ascribed to ice-action if seen in any gravel north of the Thames. Thin bands of black manganiferous material also occur. As regards fossils and artifacts, the Mitcham gravel is very barren. Dr. Hinde records a discovery in 1889 at the Mitcham railway pits of remains of Elephas primigenius, Rhinoceros sp., Equus caballus, Rangijer tarandus, and small bovine bones'. The Croydon gravel is in general finer and more homogeneous, contains more pebbles, and has a yellow loamy matrix. It also has vielded remains of mammoth. V. The London Clay.-The gravel has been removed, to a depth of 6 to 12 feet, from a large area between Beddington Lane and the railway. The gravel-merchants, Messrs. Hall and Co., erected the cement works to utilise the London Clay thus laid bare, bringing chalk for the purpose from their pit at Coulsdon: and the works are now run on the same materials by the British Portland Cement Manufacturers. During the G. MACDONALD DAVIES, war the works were used as a box factory, and the clay pit had been full of water, which had only been pumped out a few weeks before the visit of the Association. Successive shore lines were visible, running as " parallel roads ,. round the pit. 'Vater trickling in from the gravel pits had in a very short time worn gullies in the clay walls of the pit and coated them with a ferruginous red deposit. The clay contains some concretions, usually non-septarian. On washing it yields a sandy residue consisting of fine-grained quartz with a fair amount of white mica, a few foraminifera and ostracods. flint, felspar, glauconite and chlorite. The heavy minerals are chiefly iron pyrites, in small spheres or larger aggregates, with zircon, rutile. kyanite, tourmaline, stauro lite, ilmenite, garnet, epidote, magnetite, hornblende and spinel. A chemical analysis of the London Clay at this pit (B.P.C.M.