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Excursion to French Street and Sundridge
52 3
EXCURSION TO FRENCH STR E E T AND SU N DR I DGE. SATURDAY, JUNE 4TH,
1910.
Directors: P. A. B. MARTI N AND LL. TREACHER, F.G .S. E x cursion Secretary : A. H. WILLIAMS. ( R eport by TH E D IR ECT ORS.)
ABOUT 20 members and friends met at Westerham for a walk th rough the Lower Greensand country to the south-east of the town. Leaving the stat ion at I o'clo ck, they proceeded by the footpath east of the church and th e main road up H osey Hill to near th e school. R ain coming on, lunch was tak en und er th e shelter of a clump of tr ees by th e side of the road which run s east ward to French Street. Th e walk being resumed, the Directors explain ed that in this part of Kent th e Lower Greensan d forms a range of hills parallel to the North Downs, an d, like them, has a steep escar pme nt facing southward, with a more grad ual dip-slope to the north. Its outcro p, abou t three miles wide, is deeply furrowed by a ser ies of cons equent valleys, some of which are wholly contained within the present area of the forma tion, while ot hers have shallow wind-gaps in the crest of th e escarpment, showing th at at one time they extended some distan ce farther back into th e Wealde n area. As th e present configuration of the country is largely determin ed by the character of the strata, it was pointed out that th e Lower Greensand here cons ists of four di visions: th e Atherfield Clay, which for th e presen t purpose might be classed with the un derlying Weald Clay; the H ythe Bed s ; the Sandgate Bed s, very th in, even if prese nt at all ; and the Folkeston e Beds, confined to the immediate vicinity of the Darent, which flows as a strike or subseq uen t stream at the foot of the dip-slope. Of thes e th e Hythe Beds are by far the most imp ortant. About 160 feet in average th ickness, they are composed of chert bed s abo ve and calcareous ragstone and hassock below. The chert covers all the highest ground of the district and sup ports a growth of heather and pine trees, while the rag occurs along the valley sides and bottoms, where it forms a comparatively fertile soil and is mostly under cultivation. Owing to the dip of the strata being greater than the fall of the streams th e upper ends of the valleys are excavat ed in the softer rag and clay beds, and are therefore wider than where, lower down, the str eams cut across th e more resistant beds. In the latter places they run th rough
524
EXCURSION TO FRENCH STREET AND SUNDRIDGE.
narrow gorge-like passes before joining the main Darent on the Folkestone Beds and Gault. Near French Street a good view was obtained of one of these valleys, in this case somewhat complicated in structure by a north and south fault, with a downthrow on the west side. Mr. Martin was of opinion that this fault preserved a part of the Sandgate Beds, as he had observed silicified fossil wood in an old quarry a short distance down the slope, but the rain prevented a visit to the section. Taking the carriage-drive across the valley south-eastward to the lodge of Weardale Manor, and the footpath through the woods near the new gardens, the party arrived at " The Knoll," a heath-covered eminence 800 ft. O.D., from which there is one of the best views over the Weald to be found anywhere along the escarpment. Remains of old shallow workings showed how extensively the chert had been quarried for road metal in former times. A short distance northward, by the side of the Sundridge road from Toy's Hill, was seen the new quarry belonging to the local district council, where the chert is worked to a much greater depth. Instead of being broken up, as in the surface workings, it occurs here in evenly-bedded layers, alternating with loose clayey material. Some discussion took place with reference to the origin of the hard bands, some of which are chalcedonic in places, the general opinion being that their formation has been going on from an early period by the dissolution, and later segregation, of the silica originally diffused throughout the entire mass in the shape of sponge spicules. Casts of these spicules may easily be seen in the less indurated parts of the chert. The walk was then continued by footpaths through the Chart to "Emmets," and eastward to the head of another valley west of Ide Hill. In the park near the lodge, by the Sundridge road, the water parting between the consequent and obsequent sections of the valley was examined. The former of these is broader, and has a comparatively gentle slope, while the latter is steep and narrower, and is evidently in process of rapid development. It would appear that the courses of these streams must be largely determined by underground channels or depressions on the floor of Atherfield Clay, as otherwise it would be difficult to explain the presence of so much water right on the dividing ridge, and also the occurrence of an obsequent valley at the head of every consequent. The water for both must be supplied by the drainage from the hills of IIythe Beds on both sides of the valley. The route now lay northward across the valley floor of Weald and Atherfield Clays to Brook Place, and then up the eastern side to an elevated spot from which there is a good view of the wind-gap in the escarpment, and of the broad upper end of the valley dotted with farms and cottages, pine-clad hills bounding it on either side. Northward again the party proceeded to
EXCURSION TO FRENCH STREET AND SUNDRIDGE.
525
Manor Farm, near which the stream runs through a narrow wooded gorge before joining the Darent below Dry Hill, where there is an interesting section in a farm-yard showing the centre of a small anticline in the Hythe Beds, the axis of which runs in a straight line hence to Westerham, where it is again exposed opposite Quebec House. In Fitton's time it must have been much better seen, the present condition of the ground giving evidence of former extensive quarrying hereabouts. Retracing their steps a little, the members then took the path westward along the top of the anticline, towards Sundridge Church, passing several ponds on its crest where the water is held up by some impervious layer in the Hythe Beds or possibly by the Sandgate Beds. In the grounds of Sundridge Place Mr. Watson, who resides here, showed the party a spring covered in by an ancient-looking stone building which suggested a Roman bath or the water supply of the monastic institution which once flourished here. Near it is a small outlier of Folkestone Beds capped by a thin layer of gravel belonging to the main Darent valley and probably of the same age as that on Limpsfield Common. A small section showed the current-bedded sands of which the outlier is composed. Passing on through Sundridge churchyard to the cross-roads in the village, the members took tea at the old club-room, kindly lent for the occasion. After tea and the usual votes' of thanks, proposed by Mr. H. A. Allen, they crossed the Darent and walked about a mile over gravelcovered terraces on its left bank to Chevening Halt, whence the 7.43 train was taken to London. REFERENCES. Ordnance Survey Map, Sheet 287, New Series. Geological Survey Map, Sheet 6, Old Series. 1836. FnToN, "V. H._H Observations on some of the Strata between the Chalk and the Oxford Oolite, in the south-east of England." Trans. Geol. Soc, voL iv, p. 133. 1875. TaPLEY, W.-" Geology of the Weald." Mem. Geol. Survey, pp. II9, 19 2 • 1891, PRESTWICH. l-" On the Age, Formation, etc., of the Valley of the Darent.' Quart. Journ. Geoi, Soc., vol. xlvii, p. 14 2 • 1909. TREACHER, LL., and MARTIN, P. A. B.-" Excursion to Toys' Hill and Brasted." Ante, p. 203.
EXCURSION TO FRENCH STR E E T AND SU N DR I DGE. SATURDAY, JUNE 4TH,
1910.
Directors: P. A. B. MARTI N AND LL. TREACHER, F.G .S. E x cursion Secretary : A. H. WILLIAMS. ( R eport by TH E D IR ECT ORS.)
ABOUT 20 members and friends met at Westerham for a walk th rough the Lower Greensand country to the south-east of the town. Leaving the stat ion at I o'clo ck, they proceeded by the footpath east of the church and th e main road up H osey Hill to near th e school. R ain coming on, lunch was tak en und er th e shelter of a clump of tr ees by th e side of the road which run s east ward to French Street. Th e walk being resumed, the Directors explain ed that in this part of Kent th e Lower Greensan d forms a range of hills parallel to the North Downs, an d, like them, has a steep escar pme nt facing southward, with a more grad ual dip-slope to the north. Its outcro p, abou t three miles wide, is deeply furrowed by a ser ies of cons equent valleys, some of which are wholly contained within the present area of the forma tion, while ot hers have shallow wind-gaps in the crest of th e escarpment, showing th at at one time they extended some distan ce farther back into th e Wealde n area. As th e present configuration of the country is largely determin ed by the character of the strata, it was pointed out that th e Lower Greensand here cons ists of four di visions: th e Atherfield Clay, which for th e presen t purpose might be classed with the un derlying Weald Clay; the H ythe Bed s ; the Sandgate Bed s, very th in, even if prese nt at all ; and the Folkeston e Beds, confined to the immediate vicinity of the Darent, which flows as a strike or subseq uen t stream at the foot of the dip-slope. Of thes e th e Hythe Beds are by far the most imp ortant. About 160 feet in average th ickness, they are composed of chert bed s abo ve and calcareous ragstone and hassock below. The chert covers all the highest ground of the district and sup ports a growth of heather and pine trees, while the rag occurs along the valley sides and bottoms, where it forms a comparatively fertile soil and is mostly under cultivation. Owing to the dip of the strata being greater than the fall of the streams th e upper ends of the valleys are excavat ed in the softer rag and clay beds, and are therefore wider than where, lower down, the str eams cut across th e more resistant beds. In the latter places they run th rough
524
EXCURSION TO FRENCH STREET AND SUNDRIDGE.
narrow gorge-like passes before joining the main Darent on the Folkestone Beds and Gault. Near French Street a good view was obtained of one of these valleys, in this case somewhat complicated in structure by a north and south fault, with a downthrow on the west side. Mr. Martin was of opinion that this fault preserved a part of the Sandgate Beds, as he had observed silicified fossil wood in an old quarry a short distance down the slope, but the rain prevented a visit to the section. Taking the carriage-drive across the valley south-eastward to the lodge of Weardale Manor, and the footpath through the woods near the new gardens, the party arrived at " The Knoll," a heath-covered eminence 800 ft. O.D., from which there is one of the best views over the Weald to be found anywhere along the escarpment. Remains of old shallow workings showed how extensively the chert had been quarried for road metal in former times. A short distance northward, by the side of the Sundridge road from Toy's Hill, was seen the new quarry belonging to the local district council, where the chert is worked to a much greater depth. Instead of being broken up, as in the surface workings, it occurs here in evenly-bedded layers, alternating with loose clayey material. Some discussion took place with reference to the origin of the hard bands, some of which are chalcedonic in places, the general opinion being that their formation has been going on from an early period by the dissolution, and later segregation, of the silica originally diffused throughout the entire mass in the shape of sponge spicules. Casts of these spicules may easily be seen in the less indurated parts of the chert. The walk was then continued by footpaths through the Chart to "Emmets," and eastward to the head of another valley west of Ide Hill. In the park near the lodge, by the Sundridge road, the water parting between the consequent and obsequent sections of the valley was examined. The former of these is broader, and has a comparatively gentle slope, while the latter is steep and narrower, and is evidently in process of rapid development. It would appear that the courses of these streams must be largely determined by underground channels or depressions on the floor of Atherfield Clay, as otherwise it would be difficult to explain the presence of so much water right on the dividing ridge, and also the occurrence of an obsequent valley at the head of every consequent. The water for both must be supplied by the drainage from the hills of IIythe Beds on both sides of the valley. The route now lay northward across the valley floor of Weald and Atherfield Clays to Brook Place, and then up the eastern side to an elevated spot from which there is a good view of the wind-gap in the escarpment, and of the broad upper end of the valley dotted with farms and cottages, pine-clad hills bounding it on either side. Northward again the party proceeded to
EXCURSION TO FRENCH STREET AND SUNDRIDGE.
525
Manor Farm, near which the stream runs through a narrow wooded gorge before joining the Darent below Dry Hill, where there is an interesting section in a farm-yard showing the centre of a small anticline in the Hythe Beds, the axis of which runs in a straight line hence to Westerham, where it is again exposed opposite Quebec House. In Fitton's time it must have been much better seen, the present condition of the ground giving evidence of former extensive quarrying hereabouts. Retracing their steps a little, the members then took the path westward along the top of the anticline, towards Sundridge Church, passing several ponds on its crest where the water is held up by some impervious layer in the Hythe Beds or possibly by the Sandgate Beds. In the grounds of Sundridge Place Mr. Watson, who resides here, showed the party a spring covered in by an ancient-looking stone building which suggested a Roman bath or the water supply of the monastic institution which once flourished here. Near it is a small outlier of Folkestone Beds capped by a thin layer of gravel belonging to the main Darent valley and probably of the same age as that on Limpsfield Common. A small section showed the current-bedded sands of which the outlier is composed. Passing on through Sundridge churchyard to the cross-roads in the village, the members took tea at the old club-room, kindly lent for the occasion. After tea and the usual votes' of thanks, proposed by Mr. H. A. Allen, they crossed the Darent and walked about a mile over gravelcovered terraces on its left bank to Chevening Halt, whence the 7.43 train was taken to London. REFERENCES. Ordnance Survey Map, Sheet 287, New Series. Geological Survey Map, Sheet 6, Old Series. 1836. FnToN, "V. H._H Observations on some of the Strata between the Chalk and the Oxford Oolite, in the south-east of England." Trans. Geol. Soc, voL iv, p. 133. 1875. TaPLEY, W.-" Geology of the Weald." Mem. Geol. Survey, pp. II9, 19 2 • 1891, PRESTWICH. l-" On the Age, Formation, etc., of the Valley of the Darent.' Quart. Journ. Geoi, Soc., vol. xlvii, p. 14 2 • 1909. TREACHER, LL., and MARTIN, P. A. B.-" Excursion to Toys' Hill and Brasted." Ante, p. 203.