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A traverse across the Weald
77
A TRAVERSE ACROSS THE WEALD (Weald Research Committee Field Meeting) Saturday, 27th September, 1947. Report by the Directors: J. F. Kirkaldy, D.Sc., F.G.S., and A. J. Bull, Ph.D., F.G.S.
THIS Field Meeting was planned to show, as far as it can be done in one day, the salient features of the structure, geomorphology and stratigraphy of the Weald. It proved very popular, 37 members and friends being present, whilst a score of others applied too late for seats in the coach. The route followed, together with full references, except to the relevant Sheet Memoirs of the Geological Survey, is therefore given below in some detail. Leaving the Embankment at 9.30 a.m., the coach left London by the Sutton By-Pass. A brief halt was made near Cheam to comment on the line of settlements which had grown up along the springline at the Chalk-Tertiary junction. The weather was very hazy, which was unfortunate, for the route passed a number of excellent viewpoints. The first of these was on Banstead Downs, but the London Basin was obscured and all that could be done was to draw' attention to the differences in relief and vegetation between the sub-Eocene and the sub-Pliocene erosion surfaces and to mention Groves' work [4*] on the nature of the deposits along the Brighton Road. During the drive southwards through Burgh Heath and Lower Kingswood, the" facet" between the two erosion surfaces near Garratts Hall was pointed out. Unfortunately the main road does not follow the ridge crest, so the degraded cliff or .. back" to the Pliocene bench [8, p. 62] could not be seen. Good views were, however, obtained of the heads of the dry valleys of the Chipstead Bottom system. Reigate Hill was descended slowly and such features of the view as were visible, including the bench formed by the Upper Greensand, the strike vale on the outcrop of the Gault and the Folkestone Beds and the dip-slope of the Hythe Beds, were indicated. The extensive exposures in the Hythe Beds in Bell Street, Reigate [7, p. 193]were noted. Brief stops were made at SidlowBridge and near Gatwick Racecourse to demonstrate the presence of a head of rejuvenation on the River Mole. At Sidlow Bridge the Mole is entrenched to a depth of about 10 feet into the Dominant (Boyn Hill) Terrace. Around HorIey the river is flowing on the surface of the same Terrace, which here forms the floodplain [3]. From Horley, the Balcombe-Cuckfield road was followed. For the first few miles on the Weald Clay, the landscape was flat and uninteresting, but near Poundhill the outcrop of the Tunbridge • For List of References see p, 79.
78
J. F. KIRKALDY AND A. J. BULL
Wells Sands was reached and the countryside at once became much more diversified. When the Mole-Ouse water-shed was crossed, the deep incision of the streams flowing southwards direct to the sea was very marked. About a mile south of Balcombe, a halt was made to examine rootlet beds in the upper part of the Grinstead Clay and in an adjacent sandpit the Lower Tunbridge Wells Sands [2, p. 76]. Continuing towards Cuckfield, a synclinal inlier of Weald Clay was pointed out as one of the many minor folds which together compose the Wealden anticlinorium. It was also an example of "uninverted relief," for the Ouse was flowing along the axis of the syncline, whilst the higher ground on either side was composed of anticlinally disposed Tunbridge Wells Sands. Unfortunately the visibility remained poor, so it was decided not to ascend the South Downs for the view from the Devil's Dyke, but to examine the ground at the foot of the Downs. From Cuckfield the route lay through Ansty and Burgess Hill to Hassocks, where the Lower Greensand was reached. The lowness of the escarpment, which is here composed mainly of Folkestone Beds, received comment, and a visit was then paid to Hudson's Red Sand Pit. In this very picturesque exposure the White Flint Drift overlies the greenish basal beds of the Gault and the vivid red Folkestone Beds [1]. Unfortunately the party was unable to find any fossils, so that the age of the basal Gault in this neighbourhood is still undetermined. From above the pit, the significance of the" 200-Foot Platform" [6] was discussed. After lunch at the" Royal Oak," Poynings, the beautiful road through Edburton was followed and fine views were obtained of the scarp face of the South Downs and of the broad feature of the Upper Greensand at their foot. Turning northwards towards Henfield, the party then visited the large clay pit in Upper and Lower Gault to the south of Small Dole. Numerous and typical lamellibranchs and cephalopods were found, but unfortunately the fine seam of "cone-in-cone" structure noted on a previous Field Meeting [5] has been partially removed by the extension of the pit. Opportunity was also taken to discuss in some little detail the structure of the Henfield neighbourhood [2, p. 81]. A brief visit was then paid to the Henfield Brickworks so as to obtain specimens of Paludina Limestone. Driving on through Henfield, the main features of the tongue of Lower Greensand in the syncline were indicated, and further on the feature formed by the Horsham Stone near Cowfold was pointed out. After tea at the Crab Tree Inn, Dr. G. W. Himus proposed the customary vote of thanks. Continuing towards Horsham, a brief halt was next made at the Hammer Pond near Coolhurst. The Dorking road was followed out of Horsham and a halt was made at the Clock House Works of the London Brick Company. Here the party was met by Mr. R. S. Franks, Manager of the Clay Block Division, who very kindly
A TRAVERSE ACROSS THE WEALD
79
explained the technical features of this fine section. The geological importance of the exposure is discussed in the following note. Ample time was allowed both to collect specimens and to discuss technical points with Mr. Franks. During the drive through Holmwood, the contrast in the nature of the escarpment formed by the Lower Greensand at Leith Hill and at Hassocks received comment. The last stop was made in the Dorking By-Pass to examine the pebbly developments at the top of the Hythe Beds. Specimens of derived Oxfordian ammonites and of fish teeth were forthcoming. As the light was now failing, the geomorphological features of the Mole Gap [9] did not receive the attention they deserved. The Embankment was reached shortly before 8 p.m,
REFERENCES I. 2. 3. 4. 5. 6. 7. 8. 9.
BULL, A. J. and others. 1935. Field Meeting at Hassocks and the Devil's Dyke. Proc. Geol. Assoc., xlvi, p. 401. THE DIRECTORS. 1947. Whitsun Field Meeting to the Central Weald. Ibid., lviii, p. 73. GREEN, J. F. N. and others. 1934. The River Mole. Ibid., xlv, p. 35. GROVES, A. W. 1928. Eocene-Pliocene Outliers between Chipstead and Headley. Ibid., xxxix, p. 471. KIRKALDY, J. F. and BULL, A. J. 1940. Field Meeting at Steyning and Henfield. Ibid., Ii, p. 72. . 1940. Geomorphology of the Rivers of the Southern Weald. Ibid., p. 115. . 1947. Report ofField Meeting at Reigate. Ibid., lviii, p. 192. WOOLDRIDGE, S. W. 1927. The Pliocene History of the London Basin. Ibid., xxxviii, p. 49. and BULL, A. J. 1925. The Geomorphology of the Mole Gap. lbid., xxxvi, p. 1.
A TRAVERSE ACROSS THE WEALD (Weald Research Committee Field Meeting) Saturday, 27th September, 1947. Report by the Directors: J. F. Kirkaldy, D.Sc., F.G.S., and A. J. Bull, Ph.D., F.G.S.
THIS Field Meeting was planned to show, as far as it can be done in one day, the salient features of the structure, geomorphology and stratigraphy of the Weald. It proved very popular, 37 members and friends being present, whilst a score of others applied too late for seats in the coach. The route followed, together with full references, except to the relevant Sheet Memoirs of the Geological Survey, is therefore given below in some detail. Leaving the Embankment at 9.30 a.m., the coach left London by the Sutton By-Pass. A brief halt was made near Cheam to comment on the line of settlements which had grown up along the springline at the Chalk-Tertiary junction. The weather was very hazy, which was unfortunate, for the route passed a number of excellent viewpoints. The first of these was on Banstead Downs, but the London Basin was obscured and all that could be done was to draw' attention to the differences in relief and vegetation between the sub-Eocene and the sub-Pliocene erosion surfaces and to mention Groves' work [4*] on the nature of the deposits along the Brighton Road. During the drive southwards through Burgh Heath and Lower Kingswood, the" facet" between the two erosion surfaces near Garratts Hall was pointed out. Unfortunately the main road does not follow the ridge crest, so the degraded cliff or .. back" to the Pliocene bench [8, p. 62] could not be seen. Good views were, however, obtained of the heads of the dry valleys of the Chipstead Bottom system. Reigate Hill was descended slowly and such features of the view as were visible, including the bench formed by the Upper Greensand, the strike vale on the outcrop of the Gault and the Folkestone Beds and the dip-slope of the Hythe Beds, were indicated. The extensive exposures in the Hythe Beds in Bell Street, Reigate [7, p. 193]were noted. Brief stops were made at SidlowBridge and near Gatwick Racecourse to demonstrate the presence of a head of rejuvenation on the River Mole. At Sidlow Bridge the Mole is entrenched to a depth of about 10 feet into the Dominant (Boyn Hill) Terrace. Around HorIey the river is flowing on the surface of the same Terrace, which here forms the floodplain [3]. From Horley, the Balcombe-Cuckfield road was followed. For the first few miles on the Weald Clay, the landscape was flat and uninteresting, but near Poundhill the outcrop of the Tunbridge • For List of References see p, 79.
78
J. F. KIRKALDY AND A. J. BULL
Wells Sands was reached and the countryside at once became much more diversified. When the Mole-Ouse water-shed was crossed, the deep incision of the streams flowing southwards direct to the sea was very marked. About a mile south of Balcombe, a halt was made to examine rootlet beds in the upper part of the Grinstead Clay and in an adjacent sandpit the Lower Tunbridge Wells Sands [2, p. 76]. Continuing towards Cuckfield, a synclinal inlier of Weald Clay was pointed out as one of the many minor folds which together compose the Wealden anticlinorium. It was also an example of "uninverted relief," for the Ouse was flowing along the axis of the syncline, whilst the higher ground on either side was composed of anticlinally disposed Tunbridge Wells Sands. Unfortunately the visibility remained poor, so it was decided not to ascend the South Downs for the view from the Devil's Dyke, but to examine the ground at the foot of the Downs. From Cuckfield the route lay through Ansty and Burgess Hill to Hassocks, where the Lower Greensand was reached. The lowness of the escarpment, which is here composed mainly of Folkestone Beds, received comment, and a visit was then paid to Hudson's Red Sand Pit. In this very picturesque exposure the White Flint Drift overlies the greenish basal beds of the Gault and the vivid red Folkestone Beds [1]. Unfortunately the party was unable to find any fossils, so that the age of the basal Gault in this neighbourhood is still undetermined. From above the pit, the significance of the" 200-Foot Platform" [6] was discussed. After lunch at the" Royal Oak," Poynings, the beautiful road through Edburton was followed and fine views were obtained of the scarp face of the South Downs and of the broad feature of the Upper Greensand at their foot. Turning northwards towards Henfield, the party then visited the large clay pit in Upper and Lower Gault to the south of Small Dole. Numerous and typical lamellibranchs and cephalopods were found, but unfortunately the fine seam of "cone-in-cone" structure noted on a previous Field Meeting [5] has been partially removed by the extension of the pit. Opportunity was also taken to discuss in some little detail the structure of the Henfield neighbourhood [2, p. 81]. A brief visit was then paid to the Henfield Brickworks so as to obtain specimens of Paludina Limestone. Driving on through Henfield, the main features of the tongue of Lower Greensand in the syncline were indicated, and further on the feature formed by the Horsham Stone near Cowfold was pointed out. After tea at the Crab Tree Inn, Dr. G. W. Himus proposed the customary vote of thanks. Continuing towards Horsham, a brief halt was next made at the Hammer Pond near Coolhurst. The Dorking road was followed out of Horsham and a halt was made at the Clock House Works of the London Brick Company. Here the party was met by Mr. R. S. Franks, Manager of the Clay Block Division, who very kindly
A TRAVERSE ACROSS THE WEALD
79
explained the technical features of this fine section. The geological importance of the exposure is discussed in the following note. Ample time was allowed both to collect specimens and to discuss technical points with Mr. Franks. During the drive through Holmwood, the contrast in the nature of the escarpment formed by the Lower Greensand at Leith Hill and at Hassocks received comment. The last stop was made in the Dorking By-Pass to examine the pebbly developments at the top of the Hythe Beds. Specimens of derived Oxfordian ammonites and of fish teeth were forthcoming. As the light was now failing, the geomorphological features of the Mole Gap [9] did not receive the attention they deserved. The Embankment was reached shortly before 8 p.m,
REFERENCES I. 2. 3. 4. 5. 6. 7. 8. 9.
BULL, A. J. and others. 1935. Field Meeting at Hassocks and the Devil's Dyke. Proc. Geol. Assoc., xlvi, p. 401. THE DIRECTORS. 1947. Whitsun Field Meeting to the Central Weald. Ibid., lviii, p. 73. GREEN, J. F. N. and others. 1934. The River Mole. Ibid., xlv, p. 35. GROVES, A. W. 1928. Eocene-Pliocene Outliers between Chipstead and Headley. Ibid., xxxix, p. 471. KIRKALDY, J. F. and BULL, A. J. 1940. Field Meeting at Steyning and Henfield. Ibid., Ii, p. 72. . 1940. Geomorphology of the Rivers of the Southern Weald. Ibid., p. 115. . 1947. Report ofField Meeting at Reigate. Ibid., lviii, p. 192. WOOLDRIDGE, S. W. 1927. The Pliocene History of the London Basin. Ibid., xxxviii, p. 49. and BULL, A. J. 1925. The Geomorphology of the Mole Gap. lbid., xxxvi, p. 1.