field meeting at knockmill, kent: saturday, september 15th, 1934
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FIELD MEETING AT KNOCKMILL, KENT.
•Saturday, Septen1ber 15th, 1934.Report by the Director: ARTHUR L. LEACH, F.G.S
The party, meeting at Otford Station at 2.45 p.m., walked,as on former occasions, over Otford Mount to the Eocene outlierat Knockmill. The landscape features and the geology of theoutlier have been described in former Reports (see References).The special reason for the present visit was to examine a newsection exhibited in a shaft, 10 feet deep, sunk in the spring ofthis year. One side of this cutting, 13 feet wide, showed thefollowing section:
Brown loamy sand with scattered pebbles 2-7 ft.Reddish clay-with-flints .. 3-6 ..Chalk 2-4 ..
Although more than 50 bore-holes, ranging mostly between 20and 50 feet in depth, have been made within the boundariesof the outlier, the Chalk had never previously been reached.The new section, when considered in conjunction with the information derived from the earlier borings, supplies conclusiveevidence of what had previously been suspected, viz., the extraordinarily uneven surface of the Chalk below the Eoceneformations. At the new shaft the top of the Chalk is barelysix feet below the ground-surface,but 20 yards eastward pebblebeds 8 -t-ft. thick overlie clay-with-flints of unknown thickness;to the north, the old pit beside St. Clere Hill Lane, shows similarpebble-beds 23 -t-ft. thick; and to the south, at the large sandpitin the wood, sands and loams were proved to a thickness of 52feet and even at this depth neither clay-with-flints nor Chalkhad been reached. It is clear that the Eocene sands and pebblebeds rest on a very uneven surface of clay-with-flints which inturn covers a very uneven surface of Chalk, such as may be seenin the large pits which expose a pinnacled surface of the Chalkbelow Eocene pebble beds at Worms Heath in Surrey.
The party examined and discussed this new section, andalso the de-silicified flint pebbles and the blocks of silicified chalkwhich latter were first described in 1932 [3J, and then returnedto Otford. During tea, at the Oast House, Dr. J. C. M. Givenexpressed the thanks of the party to the Director for his serviceson the occasion of this fourth visit to Knockmill.
REFERENCES.
1. CHANDLER, R. H., and LEACH, A. L. 1908. Excursion to Knockmill(Oaklands) and Cotman's Ash. Proc. Geol, Assoc., vol. xx,p. 532 and plate xxix.
2. LEACH, A. L. 1921. Excursion to the North Downs in Kent.Proc. Geol, Assoc., vol. xxxii., fr. 36.
3. CHANDLER, R. H., and LEACH, A.-L.· 1932. The Eocene Outliernear Knockmill, Kent; and Rep~rt of Field Meeting. Proc,Geol, Assoc., vol. xliii., pp. 284-89 and plate 18.