Excursion to Orpington and Knockholt. Saturday, May 10th, 1879 (First of the Weald Series) - Geologists' Association excursion

From: A record of excursions made between 1860 and 1890. Edited by Thomas Vincent Holmes , F.G.S. and C. Davies Sherborn, F.G.S. London: Edward Stanford [For the Geologists’ Association], 1891. Source: Cornell University copy on the Internet Archive (Public domain work)

Director: J. Logan Lobley, F.G.S. (Report by W. Fawcett, B.Sc.) (Proc. Vol. vi. p. 189).

At Orpington, on the edge of the London Tertiary Basin, just outside the station, Mr. Lobley pointed out an exposure of Thanet Sands, the lowest member of the English Tertiaries, and, at a little distance, a good section of the Chalk, the uppermost of the English Secondaries. The presence of Chalk is clearly indicated by the altered character of the country from this point to Knockholt. The bottoms of the Chalk valleys are here covered by ten or twelve feet of gravel and wash of Pleistocene age, seen on this occasion in an excavation for new wells for the Kent Water Company close to the railway bridge. The road now runs along the bottom of the valley which is but a continuation inland of that of the Cray, but streamless from the absorbent character of the Chalk.

Arriving at Green Street Green, a fine section of Valley Gravels was pointed out, showing an increased thickness of this deposit, fully twenty feet being here exposed. After passing through the village, the ascent of the Downs was commenced, and the party speedily reached higher ground commanding a view over a large area. Mr. Lobley remarked that, instead of the ordinary appearance of sheep-walks in a Chalk country, we here meet with woods and cultivated fields. This is due to the presence c.f. superficial deposits of clays and gravels, the remains of the Tertiary beds once covering the Chalk. After passing High Elms, the road led over the upland towards Cudham. On the right is a beautiful example of a Chalk valley, with its steeply sloping sides and streamless bottom.

From Cudham the Downs were crossed, by Lutt's Green, to Knockholt village. From Knockholt Beeches, 783 feet, there is a most extensive view. Looking towards London, the Crystal Palace was visible on the high ground of the London Clay; to the south-east, the range of Lower Greensand hills on which Seven-oaks is built; and, further on, the hills of Hastings Sands.