Excursion to Otford and Darent Valley. Saturday, July 3rd, 1909 - Geologists' Association excursion

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Geologists' Association Circular No. 110 Session 1908–1909[edit]

Excursion to Otford and Darent Valley. Saturday, July 3rd, 1909. (Transcription from GA Circular No. 110 Session 1908–1909 p3)[edit]

DIRECTORS : A. L. LEACH AND R. H. CHANDLER.

EXCURSION SECRETARY A. C. YOUNG, 17, Vicar's Hill, Lewisham, S.E.

Train leaves Holborn Viaduct 1.15, due at Otford 2.26. To obtain cheap return ticket, 2s. 5d., meet the Secretary at Booking Office not later than 1 p.m.

At rear of Station examine 8 ft. of chalky "rain wash" from the escarpment, resting on Chalk. The Rain Wash contains flint and chert, and abundant land-shells. Take road to Kemsing Chalk Quarry (on Shore Hill). This quarry (disused for many years) shows several large "pipes," some full of clay with flints, and others with sand and clay well bedded (? Eocene). The summit of the escarpment is capped with sand. One pipe is occasionally functional as some water runs down it ; the others are dry, and can be closely examined from the talus slope. From the escarpment the East arm of the Darent valley can be seen, and the position of a Limpsfield Stage (Prestwich) patch of gravel below Beechy Lees at 300 O.D. (about 80 ft. above the present stream), and somewhat lower a patch of Chevening Stage gravel. Descend the escarpment by an old road, now almost disused, and notice curious mile-stone at junction with Pilgrim's Way. Take foot-path across fields towards Otford and examine an instructive little anti-dip stream cutting its way back towards the escarpment. The spring rises from the foot of a vertical bank, 8 ft. high. This foot-path crosses the patch of Limpsfield Stage gravel (indicated above), which can be examined on the field and in a heap of picked stones ; but the Chevening Stage gravel is hidden by cultivation. Notice a large block of sandstone containing angular flints and rounded flint pebbles. Continue walk through Otford Churchyard, past ruined episcopal palace and Becket's Well, into village, where a spring is thrown out at the junction of the Chalk with the Gault. (A spring in a similar position was seen at Kemsing last year.) Take main Sevenoaks road to But and Ball Brick and Tile Works, noticing on the way drifted blocks of Lower Green-sand strewn about the Gault fields. At the brickyard, by permission of Messrs. R. Durtnell and Sons, examine the Low Terrace gravel of the Darent containing abundant Chert, and the underlying Gault which is very fossiliferous. Many of the fossils are pyritised, and phosphatic nodules form a distinct layer in the upper part of the pit. The pit shows the base of the Upper Gault, with probably the top of the Lower Gault. It yields Inoceramus sulcatus, I. concentricus, Belemnites minimus, and numerous Ammonites.

From the Gault pit the wide mouth of the valley by which the Darent breaks through the North Downs is well seen.

This excursion, with those of Dartford Heath (1907) and Limpsfield (1908), completes the examination of the most important drift stages of the Darent.

Return to Otford for tea at "Ye Olde Bull," and catch 7.36 train to London, due at Holborn 8.50.

Total walking distance, 5 to 6 miles.

REFERENCES.

1855. PRESTWICH, J.—"On the Origin of Sand and Gravel Pipes in the Chalk of the London Tertiary District. " Quart. Jour. Geol. Soc., vol. xi.

1879. PRICE, F. G. HILTON.—"The Gault." 8vo. London.

1886. SPURRELL, F. C.—"A Sketch of the History of the Rivers and Denudation of West Kent, etc." Report W. Kent Nat. Hist. Soc.

1889. Geol. Survey Map, 1-inch scale, Old Series, No. 6.

1891. PRESTWICH, SIR J.—"On the Age, Formation and Drift Stages of the Darent Valley." Quart. Journ. Geol. Soc., vol. xlvii, pp. 126-163.

1897. KENNARD, A. S.—"Excursion to Otford and Holmesdale Valley." Proc. Geol. Assoc., vol. xv, p. 209.

1907. CHANDLER, R. H., and A. L. LEACH.—"Excursion to Dartford Heath." Proc. Geol. Assoc., vol. xx, p. 122.

1907. BENNETT, F. J.—"Ightham" (in the "Homeland" Series).

1908. TREACHER, L., and P. A. B. MARTIN.—"Excursion to Limpsfield and Westerham." Proc. Geol. Assoc., vol. xxi, p. 59.

Images[edit]

List of photographs[edit]

Page 75 P805341 Spring thrown out by the Chalk Marl or Upper Greensand, rises from foot of a [natural?] bank 8 ft high. Excursion to Otford and the Darent Valley, July 3rd 1909.
Page 75 P805342 Showing edge of escarpment at Shore Hill. Excursion to Otford and the Darent Valley, July 3rd 1909.
Page 75 P805343 Milestone at junction of Pilgrim's Way directing to Malling, Bromley, Sevenoaks and Dartford. Excursion to Otford and the Darent Valley, July 3rd 1909.
Page 75 P805344 Chalk pit north of Otford Railway Station showing deposit of chalky drift. Excursion to Otford and the Darent Valley, July 3rd 1909.
Page 75 P805345 Chalk pit north of Otford Railway Station showing deposit of chalky drift. Excursion to Otford and the Darent Valley, July 3rd 1909.