Excursion to Plumstead and Crossness. July 5, 1873 - Geologists' Association excursion
Directors: Henry Walker, F.G.S., W. Whitaker, F.R.S., and Frank E. Houghton. (Report By H. Walker.) (Proc. Vol. iii p. 265.)
On arriving at Abbey Wood the company proceeded across the mantles, a distance of two miles, to the ground occupied by the Metropolitan Main Drainage Works at Crossness, admission having been kindly granted by Mr. J. C. Bazalgette, C.B. By the direction of Mr. Houghton, the marsh had been opened for a depth of eight feet, and in this section the buried land surface was well seen as follows:
| Alluvial Deposit | 2 | feet. |
| Yellow Clay | 3 | |
| Blue Silty Clay | 3 | |
| Peat bed, with stools of trees still rooted | — |
The succeeding deposits are thus given by Whitaker (Geol. London, 1889, ii. 66), in the details of the Crossness Well-boring in the same marsh:
| feet | |
| Peat with remains of trees | 6¼ |
| Dark Grey Silty Clay | 1½ |
| Thin layers of Peat and Clay, with decayed wood full of phosphate of iron | 1½ |
| Dark Grey Silty Clay | 2½ |
| Silty Sand | 2 |
| Valley Drift and Oldhaven Beds (?) | 49 |
| Woolwich Beds | — |
Among the stumps and trunks of trees (some of which were of considerable size), the oak and alder were recognised, a catkin of the latter being remarkably well preserved. Mr. Houghton exhibited some articles of furniture made from oak taken out of these marshes during the excavations for the Main Drainage Works. This forest-bed has a considerable range. From the bed of the river (in which the peat is found by soundings) the forest passes under the marshes of Kent on the one side, and Essex on the other, where it is concealed by the overlying alluvium, and is only revealed by excavations. The same forest was found under the alluvium in excavating the docks in and near the Isle of Dogs, and in excavations in Lambeth and Wandsworth Marshes. During the excavations in Plumstead Marshes for the Southern Outfall Sewer, in 1862-3, the forest-bed was well exposed. The Crossness Boring was then visited. [The details of this boring, as given in the report of this excursion, are necessarily incomplete, but may he seen in full in Whitaker's Geol. London, ii., 1889, pp. 66, 67. As this is one of the deep borings ending in "red-rocks" of Old or New Red Sandstone age, it is thought that the vertical sections of these and other deep borings of S.E. England, given below, will be found useful to those who wish to see their general results at a glance. They are from a Presidential Address to the Essex Field Club, by T. V. Holmes, on "The Subterranean Geology of South-Eastern England" (Essex Naturalist, Vol. ii., Nos. 9 and 10, Sept. and Oct., 1888). The deep boring at Streatham has also ended in rocks of Old or New Red Sandstone age.] The next visit of the Association to Plumstead was paid in 1887 to the Lower Tertiary escarpment, not the marshes. The Director was J. G. Goodchild, F.G.S., and a report was printed In Proc., vol. x., No. 4, p. 191.]
References
Maps
Ordnance Survey. Geological, Quarter Sheets, 1 S.W., S.E. 3s. each.
New Ordnance Survey. Sheets 270, 271. 1s. each.
Stanford's Geological Map of London. 5s.
Books
W. Whitaker, “Geology of London and Part of the Thames Valley." 8vo. 'London (Geol. Survey), 2 vols. 1889. 11s. [For literature.]
W. Whitaker, "Guide to the Geology of London." 8vo. London (Geol. Survey). 5 Edit. 1889. 1s.