View source for Excursion to Bromley, Sundridge, and Chiselhurst. April 22nd, 1876 - Geologists' Association excursion

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[The first visit to the above places [Bromley and Chiselhurst] was on June 18th, 1864, and is reported, Proc., Vol. i. p. 404, by A. Ramsay, junr. The next was on June 15th, 1872. On this occasion the Directors were James W. Ilott and Coles Child. After inspecting the Sundridge Park and other sections the party proceeded to the caves in the Chalk under Camden Park, which had been illuminated by Mr. Strode, the owner of the estate. The brief report of this excursion may be read, Proc., vol. iii. p. 114. Another excursion took place on April 22nd, 1876, J. L. Lobley being Director, and a full account follows.]
==Excursion to Bromley, Sundridge, and Chiselhurst. April 22nd, 1876==

'''Director—J. Logan Lobley, F.G.S. (report by the director.) (Proc. Vol. iv. p. 498.)'''

A large area in the neighbourhood of Bromley is occupied by the Shell-beds and the overlying Sands and Pebble-beds of the Woolwich and Blackheath Beds, and good sections of these beds are exposed along the railway near Bromley Station. In the cutting to the east of the station the Shell-beds of the Woolwich and Reading Series are inclined at a low angle to the west. The characteristic ''Cyrena cuneiformis'' occurs here in great abundance, associated with Ostrea. At the western end of this cutting the Sands form the upper beds exposed.

The Pebble-beds are well seen immediately behind the railway station, by the side of the inclined road which has been cut through them. These remarkable beds, an accumulation of shingle, are, with the underlying sands, the equivalents in the western part of Kent of the beds exposed at Oldhaven Gap, near the Reculvers, and called by Whitaker the "Oldhaven Beds." They consist of smooth, oval, black flint pebbles, with, in some places, a considerable quantity of intermingled sand, and in others a matrix of carbonate of lime which cements the pebbles together, forming a conglomeratic rock; and in other localities, as at Blackheath, the pebbles are almost devoid of any intermingled material. As has been pointed out by Whitaker, the entire absence of subangular or little-worn pebbles indicates that this vast bed of worn Chalk flints was not a shore accumulation of shingle at the foot of a Chalk cliff, like that now forming the beach at Brighton, but was doubtless a shoal or bank considerably removed from the shore line, which pebbles would only reach after much rolling and consequent wear. The bed of quartzose sand, found underlying the Pebble-beds, Whitaker considers ought to be associated with them, and not with the Woolwich Beds. The sand has here a most irregular upper boundary, the Pebble-beds entering it in wedge-like or teeth-like masses to a considerable depth. This section shows a remarkable instance of current-bedding, the oval pebbles lying with their longer axes horizontal, while, as has been pointed out by Whitaker, lines of bedding, inclined at an angle of 25º, are very distinct. This is, perhaps, even better seen at a new section of the same beds on the opposite side of the railway, which was next inspected.

A walk through the village of Bromley brought the party to the grounds of Bromley Palace, the residence of the late Mr. Coles Child. A small section of the Woolwich Beds here, where not masked by overgrowth, shows a Cyrena-bed distinctly separated by a stratum of clay from an Ostrea-bed. Springs of highly ferruginous water are seen in one or two places in the grounds, and an ancient bath-house attests the value set upon this water in past times.

After walking through the beautiful grounds of Bromley Palace, in which are some of the largest evergreens in the neighbourhood of London, the party proceeded by the path across the fields to Widmore Kiln. The section at With/lore is figured in the "Geology of the London Basin," 1872, p. 246 (1889, i. p. 221), and on p. 247 is described as follows :

{| class="wikitable"
|  || Soil. || 
|-
| LONDON CLAY || Grey and brown weathered Clay, at most || 3½
|-
|  LONDON CLAY  || Basement bed: Clayey Pebble-bed, the pebbles of black flint || ⅛ to ⅛
|-
| OLDHAVEN BEDS || Light-coloured (mostly nearly white) sand, with a few pebbles in the upper part, chiefly in one broken line, and a few thin clay-layers; below 8 feet from the top of these last are in force || 12 or more
|-
| OLDHAVEN (or WOOLICH?) BEDS || Dark bluish-grey clay, laminated, with a few very thin sandy layers, small pieces of leaves, wood (in the state of lignite) and iron pyrites || 9
|-
| OLDHAVEN (or WOOLICH?) BEDS || Sand, with layers of clay in fine alternations. At one part (in the trough) the top highly ferruginous; at another it seems to pass up into the clay, the lower part of which is then more sandy. Tabular concretionary masses of sandstone occur a few feet down, and still lower many good impressions of leaves have been found. Not bottomed || 26 or more
|}

The "dark bluish-grey clay" is probably peculiar to this section, Whitaker stating that he is unaware of any other place at which it is seen. A collection of well-preserved specimens of leaves from the Widmore Beds was in the possession of Mr. Coles Child in 1872, but now plant remains are rarely found. The President, W. Carruthers, F.R.S., determined the leaves found to belong to the sub-tropical Ficus and Cinamomunz, genera, it is worthy of remark, not represented in the London Clay of Sheppey, which contains a large flora of a tropical and subtropical character.

The various beds having been pointed out and described, the way was led to the eastern extremity of Sundridge Park, in which is situate the "Rock-pit," so well-known to geologists. The Sundridge "rock" is a conglomerate of shells and smooth oval flint pebbles, embedded in a calcareous matrix, and affords rough building-stones well adapted for rustic buildings, to which its variegated surface adds picturesqueness, as is exemplified by the Chiselhurst Lodge of Sundridge Park. In a very short time ''Ostrea pulchra,'' ''Pectunculus Plumsteadiensis'', ''Cyrena cuneiformis'', ''C. deperdita'', ''Cerithium funatum'', and ''Melania inquinata'' were found.

At no great distance to the east of Sundridge Park a section shows Chalk with overlying Thanet Sands, thus revealing the Chalk "inlier," which extends from west to east for upwards of three miles, surrounded by the Lower Eocene. Of this inlier, Whitaker writes at p. 65 of "The Geology of the London Basin, 1872,"—"The valley that runs through Sundridge, Camden, and Bickley Parks, between Bromley and Chiselhurst, lays bare an outcrop of this formation (Thanet Sands), and the Chalk, in the form of an inlier, that is to say, surrounded on all sides by a higher formation. This exposure of the Thanet Sands, within the area of the overlying Woolwich Beds, and at so high a level, is owing to a slight upheaval of the beds, which has brought the lower formation within reach of the common forces of denudation; the outcrop extends from the north-western part of Sundridge Park, through Camden and Bickley Parks."

The line of the railway was then crossed, and on its northern side an exposure of Thanet Sands, Woolwich Beds, and Oldhaven Beds was found in a recently formed road. The section having a sloping face, the pebbles which have rolled down from the uppermost bed cover a considerable portion of the surface, and thus the Pebble-bed appears to be much thicker than it is, and the Sands correspondingly less important than is really the case.

Still going eastward the party were conducted to the entrance to the Chalk Caves of Camden Park.<ref>Figured in Whitaker, Geol. London, i, 1889, p. 116.</ref> Lower beds are exposed here, the Chalk being seen to a depth of from 15 to 16 feet. The usual bed of green-coated flint separates the Chalk from the Thanet Sands itbov, which extend to the soil at the top of the section. The Chalk at this place, obviously the uppermost bed of the Chalk of West Kent, appears to be harder and more compact than the similar bed at other sections. One bed, not much below the top, is so continuous and compact that it forms an immense unjointed slab, constituting a continuous roof to the caves, or rather galleries, which extend for a long distance under Camden Park. These, galleries, driven under grciund for quarrying purposes, consist of longitudinal and transverse workings, leaving great masses as pillars for the support of the roof. Sponges are more than usually abundant in the Chalk of this place, and some good specimens were obtained on this occasion.

In the work by Charles Barrois, "Recherches sur le Terrain Cretace Superieur de l'Angleterre et de l'Irlande" (1876), the various beds named in the classification of the Chalk of this part of England by another of our Associates, Mr. Caleb Evans,<ref>"On Some Sections of the Chalk between Croydon and Oxted," by Caleb Evans, 8vo, London (Geol. Assoc.), 1870.</ref> have been correlated with the divisions of the Chalk generally which M. Barrois seeks to establish. This correlation is given at page 139 as follows:<ref>See also J. Morris, " The Chalk : Its Distribution and Sub-Divisions " Proc. Geol. Assoc., vol. viii. (1883), p. 208.</ref>

[[File:GA Image 0650.jpg|600px|Classification of the Chalk by Caleb Evans and C. Barrois]]

It will thus be seen that Mr' Barrois considers the highest Chalk in this part of England to be the second of his divisions, " Zone à Marsupites; " and at page 138 we find he states—" C'est dans cette région (Kent) que les zones à ''Holaster subglobosa'' et ''Belemnites Plenus'' acquièrent leur plus complet developpement. La zone a Belemnitelles n'est pas copnue dans cette pantie de l'Angleterre."

Exposures of all the beds, from the Upper Chalk to the London Clay, had been seen. It remained to ascend to the high ground of Camden Park, which affords extensive views over the district, and a good standpoint from which to note the physical features of this part of Kent.

==References ==

===Maps===
Ordnance Survey. Geological—Sheet 6. 8s 6d.

New Ordnance Survey—Sheet 271. 1s.

Stanford's Geol. London, 5s.
===Book===
Whitaker, Geol. London. 1889. 2 vols. x 1s.

== Footnotes ==

[[Category:Geologists' Association excursions]]