Excursion to Watford, June 23rd, 1870 - 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: John Hopkinson, F.G.S. (Report By The Director.) (Proc. Vol. ii. p. 43.)
On alighting at Bushey Station the party examined the Chalk-pit close to the railway. A good section of the Upper Chalk, on which Watford is situated, is here seen, and overlying it, a pebble-bed of the Woolwich and Reading Series has recently been exposed. This bed completely thins out in the pit, and is succeeded by clay-drift and sandy gravel which repose, in other parts of the pit, immediately on the chalk. The Chalk Hill Pit, which furnished instructive examples of "pipes," was next noticed, and then the party proceeded to Watford Heath Kiln, where they were joined by Mr. W. T. Stone, who showed the sections then exposed, and explained how they varied in parts of the pit not now worked. Professor Morris had previously explained the general features of the country, especially with reference to the form of the ground and general contour of the hills, as caused by denudation acting on what were originally lines of weakness.
The London Clay, with its basement-bed, and between it and the Chalk a series of beds of sand and clay (with associated pebble-beds), belonging to the Woolwich and Reading series, are here seen. The following section is slightly altered from one given by Mr. Whitaker, in the " Memoirs of the Geological Survey" (No. 7), and reprinted in vol. iv.:
|London Clay||a. Brown clay, with selenite (no fossils)||9 0|
|Basement Bed||b. Brown sandy clay with selenite, numerous fossils, and at the bottom a layer of shells||5 0|
|c. Flint pebbles, with sharks' teeth (Lamma and Otodus)||0 3|
|d. "Brown sandy clay, more sandy than the upper bed, with iron sandstone, and a little ironstone at the base. At the top, here and there, a bed of soft clayey sandstone, bored by Lithodomi, from 6 inches to a foot thick"||7 0|
|e. Flint pebbles with oyster shells (Ostrea Bellovacina, Lam.)||0 3|
|Reading Beds||f Grey and mottled clay, with a few small pebbles||3 6|
|g Light-coloured sand||16 0|
|h. Sand, with beds of pebbles||9 0|
|i. Mixture of sand and clay, light coloured||3 0|
|Not shown—to the Chalk||6 0|
The shells at the bottom of the bed b are mostly in fragments, but several perfect specimens of the following, amongst other species, were collected: Aporrhais Sowerbyi, Mant., Cyprina Morrisii, Sow., Cyrena cuneiformis, Fer., Cytherea obliqua, Desh., Natica labellata, Lam., Nucula sp. (? margaritacea, Desh.), and Panopæa intermedia, Sow. But the best collection of fossils was made from some tabular masses, or concretions, of calcareo-argillaceous sandstone occurring at intervals in this bed, but not seen in place, the section from which they were obtained not having been worked for some time. In d, Mr. Stone has found several rare fossils, amongst which some turtle bones and a mammal's tooth (Hyracotherium leporinum, Owen) were particularly noticed.
On leaving this interesting pit the party proceeded to Bushey Kiln, where a section, somewhat similar, but with an additional bed of clay with "race," and showing in the lower portion alternating beds of sand and pebbles, is exposed.
At Berry Wood, near Aldenham, the Chalk is covered by thick beds of gravel, and by the roadside some Silurian and other boulders, one deeply scratched, attest the proximity of the Boulder Clay, which, in Bricket Wood, about three miles to the north, is from zo to 30 feet thick. In Berry Wood' is a chalk-pit abounding in the remains of sponges, surrounded by mere shells of flint, and containing spicules, Foraminifera, and Polyzoa, beautifully preserved.