View source for Excursion to Redhill and Crawley (Northern valley of the Weald). Saturday, May 6th, 1882 - Geologists' Association excursion

{{Template:GA excursions1860-1890}}

[[File:GA_Image_0479.jpg|thumb|Figure 45 Section of the Northern Valley of the Weald. (About 9 Miles.)]]

[[File:GA_Image_0480.jpg|thumb|Figure 46 Section of the central elevation of the Weald. (About 12 Miles.)]]

'''Director: J. Logan Lobley, F.G.S. (Report by The Director). (Proc. Vol. vii. p. 369).'''

[The next five reports, a second series of excursions to the Wealden area, describe the geology of the country between Redhill and Brighton. (See also pp. 35-44.)]

On arriving at Redhill Junction Station the party made their way to Redhill Common, on the summit of a hill that rises boldly on the south of the town to an elevation of 475 feet above the sea-level, and affords a complete view of the district to be observed. The central elevated region (the Forest District), extending east and west, rises from a low plain, lying along its northern side, while a similar vale skirts it on the south, both these vales being overlooked on the north and south respectively by elevations which form the bounding escarpments of the Wealden area. The central- elevated district consists of the Hastings Sands, the parallel vales to the north and south of the Weald Clay, and the bounding escarpments of the entire area of the Lower Greensand and the Chalk, the latter forming the North and South Downs. Although the ranges of the Chalk Downs are of about equal general elevation, the Lower Greensand on the south forms features insignificant compared to those of that formation on the north, which become in many places bold hills, and in one case, that of Leith Hill, surpass even the Downs in altitude.

Redhill Common is on the Lower Greensand escarpment, and from its commanding elevation, looking northwards, the parallel Chalk escarpment of the North Downs is well seen for a long distance running east and west, the nearest point being about a mile and a-half distant across the beautiful intermediate Cretaceous valley. Here the Lower Greensand escarpment is cut across by a deep valley, through which the London and Brighton high-road and railway run. This gorge is in line with a fault crossing the longitudinal valley, and extending to the Chalk escarpment at the Merstham tunnel.

Turning to the south, the view from Redhill Common extends over the whole Weald-Clay vale to the central elevations. The South Downs and Chanctonbury Ring are distinctly seen, and thus the !entire breadth of the Wealden area from the North to the South Downs is visible. The highest part of the common consists of the Folkestone Beds of the Lower Greensand, which have the usual dip to the north, and pass under the Gault in the valley, but on the face of the escarpment the underlying Sandgate Beds, the Hythe Beds, and lower still, the Atherfield Clay, occur in regular sequence. A very fine exposure of the Folkestone Beds is seen in the large sand pits on the eastern side of the hill, where these beds consist of brightly coloured sands, chiefly of a beautiful deep pink, ranging to crimson. At about half a mile to the east, at the base of the escarpment, the party visited a section of Atherfield Clay, worked here for bricks, in conjunction with Weald Clay from the adjacent Earlswood Common, the commencement of the northern Weald plain. This common was now traversed, the wet and boggy ground bearing witness of the changed character of the underlying strata'. It was pointed out that the slight ridges noticeable on this common were due to thin bands of limestone, which occur in the Weald Clay. The limestone, where seen, is partly decomposed, but gives evidence of its fresh-water origin by yielding ''Paludina''. Topley ("Geology of the Weald," p. 102) gives the following particulars of the subordinate beds of limestone and sand found at different horizons in the Weald Clay, the maximum thickness of which near Leith Hill is estimated at from 900 to 1,000 feet:

:7 Sand.

:6 Limestone, " Sussex Marble " (large Paludina).

:5 Sand and Sandstone, with Calcareous Grit.

:4 Limestone (large Paludina).

:3 Limestone (small Paludina).

:2 Sand and Sandstone.

:Horsham Stone.

Of these, the lowest, the Horsham Stone, is the most important.

The old coach road to Brighton was now gained, and followed for the remainder of the journey to Crawley. Another of the limestone-based ridges was crossed south of Earlswood and Petridge Common, and still another at Horley Lodge, the latter forming the water-shed between two branches of the Mole. After these elevations are passed the Weald Clay forms a plain. This flat country, destitute of sections, though well wooded and cultivated, became somewhat wearisome, but nevertheless nearly the whole party continued to walk through Honey to the little old town of Crawley, passing over, on the way, the county-boundary between Surrey and Sussex.<ref> Sheet 76 of the Horizontal Sections of the Geological Survey crosses the Weald District from near Brighton to the North Downs near Merstham, Surrey; its line of direction being almost identical with that of this series of Weald excursions.</ref>

==References==

===Maps===

Ordnance Survey. - Geological. Sheets 8 and 9. 8s. 6d. each.

New Ordnance Survey. Sheets 286 and 302. is. each. 

===Books===

W. Topley, Geology of the Weald, 8vo, London (Geol. Surv.). 1875. 2 8s.

Dixon, F., Geology of Sussex. 1850; and ed. 2, 1878.

See also Weald Series of Excursions, pp. 35-44.

[[Category:Geologists' Association excursions]]