View source for Excursion to Tilgate Forest, Cuckfield, and Hayward's Heath. (Central elevations of The Weald.) Saturday, May 20th, 1882 - Geologists' Association excursion

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'''Director: J. Logan Lobley, F.G.S. (Report by The Director.) (Proc. Vol. vii. p. 372.)'''

Three Bridges Station, at which the members assembled, is a well-situated point of departure from which to cross the central elevations of the Weald between London and Brighton, the junction of the Weald Clay and the Hastings Sands crossing the railway at this place. Immediately the Weald Clay is left behind dense woods are entered, and these, with the rising sandy ground, leave no room for doubt that the Forest District has been reached. The coincidence of the boundary between the Weald Clay and the Hastings Sands with that between the flat cultivated fields and the wooded rising ground is very remarkable.

A walk of a mile brought the party to a quarry by the side of the railway, affording a good exposure of the uppermost beds of the Hastings Sands, the subdivisions of which were described. They are briefly as follows:

{| class="wikitable"
! Subdivisions !! 
|-
| Upper Tunbridge-Wells Sands (with Tilgate Grit), in two parts separated by Cuckfield Clay (local, 15 feet) || 100 to 200 feet
|-
| Grinstead Clay || 10 to 80 feet
|-
| Lower Tunbridge-Wells Sands || 50 to 100 feet
|-
| Wadhurst Clay (with Clay Ironstone) || 120 to 150 feet
|-
| Ashdown Sands || 150 to 500 feet
|-
| Fairlight Clays (local, 360 feet) || 
|}

The Upper Tunbridge-Wells Sands, as seen in the Tilgate district, are very variable, containing, in some places, as at this quarry, beds of good, though not very hard, building-stone, bands of clays, and pockets of hard nodular calcareous blocks with ferruginous coatings. At other places they are simply compacted sands, sometimes beautifully white glass-sands, with thin shell sandstones, and at others, as Cuckfield, they contain the hard calcareo-siliceous stone known as Tilgate Grit, with argillaceous beds, Cuckfield Clay.

Leaving this quarry higher ground was traversed, and a picturesque route through the forest led to Cinderbanks, where the path descends and crosses the railway to a secluded hollow, in which one of the head waters of the Mole meanders over Grinstead Clay, which has a maximum thickness of about fifty feet in the neighbourhood of East Grinstead. This Clay has a general resemblance to the Wadhurst Clay, below the Lower Tunbridge-Wells Sands, but does not appear to contain so much ironstone. As the land rises rapidly, the Lower Tunbridge-Wells Sands,-are not seen, and the Clay occupies but a very narrow area where the stream has cut through the Sands.

Hence the party made their way to Balcombe Down, 471 feet above sea-level, and a commanding position on the great spoil-heap over Balcombe tunnel (the summit of the London and Brighton Railway) was taken up. The Director explained that the principal anticlinal axis of the Weald had now been reached, the same axis as that visited by the Association in July, 1879 (see Proc., vol. vi.). Topley has clearly shown by the map at the end of the "Geology of the Weald" that there are several anticlinals in the Wealden area having a general parallelism, but that one passing through Crowborough Beacon, Ashdown Forest, Balcombe Down, St. Leonards Forest, and so on to Horsham appears to be the chief, passing, as it does, through the central highlands, and being coincident, at a little east of Balcombe Down, with the water-parting of three hydrographical areas, those of the Medway, the Mole, and the Ouse. An extensive and varied view over a large portion of the Forest District of the Weald rewarded the geologists.

All now proceeded westwards along the anticlinal by a high level road coincident with the water-shed of the Ouse and the Mole. From Handcross the London and Brighton high road was followed. This road, running southwards, descends by Staple-field Green to the Ouse Valley, at the bottom of which, and rising on the south side to some elevation, occurs a remarkable outlier of Weald Clay running east and west for about six miles. This is caused by the folding of the strata, which dip from the anticlinal at Handcross, and present the Weald Clay along a synclinal at a lower level than the Tunbridge-Wells Sands, which are, however, lifted up again on the south by a fault.

The strata to the south are much faulted, and the Tunbridge Wells Sands, the Grinstead Clay, and patches of Weald Clay form the ground in a most irregular manner. Near the summit of the southern side of the valley the Tunbridge-Wells Sands afford a fine white glass-sand without any cementing material, though at a few yards distance a shelly sandstone is visible.

Some distance further, at a higher level, at Whiteman's Green, near Cuckfield, the famous "Iguanodon Quarry " of Mantel] is reached, where the Tilgate Grit, with a conglomerate, is covered with a patch of Weald Clay. The Iguanodon tooth, discovered here in 1822 by Mrs. Mantell, led to the determination of this animal, whose bones had been observed some years previously by William Smith. Fragments of bone of this dinosaur are frequently found in the quarry. The town of Cuckfield was next passed through, and the party assembled in the park overlooking the Southern Weald Vale, commanding a fine view of the range of the South Downs, with Ditchling Beacon, the Devil's Dyke, and Chanctonbury Ring. Returning to Cuckfield, a further walk to Hayward's Heath Station, over very remarkable ripple-marked Wealden flagstones, terminated the day's proceedings.

[An excursion confined to the Hastings Sands district of East Grinstead and West Hoathly took place on June 27th, 2885, and is reported in Proc., vol. ix. p. 217. In that described below the southern boundary of the Weald district was reached.]

[[Category:Geologists' Association excursions]]