Warwick Road/Casino slip at Southend. The following notes were made on the rotational slump above the Westcliff Casino and south of Warwick Road when it was both freshly formed and helpfully dried-out the autumn of 2001. One can still see the cliff beyond protective fencing and it will probably enlarge towards the west during later flash floods. There are two insitu cliff faces separated by slumped London Clay and all three areas showed a single band of sepatarian calcite (calcium carbonate) concretions with originally pyrite (iron sulphide) smaller nodules between or perhaps just above them. The septaria had a tabular base and a thickness of 0.11 metres, 1.5 m below the ‘Ice Age’ gravels capping the London Clay on the west side featuring a spring lubricating the slump. An equal thickness of clean London Clay was exposed below the septaria on both sides of the area. The London Clay and concretions had evidently been weathered inwards from the cliff face to a pale white or grey colour making them look like drift from a distance and the only later deposits were 0.3 m of brown gravel on the west scar and 1.4 m of finer gravel on the east scar also capped by old bricks etc. The original elevation of the concretion band was determined later by relating it to the undeformed concrete steps on the east side. A spot height on the road above these steps is recorded on the Ordance Survey maps as 31.0 m above mean sea-level, and using a crude level on the steps the concretions were recorded at 23.5 m. Probably 24 m would be a more realistic estimate. Thus although the slip is on one of the highest points on both the cliff top road and the London Clay surface there must still be five metres of porous gravel or other 'ice age' deposits represented by the grassy slope above the slipped face with the spring in it. This water doubtless comes from the old urban hinterland at this depth and bursts out to lubricate the clay fracture planes during flash flooding. There did not seem to be any obvious change in that particular urban environment since the Victorian times when this particular port of the cliff had been made into a stable public garden with trees.

The original pyrite nodules on the eastern scar were in the form of solid red iron oxide (haematite) and on the wetter west side they were decayed to yellow iron and gyspum (calcium sulphate). The primary characteristics of the associated calcite septarian concretions consisted of a relatively fine-grained quartz fabric for concretions in the upper London Clay, with some original carbonaceous laminae largely removed by marine animals in the London Clay sea producing horizontal burrows of up to 8 mm diameter, and smaller polygonal patterns. In thin section there were unusually large trochoidal foraminifera preserved to a diameter of 0.30 mm and a height of 0.18 mm as original calcite shells. They were entirely filled with what had originally been pyrite. There were also solid triangular limonite calcite and rod-like shells of 0.40 mm diameter and crustacean valves of ostracods. A search was then made for other sites in the Southend area showing the same shapes of common microfossils in this fine, largely bioturbated clay matrix. Septaria from the Cliffs Pavilion cliff 400 m to the west and in or around the Bandstand Cliff 400 m to the east had been collected before from up to 20 m above mean sea-level and they were all of a more sandy clay composition, with different or absent microfossils. It was therefore deduced that the Warwick Road cliff was stratigraphically higher as well as merely higher in altitude, despite well record evidence of a steeper dip towards the east along the coast. The highest septaria were probably around 125 m above the base of the London Clay and did not match the sandy highest septaria in the opposite cliffs on the Isle of Sheppey, which may well represent the other Southend levels.

Looking further away there was a small slip on Love Lane, opposite High Mead, near Rayleigh Station, showing the same type of septaria in December 2002. In this case it was wet sand unit within the Eocene London Clay Formation (also termed basal “Claygate Beds” without implying an age difference) which probably supplied water to the steep slope previously produced by the greater stability of more sandy layers of the London Clay. The concretions were however just below this sand and had a relatively fine-grained texture; but with more smaller, less complete pyrite cementation of the foraminifera. They were matched more exactly to loose samples from the A1015 road next to the church at Saffory Close in Eastwood and South Shoebury Common beach.