Eastchurch Gap on the Isle of Sheppey has been a regular field trip of this Society for many years. The stretch of coast between Warden Point to the East and Paddy's Point to the West is an area of high coastal erosion. It is here, that the London Clay topped by the Bagshot Sands are exposed in cliff sections some 20 to 30m high.
This view is from the top of Eastchurch Gap looking west (21 April 2002).
(Click on image for a larger picture, I think it's worth it!)
The junction (?), between the London Clay and the Bagshot Sands of the
Virginia Water Formation, is clearly visible as is also the slumping of
the cliff section due to erosion.
(?) assumed as viewed from a distance! I'm tempted to say unconformity because of the sharp contrast. Also, the facies above the junction is assumed to be Bagshot Sands, worth a close look next time, if there is a safe access!
Although the London Clay looks featureless, the stratigraphy appears to dip gently to the west and it is possible to detect divisions C, D, E of the London Clay in the cliff sections and on the foreshore. (By no means and easy task). This is, perhaps, the most continuous stratigraphy of the London Clay exposed naturally in one location, and combined with the high rate of erosion, facilitates the accumulation of a rich array of London Clay fossil fauna and flora on the foreshore. Even though the geology and fossils of the area have been well documented, this site is well worth a regular visit as it continues to yield quality fossils. (Stratigraphic Reference)
Pictured here are a few of our club members searching the foreshore. (I
never knew we had so many shrinking violets, not one looking to camera).
If you look closely you will see a few house bricks, concrete, and
other man-made artifacts. These are the remnants of homes that once were
on the cliffs above, and bear testament to the rapid erosion (and probably
indiscriminate dumping).
Some 10 members of the Society roamed the foreshore. There may have been more as it is easy to wander of into the distance collecting. Most returned looking like beet-roots! (Did you not heed my warning about UV cream?). It was hot and sunny day.
A Nautiloid of approximately 20cm in diameter and found by David Turner.
These are not an uncommon find for this location. However, their fossilization
contains a high percentage of pyrite which is unstable and leads to rapid
deterioration once exposed. Most means of treatment only delay the inevitable
decay to dust.
Gypsum,
Selenite, CaSO4, Calcium Sulphate.
This specimen was collected from the slumped clay between Eastchurch Gap and Warden Point.
The selenite is believed to have formed in the clay by the decomposition
of pyrite to form sulphuric acid that reacted with calcareous fossils
to form CaSO4.
Baryte
crystals on a Calcite (olive green) lining inside a septarian nodule from
Sheppey. (x 2.5 Image).
Baryte (BaSO4), Barium sulphate.
It is thought that the Barium was sourced from the primary deposits of the clay. The sulphate having formed by the reaction with the acid derived from the pyrite decay. ( I must say that I'd like to know where all the iron and sulphur comes from to form the pyrite and how so many fossils become pyritized?)
Another
nodule with an inclusion of Baryte, but in a different form to that above.
The 'Septarian Nodules' are concretions believed to have formed in the clay from concentrations of mineral matter during diagenesis. The name septarian comes from the way the nodule is divided into sections by fractures filled with calcite and other minerals.
These from Sheppey were originally called Cement Stones and collected over two hundred years ago for the manufacture of Roman Cement. (I think this is just a trade name and does not refer to the way Romans made cement 2000 years previous.) The long history of fossil collecting from this classic site started with the gatherers of the nodules. They also collected any fossils they came across and subsidized their wages by selling them to collectors.
One of our members spent the whole trip 'smacking nodules' and went home with a heavy load. (Are we making cement Ron, pray why are we sending them to the USA, swaps?)
The Copperas industry! Pyrite was also collected on a commercial scale in olden times and decomposed to form ferrous sulphate for the tanning industry.
(Bermondsey has a long association with tanning, and the locals were given a peculiar nickname by other Londoners, because of what they also collected for the tanning industry. [There is a full contemporary account (1850's) in Mayhew's Characters edited by Peter Quennell published by Spring Books, it's a painful book to read because of the emotions it raises.] In all honesty, I can say that there is no smell that surpasses (maybe equals) a Fell Monger's Yard on a hot day. Probably similarly to the smell of London during the height of the plague in the 1660's. In another corner of Bermondsey you could encounter the counterbalance with a wonderful aroma of the 'Smoking Sheds' (Herring, Mackerel & Haddock) which used to be to the rear of Guys Hospital. A smell that now sadly is almost non-existent in Britain, and which I last came across whilst studying Geology somewhere on the NE coast in the early 1990's)
There is an account of the Cement Stone and Copperas Industries in ESSEX ROCK by Gerald Lucy, however, this is specific to Essex and naturally makes no reference of Sheppey.
Other references:
George, W 1984a A short account of
the Cement Stone Industry of the Isle of
Sheppey,
Kent
Tertiary
Research, 5(4): 165-168. Leiden.
George,
W. 1984b A short account of the Copperas Industry
of the Isle of Sheppey,
Kent.
Tertiary
Research, 5(4): 169-172. Leiden.
You could even talk to Bill (W. George) on almost any club night as he is one of our members and a real gentleman!
(Many thanks to Sandra & Bob Blackburn for the pictures taken at Sheppey on the day.)
Report Archive (R Coleman 27 April 2002)