Geology Notes – East Coast Curious

‘A Contribution to the Geological History of Suffolk. Part 1 by Suffolk Naturalists’ Society – Issuu’. Accessed 27 January 2022. https://issuu.com/suffolknaturalistssociety/docs/tsns13_4_a. – cement stone

Geological Evolution from PLA

The London Clay
The London Clay comprises brown and grey predominantly silty clays that
were deposited in a shallow sea, up to 100 m deep, that covered much of
south-east England during the Eocene Period. England had a warm
subtropical climate, with luxuriant rain forest and coastal mangrove swamps.
Large sluggish rivers carried sediment and plant debris out to sea, where it
settled and compacted on the sea floor. Plant debris, logs and branches, now
preserved as pyritised fossil wood, seeds and fruits, are. Many species of
sharks and other fish swam in the seas – the teeth of the sharks Carcharias
hopei, C. teretidens, Striatolamia macrota and Otodus obliquus, and fish
vertebrae can often be found washed out on the foreshore at both sites.
Other vertebrates, including turtles, have also been found. A microfauna of
diatoms, radiolarian and foraminifera, and a small, poor invertebrate (mostly
mollusc) fauna have been recorded. ¹

Cobbold’s Point, Beacon Hill, Wrabness, Pin Mill. West Rocks, Stone Bank, Cliff Foot. The Rocks, Waldringfield

Churches, Walton Castle, Harwich paving, other buildings

See S Dale letter re fossils.

See Hurst, Lawrance. ‘The Properties and Uses of Roman Cement’. Construction History 18 (2002): 21–35.

See Suffolk_Building_Stone_Atlas – Paleogene (a geologic period and system that spans 43 million years from the end of the Cretaceous Period 66 million years ago (Mya) to the beginning of the Neogene Period 23.03 Mya.)

Septaria were also used for making ‘Roman’ cement, for
example by William Lockwood at Lime Kiln Quay, Woodbridge see ‘THE SUFFOLK GEOCOAST THE LONDON CLAY OF NACTON AND HARKSTEAD SHORES by Suffolk Naturalists’ Society – Issuu’. Accessed 27 January 2022. https://issuu.com/suffolknaturalistssociety/docs/tsns48t.

Definition here.

Arnott:

At the foot of Felixstowe cliffs are large deposits of limestone nodules or Septaria which is a form of fossilized jelly-fish and it had been used from very early days as a building stone. 01 ford Castle and Chillesford and Wantisden Church Towers are built of it so that it must be unique to have buildings made of jelly-fish! This stone, called Rokstone,” formed a good natural protection for the coast, but the Trimley parishioners were already carting it away in 1500 for use in completing S. Mary’s Church Tower which was not then finished. Cardinal Wolsey, too, wanted the stone for his College at Ipswich and when he asked permission from the Lady of Manor to take it from Beacon Hill, Harwich, was bluntly refused on the grounds that its removal would undermine the cliff, although he got it in the end. In later years the demand for the stone much increased in connection with the manufacture of cement, a process which was patented in 1796. Works were started at Harwich and the stone dredged up by smacks off the West Rocks. In 1851, as many as 400 smacks were at work there, racing each other every morning and night to the Rocks and back. The dredgermen received about five shillings a ton for the stone which was considered a very profitable day’s work! The last of the Harwich cement 1 manufacturers, Pattrick, supplied some of the cement with t which the Tower Bridge, London, was built and on the proceeds erected a large house, known locally as ‘c Patr trick’s Folly,” overlooking the harbour.As a result of taking cement stone from Landguard spit and Felixstowe cliffs. large slices of land, together with two Martello Towers and a battery went into the sea. ²

Cement Kilns site has a good explanation of Roman Cement

General background and only source today

Dixon, Roger. ‘The Suffolk Geocoast the London Clay of Nacton and Harkstead Shores’ 48 (2012):

SOME UNUSUAL LOCAL BUILDING STONES Roger Dixon

Septaria
Calcareous mudstone concretions from the Eocene London Clay outcrop from
Bawdsey southwards along the coast and up the Deben and Orwell estuaries
on the foreshore. They were also obtained offshore by dredging, and were
used at one time for the manufacture of Roman Cement. Impressions and
borings by marine organisms can be seen in many church fabric septaria
blocks and indicate their provenance. It is widely used in Suffolk’s Norman
churches, and indeed appears to be the Norman’s ‘local stone of preference’,
most often used in conjunction with Caen stone.
The Leper Chapel, previously a Saxon church, is all that remains of St.
James’ Hospital and with Greyfriars, is all that is left of the medieval city of
Dunwich. Founded by Richard I at the end of the c. 12th, it was built outside
the city itself for fear of the disease. Leprosy was ‘imported’, probably during
the Crusades, because Dunwich was a thriving medieval port. The stylish
Norman/Early English architecture can still be clearly seen, with fine carved
Caen stone windows and arches. Of particular note, seen in the external north
wall and internal east end, is the fine decorative contrast between imported
pale Caen limestone and darker brown septaria, often over 30 cm across and
badly weathered.
There are many other examples of Norman and Medieval septaria churches
– Orford (and Orford Castle), Iken, Falkenham, Kirton and Melton Old
Church (which also contains the memorials and graves of geologists Searles
Valentine Wood and his son) are just a few. Unfortunately, septaria fracture
and weather easily and have been responsible for the crumbling and collapse
of many structures, as the churches of Orford, Kirton, Bawdsey and, most
dramatically, Alderton testify. Repair and restoration has been a constant
theme!

www.geoessex.org.uk/wp-content/uploads/2020/06/geoessex_factsheet_6_-_septarian_nodules.pdf

1
‘THE SUFFOLK GEOCOAST THE LONDON CLAY OF NACTON AND HARKSTEAD SHORES by Suffolk Naturalists’ Society – Issuu’. Accessed 27 January 2022. https://issuu.com/suffolknaturalistssociety/docs/tsns48t.
2
W.G.Arnott (1950). Suffolk estuary : the story of the river Deben.

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