The geology of the area lying between Downham Market and the Cambridgeshire border is relatively straightforward. Approaching Downham from the west gives a clear understanding of why settlement has grown up on the greensand escarpment that rises some forty metres above the historically poorly drained lands of the Fens. It is easy to appreciate the advantages of the route followed by the A10 compared to one a few miles to the west.
South of Downham, Hilgay stands on an outcrop of lower greensand while most of the rest of the area, including Southery, Welney and all but the most eastern parts of Fordham, is underlain by Kimmeridge clay. A narrow band of upper greensand is encountered running north-south across the road between Southery and Feltwell though this is not defined on the surface because of the overlying sediments. This quickly gives way to the chalk as Feltwell is approached and the land rises significantly.
Kimmeridge clay is of interest because in places, such as Dorset, it contains oil shale. William Smith first noted on his geological map of the county (1819) that the underlying clay in west Norfolk was "part slaty and bituminous as at Kimmeridge in Dorset". Rose (1835) subsequently recorded inflammable shales "that burned like cannel coal" in the Kimmeridge Clay in a brickpit at Southery, and oil seepages that were supposedly derived from the Kimmeridge Clay were observed in drainage ditches a few kilometres away at Setchey. These seepages and the prospect of finding oil shales comparable to those that had been worked at Kimmeridge, combined with the urgent need to find additional sources of oil within the UK, caused oil-shale exploration to begin in Norfolk during World War I. A pilot operation began at Setchey in 1916. It was believed that at least three seams of oil shale 1.8m thick were present and that two of these could be retorted to yield more than 50 gallons of oil per ton of shale. The exploration was not a success but a rise in the price of oil may bring these deposits back into commercial consideration at some point in the future.
The Kimmeridge clays were laid down in the Upper Jurassic period about 150 million years ago. Lower greensand is a cretaceous rock formed around 115 million years ago and this was followed by the chalk 15 - 35 million years later. The same pattern of rocks can be seen running north east from Dorset to west Norfolk though the chalk in the Chilterns, for example, is of much greater elevation.
The Kimmeridge clay is rich in fossils. When the Relief Channel was under construction in the 1950s the excellent remains of an ichthyosaurus were unearthed at Stowbridge. The Times of 28 July 1958 attributes the discovery to Mr T Burton, a pump attendant.
Dr Forbes, assistant curator of the Sedgwick Museum in Cambridge unearthing the Stowbridge ichthyosaurus that lived in the Jurassic seas about 130 million years ago. The reptile’s head can be seen in the foreground and measures 1.2 metres in length, giving the reptile an overall length of about 7.2 metres. (The first ichthyosaurus ever discovered was found in Lower Lias rocks by Mary Anning, aged 12, at Lyme Regis in 1811)
The most recent geological period, the Quaternary, commenced some two million years ago and contains the last Ice Age. At its maximum extent in Britain, the Quaternary ice sheet reached as far south as the Thames basin and South Wales. Sea levels gradually rose as the ice retreated and the North Sea, after establishing Britain as an island about 7500BC, then settled at present levels around 3000BC. The southern half of a much more extensive ‘Wash’ became silted up and a peat layer of up to ten metres was created. It is into this swamp that many trees fell, creating the ‘bog oaks’ that have re-emerged as the peat has shrunk following the drainage in modern times.
Doggerland is a name coined for what is now a central part of the North Sea around the Dogger Bank. With Britain connected to mainland Europe animals and early man could roam freely across the land mass. Note the River Ouse. More information can be found at https://en.wikipedia.org/wiki/Doggerland
The area is drained principally by the Great Ouse and its tributaries Wissey and Little Ouse.
The River Great Ouse is 150 miles (240 km) in length which makes it the foremost navigation in East Anglia, and the fourth-longest river in the United Kingdom. The lower reaches of the Great Ouse have also been known as the Old West River and the Ely Ouse. The name Ouse is from the Celtic ‘udso’, and probably means simply ‘water’.
The river has several sources close to the villages of Syresham and Sulgrave in Northamptonshire. It flows through Brackley, Buckingham, Milton Keynes at Stony Stratford, Newport Pagnell, Olney, Bedford, St Neots, Godmanchester, Huntingdon, Hemingford Grey, St Ives, Ely, Littleport, Downham Market and enters The Wash at King's Lynn.
The River Wissey, also known as the Stoke River in the past, rises near Bradenham in Norfolk, flows through Necton, North Pickenham, South Pickenham, Great Cressingham, Ickburgh, Northwold and Stoke Ferry before joining the Great Ouse at Ouse Bridge, in the parish of Fordham The total length is close to 30 miles (50 km).
For much of its length, the Little Ouse River defines the boundary between Norfolk and Suffolk and, in its lower reaches, Norfolk and Cambridgeshire.
It rises east of Thelnetham, very close to the source of the River Waveney. The village with the curious name of Blo' Norton owes its name to the river - it was earlier known as Norton Bell-eau, from being situated near this 'fair stream'. The course continues through Rushford, Thetford, Brandon, and Hockwold. It joins the Great Ouse at Brandon Creek. The total length is about 40 miles (60 km). The river is currently navigable from the Great Ouse to a point two miles above Brandon. It has been known as the Brandon River in the past.
The most distinctive feature of the headwaters of the Little Ouse and the Waveney is the valley in which they flow; the Little Ouse westwards and the Waveney, eastwards. It has a broad, fenny bottom, lies at an altitude of up to 26 metres and both rivers rise in the fen alongside the B1113 road, between South Lopham and Redgrave. The explanation of this oddity is that the valley was formed not by these rivers but by water spilling from Lake Fenland, a periglacial lake of the Devensian glacial, fifteen to twenty thousand years ago. The ice sheet closed the natural drainage from the Vale of Pickering, the Humber and The Wash so that a lake of a complex shape formed in the Vale of Pickering, the Yorkshire Ouse valley, the lower Trent valley and the Fenland basin. This valley was its spillway into the southern North Sea basin, thence to the English Channel basin, which at the time, contained no sea. Reference to the appropriate Ordnance Survey map will quickly add some clarity to these details.
It is easy to think of the landscape around Downham as dull and featureless. Not so! Certainly, there are neither precipitous mountains nor jagged outcrops of rock but the evolution of the landscape that has led to the settlement of the area is fascinating nonetheless.
South of Downham and beyond the islands which attracted early settlement, the parishes of Hilgay and Southery extend across the fenlands to the Ouse and then to the Hundred Foot River as it adjoins the neighbouring parish of Welney.
The primary reason for the settlements of Hilgay and Southery is easy to appreciate even to the unpractised eye. The villages stand on higher land above the fenland that was created by the rise in sea level following the end of the last Ice Age. Gradually the sea level rose, Britain became an island, the Wash was formed and the Fens created. Settlers naturally sought out higher land and the islands of land, such as the hourglass-shaped island upon which Hilgay and Southery stand, proved attractive. A clear pattern of settlement had emerged by the Middle Ages as settlement concentrated on the Downham escarpment or the islands to the south.
The highest point in the parish of Hilgay lies just west of the top of Sandy Lane and is a fraction over twenty metres. Not high by any means but very significant in avoiding winter flooding on the marshy fenland that lies all around, save to the south west towards Modney Bridge. Much of Southery lies between the ten and fifteen metre contours.
Hilgay stands on the south bank of the river Wissey some two kilometres east of its confluence with the Ouse. It was in former times a busy route for the transfer of goods from Stoke Ferry, to King’s Lynn in particular. Many tons of sugar beet was carried by barge on the Wissey after the opening of the sugar factory at Wissington in 1925. Nowadays, the river is popular with holiday boats and many are moored along its banks.