Earth heritage in the Little Ouse valley, with chalk springs and river terraces
Zoom in to the Google Map to find the points of interest.
St Helen’s Well (Tanner’s Well) is a natural spring in the amphitheatre setting of an old chalk and flint pit. It is sited just east of the hamlet of Santon in the Little Ouse valley. Water rises here directly from the Chalk bedrock. The Mediaeval site of St Helen’s Church is an interesting historical feature close by, marked by hummocky ground west of the quarry (see map).
St Helen’s Chalk Pit.
The historic site of St Helen’s Well itself is gone, destroyed by the chalk pit, but it would have centred on a valley-side spring. The same water bubbles up here today as it did in Mediaeval times, where the slope of the valley side intercepts the local water table in the bedrock.
Chalk pebbles beside the natural spring.
Chalk is the bedrock underlying the Brecks. It is about 90 million years old in the Santon area, and belongs to the Turonian Stage (first identified at Tours, in France). It was laid down in a subtropical sea in a ‘greenhouse’ world, with no ice at the poles – something to think about. The beds here are a similar horizon to those mined for flint at Grimes Graves.
A fossil Spondylus shell, typical of the local Chalk. [Image courtesy BGS GeoScenic P549457]
A map of Western Europe in late Cretaceous times. [Image courtesy Stephanie Hartick]
The pit was dug for chalk and flint in the 19th century, and had an access canal for barges, which you can see entering the pit under the railway line. The chalk was transported away by river, and used to build roads, embankments and the nearby railway (opened 1845). Hard blocks of ‘clunch’ were used to build the columns in St Mary’s Church, Thetford, and doubtless other local buildings and walls. The flint was sold for building purposes and making gunflints.
Chalk clunch walling at Earl Street, Thetford.
St Helen’s Church once stood just west of the chalk pit, and is marked by hummocky ground and an interpretation panel. The site gives fine views over the Little Ouse valley, including the remains of river terraces. These are remnants of former floodplains, laid down during cold climatic periods when huge volumes of meltwater were seasonally available to shift sediment from exposed, barely vegetated land surfaces down into valleys. Floodplains built up, but were later dissected by river downcutting, to leave isolated benches along the valley sides: these are the terraces. Successive cold periods led to a ‘staircase’ of terraces in the Little Ouse valley, sides, each visible as spreads of sand and gravel with subtle breaks of slope between them. The British Geological Survey has identified a sequence of three here. Can you spot some of them in the terrain round Little Lodge Farm?
The view from St Helen’s Chapel site, looking south.
River terraces are the isolated remnants of former floodplains. [Image usage courtesy Terranova274 CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0), via Wikimedia Commons]
Examples of Palaeolithic flint tools have been found in the gravels at St Helen’s Pit. As at other sites in the Little Ouse valley such as Broomhill (another Trail site), these are likely to have been incorporated into the gravels after being washed off a land surface where they had been discarded, or having been drawn into them by the churning effects of frost action.
An oval handaxe in fresh-looking condition, collected by Rev. H. Tyrell Green of Santon Downham. [Photo courtesy Wisbech Museum 1937.17.8.]
The site is on public access land and marked on Ordnance Survey Explorer map no.229 ‘Thetford Forest in The Brecks’ (c.TL 840 874). It is best approached from the picnic areas at Two Mile Bottom (TL 848 877) or Santon (TL 826 874). Take special care on the A134, as it is a fast, busy road.