GEOLOGY AND THE FORMER SAND QUARRY
The former quarry that is now Buckland Park Lake extracted sand from the Folkestone beds, the newest (‘highest’) part of the Lower Greensand series in the Cretaceous period. This was the age of the dinosaurs, though fossils of any kind are rare at Buckland Park.
The Folkestone formation in this area was laid down in a shallow sea close to the land. This can be seen in the patterns of current and cross-bedding in the exposed quarry faces. Tidal scour and deposition from inflowing rivers disturbed the neat process of sedimentation The sands at Buckland Park were laid down around 100-110 million years ago. There are two seams running roughly east-west across the site; a more northerly one with a coarse amber grain (reflecting its iron content), and a whiter and finer-grained southerly one.
The large lake has formed because excavation of the sand took the bottom of the quarry below the level of the local water table. Its depth ranges from 5m to 28m (93ft) depending on the profile of the sand pit when quarrying ceased. Rainfall on the chalk hills of the North Downs to the north of Buckland Park filters through the chalk and another band of newer sandstone below it (the Upper Greensand series, which in the past was quarried locally for ‘Reigate Stone’). The water then meets a thin band of impermeable clay (the Gault Clay) and emerges as springs. These in turn filter through the Folkestone beds and emerge as springs in the old quarry excavations below the low cliffs along the northern side of Buckland Park. While quarrying operations continued the workings were kept dry by pumping into the Shag Brook, a small stream running to the east of the site.
The lake started to form in about 1990, after sand extraction stopped. Water is retained because underneath the Folkestone beds and older layers of sandstone beneath it in the Upper Greensand, there is another thin layer of impermeable clay (the Atherfield Clay). This stops groundwater filtering away. Instead it drains out at the lower point at its southeast corner into the Shag Brook, which flows south to join the River Mole beyond Wonham Mill.
Sand was extracted from Buckland Park between 1925 and 1990. The site continued to process sand from the Tapwood Quarry north of the A25 until 2014. The sand resource at the site is of varying quality, depending on the grain size and the proportion of iron. The presence of iron can be seen in some of the orange colouring in the exposed cliffs. Though some of it is moderately ‘consolidated’ (as seen in the harder blocks in some of the cliffs) none of it is really hard. Unlike the Upper Greensand to the north is cannot be cut into blocks and used as a building stone.
The comparative softness of the un-quarried sand has allowed sand martins and solitary bees to create nesting holes of appropriate sizes in some of the exposed sandstone faces. Their near-vertical slope is a valuable defence against predators. These can be seen at various places on a walk around the lake, but for sand martin nest holes the best place is behind the picnic area next to the water-sports centre.
After excavation the sand was crushed and screened into products of varying sizes. The purest sand with the lowest iron content was used for high-end glass-making (e.g. jewellery – including Swarovski crystal, tableware and optical lenses) and specialist ceramics, including 400,000-volt super-grid pylon insulators for the National Grid. Sands with the finest grain-sizes was used for foundry moulding sand, notably in casting the manganese bronze propellers in the 1930s for the original Queen Elizabeth and Queen Mary liners at J. Stone & Co’s foundry at Deptford.
Other soft sand from the quarry was used for building mortar and as an additive to bitumen to form road asphalt. However, the material was too soft and free of pebbles, grit and broken shells for used as an aggregate in concrete. For that, ’sharp sand’ and shingle is required. In this region that is often obtained by seabed dredging in the English Channel and southern North Sea.
While still in operation the quarry was occasionally used as a film location, including providing an Antarctic landscape (!) for the Doctor Who Seeds of Doom serial in 1975. Pure white sand from the quarry went to Borehamwood Studios in 1966 and 1967 for filming the moonscape sequences of Stanley Kubrick’s 2001 A Space Odyssey. More recently the lake featured in an episode of ITV’s black comedy Inside No. 9.
PLANT LIFE
Disused quarry workings provide not just a glimpse of what is usually hidden beneath our feet but also the opportunity for recolonisation by both plants and animals. Including planted and translocated vegetation, 270 different plant species were recorded at Buckland Park Lake during 2022 in both man-made and more natural habitats across the site.
Rarities include the spring-flowering Large Bitter-cress and Alternate-leaved Golden-saxifrage in the boggy woodland where the lake drains into the Shag Brook. Pennyroyal, a type of mint, is present in large swathes along damp paths and lake margins. It was probably introduced as a grass-seed contaminant during landscaping but provides a rare opportunity to see this attractive and pleasantly fragrant species.
On sandy banks tiny heathland species like Sheep’s Sorrel, Early Forget-me-not, Changing Forget-me-not and both Common and Small Cudweed have gained a foothold, benefiting from the nutrient-poor soils of the Folkestone sands. In a longer sward around the lake scattered spikes of Common Spotted, Bee and Pyramidal Orchids appear during summer months.
Species that are the first colonisers of disturbed ground have exploited this opportunity along paths and in amenity areas. They include not just common and familiar “weeds” but large patches of Bugloss and Scarlet Pimpernel and more showy plants like Musk Mallow, Evening Primrose and Rosebay Willowherb.
The lake itself is home to yet another suite of plants that include many species of reed, rush and sedge, some planted or introduced during landscaping. Others, like Gypsywort, Nodding Bur-marigold, Brookline and Blue Water-speedwell have arisen naturally or been brought in by water fowl.
A significant issue for the lake that affects many other water bodies is the presence of Nuttall’s Waterweed and New Zealand Pigmyweed. Both these plants are invasive non-natives that form thick mats of vegetation which displace other species and reduce biodiversity. They are extremely difficult to eradicate once established which is why it is illegal to plant or release them in the wild.
These plants can survive for many weeks in wet suits and equipment used for water sports so it is important to check them all carefully after use to avoid transferring them from one site to another. But even the smallest fragment on the feet of water birds can spread these unwelcome plants. With over 20 species of water birds living in or visiting the lake it requires constant vigilance.
THE BIRDS AT BUCKLAND PARK LAKE
The ending of quarrying, the formation of the lake, and the return of vegetation to its range of habitats has encouraged an increasing number of bird species to the site, some to nest, some as a migration stopover and others for permanent residence. So far 85 species have been counted.
In addition to the usual waterfowl and everyday farmland birds, a number of significant species have been seen at or flying over Buckland Park Lake;
- Great white egret: rare, Though not on the red list as an endangered species (with declining breeding numbers or reduced breeding areas) it is amber listed as of moderate conservation concern. Only seen breeding in the UK within the last 15 years;
- Redpoll: probably lesser redpolls. Still abundant but declining in numbers and on the red list;
- Sand martin: also on the red list, and the iconic bird for this site, where the vertical soft sandy cliffs provide an ideal nesting site for this summer visitor;
- Yellow wagtail: another on the red list, being of high conservation concern. Now a scarce summer visitor to the UK.
The high value of Buckland Park lake as a supportive habitat of migration stopover for endangered species is also shown by the other birds on the red list seen there: swift, house martin, lapwing, linnet, starling, whimbrel, hobby, cuckoo, greenfinch and herring gull.
You will find two bird hides at the park, Finch and Swift, from which to spot birdlife.
