Geology Site Account
Pickets Lock and Angel Road Pits (site of) (Lee Valley Arctic Bed), PONDERS END, London Borough of Enfield, TQ352930, Historical site only
Sites of geological interest with disused pits that have provided information about the underlying geology, particularly the 'Lee Valley Arctic Bed'. Any further major excavations in the area should be recorded.
Description and history of the sites
At the beginning of the 20th century, Essex amateur geologist Samuel Hazzledine Warren was collecting Ice Age fossil mammal bones from gravel pits in the terrace gravels of the River Lea at Ponders End, just over the border of Essex. The fossils included bones of mammoth, woolly rhinoceros, reindeer and arctic lemming and dated from the most recent glacial stage (the Devensian), a time of extreme cold when, at its maximum extent, the ice sheet reached as far south as Norfolk.
Of most interest, however, was Warren’s discovery of peat ‘rafts’ sandwiched between layers of gravel which were found to contain cold climate or ‘full glacial’ plants assemblages and referred to collectively as the ‘Lea Valley Arctic Bed’. So unusual and important was this discovery that this period of the Ice age has been referred to as the ‘Ponders End Stage’.
The Arctic Bed was carbon-dated to approximately 28,000 years ago. It contained a distinctive vegetation which has no precise modern equivalent. Known as ‘tundra steppe’ this grassy vegetation covered much of Europe, northern Asia and North America during the Devensian stage (100,000 to 10,000 years ago) and was the main habitat and diet of the woolly mammoth. The plants of this dry grassland were faster growing and more abundant than today’s tundra plants and in addition to various species of grasses they included sedges, small shrubs and many herbaceous plants. Large areas of the landscape were treeless but dwarf birch and willow, and other trees such as larch, occurred locally.
The Arctic Bed was first discovered at the Pickett’s Lock Pit an extensive gravel pit owned by the Great Eastern Railway Company. The company were proud of the fossils found in the pit and had several mammoth tusks, teeth and various limb bones on permanent display in the Board Room at Liverpool Street Station, the London Terminus of the Great Eastern Railway. This small museum was visited by the Geologists’ Association in 1911 when it was reported that the largest tusk on display was 5 ft. 6 inches long and the collection included a 2 ft. long mammoth scapula.
The Pickett’s Lock Pit was next to the creosoting works of the Great Eastern Railway Company. Warren described the pit as having a floor of London Clay, above which was a maximum of 18 feet of current-bedded gravel and sand with a capping of 4 feet of brickearth. The rafts of Arctic Bed were usually detached blocks, between one and two feet thick, found near the base of the gravel and much broken up and disturbed. Sometimes they could be seen in continuous sections for 20 or 30 yards. Occasionally masses or tablets of the bed were inclined at a considerable angle and seen to be thrust over one another, an indication that they were frozen at the time this happened. The bed contained not only the seeds and leaves of plants but also freshwater molluscs and the wing cases of beetles. Some mammal bones were found within the Arctic Bed, others beneath or above it. Warren Also stated that the bed “in certain spots assumed a deep blue-black colour, was greasy to the touch, and emitted a fetid odour when freshly dug”. The second place where Warren discovered the Arctic Bed was the Angel Road Pit, a large excavation belonging to the North London Ballast Company which also yielded mammoth bones and teeth and pieces of reindeer antler from the gravel. The pit was said by Warren to be close to Angel Road Station and about a mile and a half lower down the valley than the Pickett’s Lock Pit. He described seeing here “an admirable section of the Arctic Bed” similar to that occurring at the Pickett’s Lock Pit, which was “particularly rich in seeds”. Examination of specimens of the Arctic Bed from this pit in later years has revealed the presence of small cylindrical objects with rounded ends which have been identified as the droppings of arctic lemmings. Also, discrete patches of mammal remains have been found which have been interpreted as owl pellets. These include bones and teeth of arctic lemming in an excellent state of preservation.
The exact location of the pits is not clear and different geologists over the years have given different grid references. However, using Warren’s original descriptions, and the map in his 1916 paper, it appears that the Pickett’s Lock Pit was on the site now occupied by the Leaside Golf Course (TQ 360 940) and the lake here was originally a gravel pit. The Angel Road Pit was an extensive excavation just north of Angel Road Station and the northern part of the pit was approximately where the Montagu Road Recreation Ground now is (TQ 352 930).
The identification of a large number of species from the Arctic Bed was largely due to Warren’s painstaking efforts. Back at his home in Loughton, he spent a considerable amount of time examining the samples collected. The method he adopted was to wash the material in water, to strain it through wire gauze, and then to spread the washed material out under water in white porcelain photographic dishes. After picking out everything determinable he submitted the different classes of fossil remains to specialists in the Natural History Museum.
Warren also found the Arctic Bed in the Temple Mills Pit, Stratford and at Nazeing in Essex (see separate site records). Other sites included Hedge Lane, Edmonton (TQ 325 929 - also now a recreation ground).
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Reference: Warren 1911, Warren 1912, Warren 1916, Stuart 1982 (p.101,102), Wymer 1985 (p.301-302).
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