Geology Site Account

Historical site only

During construction of the A127 Southend Arterial Road in the early 1920s, road cuttings either side of the Ingrebourne valley exposed sections through Ice Age deposits that demonstrated beyond doubt that this valley was occupied by a glacier during the coldest period of the Ice Age. The road cutting on the eastern side of the valley is just east of the present Hall Lane flyover (TQ 565 890) and in 1922 it revealed gravel, sand and silt overlying chalky till, or boulder clay. The cutting on the western side (TQ 555 891) also revealed chalky till.

These remnants of till were deposited by a glacier, at the most southerly limit of the Anglian Ice Sheet, that filled the valley now occupied by the Ingrebourne river about 450,000 years ago. Other patches of till deposited by this glacier have been found nearby at the old Upminster Brickworks and at the railway cutting at Hornchurch. The road cuttings were examined by the Essex geologist Samuel Hazzledine Warren who recorded Palaeolithic flint implements, including at least one hand-axe, from the gravel which he considered to be deposited by an ancient river that was in existence in a warmer period after the retreat of the ice. These implements are now in the British Museum.

The Geological Survey Memoir for the Romford District, published in 1925, describes both sections in some detail and records that the western cutting was particularly interesting. Here the London Clay forms the base of the section and in places several steep-sided channels cut in to the clay could be seen which were lined with chalky till and infilled with disturbed gravel. The sketch of the section in the Geological Survey Memoir shows these channels to be curious contortions in the strata which may have been formed by cryoturbation. This process occurs during the intense cold of a glacial period when the ground is permanently frozen (permafrost) with only the top metre or so thawing during each brief summer and freezing again in the autumn. Occurring during a subsequent glacial period after the Anglian glaciation, the repeated freezing and thawing over thousands of years must have created the contortions with the London Clay squeezed up in places and pushed down in others.

Construction of the Southend Arterial Road in 1922. This cutting, close to the Hall Lane exit, revealed evidence that a glacier passed by here about 450,000 years ago. Photo: British Geological Survey (P202129)