Important geological sequence record TQ 67 SW 1837 - Swanscombe Lower Middle Gravel, dates to the Hoxnian interglacial (c. 400,000-380,000 years ago), Southfleet Road, Swanscombe

Trench 3, excavated in advance of the installation of a sewage settling tank within the Eastern Quarry construction compound, provided important evidence for the extent and character of the Lower Palaeolithic landscape at Swanscombe. Beneath a thin layer of modern topsoil, archaeologists uncovered approximately 0.75 m of artefact-bearing gravel. Analysis of the gravel composition demonstrated that it was deposited by the main Thames rather than by the smaller Ebbsfleet tributary. The deposit contained abundant well-rounded flint pebbles together with other rock types characteristic of Thames gravels transported from further upstream.

The gravel was correlated with deposits previously identified in nearby test pits and was considered probably, and perhaps almost certainly, equivalent to the Swanscombe Lower Middle Gravel, a well-known geological unit within the internationally important Swanscombe sequence. This deposit is thought to have been laid down during the Hoxnian Interglacial (Marine Isotope Stage 11), approximately 400,000-380,000 years ago, when southern Britain experienced a warm climate and remained connected to continental Europe. At this time the Thames flowed through a broad valley containing multiple channels, gravel bars and floodplain environments. The local landscape around Swanscombe is interpreted as a mosaic of woodland and open grassland, supporting large mammals and providing favourable conditions for human occupation.

The gravel yielded twenty-four worked flint artefacts recovered through sieving. These consisted entirely of flakes and knapping waste rather than complete tools. Two flakes display characteristics consistent with handaxe manufacture, while the wider assemblage probably reflects repeated handaxe production either at the trench location itself or on slightly higher ground immediately to the south-west. The artefacts were moderately to heavily abraded, suggesting movement and reworking within a fluvial environment before final burial within the gravel deposit.

The significance of these discoveries becomes clearer when viewed alongside earlier investigations in the surrounding area. Comparable artefact-bearing gravels had previously been identified in nearby test pits including TP 4.1, TP 6.2, TP 7.1, TP 7.2, TP 3.1 and TP 3.2. Several of these produced handaxes together with substantial quantities of manufacturing waste, while TP 7.2 also yielded a metatarsal bone from a large herbivore, possibly rhinoceros or bovid. Immediately south-west of Trench 3, excavations in Zone V revealed dense concentrations of fresh, unabraded artefacts preserved within clayey and silty deposits. These deposits contained mint-condition artefacts and may represent areas where Palaeolithic material survived with relatively limited post-depositional disturbance.

The report suggests that the area around Trench 3 occupied a particularly favourable position close to the confluence of the Thames and Ebbsfleet rivers. Such a location may have been attractive to hominin groups because it could have provided access to water, a ready supply of flint from river gravels, good visibility across the surrounding landscape and opportunities to encounter large mammals moving through the valley system. As a result, the area may have attracted repeated visits by Lower Palaeolithic hominins.

Perhaps the most important contribution of Trench 3 is that it provides important evidence for the southernmost known extent of deposits interpreted as the Swanscombe Lower Middle Gravel. This helps link the classic Swanscombe deposits at Barnfield Pit with archaeological discoveries further south, including the famous Southfleet Road "Elephant Site" approximately 400 m away. The trench therefore represents an important component in reconstructing the wider Thames-Ebbsfleet landscape occupied by humans during the Hoxnian interglacial around 400,000 years ago. (1)