Geology

Artifacts and faunal remains are preserved at Boxgrove within an extensive set  geological deposits preserved across 26km of the West Sussex Coastal Plain.

These deposits were lain down at the end of a temperate interglacial period almost half a million years ago. They reflect a range of depositional environments from open marine foreshore, through regressional lagoonal deposits, terrestrial land surfaces and cold stage periglacial deposits. In the photograph on the right, the remains of the chalk cliff eroded by marine action at the start of the sequence can be seen. Up against this cliff a beach of rounded flint pebbles was deposited. The sediments overlying this beach were formed by the collapse of the cliff and mass movement of chalky sediments off the Downs to the north of the site. These calcium carbonate rich gravels sealed the sequence and chemically aided the preservation of bone at the site.

The photograph to the below shows the complete geological sequence from a section

excavated 50m to the south of the cliff line. This location, GTP13, is the Boxgrove Type Section (Holostratotype section of the Slindon Formation). At the base of the section the excavator can be seen working on the surface of the wave-cut chalk platform. Overlying this platform are alternate layers of marine sand and beach/cliff collapse layers. The marine deposits grade into finely laminated silts. These were deposited under low energy conditions in a lagoon/tidal flat environment. Small temporary landsurfaces developed within the intertidal sediments and these have preserved in-situ artifact scatters associated with butchered bone. This sand and silt sequence (The Slindon Formation) terminates with the development of a fen-carr environment preserved as a distinctive thin brown/red line of mineralised organics. Above this horizon beds of silty brickearth and soliflucted gravels (The Eartham Formation) from the end of the temperate stage and subsequent cold stage can be seen through to the top of the section. The gravels were deposited by mass movement and solifluction flows when permafrost thawed on the hills (The South Downs) to the north of the site.

At the hominid locality Q1/B an atypical geological seqeunce was encountered associated with dense concentrations of artifacts and hominid remains. The sequence, seen to the right, is conventional in that it begins with the deposition of marine sand and terminates with the development of a mineralised organic layer overlain by brickearth and solifluction gravel. However, immediately overlying the marine sands, above an abrupt erosive junction, are a suite of freshwater deposits indicating the infilling of a spring-fed stream bed and small lake. The sequence appears to be contemporary with the formation of the soil horizon elsewhere in the Boxgrove palaeolandscape. The presence of a localised source of freshwater would have provided an attractive resource for grazing animals and consequently a large concentration of game for the hominids to exploit. The density of archaeology found at this locality mirrors findings from other Early and Middle Pleistocene sites in suggesting that Archaic Homo sapiens were attracted to sandy freshwater channel environments.

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