Hippos at Herne Bay
Client: Quinn Estates Limited
During strip, map and sample excavation at the former Herne Bay Golf Course in 2017, one area produced finds much older than the material that we regularly deal with. Topsoil stripping in an area known to the developers as ‘Swale 10′ revealed patches of silty clay and gravel containing fragments of fossil bones and teeth of very large animals dating to the Pleistocene period.
One of the earlier finds, a scapula (shoulder blade) fragment, was provisionally identified from a photograph as possibly being from a rhinoceros Friends Newsletter 102). However, this and some other fragments have subsequently been firmly identified as hippopotamus by Professor Danielle Schreve from Royal Holloway, University of London. At least two hippos are represented, including a young individual, and fragments of elephant ivory and part of a rhinoceros tooth have also been identified.
Hippos remains are relatively rare in Pleistocene deposits although the species has previously been recorded from the coast at Herne Bay. They are characteristic of temperate interglacial conditions, occurring in Britain some 125,000 years ago during the last interglacial period (Marine Oxygen Isotope sub-stage 5e), a period of globally warmer temperatures. Summer temperatures in Britain would have been higher than at the present day and, crucially since hippos do not tolerate frozen water, the winters were mild. The species represented is the same one that is nowadays restricted to sub-Saharan Africa, but they formerly had a much wider range. In Britain fossil remains have been recorded as far north as Stockton-on-Tees. The possibility also exists that the fossils from the golf course may have come from a much earlier interglacial since a well-preserved hippo calcaneum (heel bone) from Swale 10 is larger than modern hippo reference specimens: a larger extinct species (Hippopotamus major) has been recorded from deposits dating to around 500,000 years ago in East Anglia. Unfortunately, the fossils are too old for radiocarbon dating.
Danielle Schreve and Ian Candy (a Quaternary sedimentologist and stratigrapher, also from Royal Holloway) later visited the site to investigate the gravel deposits in Swale 10. One of their main aims was to see whether the fossils were in a stratified sequence of deposits, and if so whether other types of datable remains were present. A machine was used to excavate several deep sections down to the bedrock London Clay. This revealed that the patches of gravel had accumulated in a series of high-energy water channels that had crossed the site in this area during the cold period following the last interglacial. The fossils would have been washed out from deposits from further upslope, raising the possibility that some undisturbed stratified Pleistocene deposits may still remain in the area. Many of the fossil fragments show old breaks which ties in with the interpretation of transport from the original place of deposition.
The specialists also had time to look around the current area of excavation and Ian Candy explained to the excavation team how the natural deposits had formed on the site, including some puzzling geological features with a patterned appearance on the highest part of the site that would have formed as a result of high-energy water erosion.
The fossils and geological features provide a fascinating insight into the very different environments that existed in the Herne Bay area during the Quaternary period. Perhaps appropriately given the amphibious habits of hippos, Swale 10 is destined to become a lake, part of the plans to help with drainage on the new development.