NHER 68394 (Monument record) - Late Saxon to early medieval salterns

May 2018. Topographic Survey, Trial Trenching and Borehole Survey.
Evaluation of proposed development site (Lynnsport 1).
The 11 trenches excavated revealed extensive evidence for medieval or earlier salt production, with three probable saltern mounds identified. The deposits forming these mounds represent the accumulated waste from an industry where salt was obtained by boiling down a brine solution created by washing and filtering salt-impregnated silts and sands collected from the nearby intertidal zone. The easternmost of these mounds (Saltern 12) had been identified as an earthwork on aerial photographs (one of several features recorded as NHER 13785) but the other two were new discoveries (Salterns 10 and 11). There was though no trace of a possible saltern mound visible as an earthwork on aerial photographs at the northern edge of the site (NHER 27895) – the two trenches placed to investigate this feature encountering only recent made-ground deposits. The only possible surviving trace of salt production at this location was a very thin burnt red soil horizon overlying the natural salt marsh deposits.
All three of the saltern mounds identified were comprised of light yellowish brown sandy silt deposits likely to represent discarded filtration waste. Hand augering suggested that the three mounds survived to similar heights, with salt-making deposits shown to be between 0.88m and 1.02m in thickness. In all three mounds these layers were interspersed with thinner bands of darker material likely to represent waste from the hearths used to boil down the brine solution generated by the filtration process. Finds from these various deposits included fragments of fuel ash slag, pieces of fired clay (including possible fragments of hearth lining) and animal bone (including possible debitage from bone working). A single sherd of medieval pottery recovered from a dump of probable hearth waste in the easternmost mound (Saltern 12) was though the only datable artefact recovered.
In situ remains associated with salt production included several clay-lined tanks found within the westernmost mound (Saltern 10), which were likely to represent surviving elements of filtration units. A pit was also identified within the central mound (Saltern 11), although this appeared to have no lining. The fills of these features also produced no datable finds.
Samples taken from the features and deposits associated with salt production charcoal but little else of note in the way of plant remains. Foraminifera and ostracods were though present.
Two sherds of late post-medieval pottery were recovered from an extent drainage ditch adjacent to the westernmost saltern mount, which was shown to truncate a more substantial ditch of uncertain date.
Trenches excavated in the northern central part of the site revealed evidence for significant recent truncation, with natural deposits overlain by up to 1m of modern material containing fragments of concrete, plastic textile and metal. A further area of recent truncation was also identified towards the eastern end of the site, between the central and easternmost saltern mounds. Two test pits demonstrated that earthworks at the northern limits of the site were comprised of recent made ground.
See report (S1) for further details.
P. Watkins (HES), 1 August 2024.

January-February 2019. Excavation.
This final phase of archaeological mitigation saw further investigation of the three saltern mounds identified by the preceding trial trenching.
Two of the four excavation areas were positioned to target the westernmost saltern (Areas F and G; Saltern 10). The earliest filtration waste silts exposed in the northernmost of the excavation areas were cut by seven clay-lined features – all likely to represent the remains of the filtration units in which concentrated brine solution had been produced by washing and filtering salt-rich silt deposits. Three substantially complete filtration units were recorded, each of which comprised a sub-square or sub-rectangular tank and an adjacent deeper sub-circular pit element. Two of the tanks retained evidence of the turves which have been used to filter out silt particles from the brine solution (which then drained through narrow clay-lined channels into the deeper circular pits). Several additional clay-lined circular pits were likely to represent either truncated or partially exposed filtration units. These various clay-lined structures were partly overlain by burnt deposits that represented waste from the hearths used to boil down the concentrated brine generated by the filtration units. Much of the fired clay from these deposits is thought to have related to these hearth structures but no in situ examples were identified. Filtration waste deposits forming the uppermost portion of the mound demonstrated the continuation of salt production, although no filtration units associated with this later phase of activity were identified. A piece of metal-working debris and a fragment of cattle bone were recovered from one of these deposits.
The central saltern (Area H; Saltern 11) was shown to have had been severely truncated during the construction of the adjacent hockey pitch. Here the natural salt marsh deposits were overall by a possible buried soil, from which two sherds of Middle Saxon pottery were recovered. This possible former land surface was overlain by a sequence of deposits likely to represent waste from a nearby heath. A sample of charcoal from one of these dark, ashy layers produced a Late Saxon to early medieval radiocarbon date of 1018-1155 cal AD at 95.4% probability (SUERC-87794; 965 ± 26 BP). Finds were limited to small fragments of iron smithing slag. These heath waste deposits were cut by a single clay-lined sub-circular pit, which was in turn overlain by a thick layer of filtration waste.
A probable buried soil was also noted beneath the easternmost saltern mound (Area I; Saltern 11). This deposit was cut by a single clay-lined filtration tank which was overlain by a deep sequence of both heath waste and filtration waste deposits, one of which contained a small assemblage of salt slag. The uppermost filtration waste layer was cut by four clay-lined features which produced small quantities of Late Saxon and early medieval pottery – suggesting an 11th-century date for this final phase of activity. This is supported by the radiocarbon dating undertaken, with charcoal from one of these features producing a Late Saxon date of 902-1029 cal AD at 95.4% probability (SUERC-97795; 1045 ± 26 BP) and charcoal from another a Late Saxon to early medieval date of 994-1152 cal AD at 95.4% probability (SUERC-97796; 984 ± 26 BP).
It is notable that one of the salt slag fragments contained a lump of preserved peat – demonstrating that locally cut peat had been used as fuel. The presence of heather and stems/rhizomes alongst the charred plant macrofossils suggests this material was also used as fuel, along with oak and the other woods identifiable within the charcoal assemblage. The ostracods and forams present within the samples examined are consistent with the collection of silts from the Lower Saltmarsh/Upper Tidal Mudflats zone of the nearby tidal creeks. They also suggest the presence of freshwater bodies such as ponds in the vicinity of the salterns.
The presence of iron slag at the site is of interest and suggests there may have been sporadic re-use of salt hearths as smithing hearths – presumably for the mending or re-forging of iron tools etc.
A single residual flint flake of Late Mesolithic/Early Neolithic date was the only evidence for activity at this location prior to the Middle Saxon period.
Information from report uploaded to OASIS. HER copy awaited.
P. Watkins (HES), 1 August 2024.