Integrated microstratigraphic investigations of coastal archaeological soils and sediments in Norway: The Gokstad ship burial mound and its environs including the Viking harbour settlement of Heimdaljordet, Vestfold

摘要

Investigations of past coastal landscape development have included soil micromorphology, chemistry and microfossil recording of soils and sediments associated with marine inundation and terrestrial soil formation in marine sediments. This paper reports on similarly studied site formation processes at Norwegian coastal sites in Vestfold, Norway: the Viking Period Gokstad Ship Burial Mound and nearby contemporary harbour site of Heimdaljordet. At Gokstad, strategically-focused coring revealed mound composition and an example of its buried soil and geology. The latter investigation suggested that post glacial uplift led to a 'slowstand' period of intertidal reworking of till before ~ 700 BC emergence and development of terrestrial soils. At Heimdaljordet, typically laminated intertidal silty clay loam sediments were sealed by beach sands, into which, for example, a boat grave was dug. Post-depositional processes affecting the Gokstad Mound were compared to those in other mounds, including those recorded in experimental earthworks. Waterlogged conditions in the Gokstad mound led to iron-phosphate migration and preferential deposition of vivianite in turf layers where relict litter (L) layers remained visible, and where wood chips from constructional activities are also very well preserved (as is the long ship itself). These soil insights and other paleoenvironmental studies of the buried soil and numerous turf sequences showed that the contemporary AD 900 Viking landscape was totally terrestrial. It had become wet sedge grassland managed for grazing. The partial weathering of turves and anomalous presence within them of'fresh' roots apparently indicates the possibility that turves were stacked and stored ahead of mound building. The 10th C robber trench had developed muddy features, and rooting traces show that it was not backfilled, but was slowly infilled by humic soil silting from turf mound layers. This event did not affect the overall anaerobic burial conditions in the mound, which can be starkly compared to those at the Heimdaljordet boat grave. Here, because of acidic subaerial weathering, the wooden boat only survives as an acidic pellety humus formed of wood residues that are often ferruginised. Iron appears to be concentrated at iron nail locations. Unlike the Gokstad mound, no bone survives, but one sample found a typical 'body stain' of secondary iron and phosphate close by the iron encrusted sword in the grave (potentially the pelvic region of the inhumation). Here, mineralised faecal gut remains have an assumed hydroxyapatite composition, and embed phytoliths and pollen/spores, as found in human coprolites and cess deposits studied elsewhere.