Fig 1.
Map of Scandinavia zoomed in on the area of the Ageröd I site located on the ancient shore of the former shallow lake.
World map generated with QGIS 3.10 using the Natural Earth data set. Lower right drawing of the Ageröd area by Arne Sjöström. Image freely available through CC by 4.0 licence by PLOS ONE and previously published in [1].
Fig 2.
The 1x1 meter trenches from 2019 in relation to the former excavation trenches, the ditch draining the bog and the soil bank of excavated ditch material from its establishment and maintenance.
The zone divisions were set to enable the study of differences in bone preservation between the driest (zone 1) and the wettest (zone 4) conditions. Image freely available through CC by 4.0 licence by PLOS ONE and previously published in [1].
Fig 3.
Sections from the four undisturbed trenches excavated in 2019.
Blue arrow shows added soil from the drainage ditch, red arrow shows the upper peat layer, white arrow shows the white (archaeological) cultural layer and green arrow shows the lower peat layer. The different layers are most evident in trench 201, in trench 205 the lower peat layer is almost completely gone and difficult to detect as it has deteriorated and become merged with the white cultural layer. Trench 217 has the largest amounts of added soil from the drainage ditch on top of the originally deposited layers, and the ditch has been dug down into the moraine here as shown with the orange morainic soil in the added soil layer. The white numbered squares indicate the depth of the different soil samples (see Table 3 for depth information). The used terminology of the stratigraphic units/layers follow the original from the 1940´s. Image modified from original created for [1] and is freely available from PLOS ONE through CC by 4.0 licence.
Table 1.
Geoarchaeological methods and their abbreviations.
Fig 4.
Schematic drawing showing various microanatomical features of bone.
These include osteons (the bold circles), lamellae (the fine circles/lines), osteocyte lacunae (OCL) and Haversian canals (HC), as well as diagenetic features such as bioerosion, microcracking and inclusive material. Figure by Hege Hollund for this publication.
Table 2.
Histological indexes used to assess bone preservation.
Table 3.
Result of the wet chemical analyses applied to the different soil samples.
Table 4.
XRF-data from the soil analyses of Ageröd I 2019 excavations.
Fig 5.
Variations in soil chemistry as a function of pH and depth.
The size of the dots reflect the relative amount of each component in the analysed sample and the colour of the dot refers to a trench. a) Organic matter (LOI, range: 3.9–50.8%), b) Calcium (Ca, range: 0.7–6.1%), c) Magnetic susceptibility quota (MSQ, range: 16.5–657.2), d) Manganese (Mn, range: 198–1916 ppm), e) Sulphur (S, range: 0.07–1.74%), f) Iron (Fe, range: 1.7–6.9%).
Fig 6.
Model based on the analysed parameters (phosphates, Magnetic susceptibility, Loss on ignition and pH) and XRF-data set. Green encircled variables indicate buffer (pH and Ca) and orange encircled variables indicate reducing conditions (LOI and Mn).
Fig 7.
Model based on the analysed parameters (phosphates, Magnetic susceptibility, Loss on ignition and pH) and XRF-data set. Green encircled variables indicate buffer (pH and Ca) and orange encircled variables indicate reducing conditions (LOI and Mn).
Table 5.
General information concerning the histologically analysed bone samples.
Fig 8.
Micrograph of sample A1 (A) and ID70 (B), excavated in 1940 and 2019 respectively, in polarized light. Sample A1 display bright birefringence across the whole sample except a narrow band along the outer surface, whereas sample ID7 hardly displays any birefringence at all and the image appears dark. Photo by Hege Hollund for this publication.
Fig 9.
Micrograph of sample ID62, excavated in 2019, displaying yellow, brown and orange staining across the whole thickness of the bone.
There are large cracks across the middle cortex, likely exacerbated by the sample preparation. Photo by Hege Hollund for this publication.
Fig 10.
Micrographs of bone samples displaying grains of pyrite and oxidized pyrite within bone samples.
(A-B) Two samples (A1 and A3) from the 1940s contain numerous intact pyrite grains within bone pores, appearing as black/opaque spheres (Samples A1 and A3). C-D) A sample excavated in 2019 (ID114) contain oxidized pyrite grains, retaining the shape but appearing reddish-brown and translucent in normal transmitted light. E-F) Sample ID9 excavated in 2019, in transmitted (E) and reflected light (F), the latter showing that the blurry mass seen in transmitted light contains pyrite grains. Photo by Hege Hollund for this publication.
Fig 11.
Micrographs of bone samples with possible recent microbial growth with apparent fungal structures and biofilm within pores, on the surface and ‘floating’ in the resin the sample is embedded in.
A-B) Sample ID9 and ID81 with spherical, grey and transparent spheres within cracks and pores (red arrows). These could be fungal fruiting bodies. C) The same spherical shapes floating in the resin above the surface of sample ID81, where two shapes (red arrows) look like budding (dividing) fungal cells. D) Sample ID9 seen in UV-light, with a similar shape of a budding cell (red arrow) in the resin directly above the bone surface (red asterisk), with a light blue fluorescens. E) dark, elongated shapes near the endosteal surface of ID114, possibly biofilm pushed off the surface during sample preparation. F) The same elongated shapes (asterisk) observed in UV-light on the periosteal surface (red asterisk) of sample ID114. Photo by Hege Hollund for this publication.
Fig 12.
OHI and GHI values for the histologically analysed bones from Ageröd.
Divided into excavation campaigns and zones.
Table 6.
Results of the collagen preservation analyses.
Fig 13.
Collation of all radiocarbon dates done on charcoal, hazelnut shells and bones from Ageröd I:HC.
Data from Larsson (1978), Magnell (2006) and previously unpublished data LuS-7903. BL = Bottom layer, LP = Lower peat, UP = Upper peat, CL = white cultural layer. LuS-14888 and LuS-14891 are the wild boar radius respectively roe deer femur from the 2019 excavation campaign.
Fig 14.
Comparison of collagen preservation between the different excavation campaigns.
a) Boxplot of the amount of preserved collagen, illustrated as the median of the collagen yield percentage from each excavation campaign with the upper and lower quartiles added, with whiskers added to include the outliers. Average value added as an X with a trend line connecting the different excavation campaigns. b) Illustration of collagen preservation showing that all bone samples from the 1940s and the 1970s had preserved collagen while only half of the bone samples from 2019 had preserved collagen. c) the data inserted into a chronological frame showing a hypothetical trend line when, if no preservative actions are taken and the organic deterioration continues at the same rate and is not further accelerated, collagen might no longer be preserved at Ageröd.
Table 7.
Archaeobotanical analysis of seven soil samples from Ageröd.
Fig 15.
A selection of archaeobotanical plant remains recovered from zone 3.
a) Aspen catkin bract; b) Pond Weed seed; c) White Water-lily seed; d) Crab Apple seed; e) Raspberry seed. Photo by Santeri Vanhanen for this publication.
Fig 16.
Earthworm cocoon from the bottom of trench 209, sample 188.
Photo by Santeri Vanhanen for this publication.
Fig 17.
a) Water pepper seeds and b) hazelnut shell found in trench 209 with superficial corrosion damage. Photo: Santeri Vanhanen. Image originally created for [1] and freely available from PLOS ONE through CC by 4.0 licence.
Fig 18.
Red deer tibia from trench 205 showing surface etching.
The picture was taken minutes after it was recovered and has here been gently washed to clean it in preparation for the picture. Photo by Mathilda Kjällquist for this publication.