Södertörn
—Interdisciplinary Investigations
of Stone Age Sites in Eastern Middle Sweden
Chapter 5 Stone Age Sites
—Iron Age Dates
Per Gustafsson
The Swedish National Heritage Board
Archaeological Excavations Dept.
Central Unit
Instrumentvägen 19
SE-126 53 HÄGERSTEN
Phone +46 10 480 80 60
Fax +46 10 480 80 94
www.arkeologiuv.se
e-mail [email protected]
© 2008 The Swedish National Heritage Board
Archaeological Excavations Dept., Central Unit
ISBN 978-91-7209-515-1
© Lantmäteriverket, SE-801 82 GÄVLE. Dnr L1999/3.
Godkänd från sekretessynpunkt för spridning.
Lantmäteriverket 2008-08-25 (dnr 601-2008/2167).
Contents
Introduction............................................................................................................ 5
AIMS AND METHODS................................................................................................... 6
14
C Analyse Procedure Applied and Calibration of Dates......................................... 6
REGIONAL 14C CHRONOLOGY.................................................................................... 7
14
C Dates from Stone Age Sites Previous to the Grödinge Excavations . ................ 7
14
C Dates from the Current Excavations................................................................... 9
Previous and Current 14C Dates in Comparison..................................................... 10
EVALUATION OF EXPECTED/UNEXPECTED DATES............................................... 12
Stone Age or Iron Age............................................................................................. 12
Qualities of the Sites Sampled . ............................................................................. 12
Sample Units........................................................................................................... 13
Sample Material...................................................................................................... 13
COMPARISON BETWEEN 14C DATES AND THERMOLUMINESCENCE DATES..... 14
Conclusions........................................................................................................... 14
FINAL REMARKS......................................................................................................... 15
TABles........................................................................................................................ 16
figures...................................................................................................................... 17
Södertörn—Interdisciplinary Investigations of Stone Age Sites in Eastern Middle Sweden 3
Chapter 5
Stone Age Sites—Iron Age Dates
Per Gustafsson
Introduction
All the Stone Age sites studied within the Grödinge project except the
Nolinge Quartz quarry were 14C dated. Dating was carried out on a total
of 89 samples of which 42 yielded Stone Age dates. Prior to the Grödinge
excavations c. 70 dates from Stone Age sites in Eastern Middle Sweden
had been published. As a result of the excavations aligning the Grödinge
railway the amount of 14C dates from Stone Age contexts was almost
doubled. This fact demands a re-evaluation of the regional 14C chronology. Due to the high frequencies of dates falling outside the Stone Age an
attempt to explain archaeological miscalculations concerning selection of
samples is made. Probable explanations for dates being unexpected are
put forward and the result of comparison between 14C dates and TL dates
are discussed.
The sampling was guided by site specific conditions. In general, a
higher number of datings were carried out from contextually complex
sites compared to less complex sites.
The general purposes for carrying out 14C dating were to:
• contribute to the establishment of a regional Stone Age chronology independent of the South Scandinavian chronology (cf. chap. 2 & 3).
• settle a chronological framework attached to the utilisation of each
site. The site specific questions addressed by radiocarbon sampling are
discussed below (cf. chap. 16–19).
• try to chronologically separate spatial structures within the sites (cf.
chap. 16–19).
Some characteristics regarding the sites gave specific possibilities to create relations to 14C dates.
An example where complex spatial structures were interrelated to 14C
dates is the Smällan 1 subarea.
Contexts with vertically stratified layers, like Smällan 1, gave possibilities to correlate 14C dates to a structure presumably obtaining a relative chronology.
The occurrence of various kinds of features at the sites studied made
it possible to relate 14C dates to specific kinds of features. This resulted in
a limited test of the chronological span of certain feature types. With two
exceptions (the Neolitihic remains; at the Kyrktorp 9B subarea and at the
Eklundshov site) the Stone Age sites were regarded to have been shore
bound. This gave us means to relate 14C dated presumed sealed contexts
like features to certain altitudes, which resulted in interpretations of the
interrelationship between site locations and regional shore displacement
(cf. chap. 10 and chap. 3). The investigations of the Eklundshov, Smällan
and Kyrktorp sites exemplify this aspect of 14C dates in contextual analyses (cf. chaps. 16, 17 and 18).
Södertörn—Interdisciplinary Investigations of Stone Age Sites in Eastern Middle Sweden 5
Chapter 5
AIMS AND METHODS
This section aims at studying the 14C dates from the Grödinge excavations
from two different starting points. Firstly the regional chronology: here
the intention is to add the Grödinge dates to a compilation of regional
dates, to study in which ways the new information is complementary to
the old and to discuss problematic discrepancies regarding 14C dates of
contexts believed to be contemporary. Secondly this chapter aims at presenting possible explanations for some of the dates being much younger
or older than expected. A radiocarbon date has been considered unexpected when it does not correspond to the archaeologically dated context
it was sampled from.
The following questions represent some dimensions of the problem.
• Are the presuppositions concerning dates of the sampled contexts incorrect, which mean an archaeological evaluation failure?
• Does the individual sample have a quality that makes it easily mixed
in an irrelevant chronological context?
• Are the risks for contamination of samples high due to the quality of
sample units or sample material?
Dates from different chronological periods provided great variations
concerning qualities for what can be considered to be expected and unexpected dates, respectively. From the Mesolithic sites dates can differ by
1000–1500 14C years without being considered unexpected by archaeological means. The altitude above sea level of the site was important
for judging the part of the Mesolithic to which the remains should be
preliminary dated. In one case, at the site Smällan 1, the stratigraphical
distribution of the dates formed a chronological structure with the earliest dates at the bottom and the latest dates at the top of the stratigraphic
sequence. At this site a variation of 500 14C years was sufficient for a date
to be considered unexpected. For sites with Neolithic artefacts, dates with
variations of 200–400 years were considered as unexpected results. Here
the relation of the dates to the chronology based on type variation of the
pottery was crucial for determining which dates were expected and unexpected respectively.
Thermoluminescence (TL) dating was carried out to evaluate the results obtained through 14C dating through an independent dating method.
To fulfil the first aim in this section the dates previously published and the
current dates are presented in text and compared through a presentation in
tables (Tables 5.1–5.3). To shed light on the second aim the percentages
of expected/unexpected referred to archaeological evaluations of sampled
contexts i.e. sampling-units, sample-material etc. are calculated and discussed.
14
C Analyse Procedure Applied
and Calibration of Dates
The 14C analyses of samples from the Grödinge excavations were run at
the Tandem Accelerator Laboratory in Uppsala (Ua), the Laboratory for
6 Södertörn—Interdisciplinary Investigations of Stone Age Sites in Eastern Middle Sweden
Chapter 5
Isotope Geology at the National Natural Historical Museum in Stockholm
(St), and the Department of Physics at Uppsala University (U) (Table 5:1).
With one exception all samples consisted of carbonised organic material. At the laboratories visible rootlets were removed, and the sample
material was then treated with HCl, distilled water, NaOH, distilled water
and an acidifier (Possnert in Segerberg et al. 1991:88). The risk of mixing with later uncarbonised organic material was deemed small. There is
a risk of mixing non-contemporaneous carbonised material, particularly
in bulk samples, which were conventionally dated. All samples were normalised –25 % for 13C. The dates from the Department of Physics at Uppsala University were also corrected for variation from –25 % 13C. All 14C
ages are calculated with a half-life of 5568 years.
None of the individual samples was dated by more than one laboratory. Certain sites have 14C dating results from two or three laboratories.
No trend towards systematic differences between dates from the different laboratories was observed. Age intervals are presented with 1 sigma
standard deviations.
Calibration of all dates from the Grödinge excavations was carried out
according the University of Washington Quaternary Isotope Lab, Radiocarbon Calibration Program 1987, v. 1.3. It can be seen from the results
that the over all pattern concerning the interrelations of the dates that existed before calibration remains (Fig. 5:1).
The difference between 14C years BP and calendar age fluctuates in certain time periods, depending in part on cosmic ray and magnetic field variation. This fact is limiting the possibilities of reaching a detailed chronology. Such time periods occur at 8000 BP (Kromer et al. 1986) and 4500 BP
(Pearson et al. 1986). Generally the difference between calendar years and
14
C years expands with the age of the dated sample. Mesolithic calendar
ages are c. 900 years earlier than the 14C ages and the Late Neolithic calendar ages are c. 500 years earlier than the 14C ages. Dates that fall around
2000 BP show no considerable time difference after calibration.
REGIONAL 14C CHRONOLOGY
14
C Dates from Stone Age Sites
Previous to the Grödinge Excavations
The 14C dates from Stone Age sites in Eastern Middle Sweden published
prior to the excavations along the Grödinge railroad were primarily intended to date selected periods of the Mesolithic or Neolithic. The relative chronology based on artefact typology has been crucial for whichever
periods were chosen for 14C dating. The altitudes of the excavated sites,
measured in m a.s.l., have also played an important role in placing the
sites in a relative chronology. The 14C dating method was used to try and
reach absolute dates of sites at different altitudes above sea level. All older dates have been published as uncalibrated dates (Fig. 5:2). An account
of and commentary on the previous dates is given below. The account is
in chronological order and begins with the earliest sites.
Welinder (1977a) presented features or layers dated from several sites
with artefacts from the Mesolithic. He attempted to clarify whether the
Södertörn—Interdisciplinary Investigations of Stone Age Sites in Eastern Middle Sweden 7
Chapter 5
sites were situated at the coast by correlating dates with the altitude of the
sampling units in m a.s.l. (1977a:1). In addition, dates were sought for
those sites that Welinder assigned to the category he called quartz or flint
groups. Many samples dated to periods later than the Mesolithic. Several
of the sites lacked Mesolithic dates entirely (1977a:38). In the discussion of the dating results from the presumed Mesolithic occupation site at
Sjövreten on Södertörn, the difficulty of dating settlement site layers was
stressed. A series of samples from a vertical stratigraphy were expected
to derive contemporary dates. The upper layer, however, gave the earliest
date and the underlying layers yielded increasingly later dates with increasing depth. The explanation appeared to be the mechanical mixing of
later charcoal pieces in the layer after the Mesolithic occupation phase.
The sites Masmo 1 and Häggsta 1, located on Södertörn, gave 14C dates
within the intervals 5700–5500 BP (Masmo 1) and 5500–5000 BP
(Häggsta 1). This means that the 14C dates from Masmo 1 and Häggsta 1
are the first Late Mesolithic dates from sites in Eastern Middle Sweden
(Olsson & Åkerlund 1987:19).
The attempts to 14C date sites with artefacts typologically dated to the
Early Neolithic have only occasionally resulted in the expected dates. In
general, the samples have dated to time periods later than that expected.
In the presentation of the dates from Hjulberga in Närke, a difference
was observed in the dating results from charcoal samples from different
sample material. The expected dates are c. 5000 BP. Charcoal samples
of pine, juniper and birch yielded dates from the interval 3000–500 BP,
while a date from hazelnut shell yielded the expected age (Hulthén &
Welinder 1981:25). During the excavation of a site at Charlottenborg
in Väversunda parish, Östergötland, Early Neolithic TRB pottery was
found. Three charcoal-samples from the site were 14C dated. All samples
dated to Early Iron Age (Browall 1991:130). The first series with several
dates which clearly can be linked to a find context with Early Neolithic
artefacts and that yielded the expected dates was from Häggsta 2 on
Södertörn. The dates lie within the time interval 5000–4800 BP (cf. chap.
3). A preliminary account of the dating results from Häggsta 2 has been
published (Olsson & Åkerlund 1987:21).
Welinder has compiled previously run 14C dates from Middle Neolithic
sites with Pitted Ware pottery (Welinder 1973b). His objective was to tie
14
C dates to the so-called Säter phases, which were based on typological
variation in the pottery. The Säter phases were later connected to dates
of the South Scandinavian TRB culture and Battle-Axe culture. The result was a chronological scheme according to Welinder (1973b). Lars
Löfstrand also discussed 14C dates from Pitted Ware sites in Sweden. He
touched upon the grouping of the dates that was thought to exist, and
emphasized that they need not mirror the dominating cultural phases
but could arise from varying 14C amounts in the atmosphere (Löfstrand
1974:110). Löfstrand predicted a correction of the values, by calibration.
Later, Welinder dated samples from the sites Brunn and Korsnäs on
Södertörn. The dates were compiled with 14C dates from Överåda in Södermanland and Äs in Västmanland to test a chronological model that
posited a chronological difference between the sites (Welinder 1978:103).
In all, 21 14C dates of wood or charcoal exist from the Alvastra pile dwelling in Östergötland. Here the purpose was to date different parts of the
8 Södertörn—Interdisciplinary Investigations of Stone Age Sites in Eastern Middle Sweden
Chapter 5
pile dwelling precisely; e.g. the earliest log floors (Browall 1986:27). The
central values of the dates span over 510 years, 4600–4090 BP
One charcoal sample with somewhat later date was collected at Svällinge
in Strå Parish, Östergötland. The date, which was thought to be representative of a context that also contained porous, so-called Säter IV pottery,
was 4065±160 BP (Browall 1986:144).
Samples from Masmo 2, a site characterized by Pitted Ware pottery,
have been 14C dated to the Middle Neolithic, Bronze Age, and Early Iron
Age (Olsson & Åkerlund 1987:24). During the excavation of Early and
Middle Neolithic sites at the Bälinge bog in Uppland, series of samples
from hearths were dated. The majority of these yielded dates from the
Early Iron Age. The representativeness of the features for the Middle Neolithic site is therefore called into question (Segerberg 1978:32). In a later
work, Segerberg had four sherds from Säter and Fagervik in Östergötland
dated. A control was sought for the dates of the so-called Säter II and
Säter III styles by using carbonised material attached to sherds that dated
typologically to different parts of the Middle Neolithic. The result was
that Säter II sherds corresponded well with earlier views of the styles’
date, and Säter III sherds received somewhat older dates than expected
(Segerberg et al. 1991:89f).
Dates from the Late Neolithic have seldom been noted. One Late Neolithic date, however, comes from Stora Malmtorp on Södertörn in a find
context and at an altitude that indicates a date from the Mesolithic–Early
Neolithic (Olsson & Åkerlund 1987:25). Wigren (1987) presents several
Late Neolithic dates from Södermanland sites characterized by Bronze
Age remains and where most of the other 14C dates are from the Bronze
Age (Wigren 1987:86).
Dates from the Early Iron Age exist from a number of sites besides
those with Stone Age remains. During the 1980s the number of dates
from settlement sites and graves has increased (Widgren 1987:51), Fernholm 1987:62, Nilsson 1987:83). Dates from iron workshops are also
known (Hjärthner-Holdar 1987:114ff). Excavations of hill-forts have
yielded 14C dates from the Early Iron Age as well (Olausson 1995:153). In
figure 5:2, however, only those Iron Age dates associated with sites that
were noted because they contain remains from the Stone Age are given.
14
C Dates from the Current Excavations
The Eklundshov site yielded the so far earliest Mesolithic dates in the
region (cf. chap. 16). In all, eight dates fell within the interval 8200–7000
BP. The samples, which were expected to be Mesolithic showed a tendency to cluster in two chronologically separated groups.
A younger phase of the Mesolithic has been dated at the Kyrktorp 9B
site (cf. chap. 18). Five dates fell within the interval 6500–5500 BP, one
date was 600–1400 14C years older but the high standard deviation for the
date makes it difficult to interpret further. The division of samples at the
Kyrktorp 9B site, may be interpreted as evidence of the site originally being in limited use, and later used more intensively, and then again used less
intensively. The probability is great, however, that the samples are contemporaneous and that the results of the analysis show a normal distribution
resulting from the statistical variability that accompanies each 14C date.
Södertörn—Interdisciplinary Investigations of Stone Age Sites in Eastern Middle Sweden 9
Chapter 5
The Smällan 1 site represented the youngest part of the Mesolithic (cf.
chap. 17). Eight dates fell within the interval 5800–5000 BP. Three dates
were up to 500 14C years older. These dates do not match the horizontally
stratified layers of the site and there is no reasonable explanation for them
being too old. No evidence of contamination was detected and the sample
context did not seem to be disturbed.
Three dates from the Smällan 2 subarea represent an Early Neolithic
context and one probably a Middle Neolithic context. All these dates,
however, fell in the interval 5200–4900 BP.
There are six dates representing the Middle Neolithic from the Kyrktorp 8W site. All of these dates fell in the interval 4900–4200 BP (cf.
chap. 18).
The Kvedesta site also represents the Middle Neolithic as well as the
Late Neolithic. Two dates fell in the interval 4500–4100 BP and one date
within the interval 4000–3700 BP (cf. chap. 19).
There are occasional Late Neolithic/Early Bronze Age dates from the
Eklundshov site, Kvedesta site Smällan subarea 1 and Kyrktorp subarea
9B. None of these sites/subareas, except Kvedesta and possibly Eklundshov, has a corresponding archaeological find context (cf. chap. 3).
Contexts dated to Early Iron Age occur on all 14C dated sites. These
dates correspond to the investigated Iron Age finds and features at all the
excavated sites.
Previous and Current 14C Dates in Comparison
The timescale of Stone Age in Eastern Middle Sweden is presented in
figure 5:2. One view of the current dates is given with conventional 14C
years BP and one with calibrated dates. In comparing previous dates and
dates from the Grödinge excavations the uncalibrated dates have been
used, since calibration was not in use when the older results were published.
The dates from the occupation at the Eklundshov site, within the interval 8300–7700 BP are the earliest known from the region. This has to
be considered the most important contribution to the regional 14C chrono­
logy. The addition of dates to the younger part of the Mesolithic and to
the early Neolithic is also of great importance. Most of the dates from
previously excavated sites fell in the Middle Neolithic.
The Mesolithic samples have been roughly placed in periods of c.
1000 years. Through artefact and 14C dating conducted earlier, the Neolithic has been finely divided into periods of 200–350 years (Welinder
1973).
The regional 14C dates from presupposed Stone Age sites tend to clusters
within the following intervals (1 σ):
8300–7700 BP
5600–4800 BP
4600–4300 BP
3200–2900 BP
2500–1700 BP
10 Södertörn—Interdisciplinary Investigations of Stone Age Sites in Eastern Middle Sweden
Chapter 5
At some intervals there are gaps in the 14C chronology. These gaps are
characterised by complete lack of dates or the occurrence of only occa­
sional dates. One of these gaps falls within the interval 7000–6500 BP
another in the interval 5000–4700 BP.
The tendencies for chronological gaps seem to correspond to a lack
of sites within certain altitude intervals and/or lack of archaeological
finds which are typologically representative of certain periods (Welinder
1977:39, Olsson & Åkerlund 1987:19).
Hypothetically we could divide the Mesolithic dates to Middle (8000–
6500 BP), and Late (6500–5200 BP) Mesolithic. The Mesolithic phases
would then cover c. 1500 years. Due to the low number of dates at certain
intervals the relevance of this chronological framework has to be verified
through future research (cf. chap 3)
The Grödinge investigations resulted in four dates from an Early Neolithic context. The dates fell within the interval 5200–5000 BP. These
dates are earlier than and/or overlap with previous dates from Early Neolithic sites which fell within the interval 5100–4800 BP (cf. Hulthén &
Welinder 1981:25).
Neither the previously published nor the new results provide dates
from sampling contexts with the type of pottery thought to characterise
the transition between the Early and Middle Neolithic, so called Fagervik
1. This might explain why there are only occasional dates in the interval
5000–4700 BP.
In previous publications the problem of interpreting 14C dated Middle Neolithic sites was discussed. Variations in 14C in the atmosphere
appear to be the cause for difficulties in creating a 14C chronology that
corresponded to the chronology based on artefact typology (Löfstrand
1974). Another problem is the variations concerning the archaeological
choice of sampling material. At some of the previously dated sites the
sample material was unburnt bone, in part from terrestrial animals and in
part from marine animals. Dates on collagen from marine animals must
be corrected for the reservoir effect. For seals in this part of the country
it may be estimated at –200 to –400 years (Håkansson 1978). The results
from the 14C dating of samples in Middle Neolithic contexts from the
Grödinge excavations also exemplify the difficulties in establishing a correct 14C chronology for this part of the Stone Age. It is clear from figure
5:3 that the samples from Kyrktorp 8W were dated to the same interval
in 14C years BP as the earliest previously known typology of pottery and
14
C dated Middle Neolithic sites in Eastern Middle Sweden. Based on
initial examination, however, the pottery from Kyrktorp 8W appears to
be typologically later than the pottery occurring on those sites that previously provided similar 14C dates (cf. chap. 18). According to the ceramic
typology, the Middle Neolithic subarea at Kvedesta should be earlier than
the Kyrktorp 8W site (cf. chap. 3). The 14C dates from the Kvedesta site,
however, were younger than the dates from the Kyrktorp 8W.
The attempt to separate sampling units with expected Mesolithic or
Neolithic dates from units with expected Bronze/Iron Age dates during
sampling has succeeded in c. 75 % of the cases. Hearths gave a higher
frequency of expected dates compared with lenses and fire-cracked rock
concentrations. This situation can be clarified by the fact that we saw two
groups of hearths, one with small amounts and one with large amounts
Södertörn—Interdisciplinary Investigations of Stone Age Sites in Eastern Middle Sweden 11
Chapter 5
of soot and charcoal. The former group, in accordance with expectations,
has provided primarily Mesolithic dates. The latter has provided dates
from the Bronze and/or Iron Age. Lenses and fire-cracked rock concentrations could not be similarly distinguished.
To a great extent dates from the Bronze/Iron Age fall within the same
time-interval as those, previously published, dated remains that occur together with Stone Age remains.
EVALUATION OF EXPECTED/UNEXPECTED DATES
Stone Age or Iron Age
A comparison of unexpected dates, reveals that 39 % that were expected
Stone Age dates turned out to be Iron Age (Table 5:2). In these cases the
radiocarbon dates did not match the interpretation of the archaeological
context.
The frequency of unexpected dates was highest in those cases where
dating of archaeologically determined Stone Age context gave Iron Age
dates. The tendency is strengthened by the fact that the total number of
Iron Age dates is higher than the total number of Stone Age dates. The result indicates that it is significantly more difficult to separate a Stone Age
context from Iron Age inclusions than an Iron Age context from Stone
Age inclusions. At some of the sites inclusions of traces from activities
during the Iron Age, to begin with, are not at all known. The excavation
has made it possible for the responsible archaeologists to successively
separate sampling contexts that stem from Iron Age activities and those
that stem from activities during some part of the Stone Age.
Qualities of the Sites Sampled
The comparison of sites with respect to frequencies of expected/unexpected dates aims at detecting archaeological evaluation failures on site
level (Fig. 5:4). The percentages of unexpected dates are evenly distributed between the sites.
The site-specific goals for the excavated sites vary which makes comparisons between sites more problematic. The Kyrktorp 9A site has the
highest percentages of expected dates, which may be explained by the
high rate of expected Iron Age dates.
In order to be able to compare 14C dated phenomena from distinct
prehistoric sites, knowledge of the methodological, technical and chemical processes that affected the samples is needed. Knowledge of how the
sampling sites, sampling units and sampling material were chosen is of
greatest importance (Olsson I. U. 1983:163). There are also problems
in comparing dates from settlement dry land sites with e.g. dates from
wetlands. Sources of error from the sites, units, or sample material must
be eliminated. Samples from wetlands may have a reservoir age; depositional processes or varying degrees of humic acid, which cannot be eliminated if the sample material is uncarbonised, can affect them. Marine
species may have a reservoir age. Wood in charcoal samples has a certain
internal age. Before we compared dates from the sites currently studied
12 Södertörn—Interdisciplinary Investigations of Stone Age Sites in Eastern Middle Sweden
Chapter 5
we took these different sources of error into account. This was necessary
when we compared samples from the prehistoric occupation sites with
samples from nearby wetlands.
Sample Units
In all, 72 samples from features and 17 samples from layers were dated
(Fig. 5:5). The diagram shows that samples from features corresponded
to expectations better than samples from layers. This can be explained by
the fact that the risk of contamination is greater in layers. The risk of obtaining unexpected dates rose when samples were patterned on the basis
of stratigraphic association and an expected chronological sequence. This
may be explained by the stratigraphical basis for comparison creating
short expected time intervals for the dates to fall in.
Among the feature types, hearths showed a somewhat higher frequency of unexpected dates than pits, but a clearly lower frequency than
fire-cracked rock concentrations and lenses. This may be explained by
misevaluations of the age of the feature types. During the sampling it became evident that hearths with a high proportion of soot and charcoal in
the fill dated to the Bronze/Iron Age and hearths with a low proportion of
soot and charcoal dated to the Mesolithic. Still some hearths with sooty
fills have wrongly been considered as belonging to Stone Age contexts.
The higher frequency of unexpected dates for lenses compared with pits
may be explained by lenses more easily being contaminated due to an
open structure.
Sample Material
The sample material used was charcoal (of which 90 % had been identified to species) and identified worked wood, other carbonised remains
were hazelnut shells, identified fruits and seeds, conifer needles and organic material from sherds (Fig. 5:6).
Seeds gave a higher proportion of unexpected dates than other sample
material. The dates made on seeds tend to be the youngest dates from
supposed contemporary contexts. This tendency indicates that single
seeds and comparable sample material were more easily deposited in
non-contemporary contexts. Hazelnut shells had a somewhat lower frequency of unexpected dates than other dated fragments, which may be
due to the fact that during the sampling we assumed that hazelnut-shells
were representative of Stone Age periods. This assumption was correct in
all but one case (Feature A119, Kyrktorp 8W). Seeds, fruits and needles
gave the highest relative percentage of dates from a prehistoric period
other than the expected one, while pieces of charcoal including 50 annual
stems have a low percentage (Fig. 5:7).
The distribution of expected and unexpected dates varies between different wood species (Bartholin 1979). Only species that occur in more
than three samples are considered here (Fig. 5:8). Pine (Pinus sylvestris),
showed the lowest frequency of unexpected dates. Note that the samples
with birch (Betula sp) gave unexpected dates (i.e., Iron Age dates) in
Stone Age contexts and expected dates in Iron Age contexts. Hazel (Corylus avellana) had a higher frequency because three samples from SmälSödertörn—Interdisciplinary Investigations of Stone Age Sites in Eastern Middle Sweden 13
Chapter 5
lan 1 were classified as unexpected due to the special goals formulated
at that site. We believed spruce (Picea abies) ought to occur only in Iron
Age contexts, but this was actually borne out in only two cases. The species showed a much higher frequency of unexpected dates younger than
Iron Age.
COMPARISON BETWEEN 14C DATES
AND THERMOLUMINESCENCE DATES
Thermoluminescence (TL) dates were run on nine samples from the
Grödinge excavations. Vagn Mejdal at the Nordic Laboratory for Thermoluminescence Dating in Roskilde carried out the dating. The goals of
the TL dating were to test an independent dating method on sample material from the Middle Swedish Stone Age settlement sites and to compare
the results with dates obtained through 14C dating.
Three features have both 14C and TL dates. The expected TL dates
were supposed to agree with calibrated 14C dates (chap. 16, Table 16:13).
In one case this agreement occurred (Fig. 5:9). In one case the TL date
corresponded to the uncalibrated 14C date, and in one case there was no
correspondence.
Conclusions
Through the 14C dates from the Grödinge excavations it is possible to
contribute to a chronology for the Stone Age in Eastern Middle Sweden.
Most of the Stone Age dates fell within the Mesolithic, a fact that is considered important for the creation of a 14C chronology of this period in the
region. Some phases of the Mesolithic lacked 14C dates as presented in the
publications of the analyses previous to the Grödinge excavations. The
region’s earliest 14C-dated site (Eklundshov) has its earliest occupation
phase dated to 8200 BP, which can be compared to the earliest 14C-dated
occupation phase at the previously published site Sjövreten, which was
dated 6600 BP (Welinder 1977:39). Though the Grödinge excavations
add dates of previously not dated phases of the Mesolithic there are still
intervals with very few dates.
By dating a series of samples from the same site it has been possible to
create a basis for a phase division of certain Stone Age periods. The eight
Mesolithic dates from Eklundshov are thought to represent two phases.
Occupation remains probably represent an even greater number of phases,
but the number of dates is not sufficiently large to allow more than two
phases to be distinguished.
Through dating of samples from vertically stratified layers (Smällan
1) we obtained a chronological series of dates with the earliest date from
the lowermost layer and the latest date from the topmost layer in the
stratigraphy. Our aim to let the knowledge of the stratigraphical conditions guide our expectations on the chronological structure of the site and
choice of sample spots resulted, however, in an increase in the frequency
of unexpected dates.
14 Södertörn—Interdisciplinary Investigations of Stone Age Sites in Eastern Middle Sweden
Chapter 5
The Early Neolithic dates from Smällan 2 as well as the Middle Neolithic
dates from Kyrktorp 8W give the impression of being older than previously published 14C dates, both from this region and other areas. This
could be explained by the choice of sample material with a high intrinsic
age, mixing with earlier sample material, or unfavourable sampling circumstances. In this case, however, that explanation is not satisfactory,
thus the dates of samples from the Grödinge excavations seem to be correct (cf. chap. 3).
Certain types of chosen sampling units or the qualities of the sampling
units, appear to result in lower or higher frequencies of expected dates.
Dates of samples from hearths ought to be preceded by an opinion as to
whether the fill seems more reminiscent of the Stone Age (low incidence
of soot and charcoal) or Bronze/Iron Age (high incidence of soot and
charcoal). The risk of mixing of non-contemporaneous sample material in
layers makes the dates of samples from layers uncertain.
The selection of type of sample material has been of great importance.
Certain sample materials have given high frequencies of unexpected
dates. Seeds exhibited higher frequencies of unexpected dates, possibly
because they are lighter and can be deposited in false contexts more easily than, for example, carbonised wood. Species identification of charcoal
samples before dating has indicated, as an initial result, that we can assume that certain tree species were not used during certain periods even if
available (cf. chap. 12).
Birch (Betula), for example, has provided dates from the Iron Age,
though sampled in Stone Age contexts. Spruce (Picea) has provided dates
from the Medieval or historical period though sampled in Iron Age contexts. The intrinsic age of wood samples has not appeared to have had any
influence on the frequency of unexpected dates, possibly because the sitespecific objectives allowed such great variation of each date that dates of
samples with a high intrinsic age corresponded to the expected results.
FINAL REMARKS
The dates from the Grödinge excavations have considerably increased the
basis for discussing the 14C chronology of Stone Age settlement sites in
Eastern Middle Sweden. These new dates, together with the previously
published dates, however, do not give continuous 14C dates for all Stone
Age phases in the region. Still a great number of dates have to be carried
out to establish a statistically reliable 14C chronology. As the number of
dates rise, a greater variety of sampling sites, sampling units and sample
materials will be the result. The Grödinge investigations have resulted in
a number of unexpected dates due to seemingly unpredictable errors concerning the selection of samples. Through the investigations the knowledge of Stone Age sites being mixed with Iron Age remains have been
built up. This will increase the need for elimination of error factors before
carrying out comparisons of 14C dates from archaeologically determined
Stone Age contexts, in the future.
Södertörn—Interdisciplinary Investigations of Stone Age Sites in Eastern Middle Sweden 15
Chapter 5
TABles
Table 5:1. Table of the distribution of the datings
of the Grödinge excavation between the different laboratories.
Lab.
Ua
St
U
Number of samples
68
13
8
Table 5:2. Comparisons between unexpected dates
from the Grödinge excavations, sorted by prehistoric period.
Expected Date
Stone Age
Stone Age period
Stone Age
Iron Age
Iron Age
Uncertain
Result
Iron Age
Unexpected Stone Age period
Recent
Stone Age
Medieval/Recent
% of unexp dates
39 %
22 %
6 %
11 %
11 %
11 %
Table 5:3. Table of the TL dates from the Grödinge excavations
and their distribution between the sites.
Eklundshov
Kyrktorp, subarea 9B
Kyrktorp, Hillfort
6 datings
1 dating
2 datings
16 Södertörn—Interdisciplinary Investigations of Stone Age Sites in Eastern Middle Sweden
Figures Chapter 5
figures
CAL BP
U–4490
U–4491
Ua–1381
Ua–1380
Ua–1382
Ua–339
Ua–1379
Ua–4492
Ua–4493
Ua–1378
Ua–1377
Ua–340
Ua–1376
Ua–1606
Ua–1696
Ua–1607
Ua–1697
Ua–1805
Ua–1698
Ua–1702
Ua–1807
Ua–1699
Ua–1806
Ua–1693
Ua–1700
Ua–1694
Ua–1701
Ua–1808
Ua–1695
Ua–1383
Ua–1384
Ua–1385
Ua–1386
U–4495
U–4496
Ua–1412
Ua–1730
Ua–1397
Ua–1411
Ua–1410
Ua–1409
Ua–1408
Ua–1407
Ua–1406
Ua–1405
Ua–1404
Ua–1403
Ua–1809
St–11837
St–11838
St–11839
U–4497
St–11842
St–11844
Ua–1413
St–11845
Ua–1400
St–11848
Ua–1399
Ua–1608
Ua–1609
Ua–1610
Ua–1402
Ua–1401
St–11840
U–4494
St–11841
St–11843
St–11846
St–11847
St–12571
Ua–1706
Ua–1707
Ua–1703
Ua–1704
Ua–1705
St–12465
Ua–1161
Ua–1708
Ua–1398
Ua–1680
Ua–1802
Ua–1681
Ua–1804
Ua–1682
Ua–1683
Ua–1684
Ua–1803
Ua–1830
Ua–1831
7000
6000
5000
4000
3000
2000
1000
BC/AD
1000
CAL AD
Eklundshov
Smällan 1
Smällan 2
Kyrktorp 8W
Kyrktorp 9B
Kyrktorp 9A
Kyrktorp Fen
Kyrktorp Hill Fort
Svalsta 2:1
Kvedesta
Fig. 5:1. Compilation of the calibrated radiocarbon dates from the Grödinge excavations (2 σ).
Södertörn—Interdisciplinary Investigations of Stone Age Sites in Eastern Middle Sweden 17
Chapter 5 Figures
BP
Dalkarlstorp
Hedbo
Hulu
Sjövreten
Vallby
Hjulberga
Alvastra
Ås
Överåda
Brunn
Korsnäs
Säter
Vadsbron II
Skuggunge sn
Tibble II
Björklinge sn
Tibble III
Björklinge sn
Torslunda
Tierps sn
7000
6000
5000
4000
Lu-748
Lu-750
Lu-776
Lu-777
Lu-778
Lu-1025
Lu-982
St-3669
St-4057
St-4054
St-4056
St-4055
St-4457
St-4458
St-4459
St-4711
St-4856
St-4857
St-4914
St-4916
St-4917
Lu-1319
Lu-1320
Lu-1434
St-9
St-15
U-2734
U-2735
U-2736
U-2737
U-2738
St-7992
St-7993
St-7994
St-7995
St-7996
St-7997
St-7998
St-7999
St-8000
St-8001
St-8002
St-8003
St-8004
St-8005
St-1961
U-2112
St-2953
St-3422
St-3427
St-3428
St-3429
Lu-1282
Lu-1283
Lu-1284
Lu-1285
Lu-1286
Lu-1287
St-475
St-5209
St-5210
St-5591
St-5592
St-5587
St-5588
St-5585
St-5586
St-5589
St-5590
Fig. 5:2. Published dates from Stone Age sites in Eastern Middle Sweden and time scale (1 σ).
18 Södertörn—Interdisciplinary Investigations of Stone Age Sites in Eastern Middle Sweden
3000
2000
1000
Figures Chapter 5
BP
BP
8000
7000
6000
5000
4000
3000
2000
1000
Eklundshov 1
Smällan
Kyrktorp
Kvedesta
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
Fig. 5:3. Compilation of the uncalibrated radiocarbon dates
from the Grödinge excavations (1 σ).
Södertörn—Interdisciplinary Investigations of Stone Age Sites in Eastern Middle Sweden 19
0
Chapter 5 Figures
1
U-4490
16
Ua-1607
31
Ua-1384
46
Ua-1404
61
Ua-1609
76
Ua-1705
2
U-4491
17
Ua-1697
32
Ua-1385
47
Ua-1403
62
Ua-1610
77
St-12465
3
Ua-1381
18
Ua-1805
33
Ua-1386
48
Ua-1809
63
Ua-1402
78
Ua-1161
4
Ua-1380
19
Ua-1698
34
U-4495
49
St-11837
64
Ua-1401
79
Ua-1708
5
Ua-1382
20
Ua-1702
35
U-4496
50
St-11838
65
St-11840
80
Ua-1398
6
Ua-339
21
Ua-1807
36
Ua-1412
51
St-11839
66
U-4494
81
Ua-1680
7
Ua-1379
22
Ua-1699
37
Ua-1730
52
U-4497
67
St-11841
82
Ua-1802
8
Ua-4492
23
Ua-1806
38
Ua-1397
53
St-11842
68
St-11843
83
Ua-1681
9
Ua-4493
24
Ua-1693
39
Ua-1411
54
St-11844
69
St-11846
84
Ua-1804
10
Ua-1378
25
Ua-1700
40
Ua-1410
55
Ua-1413
70
St-11847
85
Ua-1682
11
Ua-1377
26
Ua-1694
41
Ua-1409
56
St-11845
71
St-12571
86
Ua-1683
12
Ua-340
27
Ua-1701
42
Ua-1408
57
Ua-1400
72
Ua-1706
87
Ua-1684
13
Ua-1376
28
Ua-1808
43
Ua-1407
58
St-11848
73
Ua-1707
88
Ua-1803
14
Ua-1606
29
Ua-1695
44
Ua-1406
59
Ua-1399
74
Ua-1703
89
Ua-1830
15
Ua-1696
30
Ua-1383
45
Ua-1405
60
Ua-1608
75
Ua-1704
90
Ua-1831
Table to Fig. 5:3. List of lab numbers for the dates from the Grödinge excavations.
Ekl
Smä 1 - A
Smä 1 - L
Site
Smä 2
Unexpected
Kyr 8V
Expected
Kyr 9B
Kyr 9A
Kyr EY
Kved
0
20
40
60
80
100
Percentage
Fig. 5:4. Diagram of expected and unexpected dates from the Grödinge
excavations, sorted by site.
20 Södertörn—Interdisciplinary Investigations of Stone Age Sites in Eastern Middle Sweden
Figures Chapter 5
Sample units
Layer
Unexpected
Expected
Construction
0
20
40
60
80
100
Percentage
Hearth
Construction
Pit
Unexpected
Lens
Expected
Posthole
Fig. 5:5. Diagram of expected
and unexpected dates from the
Grödinge excavations, sorted by
sample unit.
Konc
0
20
40
60
80
100
120
Percentage
Sample material
Wood
Unexpected
Seed
Expected
Hazelnut
shell
0
20
40
60
Percentage
80
100
Fig. 5:6. Diagram of expected
and unexpected dates from the
Grödinge excavations, sorted by
sample material.
Södertörn—Interdisciplinary Investigations of Stone Age Sites in Eastern Middle Sweden 21
Chapter 5 Figures
Internal age
50 yrs
Fig. 5:7. Diagram of expected and
unexpected dates from the Grödinge
excavations, sorted by the internal
age of the sample material.
40 yrs
Unexpected
Expected
25 yrs
1 yr
0
20
40
60
80
100
Percentage
Pinus silvestris
Wood species
Picea abies
Salix sp
Populus sp
Unexpected
Corylus avellana
Expected
Betula
Alnus
Fig. 5:8. Diagram of expected
and unexpected dates from the
Grödinge excavations, sorted by
wood species.
Ulmus
Wood,
indef.
0
20
40
60
Percentage
8000 BP
U–4491
Ua–1380
Ua–1382
Ua–339
U–4493
Ua–1378
Ua–1377
Ua–340
Fig. 5:9. Uncalibrated radiocarbon dates and TL dates from A2 at
the Eklundshov site.
R–864102 (TL date)
R–864103 (TL date)
22 Södertörn—Interdisciplinary Investigations of Stone Age Sites in Eastern Middle Sweden
80
100
7000 BP
120