Identifying Migration: Strontium Isotope
Studies on an Early Bell Beaker Population
from Le Tumulus des Sables, France.
Ceridwen A Boel
Honours thesis submitted as part of the B.A. (Hons) degree completed in
the School of Archaeology and Anthropology, in conjunction with the
Research School of Earth Sciences, Australian National University,
Canberra.
24th
October 2011
Statement of Authorship
I certify that this is my own original work. No other person’s work has been used, in
part or whole, unless otherwise acknowledged in the text.
Name: Ceridwen Amy Boel
Date: 24th
October 2011
Signature:
i
Abstract
______________________________________________________
Strontium isotope ratios (87
Sr/86
Sr) can be used to trace the migration of people
and animals across geologically different regions. This study has applied
strontium isotope analysis to teeth from 16 adults and 8 juveniles from what
has been identified as an early Bell Beaker (Chalcolithic, 2500 – 2000 BC) site
at Le Tumulus des Sables in south-west France. The analysis was primarily
conducted using laser ablation ICP-MS, to determine U, Th and Sr elemental
concentrations and Sr isotope ratios. Four of the teeth were also analysed using
solution ICP-MS for comparison with the laser ablation results. Significant
offsets in the Sr isotope ratios were identified between the laser ablation and
solution methods of analysis, and the correction for this resulted in large
uncertainties (up to 0.6%). Despite this, most teeth showed a clear difference
between the enamel and the overprinted dentine, suggesting mobility. The
dental results were compared to a Sr isotope map of the Médoc region, created
using a set of soil samples collected from the major geologic units and from the
archaeological site. These were also analysed using solution ICP-MS. The
different geologic regions separated well according to Sr isotope ratios, with
the exception of the Holocene costal sediment. The Sr isotope ratio range
within the Médoc region was found to be very large, encompassing all of the
dental Sr values. The variation in the enamel signatures suggested a high
degree of mobility, but due to the large regional Sr range it was impossible to
distinguish migration from beyond the Médoc from mobility within the region.
If the individuals were from outside the Médoc, the Sr isotope ratios indicate
that they are most likely to have come from the east of the Médoc. Origins to
ii
the south in are unlikely, as are origins in mountainous areas such as the
Pyrenees and the Massif Central. The results from this study indicate that
archaeological soil cannot be considered to provide a reliable local range, and
highlights the importance of regional mapping in Sr isotope studies.
iii
Acknowledgements
______________________________________________________
This honours project would not have been possible without the support,
guidance, and assistance of a number of people. Firstly, I am indebted to my
supervisors Rainer Grün, Dougald O’Reilly, and Matthew Spriggs, for their
support and encouragement, and for helping me to negotiate the careful balance
between two related but very different disciplines, Archaeology and Earth
Sciences. Thanks also to Malte Willmes and Ian Moffatt for their assistance not
only in the lab and field, but in the office as well. Their assistance with the
practical components, as well as in refining my thoughts and ideas, has been
invaluable.
Thank you to Patrice Courtaud from the University of Bordeaux, for providing
the soil and teeth samples from Le Tumulus des Sables, as well as helping me
to understand the site itself. Thank you for allowing me to be a part of the
project, and also for giving me the opportunity to come into the field and see
the site of Le Tumulus des Sables as well as another excavation first hand.
Thanks also to Philippe Rossi from the BRGM in Orléans, for providing us
with, and helping us to understand, the geological maps of the region.
My thanks to the staff and students of the Research School of Earth Sciences,
for their assistance, support and acceptance, even though I came from the other
side of the campus. A special thanks to Les Kinsley and Linda McMorrow, for
all of their help operating and understanding the Neptune, Varian and Vista,
and to Les for helping me to make sense of the solution spreadsheet. My
sincere thanks also to Steve Eggins, for helping me to understanding the laser
iv
ablation method and to make sense of all of the raw data, even when you had a
thousand other things to do!
Last but certainly not least, thank you to my wonderful partner, Gerard
Atkinson. Thank you for your unconditional love and support, for picking me
up as late as 2am after long nights in the office/lab, and for teaching me to
drive so you wouldn’t have to do it again!
v
Contents
______________________________________________________
Abstract………………………………………………………………..……….i
Acknowledgements………………….……………………………….…..…...iii
Contents…………………………………………………………………….….v
List of Figures………………………………………………………..…...…viii
List of Tables……………………………………………………………….….x
__________________________________________________________
Chapter 1: Introduction………………………………………..………1
1.1. Significance of the research.….………………………………………….1
1.2. Aims……………………………………………….………………………2
1.3. Site description……………………………………….………………...2
1.3.1. Le Tumulus des Sables…………………………...……………...2
1.3.2. Regional geology……..…………………………….……………6
1.4. Thesis overview…………………………………………………………7
__________________________________________________________
Chapter 2: Background……………………………………………….8
2.1. The Bell Beaker Phenomenon…………………………………..……….8
2.1.1. What is the Bell Beaker phenomenon?.........................................8
2.1.2. The Bell Beaker debate……………………………….……11
2.2. Strontium as an archaeometric tool………………………………..…..12
2.2.1. Basic strontium chemistry…………………………………….12
2.2.2. Incorporation into the body…………………………………..15
2.2.3. Mapping………………………………………………………...15
vi
2.2.4. Diagenesis and the identification of migration…………………18
2.3. Previous applications…………………………………………………..21
__________________________________________________________
Chapter 3: Methodology……………………………………………...23
3.1. Sample collection………………………………………………………..23
3.2. Sample preparation……………………………………………………..27
3.2.1. Cleaning………………………………………………………..27
3.2.2. Soil……………………………………………………………...28
3.2.3. Teeth……………………………………………………………29
3.2.3.1. For laser analysis…………………………………29
3.2.3.2. For solution analysis……….…………..………..30
3.3. Sample analysis………………………………………………………….30
3.3.1. HelEx laser system……………………………………………..31
3.3.2. Varian Vista ICP-AES - Elemental concentrations (Soil)……...32
3.3.3. Varian ICP-MS – Elemental concentrations (Teeth)…………...33
3.3.4 Neptune ICP-MS – Isotopic composition………………………36
__________________________________________________________
Chapter 4 : Resul t s……………………… …………………39
4.1. Soil…………………..………………………………………………….39
4.1.1. The Médoc region………………………………………………39
4.1.2. Le Tumulus des Sables………………………………………40
4.2. Teeth…………………………………………………………………….42
4.2.1. Elemental concentrations (Varian)……………………………43
4.2.2. Isotopic composition (Neptune)………………………………46
vii
4.2.2.1. Laser………………………………………………………...46
4.2.2.2. Solution……………………………………………………49
4.2.3. Examples……………………………………………………….53
__________________________________________________________
Chapter 5: Discussion…………………………………………………62
5.1. Soil analyses………………………………………………………… .62
5.1.1. The Médoc region………………………………………………62
5.1.2. Le Tumulus des Sables…………………………………………64
5.2. Teeth analyses………………………………………………………...65
5.2.1. Laser vs. solution…………………………………………...…..65
5.2.2. Locals or non-locals?...................................................................67
5.2.2.1. Enamel vs. Dentine……………………………………...….68
5.2.2.2. Dental results in the regional context…………………..…..70
5.2.2.3. Further investigation………………………………………..74
5.2.3. Implications for the technique……………………………..….77
5.2.4. Implications for the Bell Beaker………………………………..79
5.3. Summary………………………………………………………………...82
__________________________________________________________
Chapter 6: Conclusion……………………………………………..…84
6.1. Conclusions and recommendations……………………………………84
__________________________________________________________
References……………………………………………………………...88
__________________________________________________________
Appendices………………………………………………………….…98
__________________________________________________________
viii
List of Figures
______________________________________________________
Figure 1.1.: Image of Saint-Laurent Médoc……..……………...……….……..5
Figure 1.2.: Summary plan of the excavations…………………..……………..5
Figure 1.3.: Geological map of the region, located on a larger map of
France…………….…………………………………………………….7
Figure 2.1.: The approximate distribution of the Bell Beaker Phenomenon
known from archaeological sites…………...……………..…………..10
Figure 2.2.: Periodic table of the elements………………………..…………..14
Figure 3.1.: Locations of the soil samples taken from the site of Le Tumulus
des Sables…………………………………………………………….24
Figure 3.2.: Geologic map of the Médoc and surrounding region, showing
sample locations for this study (F11-188 – F11-198) and others
taken in this region for related research……….....………...…………25
Figure 3.3.: Examples of two photographs, before any preparation and after
analysis, while still loaded in the ring……………………….………..30
Figure 3.4.: The ANU HelEx laser ablation setup…………….…….………..32
Figure 3.5.: Schematic diagram of an ICP-AES……………….……..……....33
Figure 3.6.: Schematic diagram of a laser ablation cell connected to a
quadrupole ICP-MS………………………………………….………..34
Figure 3.7.: Schematic diagram of a Finnigan MAT Neptune……...……..…36
Figure 4.1.: Graphs of the elemental concentrations and isotopic composition,
along with an image of the tooth (SLMEM1007)………………...….54
Figure 4.2.: Graphs of the elemental concentrations and isotopic composition,
along with an image of the tooth showing the spots made for
ix
Neptune analysis (SLMEM1192)……………………….….…...……57
Figure 4.3.: Graphs of the elemental concentrations and isotopic composition,
along with an image of the tooth showing the spots made for Neptune
analysis (SLMEM 491)……………………….………………..……..59
Figure 4.4.: Graphs of the elemental concentrations and isotopic composition,
along with an image of the tooth (SLMEM112)…………………..….61
Figure 5.1.: Measured 87
Sr/86
Sr ranges for each geologic unit in the Médoc
peninsula and the site of Le Tumulus des Sables………….……….…63
Figure 5.2.: Measured 87
Sr/86
Sr ratios for each geologic unit in the Médoc
peninsula and the offset adjusted enamel and dentine ranges (errors
included)…………………..……………………………………….….71
Figure 5.3.: Geological map of France around the Médoc……………………73
x
List of Tables
______________________________________________________
Table 3.1.: Sediment description for all soil samples………………………...26
Table 4.1.: 87
Sr/86
Sr ratios with voltages and errors for the samples gathered
during fieldwork. Includes standards (SRM987) measured during
the analyses……………………………………..……………………40
Table 4.2.: 87
Sr/86
Sr ratios for the first 7 soil samples including errors, and
standards (SRM987) measured intermittently during solution
analyses….……………………………………………………………41
Table 4.3.: 87
Sr/86
Sr ratios with voltages and errors for second batch of soil
samples from the site. Includes standards (SRM987) measured
during the analyses……………..…………………………………….42
Table 4.4.: U, Th and Sr concentrations in all teeth (averages across high and
low zones)………………………………………………………........45
Table 4.5.: 87
Sr/86
Sr ratios for the enamel and dentine of each tooth
(averages from appropriate locations), including errors…………..….48
Table 4.6.: Average 87
Sr/86
Sr values from standard measurements taken at
each interval (minimum of three in each group)……...………….…..49
Table 4.7.: 87
Sr/86
Sr values for the teeth analysed by solution MC-ICP-MS
including errors and standards………..…………………………...….51
Table 4.8.: 87
Sr/86
Sr values provided by solution, by laser analysis selecting
The appropriate zones, and by laser analysis using all values. The
differences between laser and solution, and laser (all values) and
solution, are provided for comparison…….………….………….......51
Table 4.9.: Laser 87
Sr/86
Sr values, with average offsets subtracted………....52
1
Chapter 1
Introduction __________________________________________________________
1.1. Significance of the research
Stable strontium isotope analysis has been used to gather information on
geological and ecological systems and processes for decades (e.g. Åberg et al.,
1999, Bain and Bacon, 1994, Karim and Veizer, 2000, Widerlund and
Andersson, 2006, Capo et al., 1998) It is only comparatively recently, however,
that researchers have begun to apply it in an archaeological context (Ericson,
1985). As such, it is hardly surprising to find that the scope of application and
depth of potential of this technique are still being realised. Of the numerous
archaeological applications of the technique, including tracing the origins and
trade patterns of pottery or determining the provenance of textiles, perhaps the
best known and best developed application is the analysis of teeth to identify
and possibly trace migration. The origin and nature of the Bell Beaker culture
in Europe has been a topic of debate for decades and, despite considerable
progress in our understanding of the phenomenon, is yet to be adequately
resolved. Through the use of strontium isotope analysis, this study provides
some insight into the mobility of what is thought to be a Bell Beaker
population from the site of Le Tumulus des Sables, and offers to continue
improvement in our understanding and utilisation of the technique.
2
1.2. Aims
The primary aim of this study is to determine whether the individuals from the
study site are of local or non-local origin. Within and relating to this primary
aim, there exist a number of secondary aims. These are:
i) To compare the juvenile and adult samples in an attempt to detect a
difference in patterns of mobility.
ii) To expand of our understanding of the Bell Beaker phenomenon as a whole.
iii) To compare the results obtained by two different extraction methods, laser
ablation and solution, to detect differences in the data sets and aid in the
evaluation of their usefulness, accuracy and viability.
1.3. Site description
1.3.1. Le Tumulus des Sables
The site of Le Tumulus des Sables is located in the town of Saint-Laurent
Médoc, in the Médoc region to the north west of Bordeaux (45°8‟44”N,
0°49‟37”W, see Figure 1.1.). The site and excavations have been fully
documented in yearly site reports and a poster (Chancerel and Courtaud, 2006,
Courtaud et al., 2008, Courtaud et al., 2007, Courtaud et al., 2010, Courtaud et
al., 2009a, Courtaud et al., 2009b). The site, located in what was a part of the
local school grounds, was discovered comparatively recently when human
remains were accidentally uncovered by the school children. The burial itself
was contained within a roughly circular raised mound 7x8m in diameter and
50cm high at the peak. The excavators believe that this mound was natural, and
3
that the burial was placed on it. The site is also distinguished by the colour of
the sediment, being mostly yellowish brown (10YR 5/4, 5/6, 6/6) to dark
yellowish brown (10YR 4/4, 4/6), while being surrounded by a sterile sand of
more gray/white hues that is at least 2m deep. So far as was visible while
conducting fieldwork in the region, the region is dominated seemingly
exclusively by sandy soils of greyish colour, ranging from almost white,
through greyish browns, to nearly black. The excavators theorise that the
brownish soil is the result of acid released by the limestone which occurs at the
site.
The burial itself is 30cm deep, and the remains are highly disarticulated and
fragmented; anatomical connections between associated bones were impossible
to establish. The archaeological deposit associated with the collective burial is
not confined to the mound itself, and is irregular in shape as pictured in Figure
1.2. Some stratigraphy is preserved, although it is not evident within the burial
context itself and is not uniform across the site. The significant fragmentation
of the remains may be in part due to bioturbation, although it is thought that
this played a minimal part in site disturbance. The presence of patches of
darker yellow and brown that have not been mixed in with the rest of the soil
are evidence for the integrity of the deposit. The skeletal fragmentation may
also be in part due to the nature of the burial, as it likely originally belonged to
a culture that predated the use of the site by Bell Beaker people. Bell Beaker
graves and tomb re-use will be discussed further in section 2.1.1. Some
artefacts and bones were able to be collected from the surface, most likely due
to a combination of some turbation and weathering.
4
The site was identified as having been used by the Bell Beaker people on the
basis of distinctive material discovered within the burial. This has been
confirmed by the dating of a bone fragment, yielding a calibrated date of 2490-
2290BC. Two dates were also obtained from coal towards the bottom and top
of the excavation, providing calibrated dates of 6072-5985BC and 1395-
1214BC respectively. The older age, corresponding to the Mesolithic, surprised
the excavators somewhat given that there was no archaeological indication of
occupation in this period. The ceramic finds also indicated occupation
extending from the Neolithic, through the Bell Beaker period, and into
protohistoric and Iron Age periods. The extent of the age range of the site and
the poor stratigraphy prevent the secure identification of a particular sample as
belonging to the Bell Beaker without individually dating it. Given our
understanding of Bell Beaker burial practices in this area, it seems likely that a
proportion of the individuals may belong to the Bell Beaker; however, the most
that can be said at this point is that Bell Beaker associated artefacts have been
identified at the site and that at least one individual was dated to this period of
time.
5
Figure 1.1.: Saint-Laurent Médoc (Google Earth 2011). Le Tumulus des
Sables is marked in red.
Figure 1.2.: Summary plan of the excavations (from Courtaud et al., 2010)
6
1.3.2. Regional geology
Saint-Laurent Médoc is situated about 40km north-west of Bordeaux on the
Médoc peninsula in southwest France. The Médoc peninsula, situated between
the Atlantic coast and the Gironde, is predominantly composed of Quaternary
sand, clay and gravel sediment, with a band of Holocene sands, clays, pebbles
and gravel along the shorelines of the Atlantic Ocean and the Gironde. Some
small patches of Eocene and Oligocene limestone, conglomerates and
sandstone occur towards the eastern edge. The region is principally used for
tree plantations and vineyards; however, some crop agriculture is also
undertaken. The whole area is quite flat and low lying, making it quite difficult
to locate rock outcrops. This has implications for mapping techniques and our
interpretation of the soil results, which will be discussed in later chapters.
Particularly towards the western edge of the peninsula, most variation in
altitude is attributable to sand dunes. Like the sediment from Le Tumulus des
Sables, the sediment in the whole region is predominantly sandy, with some silt,
clay and gravel. The majority of the soil is grey to dark grey, with some
greyish browns where the soil has a larger organic component.
7
Figure 1.3.: Geological map of the region, located on a larger map of
France (adapted from Bureau de recherches géologiques et minières, 2005,
GoogleEarth, 2011)
1.4. Thesis overview
The following chapter provides an overview of the previous work and
background information relevant to this study. This covers the fundamentals
and history of the Bell Beaker phenomenon and debate, the principals and
techniques of strontium isotope analysis for tracing migration, and the previous
applications of this technique to Bell Beaker populations. Chapter 3 details the
methods used in this study, including sample collection, preparation, and
analysis processes and techniques. The results are presented in chapter 4, and
these are subsequently discussed in depth and related back to the
archaeological problem in chapter 5. Chapter 6 provides a summary and
conclusion, as well as suggestions for further research.
8
Chapter 2
Background _______________________________________________________________
2.1. The Bell Beaker phenomenon
2.1.1. What is the Bell Beaker phenomenon?
The term “Bell Beaker” was initially used to describe a distinctive type of
ceramic ware, but has since been used to describe an artefact assemblage, a
cultural complex, a group of people, and a period in time (e.g. Benz et al., 1998,
Heyd, 1998, Price et al., 1998, Shennan, 1976, Shennan, 1977). Bell Beaker
ceramic ware is characterised by inverted-bell shaped vessels, commonly
referred to as beakers. Since the initial descriptions of the ceramics in the 19th
century, (Benz et al., 1998), a number of other artefact types have come to be
recognised as part of a Bell Beaker assemblage, including some of the first
gold and bronze objects in Europe, jet, amber and obsidian ornaments, V-
perforated buttons, tanged daggers, and archery equipment including projectile
points and stone wrist guards (Desideri, 2008, Price et al., 1998, Price et al.,
2004, Vander Linden, 2006). Some researchers have also associated specific
morphological characteristics with the Bell Beaker people. Brachycephaly, a
condition in which the head is short and broad, is one such trait, having been
observed to occur frequently among Bell Beaker populations (Benz et al., 1998,
Turek, 1998). The causes for this have not yet been thoroughly investigated,
however, and it could simply be the result of diet, socioeconomic factors, or
methods of partner selection. Dental non-metric traits have been studied on
Bell Beaker populations, with results suggesting population discontinuity
9
between the Bell Beaker and preceding cultures in most areas (Desideri, 2008,
Desideri and Besse, 2010).
The Bell Beaker phenomenon (BBP) extends across most of Europe, occurring
around the transition from the Neolithic to the Bronze Age (Figure 2.1.),
although it manifests at different times in different areas. As a whole, it is
thought to have developed around 2,900 BC and persisted until roughly 1,800
BC (Desideri, 2008). While there is still some debate on this matter, it is
considered likely that the BBP originated in the Iberian Peninsula (Lemercier,
2004, Haak, 2011, Desideri, 2008). In addition to chronological variations in
the manifestation of the phenomenon, there are also significant spatial
variations. These variations occur most prominently between the eastern and
western domains, and are evident in a number of aspects of the phenomenon. It
goes beyond the variation in material culture (e.g. Benz et al., 1998), extending
to burial traditions, physical characteristics, and possibly even isotopic data.
Most eastern Bell Beaker burials are single inhumations; however, this
tradition did not take hold in western Europe until much later. For much of the
Bell Beaker period, the western domain was characterised by the re-use of
megalithic tombs of the preceding cultures (Benz et al., 1998, Chambon, 2004,
Vaquer, 1998). These are mass inhumations of variable size, and graves
containing 20-30 individuals, as seen at Le Tumulus des Sables, are not
uncommon (e.g. Heyd, 1998). While the Bell Beaker phenomenon is often
represented in collective graves, there are only a few cases where a particular
body can be identified with certainty as a Bell Beaker individual. This is at
least in part due to the way the tombs were re-used, and this is itself is quite
10
variable. The previous occupants may have been pushed aside, the new
occupants may simply have been placed on top of or alongside them, or the
tomb may have been partially or completely emptied first (Chambon, 2004). In
terms of morphology, significant variation between the east and west was noted
in dental non-metric traits, reflecting different patterns of settlement,
population exchange and population development between the two spheres
(Desideri, 2008). While the variations are most significant between the eastern
and western spheres, there are also noticeable differences between smaller
regions. This, along with other factors, gives rise to some question as to
whether the BBP truly represents a culture in the accepted archaeological sense
(see 2.1.2.). The term „phenomenon‟ seems to be universally acceptable and
avoids the implication of alignment in the debate, hence its use in this context.
Figure 2.1.: The approximate distribution of the Bell Beaker Phenomenon
known from archaeological sites (from Vander Linden, 2006).
11
2.1.2. The Bell Beaker debate
While many explanations have been offered for the origin and nature of the
BBP, these can generally be divided into two main camps – that the
phenomenon is the result of the migration of culture bearing individuals, or that
it is instead the result of cultural diffusion, and the movement of objects and
ideas. Debate of this type is by no means restricted to the BBP, and tends to
feature quite prominently in archaeology the world over. These questions
concerning the origin and nature of the BBP became the focal point of Bell
Beaker research very early on, with debate over whether the objects were
traded or transported with mobile groups developing in 1906 (Schliz, 1906,
Benz et al., 1998). The Bell Beaker assemblage appears to be most coherent in
a funerary context, leading to the development of the “prestige goods” model
in the 1970‟s, which describes the assemblage as the material manifestation of
a Bell Beaker ethos, based upon individualistic and warlike values, and
circulated amongst the elites as a symbol of prestige and power (Benz et al.,
1998, Shennan, 1976, Shennan, 1977, Vander Linden, 2006, Bailley, 1998).
This model is one of the best known and most influential models in which
cultural diffusion and the movement of objects and ideas (rather than people) is
invoked. This model suggests that the Bell Beaker assemblage represents the
culmination or, at the very least, heightened continuation of late Neolithic
social competition. No break with the preceding cultures is recognized, just the
accumulation of non-functional items for which a prestige explanation is
necessarily invoked.
12
Despite continuity in settlement patterns and subsistence techniques, however,
there are strong arguments against a supposition of cultural continuity. Conflict
in the later neolithic does not reach a climax in the Bell Beaker period; in fact,
evidence of conflict wanes, and significant diversity in ornamentation and
weapons is replaced by homogeneity (Vander Linden, 2006). The idea that Bell
Beaker artefacts were traded amongst the elites is further undermined by
evidence for the local production of pottery, using local materials. This
indicates local know-how, which in turn indicates the mobility of people
bringing this knowledge (Benz et al., 1998, Vander Linden, 2007a, Vander
Linden, 2007b). Both artefacts and site data show the BBP to be a cultural
spread, rather than diffusion, with phases of exploration, settlement and
acculturation of local populations. Some argue that the spread of the Bell
Beaker allowed the development of lines of communication, facilitating the
exchange of objects, ideas and people (e.g. Lemercier, 2004), while others
believe that it was the establishment of this network that allowed the spread of
the BBP; the integration of individuals or groups would have led to the
emergence of Bell Beaker specific settlements, and it is then that it becomes a
true culture (e.g. Benz et al., 1998). Either way, it is agreed that during the Bell
Beaker period that exceptional lines of communication were established.
The idea of human mobility is further supported by a major strontium isotope
study on Bell Beaker people in Germany, Hungary, Austria and the Czech
Republic (Grupe et al., 1997, Grupe et al., 1999, Price et al., 1994, Price et al.,
1998, Price et al., 2002a, Price et al., 2004), which echoes the previously
mentioned study on dental morphology (Desideri, 2008, Desideri and Besse,
13
2010). This has been further demonstrated by recent work which has not yet
been published demonstrating genetic discontinuity between Bell Beaker
populations and their predecessors (Haak, 2011, pers. comm.). This genetic
work indicates a higher affinity with modern Iberian populations, supporting
the notion that the Bell Beaker people originated in this area (e.g. Desideri,
2008, Lemercier, 2004). In France, particularly, the time lag of several hundred
years between the appearance of the BBP in the south and north would seem to
support this (Salanova, 1998).
2.2. Strontium as an archaeometric tool
2.2.1. Basic strontium chemistry
Strontium (Sr) is a member of the alkaline earths, group IIA of the periodic
table (Figure 2.2.), and like all elements in this group it readily forms ions with
a charge of 2+. Almost all rocks contain strontium in detectable quantities, and
its distribution is controlled by factors such as the extent to which Sr2+
can
substitute for Ca2+
(also a group IIA element, with a similar ionic radius), and
the degree to which it can be captured in the place of K+ ions in potassium
feldspar (Faure and Powell, 1972). Strontium exists in both stable and unstable
isotopic forms; it is the stable isotopes which are used to trace mobility.
Isotopes are forms of the same element with different numbers of neutrons in
the nuclei, giving them variable atomic weights. The number of protons
remains unchanged, so they retain the same chemical properties. Strontium
occurs naturally in four stable isotopic forms, 88
Sr, 87
Sr, 86
Sr and 84
Sr, of
varying natural abundance (Faure, 1986). Of these four, only 87
Sr is radiogenic,
14
being produced by the decay of 87
Rb over a half life of roughly 4.88 x 1010
years (Bentley, 2006). As a result, the proportion of 87
Sr in a substrate is
variable with respect to the other stable strontium isotopes, which occur in
fixed proportions. It is the 87
Sr/86
Sr ratio that is generally used, being
determined both by the relative concentrations of strontium and rubidium in the
rock, as well as by the age of the formation (that is, the time over which the
87Rb in the rock has been decaying to
87Sr). As rock composition is
geographically variable, so too is the 87
Sr/86
Sr ratio. This makes it possible, in
principle, to source individuals and trace mobility (Beard and Johnson, 2000,
Bentley, 2006, Ericson, 1985, Ericson, 1989).
Figure 2.2.: Periodic table of the elements. Red is used to mark strontium
(Sr) and the alkaline earths.
(from http://www.geokem.com/images/pix/pt.gif)
15
2.2.2. Incorporation into the body
There are a number of factors which influence the incorporation of strontium
into the body. As mentioned above, the distribution of Sr in rocks is partially
determined by the extent to which Sr2+
substitutes for Ca2+
in calcium-bearing
minerals. Strontium enters the body in the same way, substituting for calcium
in a number of minerals including apatite, which is a major component of teeth
and bones (Bentley, 2006, Faure and Powell, 1972). The ratio of bodily
strontium is considered to be an average of all ingested strontium; however,
there are a number of factors to take into consideration. While strontium may
substitute for calcium, the two are absorbed by the body at different rates. On
average, 19-25% of ingested strontium is absorbed during digestion, compared
to 40-80% of calcium (Sips et al., 1996). Additionally, strontium is biopurified
where calcium is not, as it plays no role in physiological processes. This further
decreases the quantity of strontium at each trophic level. With this reduction in
quantity also comes a reduction in 87
Sr/86
Sr ratio variance; however, the ratio
itself is unchanged. Fortunately, the comparative size of strontium means that
the effects of fractionation in physiological processes, in which smaller or
larger (lighter or heavier) isotopes may be favoured, are negligible (Bentley,
2006).
2.2.3. Mapping
As mentioned previously, the 87
Sr/86
Sr ratio is geographically variable. In order
for this variability to be utilised, it is necessary to create an isotopic map of an
appropriate region around the archaeological site under investigation. While
16
bedrock regions of the same type (e.g. limestone) will generally be of similar
elemental composition and have similar isotopic signatures, variations in
composition and age of the rock make it difficult to predict the Sr isotopic
signature based on the analysis of similar rock types. To complicate matters
further, the signature of the bedrock in an area is not necessarily the same as
that of the covering soil and plants. While the weathering of bedrock is the
major contributor to plant and soil 87
Sr/86
Sr ratios (Bern et al., 2005), there are
a number of factors influencing the bioavailable 87
Sr/86
Sr ratio (i.e. the Sr
entering the food chain) in any given area. Different rock types weather
differentially and may be exposed to different weathering processes and
intensities; as such their contribution to the bioavailable strontium is uneven.
The diversity of the local geology may have large impact of the signature, as
the bioavailable strontium will reflect an aggregate of the area (Budd et al.,
2004). In addition to this effect, Sr may also be contributed to the system from
other sources. Consequently, bioavailable Sr in any given area has been more
accurately described as the result of a system of inputs and outputs (Bentley,
2006). Other sources of Sr may include sediment carried by streams from
different areas, as well as the streams themselves, and atmospheric sources
such as precipitation, and dirt and dust carried by the wind. In coastal areas,
sea spray may be a contributing factor (Bentley, 2006). In a modern context,
exotic sources of Sr such as fertiliser may also contribute to, and complicate
the system further.
As demonstrated, creating the 87
Sr/86
Sr ratio map of any given area is far more
complex than simply mapping the 87
Sr/86
Sr signatures of the bedrock in the
17
area. Perhaps the most effective way of measuring the bio-available isotopic
signature of a given area is not to measure each of these individual components
and how they interact, but to measure the 87
Sr/86
Sr ratio of the fauna and flora
in the area. Due to the impact of modern contamination of the isotopic
signatures through the introduction of fertilisers, etc, the modern fauna and
flora in the area may yield a significantly different isotopic signature to the
prehistoric samples that are more likely to be of interest in an archaeological
setting. It is most useful instead to measure archaeological remains of
herbivores. Small herbivores are suitable as they have a restricted range,
reducing the impact of exotic signatures, and they develop a consistent average
87Sr/
86Sr ratio representative of the area (Bentley et al., 2004, Price et al.,
2002b). Such measurements are best conducted on a number of individuals to
provide a local range rather than a single value, as there is demonstrated
behavioural and isotopic variation even at the herd level in many animals
(Britton et al., 2009).
The above mentioned method may be ideal for the establishment of the isotopic
signature at an archaeological site, but this is not always possible. This may be
because the site is lacking in archaeological faunal remains, or due to project
limitations. Fortunately, there are other methods involving the measurement of
local rock, soil and plant signatures. There is research to suggest that even on
highly weathered soils, bioavailable strontium still predominantly reflects local
rock sources (Bern et al., 2005). As such, soil may be used as an indicator of
the local strontium range, provided it is carefully selected to avoid major
sources of contamination, such as fertilisers on farmed land.
18
2.2.4. Diagenesis and the identification of migration
When investigating faunal material, diagenesis is a key consideration. In an
archaeological context, diagenesis refers to all chemical and mineralogical
changes that a sample experiences after deposition. Skeletal material deposited
in sediment will undergo a variety of alterations, one being the exchange of
isotopes with the surrounding sediment. While some of the original Sr isotopic
composition may be preserved, diagenetic Sr displaying the local composition
may be absorbed, altering the 87
Sr/86
Sr ratio. Different types of skeletal tissue
may be affected by diagenesis to different degrees. Previously, bone and
enamel have been compared in strontium isotope studies under the assumption
that bone, which is constantly remodelling, would reflect the location in which
the individuals resided in the final years of their lives, and that the enamel
would reflect their place of residence in the early years of their lives in which it
was formed. However, given concerns about the effects of diagenesis, doubt
has been cast upon the value of bone as a source of information. Bone is porous,
and composed of small hydroxyapatite crystals mixed with roughly 30%
organic matter. This allows significant diagenetic alteration to occur. Tooth
enamel, on the other hand, is essentially non porous, and is composed of much
larger hydroxyapatite crystals with a much smaller amount of organic matter
included. As a result, tooth enamel is much harder to penetrate, and is
correspondingly much less susceptible to diagenesis (Hoppe et al., 2003).
Dentine and enamel are formed at the same time and have the same original
isotopic composition; however, dentine, like bone, is much more susceptible to
diagenesis than enamel (Budd et al., 2000). This difference can be used to
19
ascertain the influence if diagenesis, and well as to help in the identification of
migrants. If the original isotopic signature of a tooth differs from that of the
local sediment, then diagenesis will affect the 87
Sr/86
Sr ratio in the dentine and
cause it to be different to that in the enamel. If the Sr signature in the dentine
and enamel are the same but different to the local signature, they can similarly
be identified as migrants, but it can be concluded that the effect of diagenesis
has been minimal. In this, dentine performs effectively the sample function as
bone, without the unrealistic expectations of more refined chronological
tracking from bones remodelling at different rates. It is also simpler in terms of
a sample acquisition, requiring only teeth rather than additional associated
bone fragments. This is particularly useful for sites such as Le Tumulus des
Sables where the remains are quite disarticulated and associated bones are
lacking.
While enamel is less susceptible to diagenesis, it may not necessarily be
unaffected. For the investigation of the origin of an individual, it is essential to
reconstruct the original isotopic signature. It has been proposed that diagenetic
strontium may be removed through a process involving cleaning with a series
of weak acid leaches. There are concerns, however, that these may alter the
original strontium, or even cause the diagenetic strontium to partially or even
fully replace it (Bentley, 2006). In addition to the precipitation of secondary
minerals into the bone or tooth structure, it has been shown that the biogenic
apatite is also altered by diagenesis (Kohn et al., 1999).Even working on a
relatively modern sample from Vietnam, Beard and Johnson (2000) found that
they were unable to recover much of the original strontium. Hoppe et al. (2003)
20
determined that although some contaminants could be removed using the
correct preparation process, up to 80% of the diagenetic strontium remained in
bones. On the other hand, the pre treatment appeared to remove up to 95% of
the diagenetic strontium from tooth enamel.
This study pursues a different strategy. Modern teeth contain only traces of
uranium and thorium (Tandon et al., 1998); however, due to diagenesis,
archaeological skeletal tissues contain variable amounts of U and Th. Uranium
is water soluble and highly mobile, while thorium is water insoluble. As such,
the presence of any Th is the result of mechanical contamination (for example,
clay minerals in the pores of bones) while the presence of U indicates chemical
contamination. The measurement of these can be used to identify domains in
which diagenesis has occurred mechanically or chemically, and domains in
which the original Sr isotopic signature is preserved. There is no linear
correlation between uranium uptake and the uptake of other elements, like
strontium, so where any uranium is present the extent of strontium overprint
cannot be accurately quantified (Moffatt, 2011, pers. comm.). Systematic
isotope mapping of a Neanderthal tooth has shown that there are regions in the
tooth enamel (usually close to the surface) that do not contain any uranium
(Grün et al., 2008). Domains that are free of uranium, which is much more
mobile than strontium, will preserve the original strontium isotopic signature.
21
2.3. Previous applications
While the technique is still in a phase of rapid development, it has been applied
successfully to human remains a number of times in varying locations (e.g.
Knudson et al., 2004, Giblin, 2009, Bentley et al., 2007a, Cook and Schurr,
2009, Evans et al., 2010, Hodell et al., 2004, Kusaka et al., 2011, Montgomery
et al., 2000, Bentley and Knipper, 2005, Bentley et al., 2007b, Conlee et al.,
2009, Price et al., 2000, Price et al., 2006, Smits et al., 2010), including even
fossil hominins (Copeland et al., 2011, Copeland et al., 2010). A significant
amount of work has also been conducted on animal populations (e.g. Britton et
al., 2009, Balasse et al., 2002, Balter, 2008) as well as organic materials such
as wood (English et al., 2001) and wool textiles (Frei et al., 2008).
While Bell Beaker individuals have been included in strontium isotope studies
conducted on broader populations (e.g. Chiaradia et al., 2003), these have
essentially been incidental inclusions and have produced only a minor amount
of data. Only one study, by T. Douglas Price and Gisela Grupe et al. generated
a significant amount of data and gave full consideration to the interpretations
and implications of this data. This also happens to be the first strontium isotope
study conducted on Bell Beaker people. The study was conducted over the
course of ten years, beginning with a pilot study in 1994 (Price et al., 1994).
The strontium isotope composition of compact bone and molar enamel of eight
individuals were compared, sourced from two sites in Bavaria. It is the
Bavarian Bell Beaker that later formed the core of what became a much
broader study, including samples from Germany, Hungary, Austria and the
Czech Republic, which culminated in 2004 (Price et al., 2004). By this point,
22
their sample consisted of 82 individuals from 11 sites in Bavaria, five
individuals from three sites in Austria, six individuals from three sites in the
Czech Republic, and six individuals from three sites in Hungary (Grupe et al.,
1997, Grupe et al., 1999, Price et al., 1994, Price et al., 1998, Price et al., 2002a,
Price et al., 2004).
Bone and enamel were compared under the assumption that bone, which is
constantly remodelling, would reflect the location in which the individuals
resided in the final years of their lives, and that the enamel would reflect their
place of residence in the early years of their lives during formation.
Throughout the duration of the study, the authors maintained that cleaning
procedures removed sufficient diagenetic strontium from the bone for results to
be meaningful. As previously mentioned, however, there are significant
concerns about the effectiveness of these pre-treatments. The implications of
this were not considered by the authors, but fortunately the impact is not so
great as to render the conclusions entirely invalid. Given that burial usually
occurs at the final place of residence, the overprinted signature should be
similar to the biogenic signature anyway. This ten year study provides a solid
and valuable foundation for both improvements in the technique, and further
Bell Beaker research.
23
Chapter 3
Methodology
______________________________________________________
3.1. Sample collection
The teeth were collected by Dr Patrice Courtaud of the University of Bordeaux
during the excavation of Le Tumulus des Sables, and subsequently provided to
Professor Rainer Grün of the Australian National University (ANU) for
strontium isotope analysis. Of the adult samples, the LM2 (left upper second
molar) of 21 individuals was supplied. Of the juveniles, the Ldi2
(left deciduous
upper second incisor) of 8 individuals was supplied. Selecting the same tooth
from each individual ensured that none were unintentionally represented
multiple times.
The soil samples were collected over the course of a number of years. Initially,
seven samples (SLMEM 2901-2907) from the burial itself were collected by
Dr Patrice Courtaud during the excavations and sent to the ANU, following
Australian quarantine guidelines. A further 11 samples (SLMEM 2901b-2907b,
2908-2911) from the burial itself (7) and other parts of the archaeological
deposit immediately adjacent to the burial (4) were collected in the same
manner and sent to the ANU, including doubles of the first seven samples. The
sample locations were recorded, and sediment description was conducted at the
ANU (see Figure 3.1. for locations, and Table 3.1. for descriptions).
24
Figure 3.1.: Locations of the soil samples taken from the site of Le
Tumulus des Sables, adapted from Patrice Courtaud (2011 pers. comm.).
Eleven further soil samples (F11-188 – F11-198) were collected during
fieldwork in late June 2011 from carefully selected locations around the Médoc
peninsula. This was conducted with Mr Malte Willmes as part of the creation
of a broader isotopic map of France. The samples were predominantly taken
from steep roadside cuts or beneath large fallen trees to access deeper,
uncontaminated soil, and they were taken far enough from farmed or
residential land to avoid the impact of fertilisers and other modern
contaminants. They were placed so that all geologic units in the study area
were appropriately represented (Figure 3.2.). The descriptions can be found in
Table 3.1. The sampling procedure involved thorough documentation of the
location and description of the samples, which included not only soil, but
bedrock and associated plant samples. This was done according to the Research
25
School of Earth Sciences (RSES, ANU) lab and field guide for strontium
isotope analysis (Moffatt and Willmes, 2011). As mentioned previously, the
Médoc is quite flat and lacking in accessible rock outcrops, meaning that a rock
sample was only able to be collected at one of the 11 locations. Plant samples
were also collected, but neither the rock nor the plants were included in this
study due to limitations in the available time and scope of the project.
Figure 3.2.: Geologic map of the Médoc and surrounding region, showing
sample locations for this study (F11-188 – F11-198) and others taken in
this region for related research (adapted from Bureau de recherches
géologiques et minières, 2005, GoogleEarth, 2011).
26
27
3.2. Sample preparation
Samples were prepared at the Research School of Earth Sciences, ANU, with
the guidance, assistance and supervision of Professor Rainer Grün, Mr Ian
Moffatt and Miss Tegan Kelly, and the aid of Mr Malte Willmes. Preparation
was conducted according to the RSES lab and field guide for strontium isotope
analysis (Moffatt and Willmes, 2011).
3.2.1. Cleaning
All laboratory containers and equipment were chemically cleaned before use.
Pipette tips, columns, and generic glassware were cleaned with a series of
rinses in tap water and Milli-Q purified water, followed by immersion in 10-
50% HNO3 for several days. After this time, the equipment was again cleaned
with a series of Milli-Q rinses and dried in an oven at 60°C. The columns were
additionally rinsed and soaked in acetone throughout the cleaning process.
Teflon beakers and Neptune, AES and centrifuge tubes were initially immersed
in Acetone for 1-2 hours, before being soaked sequentially in 2-5% Decon
(laboratory detergent) and Milli-Q, 10-50% HNO3, 10-50% HCl and then
Milli-Q H2O, all heated to 60°C and left over night, with a series of Milli-Q
rinses between each step. To the Teflon beakers alone, a small amount of 2M
HNO3 was added to each bottle and capped beakers were heated for two days
at 60°C, followed by a number of Milli-Q rinses. All equipment was dried in
an oven and stored in a sealed container or bag.
28
3.2.2. Soil
The soil samples were baked in an oven at 60 °C for 24 hours prior to use, and
1 gram subsamples of each soil sample were carefully sieved (2mm sieve)and
measured out on equipment cleaned according to lab procedures and standards.
To leach bio-available strontium, 2.5mls of 1M ammonium nitrate (NH4NO3)
was added to each sample and they were loaded into a retsch shaking for 24
hours along with blanks containing just 0.5ml of 1M NH4NO3. They were put
into the centrifuge at 3000 RPM for no less than five minutes to separate the
liquid component, and the maximum amount of clear liquid (1-2ml) was
extracted and evaporated overnight on a hotplate at 60°C. Once the leaching
process was complete and the liquid evaporated, the samples were dissolved
again in 15 drops of distilled concentrated HNO3 to break down residual
organic matter, and left on the hotplate with the cap on for one hour to allow
full dissolution. The cap was then removed and the samples were fully
evaporated once again. Once evaporated, 2mls of 2M nitric acid was added to
each beaker, which was then placed on the hotplate for one hour with the caps
on to allow full dissolution. At this stage, 0.1 ml of each sample was removed
and added to 9.9ml 2% HNO3 for Sr concentration measurement via ICP-AES
(see section 3.3.1.1.).
Using the Sr concentration results provided by the ICP-AES, the volume of
each sample required to obtain sufficient Sr levels in the end sample was
calculated with the aid of an excel spreadsheet. The samples were then put
through iron exchange chromatography to separate the Sr from matrix elements
in the sample, particularly 87
Rb which interferes with the 87
Sr signal in the ICP-
29
MS. The samples were passed through prepared columns loaded with pre-filter,
and columns loaded with Sr specific resin. Throughout the process, the pre-
filter and Sr specific resin columns change places above one another, and a
series of acids (0.02M HNO3, 8M HCl, 2M HNO) were run through the
columns in varying order a number of times in order to preferentially retain the
Sr in the resin until a breakthrough point was reached and the Sr is released and
collected. One drop of H3PO4 was added to each sample to keep them moist
during the subsequent evaporation, as the H3PO4 will not evaporate. The day
before Neptune ICP-MS analysis, 2ml 2% concentrated HNO3 was added to
each sample, and they were transferred to 4ml Neptune vials for analysis.
3.2.3. Teeth
3.2.3.1. For laser analysis
For laser ablation sampling, teeth were cut using a fine diamond saw along the
axis which would provide the best enamel and dentine surfaces for analysis.
This varied slightly between teeth, but generally followed the buccal-lingual
(cheek to tongue) axis. A segment comprising approximately half the dentine
and enamel was removed from each tooth, leaving the remainder of the tooth
intact and minimising the damage. The teeth were then sanded lightly using
fine grained sandpaper to ensure the smooth surface required for analysis, and
loaded into standardised metal rings. Yellow-tack was used as a base to support
the teeth and hold them in place, as seen in Figure 3.3. The teeth were recorded
(length, width, thickness and weight) and photographed in high resolution
30
before preparation, after being cut, after being mounted and after analysis was
completed.
Figure 3.3.: Examples of two photographs, before any preparation (left)
and after analysis, while still loaded in the ring (right).
3.2.3.2. For solution analysis
Four of the adult teeth were additionally analysed in solution. Using a fine drill,
a small amount of the dentine and enamel were removed (approx 0.02g each)
and crushed with a mortar and pestle, and dissolved in 0.5ml of concentrated
baseline HNO3. These were left, lidded, on the hotplate over night at 60°C. The
lids were subsequently removed to allow the evaporation. Once complete, 2ml
of 2M HNO3 was added to each sample before sub-sampling for ICP-AES
along with the soil samples, followed by ion exchange chromatography and
analysis.
3.3. Sample analysis
Samples were analysed at the RSES, ANU, with the guidance, assistance, and
supervision of Professor Rainer Grün, Mr Ian Moffatt, Mr Les Kinsley, Ms
31
Linda McMorrow and Dr Steve Eggins, and the aid of Mr Malte Willmes.
Concentrations and isotope compositions were calculated from the raw data
provided by each of the analysis methods using Microsoft Excel spreadsheets
specifically formulated for the task.
3.3.1. HelEx laser system
Laser ablation analysis was conducted using the custom built ANU HelEx laser
sampling system, coupling an ArF excimer laser system (193nm; Lambda
Physik Compex 110) with one of two inductively coupled plasma mass
spectrometers (ICP-MS), a Varian-820 quadrupole ICP-MS and a Finnigan
MAT Neptune multi-collector ICP-MS (MC-ICP-MS). The ANU system and
its capabilities have previously been described in detail by Eggins et al. (1998).
In brief, a single lens is employed to project and demagnify the image of a laser
illuminated apparatus onto the sample, producing relatively sharp edged
ablation pits of controllable dimensions. The atmosphere under which ablation
is carried out is carefully controlled to be compatible with the argon ICP, an
atmospheric pressure ion source. This ensures uncontaminated transport of the
ablation products to the ICP, and the use of helium as a carrier gas maximises
the transmission. To reduce the pulsations in sample delivery resulting from the
pulsed laser ablation, a signal smoothing device is employed during
transportation of the ablation products to the ICP.
32
Figure 3.4.: The ANU HelEx laser ablation setup (courtesy of Steve Eggins)
3.3.2. Varan Vista ICP-AES - Elemental concentrations (Soil)
A Varian Vista Pro Axial ICP-AES was used to calculate the Sr concentrations
during the solution preparation process, as required during the ion exchange
chromatography. The sample is nebulised and passed through inductively
coupled plasma (a partially ionised gas to which energy is supplied by
electromagnetic induction), which atomises the sample. These atoms are
excited, and individual elements emit a characteristic wavelength when the
atoms return to their original energy level. A grating can be used to disperse
the light and separate elements, and the intensity of target wavelengths is
measured to determine quantities.
33
Figure 3.5.: Schematic diagram of an ICP-AES
(from http://www.balticuniv.uu.se/environmentalscience/ch12/chapter12_
g.htm)
3.3.3. Varian ICP-MS - Elemental concentrations (Teeth)
In ICP-MS, an inductively coupled plasma is used to atomise and ionize the
sample – in this case, the ablation product. The vaporised sample particles are
passed through the ICP using argon as a carrier gas. Ions then pass through a
small sample orifice, and are accelerated by a pumped vacuum system into an
expansion chamber. Ions are extracted from the chamber using a skimmer cone,
and are shaped and focused with ion lenses. The Varian-820 ICP-MS uses a
quadrupole mass filter composed of four parallel metal rods, through which the
ion stream is directed. The voltages of the rods are selected and varied so that
only ions of specific mass to charge ratios may pass through to the detector.
The Varian was used to gather data on elemental concentrations in the teeth,
largely for the purpose of detecting diagenesis.
34
Figure 3.6.: Schematic diagram of a laser ablation cell connected to a
quadrupole ICP-MS (adapted from D. J. Sinclair).
The samples were analysed using two methods; ablating a series of spots across
the teeth, and ablating a single track across the tooth. All of the preliminary
work on the teeth (using the Neptune MC-ICP-MS for isotopic ratios rather
than elemental concentrations) was conducted using laser tracks; however,
there is some concern that the values may be affected by the tracking laser.
Four of the teeth were re-analysed using spots, which provide a more solid,
reliable signature, as well as allowing easier interpretation. These four teeth
were analysed on the Varian using spots in corresponding locations to the spots
made in the previous Neptune analysis. This approach is much more time
consuming, and laser tracks were sufficient for the Varian elemental
concentrations for our purposes. As such, the remaining 20 teeth, 12 adult and
8 juvenile, were analysed using tracks.
35
To remove any surface contamination received during the preparation process,
such as dust and fine particles deposited during the light sanding, the samples
were first subjected to a cleaning run using the laser, following the path set for
the analysis but for a shorter time and using a slightly larger spot size. For the
four teeth on which spots were used, the ablation time was 2 seconds using a
spot size of 63μm with no pre and post-ablation time. Pre- and post-ablation
times were set during the runs to measure background levels for comparison,
and to allow time for the lines to clear between analyses. This ensures that
there is no contamination between samples. This is unnecessary during the
cleaning run, as no data are recorded. For the teeth analysed using tracks, the
cleaning run used a spot size of 233μm, moved at a speed of 100μm per second,
and had no pre - and post-ablation times.
For the spot analyses, a spot size of 47μm was used, with an ablation time of
30 seconds and 50 seconds pre-ablation and 10 seconds post-ablation. For the
track analyses, the laser moved at a speed of 20μm per second, the pre-ablation
time was 50 seconds, the post-ablation time was 10 seconds, and a spot size of
47μm was used. All analyses began in the enamel and proceeded into the
dentine. Two standard glasses of known composition, NIST 610 and NISE 612,
were used, each being measured twice with spots before and after each tooth.
All analyses were conducted with the laser pulse rate set to 5Hz, and the
elements measured were 24
Mg, 25
Mg, 31
P, 43
Ca, 86
Sr, 88
Sr, 137
Ba, 138
Ba, 232
Th
and 238
U.
36
3.3.4. Neptune MC-ICP-MS - Isotopic composition
Finnigan MAT Neptune MC-ICP-MS operates on similar principals to the
Varian ICP-MS described above, although they use different methods to
separate and count the ions. The Neptune is a magnetic sector mass
spectrometer, which separates the ions by dispersing them in a magnetic field.
These are then doubly focussed and counted in a number of Faraday cups
(hence the title „multi-collector‟), each adjusted to collect a different ionic mass.
The Neptune was used to determine the strontium isotopic compositions of
both the soil and the teeth.
Figure 3.7.: Schematic diagram of a Finnigan MAT Neptune (from
http://www.dur.ac.uk/geochem.www/group/pimms.htm)
Analysis proceeded differently depending upon sample type. The teeth were
analysed using laser ablation, using the Neptune interfaced with the ANU
37
HelEx laser sampling system described previously (section 3.3.2.). Sixteen
adult teeth and eight juvenile teeth were analysed using a series of spots
proceeding from the enamel to the dentine in each tooth. The location for these
spots was determined by reviewing the Varian elemental concentration data in
an effort to choose the part of the tooth least affected by diagenesis. The four
adult teeth that were selected for bulk analysis in solution were analysed in the
same manner as the soil samples, with the solution being nebulised for
introduction to the plasma through an Apex desolvator.
For solution analysis, the Faraday cups were set to collect ions with masses of
82.4652, 83(Kr), 83.466, 84(Sr+Kr), 85(Rb), 86(Sr+Kr), 86.469, 87(Sr+Rb)
and 88(Sr). The half mass positions are set to monitor for the contribution of
doubly charged rare earth elements (REE‟s), and along with Kr and Rb these
are monitored and measured so that interference corrections can be applied.
During the analysis, a strontium isotope standard (SRM987) was measured
periodically to monitor the accuracy and precision of the measurements. To
facilitate further corrections, a blank (2% HNO3) was measured before each
sample, including the blanks created during the preparation process. A
sequence of acid and detergent rinses was used between each measurement to
ensure there was no contamination between samples during measurement.
As in analysis with the Varian, the samples for analysis using the laser were
subjected to a cleaning run to remove any surface contamination received
during the preparation process. To simplify interpretation of the isotopic
composition results when compared to the elemental concentrations, the spots
were set to overlay the large shallow tracks created during analysis using the
38
Varian. As mentioned previously, four of the teeth had already been subjected
to Neptune analysis using spots prior to elemental concentration analysis using
the Varian, and the results from this were evaluated alongside the newer data.
A spot size of 233μm was used for the cleaning run, and a spot size of 178μm
was used for the analysis. The step size between each spot (centre to centre)
was as close to 400μm could be achieved on each tooth, varying with the
length of the track from enamel to dentine and the number of spots that could
be accommodated fully within that track. For cleaning, each spot was ablated
for 2 seconds with no pre- and post-ablation times, and for analysis each spot
was analysed for 60 seconds with 50 seconds pre-ablation and 10 seconds post-
ablation. The laser pulse rate was set to 5Hz, and the Faraday cups were set to
collect 83
Kr, 167
Er++, 84
Sr, 85
Rb, 86
Sr, 173
Yb++, 87
Sr, 88
Sr, and 177
Hf++. A
tridacna shell was used as a standard for the Sr isotope ratios and measured 3
times before and after each set of samples.
39
Chapter 4
Results
______________________________________________________
4.1. Soil
4.1.1. The Médoc region
Results from the 11 soil samples collected from the region are presented in
Table 4.1 below, including voltages, 87
Sr/86
Sr ratios and errors for the samples
and standards (SRM987). The standards show good reproducibility and low
errors. Errors in the soil measurements, while higher, are still quite low. The
strontium isotope values have quite a large range, from 0.7092±0.0001 to
0.7231±0.00002, and there is clear separation in the values between the
different geologic units (see Figure 5.1.). This is true for all units other than the
Holocene sands, whose signatures presumably reflect the diverse sources from
which they originated before being washed into the peninsula.
40
Table 4.1.: 87
Sr/86
Sr ratios with voltages and errors for the samples
gathered during fieldwork. Includes standards (SRM987) measured
during the analyses.
Sample 88Sr
Volts
87Sr/
86Sr ±
87Sr/
86Sr
F11-188 3.669982 0.713918 0.000025
F11-189 6.814904 0.709784 0.000018
F11-190 3.774493 0.715560 0.000026
F11-191 5.308487 0.721426 0.000022
F11-192 3.250591 0.717748 0.000031
F11-193 4.229294 0.711634 0.000023
F11-194 1.632383 0.709178 0.000050
F11-195 5.014138 0.709420 0.000021
F11-196 5.084050 0.723147 0.000022
F11-197 13.684909 0.722062 0.000010
F11-198 4.588683 0.715563 0.000025
SRM987 #1 39.522276 0.710216 0.000006
SRM987 #2 39.185098 0.710217 0.000006
SRM987 #3 39.551973 0.710216 0.000006
4.1.2. Les Tumulus des Sables
The first seven soil samples that were analysed from the site showed
unexpected variability in the 87
Sr/86
Sr ratios, and there was some doubt as to
the validity of these initial results. The 88
Sr voltages, 87
Sr/86
Sr ratios and errors
for these samples and standards (SRM987) have been presented below in Table
4.2. Some concerns were raised about contamination during the preparation
process, and the Neptune analyses had to be conducted a number of times due
to errors and very low voltages in the earlier attempts. Some of better data
obtained still have reasonably low voltages (below 3.0), increasing the errors
and giving some reason for doubt as to their validity. Given the good
reproducibility and low errors of the SRM987 standards, there is little reason to
suspect analytical error. Note that no value was obtained for SLMEM 2901.
41
Table 4.2.: 87
Sr/86
Sr ratios for the first 7 soil samples including errors, and
standards (SRM987) measured intermittently during solution analyses.
Sample 88Sr
Volts
87Sr/
86Sr ±
87Sr/
86Sr
SLMEM 2901 0.000000 - -
SLMEM 2902 2.134248 0.712825 0.000046
SLMEM 2903 18.33808 0.710010 0.000010
SLMEM 2904 2.813816 0.720237 0.000034
SLMEM 2905 5.129897 0.717742 0.000022
SLMEM 2906 13.049800 0.713557 0.000012
SLMEM 2907 3.841983 0.710340 0.000031
SRM987 #1 28.694181 0.710239 0.000008
SRM987 #2 28.506605 0.710236 0.000007
SRM987 #3 27.793754 0.710237 0.000007
SRM987 #4 28.284651 0.710231 0.000008
The 11 newer samples, including samples taken from the same location as the
first seven, were subjected to column chemistry in a clean lab, while the first
samples were not. They yielded generally higher voltages and lower errors than
the first seven, and consistently uniform standard values with very low errors.
The voltages, 87Sr/86Sr ratios, errors of these samples and standards are
presented in Table 4.3. The standards also show good reproducibility and very
low errors. SLMEM 2902b, 2906b and 2907b agree reasonably well with the
results from the first set of samples and sample 2903b is outside error range but
still reasonably close, whereas samples 2904b and 2905b are significantly
different. Given the lower voltages, higher errors and concerns about
contamination in the first set of samples, the second set of results can be
considered more reliable and will be used preferentially. The isotope ratios of
the samples from the archaeological site range from 0.7097±0.00001 to
0.7188±0.00001. The lowest values occur within the burial and the highest
42
come from the external architecture, but there are no clear boundaries between
the two – the intermediate values come from a mixture of the locations. The
strontium isotope ratios from the site have quite a large range, but fit within the
range established for the Médoc region
Table 4.3.: 87
Sr/86
Sr ratios with voltages and errors for second batch of soil
samples from the site. Includes standards (SRM987) measured during the
analyses.
Sample 88Sr
Volts
87Sr/
86Sr ±
87Sr/
86Sr
SLMEM 2901b 8.733223 0.711492 0.000015
SLMEM 2902b 9.209545 0.712334 0.000014
SLMEM 2903b 10.329395 0.709676 0.000017
SLMEM 2904b 10.840188 0.716264 0.000013
SLMEM 2905b 9.113053 0.718785 0.000013
SLMEM 2906b 10.371188 0.713436 0.000014
SLMEM 2907b 17.671749 0.710145 0.000011
SLMEM 2908 13.812316 0.710084 0.000010
SLMEM 2909 6.902643 0.712592 0.000011
SLMEM 2910 9.147795 0.710763 0.000015
SLMEM 2911 12.308025 0.713385 0.000018
SRM987 #1 39.522276 0.710216 0.000006
SRM987 #2 39.185098 0.710217 0.000006
SRM987 #3 39.551973 0.710216 0.000006
4.2. Teeth
Due to the amount of data, only a few examples will be presented and
explained in detail. These have been selected to be as representative as possible;
however, it is important to note that each sample requires individual attention
in the interpretation of the results. These examples will be presented further in
section 4.2.3., after a brief overview of the results obtained using each
analytical method. The full data set is available in the appendices (Appendix 2).
43
4.2.1. Elemental concentrations (Varian)
There is significant variation both within and between the teeth, making
sweeping statements regarding diagenesis of the sample set unfeasible. The
concentrations of the elements of interest in detecting diagenesis, 238
U, 232
Th
and 88
Sr, have been graphed for each tooth and supplied in Appendix 2. Within
most teeth, the dentine and enamel can be divided into a number of zones, in
which diagenesis has been absent or present to varying degrees. Table 4.3
shows the average concentrations of U, Th and Sr in high and low zones in the
enamel and dentine of each tooth. Red indicates zones in which contamination
is likely, and blue indicates zones in which it is possible. Note that there are no
set cut off values, individual judgements must be made on the basis on
comparative concentrations within and between elements and samples. Note
also that the 88
Sr concentrations are typically not coloured, given the difficulty
in distinguishing diagenetic from biogenic strontium. Where significantly
heightened strontium concentrations correspond with high uranium and/or
thorium concentrations, these are coloured blue. Only one very extreme case
has been coloured red, indicating that it is likely the result of contamination
(J1). Where thorium is concerned, any occurrence that has been labelled blue is
possibly the result of background interference. Where the reading can be
confidently identified as genuine, no matter the magnitude of the value, red is
used.
Despite the variation between samples, there are a few overall trends that can
be noted.
44
In the majority of cases, the U and Sr are higher in the dentine than in
the enamel. In the case of the uranium, this is attributable to diagenesis.
The same cannot be assumed for strontium. While it is possible that the
raised concentrations may be in part due to the entry of diagenetic
strontium, there is no way to quantify how much (if any) of this is
diagenetic. Strontium concentrations tend to be higher in the dentine
than the enamel in modern teeth, and concentrations vary between
individuals.
A number of samples display a small spike in U and/or Th at the
beginning or the end of the track. This is likely due to the track
beginning or ending slightly over the edge of the cut surface, and the
reading is being affected by sediment residues at the occlusal surface or
pulp cavity.
In almost all cases, U and Th do not remain constant within the dentine
or the enamel. This is likely due to the presence of microscopic cracks
allowing easier passage for diagenetic material into the tooth (see also
Grün et al., 2008).
Very few of the teeth have entirely uncontaminated enamel, but pristine
zones are identified in most. The dentine is almost entirely
contaminated, although there are zones in some samples in which
diagenesis may have been minimal.
As a group, the juvenile teeth appear to be generally more contaminated
than the adult teeth, and tend to contain particularly large amounts of
Th.
45
46
4.2.2. Isotopic composition (Neptune)
4.2.2.1. Laser
The results provided by laser analysis showed a reasonably high degree of
variation. Table 4.5 gives the values for the enamel and dentine of each tooth.
These values were obtained by comparing the isotopic data to the elemental
concentrations data and locating the zones in which diagenesis appeared to be
absent. Averages were taken where there was more than one suitable zone, and
these usually had very similar values. No such pristine zones could be
identified in the dentine of any of the samples, and the values tend to be
reasonably homogenous. As such, averages are taken from the majority, if not
all, of the data from the dentine in most samples.
The dentine 87
Sr/86
Sr values range between 0.7106±0.0003 and 0.7134±0.0002,
which is largely within the expected range given the site location. The values in
the enamel range between 0.7133±0.0004 and 0.7244±0.0005, although the
lowest of these are taken from teeth in which no pristine zones could be
identified, and contain elevated U and/or Th concentrations. As such, some of
these values may be heavily influenced by diagenetic input. The juvenile teeth
(0.7146±0.0006 – 0.7230±0.0008) cannot be distinguished from the adult teeth
on the basis of the values, being dispersed throughout the adult range. They do
appear to have been more heavily influenced by diagenesis, but the effect that
this had on the Sr results is difficult to gauge.
The teeth show similar errors, which are somewhat higher than those obtained
during the standard measurements. A total of 154 standard measurements were
47
made throughout the analysis, with a minimum of three being performed at
each interval. As such, Table 4.6 (below) only shows averages taken from each
of these groups. The full list of standard measurements including 87
Sr/86
Sr
ratios and errors can be found in the appendices (Appendix 1). The standards
measured during the analysis of the four teeth also analysed using solution
have lower errors than the others, as do the laser analyses on these teeth. As
these laser analyses were performed at different times, this difference in errors
is attributable to differences in the setup, calibration and possibly condition of
the equipment. The difference in error magnitude is not so much as to cause
problems with the comparison and interpretation of the data.
48
Table 4.5.: 87
Sr/86
Sr ratios for the enamel and dentine of each tooth
(averages from appropriate locations), including errors. Red indicates a
signature that is likely heavily influenced by diagenesis, as indicated by U
and Th, and orange indicates a signature taken from zones with very high
Th content, but low U.
Tooth Enamel 87
Sr/86
Sr
2se Dentine 87
Sr/86
Sr
2se
A1 (SLMEM1007) 0.724369 0.000471 0.711349 0.000225
A2 (SLMEM466) 0.718634 0.000313 0.713176 0.000196
A3 (SLMEM308) 0.715640 0.000289 0.712493 0.000296
A4 (SLMEM263) 0.720533 0.000294 0.712481 0.000130
A5 (SLMEM861) 0.722658 0.000543 0.711701 0.000156
A6 (SLMEM112) 0.715797 0.000147 0.713439 0.000182
A7 (SLMEM491) 0.713302 0.000418 0.711423 0.000313
A8 (SLMEM1094) 0.715698 0.000384 0.710956 0.000255
A9 (SLMEM454) 0.722278 0.000677 0.713131 0.000309
A10 (SLMEM900) 0.717876 0.000442 0.712092 0.000305
A11 (SLMEM432) 0.715841 0.000535 0.710831 0.000314
A12 (SLMEM509) 0.719563 0.000749 0.711380 0.000321
A13 (SLMEM282) 0.716824 0.000586 0.712492 0.000335
A14 (SLMEM298) 0.716146 0.000426 0.711886 0.000315
A15 (SLMEM1157) 0.721258 0.000884 0.711865 0.000318
A16 (SLMEM5) 0.720057 0.000561 0.711821 0.000297
J1 (SLMEM1192) 0.719712 0.000666 0.711505 0.000351
J2 (SLMEM1251) 0.715088 0.000387 0.710640 0.000309
J3 (SLMEM276) 0.723010 0.000777 0.711027 0.000277
J4 (SLMEM66) 0.719776 0.000753 0.711141 0.000309
J5 (SLMEM102) 0.714607 0.000593 0.711664 0.000301
J6 (SLMEM119) 0.719197 0.000555 0.711825 0.000301
J7 (SLMEM86) 0.719931 0.000486 0.711542 0.000281
J8 (SLMEM 291) 0.718307 0.000488 0.711095 0.000289
49
Table 4.6.: Average 87
Sr/86
Sr values from standard measurements taken at
each interval (minimum of three in each group).
Number 87
Sr/86
Sr
Value
2se
Run 1 (1007 & 308) Before 0.709161 0.000169
Run 1 (1007 & 308) After 0.709175 0.000151
Run 2 (491 & 1094) Before 0.709196 0.000114
Run 2 (491 & 1094) After 0.709198 0.000124
Run 3 (454 & 900) Before 0.709164 0.000161
Run 3 (454 &900) After 0.709170 0.000175
Run 4 (432 – 5) Before 0.709166 0.000145
Between 509 & 282 0.709176 0.000147
Between 298 & 1157 0.709194 0.000157
Run 4 (432 – 5) After 0.709170 0.000192
Run 5 (Juvenile) Before 0.709146 0.000126
Between 1192 & 119 0.709188 0.000226
Between 66 & 276 0.709152 0.000210
Run 5 (Juvenile) After 0.709154 0.000141
Run 1b (112) Before 0.709213 0.000027
Run 1b (112) After 0.709209 0.000027
Run 2b (263) Before 0.709207 0.000025
Run 2b (263) After 0.709212 0.000028
Run 3b (466) Before 0.709210 0.000025
Run 4b (466) After 0.709203 0.000027
Run 5b (861) Before 0.709217 0.000027
Run 5b (861) After 0.709214 0.000029
Averages 0.709186 0.000112
4.2.2.2 Solution
Simonetti et al. (2008) observed a systematic offset between laser ablation and
solution results, in which laser ablations uniformly provided higher 87
Sr/86
Sr
values (on average by 0.0013±0.0006). This systematic offset was attributed to
the interference of 40
Ca-31
P-16
O molecules with 87
Sr. For this reason, four of
the teeth from our sample set were analysed using both laser ablation and
solution ICP-MS. The analyses by solution returned significantly different
50
results to the analyses by laser ablation. The solution results are presented in
Table 4.7. The offsets between the laser and solution results were not uniform,
ranging from 0.0012±0.0002 to 0.0089±0.0003, though most of the variation
occurred in the enamel. Three of the four dentine samples had quite similar
offsets, on the lower end of the range (0.0026±0.0002, 0.0026±0.0003 and
0.0028±0.0002) and the fourth provided the lowest offset of all
(0.0012±0.0002). It is worth noting that the voltages obtained in the enamel
were significantly lower than those in the dentine, casting some doubt upon
their accuracy and indicating that this may potentially be partially responsible
for the variation in the enamel offsets.
The solution samples had lower errors than the laser analyses, and uniformly
lower values. To determine whether the difference in values was due to the
method, which cannot avoid zones of diagenesis like laser ablation can, the
average of all values obtained using laser ablation was calculated for each
sample (see Table 4.8.). In most cases, the difference was minor. Note that no
value was obtained for SLMEM 861EN. No consistent offset was able to be
identified, so averages were taken from the enamel and the dentine offsets
between the solution and all laser values. These average offsets were subtracted
from the dental results provided by the laser (Table 4.9.). Despite the
difference in signatures, the solution samples also demonstrate a significant
difference between the dentine and the enamel suggesting that the phenomenon
is real regardless of the exact values (see Example 4 in section 4.2.3. below).
51
Table 4.7.: 87
Sr/86
Sr values for the teeth analysed by solution MC-ICP-MS
including errors and standards measured intermittently during solution
analysis.
Sample 88
Sr Volts 87
Sr/86
Sr ± 87
Sr/86
Sr
SLMEM 112DE 5.284534 0.710860 0.000019
SLMEM 112EN 1.723297 0.714010 0.000054
SLMEM 263DE 7.756951 0.709697 0.000026
SLMEM 263EN 3.571105 0.711647 0.000028
SLMEM 466DE 5.217999 0.710585 0.000019
SLMEM 466EN 1.714757 0.711915 0.000051
SLMEM 861DE 6.294880 0.710466 0.000020
SRM987 #1 3.710665 0.710187 0.000022
SRM987 #2 3.864663 0.710268 0.000024
SRM987 #3 3.945157 0.710280 0.000031
SRM987 #4 4.282606 0.710234 0.000023
SRM987 #5 3.638225 0.710202 0.000024
SRM987 #6 3.821130 0.710173 0.000025
Table 4.8.: 87
Sr/86
Sr values provided by solution, by laser analysis selecting
the appropriate zones, and by laser analysis using all values. The
differences between laser and solution, and laser (all values) and solution,
are provided for comparison
Sample Solution 87
Sr/86
Sr
Laser 87
Sr/86
Sr Laser (all)
Laser
- Solution
Laser
(all)
- Solution
112EN 0.71401 ±
0.00002
0.71580 ±
0.00015
0.71592 ±
0.00015 0.001787 0.001906
112DE 0.71086 ±
0.00005
0.71344 ±
0.00018
0.71344 ±
0.00018 0.002579 0.002579
263EN 0.71165 ±
0.00003
0.72053 ±
0.00029
0.72005 ±
0.00028 0.008886 0.008399
263DE 0.70970 ±
0.00003
0.71248 ±
0.00014
0.71248 ±
0.00014 0.002784 0.002784
466EN 0.71192 ±
0.00002
0.71863 ±
0.00031
0.71624 ±
0.00026 0.006719 0.004323
466DE 0.71059 ±
0.00005
0.71318 ±
0.00020
0.71318 ±
0.00020 0.002591 0.002590
861EN - 0.72266 ±
0.00054
0.72220 ±
0.00054 - -
861DE 0.71047 ±
0.00002
0.71170 ±
0.00016
0.71170 ±
0.00016 0.001235 0.001235
EN average & St.dev. 0.004867±0.00329
DE average & St.dev. 0.002275±0.00072
52
Table 4.9.: Laser 87
Sr/86
Sr values, with average offsets subtracted
Tooth Enamel Dentine
A1 (SLMEM1007) 0.719502 ± 0.003758 0.709074 ± 0.000943
A2 (SLMEM466) 0.713767 ± 0.0036 0.710901 ± 0.000914
A3 (SLMEM308) 0.710773 ± 0.003576 0.710218 ± 0.001014
A4 (SLMEM263) 0.715666 ± 0.003581 0.710206 ± 0.000848
A5 (SLMEM861) 0.717791 ± 0.00383 0.709426 ± 0.000874
A6 (SLMEM112) 0.710930 ± 0.003434 0.711164 ± 0.0009
A7 (SLMEM491) 0.708435 ± 0.003705 0.709148 ± 0.001031
A8 (SLMEM1094) 0.710831 ± 0.003671 0.708681 ± 0.000973
A9 (SLMEM454) 0.717411 ± 0.003964 0.710856 ± 0.001027
A10 (SLMEM900) 0.713009 ± 0.003729 0.709817 ± 0.001023
A11 (SLMEM432) 0.710974 ± 0.003822 0.708556 ± 0.001032
A12 (SLMEM509) 0.714696 ± 0.004036 0.709105 ± 0.001039
A13 (SLMEM282) 0.711957 ± 0.003873 0.710217 ± 0.001053
A14 (SLMEM298) 0.711279 ± 0.003713 0.709611 ± 0.001033
A15 (SLMEM1157) 0.716391 ± 0.004171 0.709590 ± 0.001036
A16 (SLMEM5) 0.715190 ± 0.003848 0.709546 ± 0.001015
J1 (SLMEM1192) 0.714845 ± 0.003953 0.709230 ± 0.001069
J2 (SLMEM1251) 0.710221 ± 0.003674 0.708365 ± 0.001027
J3 (SLMEM276) 0.718143 ± 0.004064 0.708752 ± 0.000995
J4 (SLMEM66) 0.714909 ± 0.00404 0.708866 ± 0.001027
J5 (SLMEM102) 0.709740 ± 0.00388 0.709389 ± 0.001019
J6 (SLMEM119) 0.714330 ± 0.003842 0.709550 ± 0.001019
J7 (SLMEM86) 0.715064 ± 0.003773 0.709267 ± 0.000999
J8 (SLMEM 291) 0.713440 ± 0.003775 0.708820 ± 0.001007
53
4.2.3. Examples
Example 1 – Adult 1 (SLMEM 1007)
Two tracks were made across the tooth, beginning at each of the cusps. The
first appeared to have been less affected by diagenesis and had a larger enamel
surface for analysis, so was chosen for the Neptune isotopic analysis. The
uranium content in the enamel is quite low, although zones of lower (0.04ppm)
and higher (0.123ppm) content are able to be distinguished. The content in the
higher zone is still quite low and in other circumstances it may be interpreted
differently; however, in this tooth there is a noticeable peak in the strontium
concentration where the uranium peaks, suggesting that this added strontium is
diagenetic. To be certain that the isotopic signature is pristine, it was safest to
take the value from the lower zone. The uranium content rises sharply at the
dentine-enamel junction (DEJ), jumping to an average of 12.373 within a short
distance. The uranium remains quite high for about 3mm through the dentine,
before gradually dropping back down to sub-ppm concentrations. A number of
other samples demonstrate this sharp rise at the DEJ, with the highest uranium
values in the dentine domain closest to the DEJ. In conjunction with the greater
susceptibility of dentine to diagenesis, the slight cracks at the DEJ between the
enamel and dentine likely allow diagenetic material to penetrate the tooth. The
strontium also rises sharply at the DEJ, but it doesn‟t mimic the uranium and
does not drop down further into the dentine. It was theorised that the part of the
dentine in which the uranium is lowest may preserve an unaltered strontium
signature, but comparison of the concentration data with the isotopic data
revealed this not to be the case. Across all samples, isotope ratios in the dentine
54
show clear overprint and generally remain relatively constant regardless of
large fluctuations in uranium and thorium content.
A1 - SLMEM 1007
Figure 4.1.: Graphs of the elemental concentrations and isotopic
composition, along with an image of the tooth. (Note that the laser track
made during the Varian analysis underlies the spots made for the Neptune
analysis. A track from previous analysis is also visible)
0.01
0.1
1
10
100
1000
567 617 667 717 767
pp
m
Time (sec)
Sr
Th
U
0.708
0.712
0.716
0.72
0.724
0.728
1 2 3 4 5 6 7 8 9 10 11 12 13
87 S
r/8
6 Sr
Spot Number
55
Example 2 – Juvenile 1 (SLMEM1192)
While this tooth is quite an extreme example, a number of the other teeth
exhibit similar traits to varying degrees. The concentrations of all three
elements display very dramatic spatial variation in this tooth. The uranium
concentrations never drop below 1.5ppm, higher than some other teeth ever
reach, and climb as high as 38ppm. Thorium is constantly present, the likes of
which is only seen in one other tooth, A7. Concentrations exceed 35ppm in
places, and average in the dentine is slightly under 10ppm – concentrations one
might expect to find in soil. The strontium concentrations are at their lowest at
95 ppm, consistent with what might be found in unaltered human enamel.
These low points only occur briefly, however, and concentrations reach as high
as 500ppm, far beyond anything seen in any other samples. Given that a
cleaning run was conducted with the laser prior to analysis, this is unlikely to
be surface contamination. The chemical and physical contamination in this
tooth are extensive, and there don‟t appear to be any zones in which the
original strontium might have been preserved.
Many of the samples display a clear rise in concentration at the DEJ in at least
one element, demonstrating the increased susceptibility of dentine to diagenesis.
This is not the case in this tooth, and on the basis of the elemental
concentrations alone one might expect that the entire tooth has undergone
significant diagenetic overprint. Interestingly, when the isotopic compositions
are considered, this does not appear to be the case. As was seen in the last
example, the isotopic ratio remained relatively constant in the dentine despite
the fluctuation in elemental concentrations. The same is true for this tooth,
56
displaying no apparent correlation between isotopic ratios and elemental
concentrations in the dentine. This suggests that the dentine has been
completely overprinted, which is supported by the isotopic signature which
matches what we expect for area in which the burial is located. Surprisingly,
despite the very high concentrations of all elements in the enamel, with a very
large amount of spatial variation, the enamel signature has not been overprinted.
This is evidenced by the very high values obtained for the enamel, which far
exceed the local range. Unfortunately, while it is apparent that the signature has
not been entirely overprinted, we cannot be sure that a smaller degree of
diagenetic alteration has not taken place, and so cannot ascertain the biogenic
strontium signature.
57
J1 – SLMEM 1192
Figure 4.2.: Graphs of the elemental concentrations and isotopic
composition, along with an image of the tooth showing the spots made for
Neptune analysis (overlaying the Varian laser track)
0.01
0.1
1
10
100
1000
1882 1912 1942 1972 2002
pp
m
Time (sec)
Sr
Th
U
0.71
0.712
0.714
0.716
0.718
0.72
0.722
1 2 3 4 5 6 7
87 S
r/8
6 Sr
Spot Number
58
Example 3 – Adult 7 (SLMEM 491)
This tooth is unusual in that it is the only tooth with an enamel value that falls
within the range of the dentine values for the teeth. This could have a number
of explanations. The tooth may have been so affected by diagenesis that the
enamel was also overprinted with the dentine, however, even with the
enormous levels of contamination apparent in the previous example, the
enamel retained a significantly higher signature. It is also possible that the
original enamel value was quite low and was only affected to the same extent
as other teeth, or not at all. The dentine is still lower, at the lower end of the
dentine range, but this is likely overprint and the original signature may well
have matched the enamel.
Thorium is present across the entirety of the tooth, although uranium levels are
still reasonably low in most places. The DEJ is not able to be seen in any of the
elements, and there is no clear difference between the dentine and the enamel
in the strontium concentrations. This may suggest that significant diagenetic
strontium has indeed entered the tooth, as most teeth do show a noticeable
jump in Sr concentration after the DEJ. This supports the proposition that the
enamel signature may have been altered quite significantly from its original
value.
59
A7 – SLMEM 491
Figure 4.3.: Graphs of the elemental concentrations and isotopic
composition, along with an image of the tooth showing the spots made for
Neptune analysis (overlaying the Varian laser track)
0.01
0.1
1
10
100
1000
2739 2789 2839 2889 2939 2989 3039
pp
m
Time (sec)
Sr
Th
U
0.711
0.7115
0.712
0.7125
0.713
0.7135
0.714
1 6 11 16
87 S
r/8
6Sr
Spot Number
60
Example 4 – Adult 6 (SLMEM112)
This tooth is one of the four analysed previously using spots, and so was
analysed on the Varian using spots in corresponding locations. These four teeth
were also the ones analysed using solution. Like many other samples, there is a
clear rise in uranium at the DEJ. Like the previous sample, though, there is no
clear difference in strontium concentrations between the dentine and the
enamel. There are slight thorium spikes throughout the sample, but these are
generally small and isolated and it is likely that many of them are erroneous. It
is quite interesting in this sample to note the apparent correlation between the
quantity of uranium in the sample and the strontium isotopic signature. Where
the uranium is higher, the signature is lower (see figure 4.4.). This suggests that
in this tooth at least, the amount of diagenetic strontium entering the tooth was
proportional to the amount of uranium. This is not generally the case, however,
and there is no linear relationship between uranium content and diagenetic
strontium content - the extent of strontium signature modification cannot be
assessed on the basis of uranium content.
The solution analyses returned quite different values to the laser analyses, as
was seen in all teeth on which solution analysis was conducted. The difference
between the dentine signatures was twice that of the enamel, although this is
not standard for all teeth. The variation is quite considerable between samples,
and no standard offset is able to be observed between the laser and solution
analysis methods. While no standard offset is able to be identified, all solution
samples demonstrate a significant difference in values between the enamel and
the dentine. This tooth shows a difference of approximately 0.003 between the
61
enamel and dentine using both sampling methods. This confirms that the
difference is certainly real, even if the values themselves are inaccurate.
A6 – SLMEM 112
Figure 4.4.: Graphs of the elemental concentrations and isotopic
composition, along with an image of the tooth. (Note that the laser track
made during the Varian analysis is not visible, but it underlies the spots
made for the Neptune analysis. A track from previous analysis is also
visible)
0.01
0.1
1
10
100
1000
558 758 958 1158 1358 1558 1758
pp
m
Time (sec)
Sr
Th
0.71
0.711
0.712
0.713
0.714
0.715
0.716
0.717
1 3 5 7 9 11 13 15
laser
62
Chapter 5
Discussion
5.1. Soil analyses
As mentioned in the previous chapter, the first seven soil samples were
reproduced with a second set of samples taken from the same location. Only
six of the original seven returned results, and these had higher errors and lower
voltages than their newer counterparts. This is mostly likely due to errors in the
preparation and analysis, and along with the concerns about contamination
rising from the fact that the first seven samples were not subjected to the
column chemistry in a clean lab like the others, results from the original seven
samples are not considered to be as reliable. As such, the 11 newer results have
been used preferentially and they, along with 11 samples taken from the Médoc
region during fieldwork, form the basis for the discussions below.
5.1.1. The Médoc region
The geologic mapping of the region (Bureau de recherches géologiques et
minières, 2005) was based upon formation age rather than lithology, so each
unit may be composed of a number of rock types. For example, the Eocene unit
(orange in figures 1.3., 3.2., and 5.1.) is composed of marl, clay, limestone,
sandstone, and conglomerates. Thus, it is impractical to attempt to estimate the
expected Sr signature of each region based upon typical isotope ratios for the
rock types. Fortunately, as mentioned in the results section, the samples from
different units group together quite well and show clear separation in their
ranges. The exceptions to this are the lower Pleistocene and Holocene units
63
(light and dark green) that follow the coasts, which are likely formed by the
transportation and deposition of sediment by the Atlantic Ocean and the
Gironde rather than the weathering of local bedrock. The lower Pleistocene
unit (light green) fits within the range of the Pliocene and lower Pleistocene
pink unit which covers the majority of the peninsula. The Holocene (dark
green) unit has variable signatures, presumably reflecting the locations from
which the sediment originated. The Pliocene and lower Pleistocene sediment
(pink unit) that covers most of the inland area in the Médoc has a much higher
isotope ratio than the Eocene and Oligocene (orange and yellow) bedrock units,
reflecting the signatures of the source material from higher altitudes (Pyrenees).
Figure 5.1.: Measured 87
Sr/86
Sr ranges for each geologic unit in the Médoc
peninsula and the site of Le Tumulus des Sables. Note that the green units
have patchier distributions.
64
5.1.2. Le Tumulus des Sables
The soil samples from Le Tumulus des Sables display significantly more
variation than one may expect from sediment taken from the same location. In
addition to the difference in sediment colour at the site when compared to the
rest of the region, as noted in Chapter 1 (1.3.1.), this suggests the presence of
factors influencing the composition of the sediment other than those usually
involved (as in Section 2.2.3.). The site is situated within the Oligocene unit
(yellow), although, given the comparatively small size of the Médoc region, it
is not far from each of the others - particularly the Pliocene and lower
Pleistocene unit which covers much of the region (pink). Given the clear
separation in values from the different geologic units (other than the coastal
Holocene sands), one may expect the site of Le Tumulus des Sables to have a
signature similar to the Oligocene (yellow) unit. In part it does; however, its
range is much broader (while still fitting within the total range for the region).
This unexpectedly high degree of variation is difficult to explain. The
depositional setting is certainly quite complex, involving the input of sediment
washed down from higher areas (such as the Massif Central and the Pyrenees)
as well as tidal deposition. The samples taken from other locations, however,
grouped according to their geologic unit quite well. It is unlikely that this
complex deposition could have resulted in such an array of values in such a
confined location. It is more likely to have been caused by factors specific to
the burial itself. As mentioned in Section 1.3.1, the excavators theorised that
the brownish soil was the result of acid released by the limestone occurring at
the site (Courtaud et al., 2010). Similarly, it is possible that the degree of
65
variation within the site is the result of decomposition of buried archaeological
material. Whatever the source of this variation, it makes the local signature
quite difficult to define. Given that the overprinted values in the dentine
generally reflect the local value for the Oligocene unit in which the site is
located (see below), this may indicate that the site originally displayed a typical
signature for this area. This cannot be conclusively proven, but it is worth
consideration when interpreting the results from the teeth.
5.2. Teeth analyses
5.2.1. Laser vs. solution
The average offset between laser ablation and solution results identified by
Simonetti et al. (2008) was 0.0013±0.0006. While two of our solution samples,
112EN and 861DE, had offsets within this range, all others were significantly
higher. The offsets also displayed more variation than one might expect,
ranging from 0.0012±0.0002 to 0.0089±0.0003. While neither the enamel nor
the dentine was consistently higher than the other, patterns were able to be
identified in the offsets – the dentine offsets were much more consistent,
whereas most of the variation in values occurred in the enamel. The
significantly lower voltages in the enamel may be partially responsible for the
degree of variation in the offsets; however, there are a number of other
potential contributing factors.
The laser ablation was conducted using a series of spots, and the sample for
solution was taken from a different part of the dentine/enamel. As
demonstrated in both the elemental concentrations and strontium isotopic
66
analyses, both the enamel and dentine are heterogeneous in their composition.
Variation in the quantities of 87
Sr and 40
Ca-31
P-16
O molecules throughout the
tooth may affect the isotopic ratio (Simonetti et al., 2008). It is possible that the
differences in the offsets are at least partly an artefact of this heterogeneity.
Similarly, variation in the extent of diagenesis throughout the tooth, as
identified in the Varian elemental analysis, may be partially responsible for the
variation in the offsets. The laser spots can avoid zones of increased diagenesis,
whether intentionally or unintentionally, where the bulk sampling used for
solution analysis does not. The spots are also much less likely to be
representative of the entire tooth composition than the bulk sampling. In order
to assess whether the difference in the offsets is due to variation in the
elemental composition and diagenetic alteration within the tooth, micro-drilling
for the solution sample in the exact location of the laser analysis may be useful.
Despite the problem that the offset between laser ablation and solution presents,
and the difficulties in identifying and confirming these offsets in this study, this
does not necessarily cause significant problems for the interpretation of the
results. In fact, uncertainty over the exact signature is probably of less
importance in this study than in most others. Because the regional isotope
mapping revealed such a large range in Sr signatures, the capacity for the
identification of migration in the sample set is diminished to the point where
the exact Sr signatures are of little importance. The most important
observations in this case are the difference between the enamel and dentine in
the samples, and the fact that the dentine isotopic signatures all fall within a
comparatively small range. From this we have been able to determine that the
67
dentine has been subjected to significant diagenetic overprint and that the
original signature in many of the teeth was quite different, suggesting non-
locality. Due to the large regional range, it is impossible to tell whether this
„non-locality‟ represents true migration or small scale mobility. Only the
existence of a significant difference between the enamel and dentine is
important in this case, and the solution results support this. For example, in
tooth A6 (SLMEM112) (as in section 4.2.3.), the difference between the
enamel and dentine is roughly 0.003 in both sampling methods. After the
subtraction of the average laser offset from each sample (see table 4.8.), the
average difference between the enamel and dentine in all samples is 0.0043,
though it ranges from 0.0002 to 0.0104. This is significantly lower than the
unadjusted laser values, providing an average difference between enamel and
dentine of 0.0068, and ranging from 0.0019 to 0.0130.
5.2.2. Locals or non-locals?
The primary aim of this study has been to determine whether the individuals
from the study site are of local or non-local origin. In the preliminary work
conducted on this site, the local signature could not be determined and so the
only recourse was to compare the Sr results of the enamel to the dentine.
Given the significant difference that was observed between the dentine and the
enamel in all teeth, indicating diagenetic overprint in the dentine, it was
theorised that the whole population may have been non-local in origin. This
study attempted to create more reliable results, in conjunction with the creation
of a regional isotope map. As such, both the difference between the enamel and
dentine and the comparison of the dental values to the regional isotopic map
68
are available as methods of origin determination. The 87
Sr/86
Sr values were
adjusted using the average solution/laser offsets. While these are the more
realistic results, the errors are very large and the interpretation of the data
becomes complicated.
5.2.2.1. Enamel vs. Dentine
In interpreting the enamel and dentine results, careful attention must be paid to
the individual circumstances of each. While there is no linear correlation
between uranium concentration and diagenetic strontium uptake, 87
Sr/86
Sr
values appear largely to reflect the changes in uranium concentration. Where
the uranium concentrations are higher, the strontium isotope ratios are
generally lower, indicating the diagenetic impact of the local soil. While the
87Sr/
86Sr values have only been taken from the most appropriate domains in the
enamel, it is not necessarily the case that this represents a pristine zone in each
of the teeth. The enamel values tend to be lowest where either there is no clear
DEJ in the strontium concentrations, or where the concentrations fluctuate
significantly within the enamel. The correlation between these raised or
abnormal strontium concentrations in the enamel as compared to the dentine
and the lower enamel values seems to indicate that diagenetic strontium uptake
has occurred in these domains.
In the dentine, overprint appears to be universal. Fluctuations in uranium
within the tooth do not, other than in one or two samples, appear to be reflected
in the isotopic values. It is interesting to note, however, that while these
fluctuations within the tooth seem to have little impact on the signature, the
69
overall concentration of uranium compared to the other teeth does seem to bear
some relation to the Sr signature. Generally, where the uranium concentrations
are lower overall, the dentine Sr signature is higher. This supports the notion
that the low dentine values reflect extensive overprint, indicating that some
teeth have been less affected than others. Despite this variation in the extent of
overprint, there can be little doubt that all dentine has been affected quite
significantly, and it is unlikely that any of the dentine values reflect the
biogenic strontium signature. The fact that all of these samples in such a
comparatively young site show such extensive overprint, even where uranium
concentrations in the dentine are low, only serves to reinforce the notion that
dentine (and presumably bone) are poor materials for Sr isotope analysis.
The unadjusted laser data shows the dentine range falling entirely below all but
one enamel sample. The offset-adjusted data are significantly different, and
show no separation in the ranges. The dentine signatures range from 0.7084 ±
0.00103 – 0.7112 ± 0.0009. Nine of the offset-adjusted enamel signatures fall
immediately within this range, and when errors are considered this number
increases to 20. While there is little significant distinction between the overall
dentine and enamel ranges, most individual samples show a significant
distinction between the enamel and the dentine (with the exception of
SLMEM308, 491, and 102). With the consideration of the large errors,
however, the number of teeth in which there is actually a clear distinction
between the enamel and dentine falls to 11, and those in which the minimum
difference is larger than 0.0010 falls to 7. At this stage of the examination, it
appears likely that at least nine of the individuals are non-local. Within errors
70
ranges, is possible that all individuals are non-locals; however, the errors are so
large that it is impossible to make any firm conclusions.
5.2.2.2. Dental results in the regional context
As mentioned previously, the soil samples taken from the site itself display a
much higher range that expected, and may have been affected by factors
specific to the depositional circumstances. In this case, these cannot be used for
the determination of the local Sr isotope range. For this, we must turn to the
soil mapping conducted in the Médoc region. The offset-adjusted dentine Sr
signatures range from 0.7084 ± 0.0010 – 0.7112 ± 0.0009. With errors
considered, these values fall within and below the low end of the range for the
region, largely within the range identified for the Eocene (orange) unit. Given
the location of the site, situated with the Oligocene unit and in close proximity
to the Eocene unit, this is not unexpected. It is likely that the low local
signature is due to the input of marl, which forms a component of both of the
Oligocene and Eocene units. The higher values of the Pliocene/lower
Pleistocene (pink) sedimentary unit, located within very close proximity of Le
Tumulus des Sables, appear not to have had any impact on the local signature.
71
Figure 5.2.: Measured 87
Sr/86
Sr ratios for each geologic unit in the Médoc
peninsula and the offset adjusted enamel and dentine ranges (errors
included)
As well as the local range, the regional range must also be considered in order
to determine whether the individuals are truly foreign to the area. As discussed
in section 5.1, the different geologic units in the region have distinct ranges,
with the exclusion of the recent Holocene coastal deposition (see Figure 5.1.).
Unfortunately, the range in the Médoc is quite large, with lower values
exhibited in the older bedrock regions and much higher values being displayed
in the Pliocene/lower Pleistocene sediment (pink) which covers much of the
Médoc region. A number of the offset-adjusted enamel signatures (errors
included) possibly fall within the range of the Pliocene/lower Pleistocene unit;
however, none, except Adult 1 (SLMEM1007) with a signature of
0.7195±0.0038, could possibly reach above it. This means that despite the
differences between the enamel and dentine, and in many cases the enamel and
72
range at the site, no conclusion can be reached on the origin of these individual
using strontium isotopes. Under these circumstances, there is no way to
differentiate a migrant from hundreds of kilometres away from someone who
grew up two kilometres from Le Tumulus des Sables. Presuming the
individuals are migrants, a number of potential areas of origin can be ruled out
on the basis of general knowledge of the geology and previous mapping work
in France (Grün, pers. comm., Kelly, 2007). The enamel Sr values are
generally lower than the Pliocene/lower Pleistocene sedimentary unit, which
comprises much of the area within and immediately to the south of the Médoc,
including the Aquitaine basin. This sediment has its origins in the Pyrenees,
which has similarly has high Sr signatures, as do other highland areas in France
(such as the Massif Central). If these areas can be excluded, and the individuals
were indeed migrants, the most likely area of origin is directly to the east of the
Médoc.
While the Sr values may not be able to tell us whether the individuals are
migrants or not, they do indicate a certain degree of mobility within the Médoc
region at the very least. The geologic unit in which the site is located is quite
small (no more than 2x5km) and the site itself is right on the border of this unit
with the next, meaning that individuals need only travel a few kilometres to
obtain a non-local signature. The fact that there is so much variation in the
enamel signature, however, indicates that the population movement is far more
complex. All signatures could have come from the Médoc region, but they
reflect locations all over the region. Some of the difference in signatures may
be attributable to mixing of food sources from various regions, but one would
73
expect that within the same family or small community that people would
largely be eating similar foods from similar sources, and would thus obtain
similar signatures. The significant variation in signatures between the
individuals indicates considerable regional mobility at the very least.
Figure 5.3.: Geological map of France around the Médoc. The most likely
origin for any migrants would be to the east of the Médoc, before reaching
the Massif Central. The Pyrenees and Aquitaine basin to the south are
unlikely points of origin (from Bureau de recherches géologiques et
minières, 2005, GoogleEarth, 2011)
Given the impossibility of sex determination of the individuals due to the
disarticulated state of the remains, it is difficult to tell from this work whether
74
the variation in signatures was due to the movements of small groups and
individuals, or the result of marriage partner exchange. Presuming that the
values obtained from the juvenile enamel can be trusted to some extent, despite
the higher degree of contamination, these may provide more of a clue as to the
nature of population movement. If the variation was due to the exchange of
marriage partners, one would expect that the juveniles, all growing up in the
same community, would display similar signatures. The process of adjusting
for the offset increased the errors massively, meaning that all juvenile teeth are
now within range of one another; however, four of the teeth are particularly
similar in Sr values (averaging around 0.7148 ± 0.004.). In unadjusted laser
values, these four are also very similar. One tooth came close, although not
within error range of the first four, and the other three provided much higher
and lower values. This indicates that these juveniles spent the initial periods of
their lives in different locations to the others, and migrated later on. This
certainly does not rule out some of the variation in signatures coming from
marriage exchange partners, but it does indicate that this is not the sole source
of the variation. The presence of these children with different signatures
indicates the movement of family groups.
5.2.2.3. Further investigation
There is a large amount of variation in the both the enamel and dentine
strontium values within the group, and this was examined in terms of the
placement of each sample in the burial. This was done in an attempt to
determine whether there were any patterns in enamel signature and burial
location, and whether there was any correlation between burial location and the
75
diagenetic overprint. The site was excavated in grid squares using spits (R
values) rather than by context, although a number of different contexts were
able to be indentified (C values). The soil and dental samples were examined
by each of these unit types, where such information was provided by the site
excavators. Unfortunately, none of these groupings (grid squares, depths (R) or
context (C)) allowed the identification of any correlation between location and
strontium values in the soil, enamel or dentine.
The enamel Sr values were also considered in light of dental morphology.
During sample preparation, it was noted that a number of the teeth appear to be
taurodont, a dental condition characterised by an enlarged pulp chamber, an
elongated body relative to the roots, and a lack of or reduced constriction at the
cementoenamel junction (Ackerman et al., 1973, Jafarzadeh et al., 2008,
Jaspers and Witkop Jr, 1980, Keeler, 1973, Manjunatha and Kovvuru, 2010,
Shaw, 1928). While a number of the teeth appear to display the characteristic
to varying degrees, only five of them can be identified comfortably.
Taurodonty is caused by the failure of Hertwig‟s epithelial sheath diaphragm to
invaginate at the proper level (Ackerman et al., 1973, Jafarzadeh et al., 2008,
Manjunatha and Kovvuru, 2010). While it has been associated with a number
of syndromes and abnormalities, largely genetic and developmental, it occurs
most frequently in the absence of disease and appears to be a heritable trait
(Jafarzadeh et al., 2008, Jaspers and Witkop Jr, 1980, Manjunatha and Kovvuru,
2010). It is generally considered to be quite a rare trait, although prevalence
differs between populations from as little as 0.3% of the population to as much
as 48% (Jafarzadeh et al., 2008, and sources therein). It should be noted that
76
some of this variation may be attributed to different diagnostic criteria, but the
variation between study populations is certainly significant.
Taurodontism is only occasionally observed in the incisors and has a very low
incidence in deciduous dentition (Jafarzadeh et al., 2008), so the juvenile
samples have not been included as part of the sample for the investigation of
the trait in this population. Of the 15 teeth in which at least half of the roots and
pulp chamber remains attached to the crown, five of these are identified as
taurodont (SLMEM 1157, 454, 432, 112 and 900). A population frequency of
1/3rd
is very high, and given the heritability of the trait it was presumed that
these individuals represented a family group. Upon consideration of the
strontium isotope results in these teeth, this was found not to be the case; two
individuals have reasonably high signatures, two have reasonably low
signatures within, and one is in between. The unadjusted laser values, with
much lower errors, indicated that the three signature groups were statistically
different. With the offset correction, however, all of the values fall within error
range of one another. Unfortunately, with the current data, there is no way to
tell whether the differences in the values are real or not. If the individuals do
represent a family, this would lend support to the idea of migratory family
groups as is possibly indicated by the juvenile teeth. If the signatures are
different, it may still be possible that the individuals comprised a migratory
family group of different ages, having spent their childhoods in different
locations. The other interpretation is that these individuals do not represent a
family group at all. It may be that this population displays the trait in high
frequency. It may also be the case that this high percentage is simply an
77
artefact of the small sample size. In order to confirm that the reliability of this
result, morphological analysis on a much larger sample would be necessary.
Of course, any observations about trait frequency and mobility within this
population rest upon the assumption that the individuals from the burial do in
fact represent a single population. As noted in the first chapter, the site was
identified as Bell Beaker based upon the presence of distinctive bell Beaker
artefacts. Dating of one bone fragment provided a date which confirmed
occupation of the site during the Bell Beaker era, but charcoal dates from the
upper and lower layers of the excavation provided much older and younger
dates, suggesting site occupation over a much broader period of time. The age
range and poor stratigraphy of the site prevent the secure identification of a
sample as belonging to the correct time period without individual dating. Given
the propensity for Bell Beaker people in this region to re-use tombs of the
preceding cultures, and the variable ways in which these tombs were used (as
discussed in section 2.1.1), the most that can be said at this point is that Bell
Beaker associated artefacts have been identified at the site and that at least one
individual has been dated to this period of time.
5.2.3. Implications for the technique
As observed by Simonetti et al. (2008), significant offsets were identified
between the laser ablation and solution methods of analysis. The offsets were
reasonably large and quite variable, particularly in the enamel. The correction
of the laser results by averaging these offsets created very large errors, and
rendered the results almost unusable. Much more investigation into the cause
78
of the magnitude and variability of the offset needs to be conducted if the laser
ablation technique is to be applied in further Sr isotope studies.
Another existing concern that was addressed was the effect of diagenesis on
dentine and enamel. Even in such comparatively young samples, the overprint
in the dentine was found to be extensive. While concentrations of Sr, U and Th
may be used to indicate the presence of diagenesis, no consistent correlation
was able to be found between elevated levels of these contaminants and Sr
isotopic signature in the dentine. Even where levels of contaminants might
have been considered to indicate minimal contamination in the enamel, the
dentine was found to be entirely overprinted (for example, A1 – SLMEM1007).
In the enamel, the level of diagenetic alteration was considerably lower, and
pristine zones were identified in most. Some relation between elevated levels
of U, Th and the isotopic signature was able to be identified, with the isotopic
values usually dropping noticeably in zones where these were elevated,
although there is no constant or linear correlation. Where raised Sr levels
occurred at the same time as high U levels, isotopic ratios dropped significantly,
and this was found to be a good indicator of contamination. These results
suggest that even where concentrations of the elemental contaminants are low,
dentine is highly unlikely to preserve any pristine zones.
While the investigation of the concerns discussed above may have their place
in the continuing improvement of our understanding and utilisation of the
technique, perhaps the most significant contributions made by this study arise
from the local and regional mapping. As discussed previously, the soil samples
from the archaeological site display much more variation in values than might
79
have been expected, and this is likely at least partially attributable to factors
specific to archaeological contexts such as the decomposition of buried
material. This, in conjunction with the agreement between the dentine values
and the expected local range based upon regional mapping, suggests that the
sediment from an archaeological site should not be considered to be
representative of the local range. The regional mapping itself turned out to
have more of an impact on the interpretation of the results than was foreseen.
The preliminary results, based upon the difference between the enamel and
dentine, seemed to suggest that the population was largely composed of
migrants. Upon consideration of the map, this conclusion was invalidated
completely. The value of regional mapping, which is largely underused in
strontium isotope studies, could not have been better demonstrated.
5.2.4. Implications for the Bell Beaker
Before any discussion of potential implications for our understanding of the
Bell Beaker phenomenon, it is necessary to emphasise that we do not know
with certainty that the individuals from the site truly represent a single, Bell
Beaker, population. Given that no groups or trends are able to be identified in
the enamel strontium values within the group, it seems possible at least that this
is a single, highly mobile population. Whether this mobility is simply within
the local region or over a larger area is impossible to tell at this point. The
variation in enamel signatures suggests a number of source locations for the
individuals, possibly also indicating that the group is not in fact part of a single
population. For the time being, the results are being treated as if representative
of a single Bell Beaker population; however, all discussion about the potential
80
implications for the Bell Beaker phenomenon should be read with this
uncertainty about the sample composition in mind.
Due to impossibility of distinguishing small scale local mobility from large
scale migration in this study, no grand conclusions can be drawn regarding the
origins of this population or the role of migration in the spread of the Bell
Beaker culture. However, this does not mean that the results have no use. The
difference between enamel and dentine strontium values along with the
significant variation between the enamel values suggests a high degree of
mobility within the population with individuals coming from a number of
source locations. We may not be able to identify how far away these source
locations may have been, but there is little doubt that the people were highly
mobile within the region at the very least. As mentioned previously, the
inability to determine the sex of each individual makes it difficult to determine
the degree to which the variation in the signatures is attributable to the
exchange of marriage partners. The variation in juvenile signatures may,
however, be indicative of the movement of family groups. The movement of
family groups rather than individual marriage exchange partners is certainly
what one might expect to see if migration were the driving factor behind the
spread of the Bell Beaker culture. One should also consider that even if the
enamel signatures were only obtained from the local region, this does not rule
out migratory origins for the Bell Beaker culture. There is no reason to assume
that a burial of Bell beaker individuals must necessarily represent the first
generation of migrants into the area. It is possible, even, that the large amount
of variation in the enamel signatures is partially attributable to the varying
81
origins of different generations. Again, the broad range of signatures obtainable
from the local region alone make this impossible to ascertain.
Presuming that the individuals at Le Tumulus des Sables were of migrant
origin, the most likely origin (as established in Section 5.2.2.2) for these people
would be the area directly to the east of the Médoc. It is unlikely that they
came from the south, anywhere between the Pyrenees and the Médoc, although
extremely distant origins on the other side of the Pyrenees cannot be excluded.
It seems unlikely, however, that any of these individuals had direct origins in
the Iberian Peninsula. This does not necessarily pose a problem for the
hypothesis that the Bell Beaker Phenomenon had its origins in the Iberian
Peninsula; it simply indicates that this population certainly is not a first
generation wave of settlers originating in the Pyrenees.
While results do not firmly indicate whether the Bell Beaker phenomenon was
the result of migration or cultural diffusion, the answer need not necessarily be
just one or the other. One theory proposed by Vander Linden (2007b) suggests
that the Bell Beaker phenomenon neither represented the simple diffusion of
objects and ideas, nor a single group of people with territorial unity. Instead, he
proposed that the Bell Beaker culture was composed of a series of discrete
groups, in which the constant flow of people, ideas and technologies produced
a chain of networks which led to the witnessed global effect. This was
suggested to have been the result of generalised exchange in marriage partners,
rather than reciprocity. Again, the inability to determine the sex of the
individuals means that investigation of marriage partner exchange is not
possible; however, the indication from the juvenile remains of the movement of
82
family groups would seem to suggest that more was going on than the
exchange of marriage partners. The mechanism may not be strongly supported
by our data, but the concept may well be. There is good evidence for high
regional mobility at the very least. Based upon our data, diffusion as the
mechanism for the spread of the Bell Beaker culture is least supported, but is
not directly contraindicated.
The possible identification of a high frequency of taurodontism in the sample
set may also have implications for our understanding of the Bell Beaker, but
morphological analysis of a much larger Bell Beaker sample set would be
required to verify its existence. If the individuals displaying taurodonty
represent a family group, the variation in strontium isotope ratios may
represent migration across generations. If these individuals are not a family
group, the high prevalence of taurodonty within the population that this would
indicate may be used to indicate the origins of the individual - the trait is
usually quite rare, although the frequency has been seen to vary between „racial‟
groups (Jafarzadeh et al., 2008, and sources therein). Detailed consideration of
this is beyond the scope of this study, but may be worth future investigation.
5.3. Summary
The different geologic units in the Médoc region separate well
according to Sr values, with the exception of the Holocene sediment.
The soil samples from Le Tumulus des Sables display unexpected
variation, likely due to the complex depositional geology and
83
decomposition of buried material. This archaeological soil does not
provide a reliable local range.
Significant offsets between laser ablation and solution are identified.
The dentine offsets are more constant than the enamel offsets, with vary
considerably. There are a number of potential factors contributing to
this variation.
The offset corrections applied to the original laser ablation results
lower them, reduce the difference between the enamel and dentine, and
create massive error ranges. Despite this, most teeth still show a clear
difference between enamel and dentine.
All dentine shows extensive overprint, despite the comparatively young
age of the samples. Sr values were only taken from appropriate domains
in the enamel, and not all samples preserved pristine zones.
In the context of the mapping of the Médoc region, and due to the
massive errors introduced by the offset corrections, it is impossible to
tell from the dental Sr results whether the individuals are migrants or
local
Despite our inability to determine geographic origins, the variability in
enamel values suggests that the population is highly mobile.
Examination of the juvenile teeth may suggest the movement of small
family groups. If they were migrants, they are most likely to have come
from the East of the Médoc. Origins in the South seem highly unlikely.
84
Chapter 6
Conclusions
______________________________________________________
6.1. Conclusions and recommendations
Significant difficulties were encountered in answering the main aim of the
study, but all aims were addressed to the fullest extent allowed by the data and
this led to a number of conclusions. The results from this study ultimately
turned out to be inconclusive due to a number of factors, but this does not mean
that migration cannot be distinguished at the site. The biggest source of error
was the laser ablation/solution offset and this has to be resolved before any
further work can be conducted at this site or elsewhere using laser ablation. It
is suggested that until the cause of the offset has been fully investigated and a
solution identified, that laser only be used to determine elemental
concentrations and identify pristine domains within the tooth. It is
recommended that micro drilling is used to extract samples for solution
analyses from these pristine zones, given that the current bulk sampling method
does not avoid diagenetic material.
With more accurate and precise results, more could be said about the mobility
of the individuals. Whether they were true migrants, however, or simply
mobile within the Médoc would still be impossible to distinguish due to the
large range of Sr signatures within the Médoc. Other isotopic proxies, such as
oxygen and lead, may be used to trace migration. These work in slightly
different ways, meaning that they may not be affected by the same obstacles as
the strontium work in this region. Together, these isotopic proxies may not
85
only distinguish locals from non-locals, but with extensive mapping it may be
possible even to determine the origins of any migrants.
While it was not possible to distinguish migrants from locals, it is possible to
identify mobility within the Médoc region at the very least. Whether this is true
group mobility or the exchange of marriage partners is difficult to tell. Sex
determination on the basis of physical anthropology is impossible given the
fragmentation of the human remains, but there are other options. DNA could be
used, depending on the preservation of the material. Detailed studies would not
be required; a look at the karyotype is all that is necessary to determine the
presence or absence of a „y‟ chromosome. Given that taurodonty is sometimes
associated with genetic abnormalities, such as Kleinfelter‟s syndrome, in which
the male has an extra „x‟ chromosome (xxy), it may also be interesting to
investigate whether this is the case in any of the taurodont individuals.
The results of this study have a number of implications not only for the site
itself, but for the technique in general. The state of diagenesis in the dentition
in even a comparatively young site such as this suggests that dentine, and
perhaps bone by association, should only be used for comparison with the
enamel and possibly for confirmation of the local signature. Future studies in
the area, and perhaps in general, should focus on tooth enamel to gather the
most reliable results. It is recommended that elemental concentrations are
examined and compared to the isotopic data in order to determine the most
pristine zones. One or the other is insufficient for the firm identification of
contaminated Sr signatures.
86
In this case, the level of contamination in the dentine made it quite useful in
determining and confirming the local signature. The overprint was lower than
might have been expected for the Oligocene unit, in which the site was located;
however, the geologic maps reflect chronology rather than lithology. The low
Sr signature likely came from rock types which were a component in both the
Oligocene and Eocene units. Interestingly, the local signature, as determined
by this mapping and by the overprinted dentine, was nothing like the soil
samples taken from the site itself. The unexpected variation in the soil samples
from the site is likely to have been caused by the complex depositional setting,
as well as the effect of decomposing material within the burial. This
phenomenon is likely not restricted to this site, and may be applicable
elsewhere. The implication of this is that archaeological soil should not be
considered to reflect the local range. This should be taken into account in
future studies, and the local signature should be determined through other
means, such as more extensive mapping or through the analysis of teeth from
small mammals with confined ranges.
The importance of mapping could not have been better demonstrated than in
this study. Without the mapping of the Médoc, many of the individuals would
have been identified as migrants on the basis of the clear difference in Sr
signatures between the enamel and the dentine. Had the local signature been
determined on the basis of the enamel of small mammalian remains, many of
the individuals would still likely have been outside this range and would have
been firmly identified as non-local. It is only with mapping of the Médoc
region that the magnitude of the regional Sr range was discovered, it was
87
realised that the individuals were not necessarily migrants. It is recommended
that all future studies incorporate mapping of the region around the site at the
very least. More detailed mapping across larger areas may provide further
valuable insights, but basic mapping of the surrounding area in consultation
with a geologic map is the minimum required to ensure that migration is not
falsely identified.
The inability to distinguish true migration from outside the Médoc from
mobility within the region has hampered attempts at expanding our
understanding of the Bell Beaker, but this is just one site of many across
Europe. Particularly in light of the observed differences between the eastern
and western domains of the Bell Beaker people, it is recommended that
mobility studies using Sr isotopes, and other isotopic proxies where necessary,
are extended to many other sites. With the inclusion of isotope mapping,
perhaps then it may be possible to determine the origin and nature of the Bell
Beaker phenomenon once and for all.
88
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composition of modern and Holocene mollusc shells as a palaeosalinity
indicator. Chemical Geology, 232, 54-66.
98
Appendix 1
Full list of the standard (Tridacna shell) measurements taken throughout
the Neptune laser analyses
Batch Number 87
Sr/86
Sr 2se
1.1 1007 & 308 Before 0.709155 0.000138
1.1 1007 & 308 Before 0.709166 0.000190
1.1 1007 & 308 Before 0.709161 0.000179
1.1 1007 & 308 After 0.709180 0.000139
1.1 1007 & 308 After 0.709164 0.000144
1.1 1007 & 308 After 0.709182 0.000169
1.1 Average 0.709168 0.000159
1.2 491 & 1094 Before 0.709192 0.000114
1.2 491 & 1094 Before 0.709189 0.000124
1.2 491 & 1094 Before 0.709206 0.000104
1.2 491 & 1094 After 0.709205 0.000122
1.2 491 & 1094 After 0.709188 0.000121
1.2 491 & 1094 After 0.709201 0.000130
1.2 Average 0.709197 0.000119
1.3 454 & 900 Before 0.709154 0.000150
1.3 454 & 900 Before 0.709181 0.000178
1.3 454 & 900 Before 0.709157 0.000156
1.3 454 &900 After 0.709175 0.000225
1.3 454 &900 After 0.709177 0.000148
1.3 454 &900 After 0.709159 0.000152
1.3 Average 0.709167 0.000168
1.4 432 - 5 Before 0.709184 0.000155
1.4 432 - 5 Before 0.709154 0.000153
1.4 432 - 5 Before 0.709161 0.000128
1.4 Between 509 & 282 0.709178 0.000149
1.4 Between 509 & 282 0.709171 0.000130
1.4 Between 509 & 282 0.709178 0.000163
1.4 Between 298 & 1157 0.709202 0.000157
1.4 Between 298 & 1157 0.709199 0.000162
1.4 Between 298 & 1157 0.709181 0.000152
1.4 432 - 5 After 0.709172 0.000197
1.4 432 - 5 After 0.709172 0.000180
1.4 432 - 5 After 0.709167 0.000200
1.4 Average 0.709176 0.000160
1.5 Juvenile Before 0.709136 0.000159
1.5 Juvenile Before 0.709158 0.000113
1.5 Juvenile Before 0.709144 0.000106
1.5 Between 1192 & 119 0.709203 0.000235
99
1.5 Between 1192 & 119 0.709193 0.000226
1.5 Between 1192 & 119 0.709167 0.000218
1.5 Between 66 & 276 0.709190 0.000147
1.5 Between 66 & 276 0.709153 0.000160
1.5 Between 66 & 276 0.709113 0.000323
1.5 Juvenile After 0.709158 0.000122
1.5 Juvenile After 0.709175 0.000143
1.5 Juvenile After 0.709129 0.000158
1.5 Average 0.709159 0.0001758
2.1 112 Before 0.709211 0.000025
2.1 112 Before 0.709221 0.000031
2.1 112 Before 0.709229 0.000025
2.1 112 Before 0.709216 0.000026
2.1 112 Before 0.709219 0.000027
2.1 112 Before 0.70922 0.000028
2.1 112 Before 0.70923 0.000032
2.1 112 Before 0.709201 0.000023
2.1 112 Before 0.709194 0.000028
2.1 112 Before 0.709203 0.000030
2.1 112 Before 0.709195 0.000022
2.1 112 Before 0.709213 0.000023
2.1 112 Before 0.709222 0.000031
2.1 112 After 0.709211 0.000028
2.1 112 After 0.70922 0.000029
2.1 112 After 0.709217 0.000027
2.1 112 After 0.70922 0.000028
2.1 112 After 0.709214 0.000024
2.1 112 After 0.709215 0.000026
2.1 112 After 0.709202 0.000028
2.1 112 After 0.709179 0.000027
2.1 112 After 0.709218 0.000020
2.1 112 After 0.709196 0.000026
2.1 112 After 0.709215 0.000023
2.1 112 After 0.709211 0.000030
2.1 112 After 0.709199 0.000029
2.1 Average 0.709211 0.000026
2.2 263 Before 0.709201 0.000024
2.2 263 Before 0.709215 0.000025
2.2 263 Before 0.709230 0.000025
2.2 263 Before 0.709199 0.000030
2.2 263 Before 0.709207 0.000027
2.2 263 Before 0.709194 0.00004
2.2 263 Before 0.709192 0.000026
2.2 263 Before 0.709213 0.000023
2.2 263 Before 0.709209 0.000024
2.2 263 After 0.709190 0.000026
100
2.2 263 After 0.709224 0.000028
2.2 263 After 0.709226 0.000033
2.2 263 After 0.709214 0.000029
2.2 263 After 0.709198 0.000030
2.2 263 After 0.709219 0.000025
2.2 263 After 0.709208 0.000029
2.2 263 After 0.709219 0.000026
2.2 Average 0.709209 0.000027
2.3 466 Before 0.709203 0.000020
2.3 466 Before 0.709219 0.000028
2.3 466 Before 0.709218 0.000029
2.3 466 Before 0.709201 0.000025
2.3 466 Before 0.709196 0.000026
2.3 466 Before 0.709205 0.000025
2.3 466 Before 0.709212 0.000027
2.3 466 Before 0.709217 0.000026
2.3 466 Before 0.709215 0.000025
2.3 466 Before 0.709185 0.000026
2.3 466 Before 0.709219 0.000023
2.3 466 Before 0.709209 0.000025
2.3 466 Before 0.709225 0.000024
2.3 466 After 0.709199 0.000027
2.3 466 After 0.709214 0.000029
2.3 466 After 0.709205 0.000027
2.3 466 After 0.709193 0.000026
2.3 466 After 0.709192 0.000025
2.3 466 After 0.709221 0.000030
2.3 466 After 0.709204 0.000026
2.3 466 After 0.709211 0.000026
2.3 466 After 0.709211 0.000031
2.3 466 After 0.709202 0.000026
2.3 466 After 0.709177 0.000023
2.3 466 After 0.709205 0.000027
2.3 Average 0.709206 0.000026
2.4 861 Before 0.709216 0.000034
2.4 861 Before 0.709203 0.000025
2.4 861 Before 0.709215 0.000032
2.4 861 Before 0.709246 0.000023
2.4 861 Before 0.70922 0.000026
2.4 861 Before 0.709217 0.000024
2.4 861 Before 0.709229 0.000026
2.4 861 Before 0.70921 0.000028
2.4 861 Before 0.709219 0.000024
2.4 861 Before 0.709229 0.000023
2.4 861 Before 0.709216 0.000031
2.4 861 Before 0.709196 0.000026
101
2.4 861 Before 0.70922 0.000027
2.4 861 Before 0.709211 0.000030
2.4 861 Before 0.709216 0.000028
2.4 861 Before 0.709199 0.000026
2.4 861 Before 0.709227 0.000030
2.4 861 Before 0.709217 0.000024
2.4 861 Before 0.70922 0.000007
2.4 861 Before 0.709214 0.000026
2.4 861 After 0.70922 0.000033
2.4 861 After 0.709232 0.000028
2.4 861 After 0.709235 0.000029
2.4 861 After 0.7092 0.000029
2.4 861 After 0.709223 0.000028
2.4 861 After 0.709216 0.000029
2.4 861 After 0.709224 0.000027
2.4 861 After 0.709221 0.000026
2.4 861 After 0.70923 0.000030
2.4 861 After 0.709222 0.000027
2.4 861 After 0.709209 0.000027
2.4 861 After 0.7092 0.000030
2.4 861 After 0.709207 0.000030
2.4 861 After 0.709205 0.000021
2.4 861 After 0.709202 0.000029
2.4 861 After 0.70919 0.000030
2.4 861 After 0.709206 0.000030
2.4 861 After 0.709226 0.000030
2.4 861 After 0.709209 0.000027
2.4 861 After 0.709216 0.000030
2.4 861 After 0.709199 0.000026
2.4 861 After 0.709228 0.000033
2.4 861 After 0.709209 0.000030
2.4 Average 0.709215 0.000027
102
Appendix 2
Complete illustrated data sheets for each tooth
______________________________________________________
103
Adult 1 - SLMEM 1007
Elemental Concentrations
Isotopic Composition
0.01
0.1
1
10
100
1000
567 617 667 717 767
pp
m
Time (sec)
Sr
Th
U
0.708
0.712
0.716
0.72
0.724
0.728
1 2 3 4 5 6 7 8 9 10 11 12 13
87 S
r/8
6 Sr
Spot Number
Average 87
Sr/86
Sr ratios *
Enamel Dentine 87
Sr/86
Sr 2se 87
Sr/86
Sr 2se
0.724369 0.000471 0.711349 0.000225
*From selected zones, avoiding areas affected
by diagenesis areas where possible
Elemental Concentrations – High and low zones 238
U Concentration (ppm) 232
Th Concentration (ppm) 88
Sr Concentration (ppm)
EN
High
EN
Low
DE
High
DE
Low
EN
High
EN
Low
DE
High
DE
Low
EN High EN Low DE
High
DE
Low
0.123 0.040 10.081 0.293 0.000 0.000 0.000 0.000 48.544 39.727 156.636 142.933
104
Adult 2 – SLMEM 466
Elemental Concentrations
Isotopic Composition
0.01
0.1
1
10
100
1000
1 101 201 301 401 501 601 701
pp
m
cycle
Sr
Th
U
0.71
0.712
0.714
0.716
0.718
0.72
1 3 5 7 9 11 13
87
Sr/8
6Sr
Spot number
Average 87
Sr/86
Sr ratios
Enamel Dentine 87
Sr/86
Sr 2se 87
Sr/86
Sr 2se
Laser* 0.718634 0.000313 0.713176 0.000196
Solution 0.711915 0.000051 0.710585 0.000019
*From selected zones, avoiding areas
affected by diagenesis areas where
possible
Elemental Concentrations – High and low zones 238
U Concentration (ppm) 232
Th Concentration (ppm) 88
Sr Concentration (ppm)
EN
High
EN
Low
DE
High
DE
Low
EN
High
EN
Low
DE
High
DE
Low
EN High EN
Low
DE
High
DE Low
0.052 0.000 0.267 0.144 0.001 0.000 0.000 0.000 79.456 56.928 111.648 101.8566
105
Adult 3 - SLMEM 308
Elemental Concentrations
Isotopic Composition
0.01
0.1
1
10
100
1000
1617 1667 1717 1767 1817
pp
m
Time (sec)
Sr
Th
U
0.711
0.712
0.713
0.714
0.715
0.716
0.717
1 3 5 7 9 11 13
87 S
r/8
6Sr
Spot Number
Average 87
Sr/86
Sr ratios *
Enamel Dentine 87
Sr/86
Sr 2se 87
Sr/86
Sr 2se
0.715640 0.000289 0.712493 0.000296
*From selected zones, avoiding areas
affected by diagenesis areas where possible
Elemental Concentrations – High and low zones
238U Concentration (ppm)
232Th Concentration (ppm)
88Sr Concentration (ppm)
EN
High
EN
Low
DE
High
DE
Low
EN
High
EN
Low
DE
High
DE
Low
EN High EN Low DE
High
DE
Low
0.464 0.000 4.593 0.071 0.043 0.000 0.000 0.000 93.601 76.647 105.460 100.169
106
Adult 4 – SLMEM 263
Elemental Concentrations
Isotopic Composition
0.708
0.71
0.712
0.714
0.716
0.718
0.72
0.722
1 3 5 7 9 11 13 15
87
Sr/8
6Sr
Spot Number
Average 87
Sr/86
Sr ratios
Enamel Dentine 87
Sr/86
Sr 2se 87
Sr/86
Sr 2se
Laser* 0.720533 0.000294 0.712481 0.00013
Solution 0.711647 0.000028 0.709697 0.000026
*From selected zones, avoiding areas
affected by diagenesis areas where
possible
Elemental Concentrations – High and low zones 238
U Concentration (ppm) 232
Th Concentration (ppm) 88
Sr Concentration (ppm)
EN
High
EN
Low
DE
High
DE
Low
EN
High
EN
Low
DE
High
DE
Low
EN High EN Low DE
High
DE
Low
0.177 0.046 0.242 0.209 0.000 0.000 0.000 0.000 48.445 45.582 129.241 129.734
107
Adult 5 – SLMEM 861
Elemental Concentrations
Isotopic Composition
0.01
0.1
1
10
100
1000
525 725 925 1125 1325 1525 1725
pp
m
Time (sec)
Sr
Th
U
0.708
0.71
0.712
0.714
0.716
0.718
0.72
0.722
0.724
1 3 5 7 9 11 13 15
87
Sr/8
6Sr
Spot number
Average 87
Sr/86
Sr ratios
Enamel Dentine 87
Sr/86
Sr 2se 87
Sr/86
Sr 2se
Laser* 0.722658 0.000543 0.711701 0.000156
Solution - - 0.710466 0.000020
*From selected zones, avoiding areas
affected by diagenesis areas where
possible
Elemental Concentrations – High and low zones 238
U Concentration (ppm) 232
Th Concentration (ppm) 88
Sr Concentration (ppm)
EN
High
EN
Low
DE
High
DE
Low
EN
High
EN
Low
DE
High
DE
Low
EN High EN Low DE
High
DE
Low
0.017 0.000 3.044 2.347 0.000 0.000 0.020 0.000 51.145 41.541 176.905 164.910
108
Adult 6 – SLMEM 112
Elemental Concentrations
Isotopic Composition
0.01
0.1
1
10
100
1000
558 758 958 1158 1358 1558 1758
pp
m
Time (sec)
Sr
Th
U
0.71
0.711
0.712
0.713
0.714
0.715
0.716
0.717
1 3 5 7 9 11 13 15
87
Sr/8
6Sr
Spot number
Average 87
Sr/86
Sr ratios
Enamel Dentine 87
Sr/86
Sr 2se 87
Sr/86
Sr 2se
Laser* 0.715797 0.000147 0.713439 0.000182
Solution 0.714101 0.000054 0.710860 0.000019
*From selected zones, avoiding areas
affected by diagenesis areas where
possible
Elemental Concentrations – High and low zones 238
U Concentration (ppm) 232
Th Concentration (ppm) 88
Sr Concentration (ppm)
EN
High
EN
Low
DE
High
DE
Low
EN
High
EN
Low
DE
High
DE
Low
EN High EN Low DE
High
DE
Low
0.002 0.000 1.222 0.313 0.000 0.000 0.000 0.001 140.742 115.855 126.531 113.048
109
Adult 7 – SLMEM 491
Elemental Concentrations
Isotopic Composition
0.01
0.1
1
10
100
1000
2739 2789 2839 2889 2939 2989 3039
pp
m
Time (sec)
Sr
Th
U
0.711
0.7115
0.712
0.7125
0.713
0.7135
0.714
1 3 5 7 9 11 13 15 17
87 S
r/8
6 Sr
Spot Number
Average 87
Sr/86
Sr ratios *
Enamel Dentine 87
Sr/86
Sr 2se 87
Sr/86
Sr 2se
0.713302 0.000418 0.711423 0.000313
*From selected zones, avoiding areas
affected by diagenesis areas where possible
Elemental Concentrations – High and low zones 238
U Concentration (ppm) 232
Th Concentration (ppm) 88
Sr Concentration (ppm)
EN
High
EN
Low
DE
High
DE
Low
EN
High
EN
Low
DE
High
DE
Low
EN High EN Low DE
High
DE
Low
0.109 0.027 2.178 0.373 0.053 0.000 0.048 0.045 158.058 124.530 146.815 138.116
110
Adult 8 – SLMEM 1094
Elemental Concentrations
Isotopic Composition
0.01
0.1
1
10
100
1000
539 589 639 689 739 789
pp
m
Time (sec)
Sr
Th
U
0.71
0.711
0.712
0.713
0.714
0.715
0.716
0.717
1 3 5 7 9 11 13
87 S
r/8
6 Sr
Spot Number
Average 87
Sr/86
Sr ratios *
Enamel Dentine 87
Sr/86
Sr 2se 87
Sr/86
Sr 2se
0.715698 0.000384 0.710956 0.000255
*From selected zones, avoiding areas
affected by diagenesis areas where possible
Elemental Concentrations – High and low zones
238U Concentration (ppm)
232Th Concentration (ppm)
88Sr Concentration (ppm)
EN
High
EN
Low
DE
High
DE
Low
EN
High
EN
Low
DE
High
DE
Low
EN High EN Low DE
High
DE
Low
0.072 0.000 9.870 7.962 0.000 0.000 0.013 0.010 152.039 89.234 234.123 214.377
111
Adult 9 – SLMEM 454
Elemental Concentrations
Isotopic Composition
0.01
0.1
1
10
100
1000
1367 1417 1467 1517
pp
m
Time (sec)
Sr
Th
U
0.712
0.714
0.716
0.718
0.72
0.722
0.724
1 3 5 7 9 11
87 S
r/8
6 Sr
Spot Number
Average 87
Sr/86
Sr ratios *
Enamel Dentine 87
Sr/86
Sr 2se 87
Sr/86
Sr 2se
0.722278 0.000677 0.713131 0.000309
*From selected zones, avoiding areas
affected by diagenesis areas where possible
Elemental Concentrations – High and low zones 238
U Concentration (ppm) 232
Th Concentration (ppm) 88
Sr Concentration (ppm)
EN
High
EN
Low
DE
High
DE
Low
EN
High
EN
Low
DE
High
DE
Low
EN High EN Low DE
High
DE
Low
0.002 0.000 1.644 0.610 0.002 0.000 0.000 0.000 48.153 37.060 96.490 96.189
112
Adult 10 – SLMEM 900
Elemental Concentrations
Isotopic Composition
0.01
0.1
1
10
100
1000
2499 2549 2599 2649 2699 2749
pp
m
Time (sec)
Sr
Th
U
0.711
0.712
0.713
0.714
0.715
0.716
0.717
0.718
0.719
1 3 5 7 9 11
87Sr
/86 S
r
Spot Number
Average 87
Sr/86
Sr ratios *
Enamel Dentine 87
Sr/86
Sr 2se 87
Sr/86
Sr 2se
0.717876 0.000442 0.712092 0.000305
*From selected zones, avoiding areas
affected by diagenesis areas where possible
Elemental Concentrations – High and low zones 238
U Concentration (ppm) 232
Th Concentration (ppm) 88
Sr Concentration (ppm)
EN
High
EN
Low
DE
High
DE
Low
EN
High
EN
Low
DE
High
DE
Low
EN High EN Low DE
High
DE
Low
0.324 0.003 0.858 0.242 0.001 0.000 0.000 0.000 61.407 50.445 108.170 96.817
113
Adult 11 – SLMEM 432
Elemental Concentrations
Isotopic Composition
0.01
0.1
1
10
100
1000
486 536 586 636 686
pp
m
Time (sec)
Sr
Th
U
0.71
0.711
0.712
0.713
0.714
0.715
0.716
0.717
1 3 5 7 9 11
87 S
r/8
6 Sr
Spot Number
Average 87
Sr/86
Sr ratios *
Enamel Dentine 87
Sr/86
Sr 2se 87
Sr/86
Sr 2se
0.715841 0.000535 0.710831 0.000314
*From selected zones, avoiding areas
affected by diagenesis areas where possible
Elemental Concentrations – High and low zones 238
U Concentration (ppm) 232
Th Concentration (ppm) 88
Sr Concentration (ppm)
EN
High
EN
Low
DE
High
DE
Low
EN
High
EN
Low
DE
High
DE
Low
EN High EN Low DE
High
DE
Low
0.317 0.027 3.245 - 0.004 0.002 0.000 - 51.732 49.830 123.165 -
114
Adult 12 – SLMEM 509
Elemental Concentrations
Isotopic Composition
0.01
0.1
1
10
100
1000
1239 1289 1339 1389 1439 1489 1539
pp
m
Time (sec)
Sr
Th
U
0.71
0.712
0.714
0.716
0.718
0.72
1 3 5 7 9 11 13 15 17
87 S
r/8
6 Sr
Spot Number
Average 87
Sr/86
Sr ratios *
Enamel Dentine 87
Sr/86
Sr 2se 87
Sr/86
Sr 2se
0.719563 0.000749 0.711380 0.000321
*From selected zones, avoiding areas
affected by diagenesis areas where possible
Elemental Concentrations – High and low zones 238
U Concentration (ppm) 232
Th Concentration (ppm) 88
Sr Concentration (ppm)
EN
High
EN
Low
DE
High
DE
Low
EN
High
EN
Low
DE
High
DE
Low
EN High EN Low DE
High
DE
Low
0.053 0.008 2.277 1.121 0.000 0.000 0.001 0.000 62.118 44.797 121.283 109.944
115
Adult 13 – SLMEM 282
Elemental Concentrations
Isotopic Composition
0.01
0.1
1
10
100
1000
2499 2549 2599 2649 2699 2749
pp
m
Time (sec)
Sr
Th
U
0.711
0.712
0.713
0.714
0.715
0.716
0.717
0.718
1 3 5 7 9 11 13 15
87 S
r/8
6 Sr
Spot Number
Average 87
Sr/86
Sr ratios *
Enamel Dentine 87
Sr/86
Sr 2se 87
Sr/86
Sr 2se
0.716824 0.000586 0.712492 0.000335
*From selected zones, avoiding areas
affected by diagenesis areas where possible
Elemental Concentrations – High and low zones 238
U Concentration (ppm) 232
Th Concentration (ppm) 88
Sr Concentration (ppm)
EN
High
EN
Low
DE
High
DE
Low
EN
High
EN
Low
DE
High
DE
Low
EN High EN Low DE
High
DE
Low
0.104 0.012 9.681 0.362 0.000 0.000 0.000 0.000 83.294 68.825 92.923 85.472
116
Adult 14 – SLMEM 298
Elemental Concentrations
Isotopic Composition
0.01
0.1
1
10
100
1000
974 1074 1174 1274 1374
pp
m
Time (sec)
Sr
Th
U
0.71
0.711
0.712
0.713
0.714
0.715
0.716
0.717
1 6 11 16 21
87Sr
/86 S
r
Spot Number
Average 87
Sr/86
Sr ratios *
Enamel Dentine 87
Sr/86
Sr 2se 87
Sr/86
Sr 2se
0.716146 0.000426 0.711886 0.000315
*From selected zones, avoiding areas
affected by diagenesis areas where possible
Elemental Concentrations – High and low zones 238
U Concentration (ppm) 232
Th Concentration (ppm) 88
Sr Concentration (ppm)
EN
High
EN
Low
DE
High
DE
Low
EN
High
EN
Low
DE
High
DE
Low
EN High EN Low DE
High
DE
Low
0.011 0.001 1.453 0.272 0.004 0.001 0.006 0.002 59.970 58.974 112.829 105.660
117
Adult 15 – SLMEM 1157
Elemental Concentrations
Isotopic Composition
0.01
0.1
1
10
100
1000
1974 2024 2074 2124 2174
pp
m
Time (sec)
Sr
Th
U
0.71
0.712
0.714
0.716
0.718
0.72
0.722
0.724
1 2 3 4 5 6 7 8 9 10
87 S
r/8
6 Sr
Spot Number
Average 87
Sr/86
Sr ratios *
Enamel Dentine 87
Sr/86
Sr 2se 87
Sr/86
Sr 2se
0.721258 0.000884 0.711865 0.000318
*From selected zones, avoiding areas
affected by diagenesis areas where possible
Elemental Concentrations – High and low zones 238
U Concentration (ppm) 232
Th Concentration (ppm) 88
Sr Concentration (ppm)
EN
High
EN
Low
DE
High
DE
Low
EN
High
EN
Low
DE
High
DE
Low
EN High EN Low DE
High
DE
Low
0.064 0.001 1.646 0.124 0.005 0.000 0.004 0.001 46.007 29.045 110.112 95.969
118
Adult 16 – SLMEM 5
Elemental Concentrations
Isotopic Composition
0.01
0.1
1
10
100
1000
2729 2779 2829 2879 2929
pp
m
Time (sec)
Sr
Th
U
0.71
0.712
0.714
0.716
0.718
0.72
0.722
1 3 5 7 9 11
87 S
r/8
6 Sr
Spot Number
Average 87
Sr/86
Sr ratios *
Enamel Dentine 87
Sr/86
Sr 2se 87
Sr/86
Sr 2se
0.720057 0.000561 0.711821 0.000297
*From selected zones, avoiding areas
affected by diagenesis areas where possible
Elemental Concentrations – High and low zones 238
U Concentration (ppm) 232
Th Concentration (ppm) 88
Sr Concentration (ppm)
EN
High
EN
Low
DE
High
DE
Low
EN
High
EN
Low
DE
High
DE
Low
EN High EN Low DE
High
DE
Low
- 0.001 2.500 0.127 - 0.001 0.002 0.002 - 53.523 126.699 108.654
119
Juvenile 1 – SLMEM 1192
Elemental Concentrations
Isotopic Composition
0.01
0.1
1
10
100
1000
1882 1902 1922 1942 1962 1982 2002
pp
m
Time (sec)
Sr
Th
U
0.71
0.712
0.714
0.716
0.718
0.72
0.722
1 2 3 4 5 6 7
87 S
r/8
6 Sr
Spot Number
Average 87
Sr/86
Sr ratios *
Enamel Dentine 87
Sr/86
Sr 2se 87
Sr/86
Sr 2se
0.719712 0.000666 0.711505 0.000351
*From selected zones, avoiding areas
affected by diagenesis areas where possible
Elemental Concentrations – High and low zones 238
U Concentration (ppm) 232
Th Concentration (ppm) 88
Sr Concentration (ppm)
EN
High
EN
Low
DE
High
DE
Low
EN
High
EN
Low
DE
High
DE
Low
EN High EN Low DE
High
DE
Low
18.543 4.386 7.159 5.625 1.192 0.032 8.011 0.030 179.852 136.615 391.951 125.713
120
Juvenile 2 – SLMEM 1251
Elemental Concentrations
Isotopic Composition
0.01
0.1
1
10
100
1000
2568 2588 2608 2628 2648
pp
m
Time (sec)
Sr
Th
U
0.71
0.711
0.712
0.713
0.714
0.715
0.716
1 2 3 4 5 6
87 S
r/8
6 Sr
Spot Number
Average 87
Sr/86
Sr ratios *
Enamel Dentine 87
Sr/86
Sr 2se 87
Sr/86
Sr 2se
0.715088 0.000387 0.710640 0.000309
*From selected zones, avoiding areas
affected by diagenesis areas where possible
Elemental Concentrations – High and low zones 238
U Concentration (ppm) 232
Th Concentration (ppm) 88
Sr Concentration (ppm)
EN
High
EN
Low
DE
High
DE
Low
EN
High
EN
Low
DE
High
DE
Low
EN High EN Low DE
High
DE
Low
0.496 0.163 2.366 0.406 0.097 0.003 0.000 0.001 106.695 97.210 185.827 144.722
121
Juvenile 3 – SLMEM 276
Elemental Concentrations
Isotopic Composition
0.01
0.1
1
10
100
1000
1946 1956 1966 1976 1986 1996 2006
pp
m
Time (sec)
Sr
Th
U
0.71
0.712
0.714
0.716
0.718
0.72
0.722
0.724
1 2 3 4 5 6
87 S
r/8
6 Sr
Spot Number
Average 87
Sr/86
Sr ratios *
Enamel Dentine 87
Sr/86
Sr 2se 87
Sr/86
Sr 2se
0.723010 0.000777 0.711027 0.000277
*From selected zones, avoiding areas
affected by diagenesis areas where possible
Elemental Concentrations – High and low zones 238
U Concentration (ppm) 232
Th Concentration (ppm) 88
Sr Concentration (ppm)
EN
High
EN
Low
DE
High
DE
Low
EN
High
EN
Low
DE
High
DE
Low
EN High EN Low DE
High
DE
Low
0.461 0.294 43.138 28.465 0.125 0.003 0.002 0.019 56.091 50.915 190.385 142.930
122
Juvenile 4 – SLMEM 66
Elemental Concentrations
Isotopic Composition
0.01
0.1
1
10
100
1000
1220 1270 1320 1370
pp
m
Time (sec)
Sr
Th
U
0.71
0.712
0.714
0.716
0.718
0.72
0.722
1 2 3 4 5 6 7 8 9
87 S
r/8
6 Sr
Spot Number
Average 87
Sr/86
Sr ratios *
Enamel Dentine 87
Sr/86
Sr 2se 87
Sr/86
Sr 2se
0.719776 0.000753 0.711141 0.000309
*From selected zones, avoiding areas
affected by diagenesis areas where possible
Elemental Concentrations – High and low zones 238
U Concentration (ppm) 232
Th Concentration (ppm) 88
Sr Concentration (ppm)
EN
High
EN
Low
DE
High
DE
Low
EN
High
EN
Low
DE
High
DE
Low
EN High EN Low DE
High
DE
Low
0.097 0.011 5.164 0.296 0.041 0.001 0.001 0.015 55.134 51.638 146.413 106.258
123
Juvenile 5 – SLMEM 102
Elemental Concentrations
Isotopic Composition
0.01
0.1
1
10
100
1000
562 582 602 622 642 662
pp
m
Time (sec)
Sr
Th
U
0.711
0.7115
0.712
0.7125
0.713
0.7135
0.714
0.7145
0.715
1 2 3 4 5 6 7 8
87 S
r/8
6 Sr
Spot Number
Average 87
Sr/86
Sr ratios *
Enamel Dentine 87
Sr/86
Sr 2se 87
Sr/86
Sr 2se
0.714607 0.000593 0.711664 0.000301
*From selected zones, avoiding areas
affected by diagenesis areas where possible
Elemental Concentrations – High and low zones 238
U Concentration (ppm) 232
Th Concentration (ppm) 88
Sr Concentration (ppm)
EN
High
EN
Low
DE
High
DE
Low
EN
High
EN
Low
DE
High
DE
Low
EN High EN Low DE
High
DE
Low
0.545 0.354 23.722 17.714 0.025 0.004 0.020 0.008 68.776 66.929 147.171 144.415
124
Juvenile 6 – SLMEM 119
Elemental Concentrations
Isotopic Composition
0.01
0.1
1
10
100
1000
2562 2582 2602 2622 2642 2662
pp
m
Time (sec)
Sr
Th
U
0.71
0.712
0.714
0.716
0.718
0.72
1 2 3 4 5 6 7
87 S
r/8
6 Sr
Spot Number
Average 87
Sr/86
Sr ratios *
Enamel Dentine 87
Sr/86
Sr 2se 87
Sr/86
Sr 2se
0.719197 0.000555 0.711825 0.000301
*From selected zones, avoiding areas
affected by diagenesis areas where possible
Elemental Concentrations – High and low zones 238
U Concentration (ppm) 232
Th Concentration (ppm) 88
Sr Concentration (ppm)
EN
High
EN
Low
DE
High
DE
Low
EN
High
EN
Low
DE
High
DE
Low
EN High EN Low DE
High
DE
Low
- 0.717 20.225 17.848 - 0.005 0.019 0.008 - 64.810 140.582 134.989
125
Juvenile 7 – SLMEM 86
Elemental Concentrations
Isotopic Composition
0.01
0.1
1
10
100
1000
1225 1245 1265 1285 1305 1325
pp
m
Time (sec)
Sr
Th
U
0.71
0.712
0.714
0.716
0.718
0.72
0.722
1 2 3 4 5 6 7
87Sr
/86 S
r
Spot Number
Average 87
Sr/86
Sr ratios *
Enamel Dentine 87
Sr/86
Sr 2se 87
Sr/86
Sr 2se
0.719931 0.000486 0.711542 0.000281
*From selected zones, avoiding areas
affected by diagenesis areas where possible
Elemental Concentrations – High and low zones 238
U Concentration (ppm) 232
Th Concentration (ppm) 88
Sr Concentration (ppm)
EN
High
EN
Low
DE
High
DE
Low
EN
High
EN
Low
DE
High
DE
Low
EN High EN Low DE
High
DE
Low
5.251 0.221 12.593 7.602 0.019 0.002 0.038 0.011 132.823 64.493 139.181 134.664
126
Juvenile 8 – SLMEM 291
Elemental Concentrations
Isotopic Composition
0.01
0.1
1
10
100
1000
558 578 598 618 638 658
pp
m
Time (sec)
Sr
Th
U
0.71
0.711
0.712
0.713
0.714
0.715
0.716
0.717
0.718
0.719
1 2 3 4 5 6 7
87 S
r/8
6 Sr
Spot Number
Average 87
Sr/86
Sr ratios *
Enamel Dentine 87
Sr/86
Sr 2se 87
Sr/86
Sr 2se
0.718307 0.000488 0.711095 0.000289
*From selected zones, avoiding areas
affected by diagenesis areas where possible
Elemental Concentrations – High and low zones 238
U Concentration (ppm) 232
Th Concentration (ppm) 88
Sr Concentration (ppm)
EN
High
EN
Low
DE
High
DE
Low
EN
High
EN
Low
DE
High
DE
Low
EN High EN Low DE
High
DE
Low
2.815 1.628 28.328 - 0.013 0.002 0.021 - 78.798 64.271 147.678 -