SCHOOL OF CONSERVATION SCIENCES

Investigating Anglo-Saxon population movement using strontium stable isotope analysis

Sampling tooth enamel from individuals found at Frome View, Bradford Peverell

A dissertation submitted as part of the requirement for MSc Forensic Archaeology

By

Annemieke M. DoornbosSeptember 2010

ABSTRACT

This study makes use of strontium stable isotope analysis through Thermal Ionization Mass

Spectrometry on human tooth enamel to identify local and non-local individuals within one

burial place. Stromtium ratios were measured in order to shed some light on the diet of the

individuals during a certain period of their lives. Because the aim of the investigation is to

find out where the individuals come from, samples of tooth enamel were used, that does not

remodel after being formed and mineralized and therefore forms an archive for strontium that

was stored during formation and mineralization of the enamel, which occurred during

childhood. The teeth that were investigated, were selected from a number of burials found at

Frome View, Bradford Peverell in Dorset, believed to be of the Anglo-Saxon period. The

samples were prepared by taking a number of steps involving taking the enamel out of the rest

of the tooth, cleaning the enamel, dissolving it in acid and running it through a strontium

column and the mass spectrometer in order to get the strontium values that were present in

the enamel. By doing so, three individuals were found showing a strontium value that was

not of local origin. With the great variation in strontium values came the characteristics of the

burials themselves, where unusual objects were found, a unusual short individual and on the

other hand a very robust individual. Unfortunately this study coped with a limitation in time

and money and could therefore not be investigated as elaborately as one might have wanted

to. Recommendations that can therefore be given, involves a further investigation of these

individuals by using other stable isotopes in order to back up the results found in this

investigation. Also if stable isotope analysis appears to be that usefull, further research should

be done in other disciplines, for instance applying the strontium stable isotope analysis on

forensic cases.

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ACKNOWLEDGEMENTS

In this case study, I have had the help of some very important people who need to be

mentioned. Firstly, I thank Dr. Martin J. Smith, of the anthropology department at

Bournemouth University for giving me the opportunity to work with the human remains

found at Bradford Peverell, Dorset and for being my supervisor throughout the investigation,

guiding me in the right direction and giving me a lot of motivation.

Secondly I have to thank Matt Cooper and the National Oceanographic Centre in

Southampton. Without their help, the strontium isotope analysis would not have been able.

Also I am greatful for the time and devotion Matt Cooper showed in this case study, taking

the responsibility to teach me how to perform strontium stable isotope analysis.

Another very special thankyou goes to Mr. Hawthorne and Mr. Keen. Mr. Hawthorne for

giving me the opportunity to be able to see the place where the human remains were found, in

his back garden, but also for giving me so much useful information. And Mr. Keen, who has

been the archaeologist that excavated the human remains, for sheding so much light on the

case and sharing all his ideas and knowledge on the matter.

Also, a thankyou must be given to Rebecca Redfern of the Museum of London Archaeology,

for informing us about the skeletons and for getting me and my supervisor in contact with Mr.

Hawthorne in order to work with the remains found in his back garden.

Thankyou to Jane Evans and Janet Montgomery, for providing the strontium biosphere

geological map of the UK and for being a good inspiration and motivation for me to

understand the difficulties of strontium stable isotope analysis.

I would like to thank Jamie Auton, a postgraduate student in Recovery and Identification of

Human Remains at Bournemouth University who I have been able to work with on this case

and who has given me so much insight and information on the skeletal material.

Finally, a thankyou to family and friends who have kept me motivated when things were not

going as planned and for being there when help was needed.

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CONTENTS

ABSTRACT i

ACKNOWLEDGEMENTS ii

TABLE OF CONTENTS iii

LIST OF FIGURES v

LIST OF TABLES vi

CHAPTER ONE INTRODUCTION 1

1.1 Aims and Objectives 1

1.2 Anglo-Saxon population movement 3

CHAPTER TWO ARCHAEOLOGICAL BACKGROUND AND CONTEXT 5

2.1 The human remains of Frome View 5

2.2 Site geology 8

2.3 Burial practice and grave orientation 8

2.4 Grave goods found at Bradford Peverell 9

CHAPTER THREE STRONTIUM 14

3.1 The geochemical characteristics of strontium 14

3.2 Strontium uptake in plants and mammals 16

CHAPTER FOUR THE HUMAN TEETH 18

4.1 Formation of the teeth 19

4.1.1 Formation and eruption of the permanent teeth 20

4.1.2 Formation of the enamel 21

4.2 Strontium in human tooth analysis 23

CHAPTER FIVE METHODOLOGY 24

5.1 The samples used in this study 24

5.1.1 Sample selection 24

5.1.2 Tooth sample preparation 25

5.2 Preparation of the Strontium columns 26

5.3 Collection of strontium and TIMS analysis 28

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CHAPTER SIX RESULTS 30

CHAPTER SEVEN DISCUSSION OF THE RESULTS 32

7.1 Diagenesis 32

7.2 The strontium data 33

7.3 Archaeological evidence to indicate migration 35

7.3.1 Burial 5 35

7.3.2 Burial 12 36

7.3.3 Burial 17 36

7.4 Limitations of this study 36

CHAPTER EIGHT CONCLUSIONS 38

CHAPTER NINE FURTHER RECOMMENDATIONS 39

REFERENCES 41

APPENDIX I I

APPENDIX II II

APPENDIX III III

APPENDIX IV IV

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LIST OF FIGURES

CHAPTER TWO

FIGURE 1 The first eight burials found 6

FIGURE 2 Grave goods found in Burial 1 10

FIGURE 3 Objects found in burial 5 11

FIGURE 4 Objects obtained from burial 10 11

FIGURE 5 Knives found in the burials 12

CHAPTER FIVE

FIGURE 6 Diagram of the mandibular right first permanent molar 25

FIGURE 7 Strontium column showing the level of the Sr resin 27

CHAPTER SIX

FIGURE 8 Plot of 87Sr/86Sr ratios found in the tooth enamel 31

LIST OF TABLES

CHAPTER FOUR

TABLE 1 Timing of formation of permanent dentition in years 20

CHAPTER SIX

TABLE 2 An overview of the results found in the tooth enamel 30

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CHAPTER ONE

INTRODUCTION

At Frome View, Bradford Peverell, Dorset, thirty-three years ago, an amateur archaeologist

Mr. John Hawthorne planned to build an extension to his house and the construction of a new

patio. When starting this operation, he stumbled upon what appeared to be human remains.

Now, thirty-three years later, this has led to the excavation of sixteen burials in total, dating

the burial ground to Anglo-Saxon times around the 5 th – 7th century A.D. The remains, found

laid out in neat rows, do not necessarily appear to be from a cemetery, since ‘only’ 16 burials

were found, however it raises the question as to why these individuals were buried here and

what their place of origin is. Being buried with iron knives, buckles and other distinctive

items, but also with golden beads, these individuals appear to be showing differences in status

but maybe also differences in place of origin and might therefore be linked to the Migration

Period in which many people travelled throughout Britain.

1.1 AIMS AND OBJECTIVES

Dealing with the Anglo-Saxon human remains, a couple of questions arise. One of the things

an archaeologist wonders is whether all the skeletons found in this area, originate from the

same group. But how can a ‘local’ be distinguished from a ‘non-local’ person? In other words,

how can migration or even just population movement be detected in a case study? In order to

find out whether this group of Anglo-Saxon human remains consisted of people originating

from the area where they were found after being buried, this study focuses on stable isotope

analysis, a method used to detect the geological area of residence during a certain period of an

individual’s live. To be able to trace the geological area where the individuals have lived

during a particular period of life, this study makes use of the strontium isotopes. Strontium

isotopes are trace elements found in teeth and bones and can give answers to the question

whether people are local or non-local. Previous studies using strontium stable isotope analysis

in order to make a distinction between local people and non-locals have proven to be very

useful (Chenery et al., 2010, p.150; Price & Gestsdóttir, 2006; Evans & Tatham, 2004;

Bentley, 2003).

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Therefore the specific aim of this research is:

To determine if the remains found at Frome View, Bradford Peverell, are

local or non-local to the area in which they were buried, with the use of

strontium stable isotope analysis applied on human tooth enamel.

In order to meet this aim, a number of objectives must be followed which are listed below.

1. First of all, a literature review must be conducted in order to get an overview of what

has already been published in this field of study. The aim of this literature review is

not to prove that stable isotope analysis is indeed useful for the researching population

movement, but rather used as a means of providing information in order to fully

comprehend and justify what it is that strontium stable isotope analysis does, how it is

conducted and which certain parts of skeletal remains are best to be used for this

study.

2. Having an overview of the present literature, six individuals found in Bradford

Peverell must be selected after which the right mandibular first molar must be taken of

each of the selected individuals. To confirm that the right teeth have been taken from

the skeletal remains, help from an anthropologist must be asked.

3. After selecting the teeth samples, the teeth must be cleaned professionally, bearing in

mind that the level of contamination must be kept as low as possible or even fully

prevented where possible.

4. When the teeth are clean, the enamel must be separated from all other tooth material.

The way in which this is done is with the use of a hammer and a scalpel in order to

split the teeth so that after this the dentine present inside the tooth can be chipped

away. Very important in this objective is the fact that all the dentine must be taken off

the enamel before the enamel can be used for further investigation. This is done with

the use of a dental dremel tool.

5. The next thing that has to be done involves obtaining the strontium from the enamel

samples and measuring the strontium ratios. To accomplish this, a Teflon column has

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to be prepared holding the strontium resin to bind the Sr parts from to tooth sample to.

In the meantime, the samples will have to be dissolved in acid after which the solution

is run through the prepared columns. In order to obtain the Sr, finally water needs to

be run through the column which has to be collected in Teflon vials. The strontium

collected from the samples then needs to be loaded on a Tantalum filament and put in

the TIMS machine that will measure the strontium ratios.

6. When the strontium ratio results are known, a geological map of Britain must be used,

showing average strontium ratio values present in the biosphere in each geological

area. By comparing the strontium values found in the enamel samples to the strontium

values present on the map in the area in which the skeletal remains were found, an

assumption can be made concerning whether the individuals are local to the area in

which they were found or if they appear to have come from a different area.

1.2 ANGLO-SAXON POPULATION MOVEMENT

Before going into this study on possible population movement among the Anglo-Saxon

individuals found at Bradford Peverell, it is essential that one has some knowledge of Anglo-

Saxon history, in particular the Migration Period. Many historical texts speak of ‘the coming

of the Saxons’ or as it is known in Latin: the Adventus Saxonum (Lucy, 2000, p.156). Many

historians in the past have placed the arrival of the Saxons in mid-5 th century A.D. however,

other dates have also been mentioned (Lucy, 2000, p.157). The main idea of the event is that

three Germanic tribes called the Saxons, the Angles and the Jutes came from Germania

towards Britain. Unfortunately all this information is derived from historical texts that were

written with a certain purpose. Lucy mentions that from the sixth century onwards, people

were trying to place European people in different categories, meaning that it became a trend

to ‘fantasize’ about the origin of different European groups. Through time, not much evidence

has come up concerning the Migration Period which is why these stories about the Saxons

entering Britain tend to be labeled under the name ‘origin myth’ (Lucy, 2000, p.158). This

way various origin myths have been written on the Angles, the Saxons and the Jutes, all with

a slightly different story about origin. That people were moving around during the Migration

Period might be true, but if it was the case that these three Germanic groups entered Britain

during this period, remains unsure (Lucy, 2000, p.158; Montgomery, 2002).

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In the case of migration, or moving from one place to another for that matter, during Anglo-

Saxon times, questions arise concerning the area that was crossed. During Anglo-Saxon times,

people were obviously a lot less mobile than we are nowadays which makes one wonder if

they would cross large areas across countries or if they would just move from one place to

another close by and work from there. What could be of importance when trying to answer

this question is the goal that those populations had, what their main reason was to move in the

first place, for instance to just cross an area in search for better living conditions or in order to

follow family. According to Montgomery, in the case of migration, people are far more likely

to follow their family members or friends to a particular place rather than just going

somewhere on their own in order to find a new place to live. In the case of investigating the

movement of an entire population, it is therefore interesting to look further into a migration

route because the migration between two places might have lasted longer than during one

single migration event (Montgomery, 2002, p.223).

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CHAPTER TWO

ARCHAEOLOGICAL BACKGROUND AND CONTEXT

2.1 THE HUMAN REMAINS OF FROME VIEW

The human remains used for this research were found at Frome View, a bungalow owned by

Mr. J.B. Hawthorne during preparation work for an extension to his house and the building of

a patio leading from the back of the bungalow into the back garden. Over 33 years, bit by bit a

total of 18 burials were excavated, documented and recorded. As published in the

´Proceedings of Dorset Natural History and Archaeological Society´, archaeologist Laurence

Keen was assigned to the project as soon as it became known that human remains were found

and from 1977 onwards, Mr. Keen and the owner of Frome View, Mr. Hawthorne, published

the archaeological excavation notes. In this section, an overview of these notes will be given

in order to give the reader background information of the case-study used for this paper.

In 1977, the first eight burials were found, all of which contained human skeletal remains.

These shallow graves were cut into the chalk bedrock and were neatly laid out in two rows.

The skeletons found in the graves were buried with their heads towards the west and the feet

towards the east, lying in a stretched position. Burial 1 was very waterlogged when it was

found and of the human remains that were present in it, the leg bones were extended over the

grave cut, implying that the individual did not fully fit in the deepest part of the grave. Around

the pelvis, grave goods were found which will be further explained later on. In burial 4

remains were found of what appeared to be a female. Unfortunately, the skull found in this

grave appeared to have been smashed which makes identification of the individual more

difficult (Keen, 2010, pers. comm.).

Burial 5 appeared to hold the remains of a young female, who was buried with some

interesting grave goods. The reason why these grave goods appear to be interesting is the fact

that they consisted of a couple of beads that seem to belong to some sort of necklace.

According to Mr. Keen, two of the beads found contain golden material, which was obviously

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quite precious during the Anglo-Saxon period. Further explanation will be given in the

chapter on grave goods which will be presented later in this paper.

When burial 6 was excavated, only a few long bones were found next to some teeth in the foot

end of the grave. In the notes in Dorset Archaeology, the archaeologist states that the graves

probably date around the seventh century A.D (Keen, 1977, p.120; Keen & Hawthorne, pers.

comm.).

Fig. 1 The first eight burials found (Mr. J. Hawthorne, 2010, pers. comm.)

The publication of this case continues in 1978, when Mr. Keen and Mr. Hawthorne discover

another two burials. Both burials were again showing human remains in a stretched position

with their heads at the west-end of the grave. The interesting thing about the tenth burial

containing human remains is that according to anthropological research, there were too many

bones present in this burial. Why this is the case remains unknown. The human remains found

in these graves were found with various objects buried with them. Dating methods that were

used on these objects, confirmed that the graves were dating from the late seventh- to early

eighth-century A.D (Keen, 1978, p.112).

The excavation of Mr. Hawthorne’s back garden continued in 1979. In this year, another two

graves were excavated, bringing this case to a total of 12 graves containing human remains.

One of the burials was quite deep compared to the graves that were previously excavated,

with a depth of about 50 centimetres into the chalk bedrock. In this burial the human remains

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of an individual were found in a slightly flexed position. The second grave, burial number 12,

showed a shallow grave cut, going into the natural chalk bedrock for about 15 to 30

centimetres. What is interesting about this grave is that it is only 4 foot 8 inches long and

appears to be holding the remains of a male, which would then have been an unusually short

individual (Keen, 1979, p.133).

The publications in Dorset Archaeology continue in 1981 with the excavation of the thirteenth

grave, found adjacent to burial 7 which formed the end of a row of seven burials. Burial

number 13 appeared to be a shallow grave with a cut going into the chalk bedrock for only a

few centimetres. The human remains that were found in this grave were slightly flexed and

appear to be those of a young male (Hawthorne, 1981, p.126).

Between 1981 and 1989 unfortunately not much was published. From the overview of the

burials shown in appendix II, number 14 seems to be an empty pit, too small to have

contained human remains. Burial 15 however, contained human remains. The photo of burial

15, shown in appendix I, was made by Mr. Hawthorne himself in 1983 and picture the

remains of possibly a female.

In 1989, another burial was excavated that was already located between 1981 and 1989. By

this time the total number of burials found is 16, of which 15 burials contain human remains.

Again this burial consists of a shallow cut leading into the chalk bedrock. The skeletal

remains in grave 16 were found with slightly bent knees and no skull seemed to be present.

With the human remains, pieces of an iron object were found which were thought to be those

of an iron knife. On the knees of the individual excavated, large pieces of flint were also

found (Hawthorne & Pinder, 1989, p.110-111).

Later on, as the excavation continued, the last two graves were discovered. According to

anthropological research done on the human remains from Bradford Peverell, burial 17

appeared to show the remains of a large, robust male. The last burial, number 18, showed a

shallow grave, holding the remains of an individual. What is interesting about burial 18 is the

fact that there were no grave goods found in this one however, the grave cut was made quite

large for the human remains to fit in. According to archaeologist Mr. Keen, burial 18 appears

to have been robbed in the past before it was discovered in Mr. Hawthorne’s back garden. A

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complete overview of the burials discovered in Mr. Hawthorne’s rear garden can be seen in

Appendix II.

Reviewing the excavation notes concerning the burials, one can see interesting features, like

for instance the beads found with the remains of a young female in burial 5, appearance of

burial 12 which seems to have held the remains of an unusually short adult male and burial 17

which contains the remains of quite a large robust male.

2.2 SITE GEOLOGY

Bradford Peverell is a town in Dorset, which is built on top of Cretaceous bedrock as can be

seen in Appendix II. Cretaceous geology consists mostly of chalk bedrock with a layer of

greensand on top. The formation during the Cretaceous period started with a layer of marls

and Marley limestone, which was followed by a layer of clay or silty clay. Finally a layer of

sand was deposited on the clay soil. This layer of sand consists mainly of marine sand (British

Geological Survey, 2008, p.4). Light types of soil, like the sandy soil layer found at Bradford

Peverell, was often used to build Anglo-Saxon cemeteries on during the 5 th and 7th century

A.D. Nowadays this is not the case because sandy soils have become unreliable due to eroded

and weathered bedrock (Montgomery, 2002, p.221).

2.3 BURIAL PRACTICE AND GRAVE ORIENTATION

At Frome View, Bradford Peverell, a total of 17 inhumations were recovered, most of them

buried with their heads towards the west. The bones of the burials were in fair to poor

condition (Auton, 2010) and were found fairly close to the current land surface. During the 5 th

and the 6th century, many cemeteries consisted of burials laid out in neat rows with the head at

the west end of the grave (Lucy, 2000, p.130). An article written by Petts shows an example

of neat rows of burials, orientated from west to east, already present during the Late-Roman

period when inhumation became more popular in Anglo-Saxon England (Petts, 1998, p.114).

Throughout the Anglo-Saxon period, cemeteries holding a large amount of inhumations were

widely used. Often these cemeteries with Anglian graves were cemeteries from the Roman

Period that were re-used as can be seen in the case study of west Heslerton (Lucy, 2000, p.

126; Montgomery, 2002, ch. 7; Montgomery et al., 2005). Because the Anglo-Saxon

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population made use from already existing burial places, archaeologists have often found it

difficult to make notes on the stratigraphy of these cemeteries due to inter-cuttings present

between the graves. Among the inhumation burials, the most common position, in which the

individual would be buried in the area of Dorchester, was the extended supine position. The

extended supine position means that the humain remains were placed on the back in a

stretched position. Sometimes, the bodies are found placed on the side (Lucy, 2000, p.78; see

also: Pettitt & Bader, 2000) In this position, the legs are often found stretched out, in

contracted position or just slightly flexed.

As mentioned before, the burials from Bradford Peverell that were used for this study, were

mostly buried with their heads towards the west. Burying individuals with the head end of the

grave towards the west appears to be a tradition when it comes to Anglo-Saxon burials

(Richardson, 2005, p.108). According to Montgomery, some people tend to address to the

burial orientation to differentiate between natives from the area, also referred to as Briton and

the Anglo-Saxon or the immigrants:

“Orientation with the head pointing somewhere between the north and north-east is typical

of Iron Age burials throughout the whole of Britain, Examination of 5293 Anglo-Saxon

inhumations shows that the normal pagan rite was extended or loosely-flexed burial, either

supine or on one side, with the great majority orientated with heads pointing somewhere in

the western section of the compass...burials of the Roman period seem to continue the

native traditions” (Faull, 1977, cited by: Montgomery, 2002, p.229).

Another similar opinion is shared in an article written by Elisabeth O’Brien who states that

during the Iron Age, most favoured grave orientation was from north to south. She also

mentions that throughout the Roman Period, this trend started to change and started to move

towards a burial orientation from west to east (O’Brien, 1999, p.5). Something one has to bear

in mind though is the fact that in Christian burials the head was often facing towards the west

as well, so the idea of having a burial orientation from west to east cannot be seen solely as an

Anglo-Saxon characteristic.

2.4 GRAVE GOODS FOUND AT BRADFORD PEVERELL

As mentioned in the excavation notes by Mr. Keen, several objects were found in the burials

during the excavation. In five of the first eight burials that were uncovered, grave goods were

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found. Three of which contained a small iron knife. The knife found in burial 2 is interesting

in particular, because in this grave the knife was found on the right side of the skeletal

remains, whereas in all the other graves where knives were recovered, they were found on the

left side of the remains (Keen, 2010, pers. comm.). Next to the knives found in these burials,

burial 1 contained a bone comb, iron objects, a bronze ring and a silvered bronze purse mount.

Fig.2 Grave goods found in Burial 1 (adapted from: Mr. J. Hawthorne, 2010, pers. comm.)

In burial 5 the remains of what seemed to be a young female were found wearing a necklace

made of glass beads, a bead made of golden wire, a triangular bead pendant consisting of a

cabochon held in a golden setting and a circular shaped pendant with a glass setting. In this

burial, also the remains of a set of two disks were found, made of punched silver. Furthermore

at the waist of the young female, part of a bronze buckle was found together with two coins of

punched metal and a large round disk made of bronze.

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Fig. 3 Objects found in burial 5 (adapted from: Mr. J. Hawthorne, 2010, pers. comm.)

In the ninth grave that was discovered in 1978, an iron object was found which turned out to

be unidentifiable. However, the topsoil that was removed from burial 9 contained rusty nails.

According to Mr. Keen, these nails could have been part of something bigger that was laid on

top of the grave, like for instance a shield. Underneath the remains, a bronze pin was found

and on the left side next to the body there appeared to be a round patch containing the bones

of a bird. What this could mean is unsure. In the tenth grave, a spearhead was found together

with a small knife and a buckle made of bronze and iron. Also, some worked bone was found

and the bronze end of a shoelace (Keen, 2010, pers. comm.).

Fig. 4 Objects obtained from burial 10 (adapted from: Mr. J. Hawthorne, 2010, pers. comm.)

When burial 11 and 12 were excavated, again iron knives were found. It seems likely that it

was quite common during the Anglo-Saxon period to bury iron knives together with the

individuals. This could have been because of religious beliefs (Williams, 1998, p.97). In the

literature present on Romano-British and Anglo-Saxon grave goods, there are often leaf

shaped knives mentioned. According to an article by Elizabeth O’Brien, during the 5 th to 7th

century A.D., burial rites present during the Romano-British period were not affected by the

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Anglo-Saxons (O’Brien, 1999, p.30). Burial 11 also contained large pieces of flint at the head

and the foot end of the grave-cut. When the archaeologist investigated the grave further, small

pits were found underneath the large flint pieces. According to Mr. Keen, these pits are

believed to have been holding posts in order to mark the grave-cut. In the cut from burial 12, a

small iron knife was found at the head end of the burial. A reason given for a knife being

buried at the head end of the burial is that of the individual buried being a slave. It is unknown

if this was indeed the case in this particular grave (Keen, 2010, pers. comm.).

Fig. 5 Knives found in the burials (adapted from: Mr. J. Hawthorne, 2010, pers. comm.)

During the excavation of burial 13, an iron knife, a bronze buckle and a second iron object

between the knees were uncovered. Finally in burial 18, a row of flints was found around the

midriff of the individual with a cone underneath the body. Next to these objects not much was

found and it is believed that this grave was robbed before the excavation (Keen, 2010, pers.

comm.).

Looking at this overview of the objects found within the burials, one can see that burial 5

really stands out. First of all, no knife was found in this grave whereas in most other burials

this was the case. Furthermore, beads were found of which two contained golden material

which could be from some sort of higher class or simply a different geological area which can

also be found back in the silver disks and the large disk made from bronze. Social status

represented through grave goods is also mentioned in a case-study by Howard Williams on

monuments in Anglo-Saxon England (Williams, 1998, p.96). Social status is shown by the

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value of the objects found in the burial. The higher the value of the objects, the higher ones

status has probably been. Another burial that seems to be interesting is number 12, where a

knife was found above the head which is interesting as all other knives were found alongside

the skeletal remains. Although it is unsure why this is the case, stable isotope analysis might

be able to shed some light on these burials and their characteristics.

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CHAPTER THREE

STRONTIUM

Using strontium stable isotope analysis, in order to detect migration, relies on the fact that

strontium is an element which in some cases is formed due to radioactive decay. Because of

this characteristic, the ratios of strontium present in rocks can change per individual rock type,

forming so called isotope fingerprints. The amount of strontium found in each rock type was

formed during the time of mineralization which means that once the rock is formed, no

significant changes can occur concerning the amount of strontium present in that particular

rock. This is why with the use of these ratios, strontium found in plant and animal material

can be traced back to its original geological area by comparing the ratios found in the sample

to the ratios known by rock types in various areas throughout the world (Montgomery, 2002,

p. 22).

3.1 THE GEOCHEMICAL CHARACTERISTICS OF STRONTIUM

Strontium occurs in four different forms of stable isotopes, those being: 84Sr, 86Sr, 87Sr and 88Sr. Isotopes are different types of atoms each containing the same amount of protons, or

positively loaded parts, but different amounts of neutrons, or neutral parts (Pye, 2004, p.218,

p.220; Price & Gestsdóttir, 2006, p.132). The first two and the last one are constant stable

isotopes whereas 87Sr is formed out of rubidium (87Rb) which is a particle with a radioactive

decay with a half-life of 4.88 x 1010 years, meaning that it looses half of its amount

(Montgomery 2002, p.23; Åberg, 1998, p.111; see also Pye, 2004, p.218; Price & Gestsdóttir,

2006, p.132-133). Both 87Rb and its radiogenic product 87Sr, occur naturally in rocks and other

mineralized material (Montgomery et al., 2000, p.371). Because 87Sr is formed out of the

decay of radioactive 87Rb, this stable isotope is also referred to as a radiogenic isotope (Pye,

2004, p.218).

The amount in which 87Sr is present in rock and other materials, depends on the ratio of Rb/Sr,

but in the case of rocks, it also depends on the age of the rock (Budd et al., 2004, p.128).

Since the number of years in which half of the 87Rb turns into 87Sr is relatively great, this does

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not affect the archaeological time-line and can therefore be measured and used in order to

distinguish geological areas. In archaeological studies, a ratio of 87Sr and 86Sr is measured

(87Sr/86Sr) because these two stable isotopes occur in about the same amounts in the natural

atmosphere. The reason why 87Sr has to be measured in a ratio, together with 86Sr is based on

the idea that the amount of 86Sr is constant whereas the amount of 87Sr varies due to the decay

of 87Rb (Montgomery, 2002, p. 24).

Strontium ratios in the UK can vary from 0.703 to 0.740 (Montgomery et al., 2000, p.371).

Strontium ratios from samples from Anglo-Saxon England found in previous studies appear to

range from 0.708 to 0.712 (Price & Gestsdóttir, 2006, p.136). The strontium ratios are

measured with the use of a mass spectrometer which can produce measurements with an

accuracy of up to approximately 0.00002, of which an accuracy of up to a third decimal is

usually noteworthy in the study of population movement (Montgomery et al., 2000, p.371;

Price & Gestsdóttir, 2006, p.133; Pye, 2004, p.220). By measuring the ratio, one can find out

in which geological area an individual spent a certain part of his or her life.

When it comes to strontium in mineral material, strontium is an element that is similar to

calcium (Ca) and barium (Ba) in its characteristics. It is known to be silicate loving and is

often traced back in mineralized material such as rocks, bones and teeth where it tends to take

the place of calcium (Montgomery, 2002, p.23; Montgomery et al., 2000, p.371). Part of the

strontium present in rocks is released over time due to weathering. This is how it ends up in

the soil and groundwater, but also in plants that take up the groundwater, which is how Sr

eventually ends up in animals and humans via ingestion of food and water. However, one

must bear in mind that the amount of strontium that ends up in either bone or tooth material,

does not reflect the exact same amount of strontium that was present in the rock from which it

originally came.

Looking at strontium present in soils and the groundwater, as well as the water that flows in

rivers, the amount of strontium present usually represents the ratio in the natural bedrock

underneath the soil and the water. However, there are cases in which it is mentioned that one

cannot just take this as a fact. The reason given for this is that those ratios are able to change

over time, depending on changes in the amount of strontium that is released from the bedrock

through weathering, but also through other changes in for instance the atmosphere, where

~ 15 ~

strontium is present in the rain water which is formed out of evaporated sea water

(Montgomery, 2002, p.24).

The idea that the strontium ratio could change over a relatively short period of time plays an

important role in this study. This is because it is dealing with archaeological human remains

that were buried in the soil a long time ago, soil that is older than the modern soil on top of it,

therefore possibly showing different strontium values than the modern soil on which the

geological map is based, which is in turn used to analyse the results later in this study. Also,

events such as land-use over time could have caused differences in strontium values, due to

contamination after the remains were buried. Even though it has not proven to cause great

differences in the results of previous studies, or pose problems for their overall outcomes, it is

certainly something to consider in an archaeological investigation such as this (Montgomery,

2002, p.27).

3.2 STRONTIUM UPTAKE IN PLANTS AND MAMMALS

In the previous section it is shown that strontium has similar characteristics as calcium and

therefore takes the place of some of the calcium present in mineralized materials. When it

comes to human remains, this means that most strontium stores itself in the hard parts of the

skeletal material like the teeth, and in particular the tooth enamel. Before strontium enters the

human body it travels through the food chain and through various trophic levels. It starts with

the plants taking up the strontium via their roots, from the soil where the strontium was

leached into. The principle, on which the process of the absorption of strontium is based, is

the same as that of the uptake of strontium in rocks or skeletal material: strontium substitutes

for calcium (Montgomery, 2002, p.36).

From the plants strontium then travels to the next level: the animals that eat the plants and

drink water. Studies that have been conducted on the amount of strontium present in

mammals and the uptake of strontium through food and drink have resulted in the fact that,

the strontium ratio measured in mammals shows a direct reflection of the amount of strontium

that was available during ingestion. This means that 100% of the strontium ingested was taken

up in order to replace calcium, whereas with plants this is not the case, as the absorption of

calcium is dominant over that of strontium in plant material. Because strontium is non-toxic to

mammals, it is taken up in the body naturally (Åberg, 1998, p.110).

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In skeletal material, strontium is spread out evenly, making the concentrations of strontium

throughout different parts of the skeleton similar. What is often the case though is that bone

and dentine contain a slightly higher amount of strontium than tooth enamel. A reason given

by Montgomery is the fact that bone and dentine have a larger surface to catch the absorption

of strontium. What could also be the case is the idea that both dentine and bone material are

able to remodel, whereas tooth enamel is incapable of doing so (Montgomery, 2002, p. 37).

When it comes to measuring strontium ratios in human remains, one can see that this does not

only vary per material of the human remains that are measured, but also that it varies

geographically. This has to do with variations in diet and variations in amounts of strontium

present in the water, which is therefore based on geological differences throughout the world.

However, one must realise that there are also cultural differences that are reflected in what is

eaten and where it is obtained from. These differences in strontium ratios and the connection

with geographical differences are very useful in migration studies because they can give

information on changes that occur in diets, which may then result in giving consequent

information on population movements from one place to another, making dietary change very

likely among humans (Montgomery, 2002, p.38).

Strontium ratios and other isotope ratios present in human remains are not only used in order

to allow for investigation into human migration, but also for investigation in dietary purposes.

By researching the amount of strontium present in skeletal remains, one can say something

about the origin of the food and drinks that have been ingested. Examples of studies that use

this are: Privatet al., 2002, Jørkov et al., 2008 and Chenery et al., 2010.

~ 17 ~

CHAPTER FOUR

THE HUMAN TEETH

In this paper, the investigation is dealing with finding the origin of the individuals found in

Mr. Hawthorne’s back garden. To be able to do this, information is needed that will lead the

archaeological research to this part, therefore evidence from the human remains is needed that

can tell the archaeologist something about the childhood of the individuals found in the

graves. In the study of migration and/or origins of humans and animals, various tissues can be

used in order to trace the information back to the childhood or place of birth like bone

material, hairs, teeth and skin. However, all of these different materials hold the information

of different periods in life and in archaeological cases usually only the bone and tooth

material survives. Tooth enamel is known to contain information concerning ones diet during

childhood whereas bone material tends to hold information concerning the last six to ten years

of an individual’s life (Montgomery, 2002, p.46; Montgomery et al., 2000, p.372). Teeth in

general are seen as good indicators for migration studies, because different teeth are formed at

different stages during life and therefore hold the information of different stages of life (Budd

et al., 2004, p.128).

For this particular case teeth are being used as samples. Unlike bone material or other human

tissue, teeth do not re-model or mineralize any further after the teeth are fully formed. Once

completely formed, teeth act as an archive that stores information from during the formation,

which makes them highly useful for research to an individual’s place of origin and migration

patterns towards the place where the human remains are found after death. Especially tooth

enamel is useful for the investigation of one’s residence during the early years of life, because

this is exactly when the enamel stores its information, during childhood (Evans & Tatham,

2004, p.238; Montgomery, 2002, p.46). To be able to find out which teeth and what part of

the teeth it is exactly that can be used best in this research, some information must be given

explaining the formation of teeth, what they consist of and when the different teeth erupt

through the jaws.

~ 18 ~

First of all, human teeth consist of a set of deciduous teeth which appear rapidly after being

born. After that, humans get a set of permanent teeth that replaces the deciduous teeth during

childhood. In most archaeological cases dealing with tooth evidence, one is dealing with the

permanent teeth, as they form the teeth of one’s mouth during most of his or her life. Since

the teeth from the Bradford Peverell skeletons that are used in this particular case study only

consist of permanent teeth, the theoretical part on the deciduous teeth will not be mentioned

and this chapter will therefore solely focus on the permanent teeth. In the chapter on the

archaeological background information, it was mentioned that in burial 5 there was a mixture

present of both deciduous and permanent teeth; however, none of the deciduous teeth were

used in this study.

In order to be able to interpret the results given later in this paper, understanding of the teeth

is essential. This will also help the understanding of the use of strontium stable isotope

analysis used to find information on mobility, when information is given about the uptake of

strontium in the tooth enamel and why enamel is resistant to contamination after being buried

in the soil, thus making it very useful as analyzing material.

4.1 FORMATION OF THE TEETH

During human life, two series of teeth are formed: the deciduous teeth, often referred to as

milk teeth, and the permanent teeth, that start replacing the milk teeth during childhood at

about 6 years old, continuing until the age of 14 (Pye, 2004, p.215). Normally a set of

deciduous teeth holds 20 teeth whereas the permanent dentition consists of a total of 32. As

mentioned earlier, the time in which the permanent dentition is formed is critical in this

archaeological case. It is during the formation of the teeth, with the enamel in particular, that

strontium is stored within the teeth, becoming incorporated during mineralization of the

enamel where strontium often takes the place of calcium, being similar in its characteristics as

mentioned in the previous chapter on strontium. This is why a dental development table is

used, as can be seen in table 1, where the formation of each tooth, formed during a certain

stage of childhood, is mentioned separately (Montgomery, 2002, p.51). Because in this

particular case study only permanent teeth were dealt with, as mentioned earlier, the next part

of this chapter will go further into the formation of the permanent dentition.

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4.1.1 Formation and eruption of the permanent teeth

In the set of permanent teeth, the formation starts with the first molar around 28-32 weeks of

pregnancy. Following the first molar is the first incisor, which is formed just after birth. By

about 8 years of age, all of the crowns of the permanent teeth, apart from the third molars, are

formed including the tooth enamel (Pye, 2004, p.216). After formation, the eruption of the

permanent dentition starts as early as the age of five years and usually all of the permanent

teeth, apart from the third molars or wisdom teeth, are erupted by the age of thirteen. The

eruption of the teeth takes place after the crowns of the teeth are fully formed. By this time,

the crowns are also mineralized; however the roots of the teeth are not yet fully completed.

The order in which the teeth erupt in most cases is as follows: it starts with the first molars,

followed by the first incisors, the second incisors, the upper first premolar and the lower

canine, the lower first premolar and the upper canine, then the second premolars, the second

molars and finally the third molars. The sequence of tooth eruption might change slightly

within different populations and sexes, but this is considered the most common order in which

the permanent dentition erupts.

Table 1. Timing of formation of permanent dentition in years

Source: Gustafson and Koch 1974, adapted from: Montgomery 2002, p.52

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In the table made by Gustafson and Koch, 1974 (adapted from: Montgomery, 2002, p.52), a

full record on the formation and eruption of the permanent teeth can be found, explained in a

clear and easy to understand overview. The fact that these data show ranges instead of a single

date relies on the idea that these ranges cover the variations in tooth formation and eruption

present within a population. Therefore one has to bear in mind when using these data that they

do not represent an exact date when a particular tooth is formed, but are merely based on the

idea that when a child’s tooth is formed early, this tooth is very likely to be fully formed and

erupted at an early age as well. As mentioned before, tooth formation times vary within a

group of people and are often also depending on gender.

In this study, the primary purpose of using the information on the formation of the permanent

dentition is the fact that the time of mineralization of the enamel is very important in order to

be able to decide which teeth will be used for the stable isotope analysis, which is depending

on the period during childhood when the enamel was formed, relying on the idea of the uptake

of strontium in the enamel during mineralization. With the information gained from the

enamel it can be decided which teeth form the focus of interest in this research.

4.1.2 Formation of the enamel

Enamel present in human teeth is formed during the early years of childhood (Price &

Gestsdóttir, 2006, p.132). Explaining the way tooth enamel is formed is a difficult matter as

this remains a mystery to many researchers. Common thinking has led people to believe that

teeth are formed ‘from the top to the bottom’, meaning that the outside enamel cap is formed

first before the dentine is created followed by the roots leading to the end of the tooth

formation. However, according to Janet Montgomery, this way of thinking is very simplified

and insufficient as it tends to ignore the complicated mechanisms that coincide with the

formation of enamel and the tooth dentine. Because the formation of enamel demands a lot of

time to be fully understood and analyzed, and this is not of particularly big influence to this

investigation, explaining the formation of enamel will be kept rather simple in this chapter in

order to understand the basics, so that one can understand why tooth enamel plays such an

important role in the study of stable isotope analysis when analyzing mobility. For more in-

depth information on the formation of enamel, see Montgomery, 2002, chapter 3.4.

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Enamel grows in layers that are in a way comparable to tree rings. Dark and light bands are

visible when a cross section is made and according to Hillson (1996, a pair of one dark and

one light band forms the growth during 24 hours. Of all the materials present in the teeth,

enamel is the hardest of all and is highly mineralized. Another material present in the teeth is

dentine, a softer material which forms the base of the roots and the crown on which the

enamel cap is formed. The enamel cap is usually the part of the teeth that is visible in one’s

mouth. Both enamel and dentine consist of inorganic and organic material and also contain

water. However, both tissues vary greatly in composition. Enamel is mostly made from

inorganic material, about 95% of the enamel, with 4% of water and 1% of organic material,

whereas dentine consists of 70% of inorganic material, 12% of water and 18% of organic

material (Pye, 2004, p.216; Evans & Tatham, 2004, p.238; See also Montgomery, 2002, p.57).

Enamel and dentine are formed by cells while making use of a blood supply. Once the enamel

is formed, the cells present in the enamel die and the blood supply stops which starts the

mineralization process. This is why once enamel is formed and mineralized, basically no

changes can occur which makes the tissue highly resistant to any remodeling or re-

mineralization, but also resistant to diagenesis (Kyle, 1986, p.410) and other post-mortem

changes occurring after deposition (Pye, 2004, p.216; Price & Gestsdóttir, 2006, p.132). Also

when enamel is chipped off the tooth, it is incapable of growing back (Montgomery, 2002,

p.75).

Dentine on the other hand can more or less be compared to bone, since just like bone material

it contains collagen. As mentioned before, dentine consists of more organic material than

enamel, and is a tissue constantly fed by a blood supply. This fact is why dentine can be seen

as a living tissue built from cells. Even though most of the dentine tissue contains information

from during the formation of the tissue, its living cells form the so called secondary dentine,

which is capable of adapting itself to its surrounding environment (Montgomery, 2002, p.58).

This means for instance that when a person has a certain diet, then moves to another place and

changes their diet, the concentration of chemicals in the dentine changes with it. This is why

dentine is considered not very useful for this investigation, because it adapts itself to the soil

where the individual was buried in, therefore showing only signs of the local area and

showing nothing of movement.

~ 22 ~

4.2 STRONTIUM IN HUMAN TOOTH ANALYSIS

During mineralization of the enamel and the primary dentine, strontium is absorbed into these

tissues. The amount of strontium that occurs in the enamel and dentine represents the amount

that was ingested during mineralization. This can be traced back since enamel and primary

dentine have the characteristic of not being remodeled or reformed after mineralization,

therefore keeping the information on strontium ingested during a certain period of life safe

(Evans & Tatham, 2004, p.238). This characteristic is very useful in archaeological cases

where one often deals with an individual buried in the soil, where it is open to contamination

by everything present in that soil. The amount of strontium present in the soil could be very

different from the amount ingested during childhood, so if the enamel was capable of taking

up new strontium, stable isotope analysis would not prove much.

With this information and that given in the previous sections, it is proven that enamel seems

to form a good fundament for this study in order to find information on human movement

during the formation of the enamel, and has been a good indicator of strontium levels in

previous studies (Price & Gestsdóttir, 2006, p.132). One thing one has to bear in mind when

taking enamel samples to be used for strontium stable isotope analysis is, that these samples

must consist solely of core enamel, therefore getting rid of the surface enamel and any dentine

present on the tooth, since especially the dentine is prone to adapting to the soil in which the

tooth was buried (Bentley, 2006, p.167; Montgomery, 2002, p.75).

~ 23 ~

CHAPTER FIVE

METHODOLOGY

5.1 THE SAMPLES USED IN THIS STUDY

The samples that were used in this particular study consisted of the first permanent molar on

the right side of the mandible of six individuals. The first permanent molar was used because

this is the first permanent tooth to erupt, as can be read in chapter 3, and therefore holds the

earliest Strontium information in the enamel when the deciduous teeth are not present. The

reason why deciduous teeth were not used in this case study is because there were none, since

the individuals dealt with in this investigation are all believed to be older than six years of age

(Auton, 2010). Also, by using the right mandibular first permanent molar, it is ensured that

this study is indeed dealing with six different individuals, whereas with the use of different

teeth, one can never be completely sure of having six different individuals.

5.1.1 Sample selection

The first step that was taken in this research was collecting the tooth material present with

every skeleton. These teeth were carefully recorded for every individual and washed with the

use of water and a toothbrush in order to get rid of most of the soil. After having recorded all

the teeth, six individuals of whom the most teeth were thought to be present, were selected. Of

these individuals, the right mandibular first permanent molar was taken for further

investigation. The first permanent molar is used in this study because it is the only tooth that

forms its enamel during the very early childhood and even before that (Price & Gestsdóttir,

2006, p.133). The tooth samples were selected by using the diagrams of the right mandibular

first molar present in Van Beek, 1983, to compare with the teeth from the skeletal remains

found at Bradford Peverell (see figure 6). By looking at the amount of cusps present on the

teeth and the shape of the teeth, the right first molars could be selected.

~ 24 ~

Fig. 6 Diagram of the mandibular right first permanent molar (van Beek, 1983, p.83)

In order to make sure the right teeth were selected for this study, help was offered by Dr. M.J.

Smith who is working as an anthropologist at Bournemouth University.

5.1.2 Tooth sample preparation

The most important thing that had to be considered when preparing the tooth samples was the

issue of contamination. Strontium ratios in enamel tend to adjust themselves to the amount of

strontium present in the atmosphere when being exposed to it, next to the amount of strontium

ingested through one’s diet. Therefore it was very important to work in the right environment,

using clean tools and acid-leached Teflon beakers (Evans & Tatham, 2004, p.241), while

working in a laboratory in which the air was constantly filtered. Also, in between the different

stages of sample preparation, all the tools and beakers were cleaned or when necessary,

replaced with new ones. Another thing that must be stressed is that all of the work was done

and performed by the author of this paper unless stated otherwise.

This research was conducted in the Oceanographic Centre in Southampton under the

instructions given by Dr. Matt Cooper. Therefore, the methods used for the preparation and

stable isotope analysis of the tooth samples were adapted to the methods used in this centre.

The first step taken after the teeth were moved from the human bone lab at Bournemouth

University to the centre in Southampton, was to place them in an ultrasonic bath for 30

minutes (Montgomery, 2000, p.374; Evans & Tatham, 2004, p.241; See also: Beard &

Johnson, 2000, p.1053). This was done in order to remove the surface contamination and bits

of soil still present on the teeth. During these 30 minutes of cleaning, the process was

~ 25 ~

interrupted every 10 minutes in which the specimens were each cleaned mechanically using a

toothbrush and ultra pure water (at 18.2M) (Knudson, 2004, p.10). After this step, the

samples were dried in the oven overnight at a temperature of 60 ˚C.

Having cleaned the teeth, they were cut down in pieces by the use of a scalpel and a hammer

so that the enamel could be separated from the dentine using a scalpel to scrape it off. This

way, samples of at least 20 mg of enamel were extracted from the teeth of which the small

bits of dentine still present on the samples after the use of the scalpel, were removed

mechanically with the use of a dremel tool (Price & Gestsdóttir, 2006, p.133). After this step,

the samples were again placed in an ultra sonic bath for 20 minutes and rinsed afterwards by

using ultra pure water.

The next step in cleaning the tooth samples involved removing diagenetic strontium. In order

to do this, the samples were leached in 2 ml of a 5% HNO3 acetic acid solution overnight

(Price et al., 1994, p. 321; Beard & Johnson, 2000, p.1053; Knudson et al., 2004, p.10). The

next day, the samples were rinsed four times using ultra pure water and were dried in the oven

at 60 ˚C. After the samples were dried the last step was taken, which involved the dissolving

of the tooth enamel samples. This was done on a hotplate in a solution of 300 µl 3M HNO 3

and 6M HNO3. After having dissolved the samples in these chemicals, 300 µl of ultra pure

water was added to end with a solution of 600 µl 3M HNO3.

5.2 PREPARATION OF THE STRONTIUM COLUMNS

With all the tooth samples cleaned and ready to be used, strontium columns now had to be

prepared. In order to make the strontium columns, cleaned Sr resin had to be prepared with

which the strontium could be extracted from the tooth enamel samples by ion-exchange

(Montgomery et al., 2005, p.127). The preparation of the Sr resin was done by taking a bottle,

transferring the dry resin into the bottle and adding ELGA water after which it was shaken

and allowed to settle. The water that was visible on top of the resin was then taken off and the

procedure was repeated several times. Finally, the resin was soaked in ELGA water for at

least 24 hours before use.

While the resin was soaking and settling down, the columns in which the resin would be

inserted were taken out of the box in which they were stored, containing an acid bath of 10%

~ 26 ~

HNO3. The reason why the Teflon columns were stored in this acid was to prevent

contamination. Next the columns were carefully rinsed with ultra pure water, after which they

were placed in a plastic rack with plastic pots underneath every column in order to catch the

fluids coming out of the columns. After setting everything up, the columns were then filled

with water. To make sure the water runs through the columns, they were squeezed gently.

The next step involved getting the strontium resin into the columns. This was done by using a

clean pipette which was then put in the bottle holding the prepared resin. A small amount was

sucked up in the pipette and released in the column which was still filled with water. This

method was used to be able to get the resin in the right place of the column, filling it up until

just after the small tube, into the neck of the column (See figure 7). Doing this while water

was still running through the columns made sure that the small tube of the column got filled

completely with the resin without the presence of air bubbles.

With the resin settled down in the column, the column had to be cleaned so that contamination

could be prevented as much as possible. In order to do this, a number of steps were followed.

The first step was running 1.5ml of water (H2O) through every column. To make sure the

amounts of water running through the columns were the same in every one of them, use was

made of a volumetric pipette that could be set manually to a specific volume, allowing the

amount of liquid taken up to be measured accurately. After cleaning the columns with water,

again 1,5 ml was run through the columns, this time of 3M HNO3, a chemical prepared by

Matt Cooper out of sub boiled acid. The cleaning of the columns with the use of water and the

acid was then repeated once.

Fig. 7 Strontium column showing the level of the Sr resin.

(Obtained from Matt Cooper, 2010, pers. comm.)

~ 27 ~

5.3 COLLECTION OF STRONTIUM AND TIMS ANALYSIS

The clean columns containing the Sr resin had then to be loaded with the tooth sample

solutions that were prepared earlier, as mentioned in the previous section of this chapter. To

the solution 200 µl 3M HNO3 was added, before it was taken out of the Teflon vial with the

use of a pipette and loaded onto the column. While doing so, the numbers on the vials were

carefully noted so that later on one would be able to trace the sample numbers back to the

columns. Having loaded all the six samples each in a different Sr column, 200µl 3M HNO 3

was run through the columns to wash the columns with the samples in. This step was

repeated, this time with 2,5 ml 3M HNO3, in order to elute the columns after which the

strontium could be collected.

After having eluted the strontium columns, the plastic cups, that had been collecting the fluids

running through the columns so far, were replaced by clean savillex vials, each with

individual letters written on them in order to keep them apart. Then 1,5ml of water (H 2O) was

run through the columns in order to collect the Sr from the resin. The samples were then dried

out on the hotplate so that all the water would evaporate and only the pure Strontium would

be left over in the vials. In the mean time, while the samples were drying out, the Sr resin was

washed out of the columns, after which they were rinsed with water and returned to their

acidic bath and stored for their next use.

Having the Strontium samples fully prepared, it was time for the next step: the preparation of

the filaments on which the sample would be loaded before placing them in the Thermal

Ionization Mass Spectrometry machine (Montgomery, 2000, p.374; Evans & Tatham, 2004,

p.241). The filaments were made of a metal holder, already present at the National

Oceanographic Centre, on which a piece of tantalum (Ta) strip was welded (Price &

Gestsdóttir, 2006, p.133), again stressing that all of this was done by the author of this paper.

The metal piece with the tantalum strip was set in a socket, after which the dried down

strontium samples were collected. Following this, a drop of Ta-activator was released onto the

strontium samples. The sample was then taken up with the use of a pipette and released on the

filament. While turning up the voltage of the battery that was connected to the socket, the

activator was dried down. When the same was done for all six samples, they were now ready

to be loaded into the mass spectrometer to be run in order to get the results. This last step of

~ 28 ~

running the machine was done by Matt Cooper since the machine was not available straight

away. Through personal contact, the results of the mass spectrometer were obtained.

The strontium ratios found were all measured with a precision of approximately 0.000011

2SE (standard error) or less, with the exception of one result that came in with a precision of

0.00003 SE. After the result came in, they were compared to the strontium ratio reflecting the

local area, of Bradford Peverell, in which the burials were found. This was done in order to

see if there were large differences. Full analysis and discussion of the results will be

mentioned in the next chapters.

~ 29 ~

CHAPTER SIX

RESULTS

The strontium ratios found after conducting the stable isotope analysis range from 0.708287

to 0.712039 (See table 2). The standard errors in the isotope ratios were considerably small

and are encompassed by the symbols presented in the diagram. Looking at these results with

the dashed line showing the average strontium ratio value of the geological area in which the

human remains were found, it appears that 3 out of the 6 samples taken seem to be close to

the value of the local geological area. However, three values really seem to stand out. In the

case of these values, there appears to be no correlation between the strontium ratios and the

surrounding soil in which the remains were initially found. This means that these results

might show that not all the individuals sampled in this study appear to be local to the area in

which they were buried after they died. This will be further analyzed and discussed in the next

chapter. A full overview of the results found, is presented in table 2.

Table 2. An overview of the results found in the tooth enamel

Burial Number Amount of tooth enamel sampled (mg)

87Sr/86Sr ratio found through TIMS± 2SE (Standard Error)

1 38.7 0.708963 ±2SE 0.0000114 25.9 0.708449 ±2SE 0.0000305 47.6 0.712039 ±2SE 0.00001112 26.5 0.710895 ±2SE 0.00000917 40.6 0.709817 ±2SE 0.00001118 29.1 0.708287 ±2SE 0.000011

~ 30 ~

~ 31 ~

Fig. 8 Plot of 87Sr/86Sr ratios found in the tooth enamel

CHAPTER SEVEN

DISCUSSION OF THE RESULTS

7.1 DIAGENESIS

The human remains that were found at Frome View were fair to poorly preserved. This makes

it possible that the tooth enamel of each sample used in this study might be affected by post-

mortem diagenesis. This could be a reason for some of the samples to show a similar Sr ratio

in the results, close to the known Sr ratio of the surrounding burial soil. However, in the most

ideal circumstances when the enamel is fully mineralized, the event of diagenesis entering the

tooth enamel does not have to occur. The teeth used in this study appeared to have been well

preserved and in order to prevent diagenesis to interfere with the Sr results, a technique was

used during the investigation in which the teeth were leached in delute acid (Bentley, 2006,

p.164; Price et al., 1992, p. 519) in order to remove the diagenetic strontium. This is proven to

be an effective technique, taking away only the diagenetic strontium without losing the

strontium present in the mineralized tooth enamel (Montgomery, 2000, p.373).

In three out of six samples, there is no correlation with the Sr ratio found in the enamel

samples and the average Sr value present in the surrounding burial soil as found on the

geological map that shows the strontium ratios present in the UK (Appendix; See also: Evans

et al., 2010). This suggests that the surrounding, in which the human remains of burial 5, 12

and 17 were found, had no influence on the Sr ratios found in the tooth enamel of these

individuals. This shows that because of the amount of strontium found in the enamel samples

is higher than the amount found in the burial soil, the strontium present in the enamel samples

must either have consisted of a lot more radiogenic strontium (i.e. 87Sr), which appears to be

highly unlikely, or little diagenetic strontium was able to enter the mineralized enamel. The

latter seems a very reasonable option.

In the case of enamel, poor preservation of the teeth does not necessarily mean that there is a

loss of strontium that was ingested during the mineralization of the teeth and also does not

mean per definition that there is a higher chance of diagenetic strontium entering the tooth

~ 32 ~

enamel. However, the idea of diagenetic incorporation is necessary to be considered,

especially in the results that show a Sr ratio found in the enamel that is very close to that of

the surrounding burial soil, but also when tooth enamel is used that has not fully mineralized

thus diagenetic Sr is able to enter the enamel.

7.2 THE STRONTIUM DATA

Of all the results found in this study and presented in the previous chapter, the outcomes of

burial 5, 12 and 17 fall outside of the group of results around the average strontium value of

the surrounding burial soil from the location where the human remains were all found. This

shows that these individuals ingested a different amount of strontium than the other ones,

which could mean that they had a different diet and drank water with a different amount of

strontium in it during their childhood because tooth enamel gives the opportunity to make a

direct comparison of the diets of the individuals during the time of mineralization

(Montgomery et al., 2005, 131). Because of the results that came out of this investigation, it is

safe to say that the results range over a wide area and that it is therefore unlikely that the

individuals found at Frome View all came from one local population, in which natural

variations in strontium ratios occur, because these variations are considerably large.

Three out of six results fall in the local range of the average strontium value present in the

area of the burials, not showing a larger difference to this value than 0.0005. The individuals

from burials 1, 4 and 18 might therefore be from Britain and even from the local origin

whereas the human remains found in the burials 5, 12 and 17 could be from a different area

within Britain or even from outside the UK. It could also be that the sample taken was too

small to give really reliable results however, table 1 presented in the results section shows that

all the samples taken were considerably higher than the minimum of 20mg that had to be used

and also, there appears to be no correlation between the amount of enamel sampled in this

study and the outcomes of the strontium ratios.

Another reason for the results that appear to be “non-local” has to do with the diet the

individuals had during their childhood. It might for instance have been the case that one could

not always eat meat, which is relatively low in strontium, and had to search for other

resources like greens and other plants which hold more radiogenic strontium. One thing that is

mentioned in Montgomery et al., 2005, is the possibility of importing food from a different

~ 33 ~

region. This is an important thing to keep in mind as this might be resulting in strontium

isotope ratios showing a non-local signature whereas they actually could be of local origin.

If the three individuals showing a different strontium ratio are indeed of a different place of

origin, the next question involves where the individuals came from and if it was just a case of

spending their childhood in a different geological area and spending the rest of their lives in

the area where they were buried in the end or whether there was indeed a real migration.

Because in this case it is not known what the exact diet of the individuals was, one rule given

by Douglas Price and Hildur Gestsdóttir was adapted in order to analyse the results:

“If the enamel ratios are similar to the local ratio then the individual probably did not move. If the enamel ratio is distinct from the local ratio, this individual must have moved to the place of death from a geological distinct homeland.” (Price & Gestsdóttir, 2006, p.132; See also: Bentley et al., 2003, p.474)

This means that in this research, it has come to light that three out of six individuals have

probably moved from one place, in which they spent their childhood at the time of enamel

mineralization, to another place, the place in which their remains were found.

Comparing the three outstanding strontium ratios with the geological map of strontium

biospheres in the UK, as seen in appendix , three different colours correspond with each of the

individuals. Burial 5, with a strontium ratio of 0.712039 , shows a value that falls in the

orange range on the map, burial 12, having a ratio value of 0.710895, corresponds with the

light green colour of the map and burial 17 with its strontium ratio of 0.709817 , can be traced

back to the dark green areas on the map. The area in which the human remains were found are

shown on the map with the use of a purple arrow and are measured in, according the

coordinates of Mr. Hawthorne’s house in Bradford Peverell. Looking at the arrow, one can

see that the place, in which the burials were found, lies clearly in the light blue area on the

map, showing enough light blue space around it to be sure not to confuse this with a different

colour.

Knowing that the average Sr ratio of the burial soil is 0.7085, derived from the light blue class

which is 0.708-0.709, one can see that especially the strontium ratio values found for burial 5

and 12 are showing a great difference from this class, which means that they could not have

come from the local area or from an area directly adjacent to the local area. The question as to

~ 34 ~

where the individuals exactly came from, the provenance, is unfortunately not easy to answer

as it was shown in the introduction that the background and the migration patterns of the

Anglo-Saxon population is uncertain and relies on a lot of historical, but also very subjective,

sources. For this investigation, it can only be said that the individuals are likely to be non-

local which can be shown by the strontium ratios present on the map.

7.3 ARCHAEOLOGICAL EVIDENCE TO INDICATE MIGRATION

In the previous section, it is shown that there is a difference in dietary pattern, presented

through great variation in the found Sr ratios, and therefore one might be dealing with non-

local people. However, solely based on the difference in strontium values, one cannot

conclude that there are indeed non-locals among the burials found in Frome View. In order to

justify this statement, a comparison is made between the burial numbers and their strontium

value, and the grave goods found during excavation and other characteristics of the grave.

7.3.1 Burial 5

From the strontium ratios found, burial 5 shows the highest with a value of 0.712039.

Looking at the information given in the chapter on archaeological background information,

this grave held the remains of a young female, aged between 6 and 12 years old by

anthropological investigation. The objects found in the grave show a variety of goods: various

beads that might have formed a necklace, two silver disks, a bronze disk, a buckle made of

bronze and two coins. On its own, the buckle, the coins and the disks don’t have to mean

anything and don’t necessarily show a different place of origin, unless there is information

present on the coins and can be traced back. The beads on the other hand, show some

interesting features as two of the beads appear to be made from gold material which is a

precious possession for a young female believed to be aged between 6 and 12 years. This

could mean that the female is of higher status and/or not from around the local area. However,

more investigation on Anglo-Saxon grave goods needs to be done in order to find out where

exactly the individual came from.

~ 35 ~

7.3.2 Burial 12

From the human remains found in burial 12, a strontium ratio was found with a value of

0.710895. In this grave a knife was found at the head end of the grave. This is interesting

because in all other graves where a knife was found, it was found at either side of the body,

but never at the head end. Mr. Keen, the archaeologist of this project, has mentioned the

possibility of it being an indication that the person buried in this grave could have been a

slave. That thought is very fascinating because the remains found in burial 12, show that of a

male individual of adult age however, quite short as the grave outline has a length of only 4

foot 8 inches long. Even though one cannot say this for sure, but these features together with

the knife found at the head end, could imply that the individual is of non-local origin.

7.3.3 Burial 17

According to the anthropological research, in burial 17 the remains of a robust, tall adult male

were found. Remarkably, in this grave, no grave goods were found and it does not seem that

there was any room for objects as the grave cut appears to be narrow, just fitting around the

human remains. This information does not prove that the individual found in burial 17 was

indeed a migrant, but it does show that this grave is interesting and needs more investigation

in order to find out more about the origin of the human remains.

7.4 LIMITATIONS OF THIS STUDY

During this investigation, a number of limitations were present that influenced the route this

study has taken, but also the results that came out of it. The limitations started with the human

remains from Frome View. The human remains were excavated over the past 33 years by Mr.

Keen and Mr. Hawthorne, all paid out of their own expenses and executed in their own spare

time. Having money and time as a limitation, this caused the investigation to take such a long

time, but also limited the way in which everything was documented, next to the fact that 33

years ago the ways in which archaeological excavations were documented was a lot more

limited and different than it is done nowadays. This is especially seen in the fact that the

stratigraphic context of the burials was lost by the time this study was conducted and therefore

solely relied on pictures taken during the excavations, the personal communication with Mr.

Hawthorne and Mr. Keen themselves and on the human remains that were brought to

Bournemouth University.

~ 36 ~

The next limitation of this study was the accessibility of the grave goods. Because the

archaeological investigation was already finished a while before the stable isotope analysis

took place, there was only access to the human remains and to some pictures taken of the

excavation process and of the grave goods themselves. However, there was no chance of

actually seeing the grave goods which made interpretation of the graves together with the

strontium isotope results more difficult.

When it comes to the strontium stable isotope analysis itself, there were a lot of limitations as

well. The most important ones include time and money. Preparation of the samples and the

isotope analysis itself were quite difficult, very time consuming, and also expensive (Budd et

al., 2004, p.139). The fact that the strontium isotope analysis is so expensive reflected in the

amount of samples that were taken during this study, which resulted in only one sample per

individual taken and also the small number of only six selected individuals. This is also why

this research in solely focused on strontium stable isotope analysis instead of combining this

with for instance oxygen isotope analysis in order to get more reliable results (Pye, 2004,

p.223).

Finally, there was the limitation of not having the right facilities at Bournemouth University

and therefore having to make use of the facilities at the National Oceanographic Centre in

Southampton which made things more expensive as well. With these limitations, one can see

that there is definitely room for improvement which will be discussed in the chapter on further

recommendations.

~ 37 ~

CHAPTER EIGHT

CONCLUSIONS

The aim of this case study was to investigate six individuals found at Frome View, Bradford

Peverell in order to find out whether they were local or non-local to the area in which they

were buried. This was done by performing strontium stable isotope analysis on the right

mandibular first molar of those selected individuals. The results that came out of the isotope

analysis clearly produced two groups: One group consisting of three individuals with a

strontium ratio that is close to the average ratio of the burial soil in which the remains were

found, and one group showing Sr ratios with a great difference from the average Sr value.

The group of three ratios that differ from the average strontium ratio consist of the remains of

a young female found in burial 5, the remains of an unusually short adult male, found in burial

12 and the robust, large remains of an adult male who was excavated from burial 17.

Unfortunately of none of these individuals can be stated what their provenance is or can it be

concluded that they are 100% non-local as food could have been imported into the area.

However, it can be stated that together with the evidence obtained from the information on the

burials and the objects found in them, these individuals are very likely to be of non-local

origin.

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CHAPTER NINE

FURTHER RECOMMENDATIONS

In this study, it has come to light that there is much that can still be done to improve the use of

strontium stable isotope analysis. As mentioned in the limitations money and time have

played a great role in this study. Therefore, some recommendations must be given in order to

overcome these limitations and to take this investigation a step further. First of all, this study

only investigated strontium stable isotopes. Recommended would be that further investigation

on these individuals will be done in the future in order to obtain more information on their

provenance. This could be done by performing oxygen stable isotope analysis on them, so that

these results could back up the results found in this study, which has been proven to be useful

in an article by Evans et al., 2006.

Secondly, the strontium isotope analysis used in this study has proven to be technically

difficult and also destructive on the teeth. In the future it would be nice if a method could be

developed which will use smaller samples of tooth enamel, but it still proven to be just as

effective so that the damage done to the archaeological material will be kept to a minimum.

Also, the use of strontium stable isotope analysis could be of interest of not only buried

archaeological remains but maybe also applying them on cremated remains and in forensic

cases. This is something that one is trying to do. In forensic cases, contamination plays a huge

role, thus one has to be very careful. However, dealing with a forensic and therefore recent

case, diagenesis of strontium is less likely to occur and the results might therefore be more

reliable and very useful when it comes to personal identification. Studies that have been done

in relation to forensics, can be seen in: Pye, 2004 and Montgomery et al., 2006. Further

investigation into this might show that strontium stable isotope analysis appears to be very

useful.

Finally there is the problem of diagenetic strontium present in archaeological bone and tooth

material. Research must be done in order to find an effective method to get rid of the

diagenetic strontium. In tooth material, acid leaching has been used, however this does not

~ 39 ~

seem to be an option for bone material. If in the future a good method will be developed in

order to remove the diagenetic strontium present in skeletal material, the strontium results will

be a lot more reliable.

~ 40 ~

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APPENDIX I

Burial pictures, received from Mr. J. Hawthorne through personal communication.

BURIAL 1 BURIAL 2

BURIAL 3 BURIAL 4

BURIAL 5 BURIAL 6

~ I ~

BURIAL 7 BURIAL 8

BURIAL 9 BURIAL 10

BURIAL 11 (RIGHT) AND 12 (LEFT) BURIAL 13

BURIAL 15 BURIAL 16

BURIAL 17

BURIAL 18

APPENDIX II

Overview of the burials found at Frome View

(Adapted from Mr. Hawthorne & Mr. Keen, 2010, pers. comm.)

~ II ~

APPENDIX III

Map of Britain showing the geology of the burial location

(Adapted from British Geological Survey, 2010)

~ III ~

Burial location

Cretaceous

Jurassic

APPENDIX IV

~ IV ~

Map of Britain showing the strontium ratios present in the biosphere

(J. Evans, 2010, pers. comm.)