Journal of the North Atlantic
T.D. Price
2015 Special Volume 7
71
Introduction
A Scottish chemist, Frederick Soddy, coined the
term “isotope” in 1912. He observed what now defines
an isotope—that the number of protons in the
atomic nucleus determines the chemical properties
and identity of an element, but there can be different
numbers of neutrons associated with the same
number of protons, resulting in the same element
having several variations with different weights (or
masses). These different structural formations of an
element are its isotopes. The beginnings of isotopic
applications in archaeology probably dates to the
mid-1960s with the analysis of lead isotopes in ancient
metals and slags by Brill and Wampler (1965).
Today the use of isotopes in archaeological
chemistry is widespread and rapidly growing, with
many kinds of applications. Various isotopes are
analyzed in different kinds of materials to answer a
variety of questions about the past. Isotopes of oxygen,
carbon, nitrogen, lead, and strontium isotopes
are commonly used in archaeological applications.
For the study of human remains, these isotopes are
important because they get into our bodies through
the food we eat and the water we drink and are deposited
in measurable amounts in our skeleton.
Interest in the isotope chemistry of human skeletal
remains began in the late 1970s as a spinoff from
radiocarbon dating (e.g., Bender et al. 1981, Tauber
1981, Vogel and van der Merwe 1977). The isotopic
analysis of human skeletal remains generally
involves two types of questions: concerning either
past diet or human provenience. Isotopic studies of
ancient human remains began in almost 40 years
ago with the recognition that different diets produced
different carbon isotope ratios in the tissues
of animals (e.g., DeNiro and Epstein 1978). Almost
simultaneously there was a recognition that different
pathways of photosynthesis produced different
ratios of 13C/12C in plants (O’Leary 1981, Smith and
Epstein 1971). This information was soon applied to
the study of the spread of corn from its homeland in
Mexico to North America (Bender et al. 1981, Vogel
and van der Merwe 1977). Around the same time,
the impact of marine foods on carbon isotope ratios
in human tissue was reported in seminal papers by
Tauber (1981) and Chisholm et al. (1982).
The isotopic investigation of human provenience
began in the mid-1980s with both practical and
theoretic publications. Krueger (1985) measured
strontium isotope ratios in a series of human and
animal samples from the Maya region in Central
America and reported significant geographic differences.
That same year Ericson (1985) proposed
the application of strontium isotopes to questions
concerned with place of origin. The method slowly
gained attention with an important dissertation published
in South Africa (Sealy 1989) and papers by
Price et al. (1994a, 1994b) concerned with place-oforigin
studies in early Bronze Age Europe and the
prehistoric southwestern US.
Both questions—past diet and place of origin—
are of interest in the investigation of the Norse colonization
of the Atlantic. Such studies involve both
the light isotopes of carbon, nitrogen, and oxygen,
and the heavy isotopes of strontium and lead. Each
of these isotopic methods will be introduced and
described in some detail below. In addition, there are
two primary types of tissues that have been used in
such studies: bone and tooth enamel. These tissues
are considered below prior to a discussion of the
isotopic methods. A brief summary of sample preparation
and measurement for these isotopic methods
is provided in Appendix 1.
An Introduction to the Isotopic Studies of Ancient Human Remains
T. Douglas Price*
Abstract - This paper provides an introduction to methods in archaeology that utilize light isotopes for helping to determine
diet and heavier isotopes for information on mobility and provenience of specimens. The common isotopic systems of carbon,
nitrogen, oxygen, strontium, and lead are described in terms of basic principles, specifically with references of human
bone and tooth enamel. Isotopic analyses of carbon and nitrogen in collagen for past diet provides information on certain
food types (e.g., C4 plants, marine resources, freshwater fish) and trophic level, while the analysis of oxygen, strontium,
and lead can provide information on local vs. non-local origins, mobility, and place of origin. Analysis of tooth enamel
provides information on childhood contexts, and the analysis of adult bone provides information on the later years of life.
This paper is intended to provide the methodological background for the isotopic analysis of human and faunal materials
from the Viking colonization of the North Atlantic.
Viking Settlers of the North Atlantic: An Isotopic Approach
Journal of the North Atlantic
*Laboratory for Archaeological Chemistry, University of Wisconsin-Madison, Madison, WI, USA 53706; tdprice@wisc.edu.
2015 Special Volume 7:71–87
Journal of the North Atlantic
T.D. Price
2015 Special Volume 7
72
Tooth Enamel and Bone
Bone and tooth enamel incorporate chemical
signals from different periods in an individual’s life.
Bone is a relatively plastic material, containing both
an organic (mostly collagen) and inorganic (mostly
the mineral hydroxyapatite) phase. Collagen is the
major structural protein in bone, and also forms the
molecular cables that strengthen the tendons and
vast, tough sheets of tissue that support the skin and
internal organs. Because bone is a dynamic material,
it is constantly changing and remodeling, adding
new material and losing old. Thus, the chemical
composition of bone reflects the chemistry of diet
and place of residence of the later years of life.
Enamel, on the other hand, forms during early
childhood and is constructed from nutrients eaten
by the mother and the young child (Hillson 2005).
Calcification of the enamel crown of most of the
permanent teeth (with the exception of M3) is normally
completed by the age of six (AlQahtani et al.
2010, ElNesr and Avery 1994, Ten Cate 1998). Formation
time for the permanent teeth (except M3) is
shown in Figure 1. M3 begins forming between the
ages of 8–10, and the crown of the tooth is complete
between 12–16 years of age in most individuals. Because
tooth enamel, composed primarily of the mineral
hydroxyapatite, does not change during one’s
lifetime, it retains the chemistry of the place of birth
and childhood (Ericson 1985, Krueger 1985, Price
et al. 1994b). A variety of studies have demonstrated
that enamel is highly resistant to post-mortem contamination
(e.g., Budd et al. 2000, Hoppe et al. 2003,
Kohn et al. 1999, Lee-Thorp and Sponheimer 2003).
Because of these differences in tissue formation
and the inert nature of enamel, we have available in
human skeletal remains the means to examine some
of the conditions in the life history of a single individual
(e.g., Sealy et al. 1995).
Studies of paleodiet have focused primarily on
bone, and specifically bone collagen, while studies
of human provenience have concentrated on
dental enamel. Collagen is usually extracted from
cortical bone for the analysis of carbon and nitrogen
isotopes. Procedures for this extraction have been
described in detail in a number of publications (e.g.,
Ambrose 1990, Chisholm et al. 1983, Liden et al.
1995, Longin 1971).
The principles for human proveniencing rely
on isotopes that exhibit geographic variation and
are deposited in the human skeleton in early childhood.
Strontium, and sometimes lead and oxygen,
in tooth enamel meet those criteria. Comparison of
the isotope ratios in tooth enamel with the bone of
the same individual or with measured local isotope
ratios can provide an indication of local or non-local
origin. In our analyses, we normally sample the M1
for enamel; other teeth are taken when the M1 is not
available. Enamel is largely composed of apatite,
so little preparation is necessary. The outer surface
of the enamel is scoured, and 10–20 milligrams removed
for analysis Larger samples are needed for
lead. More information on method and procedure
will be provided below.
Carbon Isotopes in Collagen
The measurement of carbon isotope ratios in bone
collagen is well known in the study of marine resources
or certain types of plants in human diets (e.g.,
Chisholm et al. 1982, Schoeninger and DeNiro 1984,
Tauber 1981, van der Merwe and Vogel 1977). The
ratio of carbon isotopes in collagen reflects the ratio
Figure 1. Age and duration of enamel and dentin formation in teeth (Knipp er 2011).
Journal of the North Atlantic
T.D. Price
2015 Special Volume 7
73
of the diet. The method has been in use for a number
of years and is well established. Carbon and nitrogen
isotope analyses today are a routine part of the study
of human skeletal remains. These ratios are usually
calculated along with radiocarbon measurements at
dating laboratories. There are other isotopes that may
also be of interest in the study of diet such as hydrogen
and sulfur, but these are less well understood and
still experimental (e.g., Lee-Thorp 2008, Richards et
al. 2001). Carbon isotopes in tissues like hair or nail
collagen can provide information on the diet of the
last days or weeks of an individual (e.g., Macko et al.
1999, O’Connell et al. 2001). There are a number of
published summaries of carbon isotope analysis in
archaeology available (e.g., Ambrose 1993, Ambrose
and Krigbaum 2003, Hedges et al. 2006, Katzenberg
and Harrison 1997, Lee-Thorp and Sponheimer 2003,
Schoeninger 1995, Sealy 2001, van der Merwe 1992).
Lee-Thorp (2008) provides a useful review of the
development of the method and some suggestions for
future research.
Carbon is an element of biological interest with
3 stable isotopes: 12C, 13C, and 14C. Nitrogen has 2
natural stable isotopes: 14N and 15N. In each case, the
lightest isotope is present in much greater abundance
in nature than the others. For example, of the total
carbon on earth, 12C = 98.89%, 13C = 1.1%, and 14C =
0.000001%. Carbon isotopes in biological materials
are reported as a ratio of 13C to 12C. Ratios are used
in order to standardize the value that is reported,
regardless of the amount of material measured or the
concentration of the element present. These ratios
are then compared to the ratio of a standard, and reported
as a “delta” value (δ), which is the ratio of the
difference between the sample ratio and the standard
ratio compared to that of the standard, given in parts
per thousand or per mil (“‰”):
δ13C‰ =
13C / 12Csample - 13C / 12Cstandard
x 1000
13C / 12Cstandard
Delta values are not absolute isotope abundances,
but express the relative difference between a sample
reading and a standard reference material. The
standard reference material for carbon is the calcite
from a mineral deposit known as PeeDee Belemnite
(PDB).
Carbon isotope ratios are reported as δ13C‰, and
values for this ratio are negative in value and range
from roughly 0.0 to -25‰. The numbers are negative
because observed ratios are lower than the standard.
A sample with δ13C = -5.0 means that the sample is
5 per mil (or 0.5%) lighter than PeeDee belemnite.
Values for δ13C in human bone collagen range
between approximately -5‰ and -25‰. This variation
in human bone collagen is due in large part to
different sources of 13C in the plants and animals we
eat. There are two sources of heavier 13C isotopes:
the sea and some species of plants, mainly tropical
grasses, known as C4 plants. Two distinct photosynthetic
pathways produce different carbon isotope
ratios among terrestrial plant species (O’Leary 1981,
Smith and Epstein 1971). Maize, sorghum, millet
and other tropical plants (designated as C4 species)
utilize a photosynthetic pathway that efficiently
metabolizes carbon dioxide by initial conversion to
a 4-carbon compound that incorporates more available
13C (van der Merwe 1982). C4 is a more efficient
pathway for photosynthesis and is found in plants,
grasses, sedges, and grains in drier, warmer regions.
The C3 plants, more common in temperate areas,
produce a 3-carbon compound. Woody, round-leafed
species are 95% of all plants and utilize C3 photosynthesis.
The carbon isotope ratios in the bone collagen
of animals feeding on 3- or 4-carbon plants reflect
these isotopic differences. Humans who consume C4
plants have more 13C and correspondingly heavier
CO2 in their bone collagen and dental enamel.
13C/12C ratios in seawater bicarbonate are higher than
in atmospheric carbon dioxide. These differences are
observed between the plants from the land and sea,
as well as in the bone collagen of the animals that
feed on these species.
Carbon isotope ratios are reported in δ13C values
that generally become more positive (less negative)
along the continuum from plants to herbivores to
carnivores in marine and terrestrial regimes. Terrestrial
C3 diets appear as δ13C‰ values in collagen
around -20‰. Marine or largely C4 diets exhibit
δ13C‰ values in human bone collagen around -10‰.
Thus, less negative values for collagen in bone mean
either marine foods or C4 plants in the diet, or both.
Thus, human diets that include marine foods, C4
plants, or the animals that ingest C4 plants can be
distinguished using stable carbon isotope ratios.
Numerous published studies of δ13C have documented
various aspects of past human diets in antiquity.
Lee-Thorp et al. (2003), for example, reported
measurements of carbon isotope ratios in the bone
collagen of early African hominids. Richards et al.
(2000) and Bocherens et al. (2001) examined Neanderthal
diets using carbon isotope ratios. Sealy and
van der Merwe (1988) documented Holocene marine
diets from prehistoric South Africa. Ambrose et al.
(2003) documented status differences in diet ca. AD
1000 in the midwestern US. The list goes on and on,
and the range of applications continues to expand.
Journal of the North Atlantic
T.D. Price
2015 Special Volume 7
74
be reflected in carbon isotopes in carbonate when
consumed in small amounts, whereas they will be reflected
in collagen only when consumed in sizeable
proportions (Harrison and Katzenberg 2003). These
experiments showed that when the protein and bulk
diet have the same δ13C values, collagen and apatite
are enriched by 5.0‰ and ~9.4‰, respectively, relative
to the total diet. Thus, the apatite-collagen offset
(Δ13Cap–co) is 4.4‰. The results of these experiments
permit more detailed reconstruction of the isotopic
composition of prehistoric human diets. A spacing of
less than 4.4‰ indicates that dietary protein is isotopically
heavier (more positive) relative to the whole
diet. If the spacing is greater than 4.4‰, then dietary
protein is isotopically lighter (more negative) than
the whole diet (Ambrose et al. 1997, 2003; Jin et al.
2004). Harrison and Katzenberg (2003), on the other
hand, found that a δ13C apatite–diet value of +12.0‰
and a δ13C collagen–diet value of +5.1‰, with a resulting
Δ13Cap–co offset of 6.9 to be more accurate for
human samples.
Δ 13Cap-co has also been used to improve estimates
of marine foods in the diet (Ambrose et al. 2003) and
to discover C4 foods in largely C3 diets in Neolithic
China (Hu et al. 2006). Marine foods, rich in protein,
will contribute disproportionately to the amino acids
in collagen compared to terrestrial plants. Moreover,
being enriched in 13C, marine proteins will
disproportionately increase the collagen δ13C values
relative to the bulk diet, and relative to apatite δ13C
(Ambrose and Norr 1993). In marine contexts with
no C4 plants, protein comes mainly from 13C-enriched
marine animal resources, while carbohydrates
and some proteins come from 13C-depleted C3 plants
and C3-feeding animals. Because the marine protein
source is more enriched in the heavy carbon isotope,
the diet-to-collagen spacing (Δ13Cdiet–coll) should be
greater than 5‰, and collagen-to-carbonate spacing
(Δ13Ccoll–carb) should be less than 4.4‰. Because the
marine protein source is more enriched in 15N, collagen
δ15N values should also be high.
In a coastal environment lacking C4 plants, a
positive correlation should exist between collagen
δ13C and δ15N, and a negative correlation should
occur between δ15N and Δ13Cdiet-coll. In terrestrial
high-latitude diets, the entire foodweb is based on
13C-depleted C3 plants, so the bulk diet and dietary
protein should have very similar δ13C values. The
diet-collagen spacing and the apatite-collagen spacing
should be 5‰ and at least 4.4‰, respectively .
In an effort to simplify these relationships, Kellner
and Schoeninger (2007) and Froehle et al. (2012)
have published models of the relationships between
apatite and collagen carbon and nitrogen. Variation is
summarized in a scatterplot of discriminant functions
Carbon Isotopes in Apatite
Most of the paleodiet work using carbon isotopes
has focused on the organic collagen in bone. Carbon
is present in the mineral, or carbonate, portion of
bone and tooth enamel as well and also contains
information on diet (Cerling and Harris 1999,
Froehle et al 2012, Lee-Thorp et al. 1989, Sullivan
and Krueger 1981, Tieszen and Fagre 1993). Tykot
(2004) reports that δ13C values in apatite are approximately
7‰ more positive than in collagen. This
offset is variable depending on diet and is discussed
in more detail below.
Although there are potential problems with contamination
in apatite (e.g., Hedges 2002, Krueger
1991, Schoeninger and DeNiro 1982), this carbon
isotope ratio can provide substantial insight on
questions regarding diet and place of origin of the
individual from whom the sample was taken. This
tissue provides different information on diet than
bone collage. Tooth enamel—and the carbonate and
phosphate minerals where carbon is bound—forms
during childhood. Whereas bone collagen provides
a record of adult diet, tooth enamel provides information
about the diet of early childhood.
Differences in stable carbon isotope ratios between
the apatite and collagen compartments of
bone in the same individual were first reported by
Krueger and Sullivan (1984). They proposed that
consumer collagen carbon was derived from dietary
protein and apatite from dietary energy sources.
They used this model to explain systematic differences
in the isotopic composition of collagen and
apatite of non-human herbivores versus carnivores
and omnivores, and marine versus terrestrial human
diets. In protein-deficient diets, some of the carbon
for collagen may be taken from carbohydrates.
Loftus and Sealy (2012), in a comparison of collagen
and apatite carbon in archaeological samples
from South Africa, found a strong correlation between
δ13Cenamel and δ13Ccollagen and indicated that both
ratios were good proxies for past human diet. The
also examined intertooth (intraindividual) isotopic
variation, measuring each tooth from one side of
3 different mandibles. The range of values within
each mouth varied from 1.1 to 1.6%, substantially
less than reported intrapopulation variation. Loftus
and Sealy concluded that any tooth could be used for
dietary reconstruction.
Experimental studies with rats and mice have
shown that collagen carbon comes largely from
dietary protein, whereas apatite carbon more accurately
reflects the isotopic composition of the
whole diet (Ambrose and Norr 1993, Jin et al. 2004,
Tieszen and Fagre 1993). Protein-poor foods will
Journal of the North Atlantic
T.D. Price
2015 Special Volume 7
75
that summarizes the relationship among these 3 variables
(or a cross plot of δ13C for collagen and apatite)
and identifies the major components of diet in terms
of C3, C4, marine protein, and non-protein input.
Thus, carbon isotope ratios in bone and enamel
apatite can provide information on childhood diet
and on whole diet when compared with collagen.
A number of case studies have been published.
Ambrose et al. (2003) examined bone collagen and
apatite carbon in human remains from the western
Pacific and suggested the presence of previously
unknown foods in the diet. Price et al. (2012) compared
collagen and apatite carbon from the bones
and teeth of the early colonial inhabitants of the
colonial Mexican town of Campeche. Harrison
and Katzenberg (2003) reported on bone collagen
and apatite δ13C and used the offset to better estimate
the contribution of maize and marine foods in
prehistoric populations in Ontario and California,
respectively.
Nitrogen Isotopes in Collagen
Nitrogen isotopes in bone collagen are also informative
with regard to past human diets and are
reported as δ15N‰. There are 2 isotopes used in this
ratio, 14N (99.63% in nature) and 15N (0.37% in nature).
The ratio is calculated in a similar fashion as
δ13C in parts per thousand or per mil (‰), as the difference
between the sample and a standard, divided
by the standard:
δ15N‰ =
15N / 14Nsample - 15N / 14Nstandard
x 1000
15N / 14Nstandard
As noted earlier, these delta values are not absolute
isotope abundances, but express the relative difference
between a sample reading and a standard reference
material. The standard reference material for
nitrogen is air.
Natural δ15N levels in biological materials
typically range from -5‰ to +10‰ (Ambrose 1991,
Bocherens and Drucker 2003, Sealy et al. 1987).
Variations in nitrogen isotope ratios are largely
due to the role of leguminous plants in diet and the
trophic level (position in the food chain) of the organism
(e.g., Minagawa and Wada 1984, Post 2002,
Schoeninger 1985). The nitrogen isotope ratios for
plants depend primarily on how they obtain their
nitrogen—by symbiotic bacterial fixation or directly
from soil nitrates. Atmospheric nitrogen (δ15N =
0‰) is isotopically lighter than plant tissues; values
in soil tend to be even higher. Non-nitrogen-fixing
plants, which derive all of their nitrogen from soil
nitrates, can thus be expected to be isotopically
heavier than nitrogen-fixing plants, which derive
some of their nitrogen directly from the atmosphere.
Nitrogen isotope ratios can vary widely among different
plant species in the same area (e.g., Dawson
et al. 2002, Dijkstra et al. 2003). Drier environments
tend to have higher food-web δ15N values (Ambrose
1991). Grazing animals show δ15N enrichment relative
to the plants they consume; predators show further
δ15N enrichment relative to their prey species.
Thus, stable nitrogen isotopes tend to mirror trophic
level in the food chain. In one sense, nitrogen isotopes
reflect the proportion of animal protein in the
diet.
δ 15N values in the food chain are passed along
accompanied by an approximately 2–3‰ positive
shift for each trophic level, including between
mother and nursing infant (Tykot 2004). Human
consumers of terrestrial plants and animals typically
have δ15N values in bone collagen of about
6–10‰, whereas consumers of freshwater or marine
fish, seals, and sea lions may have δ15N values of
15–20‰ (Schoeninger and DeNiro 1984, Tykot
2004). A more positive nitrogen isotope ratio generally
reflects a higher trophic position (e.g., DeNiro
and Epstein 1981, Hedges and Reynard 2007, Pate
1994). Fogel et al. (1989), for example, report on the
use of nitrogen isotope ratios in identifying the age
of weaning in archaeological skeletal populations
containing infant burials.
Oxygen Isotopes in Apatite
Oxygen isotopes have been widely used as a
proxy for temperature in many climate and environmental
studies and vary geographically in surface
water and rainfall (Dansgaard 1964). Oxygen
isotopes in archaeology are used primarily to study
ancient environments and to examine past human
mobility. Oxygen isotopes in ancient human skeletal
remains are found in both tooth enamel and bone.
Oxygen is incorporated into dental enamel during
the early life of an individual and it remains unchanged
through adulthood. Samples for the analysis
of human skeletal remains are normally taken
from dental enamel due to better preservation and
resistance to diagenesis. Oxygen isotopes are also
present in bone apatite and are exchanged through
the life of the individual during bone turnover, thus
reflecting place of residence in the later years of
life. Thus, oxygen isotopes have the potential to be
used to investigate human mobility and provenience
(Bowen et al. 2005). The use of both hydrogen
isotopes in bone collagen has also been suggested
(O’Brien and Wooller 2007), but this application
remains largely experimental.
Journal of the North Atlantic
T.D. Price
2015 Special Volume 7
76
rected: δ18OC(PDB) = (0.97 x δ18OC(SMOW)) - 29.98.
Thus, a drinking water δ18OC(SMOW) value of -6.0‰
to -6.5‰(SMOW) yields an enamel carbonate δ18OC(PDB)
value of approximately -4.0‰.
The oxygen isotope ratio in the skeleton reflects
that of body water, and ultimately of drinking
water (Kohn 1996, Luz and Kolodny 1985, Luz
et al. 1984), which in turn predominantly reflects
local rainfall. Water from food and atmospheric
oxygen are minor, secondary sources. Isotopes
in rainfall are greatly affected by enrichment or
depletion of the heavy 18O isotope relative to 16O
in water due to evaporation and precipitation (e.g.,
Dansgaard 1964). Major factors affecting rainfall
δ18O values are latitude, elevation, amount of
precipitation, and distance from the evaporation
source (e.g., an ocean), i.e., geographic factors
(Fig. 2). Rainwater, can contain either isotope, and
H2
18O has a greater mass than H2
16O, and requires
more energy to evaporate and more energy to stay
in the atmosphere. When water evaporates over the
ocean, it becomes relatively lighter isotopically
(more 16O) than the water left behind. As this moisture
moves over land, the first precipitation contains
more of the heavy isotope and as the clouds
move inland (and to higher elevations) the rain becomes
even more depleted in the heavier isotope.
Thus, oxygen isotope ratios have some potential
Oxygen has three isotopes—16O (99.762%), 17O
(0.038%), and 18O (0.2%)—all of which are stable
and non-radiogenic. As with carbon and nitrogen,
isotope measurements of oxygen are always reported
as a ratio of one isotope to another, lighter and more
common cousin. Oxygen isotopes are commonly
reported as the per mil difference (‰ or parts per
thousand) in the ratio of 18O to 16O between a sample
and a standard. This value is designated as δ18O. This
value can be measured in either carbonate (CO3)-2 or
phosphate (PO4)-3 ions of apatite in tooth and bone.
Phosphate and carbonate produce comparable results
for oxygen isotope ratios (Sponheimer and Lee-
Thorp 1999). Less sample is needed for carbonate,
preparation is less demanding, and results between
laboratories are more comparable (e.g., Bryant et
al. 1996, Chenery et al. 2012, Sponheimer and Lee-
Thorp 1999). The standard used is commonly Vienna
Standard Mean Ocean Water (VSMOW or SMOW)
for phosphate oxygen, and PeeDeeBee dolomite
(PDB) for carbonate oxygen.
These 18O values for carbonate and phosphate
oxygen using different standards are comparable
though calculation. Chenery et al. (2012) defined the
relationship between the δ18O value of drinking water
and δ18O in enamel carbonate as δ18OC = (δ18ODW
+ 48.634) / 1.59 relative to SMOW. Measurements
made using a PDB standard must be further cor-
Figure 2. Oxygen isotopes in hydrological cycles and geographic variation.
Journal of the North Atlantic
T.D. Price
2015 Special Volume 7
77
seen at a given site. There are also reservoir effects.
Water in lakes, ponds, and storage vessels can have
higher δ18O values due to evaporation of the lighter
isotope. Through-flowing rivers can have δ18O that
differs from local rainfall values. Even beveragepreparation
techniques can affect mean dietary δ18O
(Knudson 2008).
In addition, considerable variability may be
expected among the teeth of a single individual or
even within a single tooth (Fricke and O’Neil 1996,
Weidemann et al. 1999, Wright and Schwarcz 1998).
Because oxygen isotopes are much lighter and have a
much greater relative mass difference than strontium,
the ratio of 18O to 16O is highly sensitive to environmental
and biological processes, and fractionation
is not uncommon. Since most permanent teeth form
over the span of 2–4 years, seasonal fluctuations
may well be visible in dental δ18O values, if measurements
are sufficiently precise. Cultural practices,
such as long-term water storage, cooking, diet, and
breastfeeding can influence the δ18O of human skeletal
tissues (White et al. 2007, Wright and Schwarcz
1998). Because of the high variation present in oxygen
isotope ratios, the application of this method for
to vary geographically and provide information on
past human movement.
At the same time, there are significant difficulties
in the application of oxygen isotope ratios to human
proveniencing (e.g., White et al. 2004). There are
potential difficulties with diagenesis (e.g., Sharp
et al. 2000). As noted, oxygen isotope ratios vary
with latitude with pronounced variation in the arctic
region. Many parts of the temperate and tropical
regions of the world, however, have similar δ18O values,
ranging broadly from approximately -2.0‰ to
-8.0‰ (Fig. 3), so that finding distinctive differences
in these regions is difficult (Bowen et al. 2005).
We have also observed unexplained variation on
the order of ±2‰ in δ18O values among individuals
from the same location in our investigations (see
also Huertas et al. 1995). Moreover, the δ18O of human
tissues may differ from that of rain falling in
the same landscape. Several different factors appear
to affect the final values measured in the human
skeleton. Rainfall δ18O levels vary from year to year
and over time in the same area (e.g., Rozanski et
al. 1993). This annual variability is undoubtedly a
major contributor to the broad range of δ18O values
Figure 3. Isoscape map of global d 18O values (Bowen 2012, Bowen and Revenaugh 2003).
Journal of the North Atlantic
T.D. Price
2015 Special Volume 7
78
provenience studies must be done with caution and
remains experimental in many regions.
Strontium Isotopes in Apatite
Strontium isotope analysis provides a robust
means for identifying human mobility in the past.
There are several published summaries of the method
(Bentley 2006, Montgomery 2010, Price 2000,
Slovak and Paytan 2011). Analytical methods are
described in detail in a number of publications (e.g.,
Frei and Price 2012, Price et al. 1994b, Slovak and
Paytan 2011, Sjögren et al. 2009). Numerous examples
of the application of strontium isotope ratios to
archaeological questions have been published (e.g.,
Benson et al. 2006, Hedman et al. 2009, Knudson
2008, Montgomery et al. 2003, Price et al. 2011,
Wright 2005).
The principle is straightforward. The strontium
isotope ratio of 87Sr/86Sr varies among different
kinds of rocks and sediments. Because the 87Sr forms
through a radiogenic process as a product of decay
from rubidium-87 over time, older rocks with more
rubidium have a higher 87Sr/86Sr ratio, while younger
rocks with less rubidium are at the opposite end of
the range with low ratios (e.g., Montgomery et al.
2006). The half-life for this process is on the order
of billions of years, so the abundance of 87Sr does not
change on the time scales of human prehistory, but
can accumulate appreciably on geologic time scales
such that regions with old rocks have more 87Sr than
regions with relatively younger rocks.
Strontium moves into humans from rocks and
sediment through the food chain (Price 1989, 2000;
Sillen and Kavanagh 1982). Strontium is chemically
similar to calcium and substitutes for calcium
in enamel and bone. Because some rocks and sediments
contain higher concentrations of strontium
than others, a correction is made by using a ratio of
the radiogenic 87Sr to a non-radiogenic 86Sr.
The amount of 87Sr in nature varies but is ~7%
of total strontium and 86Sr is 10%. This ratio normally
varies from about 0.700 in young rocks with
low Rb to >0.730 in high-Rb rocks that are billions
of years old. Most measurements fall in the range
of 0.703 to 0.723. This ratio generally varies with
geology and is not significantly altered by biological
processes, so that the 87Sr/86Sr ratio in enamel
reflects that of the underlying geology where one
was born and raised when the enamel formed.
If one moves to a new location with a different
geologic setting, or is buried in a new place, the
enamel isotopes will not match those of the new
location, allowing us to identify the individual as
an immigrant.
An essential question regarding strontium isotope
analysis concerns the local strontium isotope
signal for the area in which the burial is located. In
actual fact, levels of strontium isotopes in human tissue
may vary from local geology for various reasons
(Price et al. 2002) and, for this reason, it is necessary
to measure bioavailable levels of 87Sr/86Sr to determine
local strontium isotope ratios. The local bioavailable
isotopic signal of the place of burial can be
determined in several ways: in human bone from the
individuals whose teeth are analyzed, from the bones
of other humans or archaeological fauna at the site,
or from modern fauna in the vicinity. This baseline
information on isotope values across an area needs
to be obtained in order to make useful and reliable
statements about the origins of the human remains
under study (Frei and Price 2012, Price et al. 2002).
Lead Isotopes in Apatite
Lead (Pb) behaves remarkably like strontium
in terms of provenience studies. Both elements
substitute for calcium in hydroxyapatite in skeletal
tissue, are transferred with negligible fractionation
from soils into plants and through successive trophic
levels, and are found as trace constituents in
plants and animals. Virtually the entire body burden
of both elements is deposited in the skeleton. Bone
concentrations of both elements are proportionate to
dietary (and hence environmental) abundances, and
both elements undergo trophic-level biopurification.
Most importantly, both elements have stable and
radiogenic isotopes, such that the ratios of these
isotopes depend upon the local geology and are thus
geographically variable. In contrast to strontium,
there is very little lead in seawater.
Lead is the element with the heaviest stable
isotope (208) in nature. Lead, in addition to nonradiogenic
204Pb, has not one, but three, radiogenic
isotopes: 206Pb, 207Pb, and 208Pb. Measurable differences
in stable lead isotopic compositions are caused
by the differential radioactive decay of 238U (t1/2 =
4.5 x 109 years), 235U (t1/2 = 0.70 x 109 years), and
232Th (t1/2 = 1.4 x 1010 years) to form 206Pb, 207Pb, and
208Pb, respectively (Faure and Mensing 2005). The
relative abundances of these isotopes in nature are
204Pb = 1.4%, 206Pb = 24.1%, 207Pb = 22.1%, and 208Pb
= 52.4%.
Normally the relative abundance of the different
isotopes of an element varies little across the surface
of the earth, but that is not the case with lead. Stable
lead isotopes, and their ratios, locally vary according
to both the geologic age of the terrain and the
amounts of the parent isotopes of uranium and thorium.
Importantly, lead isotope ratios, like strontium
Journal of the North Atlantic
T.D. Price
2015 Special Volume 7
79
A variety of isotopes are used in the study of
human remains. Carbon and nitrogen isotopes have
often been measured in bone collagen for information
on diet and are especially useful for detecting
certain types of plants or marine foods in the diet.
At the same time, smaller differences in past human
diets may also be recorded in these isotopes and thus
they are potentially useful for further differentiation
among populations. Carbon and oxygen can be measured
in both bone and tooth enamel, in the mineral
or apatite component of the tissue. Carbon isotope
ratios in enamel apatite provide information on
childhood diet. Carbon isotope ratios in bone apatite
provide information on adult diet. Comparison of
this ratio in apatite and collagen can provide some
indication of the differences between protein intake
and whole-diet composition.
Oxygen isotopes vary geographically with
changes in rainfall and provide information sometimes
useful for human proveniencing. The oxygen
isotope ratio in apatite reflects that of drinking water
and ultimately rainfall or snow intake. However, oxygen
isotopes are quite variable in human remains,
and the approach remains experimental.
Strontium isotopes in enamel apatite provide a
fairly robust method for investigating past human
mobility. Strontium isotopes reach the human skeleton
from the food chain, and ultimately from the
rocks and sediments on which plants are growing.
Strontium isotope ratios in tooth enamel provide a
signature of the place of birth and early childhood
that can be compared to the value for the place of
burial to determine if an individual is local or not.
It is important to remember that while strontium
isotopes are useful for identifying non-local individuals
in a population, it is much more difficult
to determine place of origin because of the widespread
occurrence of certain strontium isotopic
signatures.
It is also essential in the investigation of past human
mobility to have information on the local and
regional isotope values in order to have a baseline
for comparison. These baseline values cannot be
directly predicted from local geology and need to
be measured to determine the bioavailable strontium
isotope ratios of the place of burial. Price et al. (2015
[this issue]) considers the bioavailable strontium
isotope ratios in the potential homelands and destinations
of the Viking settlers of the North Atlantic.
This baseline information is important to have prior
to an examination of values in the tooth enamel of
these individuals.
Lead isotopes follow principles of distribution
and deposition similar to strontium. Lead is
isotope ratios, are not changed by biological or other
low-temperature chemical or physical processes.
The ratios present in dental enamel reflect those of
dietary intake and, in the New World prior to the
modern industrial era, that of the local geology. The
four stable isotopes of lead provide a large number of
potentially useful ratios, but the values of 206Pb/204Pb,
207Pb /204Pb, 208Pb /204Pb, 207Pb /206Pb, and 208Pb /206Pb
are commonly used in isotopic provenience studies.
Lead isotope analysis was initially applied to
lead-rich artifacts, such as those made of copper,
bronze, and lead-bearing ores, to study provenience
questions. This method was later used with other
artifact classes such as ceramics. Lead isotopes can
also be used as a tracer in past human-mobility studies
(e.g., Augustine 2002; Budd 1999, 2000; Carlson
1996; Corruccini et al. 1987; Gulson et al. 1997;
Molleson et al. 1986; Montgomery et al. 1999; Reinhard
and Ghazi 1992).
There are several problems with lead isotope
analysis, including the low concentrations of this
element in dental enamel, the poorly known geographic
distribution of most lead isotope values, and
the solubility of lead resulting in potential contamination
of modern and ancient samples, particularly
from the combustion products of leaded gasoline
(Albarède et al. 2011). The ubiquity of these pollutants
means that an ultraclean lab is often necessary
to avoid contamination issues. These factors make
interpretation of ratios for lead isotopes considerably
more complex than for strontium isotopes.
Although there is evidence for diagenesis of lead
in buried bone (e.g., Kyle 1986), this contamination
does not appear to be present in tooth enamel in most
cases (Montgomery et al. 1999, Waldron 1983).
Because of their variability, lead isotopes have had
a successful history in archaeometric research for artifact
provenience studies. More pertinent here, lead
isotopes have been used in recent years to identify
prehistoric human immigrants in a number of different
contexts (e.g., Budd 1999, 2000; Carlson 1996;
Gulson et al. 1997; Molleson et al. 1986; Montgomery
et al. 1999; Reinhard and Ghazi 1992).
Conclusions
Major questions pursued in isotopic studies of
human remains focus on past diet and human mobility.
Two major types of skeletal tissue—enamel and
bone—are used in such studies. Enamel retains the
chemistry of early childhood, while bone contains
the chemistry of the last decade or so of life. The
two types of tissue can provide insight into part of
the life history of an individual.
Journal of the North Atlantic
T.D. Price
2015 Special Volume 7
80
spectives on questions about past diet (e.g., Hedges
et al. 2008, Katzenberg et al. 1995, Schwarcz and
Schoeninger 2011). Carbon and oxygen in apatite are
also measured simultaneously in a number of labs
and routinely used together in studies of past diet and
movement. Using more than 2 isotopes can provide
even more information (e.g., Jay et al. 2007, Knudson
and Price 2007). Wright and Schwarcz (1998) measured
3 isotopes—carbon, oxygen, and nitrogen—in
the investigation of infant diets in the Maya region.
Price et al. (2012) in a study of a colonial cemetery
in Campeche, Mexico, employed all of the isotopes
discussed in this essay—carbon and nitrogen in collagen,
carbon and oxygen in enamel apatite, and
strontium and lead in enamel—to assess the places
of origin of the buried individuals. Larger samples
of burial populations and multiple isotope investigations
will provide significantly more information on
past diet and mobility.
Isotopic studies can also be used together with
molecular approaches such as use of DNA to learn
even more about past human populations in terms of
diet, genetic relationships, and mobility. Haak et al.
(2008) documented a variety of information on these
questions for a group of burials from Neolithic Germany.
The potential for isotopic studies is enormous.
This work has been ongoing for about 30 years and
is in its early childhood. The next 30 years are going
to be very exciting.
Literature Cited
Albarède, F., A.-M. Desaulty, and J. Blichert-Toft. 2011.
A geological perspective on the use of Pb isotopes in
archaeometry. Archaeometry 54:853–857.
AlQahtani, S.J., M.P. Hector, and H.M. Liversidge. 2010.
Brief communication: The London atlas of human
tooth development and eruption. American Journal of
Physical Anthropology 142:481–490.
Ambrose, S.H. 1990. Preparation and characterization of
bone and tooth collagen for isotopic analysis. Journal
of Archaeological Science 17:431–451.
Ambrose, S.H. 1991. Effects of diet, climate, and physiology
on nitrogen isotope abundances in terrestrial foodwebs.
Journal of Archaeological Science 18:293–317.
Ambrose, S.H. 1993. Isotopic analysis of paleodiets:
Methodological and interpretive considerations. Pp.
59–129, In M.K. Sandford (Ed.). Investigations of
Ancient Human Tissue: Chemical Analysis in Anthropology.
Gordon and Breach Science Publishers,
Langhorne, PA, USA.
Ambrose, S.H., and L. Norr. 1993. Experimental evidence
for the relationship of the carbon isotope ratios of whole
diet and dietary protein to those of bone collagen and
carbonate. Pp.1–37, In J.B. Lambert and G. Grupe
(Eds.). Prehistoric Human Bone: Archaeology at the
Molecular Level. Springer-Verlag, Berlin, Germany.
substituted for calcium in bioapatite and is deposited
throughout the skeleton, albeit in much lower
concentrations. The distribution of sources of lead
isotopes, however, is more specific. While strontium
occurs in most rocks and sediments, lead is not
present everywhere, and isotopic variation in lead
is not completely understood. Lead isotopes are not
commonly employed in human mobility studies because
of these issues and others. Ultraclean labs are
required because of the ubiquity of contamination,
and the analysis is expensive. At the same time, the
larger number of isotopes present in lead provides
several different kinds of information for investigation.
In general terms, use of lead isotopes remain an
experimental method in the search for past human
provenience.
As with any method in archaeological research,
there are problems and uncertainties in the isotopic
investigation of past diet and mobility. Some of these
issues have been addressed in various publications
(e.g., Fuller et al. 2005, Montgomery et al. 2007,
Pollard 2011, Sillen et al. 1989, Van Strydonck et al.
2005). The science is evolving as evidenced by the
numerouse changes that radiocarbon dating has experienced
over the last 60 years as adjustments and corrections
are introduced to fine tune the method. These
calibrations are an inevitable part of an inexact science.
As Pollard (2011) has observed, the addition of
people to the analysis complicates our questions and
answers enormously. Nevertheless, the final criteria
by which these studies must be judged is what has
been learned and where we go from here. Problems
and uncertainties are part of the process.
Each of these different isotopic methods offers
interesting information and potential. At the same
time, there are often questions and uncertainties that
make decisions about diet or past mobility difficult.
Two directions point to some solution to these problems:
larger samples and multi-isotope analyses. In
many studies to date, the number of samples has
been only a small proportion of the larger burial
population under investigation. In order to better
observe and understand the variation present within
populations and to compare samples between sites,
it is essential that more samples be analyzed (Price
et al. 2010). Of course, this requires more time and
money, but the benefits, in terms of more nuanced
results, outweigh the costs.
The use of combined or multi-element studies
provides a much more powerful approach to such
questions. The combination of two isotopic methods
is commonplace in many studies today. Carbon and
nitrogen isotopes in collagen are usually measured
simultaneously and provide complementary perJournal
of the North Atlantic
T.D. Price
2015 Special Volume 7
81
Ambrose, S.H. and J. Krigbaum. 2003. Bone chemistry
and bioarchaeology. Journal of Anthropological Archaeology
22:193–199.
Ambrose S.H., B.M. Butler, D.B. Hanson, R.L. Hunter-
Anderson, and H.W. Krueger. 1997. Stable isotopic
analysis of human diet in the Marianas Archipelago,
western Pacific. American Journal of Physical Anthropology
104:343–361.
Ambrose, S.H., J. Buikstra, and H.W. Krueger. 2003.
Status and gender differences in diet at Mound 72, Cahokia,
revealed by isotopic analysis of bone. Journal
of Anthropological Archaeology 22:217–226.
Augustine, L. 2002. Lead isotope ratios: The key to addressing
migration patterns of European-Americans
to Grafton, IL. Ph.D. Dissertation. Department of
Anthropology, Loyola University, Chicago, IL, USA.
Balasse, M. 2002. Reconstructing dietary and environmental
history from enamel isotopic analysis: Time
resolution of intra-tooth se- quential sampling. International
Journal of Osteoarchaeology 12:155–165.
Bender, M., D. Baerreis, and R. Steventon. 1981. Further
light on carbon isotopes and Hopewell architecture.
American Antiquity 46:346–353.
Benson, L.V., E.M. Hattori, H.E. Taylor, S.R. Poulson,
and E.A. Jolie. 2006. Isotope sourcing of prehistoric
willow and tule textiles recovered from western Great
Basin rock shelters and caves: Proof of concept. Journal
of Archaeological Science 33:1588–1599.
Bentley, R.A. 2006. Strontium isotopes from the Earth to
the archaeological skeleton: A review. Journal of Archaeological
Method and Theory 13:135–187.
Bocherens, H., and D. Drucker. 2003. Trophic level isotopic
enrichment of carbon and nitrogen in bone collagen:
Case studies from recent and ancient terrestrial
ecosystems. International Journal of Osteoarchaeology
13:46–53.
Bocherens, H., D. Billiou, A. Mariotti, M. Patou-Mathis,
M. Otte, D. Bonjean, and M. Toussaint. 2001. New isotopic
evidence for dietary habits of Neandertals from
Belgium. Journal of Human Evolution 40:497–505.
Bowen, G.J. 2012. Gridded maps of the isotopic composition
of meteoric waters. Available online at http://
www.waterisotopes.org. Accessed on 11 July 2015.
Bowen G.J., and J. Revenaugh. 2003. Interpolating the
isotopic composition of modern meteoric precipitation.
Water Resources Research 39:1299–1314.
Bowen, Gabriel J., Leonard I. Wassenaar, and Keith A.
Hobson. 2005. Global application of stable hydrogen
and oxygen isotopes to wildlife forensics. Oecologia
143:337–348.
Brill, R.H., and J.M. Wampler. 1965. Isotope studies
of ancient lead. American Journal of Archaeology
69:165–166.
Bryant, J.D., P.L. Koch, P.N. Froelich, W.J. Shower, and
B.J. Genna. 1996. Oxygen isotope partitioning between
phosphate and carbonate in mammalian apatite.
Geochimica et Cosmochimica Acta 60:5145–5148.
Budd, P., J. Montgomery, P. Rainbird, R.G. Thomas, and
S.M.M. Young. 1999. Pb- and Sr-isotope composition
of human dental enamel: An indicator of Pacific Islander
population dynamics, in The Pacific from 5000
to 2000 BP. Pp. 301–311, In J.C. Galipaud and I. Lilley
(Eds.). Colonisation and Transformations. Institut de
Recherche pour le Dévelopement, Paris, France.
Budd, P., J. Montgomery, J. Evans, and B. Barreiro. 2000.
Human tooth enamel as a record of the comparative
lead exposure of prehistoric and modern people. The
Science of the Total Environment 263:1–10.
Carlson, A. K. 1996. Lead isotope analysis of human bone
for addressing cultural affinity: A case study from
Rocky Mountain House, Alberta. Journal of Archaeological
Science 23(4):557–568.
Cerling, T.E., and J.M. Harris. 1999. Carbon isotope
fractionation between diet and bioapatite in ungulate
mammals and implications for ecological and paleoecological
studies. Oecologia 120:347–363.
Chenery, C.A., V. Pashley, A.L Lamb, H.J. Sloane, and
J.A. Evans. 2012. The oxygen isotope relationship between
the phosphate and structural carbonate fractions
of human bioapatite. Rapid Communications in Mass
Spectrometry 26:309–319.
Chisholm, B.S., D.E. Nelson, and H.P. Schwarcz. 1982.
Stable carbon as a measure of marine versus terrestrial
protein in ancient diets. Science 216:1131–1132.
Chisholm, B.S., D.E. Nelson, A. Hobson, H.P. Schwarcz,
and M. Knyf. 1983. Carbon isotope measurement techniques
for bone collagen: Notes for the archaeologist.
Journal of Archaeological Science 10:355–360
Corruccini, R.S., A.C. Aufderheide, J.S. Handier, and L.E.
Wittniers Jr. 1987. Patterning of skeletal lead content
in Barbados slaves. Archaeometry 29:233–239.
Dansgaard, W. 1964. Stable isotopes in precipitation. Tellus
16:466–468.
Dawson, T.E., S. Mambelli, A.H. Plamboeck, P.H.
Templer, and K.P. Tu. 2002. Stable isotopes in plant
ecology. Annual Review of Ecology and Systematics
33:507–559.
DeNiro, M.J., and S. Epstein. 1978. Influence of diet on
the distribution of carbon isotopes in animals. Geochemica
et Cosmochemica Acta 45:341–351.
DeNiro, M.J., and S. Epstein. 1981. Influence of diet on
the distribution of nitrogen isotopes in animals. Geochimica
et Cosmochimica Acta 45:341–351.
Dijkstra P., C. Williamson, O. Menyailo, R. Doucett, G.
Koch, and B.A. Hungate. 2003. Nitrogen stable isotope
composition of leaves and roots of plants growing
in a forest and a meadow. Isotopes and Environmental
Health Studies 39:29–39.
ElNesr, N.M., and J.K. Avery. 1994. Tooth eruption and
shedding. Pp. 110–129, In J.K. Avery (Ed.). Oral Development
and Histology. Thieme Medical Publishers,
New York, NY, USA.
Ericson, J.E. 1985. Strontium isotope characterization in
the study of prehistoric human ecology. Journal of Human
Evolution 14:503–514.
Faure, G., and T.M. Mensing. 2005. Isotopes: Principles
and Applications. John Wiley, New York, NY, USA.
Journal of the North Atlantic
T.D. Price
2015 Special Volume 7
82
Fogel, M.L., N. Tuross, and D.W. Owsley. 1989. Nitrogen
isotope tracers of human lactation in modern and
archaeological populations. Pp. 111–117, In Annual
Report of the Director, Geophysical Laboratory 1988–
1989. Carnegie Institute, Washington, DC, USA.
Frei, K.M., and T.D. Price. 2012. Strontium isotopes
and human mobility in prehistoric Denmark. Journal
of Anthropological and Archaeological Sciences
4:103–114.
Fricke, H.C., and J.R. O’Neil. 1996. Inter- and intratooth
variation in the oxygen isotope composition of
mammalian tooth enamel phosphate: Implications for
palaeoclimatological and palaeobiological research.
Palaeogeography, Palaeoclimatology, Palaeoecology
126:91–99
Froehle, A.W., C.M. Kellner, and M.J. Schoeninger.
2012. Multivariate carbon and nitrogen stable isotope
model for the reconstruction of prehistoric human
diet. American Journal of Physical Anthropology
147:352–369.
Fuller B.T., J.L. Fuller, N.E. Sage, D.A. Harris, T.C.
O’Connell, and R.E.M. Hedges. 2005. Nitrogen balance
and 15N: Why you’re not what you eat during
nutritional stress. Rapid Communications in Mass
Spectrometry 19:2497–2506.
Grupe, G., and H. Piepenbrink. 1987. Processing of prehistoric
bones for isotopic analysis and the meaning
of collagen C/N ratios in the assessment of diagenetic
effects. Human Evolution 2:511–515.
Gulson, B.L., C.W. Jameson, and B.R. Gillings. 1997.
Stable lead isotopes in teeth as indicators of past domicile:
A potential new tool in forensic science? Journal
of Forensic Sciences 42:787–791.
Haak, W., G. Brandt, H.N. De Jong, C. Meyer, R. Ganslmeier,
V. Heyd, C. Hawkesworth, A.W.G. Pike, H.
Meller, and K.W. Alt. 2008. Ancient DNA, strontium
isotopes, and osteological analyses shed light on social
and kinship organization of the Later Stone Age.
Proceedings of the National Academy of Sciences
105:18226–18231.
Harrison, R.G., and M.A. Katzenberg. 2003. Paleodiet
studies using stable carbon isotopes from bone apatite
and collagen: Examples from southern Ontario and
San Nicolas Island, California. Journal of Anthropological
Archaeology 22:227–244.
Hedges, R.E.M. 2002. Bone diagenesis: An overview of
processes. Archaeometry 44:319–328.
Hedges, R.E.M., and L.M. Reynard. 2007. Nitrogen isotopes
and the trophic level of humans in archaeology.
Journal of Archaeological Science 34:1240–1251.
Hedges, R.E.M., R.E. Stevens, and P.L. Koch. 2006. Isotopes
in bones and teeth. Pp. 117–145, In M.J. Leng
(Ed.). Isotopes in Palaeoenvironmental Research Vol.
10. Springer, Dordrecht, The Netherlands.
Hedges, R.E.M., A. Saville, and T.C. O’Connell 2008.
Characterizing the diet of individuals at the Neolithic
chambered tomb of Hazleton North, Gloucestershire,
England, using stable isotopic analysis. Archaeometry
50:114–128.
Hedman, K.M., B.B. Curry, T.M. Johnson, P.D. Fullagar,
and T.E. Emerson. 2009. Variation in strontium isotope
ratios of archaeological fauna in the midwestern
United States: A preliminary study. Journal of Archaeological
Science 36:64–73.
Hillson, S. 2005. Teeth. Cambridge University Press,
Cambridge, UK.
Hoppe, K.A., P.L. Koch, and T.T. Furutani. 2003. Assessing
the preservation of biogenic strontium in fossil
bones and tooth enamel. International Journal of Osteoarchaeology
13:20–28.
Hu, Y., S.H. Ambrose, and C. Wang. 2006. Stable isotopic
analysis of human bones from Jiahu site, Henan,
China: Implications for the transition to agriculture.
Journal of Archaeological Science 33:1319–1330.
Huertas, A.D., P. Iacumin, B. Stenni, B.S. Chillon, and
A. Longinelli. 1995. Oxygen-isotope variations of
phosphate in mammalian bone and tooth enamel. Geochimica
et Cosmochimica Acta 59:4299–305.
Jay, M., V. Grimes, J. Montgomery, K. Lakin, and J.
Evans. 2007. Multi-isotope analysis. Pp. 351–354, In
F. Brown, C. Howard-Davis, T. Evans, S. O’Connor,
A. Spence, R. Heawood, and A. Lupton (Eds.). The
Archaeology of the A1 (M) Darrington to Dishforth
DBFO Road Scheme. Oxford Archaeology North,
Lancaster, UK.
Jin, S., S.H. Ambrose, and R.P. Evershed. 2004. Stable
carbon isotopic evidence for differences in the dietary
origin of bone cholesterol, collagen, and apatite: Implications
for their use in paleodietary reconstructions.
Geochimica et Cosmochimica Acta 68:61–72.
Katzenberg, M.A., and R.G. Harrison. 1997. What’s in a
bone? Recent advances in archaeological bone chemistry.
Journal of Archaeological Research 5:265–293.
Katzenberg, M.A., H.P. Schwarcz, M. Knyf and F.J.
Melbye. 1995. Stable isotope evidence for maize horticulture
and paleodiet in southern Ontario, Canada.
American Antiquity 60:335–350.
Kellner C.M., and M.J. Schoeninger. 2007. A simple
carbon isotope model for reconstructing prehistoric
human diet. American Journal of Physical Anthropology
133:1112–1127.
Knipper, C. 2011. Die räumliche Organisation der Linearbandkeramischen
Rinderhaltung: Naturwissenschaftliche
und archäologische Untersuchungen. BAR
International Series 2005. Archaeopress, Oxford, UK.
Knudson, K.J. 2008. Tiwanaku influence in the south central
Andes: Strontium isotope analysis and Middle Horizon
migration. Latin American Antiquity 19:3–24.
Knudson, K.J., and T.D. Price. 2007. The utility of multiple
chemical techniques in archaeological residential
mobility studies. American Journal of Physical Anthropology
132:25–39.
Kohn, M.J. 1996. Predicting animal d18O: Accounting
for diet and physiological adaptation. Geochimica et
Cosmochimica Acta 60:4811–4829.
Kohn, M.J., M.J. Schoeninger, and W.W. Barker. 1999.
Altered states: Effects of diagenesis on fossil-tooth
chemistry. Geochimica Cosmochimica Acta 63:2737–
2747.
Journal of the North Atlantic
T.D. Price
2015 Special Volume 7
83
Montgomery, J. 2010. Passports from the past: Investigating
human dispersals using strontium isotope analysis
of tooth enamel. Annals of Human Biology 37:325–46.
Montgomery, J., P. Budd, A. Cox, P. Krause, and R.G.
Thomas. 1999. LA-ICP-MS evidence for the distribution
of Pb and Sr in Romano-British medieval
and modern human teeth: Implications for life history
and exposure reconstruction. Pp. 290–296, In
S.M.M. Young, A.M. Pollard, P. Budd, and R.A. Ixer
(Eds.).Metals in Antiquity: Proceedings of the International
Symposium. Archaeopress, Oxford, UK.
Montgomery, J., J.A. Evans, and T. Neighbour. 2003. Sr
isotope evidence for population movement within the
Hebridean Norse community of NW Scotland. Journal
of the Geological Society of London 160:649–653.
Montgomery, J., J.A. Evans, and G. Wildman. 2006. Sr-
87/Sr-86 isotope composition of bottled British mineral
waters for environmental and forensic purposes.
Applied Geochemistry 21:1626–1634.
Montgomery,
J., J.A. Evans, and
R.E. Cooper. 2007.
Resolving archaeological populations with Sr-isotope
mixing models. Applied Geochemistry 22:1502–1514.
O’Brien, D.M., and M.J. Wooller. 2007. Tracking human
travel using stable oxygen and hydrogen isotope
analyses of hair and urine. Rapid Communications in
Mass Spectrometry 21:2422–30.
O’Connell T.C., R.E.M. Hedges, M.A. Healey, and
A.H.R.W. Simpson. 2001. Isotopic comparison of hair,
nail, and bone: Modern analyses. Journal of Archaeological
Science 28:1247–1255.
O’Leary, M. 1981. Carbon isotope fractionation in plants.
Phytochemistry 20:553–567.
Pate, F.D. 1994. Bone chemistry and paleodiet. Journal of
Archaeological Method and Theory 1:161–209.
Pollard, A.M. 2011. Isotopes and impact: A cautionary tale
Antiquity 85:631–638.
Post, D.M. 2002. Using stable isotopes to estimate trophic
position: Models, methods, and assumption. Ecology
83:703–718.
Price, T.D. (Ed.) 1989. The Chemistry of Prehistoric Human
Bone. Cambridge University Press, Cambridge, MA,
USA.
Price, T.D. 2000. Les isotopes du strontium dans les
restes squeletiques. Étude des migrations de populations
archéologiques. Les Nouvelles de l‘Archeologie
80:29–34.
Price, T.D., G. Grupe, and P. Schrorter. 1994a. Reconstruction
of migration patterns in the Bell Beaker
period by stable strontium isotope analysis. Applied
Geochemistry 9:413–417.
Price, T.D., C.M. Johnson, J.A. Ezzo, J.H. Burton, and
J.A. Ericson. 1994b. Residential mobility in the Prehistoric
Southwest United States. A preliminary study
using strontium isotope analysis. Journal of Archaeological
Science 24:315–330.
Price, T.D., J.H. Burton, and R. Bentley. 2002 Characterization
of biologically available strontium isotope
ratios for the study of Prehistoric migration. Archaeometry
44:117–135.
Krueger, H.W. 1985. Sr Isotopes and Sr/Ca in Bone. Paper
presented at Bone Mineralization Conference, Warrenton,
VA. Available upon request from the author of this
paper (T.D. Price).
Krueger, H.W. 1991. Exchange of carbon with biological
apatite. Journal of Archaeological Science18:355–361.
Krueger, H.W., and C.H. Sullivan. 1984. Models for carbon
isotope fractionation between diet and bone. Pp.
205–220, In J.R. Turnland and P.E. Johnson (Eds.).
Stable Isotopes in Nutrition. American Chemical Society
Symposium Series, No 258. Washington, DC, USA.
Kyle, J.H. 1986. Effect of post-burial contamination on
the concentrations of major and minor elements in
human bones and teeth? The implications for paleodietary
research. Journal of Archaeological Science
13:403–416.
Lee-Thorp, Julia. 2008. On isotopes and old bones. Archaeometry
50:925–950.
Lee-Thorp, J., and M. Sponheimer. 2003. Three case
studies used to reassess the reliability of fossil bone
and enamel isotope signals for paleodietary studies.
Journal of Anthropological Archaeology 22:208–216.
Lee-Thorp, J.A., J.C. Sealy, and N.J. van der Merwe.
1989. Stable carbon isotope ratio differences between
bone collagen and bone apatite and their relationship
to diet. Journal of Archaeological Science 16:585–599.
Lee-Thorp, J.A., M. Sponheimer, and N.J. van der Merwe.
2003. What do stable isotopes tell us about hominid
diets? International Journal of Osteoarchaeology
13:104–113.
Liden, K., Cheryl Takahashi, D. Erle Nelson. 1995. The
effects of lipids in stable carbon isotope analysis and
the effects of NaOH treatment on the composition of
extracted bone collagen. Journal of Archaeological
Science 22:321–326.
Loftus, E., and J. Sealy. 2012. Interpreting stable carbon
isotopes in human tooth enamel: An examination of
tissue spacings from South Africa. American Journal
of Physical Anthropology 147:499–507.
Longin, R. 1971. New Method of Collagen Extraction for
Radiocarbon Dating. Nature 230:241–242.
Luz, B., and Y. Kolodny. 1985. Oxygen isotope variations
in phosphate of biogenic apatites. IV. Mammal
teeth and bones. Earth and Planetary Science Letters
75:29–36.
Luz, B., Y. Kolodny, and M. Horowitz. 1984. Fractionation
of oxygen isotopes between mammalian bonephosphate
and environmental drinking water. Geochimica
et Cosmochimica Acta 48:1689–1693.
Macko, S.A., G. Lubec, M. Teschler-Nicola, V. Andrusevich,
and M.H. Engel. 1999. The Ice Man’s diet as
reflected by the stable nitrogen and carbon isotopic
composition of his hair. FASEB Journal 13:559–562.
Minagawa, M., and E. Wada, 1984. Stepwise enrichment
of 15N along food chains: Further evidence and the
relation between δ15N and animal age. Geochimica et
Cosmochimica Acta 48:1135–1140.
Molleson, T.I., D. Eldridge, and N. Gale. 1986. Identification
of lead sources by stable isotope ratios in bones
and lead from Poundbury Camp, Dorset. Oxford Journal
of Archaeology 5:249–253.
Journal of the North Atlantic
T.D. Price
2015 Special Volume 7
84
Sealy, J. 1989. Reconstruction of Later Stone Age diets in
the southwestern Cape, South Africa: Evaluation and
application of five isotopic and trace element techniques.
Ph.D. Dissertation. Department of Archaeology,
University of Capetown, Capetown, South Africa.
Sealy, J. 2001. Body tissue chemistry and palaeodiet. Pp.
269–279, In D.R. Brothwell and A.M Pollard (Eds.).
Handbook of Archaeological Sciences. John Wiley
and Sons, Chichester, UK.
Sealy, J.C., and N.J van der Merwe. 1987. Stable carbon
isotopes, Later Stone Age diets, and seasonal mobility
in the southwestern Cape. Pp. 262–268, In J. Parkington
and M. Hall (Eds.). Papers in the Prehistory of the
Western Cape, South Africa. British Archaeological
Reports, International Series 332, Oxford, UK.
Sealy, J.C., and N.J van der Merwe. 1988. Social, spatial
and chronological patterning in marine food use as
determined by 13C measurements of Holocene human
skeletons from the southwestern Cape, South Africa.
World Archaeology 20:87–102.
Sealy, J.C., N.J. van der Merwe, J.A. Lee-Thorp, and
J.L. Lanham. 1987. Nitrogen isotopic ecology in
southern Africa: Implications for environmental and
dietary tracing. Geochimica et Cosmochimica Acta
51:2707–2717.
Sealy, J., R. Armstrong, and C. Schrire. 1995. Beyond lifetime
averages: Tracing life histories through isotopic
analysis of different calcified tissues from archaeological
human skeletons. Antiquity 69:290–300.
Sharp, Z.D., V. Atudorei, and H. Furrer. 2000. The effect of
diagenesis on oxygen isotope ratios of biogenic phosphates.
American Journal of Science 300:222–237.
Sillen, A., and M. Kavanagh. 1982. Strontium and paleodietary
research: A review. American Journal of Physical
Anthropology 25:67–90.
Sillen, A., J. Sealy, and N.J. van der Merwe. 1989.
Chemistry and paleodietary research: No more easy
answers. American Antiquity 54:504–512.
Sjögren, K.-G., T.D. Price, and T. Ahlström. 2009.
Megaliths and mobility in southwestern Sweden:
Investigating relations between a local society and
its neighbours using strontium isotopes. Journal of
Anthropological Archaeology 28:85–101.
Slovak, N.M., and A. Paytan. 2011. Applications of Sr
Isotopes in Archaeology. Advances in Isotope Geochemistry
5:743–768.
Smith, B.N., and S. Epstein. 1971. Two categories of
13C/12C ratios for higher plants. Plant Physiology
47:380–384.
Sponheimer, M., and J.A. Lee-Thorp. 1999. Oxygen isotopes
in enamel carbonate and their ecological significance.
Journal of Archaeological Science 26:723–728.
Stephan, E. 2000. Oxygen isotope analysis of animal bone
phosphate: Method refinement, influence of consolidants,
and reconstruction of palaeotemperatures for
Holocene sites. Journal of Archaeological Science
27:523–535.
Sullivan, C.H., and H.W. Krueger. 1981. Carbon isotope
analysis in separate chemical phases in modern and
fossil bone. Nature 292:333–335.
Price, T.D., K.M. Frei, H. Gestsdottir, and V. Tiesler.
2010. Isotopes and mobility: Case studies with large
samples. Mitteilungen der Berliner Gesellschaft
für Anthropologie, Ethnologie und Urgeschichte
31:203–212.
Price, T.D., A. Dobat, N. Lynnerup, and P. Bennike. 2011.
Who was in Harold Bluetooth’s army? Strontium
isotope investigation of the cemetery at the Viking
Age fortress at Trelleborg, Denmark. Antiquity
85:476–489.
Price, T.D., J.H. Burton, V. Tiesler, A. Cucina, P. Zabala,
and R. Tykot. 2012. Isotopic studies of human skeletal
remains from a 16th–17th-century AD churchyard in
Campeche, Mexico: Diet, ethnicity, place of origin,
and age. Current Anthropology 53(4):396–433.
Price, T.D., K.M. Frei, and E. Nauman. 2015. Isotopic
baselines in the North Atlantic region. Journal of the
North Atlantic Special Volume 7:103–136.
Reinhard, K.J., and A.M. Ghazi. 1992. Evaluation of lead
concentrations in 18th-century Omaha Indian skeletons
using ICP-MS. American Journal of Physical
Anthropology 89:183–195.
Richards, M.P., P.B. Pettitt, E. Trinkaus, F.H. Smith, M.
Paunovic, and I. Karavanic. 2000. Neanderthal diet at
Vindija and Neanderthal predation: The evidence from
stable isotopes. Proceedings of the National Academy
of Sciences 97:7663–7666.
Richards M.P., B.T. Fuller, and R.E.M. Hedges. 2001. Sulphur
isotopic variation in ancient bone collagen from
Europe: Implications for human palaeodiet, residence
mobility, and modern pollutant studies. Earth and
Planetary Sciences Letters 191:185–190.
Rozanski, K., L. Araguás-Araguás, and R. Gonfiantini.
1993. Isotopic patterns in modern global precipitation.
Pp. 1–36, In P.K. Swart, K.C. Lohmann, J.A. McKenzie,
S. Savin (Eds.).Climate Change in Continental
Isotopic Records. American Geophysical Union,
Washington, DC, USA.
Schoeninger, M.J. 1985. Trophic-level effects on 15N/14N
and 13C/12C ratios in bone collagen and strontium
levels in bone mineral. Journal of Human Evolution
14:515–525.
Schoeninger, M.J. 1995. Stable isotope studies in human
evolution. Evolutionary Anthropology 4:83–98.
Schoeninger, M.J., and M.J. DeNiro. 1982. Carbon isotope
ratios of apatite from fossil bone cannot be used
to reconstruct diets of animals. Nature 297:577–578.
Schoeninger, M.J., and M.J. DeNiro. 1984. Nitrogen and
carbon isotopic composition of bone collagen in marine
and terrestrial vertebrates. Geochimica et Cosmochimica
Acta 48:625–639.
Schwarcz, H.P., and M.J. Schoeninger. 2011. Stable isotopes
of carbon and nitrogen as tracers for paleo-diet
reconstruction. Handbook of Environmental Isotope
Geochemistry, Advances in Isotope Geochemistry
5:725–742.
Schwarcz, H.P, L. Gibbs, and M. Knyf. 1991. Oxygen
isotope analysis as an indicator of place of origin. Pp.
263–268, In S. Pfeiffer and R.F. Williamson (Eds.).
Snake Hill: An Investigation of a Military Cemetery
from the War of 1812. Dundurn Press, Toronto, ON,
Canada.
Journal of the North Atlantic
T.D. Price
2015 Special Volume 7
85
Wright, L.E., and H.P. Schwarcz. 1998. Correspondence
between stable carbon, oxygen and nitrogen isotopes
in human tooth enamel and dentine: Infant diets at
Kaminaljuyú. Journal of Archaeological Science
26:1159–1170.
Tauber, H. 1981. 13C evidence for dietary habits of prehistoric
man in Denmark. Nature 292:332–333.
Ten Cate, R. 1998. Oral Histology: Development, Structure,
and Function. 5th Edition. Mosby-Year Book, Inc,
St. Louis, MO, USA.
Tieszen, L.L., and T. Fagre. 1993. Carbon isotopic variability
in modern and archaeological maize. Journal of
Archaeological Science 20:25–40.
Todt, W., R.A. Cliff, A. Hanser, and A.W. Hofmann. 1996.
Evaluation of a 202Pb-205Pb double spike for highprecision
lead isotope analysis in Earth processes.
Pp. 429–437, In A. Basu, and S. Hart (Eds.). Reading
the Isotopic Code. Geophysics Monograph Series 95.
American Geological Union, Washington, DC, USA.
Tykot, R.H. 2004. Stable isotopes and diet: You are what
you eat. Pp. 433–444, In M. Martini, M. Milazzo and
M. Piacentini (Eds.). Proceedings of the International
School of Physics “Enrico Fermi” Course CLIV. IOS
Press, Amsterdam, The Netherlands.
van der Merwe, N.J. 1982. Carbon isotopes, photosynthesis,
and archaeology. American Scientist 70:596–606.
van der Merwe, N.J. 1992. Light stable isotopes and the
reconstruction of prehistoric diets. Proceedings of the
British Academy 77:247–264.
van der Merwe, N.J., and J.C. Vogel. 1977. 13C content
of human collagen as a measure of prehistoric diet in
woodland North America. Nature 276:815–816.
van Klinken, G.J. 1999. Bone collagen quality indicators
for palaeodietary and radiocarbon measurements.
Journal of Archaeological Science 26:687–695.
Van Strydonck, M., M, Boudin, and A. Ervynck. 2005.
Possibilities and limitations of the use of stable isotopes
(13C and d15N) from human bone collagen and
carbonate as an aid in migration studies. Impact of the
Environment on Human Migration in Eurasia. NATO
Science Series IV: Earth and Environmental Sciences,
42, Section 2:125–135.
Vogel, J.C., and N.J. van der Merwe. 1977. Isotopic evidence
for early maize cultivation in New York State.
American Antiquity 42:238–242.
Waldron, H.A. 1983. On the post-mortem accumulation
of lead by skeletal tissues. Journal of Archaeological
Science 10:35–40.
White C., F.J. Longstaffe, and K.R. Law. 2004. Exploring
the effects of environment, physiology, and diet
on oxygen isotope ratios in ancient Nubian bones and
teeth. Journal of Archaeological Science 31:233–350.
White, C.D., T.D. Price, and F.J. Longstaffe. 2007. Residential
histories of the human sacrifices at the Moon
Pyramid, Teotihuacan: Evidence from oxygen and
strontium isotopes. Ancient Mesoamerica 18:159–172.
Wiedemann, F.B., H. Bocherens, A. Mariotti, A. von den
Driesch, and G. Grupe. 1999. Methodological and
archaeological implications of intra-tooth variations
(δ13C, δ18O) in herbivores from Ain Ghazal (Jordan,
Neolithic). Journal of Archaeological Science
26:697–704.
Wright, L.E. 2005. Identifying immigrants to Tikal, Guatemala:
Defining local variability in strontium isotope
ratios of human tooth enamel. Journal of Archaeological
Science 32:555–566.
Journal of the North Atlantic
T.D. Price
2015 Special Volume 7
86
Initial Preparation
Tooth enamel
The permanent first molar is the preferred tooth for
isotopic analyses both for consistency and the fact that the
enamel of this tooth forms during late gestation and very
early childhood. Teeth are mechanically pre-cleaned by
hand and subsequently repeatedly washed ultrasonically
in ultrapure (MilliQ™) water until the water remains visually
clear. After drying, part of the surface of the tooth is
initially abraded using a dental drill fitted with a diamond
burr to remove contamination. Small pieces of enamel
are removed by means of a small diamond blade saw and/
or with chromium steel pliers. Extreme care is taken to
separate dentin material from enamel. Sample sizes are
about 20 mg of material, with approximately 10 mg for
strontium isotopes, 2 mg of fine enamel powder for enamel
apatite carbon and oxygen isotopes, and the remainder
reserved for possible subsequent analysis. For lead isotope
analysis, an additional part of the tooth is prepared, and
another 30 mg of enamel are removed.
Bone
Most of the carbon and nitrogen isotope measurements
from the North Atlantic human remains were carried
out by other projects and data has been shared. For
bone apatite samples for strontium and lead, a sample of
the exterior and interior surfaces of a section of cortical
bone, weighing from about half a gram to a few grams, is
heavily abraded and then broken into several small pieces
(less than 1 cm). These pieces are placed into a 20-ml glass vial
filled with deionized water and are repeatedly sonicated in
an ultrasonic water bath, replacing any cloudy water with
clean deioinzed water until the water remains clear after
sonication. The samples are sonicated with 5% acetic acid,
and rinsed again with ultrapure deionized water. The bone
chips are then ashed in a muffle furnace at 750–800 °C for
8 hours, and the resulting ash is used for strontium and
lead isotopes.
Carbon and Oxygen in Enamel Apatite
References: Loftus and Sealy 2012, Stephan 2000,
Schwarcz et al. 1991.
Enamel apatite carbonate isotopic analysis (sample
weight = ~700 μg) was performed by reacting the prepared
finely powdered enamel with 100% phosphoric acid in
the presence of silver foil at 70 °C in a Kiel III automated
carbonate reaction device coupled to a MAT 252. Carbon
and oxygen isotope ratios were simultaneously determined
on the CO2 generated by this reaction. The isotope ratio
measurement was calibrated based on repeated measurements
of NBS-19 and NBS-18 and precision is ± 0.1 ‰ for
δ13C and ±0.06‰ for δ18O (1s). The carbonate–CO2 fractionation
for the acid extraction is assumed to be identical
to that of calcite. Replicate analyses of apatite were not
performed. Analytical error on this instrument is ±0.05‰
for δ13C and ±1.0‰ for δ18O (Balasse 2002).
Carbon in Bone Apatite
References: Lee-Thorp et al. 1989.
Bone samples were treated as follows. Carbonate from
apatite samples was extracted using established techniques,
specifically the removal of organic components
using bleach (24 hrs for enamel, 72 hrs for apatite) and
non-biogenic carbonates using buffered 1 M acetic acid
(24 hrs). Carbonate samples were analyzed using a similar
Finnegan MAT Delta Plus XL mass-spectrometer, coupled
with a Kiel III device that produces CO2 gas using 100%
phosphoric acid injected into individual sample containers.
Carbon and Nitrogen in Bone Collagen
References: Ambrose 1990, Chisholm et al. 1983, Grupe
and Piepenbrink 1987, van Klinken 1999.
Sample preparation for the simultaneous measurement
of carbon and nitrogen isotopes in bone collagen generally
follows the procedure described here with minor differences
from lab to lab. Whole and fragmented bone (about
1 g) was first cleaned using ultra-sonic vibration and distilled
water. From the cleaned bone, 10 mg of bone powder
were extracted for apatite analysis. Following initial
treatment with 0.1 M NaOH to remove humic acids, bone
collagen was extracted using 2% HCl for 72 hrs. Following
a second 24-hr treatment with NaOH, residual lipids
were separated with a mixture of methanol, chloroform,
and water. After drying, the collagen was weighed to determine
percent yield, with 1% or more considered reliable
for isotope analyses.
Duplicate 1-mg samples were then weighed into tin
cups, and analyzed using a CHN analyzer coupled with
a Finnigan MAT Delta Plus XL stable isotope ratio mass
spectrometer set up with a continuous flow. The reliability
of isotope measurements was also validated by C and N
gas yields and C:N ratios during processing on the mass
spectrometer, with values between 2.9 and 3.6 considered
equivalent to those found in collagen. The precision of
the analyses is about ±0.1‰ for carbon and ±0.2‰ for
nitrogen. Results are reported relative to the PDB and AIR
standards, respectively.
Strontium Isotopes in Enamel Apatite
References: Bentley 2006, Montgomery 2010, Price et al.
1994a, Slovak and Paytan 2011.
Appendix 1. A brief summary of sample preparation and measurement for these isotopic methods is provided. This information
is widely available in a number of publications as referenced in each section. Samples of tooth enamel are taken
for oxygen, carbon, strontium, and lead. Samples of bone are taken for carbon and nitrogen in collagen. This appendix
first describes the preparation of enamel and bone for analysis and then summarizes the procedures used for isotope ratio
measurement for carbon and oxygen in enamel apatite, carbon and oxygen in bone apatite, carbon and nitrogen in bone
collagen, strontium in enamel and bone apatite, and lead in ena mel apatite.
Journal of the North Atlantic
T.D. Price
2015 Special Volume 7
87
For 87Sr/86Sr, samples weighing approximately 3 mg
were dissolved in 5-molar nitric acid. The strontium fraction
was purified using EiChrom Sr-Spec resin and eluted
with nitric acid followed by water. The eluent was dried,
and the Sr residue was placed on a tantalum filament.
Isotopic compositions were obtained on this strontium
fraction using a VG (Micromass) Sector 54 thermal
ionization mass spectrometer (TIMS) in the Department
of Geological Sciences, University of North Carolina at
Chapel Hill or a VG Sector 54 IT mass spectrometer at
the Isotope Laboratory in the Institute of Geography and
Geology, University of Copenhagen. Regular and repeated
87Sr/86Sr analyses of the NIST 987 (National Institute of
Standards, Standard Reference Material) strontium carbonate
yielded a value of 0.710259 ± 0.0003 (2 SE). Internal
precision (standard error) for the samples is typically
0.000006–0.000010, based on 100 dynamic cycles of data
collection. Total procedural blanks for strontium typically
were below 100 picograms, which is insignificant relative
to the amounts of strontium in the samples.
Lead Isotopes in Apatite
References: Budd et al. 1999, 2000; Carlson 1996; Gulson
et al.1997.
Samples weighing 15–30 mg are placed into 7-ml Teflon
beakers (Savillex™), and are then dissolved in a 1:1
mixture of 0.5 ml 6 N HCl (Seastar) and 0.5 ml 30% H2O2
(Seastar). The samples are typically decomposed within
5–10 minutes, after which the solutions are dried down on
a hotplate at 80 °C.
Enamel samples were taken up in a few drops of a
3:1 mixture of 1.5N HBr and 2N HCl and then loaded on
disposable mini extraction columns (1-ml pipette tips with
a fitted frit at the bottom) charged with 0.1 ml intensively
pre-cleaned mesh 100 anion resin (BioRad AG 1x8). The
elution recipe essentially followed that described by Frei
and Kamber (1995), tailored to the small size of the herein
used extraction columns. Lead samples were dissolved in
2.5 ml of a 1 M H3PO4 and loaded together with a silica
gel activator onto previously outgassed 99.98% single rhenium
filaments. Samples were measured at 1100–1200 °C
in static multi-collection mode on a VG Sector 54 IT mass
spectrometer equipped with 8 faraday detectors (Institute
of Geography and Geology, University of Copenhagen,
Denmark). Repeated analyses of 10-ng loads of the NBS
981 Pb standard were used to control the mass bias of the
sample analyses. Mass fractionation amounted to 0.103%
/ AMU (atomic mass unit) relative to the values for this
standard reported by Todt et al. (1996). Total lead procedure
blanks were ~50 picograms. These amounts are insignificant
relative to the total amounts of lead in a sample,
and therefore blank corrections were not undertaken.