2009 International Nuclear Atlantic Conference - INAC 2009
Rio de Janeiro,RJ, Brazil, September27 to October 2, 2009
ASSOCIAÇÃO BRASILEIRA DE ENERGIA NUCLEAR - ABEN
ISBN: 978-85-99141-03-8
ARCHAEOLOGICAL POTTERY FRAGMENTS ANALYSIS FROM
SAMBAQUI DO BACANGA (MA-BRAZIL) WITH A PORTABLE
EDXRF SYSTEM
Renato A. Ikeoka1, Carlos R. Appoloni1, Paulo S. Parreira1, Fábio Lopes1,
Arkley M. Bandeira2
1
Departamento de Física/CCE
Universidade Estadual de Londrina
Cx.Postal 6001
CEP 86051-990 Londrina/PR – Brazil
[email protected]
2
Museu de Arqueologia e Etnologia
Universidade de São Paulo
Av. Prof. Almeida Prado, 1466
CEP 05508-900 - Cidade Universitária - São Paulo/SP – Brazil;
[email protected]
ABSTRACT
“Sambaqui do Bacanga” archaeological site is located in the Island of São Luis - Maranhão – Brazil, in the
region bathed by the Bacanga River. A stratigraphic collection of 68 pottery fragments was collected during the
years 2005 and 2006 to perform a qualitative analysis of the chemical elements employing a Portable System of
Energy Dispersive X-ray Fluorescence (PXRF). The elements K, Ca, Ti, Mn, Fe, Zn, Br, Rb, Sr, Y, Zr and Pb
were identified in the different fragments and only Fe, Ca, Sr, Zr, Mn, Ti and Zn were common elements for all
of them, indicating that these elements are present in the raw material used in the manufacture of the fragments.
Only one fragment presented remains of painting. A larger concentration of Fe was observed in this region
compared to other areas. This indicates that a material with iron oxide was used to make the painting. The
elements Fe, Sr, Mn, Ti and Zn are present, systematically, with larger intensities on concave and convex sides
in relation to the ceramic paste for 43 among the 68 analyzed fragments, indicating a different surface treatment
that leads to an enrichment of those elements. Cluster analysis was performed with the pottery fragments at
three levels. The fragments were grouped in three different clusters, except for two fragments from the 132 cm
level, which grouped with the fragments from 10-20 cm level. This result indicates three different sources of
clay for the studied pottery fragments.
Keywords: PXRF, Portable X-ray Fluorescence, Archaeological Pottery, Archaeometry.
1. INTRODUCTION
In the State of Maranhão - Brasil, where there is not enough archeological information
available to constitute a minimal picture of the pre-colonial occupations in the territory, a
research project is being developed for the first time. Its name is “Sambaqui do Bacanga at
Ilha de São Luís-Maranhão: a study on the ceramic occurrence in the archeological
records” [1].
In the archeological excavations in Sambaqui do Bacanga, several types of material vestiges
have been evidenced, like fire remains, human skeletons, remains of animal bones, fish
remains, shells, mollusk shells and ceramic objects. Ancient civilizations that inhabited that
territory were characterized by being fishing populations - catchers – hunters and ceramists,
who settled down in the region around 6,600 years ago and remained inhabiting the place till
the year 900 of our era [1].
Amidst all such material culture, ceramics are highlighted as objects of highly archeological
value because they are extremely resistant to weather and environment conditions [2].
The chemical characterization of such fragments may provide important information about
the origin of the raw material, the quality of the coating, indexes of the occurrence of
paintings, etc., which help the archeological studies about the peoples in that region. Thus,
the Energy Dispersive X-Ray Fluorescence technique (EDXRF) was used in the
identification of the chemical elements that constitute the ceramics. As it is a
multi-elementary, simultaneous and non-destructive technique, the EDXRF has been gaining
a great deal of importance in archeological studies [3-7].
The pottery fragments were analyzed by using a Portable System of Energy Dispersive
X-Ray Fluorescence (PXRF) with the aims of verifying the existence of painting vestiges in
the fragments, as well as if there is some kind of treatment in the concave and convex sides in
relation to the ceramic paste of the fragments and finally, using grouping analysis to check
the similarity among the chemical elements identified in the fragments not only with the same
stratigraphic level but also with different levels.
2. MATERIALS AND METHODS
2.1. Description of the Samples
The pottery fragments were collected in an archeological site in Sambaqui do Bacanga,
located in the Bacanga National Park in Ilha de São Luis – MA.
A stratified collection of 68 pottery fragments was conducted. The provenance of such
fragments are the following sectors: Exploratory Trench, Excavation Area 1, Profile 1 and
Profile 2, as the following tables 1 to 4 show.
Table 1. Information about fragments in sector Exploratory Trench.
Sample
Sample 03
Sample 09
Sample 20
Sample 15
Sample 05
Sample 12
Sample 17
Sample 18
Sample 07
Sample 01
Total
INAC 2009, Rio de Janeiro, RJ, Brazil.
Quantity of fragments
01
02
11
02
01
03
03
02
08
01
34
Stratigraphic levels (cm)
Surface
Surface
Surface
125
128
128
135
138
144
150
07
Table 2. Information about fragments in the sector Excavation Area 1.
Sample
Sample 02
Sample 10
Sample 11
Total
Quantity of fragments
01
03
02
06
Stratigraphic level (cm)
Surface
Surface
Surface
01
Table 3. Information about fragments in sector Profile 1.
Sample
Sample 04
Sample 14
Sample 06
Sample 22
Sample 21
Sample 19
Sample 08
Total
Quantity of fragments Stratigraphic levels (cm)
01
0–8
02
10 – 20
01
80
04
113
07
125
06
132
03
140
24
07
Table 4. Information about fragments in sector Profile 2.
Sample
Sample 13
Sample 16
Total
Quantity of fragments
02
02
04
Stratigraphic levels (cm)
30 – 35
40
02
Table 5 shows the description of the sectors excavated in Sambaqui do Bacanga.
Table 5. Sectors excavated in Sambaqui do Bacanga.
Excavation sector
Elevation variation
(m)
Excavation area
(m2)
Excavation area 1
Exploratory Trench
Profile 1
Profile 2
74
72
72
70
20
16
4,45
3
INAC 2009, Rio de Janeiro, RJ, Brazil.
2.2. EDXRF Portable System
The EDXRF (PXRF-LFNA-02) portable system utilized for irradiation/detection of the
fragments consists of a 4W X-ray mini-tube with Ag anode and 50 µm Ag filter
(Moxtek, Inc.); a Si-PIN detector with pre-amplifier XR-100CR (AMPTEK Inc.), 221 eV
FWHM for the 5.9 keV Mn line, 25 μm Be window and thermoelectric cooling system by
Peltier Effect; PX2CR conjugated high tension source module and amplifier (AMPTEK Inc.);
multichannel analyzer model MCA8000A (AMPTEK Inc.); an excitation-detection system
positioning module with freedom degrees XYZ and rotation in relation to the analyzed
sample; and a notebook for data acquisition and storage. Fig. 1 shows the system used to
carry out the measurements.
Measurement conditions were 28 kV and 5 μA in the X-ray mini-tube and acquisition time
was 500 seconds.
Figure 1. X-ray Fluorescence Portable System: (1) Sample carrier, (2) X-ray Mini-tube,
(3) X-ray non-cryogenic detector, (4) Standard electronic equipment and (5) Notebook.
In average, nine measurements were made for each fragment, three of which in the concave
face, three in the convex face and three in the ceramic paste. The analysis of the spectra was
conducted by using the software Quantitative X-Ray Analysis (WinQXAS), distributed by
the International Atomic Energy Agency (IAEA).
For the analyses of the data obtained with WinQXAS, only the intensities of the chemical
elements whose net areas were threefold higher their standard deviation were considered.
3. RESULTS AND DISCUSSION
It was possible to observe the elements K, Ca, Ti, Mn, Fe, Zn, Br, Rb, Sr, Y, Zr and Pb in the
different fragments analyzed. The statistical deviations of those determinations were, in
INAC 2009, Rio de Janeiro, RJ, Brazil.
general, 1% for Fe, 5% for Ca, from 5 to 10% for Sr, Zr, Mn, Ti and Zn, and from 20 to 25%
for K, Br, Rb, Y and Pb.
The elements Ca, Ti, Mn, Fe, Zn, Sr and Zr appeared in the ceramic paste of all the 68
analyzed fragments, indicating that such elements are present in the constitution of the clay
used in the manufacture of these ceramics.
The elements Fe, Sr, Mn, Ti, and Zn presented systematically higher intensities in the faces in
relation to the ceramic paste in 43 out of the 68 analyzed fragments, indicating that there is a
treatment in the faces, with enriching for those elements, which is the engobe. This behavior
is shown in Figures 2 to 5, which refer to element Fe in the Exploratory Trench, with
exception of sample 20; Ti in Excavation area 1, with exception of sample 10.1; Zn of
Profile 1, with exception of samples 21 and 22; and Sr of Profile 2, respectively.
By analyzing sample 3, which is the only fragment where painting vestiges can be visualized
in both sides, it is possible to notice that the concave and convex faces have more Fe
concentration in these regions with painting vestiges in comparison with the regions of the
same faces without painting. This behavior is shown in Figure 2, in which, on the left, there is
a rectangle separating sample 3 from the other samples in this sector. The measurements
carried out in the region without painting are in the spots on the left, and the measurements
carried out in the region with painting are in the spots on the right.
Fe
Convex
Paste
Concave
Sam.3
900
Sam.7
Sam.20
800
Intensity (cps)
700
Sam.12 Sam.17
Sam.15
Sam.18
Sam.5
Sam.9
Sam.1
600
500
400
300
200
100
0
0
4
8
12
16
20
24
28 32 36 40 44 48 52
Sample
Figure 2. Graph of Fe intensity for the samples in the Exploratory Trench, in which the
samples are separated in different stratigraphies and the number of fragments is in
brackets: surface {samples 3(1), 9(2) e 20(11)}, 125 cm {sample 15(2)}, 128 cm {samples
5(1) and 12(3)},135cm {sample 17(3)}, 138 cm {sample 18(2)}, 144 cm {sample 7(8)} and
150 cm {sample 1(1)}.
INAC 2009, Rio de Janeiro, RJ, Brazil.
Ti
Convex
Paste
Concave
20
Sam. 10.3
18
Sam. 11.2
Intensity (cps)
16
Sam. 2
Sam. 10.2
Sam. 11.1
14
12
Sam. 10.1
10
8
6
4
2
0
0
1
2
3
4
5
6
Sample
7
8
9
10
11
Figure 3. Graph of Ti intensity for the samples in the sector Excavation area 1, in which
all the pottery fragments are from the surface.
Zn
Convex
Paste
Concave
12
Sam. 22
10
Sam. 21
Intensity (cps)
8
Sam. 19
Sam. 14
Sam. 6
Sam. 8
6 Sam. 4
4
2
0
0
2
4
6
8 10 12 14 16 18 20 22 24 26 28 30 32 34 36
Sample
Figure 4. Graph of Zn intensity for samples from Profile 1, in which the samples are
separated in different stratigraphies and the number of fragments is in brackets:
sample 4(1) – 0 to 8 cm, sample 14(2) – 10 to 20 cm, sample 6(1) – 80 cm, sample 22(4) –
113 cm, sample 21(7) – 125 cm, sample 19(6) – 132 cm and sample 8(3) – 140 cm.
INAC 2009, Rio de Janeiro, RJ, Brazil.
Sr
Convex
Paste
Concave
55
Sam. 16.1
50
45
Intensity (cps)
40
35
Sam. 13.1
Sam. 16.2
30
25
20
Sam. 13.2
15
10
5
0
1
2
3
4
5
6
Sample
Figure 5. Graph of Sr intensity for samples in Profile 2, in which the samples are
separated in different stratigraphies and the number of fragments is in brackets:
sample 13(2) – 30 to 35 cm and sample 16(2) – 40 cm.
By applying cluster analysis in the study of the pottery fragments of stratigraphies 10 to
20 cm, 132 cm to 144 cm, it was possible to observe the formation of three distinct groups for
the fragments of the three stratigraphies, apart from two fragments of the 132 cm
stratigraphy, which stayed in the same group of the fragments of stratigraphy 10 to 20 cm, as
seen in Figure 6. This result indicates that the analyzed fragments were manufactured with
clay from three different origins.
Figure 6. Dendogram with pottery fragments excavated in three stratigraphies, 10 to 20
cm (represented as 20 cm), 132 cm and 144 cm, the last algarism from left to right in the
sample code represents the sample number.
INAC 2009, Rio de Janeiro, RJ, Brazil.
4. CONCLUSIONS
Utilizing an EDXRF portable system to analyze pottery fragments collected in an
archeological site in Sambaqui do Bacanga, it was possible to observe that the basic elements
in the constitution of the clay used to manufacture these fragments were Fe, Ca, Sr, Zr, Mn,
Ti and Zn. It could also be noticed that a material with high iron concentration was possibly
used in the painting to give the red colour, which was found only in one of the samples.
Out of the 68 pottery fragments analyzed, 43 presented a different treatment on the faces in
relation to the ceramic paste. It means that on these 43 fragments it was applied engobe,
which is a kind of clay enriched with the elements Fe, Sr, Mn, Ti, and Zn. This more refined
material is characterized by forming a concentration increase of such elements in the faces
when the ceramics are burnt in the manufacturing process.
From the cluster analysis of the pottery fragments of three stratigraphies, the formation of
three groups was observed. This result indicates that the fragments analyzed were
manufactured with clay from three different origins.
ACKNOWLEDGMENTS
To Fábio Luiz Melquiades and Wislley Dueli da Silva for their collaboration in the sample
measurements, and to CNPq for the scholarship awarded during the MA Course.
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INAC 2009, Rio de Janeiro, RJ, Brazil.