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9
XII/1/2021
INTERDISCIPLINARIA ARCHAEOLOGICA
NATURAL SCIENCES IN ARCHAEOLOGY
homepage: http://www.iansa.eu
Petrography and Micromorphology Face-to-Face: the Potential
of Multivocality in the Study of Earth-Based Archaeological Materials
Susanna Cereda
1*
, Pamela Fragnoli
2
1
University of Innsbruck, Institute of Archaeologies, Langer Weg 9-11, 6020 Innsbruck, Austria
2
Austrian Archeological Institute, Austrian Academy of Sciences, Franz Klein-Gasse 1, A-1190 Wien, Austria
1. Introduction
The implementation of techniques frst developed in the feld of
geology or soil science to answer questions of archaeological
relevance is not a novelty. After all, soils and sediments (from
the fne clayey fraction to rocks) are a main component of
any archaeological site. This omnipresent element can be
found in a myriad of forms, and one of the most common –
at least from the onset of this technology – is pottery. Using
the same concepts and methods established for the study
of rocks, ceramic petrography cuts thin sections through
the body of vessels in order to study the nature and spatial
arrangement of both their coarse and fne components (Quinn,
2013). Even more abundant than pottery is the sedimentary
fabric that composes the body of a site, and that derives
primarily from constructed, collapsed or levelled buildings.
The microscopic analysis of these sedimentary sequences is
called micromorphology, and since the 1980s it has gained
increasing attention in archaeology (Courty and Fedorof,
1982; Goldberg, 1979; Goldberg, 1980; Stoops, 1984).
Although converging on the type of studied material
and also on the wide adoption of optical microscopy for
the observation of their samples, micromorphology and
ceramic petrography are treated as two separate felds, since
they aim at clarifying diferent aspects of past societies.
Ceramic petrography deals with synthetic artefacts produced
by humans through a specifc sequence of operation (the
so-called
chaîne opératoire
) in order to shed light on ancient
technological behaviour and exchanges. Micromorphology
looks at the microstratigraphy of a site in order to assess what
events/agencies led to the deposition of a sequence and what
post-depositional processes afected the stratigraphy. While
the diference inherent in the research questions is clear, the
distinction based on the type of materials analysed might be
ambiguous and artifcial. This concern, for example, earth
construction materials, such as mudbricks, adobe, plaster,
daub, concrete and mortars that ft both defnitions, being as
Volume XII ● Issue 1/2021 ● Pages 9–18
*Corresponding author. E-mail: Susanna.Cereda@uibk.ac.at
ARTICLE INFO
Article history:
Received: 14
th
September 2020
Accepted: 3
rd
March 2021
DOI: http://dx.doi.org/10.24916/iansa.2021.1.1
Key words:
earthen materials
polarising microscopy
micromorphology
ceramic petrography
tell sites
Arslantepe
ABSTRACT
Soils and sediments are among the most commonly found materials in archaeological contexts,
occurring in a myriad of forms. We need only think of pottery, which is a manipulated and fred
sediment, or the diferent earthen deposits that compose the bulk of many sites. Traditionally, the
study of the microscopic and compositional characteristics of pottery has been the focus of ceramic
archaeometry, while the microstratigraphic analysis of archaeological sediments was always the main
task of geoarchaeology. In this paper, the authors explore the potential of a closer collaboration between
researchers dealing with the same type of raw material and often using the same methods (optical
microscopy), who rarely confront the approaches and expertise of the other feld. For this purpose,
two samples belonging to the pre-historic and early historic site of Arslantepe were selected for
a methodological exercise: a fragment of an andiron and a piece of a double-vaulted oven. Ultimately,
the results of this work demonstrate that researchers from both felds can proft from a more intense
exchange: one that takes advantage of the expertise developed in answering distinct but complementary
research questions, and calls for the blurring of strict inter-disciplinary boundaries.
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IANSA 2021 ● XII/1 ● 9–18
Susanna Cereda, Pamela Fragnoli: Petrography and Micromorphology Face-to-Face: the Potential of Multivocality
in the Study of Earth-Based Archaeological Materials
10
they are the result of human recipes, but at the same time
parts of living spaces that often require a microstratigraphic
analysis as well. As a result, earth construction materials
are invariably handled in the handbooks of both ceramic
petrography and micromorphology (Karkanas and Goldberg,
2018; Macphail and Goldberg, 2017; Nicosia and Stoops,
2017; Quinn, 2013), even though scientifc papers on single
case-studies show a prevalence of micromorphologists.
In contrast, some other clay-based artefacts, such as
loom weights, spools and andirons, are mostly studied by
ceramic petrographists, but would strongly beneft from a
micromorphological perspective as they are items closely
interconnected with the domestic sphere.
2. Are four eyes better than two?
Although there is a wide range of archaeological fndings that
interest both ceramic petrographists and micromorphologists,
attempts at data integration rarely occur and are typically
limited to discussions about the adoption of common
standardised descriptive terminologies (Josephs, 2005;
Whitbread, 1995). The ambivalent distance/proximity
between these felds was particularly striking for the authors
of this paper because of their mutual involvement in the study
of earthen materials at Arslantepe (Figure 1), a 30 m high
tell located in the south-east of Turkey, next to the modern
city of Malatya. The site, occupied from approximately the
5
th
millennium BCE to the Byzantine period (4
th
–6
th
century
CE), has been the object of systematic excavations carried
out annually for more than 50 years by a team led by “La
Sapienza” University of Rome (Frangipane, 2011). The long
and complex occupation sequence of the site allowed the
recovery of large amounts of material culture that is studied
by several classes of specialists, including – as mentioned
before – the two authors of this contribution.
At Arslantepe, Pamela Fragnoli analysed, using thin-
section petrography and bulk geochemistry, vessels and
Figure 1.
Satellite image of Turkey (a). The black box indicates the location of the Malatya Basin, where the site of Arslantepe arises; b) Aerial photograph
of the tell-site of Arslantepe, surrounded by cultivated land (mainly apricot orchards); c) Absolute chronology of Arslantepe. Modifed from Vignola
et al.
(2017) and with new data from Manuelli (2018). Images from MAIAO archive.
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in the Study of Earth-Based Archaeological Materials
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clay-based artefacts dating from the Late Chalcolithic period
to the Middle Iron Age (ca. 4700–712 BCE). Her main
aim has been to explore: 1) changes and continuity in raw
material procurement patterns and paste preparation modes
in relation to the emergence and collapse of the centralised
economy; 2) multi-scaled phenomena of mobility ascribable
to pastoral communities; 3) relations between socio-
economic complexity, standardisation and specialisation
(Fragnoli, 2018; Fragnoli, 2019a; Fragnoli, 2019b; Fragnoli
and Palmieri, 2017). Susanna Cereda has instead focused
on the micromorphological analysis of earthen surfaces
in buildings and open areas in order to reconstruct their
microstratigraphy. The main aspect she explored in her
investigations was how people engaged with their built
environment in terms of its construction, maintenance and
use (Cereda, 2019a; Cereda, 2019b; Cereda, in press).
Along with the many shared features connected with
their work at the same site (
e.g.
landscape, environment
and raw materials) both Fragnoli and Cereda had included
in their research common fndings such as either building
materials (cob, freplaces) or objects (andirons, loom
weights), which fall into the above-mentioned category
of earthen products that pertain to both felds of study,
i.e.
ceramic petrography and micromorphology. This series
of favourable circumstances provided the opportunity for
a closer exchange, which in turn encouraged a self-refection
on disciplinary and inter-disciplinary boundaries.
The result of this exchange is the present pilot study on
a few selected earth-based fndings from Arslantepe, the main
aim of which is to assess to what extent the collaboration
between ceramic petrographists and micromorphologists
might not only be fruitful, but also bring out new research
questions and ways of looking at archaeological fndings
and past human communities. We intend to demonstrate
that the integration of data and observations is especially
fundamental in archaeological tell sites, where earth and
soils could accumulate over millennia and be exploited for
craft and domestic activities. Ultimately, this methodological
exercise intends to boost the exchange of ideas between the
diferent specialists of the so-called archaeological sciences
and enhance interdisciplinarity within interdisciplinarity,
in order to think “holistic” beyond any hierarchisation of
knowledge (Morin, 1999).
3. Materials, methods and questions
For the scope of this contribution, two samples were
selected. They belong to diferent contexts and periods, but
they were chosen because they belong to the aforementioned
“in-between” categories of earth-based fnds. To make
the experiment more meaningful and stress the element
of inter-disciplinary distance, each author was assigned
the type of material she was less familiar with. Fragnoli,
the petrographist, was given the construction material
(Figure 2): the surface located in the immediate vicinity
of a double-vaulted oven (sample 119/16). Cereda, the
micromorphologist, was assigned the clayey object: sample
205/15 from the andiron (Figure 2b).
These items were also selected as usually recurring in
domestic spaces and diferently exposed to fre. The idea is
not to provide a detailed description of the thin sections and
compare the terminologies used by the diferent specialists,
since ceramic petrography already traditionally borrows
the descriptive models of micromorphology (Quinn, 2013;
Whitbread, 1995); it is rather an experiment to see whether
eyes diferently trained might enrich the fnal interpretations
of ancient earth-based fnds.
The specifc questions that the authors of this contribution
asked themselves are: what kind of information would
researchers usually focusing on a specifc product of the
same raw material be able to observe in the artifacts, which
are usually examined by the other specialist? What is the
common ground they both share and what, in contrast, is the
result of the specifcities of their objects of study and of the
research questions that guide their work, which train their
eye diferently? And above all: can these fgures help each
other in the study of earth-based materials?
4. Results
4.1 Fragnoli’s analysis of sample 119/16
Within this sample two main layers could be distinguished
based on textural features, diferent exposures to heat,
minero-petrographic associations, and the presence and type
of organic matter. The lowest layer (Figures 3a–e) is 1 to
4 cm thick and consists of a calcareous, optically-active, clay
matrix rich in clay pellets with sharp boundaries and high
optical density. Among aplastic inclusions the organic matter
predominates both in incidence and size (up to 7 mm/20%),
while minerals are fewer and fner (up to 1.6 mm/5%).
The angular shapes, low sorting degree, clustered spatial
distribution and random-to-discordant orientation patterns
of organic components (Figures 3b–d) suggest that they
were intentionally added to the clay paste as tempering
Figure 2.
Location of sample 119/16, which was collected directly in front
of one of the openings of a double-vaulted oven.
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in the Study of Earth-Based Archaeological Materials
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material. Once decomposed they mostly left rectangular
voids of diferent thickness interpretable as imprints of
stems and leaves of variegated plants. Only a few arcuate
and circular-to-semicircular voids/imprints are ascribable
to agricultural by-products, such as cereal spikelets and
caryopses. The remaining imprints have more undefned,
polylobal-to-polygonal shapes and still contain remains of
dark brown organic matter immersed in an orange, glassy
matrix (dung temper?). The mineral inclusions of the paste
are composed, in order of decreasing incidence, of: micritic
calcite, quartz, plagioclase, limestones, intermediate to
sialic igneous rocks, amphiboles, biotites, and planktonic
foraminifera.
The right part of this lowest layer (Figures 3c–e)
difers from the left one (Figures 3a–b) by the decreased
sorting degree (polymodal vs. bimodal), the coarser paste
(6.5 mm/25% vs. 5.2 mm/15%), the higher incidence of
clay pellets and minerals, the smoother and sharper upper
boundaries, the more continuous and regular thickness,
as well as the evidence of exposure to heat (lower matrix
birefringence and remains of oxidised organic matter).
The above layer (Figures 3f–h) presents a concave shape,
up to 5 cm deep, made of loose rounded-to-subrounded
calcareous clay particles of diferent sizes (ashes?). The clay
particles are mostly isotropic, which indicates an exposure
to heat or fre. The aplastic inclusions reach a maximum
diameter and incidence of 1.76 mm and 7% respectively,
present a unimodal grain-size distribution, and consist of
inclusions of quartz, plagioclase, calcite, limestone, bones,
charcoals, melted phytoliths, vegetal matter, planktonic
foraminifera, and other bioclasts (shell fragments?). The
layer presents signifcant inner variations: upwards, the
compactness, fneness and sorting degree progressively
increase, while they tend to decrease towards the external
sides.
The two layers identifed relate to distinct raw materials and
formation processes. The lower one is the result of a recipe
prepared and shaped through rotation pressure by humans.
This worked material was then partially, briefy and possibly
unintentionally exposed to temperatures lower than 800°C.
The intermediate-to-acidic lavas contained in this layer recur
in the pottery production of the whole sequence (Fragnoli