Archeo Micromorphology

Micromorphology
Archeo
Figure 1: aerial photo with
indication of the sites where Dark
Earth has been discovered.
Integrating micromorphology and
phytolith studies to investigate medieval
Dark Earth: the example of Brussels
Authors
Y. Devos, L. Vrydaghs
A lthough
Figure 2: Petite rue de
Bouchers. Sampling of a Dark
Earth for micromorphology
and phytolith analysis.
Figure 3: different phytolith
distribution patterns: A:
isolated; B: clustered; C:
contiguous. Their distribution
contributes to the
understanding of taphonomic
processes.
Figure 4: Hôtel d’Hoogstraeten. Units 7321 and 7338 have been
identified as remains of ancient crop fields. The high textural similarity
of the units 7321, 7338 and 7341 indicates that units 7321 and 7338 are
not a dump of new material, but the result of reworking of units 7338
and 7341 consecutively (A). The absence of laminations both on macroand micro-scale, the random distribution of the highly fragmented
anthropogenic elements and the presence of dusty humiferous
clay-coatings (B), point towards a thorough mixing/reworking of a
topsoil. The phytolith study of reveals the presence of Avena sp. and
Triticum sp. and/or Hordeum sp. (C). The phosphate data show
enhanced values for units 7321 and 7338 (E). In combination with the
presence of coprolithic material (D) they suggest fertilisation of the
initially poor soil.
thick, dark, humiferous, macroscopically homogeneous
units, also known as Dark Earth, are an important part of the urban
stratigraphy, their understanding often remains problematic. Last
decades, however, interdisciplinary studies have demonstrated their
huge archaeological potential. Especially micromorphology (fig. 2)
has proven to be of great value to understand the formation processes
of these homogeneous units (MACPHAIL, 1994; CAMMAS, 2000;
MACPHAIL & LINDERHOLM, 2004; NICOSIA, 2006). More recently,
through the study of the Brussels Dark Earth, the integration of
phytolith studies and micromorphology has proven to be of
particular interest to investigate archaeological layers such as Dark
Earth, where other botanical remains are often poorly preserved
(DEVOS et al., 2009; DEVOS & VRYDAGHS, 2009). The integration of
both approaches allows to understand the basic distribution and
orientation patterns of the phytoliths and their relation to other
features/fabrics (fig. 3), contributing to a better understanding of
taphonomical processes and the identification of different human
activities behind Dark Earth formation.
The integrated study demonstrates that the formation of the Dark
Earth results from multiphased processes, whereby various human
actions interact with natural phenomena. Among the human activities
pasturing (fig. 5), agriculture (fig. 4), digging, destruction, dumping of
debris, tramping and middening have been identified. Main natural
factors are bioturbation, erosion, sedimentation and soil development.
Obviously part of them are human induced (e.g. enhanced earthworm
bioturbation, due to a change in soil properties created by the addition
of soil amendments). As a matter of fact the formation and
transformation of Dark Earth is an ongoing process of accumulation,
erosion / truncation, decomposition and homogenisation that stops
once the Dark Earth gets sealed (fig. 6).
Considering that Dark Earth results from variable sequences of
activities and natural phenomena, it needs to be investigated on an
individual basis. Only the systematic application of a specific research
protocol might allow to identify the social and natural events driving
the formation of the Dark Earth.
Bibliography
CAMMAS C., 2000. Apports et perspectives de l’analyse micromorphologique des “terres noires”.
In: Terres Noires – 1. Maison des sciences de la ville, de l’urbanisme et des paysages, Tours,
pp. 45-60. (= Documents Sciences de la Ville, 6, 2000).
DEVOS Y. & VRYDAGHS L., 2009. Micromorphology and Opal Phytolith Studies on Thin Sections
on Medieval Sites in Brussels (Belgium). Frankfurter geowiss. Arbeiten, 30: 25-33.
DEVOS Y., VRYDAGHS L., DEGRAEVE A. & FECHNER K. 2009: An archaeopedological and
phytolitarian study of the “Dark Earth” on the site of Rue de Dinant (Brussels, Belgium). Catena,
78: 270-284.
MACPHAIL R.I., 1994. The reworking of urban stratigraphy by human and natural processes. In:
HALL A.R. & KENWARD H.K. (eds.), Urban-rural connexions: perspectives from environmental
archaeology. Symposia of the Association for Environmental Archaeology No. 12. Oxbow, Oxford,
pp. 13-43. (= Oxbow Monograph, 47).
Figure 5: rue de Dinant. The presence of roots, the very high porosity, the
abundant excremental organo-mineral micro-aggregates and the presence
of sparitic biospheroids point to heavy bioturbation by plant roots and
earthworms. In combination with slightly enhanced phosphorus levels
these remains are probably witnessing old pasture land.
MACPHAIL R.I. & LINDERHOLM J., 2004. “Dark Earth”: recent studies of “Dark Earth” and
“Dark-Earth-like” microstratigraphy in England, UK. In: VERSLYPE L. & BRULET R. (eds.), Terres
Noires – Dark Earth. Actes de la table ronde internationale tenue à Louvain-la-Neuve, les 09 et 10
novembre 2001. Université Catholique de Louvain, Louvain-la-Neuve, pp. 35-42. (= Collection
d’archéologie Joseph Mertens, XIV).
NICOSIA, C., 2006. Archaeopedological study of medieval ‘Dark Earth’ from Firenze, Italy. Unpublished
M.Sc. thesis, University Ghent.
Contacts
Y. Devos
Centre de Recherches en
Archéologie et Patrimoine,
Université Libre de Bruxelles,
Avenue F.D. Roosevelt, 50, CP
175, B-1050 Brussels, Belgium,
[email protected]
Acknowledgements
This research was funded by the
Brussels Capital Region. The
authors want to thank the
Direction of Monuments and Sites
of the Brussels Capital Region for
the fruitful collaboration.
L. Vrydaghs
Research Team in Archaeo- and
Palaeosciences, Avenue H. de
Brouckère, 82, B-1160 Brussels,
Belgium,
[email protected]
Figure 6: scenario on Dark Earth formation in Brussels.
2011