Lacasa-Marquina et al., 2014: IN SITU CONSERVATION STRATEGIES
archeological level [X-ray Diffraction analysis
and after burial ­ for understanding the
(XRD)] indicates the presence of two principal
dynamic of degradation of sub-fossil bones.
minerals, quartz and calcite, whereas kaolinite
Thus, the study of the state of preservation of
is detected in a smaller proportion (Sahnouni,
the remains is based on the examination of
1998). Additionally, the stratigraphic evidence
their nature and properties in correlation with
based
on
the
sedimentary
matrix,
the
the geological and sedimentary context, as well
taphonomic conditions of the bones and the
as on the sub-aerial environmental conditions.
spatial
disposition
of
the
archeological
The analysis for the identification of exogenous
materials, show that the archeo-paleontological
agents of deterioration during biostratinomic
remains were buried in primary context and
and diagenetic processes has been performed
were minimally disturbed (Sahnouni et al.,
by consulting the published literature dealing
2013). Likewise, the bone weathering patterns
with the geology and archeology at Ain Hanech.
do
not
infer
long
sub-aerial
exposure,
The analysis of climate dynamics has been
suggesting that the depositional process prior
carried out over the 2012 annual period and,
to burial was relatively short, less than three
more specifically, during the fieldwork season
years (Sahnouni and de Heinzelin, 1998).
(23
rd of June -10th of July). The reference data
However, the majority of the sub-fossil bones
of temperature (T), relative humidity (RH) and
are fractured caused by both biostratinomic and
precipitation rate (RRR) were taken from the
postdepositional
taphonomic
processes.
weather station of Sétif International Airport,
Taphonomic evidence indicates that early
located 30 km southwest from El-Kherba. The
hominins were largely responsible for the
recorded daily data cover a sampling interval of
modification of animal bones (Sahnouni et al.,
every three hours during a period of one year
2013), but other factors such as sediment
representing the natural oscillation cycles:
compaction could be responsible for their
daily, seasonally, monthly and yearly (Table 1).
degradation during burial.
Despite that the distance between the weather
station and the archeological site may imply a
MATERIALS AND METHODS
slight variation of the climatic parameters, we
must consider it as an initial approach to
The
definition
and
implementation
of
understand
the
environmental
regional
conservation strategies required a preliminary
dynamics. Besides, it can be regarded as an
analysis of the state of preservation of a bone
immediate and preliminary technique before
sample representative of the typical dynamic of
develop in situ technical facilities in order to
degradation at the site of El-Kherba.
obtain a more detailed study.
The quantitative data have been processed for
undertaking a statistical analysis based on
Sample
statistical variables and the interpretation of
The studied sub-fossil sample comprises 24
graphic representations. Characterization -
bone specimens excavated from level B during
average ­ and dispersal parameters to deduce
the 2012 fieldwork season. According to Collins
disturbances
and
evaluate
the
(1988), a sub-fossil bone is a bone that has
representativeness of the data ­ maximum,
been subject to sub-aerial weathering and then
minimum,
oscillations
and
standard
burial, but has not been subjected to any
deviations.­ have been obtained with the aim
secondary mineralization (Shelton and Johnson,
of determining the environmental conditions,
1995). The selection sample was based on the
and verifying if these climatic parameters are
vulnerability degree of the specimens against
within the proper range of preservation of the
the external climate degradation agents, and
sampled sub-fossil remains (Pastor, 2013).
on the technical complexity of the strategies
Likewise, the graphical representation of the
that had to be developed for recovering them
data has been performed by time-series graphs
and ensure their preservation. The sample
and histograms. These graphs allow us to
includes
12
axial
skeleton
(50%),
six
detect climatic parameters outside the optimal
appendicular (25%), and six undetermined
preservation range and to quantify the
bones (25%).
relevance of these extreme values.
The second phase consists of defining and
Methods
implementing remedial conservation strategies,
The methodology includes two interrelated
in order to arrest or minimize the potential risk
phases. The first phase consists of analyzing
agents of deterioration, based on the results
the potential alteration risks ­ before, during
obtained in the previous phase.
5
Journal of Paleontological Techniques