Beiner & Rabinovich, 2014: BONES AND SEDIMENTS
exposed in the excavation site, the base and
In addition, it has been stated that field
top exhibit fully lacustrine character, with a full
observations in archeological sites show that
cycle of transgressive-regressive oscillation in
preservation of bones is enhanced by the
between (Feibel, 2004:24). A good portion of
presence of calcite and authigenic carbonated
the finds from EEA had a powdery character,
apatite in the matrix sediments (Berna et al.,
flaking
easily
and
requiring
considerable
2004:867). If bones are deposited in calcite-
consolidation before being touched and lifted.
containing layers, similar to the calcareous soils
Chemical analysis will be needed to gain better
of Israel, they may possibly remain stable as
understanding of the situation, but it seems
long as calcite remains (Berna et al.,
likely that the cyclic nature of the sedimentation
2004:879). In Ein Yahav, the depositional
may prove to be one of the main causes of this
environment apparently involves eolian sand
condition.
layering on sediments of fluvial and lacustrine
In contrast, NMO bone-containing sediments
origin with a limestone (calcite) content. This
were deposited mainly in two levels of a
may explain the relatively good preservation of
wetland/floodplain to lake environment. The
the finds from Ein Yahav.
more recent unit 3 consists of a dark grey silt
Taking this information into account, the levels
containing montmorillonite, quartz, pyrite and
of mineralization not only affect the integrity of
calcite, while the earlier unit 4 contains black
the bone, thus influencing preservation of the
argillaceous silt containing also dolomite (Kalbe
finds, but also give us better understanding of
et al., 2013:3). Bones retrieved from this site
the effects of the matrix and the hydrological
are characterized by a dark brown color, similar
system on bone material. Such understanding
to the fluvial sediment of the excavation. They
will help to determine whether finds are
are not intensely mineralized, and exhibit good
suitable
for
dating
analysis
and/or
morphological preservation. In other freshwater
paleoenvironmental studies. Current research
environments, for example from the Rhine River
on fossilization processes emphasizes three
Valley, bones also exhibited lower levels of
main processes: degradation of the organic
change in isotopic phosphate oxygen levels,
component in the bone, mineral accumulation
compared with marine settings (Tütken et al.,
(dark interstitial oxides and oxyhydroxides),
2008:266). This possibly indicates that fewer
and
intake
of
trace
elements
(Kohn,
diagenetic
processes
occur
in
freshwater
2008:3759).
environments, at least compared with marine or
In spite of the high-resolution microscopic
marine-influenced environments. Apparently,
examinations
currently
available,
on-site
the archeological finds were directly deposited
conservation must cope with the actual macro
on the floodplain on the margins of a marshy
aspect of bone conservation. Perhaps an
lake, and covered rapidly by a closely packed,
intermediate medium is required in order to
fine grained sediment when the lake rose
negotiate
between
the
high
detail
of
between 70-65 kya (Kalbe et al., 2013:8). In a
microscopic information on bone degradation
similar manner, NMO bones exhibit excellent
and the external appearance of the bone as
preservation.
exposed during excavations. Conservators need
Berna et al. (2004) propose a process during
to be aware of the relationship between the
which layers of insoluble mineral precipitates
matrix and the bone so as to be able to
are built up within bone pores in repetitive
recommend
appropriate
conservation
manner, the cycles working along with the
procedures. As collagen-extraction for early
hydrological regime to create a process of
DNA studies and other analytical methods
"recrystallization". According to their research,
become
more
and
more
prevalent,
more recent bone tends to be less stable, with
conservation knowledge needs to include better
more
soluble
mineral
components
than
understanding of organic decay in bone
fossilized bone. They postulate that this is due
material.
to the much larger surface area to volume ratio
in fresher bone and a much thinner layer of
ACKNOWLEDGMENTS
crystals (Berna et al., 2004:877). It is not yet
clear how the presence of collagen or other
We would like to thank the participants of the
proteins affects the recrystallization process,
excavations in case studies that we have
but pH conditions below seven tend to promote
described:
Revadim
Quarry,
Nahal
bone dissolution and acids are released when
Mahanayeem Outlet, Erq el Ahmar and Ein
collagen
deteriorates.
In
other
words,
Yahav. The Revadim excavations were directed
deterioration
slows
down
as
diagenesis
by Ofer Marder, in collaboration with Ianir
progresses.
Milevski and Hamoudi Khalaily. Conservation
26
Journal of Paleontological Techniques