extended abstracts - Geomorphic Processes and Geoarchaeology

Geomorphic processes and geoarchaeology
putrefaction of their deads [3].
It should be expected that many of Early Holocene and Pleistocene sites,
particularly in Siberia, still remain fully frozen. Not many of them are so far known, but
in all cases (Zhokhov site, Yana RHS, and Berelekh) they are hosted by ice-rich
deposits [1]. Then, experience of excavating of such sites is limited to these three cases.
Excavation strategies which can be potentially used are determined mostly by (1)
ice-richness of matrix and overlain deposits that is related to their genesis and age and (2)
thickness of the overlain sediments and that of seasonally thaw layer. Excavations are
also affected by the exposition of the area and it’s topography including general
inclination of the surface, and presence of negative land forms.
After frozen matrix deposit is exposed, the excavation strategy consists of three
steps: (1) thawing; (2) drying (by evaporation and drainage); (3) regular excavation of
relatively dry cultural deposits. Steps (1) and (2) require permanent control. Use of forced
thawing for archaeological purposes is possible in a form any controlled heat technology
except for the open fire. However, fast thawing creates too much water and makes the
sediment super water saturated; it looses a volume proportionally to the ice content and
becomes capable to flow. Because of that, forced thawing can be used only if the
excavation can be drained of dried out quickly, before slump of thawed area. Most likely
this can be done if the host sediment is not deep frozen and has low ice content.
Ice-rich deposits are best to be excavated under natural conditions of summer
insulation and evaporation forced by atmospheric heat and breeze. Certainly, an
excavation of frozen sites involves routine archaeological principals. Sewing of the
excavated matter is important for the Stone Age archaeology, but for frozen sites it has to
be substituted by water screening with low pressure pump.
Obviously, excavations organized from the day light surface (if there is no
erosional land form from which margin the excavation can be started) are the hardest case
because of the drainage problem. In that case, a sort of caisson (or bore hole) to collect
the water could be recommended, and water can be pumped out then. In any case, initial
activity on the excavation will be slow depending mostly on the speed of drying of
thawed sediments. After a part of the area becomes excavated, work goes faster because
there is some space to manage the drainage and drying of the excavation. In some cases
walls of the excavation require additional support in a form of falsework.
The open area has to be relatively extensive, which allows having one third of it
for thawing, another one for drying, and the last one under excavation itself. Multiple
repeating these operations and taking turns of activities in different parts of the
excavation allows excavating cultural deposits down to the bottom. Depending on
weather conditions, this allows to excavate 5-10 cm of the total thickness per a day.
Similar strategy was successfully used in Zhokhov island site, which resulted in
excavating of about 500 m 2 , with a total thickness of cultural deposits up to 3 m [1].
Importantly in the most of the site area there is almost no overlying sediments.
Different scenario for excavations of the frozen sites is applicable for excavations
of the sites with a thick cover of overlain deposits, with a thickness much greater than
that of the active layer. Some kind of the erosional land form is necessary to start this
kind of the excavations. Thus, in Yana RHS the excavation was started from the frozen
river bank exposure [1, 2]. Here the overlain deposits have a thickness of about 7-8 m.
Most of it is frozen, except for the active layer which is less than 1 m thick. These
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