Archaeologia Islandica - 01.01.1998, Side 135

Archaeological Sediments and Site Formation at Hofstaðir, Mývatn, NE-Iceland
Sediment Sampling Rationale
and Procedure
1) Layer C4: The layer designated as
C4 has become an important
chronological marker on the site
because of its lateral extent from Area
G to Area D but it is in fact a heter-
ogeneous deposit of variable thickness,
and it should not be assumed that it
accumulated simultaneously in differ-
ent parts of the site, or that the rate at
which it was deposited was continuous
or uniform across the site. In Areas D
and E, extensive cultural layers con-
sisting of grey ash, charcoal, small
bone and egg shell fragments are very
comparable to C4, and are thought to
be a continuation of the same layer. In
Area D, this layer is located above the
so-called Landnám tephra sequence
and a subsequent accumulation of
windblown silt that is typical of
Icelandic andisols. It pre-dates the
construction of the turf structure in
Area D, since it was truncated by the
digging activity that created a sunken
floor at the level of the Hekla-3 tephra
layer, and is underneath the western
wall of this structure.
In order to characterize C4 in this
part of the site and to facilitate its
comparison to the similar layer found
in Areas E and G, two micromor-
phology samples were taken from the
western profile (Ref. 1/1 and Ref. 2/3;
fig.l). Thin section analysis will de-
termine the composition of this layer,
including the relative proportions of
ash, charcoal, bone, shell, phytoliths,
organic residues, sand, silt and clay.
The physical condition, orientation
and distribution of these components
will allow us to make interpretations
about the mode and rate of deposition.
Key features will be the presence or
absence of fine laminae within the
layer, signs of weathering on an ex-
posed ground si^rface, the accumula-
tion of windblown silt and soil
development. Post-depositional dis-
turbances such as bioturbation or
trampling can be interpreted from the
microstructure of the sediment and the
degree of mixing. These samples form
part of a continuous sequence of
micromorphology samples, which
incorporate the windblown silts and
prehistoric tephra layers down to
Hekla-3 and have therefore been
labeled as Reference samples.
Adjacent to micromorphology
sample Ref. 2/3, C4 was bulk sampled
for geochemical analysis (bulk sample
no. 13). Analysis will focus on the
lipid fraction in an attempt to charac-
terize the organic materials that
contributed to the formation of the
deposit, but which will have decom-
posed to such a degree that they are no
longer identifiable in thin section.
Organic residues that may potentially
be distinguished using lipid analysis
include human and animal excrement,
turf vegetation, fats and oils.
2) Western Wall and Doorway of the
Turf Structure in Area D: In 1996, a
continuous vertical sequence of
micromorphology samples was taken
from the turf wall exposed in the west
profile of Area D. The analysis of these
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