Geology Reference
In-Depth Information
Fig. 19.2.
Polychrome mosaic floor
of a late
antique church from the Hemmaberg near
Globasnitz, southern Carinthia. Most white
and pink mosaic stones are Triassic
dolomites. Black stones include Triassic and
Jurassic as well a few Carboniferous
limestones. No distinct correlation exists be-
tween rock color and specific microfacies
types. Most of the material was derived from
outcrops exposed within a distance of a few
kilometers adjacent to the mosaic site. In
addition some glacial boulders have been
used in the production of mosaic stones. The
average size of these stones is 1.5 cm.
were a center of early Christian pilgrimage (Fig. 19.2).
The churches were decorated by rich polychrome mo-
saic floors. Stylistic analyses of the mosaics prove that
the mosaicists knew the repertoire of mosaics in the
northern Adria region (Glaser 1996). Did the mosaicists
import material from the Adria region or did they use
local material?
Pink mosaic stones are fine to medium-crystalline
dolomite. White mosaic stones consist of dolomite and
limestone and exhibit 5 microfacies types. Light gray
tesserae are limestones exhibiting 4 microfacies types.
Most microfacies types observed in the Hemmaberg
mosaics can be attributed to Middle and Late Triassic
carbonates exposed along a distance of a few kilome-
ters. The idea that material was imported from the Adria
region can be rejected. A central on-site production of
the Hemmaberg tesserae is also supported by the enor-
mous amount of rock material necessary for the large
mosaics. The size of the mosaic area, the number of
mosaic stones necessary to cover this area, and the av-
erage size and volume, means about 4000 kg of mate-
rial must have been available for the tesserae.
Stable isotope data of Hemmaberg and Carthage
tesserae can be used in evaluating the differentiated
microfacies types. Close-spaced δ
18
O/δ
13
C patterns of
apparently different microfacies types indicate a too
rigorous definition and the necessity of uniting these
types.
19.4 Works of Art
Many antique sculptures were made of marbles, others
of limestones or other rock material. An examination
of the material may be necessary to clarify the produc-
tion area or recognize falsifications (Riederer 1994).
19.4.1 Works of Art: Methods
Limestone sculptures are studied by means of thin sec-
tions, marbles by geochemical methods and thin sec-
tions (Sect. 7.9; Pollini et al. 1998). Available thin-sec-
tion samples are usually very small, because archae-
ologists fear that the sculpture could be injured. How-
ever, even very small thin sections can provide a great
deal of information as demonstrated by the following
example.
19.4.2 Works of Art: Example
Fig. 19.3 shows a Roman sculpture from the middle of
the first century AD, tentatively interpreted as the head
of the Goddess Iuno. The head was said to have been
found in the Roman province of Raetia, near Augsburg
in southern Bavaria, but this assignment has been ques-
tioned in the light of stylistic arguments (Eingartner
