This study aimed to: 1) characterise the individual San parietal art rock art paint colours; 2) relate
paint compositions to erosion susceptibility; 3) determine if paint pigments can be related to pigment
samples excavated from a Shelter deposit, and/or a variety of field samples; and 4) determine if paint
samples from geographically distinct sites can be distinguished on their composition. A combination
of mineralogical (X-ray diffraction (XRD), synchrotron micro-XRD (μ-XRD)) and chemical (energy
dispersive X-ray micro-analysis (EDX), X-ray fluorescence spectrometry (XRF), and synchrotron
micro-XRF (μ-XRF)) analytical techniques were used.
Maqonqo Shelter (MQ), 35 km south-east of Dundee, KwaZulu-Natal, South Africa, was the
primary study site chosen as it contained both a large number of paintings, as well as a large deposit.
Thirty paint (of various colours) and 3 blank wall samples were collected using Silver Mylar tape and
analysed using a combination of EDX, μ-XRD and μ-XRF techniques. Sixty two large (> 2.5 g)
‘ochre’ pieces were selected from the upper three layers of the deposit and analysed using XRD, XRF
and EDX. A further 63 small pieces (< 2.5 g) were analysed using μ-XRD and μ-XRF techniques.
To compare the MQ paint samples with potential source materials, three distinct sample sets were
collected. The first included samples of the Shelter wall and surface rocks located near the painted
panel (analysed by XRD, XRF and EDX). A second sample set of 17 samples was collected from the
surrounding landscape (± 3 km radius of MQ; analysed by XRD and XRF). Their selection was based
on ease of accessibility, degree of pulverulence, and perceived Fe content i.e., red and/or yellow
colouration. No white sources were found. A third set of 11 samples (obtained from six sites, analysed
using XRD and XRF) was collected within ± 50 km distance of the Shelter. Their selection was based
on old mining survey reports that detailed the location of Fe ore outcrops.
Paint samples from three additional shelters i.e., Fergies Cave (FC), Giants Castle Game Reserve,
central Drakensberg; Sheltered Vale (SV), Mount Currie District, south-western KwaZulu-Natal; and
Twagwa Shelter (TW), Izingolweni District, southern KwaZulu-Natal, were collected to compare
paint composition over distance. Site selection was determined according to the following criteria: 1)
the shelters had to reside a significant distance away from the primary site so as to minimise any
possible interaction that might have existed between the authors of the respective artworks (each site
is at least 100 km distant from the other); 2) each had to be located upon a distinct geological
formation so that external influences from different regions, and their possible affects on the paint
samples, could be noted; and 3) the climatic regimes of each of the shelters should be relatively
distinct. Fifteen paint and nine blank wall samples were collected from the three shelters (three each
of red, white and blank samples; analysed using EDX, μ-XRD and μ-XRF), with the exception that no
white samples were collected from FC.
In total, 673 EDX, 212 μ-XRD, 378 μ-XRF, 98 XRD, 98 XRF and 6 ICP-MS traces were
produced and analysed. Due to the extremely heterogeneous nature of the paint samples at the microii
scale, the more generalised EDX reduced window scans were used as the basis of the paint samples’
characterisation, with the data obtained from the more precise μ-XRD and μ-XRF techniques
providing additional supportive information. Irrespective of colour, almost all of the MQ paint
samples had elevated Ca contents that tended to increase in the order of black < orange £ red and
yellow < pink < white. The predominant Ca-based mineral was gypsum, although Ca-oxalates,
whewellite and weddellite, were also present. The blank samples collected from MQ also had high
gypsum content, but no Ca-oxalate. It is thus proposed that the Ca-oxalates formed after the painting
event and were derived from the original paint constituents.
The white pigments consisted of gypsum (dominant), anhydrite, bassanite and whewellite, or a
combination thereof. Whewellite increased within increasing paint depth, while gypsum showed the
reverse trend. This indicates that, whilst both gypsum and whewellite were originally present within
the original paint pigment, additional gypsum has been added via secondary evaporite deposition.
Although initially considered to be sourced along with the gypsum, another potential whewellite
source is organic additives. The most likely source for the white pigments would be precipitates found
on sandstone walls of shelters near MQ. Of more immediate importance, however, is that the
pigments, being gypsum based, are water-soluble and thus susceptible to erosion.
Most of the orange paints had an elevated Al content and contained gibbsite, suggesting bauxitic
material associated with locally sourced dolerite within the Ecca Series within KwaZulu-Natal (as
evidenced by their respective Ti levels). Two samples were so similar that it is likely that the same
pigment was utilised in the creation of both images. Two samples did not contain high Al contents,
however, indicating that they were probably sourced from the soft, ochreous material found within
local Fe nodules.
A consistent combination of goethite and haematite, together with a low Al and elevated Ti
content, indicate that the yellow and red samples were probably sourced from Fe nodules found
locally, the red samples differing from the yellow pigments primarily in their higher haematite
content. A low Si and relatively low Fe content discounts red sands/clays and Fe-ores as sources of
the red pigments. The red samples were ‘thinner’ than the other samples with quartz contents
comparable to those of the blank samples. The thin nature of the red paints, the erratic distribution of
whewellite upon the paint surfaces, the dominance of gypsum and, to a certain extent quartz, all
strongly suggest that the red paints are at least partly absorbed into the surface of the Shelter wall.
This, together with the strong staining ability of haematite, is probably the most important reason that
the red pigments have outlasted images painted in other colours. It may also account for the high
degree of variability found within the red paint dataset, though age differences between the sampled
images could also be a contributing factor.
The single dark red paint sample, except for an elevated Mn content, was very similar in many
ways to the red paint samples analysed. The only readily available pigment source identified that had
both low Al and high Fe and Mn contents, was plinthite. The pink samples represented the ‘middleiii
ground’ between the red and white paints, suggesting that this colour was the result of a blending of
the two. The black paint sample had the highest recorded Fe content of the entire paint dataset. A high
Mn and relatively low Al content suggest that a soft inner core of an Fe nodule was used in its
manufacture. The presence of maghemite and a dark colouration strongly suggest that the
manufacture also involved calcination.
The initial distinction between the paint and excavated samples was that the former all exhibited
elevated Ca and S values due to the deposition of secondary evaporite minerals. Even when taking
these additional deposits into account, however, the two datasets still remained distinct indicating that
the excavated materials sampled were not utilised in the manufacture of the MQ paints. A potential
exception concerned the orange paint samples, which were similar in composition to both doleritic
samples from deeper excavated layers and the local (weathered doleritic samples) and distant (bauxite
samples) field samples. Whilst weathered dolerite/bauxitic material was clearly the source of the
orange pigments, a more detailed investigation is needed to find a precise location. No other
relationships between the paint pigments and the excavated pigments and field samples were
established.
A comparison of the blank samples from all four study sites showed that the techniques used
could distinguish between different sites despite sampling the smallest and, relatively speaking,
poorest quality samples. The FC blank samples had elevated C and Ca contents (associated with Caoxalates).
The conditions within this Shelter favour the formation of weddellite and whewellite, the
former not typically found at the other three sites. In addition, low K, Si and Al contents (often
associated with sandstone matrix minerals) indicate that the surface of the relatively dense, compact
Cave sandstone is more resistant to physical erosion compared to the other sites, and/or FC shelter
experiences a high amount of secondary deposition, with the result that a majority of the samples are
composed of evaporite minerals. The SV samples were composed primarily of the evaporite-type
minerals, with only minor sandstone ‘contamination’ indicated by quartz and kaolinite. The quartz
content, whilst not always high, was present in most of the samples analysed, possibly indicating a
greater amount of more uniform surface erosion (relative to the other sites). The TW blank samples
were distinct from the other shelters’ as they contained no Ca-based minerals but did contain the very
rare mineral schlossmacherite.
A comparison of the paint colours also revealed differences between the different shelters. Whilst
the white samples from SV and MQ are dominated by whewellite and gypsum (minerals probably
present within the pigments when they were applied), the presence of quartz, sanidine and apatite in
the SV samples indicated a degree of shelter wall ‘contamination’, with anhydrite, bassanite and
glushinskite suggesting climatic variations that favoured various evaporite depositional regimes. The
TW white paint contained minimal secondary deposited minerals common in the other shelters. The
one mineral that is dominant within the TW samples is minamiite. As this mineral was not identified
in any of the blank samples, it is likely that this mineral originates from the original pigment source.
The TW white paints also contained 10 to 40 times more Zn than those recorded for any of the other
paint samples. This was possibly present within the structure of greigite.
The red SV samples could be distinguished from MQ red samples by the presence of wall
‘contaminants’ in a manner similar to that described for the white samples. The TW samples indicate a change in pigment source and/or manner of paint manufacturing technique, for these red samples
contained minamiite. This mineral is white and thus its selection could not have been based on colour
but rather it must represent a paint additive. With the exception of only one sample from TW, no
goethite was found within any of the red samples collected from the three additional sites indicating a
different haematite source to that of MQ.
An interesting facet of this study, although not directly addressed, concerns what the results do
not show with respect to the compositional nature of the pigments analysed. Most texts available
today list a number of pigment sources stated to have been utilised in the manufacture of the San
parietal rock art. This study has shown that very few of these potential sources were utilised within
the four shelters investigated. In addition, this study has also highlighted the presence of minerals
about which little is known, yet which appear to be commonly associated with parietal rock art. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2011.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:ukzn/oai:http://researchspace.ukzn.ac.za:10413/7920 |
| Date | January 2011 |
| Creators | Escott, Boyd John. |
| Contributors | Hughes, Jeffrey C. |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | English |
| Type | Thesis |
Page generated in 0.0074 seconds