Inora Newsletter #46
FIRST RADIOCARBON DATING OF OXALATE CRUSTS
OVER SPANISH PREHISTORIC ROCK ART
Open-air rock paintings were discovered in the eastern Iberian Peninsula at the beginning of the 20th century. By the start of the 21st century, more than 800 such sites were included in the UNESCO World Heritage List (Rock art of the Mediterranean Basin in the Iberian Peninsula). Three main different styles have been described up to now. Levantine, Macroschematic and Schematic arts were identified as different expressions of hunter-gatherers and first farmer and herder groups, and so, as an important aspect of an evolutionary cultural change from the last predatory groups to productive economies. The chronology of these styles was derived from the images themselves, or from stylistic parallels with well dated artefacts, such as decorated ceramics.
Nowadays, clear parallels have been established for Macroschematic and Schematic arts, but serious doubts remain about the Levantine art itself. Levantine art is mainly painted in red and is characterized by naturalistic animal and human figures depicted in complex scenes such as hunting. After its discovery in 1903, it was considered as the Mediterranean counterpart of Cantabrian cave art, and so of Palaeolithic age. Soon after that, discoveries occurred in all the regions near Mediterranean Spain. The Palaeolithic theory was held up to the 1950’s. Then, a Palaeolithic age assignment was challenged because no glacial fauna was depicted, because the art was always found in open rock shelters instead of deep caves, and because painting techniques were different, as only plain colours and silhouettes without volume depiction were used in Levantine art. The frequent superimpositions of Levantine figures over schematic ones was taken to be the evidence of differences in their chronology. Thus, Levantine art was supposed to begin in the Mesolithic and develop up to the beginning of the Bronze Age. This position is still held by some researchers.
Fig. 3. Cueva del Tío Modesto main panel.
In the 1980’s a new style was discovered in the Alicante province by Mauro Hernández who called it Macroschematic. Some years before, Levantine art had several times been found painted over long linear and zigzag motifs, as was also the case at some sites with Macroschematic art. So it became obvious that Levantine art was not the oldest of the open-air rock art traditions in Mediterranean Spain. Researchers soon proposed stylistic parallels for the big humans with raised arms known in Macroschematic art with Neolithic Cardial ceramics. They considered that impressed motifs on ancient Neolithic Cardial ware depicted the same kind of “orants” painted in shelters, so they were considered to be of the same age as the impressed wares (5460-5230 cal BC) based on the Cova de l’Or (Alicante) archaeological sequence. Furthermore, abstract motifs of Schematic art also have parallels in the Cardial ware, so the Neolithic appears to be the departure point for those three styles.
(Fig. 3). The earliest painting episode consists of a series of 33 vertical zigzag lines. All other phases are superimposed over them. Painted over zigzags lines, the image that follows is that of a Levantine wild-goat hunting scene. The third phase, another Levantine hunting scene, is superimposed over the former. Both hunting scenes have parallels in the mid-Levantine sequence at other places, according to chronostylistic approaches. The 4th phase is on the left side of the panel, where three linear human figures cover zigzags and a Levantine archer from the 2nd or 3rd Levantine phase. The 5th phase is formed by several dotted lines and an anthropomorphic figure covering the 3rd phase on the right of the panel. The 6th and most recent episode is a group of orange vertical lines covering the 3rd and 5th painting episodes.
We have also examined the taphonomic processes at work in this shelter. The main panel is suffering flaking from its bottom towards the top. We have identified at least three levels in the present morphology of the panel. Most of the figures were painted on the primary level, which is fully covered with an oxalate crust, so that most paintings appear to be covered by this older accretion. Some flakes have broken from the bottom of the panel as in motif 123 (Fig. 3), and the newly exposed surfaces were then covered by a more recent deposit of oxalate. Finally, additional flakes are apparent in both levels, but oxalate has not yet formed on the surfaces left exposed by the more recent spalling.
To get chronological information, we sampled oxalate at three points, taking into consideration flaking and superimposition. TMD1 sample is related to the 2nd level of the panel and to the loss of motif 123. TMD2 sample is from the upper right of level 1; TMD3 from the upper left of level 1. The dates are: TMD2 6180 ± 35 BP (2 sigma: 5230-5010 cal BC) (Fig. 5); TMD3 5855 ± 35 BP (2 sigma: 4800-4610 cal BC); TMD1 2800 ± 35 BP (2 sigma: 1050-840 cal BC). They are roughly coherent, because the last two samples have a similar date, and the younger age for TMD1 represents the later flaking moment of level 1. That coherence from the two widely separated parts of the panel suggests an approximately uniform deposition when averaged over a few millennia.
Radiocarbon dating of these samples was accomplished by applying the technique of selective oxidation of organic carbon to remove any contaminant organic matter before sending the samples to the Center for Accelerator Mass Spectrometry of the Lawrence Livermore National Laboratory for radiocarbon analyses. Carbonate minerals have not been detected. TMD2 and TMD3 samples are clearly related to the oxalate layer that is covering the 1st-3rd pictorial phases, and probably also the 4th and 5th. We have observed in a thin layer section that paintings from the 1st and 3rd phases are embedded within the oxalate crust. Now, we are trying to get a deeper knowledge of the oxalate deposition process, so we can develop a more meaningful archaeological valuation of these dates. In this respect, it must be remembered that the older dates we obtained are not necessarily the absolute chronological limit of this panel. Rather, it is the dating of the weighted average of the oxalate crust accumulated along time in these two places.
This work was financed by the Consejería de Cultura de la Junta de Comunidades de Castilla La Mancha, Universidad de Castilla La Mancha (UCLM), European Regional Development Fund (ERDF) and the Universidad Nacional de Educación a Distancia (UNED).
Juan Francisco RUIZ, email@example.com
Martí MAS, firstname.lastname@example.org
Antonio HERNANZ, email@example.com
José María GAVIRA firstname.lastname@example.org
1-2 Departamento de Prehistoria y Arqueología and Departamento de Ciencias y Técnicas Fisicoquímicas (UNED, Madrid).
Marvin W. ROWE, email@example.com
Department of Chemistry (Texas A&M University)
Karen L. STEELMAN firstname.lastname@example.org
Department of Chemistry (Central Arkansas University)
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