Szeletian felsitic porphyry: non-destructive analysis of a classical palaeolithic raw material (original) (raw)

2003, Acta Archaeologica Academiae Scientiarum Hungaricae

Szeletian felsitic porphyry is one of the most famous raw materials used in the Hungarian Palae olithic. 1 It was identified, under various names, by students of the Palaeolithic material of the Bükk region in the earliest petroarchaeological descriptions. Due to its high silica content and homogeneity it was erroneously identified as hornstone, 2 later as ash-grey chalcedony, 3 even in petrographical descriptions based on thin sections. 4 Interestingly, the geological source was placed on the plateau of the Avas, where solid 'flint' and 'chert' were reported. 5 With the advance of new analytical methods and their application to archaeology, Lajos Tóth, at that time general engineer of the Diósgyôr Steel Works, and László Vértes, cur a tor of the Hungarian National Museum, performed a classical study to fingerprint this material. Following the geological descriptions of Gábor Pantó, 6 they sampled sources of " quartzporphyry, " high silica content epi-metamorphic volcanic rock outcrops from Károly Kaán spring in the vicinity of Miskolc. They compared these samples to archaeological material from nineteen sites of various ages and industries with the help of X-ray diffraction analysis (XRD) (Fig. 1). Because, in addition to silica, " quartz porphyry " is composed of feldspars, mica, and kaolinite, all of them with typical XRD signals, 7 they were able to separate their raw material samples from silex (mainly postvolcanic silices, chalcedony, and hor nstone). They published their results in a classic study in Acta Archaeologica Hungarica: Der Gebrauch des glasigen Quartzporphyrs im Paläolithikum des Bükk-Gebirges. 8 This study can be considered the first Hunga rian effort to apply high-tech analytical methods to the study of lithic materials and is an early application of an archaeometrical approach in archaeology altogether. The drawback of the method is partly its destructive character (at least, on a routine way), 9 partly rooted in the applicability of the method. XRD is typically used in combination with other methods, mainly chemical analysis of the main components and thermal analyses for more precise identification of the mi neral phases. In the mid-1970s, during a general study of Hungarian lithic raw materials by V. T. Dobosi and L. Ravasz-Baranyai, some " quartz porphyry " finds were also examined. After thin sectioning, this kind of rock was identified as felsitic banded rhyolite (felzites-sávos riolit), 10 which raised the problem of differentiating between palaeovolcanic rocks from the Ladinian stage and the remains of Neogene volcanism. 11 However, unless they were heavily silicified, young rhyolites were seemingly not used for the production of Palae olithic chipped stone implements. In course of the raw material historical research program led by J. Fülöp at the Hungarian Ge ological Survey, 12 a systematic study of the most important Hungarian chipped stone raw materials was pe rformed, including-among others-Szeletian felsitic porphyry. Petrographic thin sections, chemical anal y-1