APPLIED MICROFACIES ANALYSIS - PROVENANCE STUDIES OF ROMAN MOSAIC STONES

Provenance analysis of archaeological materials is an essential tool o f archaeometry but has been rarely applied to antique mosaics. Many mo saics are made of carbonate mosaic stones (tesserae). Hence, microfaci es analysis offers a great potential in differentiating these limeston e tesserae and provenancing their local, regional, imported or recycle d origins. The methods of microfacies analysis and their prospects for studying mosaics are demonstrated by case studies of Roman mosaics fr om southern Germany (Kraiburg, Bavaria), Austria (Hemmaberg near Globa snitz, southern Carinthia), Italy (Asolo north of Padova) and late Pun ic and Roman mosaics from Tunisia (Carthage and Hergla). Microfacies-b ased provenance analysis comprises six stages: 1) Macroscopic assessme nt and definition of rock colour groups of tesserae, 2) Sampling based on rock-colour categories, 3) Definition of microfacies types and att ribution to standard microfacies types based on thin-section criteria, 4) Evaluation of the mosaic site with respect to geological and paleo ntological data followed by comparisons of the microfacies inventory o f the region with microfacies types of the tesserae, 5) Assessment of carbonate tesserae to specific geological rock/time units followed by suggestions of provenance sites, 6) Critical evaluation of provenance assessment within the archaeological context. Principal limestone colo urs do not necessarily coincide with specific limestone types. Uniform ly coloured tesserae can represent different limestone types from diff erent sources (cf. Kraiburg, Hemmaberg). On the other hand, a specific limestone type may be characterized by different rock colours (cf. Ca rthage).Provenance assessment of mosaic stones results in relatively n arrow (Hemmaberg, Asolo) or only broad (Carthage, Hergla) indications of sites characterized by exposures of carbonate rocks whose microfaci es criteria, geological age and rock colour correspond to those of the carbonate tesserae. The case studies argue for local and/or imported (Kraiburg) as well as regional provenances of the mosaic material (Hem maberg, Asolo; source area within a distance between 10 and about 40 k m) and indicate that off-cuts of building stones exploited within a re gional frame might possibly have been used (Carthage). Differences in the composition and diversity of carbonate locks used for the fabricat ion of mosaics reflect time-dependent changes in major quarrying and p otential source areas (Carthage). Further provenance research of mosai cs should be based on statistically representative tesserae samples, s upplemented by microfacies studies of the building material used at th e mosaic sires as well as investigation of non-lithic tesserae and the mortar bedding of the mosaics. The isotopic composition of limestone and dolomite tesserae also assists in the critical evaluation of micro facies categorization.