Characterization of pre-Columbian artefacts in situ through handheld portable X-ray fluorescence spectrometry: the case of ceramics from the Mochica site of San Jose de Moro (Peru)

The famous archaeological site of San Jose de Moro (SJM) located in the Jequetepeque Valley (JV) represents one of the best-preserved pre-Columbian Mochica cemeteries uncovered along the north coast of Peru. SJM was a regional ritual centre where elites and the general population of all JV met to celebrate ceremonial events. Its role as a place of regional integration and coordination continued long after the disappearance of the Mochica and SJM was continuously occupied throughout the Late Mochica Period (8th-9th c. AD) and into the Transitional Period (9th-10th c. AD). Even though the abandonment of Mochica traditions in SJM (funerary practices and ceramic styles) appears quite rapid, SJM was constantly occupied whereby local traditions were being reshaped. During this time various styles of ritual ceramics from different traditions (Mochica, Cajamarca and Wari) were buried within ceremonial and funerary contexts. This research involves archaeometric studies of excavated painted diagnostic ceramic sherds representing four distinctive pre-Columbian typologies present at this site-Mochica fineline bichrome, Mochica fineline polychrome, coastal Cajamarca and Highland Cajamarca ceramics. For this study handheld portable X-ray fluorescence spectrometer (HHpXRF) instrumentation was operated in situ in order to (1) perform non-destructive trace element analysis (2) to assess if Cajamarca ceramics were further elaborated using the same raw materials employed by the Mochica potters of SJM, and (3) to establish whether or not Mochica and Cajamarca ceramics were truly technological markers in the lower part of the Jequetepeque valley. Results: The chemical elements detected in the ceramic bodies by the portable technique and used for this analysis were: K, Ca, Mn, Fe, Zn, Ga, As, Rb, Sr and Y. All sherds that were identified as aesthetically different also differed chemically with the exception of the Mochica fineline bichrome and the Mochica fineline polychrome, which were produced in a coastal workshop using the same local raw materials. In addition, these sherds were not elaborated employing the same recipe used in the Coastal and Highland Cajamarca productions. Conclusions: Mochica ceramic productions are stylistically and chemically different from both Coastal and Highland Cajamarca productions. Ceramics from San Jose de Moro are technological markers of two cultures (Mochica and Cajamarca) in the lower part of the Jequetepeque Valley that interacted during Late Mochica and through the Transitional periods.