Here, we investigate the application of rock surface IRSL dating to chronology restrain archaeological structures related to upland pastoralism. We applied the method to cobbles collected from archaeological units in an excavation of a dry-stone structure in Val di Sole in the Italian Alps. At this site, archaeological finds and previous radiocarbon analyses have dated an initial human occupation of the site to the Early Bronze Age (ca. 2200–1600 BC), and a possible second occupation to the Middle Bronze Age (ca. 1600–1350 BC). These archaeological units have later been buried by colluvial sediments. Theoretically, the luminescence-depth profiles from rock surfaces from inside such structures could record the exposure and burial of these archaeological units. We collected buried gneiss cobbles from these archaeological units and measured rock slices and chips from 1 to 4 cm long cores with a low-temperature pIR-IRSL protocol to investigate the signal resetting in these cobbles. Only the IRSL50 signal was deemed appropriate for dating. Measured luminescence-depth profiles demonstrate varying levels of signal resetting before burial. Dating of two paragneiss cobbles from the lower unit yielded corrected burial ages of ∽1450-700 BC and ∽19 ka. The older date is clearly not associated with human occupation; the younger date slightly underestimates the Early Bronze Age occupation, which was confirmed by new radiocarbon dating of charcoal (1731-1452 and 2124-1773 cal. BC). The burial of the upper archaeological unit was dated to ∽AD 1000, based on ages derived from the bottom surface of an orthogneiss cobble and the top surface of a paragneiss cobble. This is slightly younger than two new radiocarbon ages (426-596 and 537-654 cal. AD) from charcoal fragments sampled from the same unit. This new chronological data show longer exposure of the upper archaeological unit than was previously known. Furthermore, the paragneiss cobble from the upper unit has been exposed to sufficient heat to reset the IRSL50 and pIR-IRSL290 signals throughout the cobble; an event which can be dated to ∽AD 100–1500 BC. Comparisons between fading-corrected IRSL50 ages and pIR-IRSL290 ages from the heated cobble are in agreement, which suggests that the conventional g-value approach accurately corrects for signal loss during burial. Overall, our research suggests that rock surface IRSL dating can provide complementary chronological data for archaeological settings.
Bibliographical noteFunding Information:
Dr. Anja Zander, University of Cologne, is thanked for gamma spectrometry measurements. Laura Vezzoni, University of Trento, is thanked for visual inspections of petrographic thin sections. The authors are grateful to Dr. Fabio Cavulli, University of Trento, for helping during fieldwork and for providing photo-plans of the excavations. Lucas Ageby is funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) ? Project number 57444011 - SFB 806 as part of project F2 in CRC 806 ? Our Way To Europe. Francesco Carrer's research is funded by the Newcastle University Academic Track programme (NUAcT), UK. Project ALPES is undertaken in the context of a specific agreement between the Department of Humanities of the University of Trento and the Soprintendenza per i Beni Culturali of the autonomous Province of Trento. The project is funded by the University of Trento, Italy and by the Terre Alte programme of the CAI (Italian Alpine Club) and is supported by the Municipality of Mezzana, Italy (Trento). The authors are indebted to the people from Ortis? and Menas for their help, and to all the students and researchers who have participated in fieldwork activities. The work by Eike F. Rades was funded by the German Research Foundation (DFG) in the framework of a Research Fellowship (RA 2836/1-1). Finally, we thank Dr. Michael Meyer and two anonymous reviewers for their helpful feedback and comments, which greatly improved the manuscript.
- Dry-stone structures
- Luminescence-depth profiles
- Rock surface luminescence dating
- Val di Sole