Identifying the reworking and stratigraphic provenance of bones by exploring multivariate geochemical relationships with the ‘Perio-spot’ technique

Publication date: December 2017Source:Journal of Archaeological Science, Volume 88
Author(s): Rhy McMillan, Dominique Weis, Marghaleray Amini, Dominique Bonjean
Erosional processes often rework materials of different ages into the same sedimentary facies, producing time-averaged deposits. Such reworking is common at archaeological sites, and researchers must consider the resulting time-averaging effects when using natural stratigraphy to situate artifacts and remains in time. At Scladina Cave, a Neandertal site in Belgium, we developed a method for identifying reworked facies and the stratigraphic provenance of mammal bones based on their post-mortem trace element characteristics and crystallinity. We collected sixty-two faunal remains from throughout the site’s sedimentary sequence and analyzed them for trace element concentrations and crystallinity with laser ablation inductively coupled plasma mass spectrometry and Raman spectroscopy. Our novel approach, the ‘Perio-spot’ technique, quantifies the trace element characteristics and crystallinity from the most diagenetically altered part of a bone with high spatial resolution. Trace element concentrations, rare earth element patterns, and crystallinity of ‘Perio-spots’ correlate throughout the Scladina sedimentary sequence. Based on stratigraphic trends in bone chemistry and crystallinity, we subdivide the Scladina sequence into two successive periods of early diagenesis, a period of later diagenesis, and a transitional period between the early and later diagenesis periods. The period boundaries also correspond to major climatic fluctuations identified in the site’s stratigraphy by other means (e.g., palynology and heavy mineralogy). The stratigraphic provenance of nine cave bear femora support the confinement of reworking to within each of the diagenetic periods; the provenance of two indeterminate faunal remains that visually resemble the taphonomic alteration of the Scladina Neandertal (taphonomic proxies) suggest that the individual may be significantly older than previously hypothesized. Evaluating the temporal integrity of exhumed assemblages and the original sedimentary context of bones with our method is thus a valuable addition to archaeological analyses, especially beyond the temporal range of radiocarbon dating or in contexts with very low preservation potential of organic materials.

Graphical abstract