Mapping diagenesis in archaeological human bones

Abstract

We describe a procedure for ascertaining the extent of diagenesis in archaeological human skeletons through the distribution of Sr, Ba, Cu, Pb, Fe, and Mn in cross-sections of femoral cortical bone. Element mapping is performed through Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS). Absolute calibrations of element concentrations were obtained using Inductively Coupled Plasma Mass Spectrometry (ICP-MS) on adjacent dissolved bulk bone samples. By comparing a modern individual to five medieval to early modern Danish skeletons, we demonstrate the degree to which concentrations of trace elements are attributable to diagenesis. Invasion from the exterior bone surface into a degraded part of the outer cortical bone is the most frequently occurring diagenetic change. In the archaeological skeletons investigated, diagenetic modification is restricted to, at most, the outer ca. 0.5 mm of bone. In one femur, Haversian channels were filled with diagenetic material, which appears to have entered the bone through a network of cavities largely made up by Haversian and Volkmann's canals.

Copper exposure in medieval and post-medieval Denmark and northern Germany: its relationship to residence location and social position

“…The distribution of the Dominican Friary sample, which contained many churchmen, is different from those consisting of skeletons from other contexts Fig. 8 Concentrations of Sr and Ba in femoral cortical bone (µg g −1 ) from early to late Ribe Cathedral graveyard skeletons: AD 800-1050 (a), AD 1225-1425 (b), AD 1425-1738 (c), and AD 1738-1805 (d) somewhat higher than those reported for presentday populations [24,61,64] (Fig. 2), but they were not above the upper bounds of ranges for modern non-buried bones, except for Ribe.…”

“…Only cortical bone deeper than 1 mm was used for chemical analyses. Examinations of cortical bone cross-sections have shown that 1 mm is at least twice the depth of physically and chemically degraded bone normally seen in Danish medieval skeletons [24].…”

“…Before inferences are drawn about past conditions from archaeological bones, it must be established that the element(s) of interest is indicative of what took place during the lives of the sampled individuals rather than what happened after they had died and were buried. The elements Fe, Mn, Al, and As have consistently been reported as being strongly affected by diagenesis [24,[123][124][125].…”

“…Although diagenetic Cu contamination has been a concern for most, but not all, studies of archaeological materials [17-23, 39, 99, 100], a recent study of centuries old Danish skeletons has shown that alterations in Cu content occur within the outer 500 µm of compact bone [24]. This work shows that suitable precautions taken when sampling thick cortical bone, starting with a mechanical removal of the outermost surface to a depth of at least 1 mm, are sufficient to obtain satisfactory samples from Danish medieval or later skeletons.…”

“…In short, Cu in excavated bones might originate from the food and drink consumed, environmental exposure, or alterations in composition long after a skeleton was buried. Because the last confounds interpretations of archaeological skeletons, it is fortunate that Cu concentrations in bones from medieval to early modern Danish cemeteries are largely free of diagenetic effects as long as suitable precautions are taken when sampling thick cortical bone [24].…”