Bone collagen diagenesis at Roonka Flat, South Australia: implications for isotopic analysis

Abstract

AbstractA simple screening procedure to select archaeological bone samples for radiocarbon dating or stable isotope analysis is assessed at the Roonka Flat Dune, South Australia. Carbon and nitrogen concentrations in HCl insoluble bone extracts are employed to address variations in collagen preservation. Sandy sediments like those at Roonka provide one of the poorest environments for archaeological bone preservation. However, many prehistoric human interments and midden deposits occur in sandy contexts. Archaeological bone specimens from 86 human skeletons dating from ca.10ka BP to AD 1840 are assigned to Good, Intermediate, and Poor collagen preservation categories according to variations in extract carbon and nitrogen concentrations. Good collagen preservation was restricted to the Late Holocene skeletons and included 47% (32/68) of the sample. Over 83% (15/18) of the Early Holocene sample and 34% (23/68) of the Late Holocene sample were placed in the Poor collagen preservation category on the basis of low carbon and nitrogen concentrations. As the archaeological bone at Roonka becomes more poorly preserved, atomic C/N ratios increase and are more variable, and stable carbon isotope values become more positive and also show greater variability. Collagen yields from whole bone are extremely variable and do not relate to variations in collagen preservation. There is also extreme variability in collagen preservation in bone from closely associated burials. With regard to skeletal maturity, suabadults generally have better collagen preservation than adults.