First screening of collagen quality in Lebanese archaeological bones

Abstract

Radiocarbon dating is a crucial tool for studying national cultural heritage and reconstructing ancient human history. Uncalcined bones, alongside seeds and charcoal, are one of the most reliable materials to be dated, and more precisely the collagen which constitutes around 30% by weight of the whole bone. However, this collagen may not be well preserved due to the effect of physical and chemical properties of the burial environment. Radiocarbon dating of low-collagen bones could be costly, time consuming and cause destruction of valuable archaeological samples without getting reliable ages. Many techniques were developed to test the state of collagen in bone samples. In this work, an Elemental Analyzer was used on twenty-one bone samples to determine %N, C/N ratio and to calculate %C excess as indicator parameters of collagen preservation. All samples were collected from four coastal Lebanese archeological sites. Percentage nitrogen in 15 samples was below the threshold value 0.7% and hence they were not adequate for radiocarbon dating. The ratio C/N in the majority of the samples was higher than 5 indicating extensive diagenetic alteration or contamination by exogenous carbon. The percentages excess carbon were lower than maximum acceptable values 5-10%. Our results emphasize on the importance of collagen prescreening when dating local bone samples which are in many cases degraded.