A combination of FT-IR, FT-Raman and GC-MS techniques for the identification of pastes from an archaeological site at Beagle Channel, Tierra del Fuego, Argentina.

MAIER, M; FIORE, D; FARIA, D; PARERA, S

Nueva York, USA

Congreso; The Seventh Biennial Gathering of the Infrared and RAMAN Users Group. IRUG7.; 2007

Archaeological samples are very complex in composition, since their preparation generally involves a mixture of materials submitted to deterioration factors that are largely dependent on the environmental conditions. In the case of pastes, the presence of an inorganic and an organic phase, adds up to the system complexity. Therefore, the use of complementary analytical tools such as FT-IR, GC-MS and more recently non destructive FT-Raman spectroscopy can maximize the amount of information provided by a sample, allowing a better understanding of its degradation process. In continuation of our studies on archaeological pastes we have studied two samples of red painting residues that were in stratigraphic position in the archaeological site Shamakush I in Tierra del Fuego, Argentina. The two samples were found in strata dated by C14 in 940 B.P. and belong to hunter-gatherer-fisher societies that started their littoral adaptations in the Beagle Channel coast 6200 BP. Analysis by FT-IR of the pastes revealed the presence of strong bands at 543 and 470 cm characteristic of hematite together with bands at 2931 and 2859 cm due to C-H stretching vibrations in methyl and methylene groups and a carbonyl band at 1743 cm. These bands are characteristic of lipids. The FT-Raman spectrum of one of the pastes confirmed the presence of hematite and showed an intense band due to double bond stretching at 1602 cm characteristic of unsaturated lipids. Analysis by GC-MS of the mixtures of fatty acids obtained by transesterification of both pastes confirmed the presence of saturated (C15, C16, C17, C18) and unsaturated (C16, C17, C18) fatty acids together with a mixture of hydrocarbons.