The characterisation of amber from deposit sites in western and northern Canada. (June 2016)

• Record Type: Journal Article
• Authors: Poulin, Jennifer; Helwig, Kate
• Is Part Of: Journal of archaeological science. Volume 7(2016)
• Page Start: 155
• Page End: 168
• Publication Date: 2016-06
• Subjects: Amber -- FTIR -- Py-GC–MS -- Resinite -- Thule -- Amber beads; Archaeology -- Periodicals; Archaeology -- Research -- Periodicals; 930.1
• DOI: 10.1016/j.jasrep.2016.03.037
• Languages: English
• ISSNs: 2352-409X

Abstract

Abstract: For years, the recovery of amber beads and other objects with amber components from archaeological sites in Canada has raised questions concerning the deposit site sources for this highly traded material. Objects found at one site may have originated elsewhere, thus, the accurate characterisation of amber could aid in establishing trade. In this investigation, 12 distinct amber specimens from 11 deposit sites in Canada were studied in order to determine their subclass and other distinguishing chemical features. The ambers were analysed using Fourier transform infrared spectrometry (FTIR) in combination with pyrolysis-gas chromatography–mass spectrometry (Py-GC–MS), using a thermal separation probe (TSP) to perform the pyrolysis and sample introduction. Analysis of the amber from the 11 deposits in Canada showed that they represent three different classes: Class Ib (based on regular -labdanes), Class Ic and Class Id (both based on enantio -labdanes). Different forms were found within the Class Ib and Ic ambers, based on the presence and absence of self-crosslinking and free succinic acid. The techniques identified polymeric crosslinking in three subclasses. These include self-crosslinking of communol and communic acid moieties in two Class Ib (form 2) ambers, self-crosslinking of ozol and ozic acid moieties in one Class Ic (form 2) amber and succinylation of the Class Id ambers. Other important characteristics were discovered, including the presence of free succinic acid in six Class Ib (form 1) ambers and one Class Ic (form 1) amber, the presence of diagenetic analogues of both dehydroabietic acid and callitrisic acid in all Class Ib (form 1) ambers, and the attachment of non-polymerisable terpenoids to the macromolecular structures of two Class Ib ambers and one Class Id amber. Amber beads recovered from three Thule sites in the Canadian arctic were characterised and compared to the 12 reference specimens. The beads from site TkAu-1 (Ellesmere Island) were found to originate from the local deposit at Lake Hazen. However, beads from the QeJu-1 (Cornwallis Island) and OkRn-1 (Banks Island) sites closely matched amber specimens from the major deposit at Cedar Lake (Manitoba). This may indicate movement of the Cedar Lake amber to the arctic via trade. Graphical abstract: Highlights: 12 specimens of amber from 11 deposits sites in Canada were characterised. Analysis was performed using TSP Py-GC–MS and FTIR. Three sub-classes of amber were determined: Class Ib, Class Ic and Class Id. Free succinic acid and self-crosslinking occur in some Class Ib and Ic ambers. Archaeological amber objects from three Thule sites were characterised.