Tricyclic terpenoid composition of Tasmanites kerogen as determined by pyrolysis GC-MS

The high abundance with which tricyclic terpenoids have previously been det ected in Tasmanite oil shales has led to the strong suspicion that the sour ce of these compounds is the Tasmanites microfossil prevalent in these oil shales. In this study, the hydrocarbon composition of a Tasmanite oil shale and isolated Tasmanites were separately investigated by laser micropyrolys is gas chromatography-mass spectrometry, a recently developed technique tha t facilitates the analysis of small samples such as microfossils. Major pro ducts comprised C-19-C-28 tricyclic terpanes, including the ubiquitous 13-m ethyl, 14-alkylpodocarpanes, as well as a number of additional tricyclic te rpane isomers, a C-19 monoaromatic hydrocarbon, and several C-19-C-28 tricy clic terpenes (one and two orders of unsaturation). There have been few pre vious reports on the tricyclic terpenes and their production is likely attr ibutable to the pyrolytic cleavage of analogous (probably saturated) tricyc lic precursors within the macromolecular biopolymer. The only major differe nce between the tricyclic terpenoid compositions observed from these sample s was the absence of the less concentrated oil shale products in the Tasman ites analyses, probably due to the lower organic content of the preextracte d fossil. The very similar tricyclic content of both samples strongly suppo rts the proposal of an inherent relationship between the Tasmanites and tri cyclic terpenoid production. The integrity of the laser data was confirmed by comparison to a conventional data set obtained by the pyroprobe pyrolysi s of the Tasmanite oil shale. Copyright (C) 2000 Elsevier Science Ltd.