Nature of Tasmanian oil shale

Abstract

Since deposition, the organic matter of most oil shales has been so changed over geological time that little recognisable features remain. Microscopical examination does not provide much help for constitutional analysis and thus one cannot use biological features as a basis for classification. Tasmanite oil shale is a notable exception. The kerogen is so sharply differentiated from the mineral matrix that it can be largely separated by mechanical means. Tasmanite kerogen, when isolated, appears as flattened discs, which, by various sectioning processes, can be shown to have been nearly spherical in shape before compaction. There has been a great deal of argument as to the exact nature of these dissemenules. The century-old suggestion, originally rejected, that they are algal in origin has now been generally accepted and it may be taken that Tasmanites, as it occurs in oil shale, represents the cyst stage of a peculiar alga belonging, most likely, to the Chlorophyceae. The exact relationship within the family is still uncertain. Because of its discrete and peculiar structure, it might be assumed that the organic matter of tasmanite has a chemistry different from other algal shales. This is true only in so far as the soluble resin-like material is concerned, the pyrolysate possesses a normal hydrocarbon chemistry, although the non-hydrocarbon constituents are somewhat more than usual. Infrared and other physical methods of analysis support this hypothesis.