Nature of Tasmanian oil shale

Abstract

Since deposition, the organic matter of most oilshales has been so changed over geological timethat little recognisable features remain. Microscopicalexamination does not provide much helpfor constitutional analysis and thus one cannot usebiological features as a basis for classification.Tasmanite oil shale is a notable exception. Thekerogen is so sharply differentiated from themineral matrix that it can be largely separatedby mechanical means.Tasmanite kerogen, when isolated, appears asflattened discs, which, by various sectioning processes,can be shown to have been nearly sphericalin shape before compaction. There has been agreat deal of argument as to the exact nature ofthese dissemenules. The century-old suggestion,originally rejected, that they are algal in originhas now been generally accepted and it may betaken that Tasmanites, as it occurs in oil shale,represents the cyst stage of a peculiar alga belonging,most likely, to the Chlorophyceae. The exactrelationship within the family is still uncertain.Because of its discrete and peculiar structure, itmight be assumed that the organic matter of tasmanitehas a chemistry different from other algalshales. This is true only in so far as the solubleresin-like material is concerned, the pyrolysatepossesses a normal hydrocarbon chemistry, althoughthe non-hydrocarbon constituents are somewhatmore than usual. Infrared and other physicalmethods of analysis support this hypothesis.