The application of quantitative spore colour measurement to thermal maturity studies

Milton, James Andrew (1993) The application of quantitative spore colour measurement to thermal maturity studies. University of Southampton, Doctoral Thesis.

Abstract

For appraisal purposes the quantitative colour technique has been used to examine thermally induced transformations in spores and pollen in a wide range of material; artifically matured modern spores, fossil palynomorphs from the aureoles of minor igneous intrusions, and on- and off-shore well material. The resulting database has been used to comprehensively assess the colour property of spores as a maturity marker. A synopsis of results is as follows:

1) With increasing thermal maturity the colour changes in spores and pollen define a consistent and reproducible trend in the CIELAB colour space. Using various numerical measures the position of any given spore along this trend can be determined and directly related to thermal maturity. Progression along the colour-change trend is one-way. The spread of colour data is also related to maturity. Significantly, all sample suites (experimental and natural) exhibit the same colorimetric behaviour.

2) The recordable and quantitative nature of the measurement has identified consistently occurring patterns of colour change that have been fully characterised. At specific points in the maturity trend, distinctive colorimetric events occur. These are related to significant chemical transformations in the spores and can be used as markers for them. The most fundamental colorimetric changes (apparent in all measured colour parameters) coincide with the initial on-set of hydrocarbon generation. One the basis of the colorimetric measures thermal maturity can be accurately determined. These findings have been confirmed by correlation with other maturity markers (e.g. vitrinite reflectance, Tmax, etc.).

3) A systematic variation in the colour of palynomorphs has been identified. At any given maturity morphologically similar types will have similar colour properties. The dominant controlling factor is wall thickness.

4) For well-based exploration purposes the rapid measurement of 40-50 randomly selected (avoiding likely re-worked/caved material) spores and pollen per sample is sufficient for a usable maturity evaluation.

Existing spore colour standards (e.g. the SCI) have been measured and appraised by quantitative measurement.

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