QUANTITATIVE SPORE COLOR MEASUREMENT USING COLOR IMAGE-ANALYSIS

The colour changes that sports exhibit, with increasing depth of buria l, are used as a thermal maturity indicator for evaluating hydrocarbon source rocks. Spore colour is determined visually leading to an intri nsic difficulty of unequivocally assessing and recording their colour. Quantitative scales using photometers are available, but are not wide ly applied. Colour Image Analysis (CIA) is presented here as an altern ative method for the quantification of Sport colour, through the use o f Image Analysis software common in many laboratories. Using the RGB ( red, green, blue) colour format, the colour of spores was determined. The material included a set of artificially heated Lycopodium spores a nd geological samples from a range of ages and geographical areas cove ring the entire maturity range. These data were then compared to sampl es from a well section of Carboniferous age which were 'fully mature' to 'post mature'. With increasing maturity the colour changes in spore s and pollen define a consistent and reproducible trend on the red vs. green (pixel intensity) graph. Significantly all samples suites (expe rimental and natural) exhibit the same behaviour. Previous research [M illon, J. A. (1993) Ph.D. thesis; Gutjahr, C. C. M. (1966) Leidse Geol ogische Medelingen, 38, 1-30] show a strong morphological control on c olour, based on differences in wail thickness and original chemistry. However, if sports and pollen are chosen carefully i.e. avoiding taxon with cracks, folds, apertures and ornamentation, as well as those wit h exceptionally thin (bag-type) or thick exines, a good sample average can be made by measurement of 40-50 similar spore/pollen types. Speci fic points on the red vs. green colour graph coincide with significant chemical transformations and these coincide with the thermal cracking of the spore wail (spore oil window). (C) 1998 Elsevier Science Ltd. All rights reserved.