F.L. Staplin, 1987. "Determination of Thermal Alteration Index from color of exinite (pollen, spores).", How to Assess Maturation and Paleotemperatures, F. L. Staplin, W. G. Dow, C. W. D. Milner, D.I. O’Connor, S.A.J. Pocock, P. van Gijzel, D.H. Welte, M.A. Yükler
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The change in color of organic particulate debris with increasing thermal increments is an easily observable feature that requires only routine palynological preparations for its use. With proper standardization of techniques, arbitrary numerical values may be applied to the color change sequence, and related with other, more sophisticated means of determining the level of maturation (Figure 1).
Most of the difficulty encountered with this method stems from failure to standardize the techniques.
Standardized processing of samples to obtain the residue.
Only HCl and HF treatment should be used to obtain the organic matter slides. Oxidizing agents will change the color of the materials substantially. Centrifugation and/or decantation should be monitered carefully, otherwise light and fine fractions may be lost.
If necessary, water-soluble ZnBr2 may be used to concentrate the organic fraction.
Mounting media for the residues should be clear and non-reactive, close to 1.54 refractive index.
Standardized light source.
Illumination at 3200° K with a light blue “daylight” filter yields a good white light with simple set-ups. Follow the directions provided with the microscope and light source if halogen or xenon lamps are used.
Polarization filters affect the image contrast and inhibit color discrimination. If the color temperature is too low, the light is yellow-red and the result will be a bias toward a higher thermal index than exists.
Standardization on the object measured.
Different kinds of organic matter have different responses to thermal increments. The color changes converge at the high end of the scale.
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How to Assess Maturation and Paleotemperatures
The application of organic matter studies in petroleum exploration had its start with the recognition of “rank” in coal. During the period of 1900–1925, both physical and chemical methods were developed for determination of the degree of low grade metamorphism of particulate organic materials, or palynodebris in coals and other sediments. Measurements of the relative metamorphism (maturation level) which are based on physical properties are generally quick, cheap, and qualitative to semiquantitative. Those based on chemical analyses are less rapid and tend to be more quantitative. Each method has advantages and disadvantages and they often are combined. Papers included in this course consider methods based on particulate organic matter, reflectance, fluorescence, and geochemistry. A method for integrating the data into a three-dimensional model is included.