Shape and size of lacustrine deposited melanogen (opaque organic matter), Upper Carboniferous, East Greenland

The content of opaque particles (melanogen) in eight kerogen concentrates from lacustrine sediments of the Upper Carboniferous of East Greenland are characterized with respect to shape and size by means of electronic image analysis. The method of electronic image analysis is briefly described and the applied sequence of image analysis functions is explained. The main items of the program sequence are shade and intensity correction, object discrimination and object selection. It is demonstrated that the method produces consistent results. Shape indices for circularity (4π × area/perimeter2) and elongation ((b/a)1/2) and the areas of the optical sections have been recorded. These parameters have a distinct relationship to the sedimentary environment; the melanogen particles in the clay-siltstone beds show increasing circularity, decreasing elongation and increasing areas up through the coarsening-upward sequences. Thus, the size and shape of the melanogen particles are not only tied to the sedimentary texture of the actual sample, but also to the overall textural characteristics of the section.