MACERAL-BASED ENVIRONMENT OF DEPOSITION MODELS: EXAMPLES FROM ANALYSIS OF A LITHOTYPE SUITE FROM A CRETACEOUS COAL, INNER MONGOLIA AUTONOMOUS REGION, CHINA

Of the three maceral groups in organic petrology, varieties of the vitrinite-group and certain inertinite-group macerals are of specific interest. Previous research has determined maceral and environment-of-deposition models for specific regional and age coal sources. However, general models that work well for a majority of coals have not yet proven to be universally successful. Using data from a Cretaceous Inner Mongolian low-rank coal lithotype sequence, a series of published models for interpreting depositional environments from macerals have been examined for general use on coal samples. The coal samples studied contained vitrinite ranges from 18% to 94% with a dominance of telovitrinite and often an absence of substantial gelovitrinite. Inertinite values range a greater difference from miniscule amounts to 70% per sample. In examining these models, index values such as the Groundwater Influence Index (GWI), the Tissue Preservation Index (TPI), and the Gelification Index (GI) were used to gauge prediction accuracy. These models will provide petrographers a base for estimation of such values for their samples from a large variety of regions.