CHARACTERIZATION OF ORGANIC-RICH MATERIAL IN AN EVAPORITIC ENVIRONMENT - THE LOWER OLIGOCENE OF THE MULHOUSE BASIN (ALSACE, FRANCE)

Evaporitic sediments from the Max borehole (Mulhouse Potash Basin, southern Rhine Graben) were studied over an interval of about 40 m in the vicinity of sylvite beds. Total organic carbon (TOC) analyses of 450 samples showed that marly layers interbedded within the evaporites have TOC values that fluctuate in a rhythmic manner; the highest values are found near the top of the clay-anhydrite layers and the lowest values are recorded near the top of the halite-rich beds. Geochemical (elemental analysis of kerogen, gas chromatography of bitumen) and palynological studies of 26 samples showed that the organic matter is mainly of algal origin (A and B groups). A third category of organic material (C group) may have been derived from a mixture of continental supply and in situ bacterial productivity.