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, sou thern 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 hav e TOC values that fluctuate in a rhythmic manner; the highest values a re found near the top of the clay-anhydrite layers and the lowest valu es are recorded near the top of the halite-rich beds. Geochemical (ele mental analysis of kerogen, gas chromatography of bitumen) and palynol ogical 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.