ORGANIC-MATTER OF THE MULHOUSE BASIN, FRANCE - A SYNTHESIS

The lower Oligocene evaporite sequence of the Mulhouse Basin (France) contains organic matter-rich marl deposits. These marls display an ove rall cyclic variation of sedimentation rate, organic carbon content, h ydrogen index and selected molecular parameters over a 30 m thick stra tigraphic interval. The integration of all sedimentological and geoche mical parameters has allowed the reconstruction and characterization o f the paleoenvironment of deposition. The marls were deposited in a pe rennial lake that was at times connected to the sea. Two organic facie s end members could be assigned to a lake stage with a marine connecti on and a lake stage that received dominantly continental water input. The overall stratigraphic variation in the organic matter content is i nterpreted to reflect the adaptation of the Oligocene flora to the cha nging paleoclimate and environmental conditions.