Figure 5b. ODP Leg 161 drill sites and Pleistocene occurrences of sapropels and ORL's in the western Mediterranean. Preliminary time scale is based on shipboard biostratigraphic data. In the Tyrrhenian and Balearic seas, sapropels are discrete layers up to 30 cm thick. In the Alboran Sea, ORL's contain 0.8% to 2.5% organic carbon and are up to 3 m thick. These layers are more dispersed and thus do not resemble type sapropels. Yet, ODP Leg 161 drilling results suggest that organic-rich sedimentation occurred basinwide in the western Mediterranean.