Sedimentary Facies on the Rises and Slopes of Passive Continental Margins [and Discussion]

Joides drilling results provide new evidence concerning facies patterns on evolving passive margins that strengthens and extends hypotheses constructed from studies of morphology, seismic reflexion data and shallow samples on modern margins, and from field geologic studies of uplifted ancient margins. On the slopes and rise, gravitycontrolled mechanisms -- turbidity currents, debris flows, slides and the like -- play the dominant role in sediment transport over the long term, but when clastic supplies are reduced, as for example during rapid transgressions, then oceanic sedimentation and the effects of thermohaline circulation become important. Sedimentary facies models used as the basis of unravelling tectonic complexities of some deformed margins, for example in the Mesozoic Tethys, may be too simplistic in the light of available data from modern continental margins.