Sedimentation on the Madeira Abyssal Plain over the last 300 000 years

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Abstract
The sediments of the Madeira Abyssal Plain consist of thick turbidites (up to 5 m) separated by thin pelagic layers of clay, marl or ooze. Over most of the area the turbidites consist of ungraded massive silts and silty clays, sometimes with coarser bases. The mineralogy of these sediments suggests that they derive from the NW African margin. Isopach maps of individual turbidites show several of them thickening towards the W; their silty bases, however, coarsen towards the E suggesting transport from the NW African margin, followed by ponding on the plain. Some of the smaller turbidities are concentrated in particular areas of the plain. One group is concentrated in the N and NE, whereas a group of pure CaCO3 turbidites are limited to the SW, suggesting an origin from the nearby seamounts.