The deposits are rich in organic carbon and occur in cycles of sedimentation that range from 10420 000-100 000 years but average 09640 000-50 000 years. The organic carbon-rich lithologies are commonly enriched in Cr, Ni, V, Cu, Zn and Mo. The slowly deposited oxidized shales are enriched in Fe, Mn, Zn and Cu.-K.A.R.
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Origin and geochemistry of Cretaceous deep-sea black shales and multi-colored claystones, with emphasis on Deep Sea Drilling Project site 530, Southern Angola Basin.