At the end of the Leg 73 cruise, at Site 520, a thick upper Miocene facies of laminated diatomite was discovered. It was hypothesized that the sediment was derived from nutrient-rich waters in a young Cenozoic anoxic basin in the open Atlantic Ocean near the Mid-Atlantic Ridge.

Supplement to: Herbin, Jean-Paul; Deroo, Gerard (1984): Organic geochemistry of Miocene-Pliocene laminated diatomites on the East Flank of the Mid-Atlantic Ridge (Site 520, Leg 73). In: Hsü, KJ; LaBrecque, JL; et al. (eds.), Initial Reports of the Deep Sea Drilling Project (U.S. Govt. Printing Office), 73, 537-538