Late Eocene diatomite from the Peruvian coastal desert, coastal upwelling in the eastern Pacific, and Pacific circulation before the terminal Eocene event
Previously undocumented late Eocene diatomaceous sediments are present near Fundo Desbarrancado (FD) in southern Peru. These sediments are similar to Miocene diatomite from the same area but, unlike the Miocene diatomite, the FD sediments contain cherty layers, are enriched in CaCO3, have a diverse and abundant radiolarian fauna, and possess varved-massive and millimetre- and metre-scale biogenic-terrigenous alternations. The FD sediments are part of an Eocene sequence that includes the clastic sediments of the Paracas Formation, and they are correlative to the Chira Formation of northern Peru. The Paleogene biogenic sediments of western South America show that coastal upwelling developed in the eastern Pacific before the latest Eocene, argue for the existence of a proto-Humboldt current at this time, and suggest that the terminal Eocene event was the culmination of gradual changes and not a catastrophic event at the Eocene/Oligocene boundary. © 1988 Geological Society of America.
Marty, R; Dunbar, R; Martin, JB; Baker, P
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