Paleoceanographic evolution of backwater in the Nazca region, southeastern Pacific, during late Pleistocene

  • Adolfo Molina-Cruz Instituto de Ciencias del Mar y Limnología, UNAM. Cd. Universitaria, Circuito exterior s/n, 04510 México, D.F., México.
  • Juan Carlos Herguera CICESE. Carretera Tijuana-Ensenada, Km. 107, 22800 Ensenada, Baja California, México.
Keywords: Chile Current, southeastern Pacific, trade wind field, radiolaria, glacial-interglacial episodes.


The distribution of radiolarian assemblages in the surface sediments of the southeastern Pacific reflects the westward advection of the Chile Current away from the coast and its mixing with Subtropical Water. This oceanic process, occurring along the eastern section of the Nazca Ridge (~ 20° S), is influence by the trade wind field, disrupts the Subtropical Convergence and leaves backwater near the coast. Late Pleistocene glacial-interglacial fluctuations of this ocean circulation are reconstructed using radiolarian assemblages in core H96-Tg7 (17°14.04’S, 78°06.16’W). Glacial episodes exhibit more intense ocean circulation than interglacial episodes. Extreme southern incu rsions of Subtropical Water occurred during Marine Isotope Stages 11, 5 and 1, suggesting that extremely warm climate conditions occurred episodically.