Late quaternary oceanic circulation along the Pacific Coast of South America

• Main Author: Molina-Cruz, Adolfo
• Other Authors: Thiede, Jorn, Quinn, W., Simons, W., Boucot, Art, School of Oceanography, Oregon State University. Graduate School
• Format: Doctoral or Postdoctoral Thesis
• Language: English; unknown
• Published: Oregon State University
• Subjects: Upwelling (Oceanography); Antarc*; Antarctic
• Online Access: https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/1831cn86f

The distribution patterns of quartz and opal contents and the distribution patterns of radiolarian assemblages, in the sediments of the southeastern Pacific, are largely controlled by both the surface winds and the mixed-layer oceanic circulation. The distribution pattern of quartz is related to eolian and ice-rafted transport, as well as to runoff. In the subtropical region, quartz distribution extends offshore of Peru as a tongue in the same direction and position as the prevailing trade winds. Along the South American and Antarctic coast, high quartz concentrations are found in patches near shore or abundances commonly decrease rapidly seaward. Opal distribution follows the mixed-layer circulation around the subtropical anticyclonic gyre and shows high values under areas of oceanic divergence, characterized by high primary productivity. Along the continental margins, opal abundances are diluted by terrigenous debris; even off the Peruvian coast, where strong upwelling occurs and consequently high primary productivity prevails The distribution patterns of six radiolarian assemblages, defined through Q-mode factor analysis, reflect the geographical distribution of water masses associated with both surface and subsurface circulation. These are: 1) the surface Antarctic water mass, 2) the surface Subantarctic-Temperate water mass, 3) the Chile Current, 4) the Peru Current, 5) the surface Subtropical water mass and 6) the Equatorial Undercurrent. The Equatorial Undercurrent surfaces either because of strong trade winds or because of considerable relaxed trade winds. The above mentioned distribution patterns have shifted geographically during the Late Quaternary because of global climatic changes (glacial and interglacial stages). Fluctuations in the strength of the winds have been concurrent with fluctuations in the amount of ice stored on the continents, represented by the δ18O stratigraphic record, however, the direction and position of the winds have varied in a rather complex manner. Consequently, the oceanic ...