High-resolution sedimentology and micropalaeontology of laminated diatomaceous sediments from the eastern equatorial Pacific Ocean (Leg 138)
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abstract
Scanning electron microscope (SEM)-based analyses of the laminated diatom oozes encountered during Leg 138 reveal three major laminae types. Two lamina associations occur within the laminated intervals; the first comprises alternations of T. longissima Group and mixed-assemblage laminae and the second is composed of T. longissima and nannofossil-rich laminae. The arrangement of laminae probably originates from the deposition of multiple layers of 20 m thick mats from one mat-flux episode. The much thinner nannofossil-rich laminae are interpreted to represent periods of more 'normal' deposition between mat-flux episodes. The occurrence of several varieties/subspecies of T. longissima within individual mat layers is consistent with observations of Rhizosolenia diatom mats in the modern world ocean.