Doctor of Philosophy (PhD)
Earth Systems Science
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Chile, turbidites, volcanic glass, Nazca Plate, Site 1232, Pleistocene
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A 300 meter sequence of Pleistocene turbidite deposits was recovered on the Nazca Plate at the subducting edge of the Peru-Chile Trench at ODP Site 1232. Analysis of the coarsest particles in the turbidite sequences implies sediment was supplied in some proportion by terrestrial erosion and originated in the coastal, central, and Andean volcanic/magmatic belt which parallels the Southern Chilean coast, and the predominant material type is volcanic. Petrographic and geochemical analyses show that samples from 3 - 140 mbsf contain >43% fresh, angular glass. New calcareous nannofossil biostratigraphy brackets the sediment ages of the upper 288 m of cored section to between 12.47 kyr and 275 kyr. Glass compositional analyses and comparisons with geochemical data from surrounding volcanic sources in southern Chile indicate the volcanic glasses within Site 1232 turbidites originate from a single source. Elemental analyses of individual glass shards show a geochemical signature consistent with origination within the adjacent Andean Southern Volcanic Zone. Similarities in the incompatible element averages and a strong correlation of trace element ratios coincide with published data from the Central Southern Volcanic Zone (CSVZ), more specifically the Puyehue-Cordon Caulle volcanic complex (PCCVC). Investigation into potential transport processes in Coastal Chile from the CSVZ to Site 1232 reveal that with the distance traveled (>250 km), the Site 1232 turbidites are likely to have experienced multiple transport methods. With the lack of turbidite deposition in the Holocene, despite the consistency of sediment delivered to the continental shelf by adjacent rivers, it is unlikely that the Site 1232 sediments were deposited onto the continental shelf solely by fluvial transport. Glacial shifts in wind patterns and ice distribution likely played a strong role in the dispersal and deposition of the glass shards. Understanding the origin and of the Site 1232 glass shards and how they were emplaced will help to illuminate potential volcanic hazards in South Central Chile. To improve our knowledge and develop correct hazard assessments, high-quality volcanic records are required.
Beck, Kimberly D., "Provenance, Composition and Transport Processes of Pleistocene-Recent Turbidite Sediments of the SE Nazca Plate, ODP Site 1232" (2022). FIU Electronic Theses and Dissertations. 5050.
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