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Sediment Supply to the South China Sea as Recorded by Sand Composition at IODP Expedition 367/368 Sites U1499 and U1500

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2018, Master of Science, Ohio State University, Earth Sciences.
IODP Expeditions 367/368 drilled the northern rifted margin of the South China Sea (SCS) basin to investigate the timing and mechanisms of its rifting history and to explore its sediment source-to-sink processes. This study examines the mineral composition of sand intervals recovered from two adjacent sites drilled during these expeditions, in order to contribute to understanding these aspects of the evolution of the SCS basin. The sand mineral assemblages at these two sites were interpreted in the context of sand mineral assemblages derived from major sources surrounding the SCS to evaluate the history of sediment supply and the patterns of sand transport throughout the mid-late Cenozoic. Mineral distributions in sand intervals throughout Sites U1499 and U1500 also help to distinguish between rifting models hypothesized for this basin. Sixty-nine samples of medium- to coarse-grained sand and sandstone intervals from Sites U1499 and U1500 were analyzed petrographically. The two sites contain similar lithostratigraphic successions, although unit boundaries occur at different depths. Moving downcore, these units include clay; silty sand with clay and siltstone interbeds; claystone; calcareous-rich claystone; and sandstone. The base of Site U1499 contained sandstone with polymict clasts and matrix-supported breccia, overlying sandstone cobbles. At Site U1499, thin sections from the cobble lithologic unit contain an average framework composition of Q18F74L8; shallower samples are more quartz-rich (average framework composition of Q54F38L8), and some intervals are enriched in mica. Most rock fragments in the cobble interval at Site U1499 are volcanic in origin, whereas the majority of rock fragments in the shallower sediments are plutonic. At Site U1500, thin sections contain an average framework grain composition of Q53F42L5, with limited variability. The majority of rock fragments shifts slightly at Site U1500 from more metamorphic rock fragments to more sedimentary rock fragments up section. The framework grain composition of the upper sediments recovered at Site U1499 is similar to that of the sands at Site U1500, suggesting similar sediment sources for those lithologic units. The upcore shift from plagioclase-rich gravels to quartz-rich sands suggests a change from more proximal to more distal sediment sources. The plagioclase-rich gravels at Site U1499 may record input from granitoid basement rock in southern mainland China, from continental crust exposed during rifting, or from a local basement high formed as a result of rifting. The cobble unit also may have been deposited by a locally sourced gravity flow, based on its limited geographic distribution. The younger sediments may have been supplied by more quartz-rich sediments from the Pearl River or from mica-rich metamorphic basement rocks in Taiwan, which was uplifted during the late Miocene/early Pliocene by collision of the Luzon Arc with the Eurasian Plate.
Lawrence Krissek (Advisor)
Derek Sawyer (Committee Member)
William Ausich (Committee Member)
213 p.

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Citations

  • Robinson, C. M. (2018). Sediment Supply to the South China Sea as Recorded by Sand Composition at IODP Expedition 367/368 Sites U1499 and U1500 [Master's thesis, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1543404762724956

    APA Style (7th edition)

  • Robinson, Caroline. Sediment Supply to the South China Sea as Recorded by Sand Composition at IODP Expedition 367/368 Sites U1499 and U1500. 2018. Ohio State University, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1543404762724956.

    MLA Style (8th edition)

  • Robinson, Caroline. "Sediment Supply to the South China Sea as Recorded by Sand Composition at IODP Expedition 367/368 Sites U1499 and U1500." Master's thesis, Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu1543404762724956

    Chicago Manual of Style (17th edition)