Detrital Sediments of Core MD012403 in Southern Okinawa Trough : Implications for Provenance and Paleoceanographic Changes
Date Issued
2008
Date
2008
Author(s)
Lee, Wen-Hsin
Abstract
High sedimentation rates (50-500cm/kyr) in the South Okinawa Trough (SOT) provide high resolution records for reconstructing millennial or centennial paleo-environment changes. This research analyzes the grain size distribution , clay mineral assemblage and major elements of the IMAGE Core MD012403 retrieved from the Southern Okinawa Trough.he medians of grain size in MD012403 varied from 7.3 Φ to 7.8 Φ during 32.6 ka-20 ka and showed a coarsening trend during 21 ka-10.1 ka. After 10.1 ka, the grain sizes increased to 6.6-7.1 Φ were more stable in association with poor sorting. High content of sortable silt also occurred at this period, indicating the intensity of Kuroshio current was enhanced. he average chlorite / kaolinite ratio of detrital sediments from Taiwan (5.0) is much higher than that from the East China Sea Continental (ECS) Shelf (<2.0). The ratio of chlorite / kaolinite in Core MD012403 shows high values (2-6) during 0 ka-12 ka and maintains low (0.5) between 12 ka-21 ka. This suggests that the ECS may be the major sedimentary provenance during 12 ka-21 ka. oncentrations of MnO、CaO、MgO、ΣFe2O3 in sediment increase with depth but Na2O displays an opposite trend. Aoki and Oinuma(1974) documented that the sediments come from East China Shelf have a significantly low K/Ti ratio. In this study, the ratios of K/Ti drop down during 12 ka-21 ka indicating sources of sediments were mainly from ECS shelf. This interpretation is consistent with evidence also supports the inference derived from clay mineral assemblage.
Subjects
Okinawa Trough
Kuroshio
clay minerals
grain size analysis
major elements
Type
thesis
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