Preliminary analysis of grain-size populations with environmentally sensitive terrigenous components in marginal sea setting

Grain-size data have been widely used to determine sediment transport patterns and to reconstruct the sedi-mentary environment. Because the natural occurring sediments deposited in the geologic periods and modern times are mostly mixtures of materials transported from multi-sources or/and by different sedimentary processes, the grain size of bulk samples is an incomplete, approxi-mate index for sedimentary environment changes1,2]. Thus, further studies on the quantitative reconstruction of th…

Preliminary analysis of grain-size populations with environmentally sensitive terrigenous components in marginal sea setting

Terrigenous components were separated from the bulk sediment of Core A7 from the Okinawa Trough and Core A37 from the Ryukru Trench and grain-size distribu-tions of these sub-samples were analyzed. Based upon an analysis of the grain-size data of the two sedimentary se-quences, grain-size populations are identified to be sensitive to sedimentary environmental changes. The modal values and size ranges of the two main grain-size populations in Core A7 are evidently different from those of Core A37, in-dicating the spatial variability of sediment sources and transport processes between the two places. The downcore variations in the content of the environmentally sensitive grain-size populations reveal that during the accumulation of sedimentary material the environment remained relatively stable at the site where Core A7 was collected, except for the apparent events for the formation of two turbidite layers and a volcanic ash layer. However, the sedimentary sequence of Core A37 shows six sedimentary cycles, indicating a highly variable sedimentary environment at this location.