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A 1108.6 m long core was recovered at Site U1457 located on the Indus Fan in the Laxmi Basin of the eastern Arabian Sea during IODP Expedition 355. Shipboard examinations defined five lithologic units (I to V) of the lower Paleocene to Holocene sedimentary sequence. In this study, δ13C values of sedimentary organic matter (SOM) confirm the differentiation of the lithologic units and further divide units III and IV into two subunits (1 and 2). Based on the underlying assumption that the SOM is decided primarily by a mixture of marine and terrestrial origins, δ13CSOM values at Site U1457 provide information on the terrestrial catchment conditions since late Miocene time. Low δ13CSOM values from late Miocene to late Pleistocene times are similar (c. −22.0 ‰) for the most part, reflecting a consistent contribution of terrestrial organic matter from the catchment areas characterized by dominant C3 land plants. Significantly lower δ13CSOM values (c. −24.0 ‰) in Unit III-2 (∼8 to ∼7 Ma) might be due to a greater input of C3 terrestrial organic matter. The increase in δ13CSOM values at ∼7 Ma and the appearance of high δ13CSOM values (c. −18.0 ‰) within Unit III-1 (∼7 to ∼2 Ma) indicate that C4 biomass overwhelmed the terrestrial catchment environment as a result of enhanced terrestrial aridity in the Himalayan foreland. The three-end-member simple mixing model, estimating the relative contributions of SOM from terrestrial C3 and C4 plants and marine phytoplankton, supports our interpretation of the distribution of C3 and C4 land plants in the terrestrial catchment environment. [ABSTRACT FROM AUTHOR]

We present a new set of clay mineral and grain-size data for the siliciclastic sediment fraction from International Ocean Discovery Program (IODP) Site U1456 located in the eastern Arabian Sea to reconstruct the variabilities in the continental erosion and weathering intensity in the western Himalaya, elucidate the sediment source-to-sink processes and discuss the potential controls underlying these changes since 3.7 Ma. The clay minerals mainly consist of smectite (0–90%, average 44%) and illite (3–90%, average 44%), with chlorite (1–26%, average 7%) and kaolinite (0–19%, average 5%) as minor components. The compositional variations in the clay minerals at IODP Site U1456 suggest four phases of sediment provenance: the Indus River (phase 1, 3.7–3.2 Ma), the Indus River and Deccan Traps (phase 2, 3.2–2.6 Ma), the Indus River (phase 3, 2.6–1.2 Ma) and the Indus River and Deccan Traps (phase 4, 1.2–0 Ma). These provenance changes since 3.7 Ma can be correlated with variations in the Indian summer monsoon intensity. The siliciclastic sediments in the eastern Arabian Sea were mainly derived from the Indus River when the Indian summer monsoon was generally weak. In contrast, when the Indian summer monsoon intensified, the siliciclastic sediment supply from the Deccan Traps increased. In particular, this study shows that the smectite/(illite+chlorite) ratio is a sensitive tool for reconstructing the history of the variation in the Indian summer monsoon intensity over the continents surrounding the Arabian Sea since 3.7 Ma. [ABSTRACT FROM AUTHOR]

We investigated the biotic response of benthic foraminifera (Rhizaria) to Holocene paleoceanographic changes in a upper bathyal environment by examining fossil benthic foraminifera younger than ~13 ka from core GH87-2-308 (316-m water depth) off San-in district, southwestern Japan. A non-metric multidimensional scaling (nm-MDS) analysis enabled the distinction of three main benthic foraminiferal assemblages and two faunal transitions. The phase 1 to 2 transition at 11.3 ka was characterized by a rapid decrease in species diversity followed by its gradual recovery and a shift toward present-day fauna. The phase 2 to 3 transition at ~7 ka was characterized by continuation of the shift toward present-day fauna as the Tsushima Warm Current developed and approached its present-day form. The nm-MDS axis 1 was negatively correlated with the radiolarian accumulation rate at this site and with the radiolarian and diatom accumulation rates of neighbor core D-GC-6, suggesting that benthic foraminifera responded to ballasting of particulate organic carbon (POC) with siliceous plankton skeletons. Furthermore, a decrease in the benthic foraminiferal accumulation rate during late phase 2 (~9–7 ka), when warm-water planktonic foraminifera were common, can be attributed to a decreased food supply from the surface ocean because of reduced paleoproductivity beneath a warmer, more stratified surface ocean, possibly accompanied by enhanced remineralization of POC, in response to strengthening of the Tsushima Warm Current. Thus, the benthic foraminifera at upper bathyal depth off San-in district appear to have responded to surface oceanographic changes, suggesting coupling of surface and bottom biota. [ABSTRACT FROM AUTHOR]

Investigation of sediment-trap deployments in the East/Japan Sea (EJS) showed that distinct seasonal variations in particulate organic carbon (POC) fluxes of intermediate-water sediment-traps clearly corresponded to changes in chlorophyll a concentrations estimated from SeaWiFS data. The prominent high POC flux periods (e.g., March) were strongly correlated with the enhanced surface-water phytoplankton blooms. Deep-water sedimenttraps exhibited similar variation patterns to intermediate-water sediment-traps. However, their total flux and POC flux were higher than those of intermediate-water sediment-traps during some months (e.g., April and May), indicating the lateral delivery of some particles to the deep-water sediment-traps. Distinct seasonal δ13C and δ15N variations in settling particles of the intermediate-water sediment-traps were observed, strongly supporting the notion of seasonal primary production. Seasonal variations in δ13C and δ15N values from the deep-water sediment-traps were similar to those of the intermediate-water sediment-traps. However, the difference in δ13C and δ15N values between the intermediate-water and the deepwater sediment-traps may be attributed to degradation of organic matter as it sank through the water column. Comparison of fluxweighted δ13C and δ15N mean values between the deep-water sediment-traps and the core-top sediments showed that strong selective loss of organic matter components (lipids) depleted in 13C and 15N occurred during sediment burial. Nonetheless, the results of our study indicate that particles in the deep-water sediment-trap deposited as surface sediments on the seafloor preserve the record of surface-water conditions, highlighting the usefulness of sedimentary δ13C and δ15N values as a paleoceanographic application in the EJS. [ABSTRACT FROM AUTHOR]

Jeong, S.H.; Khim, B.K..; Jo, Y.H., Kim, B.O., Lee, S.H. and Park, K.S., 2016. Shoreline change rate of the barrier islands in Nakdong River Estuary over the southern part of Korea. In: Vila-Concejo, A.; Bruce, E.; Kennedy, D.M., and McCarroll, R.J. (eds.), Proceedings of the 14th International Coastal Symposium (Sydney, Australia). Journal of Coastal Research, Special Issue, No. 75, pp. 248-252. Coconut Creek (Florida), ISSN 0749-0208. Shoreline data of the barrier islands in the Nakdong River Estuary in Korea for the last three decades were assembled using six sets of aerial photographs and seven sets of satellite images. Canny Algorithm was applied to untreated data in order to obtain a wet-dry boundary as a proxy shoreline. Digital Shoreline Analysis System (DSAS 4.0) was used to estimate the rate of shoreline changes in terms of three statistical variables; End Point Rate (EPR), Linear Regression Rate (LRR) and Least Median of Squares (LMS). Based on Digital Shoreline Analysis, shoreline changes in the barrier islands in the Nakdong River Estuary have varied both temporally and spatially, although the exact reason for the shoreline changes requires more investigation. [ABSTRACT FROM AUTHOR]

We documented the Holocene benthic foraminifera in the coastal deposits based on drilled cores ND-01 (Nakdong River delta, southeastern Korea) and HS02 (Izumo Plain, southwestern Japan). The rapid deepening and subsequent gradual shoaling during the Holocene were recognized from the stratigraphic distribution of five clusters (A to E) and the ratio of planktonic foraminifera to the sum of benthic and planktonic foraminifera (P/T ratio) in core ND-01. Comparison of benthic foraminiferal faunas indicated that the faunal composition differs somewhat between the Nakdong River delta and Izumo Plain or Urauchi Bay (the East China Sea). The relationships between MDS axis 1 and the rarefaction and between MDS axis 1 and the RAC kurtosis showed positive and negative linear-like trends, respectively, in both the Nakdong River delta and the Izumo Plain. The biotic response of benthic foraminifera to taxonomic loss also seemed to be common in that both coastal deposits experienced shoaling or enclosing of the bay environments. Despite the different occurrence of benthic foraminifera between the Nakdong River delta and Izumo Plain, transient changes of benthic foraminifera in both areas at ∼8 ka might have been caused by the enhanced influence of the Tsushima Warm Current. [ABSTRACT FROM AUTHOR]