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• First millennial-scale study on erosion and weathering of the western Philippine Sea. • Sea-level lowstand favored erosion and weathering of exposed shelf sediments. • Anthropogenic activity has been a dominant control on Luzon erosion since 2.1 ka. Multiproxy records from Core MD06-3054 in the western Philippine Sea and published results from the nearby Core MD06-3052, which are both located at the northern margin of the Western Pacific Warm Pool (WPWP), provide precise reconstructions and evidence for the potential controls on continental erosion and weathering intensities in Luzon. These data also constrain sediment source-to-sink processes in the sea since 27 ka at the millennial scale. We demonstrate that the siliciclastic fraction is derived from Luzon volcanic rocks and eolian dust from mainland Asia. Stronger physical erosion and chemical weathering generally occurred during the last glaciation, Heinrich Event 1, the Younger Dryas, and the period from 10.3 to 11.3 ka. In contrast, the Bølling-Allerød was characterized by weaker physical erosion and chemical weathering. During the last glaciation, Heinrich Event 1, and the Younger Dryas, the lower sea level led to enhanced erosion and weathering of the exposed shelf sediments. In contrast, the weaker physical erosion and chemical weathering that occurred during the Bølling-Allerød and the Holocene, except after 2.1 ka, are closely correlated with the higher sea level. The stronger physical erosion and chemical weathering at 10.3–11.3 ka may be derived from the reworking of older sediments during the time of a strengthening summer monsoon. Furthermore, enhanced human activity since 2.1 ka has become the dominant control on erosion in Luzon. Rapid weathering changes in the WPWP during the last deglaciation highlight the high variability in local controls at low latitudes during these periods and the potential influence of controls at high latitudes. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • The evolution of the Indian summer monsoon was reconstructed from IODP Site U1456. • The clay-sized detrital sediments are derived from Indus River and Deccan Traps. • A major transition recorded by clay mineralogy at ~0.9 Ma corresponds to the MPT. Abstract Clay mineral assemblages at International Ocean Discovery Program Expedition 355 Site U1456 drilled in the eastern Arabian Sea have been investigated to reveal the sediment provenances and reconstruct the erosion/weathering patterns in the western Himalaya and Indian subcontinent, thus constraining the evolution of the Indian summer monsoon and its forcing mechanism since 1.2 Ma. The clay mineral assemblages at Site U1456 mainly comprise smectite (with an average value of 59%) and illite (with an average value of 33%), with chlorite (with an average value of 5%) and kaolinite (with an average value of 3%) as minor constituents. In terms of sediment provenance, our results indicate that illite and chlorite are predominantly derived from the Indus River, which originates from the western Himalaya and Karakoram, while smectite is primarily sourced from the Narmada River and Tapti River in the Deccan Traps, with a non-negligible contribution from the Indus River in some cases. Variations in smectite/(illite + chlorite) ratio are ultimately controlled by the Indian summer monsoon, which is characterized by approximate glacial/interglacial cyclicity, showing higher values (i.e., enhanced chemical weathering) during interglacial periods. In addition, a major shift in smectite/(illite + chlorite) ratio at 0.9 Ma is correlated to the Mid-Pleistocene Transition (∼1.2–0.9 Ma). Both the Marine Isotope Stage 13 event (533–478 ka) and the Mid-Brunhes Event (∼430 ka) are also recorded in the clay mineral proxies. Based on the spectral analysis, smectite/(illite + chlorite) ratio displays a transition from nonprimary periodicity (29-kyr) to strong eccentricity (100-kyr) and precession (22-kyr) periodicities at approximately 0.9 Ma, which corresponds to the Mid-Pleistocene Transition. Our study indicates that the variability of the Indian summer monsoon at orbital timescales is controlled by high-latitude (i.e., ice volume) and low-latitude (i.e., summer insolation) processes. [ABSTRACT FROM AUTHOR]

We comprehensively investigated sedimentary Hg in Yellow and East China Seas (YECSs), which constitute potentially important depocenters for large anthropogenic Hg emissions from mainland China. A large dataset of Al-TOC-Hg concentrations led to an in-depth understanding of sedimentary Hg in the entire YECSs, including distribution and its determinants, source-to-sink, background levels, inventory in flux and budget, and accumulation history. Especially, the net atmospheric Hg flux to the sediments was estimated to be 1.3 × 10 −5  g/m 2 /yr, which corresponded reasonably well to that calculated using a box model. About 21.2 tons of atmospheric Hg (approximately 4% of the total anthropogenic atmospheric Hg emissions from China) were buried annually in the YECS basin. This result implies that most of atmospheric Hg from China is transferred to the surface of the Pacific (including the East/Japan Sea and South China Sea) by the westerlies and, consequently, can play a critical role in open-sea aquatic ecosystems. [ABSTRACT FROM AUTHOR]

We investigated grain size, clay mineralogy, elemental geochemistry, organic composition, and AMS 14 C dating ages in Core KX12-3 from the middle Okinawa Trough in order to better understand the sediment provenances and transport processes and also the forcing mechanisms behind their variations over the last 18.5 ky. The geochemical–mineralogical indices reveal three notable phases of change in the sediment provenance of the core, which are related to the development of the Kuroshio Current coupled with sea-level fluctuations, the position shift of the mouths of large rivers, the magnitude of tidal bottom stress, and the East Asian monsoon intensity. The sea-level lowstand deposits of Interval 1 (18.5–9.3 ka) formed from mixed sediments originating mostly from Chinese rivers (the paleo-Huanghe and the paleo-Changjiang) as well as from materials eroded from seafloor by the strong tidal stress. Thereafter during Interval 2 (9.3–8.7 ka), a significant sea-level rise, the moderate tidal bottom stress, and a gradual landward retreat of river mouths led to obviously decreased sediment supplies from both seafloor erosion and mainland China rivers (especially the paleo-Huanghe) into to the study area. After this transitional period, the dominant sediment provenance during the mid-to-late Holocene (Interval 3) changed to the Changjiang and seafloor erosion, resulting in lower detrital linear sedimentation rate and finer grain size. At the same time, some fine-grained materials from Taiwan may have been transported northward to the study area by the Kuroshio Current, as evidenced by higher values of chlorite/kaolinite ratio and chemical index of illite, and lower TOC/TN values. In addition, a prominent decline in chlorite/kaolinite values that occurred at 5.0–3.5 ka may have been linked to a suppression of the Kuroshio Current, probably related to the Pulleniatina minimum event and/or the late Holocene Neoglacial cold event commonly found in the northwestern Pacific. [ABSTRACT FROM AUTHOR]

In this study, Holocene changes in the riverine, eolian, and erosional supplies to the eastern part of the central Yellow Sea (YS) and their forcing mechanisms were determined on the basis of multiple mineralogical and geochemical indices of three age-dated piston cores from the central Yellow Sea mud (CYSM) deposition. The core records of the indices, including clay minerals, rare earth element fractionation parameters, and conservative trace elements, revealed abrupt changes in the sediment sources, especially ∼9.0 and 4.8 ka. The late last deglaciation and early Holocene sediments (Units 3 and 4, ∼14.1 to ∼9.0 ka) most likely originated from the paleo-Huanghe and the sea bed erosion, together with some contribution from the paleo-Changjiang Shoal sediments that extended northeastward into the YS. After that period, the dominant sediment source gradually changed to the Changjiang during the middle Holocene (∼9.0–4.8 ka, Unit 2), while the supplies from Huanghe and sea bed erosion to the south YS decreased. In the last 4.8 ka (Unit 1), the CYSM largely received Changjiang-derived sediments. Besides, some clay-sized particulates from the Huanghe, sea bed erosion, and Korea rivers might be transported to the CYSM during Unit 1. Possible mechanisms behind such changes in the riverine and erosional sediment sources and contributions include position shifts of river mouths, tidal stress evolutions, shelf sea-level fluctuations, East Asian monsoon climate changes, and the development of the YSWC and coastal circulation systems. [ABSTRACT FROM AUTHOR]

Despite the well-reconstructed paleoceanography of the late Quaternary deposits in the East (Japan) Sea (ES), provenances of terrigenous sediments and a comprehensive interpretation of their variations since the Last Glacial Maximum remain unclear, especially in regard to the mainland China- and Taiwan-derived matter. Grain size, conservative trace elements, rare earth elements (REEs), Nd isotope, and clay mineralogy of core sediments from the Ulleung Basin of the ES were investigated for better understanding of detrital sediment provenance and transport process and then their forcing mechanisms over the last 21 kyr. Geochemical–mineralogical multi-indices in this study showed notable three-phase changes in sediment provenance, which can be closely related to sea-level fluctuation, development of the Tsushima Warm Current as well as intermittent influence from the East Asian summer monsoon climate evolution. During Unit 1 (21.1–8.4 kyr BP) when the Tsushima Warm Current was absent in the ES, the paleo-Changjiang and the paleo-Huanghe mouth might be situated close to the study area and thus mainland China could have played major role in the southwestern Ulleung Basin sedimentation. In particular, the formation of rhythmic dark-colored alternation in Unit 1 is possibly attributable to the pulse of paleo-Huanghe discharge associated with centurial- to millennial-scale variability in the East Asian summer monsoon. In Unit 2 (8.4–7.2 kyr BP), these river mouths gradually retreated to their present positions with global sea-level rise, leading to decreasing terrigenous sediment supply from mainland China to the study area. Since 7.2 kyr BP (Unit 3), sedimentation in the Ulleung Basin should still be mainly derived from mainland China. Meanwhile, increasing chlorite/kaolinite ratio but decreasing ε Nd value revealed that terrigenous matter from Taiwan might have been limitedly transported northward to the study area by the fully evolved Tsushima Warm Current. A prominent decline in chlorite/kaolinite ratio, together with contrast change on ε Nd value, centered at around 2.9 kyr BP (3.3–2.4 kyr BP) may have been caused by the Tsushima Warm Current suppression, possibly related to the Pulleniatina minimum event popularly found in the study area and nearby seas. [ABSTRACT FROM AUTHOR]

Abstract: Clay mineral assemblage of the core MD06-3047 in the western Philippine Sea has been used to trace sediment provenance and transport process and thus to constrain the East Asian monsoon evolution as well as its forcing mechanism over the past 700kyr. Clay minerals mainly consist of smectite (61%) and illite (23%), with minor chlorite (10%) and kaolinite (6%). Provenance analyses suggest that the smectite originates predominantly from the alteration of nearby Luzon volcanic rocks. Illite is primarily derived from the Asian continent with eolian origin. Illite contents show strong glacial/interglacial cyclicity as constrained by oxygen isotope stratigraphy. Variations of illite contents are ultimately controlled by the East Asian monsoon evolution, characterized by higher illite values during glacials with relatively stronger East Asian winter monsoon but weaker East Asian summer monsoon. During interglacials, enhanced East Asian summer monsoon and rainfall could produce more smectite with poor crystallinity from Luzon to the study core. Spectral analyses of illite content and smectite crystallinity display a strong periodicity at 100kyr for the East Asian winter monsoon and 100kyr, 30kyr, and 23kyr periodicities for the East Asian summer monsoon, respectively, suggesting the unique forcing processes of the East Asian winter monsoon from high-latitudes (i.e., ice volume) and the East Asian summer monsoon from both high-latitudes and low-latitudes (i.e., tropical Pacific). [Copyright &y& Elsevier]

Abstract: A millennial-scale paleoceanographic record of the Ulleung Basin in the southern part of the East (Japan) Sea (ES) for the last 20,000years was reconstructed based on variations in the element compositions of core sediment. Most of the elements showed relatively wide content ranges throughout the core, largely because of different sediment types, their grain size spectra, biological components, and geochemical conditions (i.e., redox conditions). In particular, biogenic components (Ca, Sr, Ba, and CaCO3) and some minor elements (Cu, Mn, Mo, U, Cd, Zn, and V) revealed three distinct intervals of major paleoceanographic changes. Interval 1 (∼18–9.3kyr BP) is characterized by a rhythmic alternation of dark- and light-colored sediment bands. Distinctive differences in the abundance of organic carbon, carbonate, and redox-elements between the dark- and light-colored-sediment layers are probably attributable to especially those associated with bottom-water redox variations combined with the enhanced primary productivity and water stratification in the Ulleung Basin. These alternations perhaps reflect fluctuations in paleo-discharge from Chinese and/or Korean rivers during the last deglaciation. From a global perspective, the repetition of dark sapropelic sediment layers suggests a possible teleconnection between oceanographic change and development of the East Asian summer monsoon and consequent fluctuations in fluvial discharge from Korean and Chinese rivers to the East Sea basin. In Interval 2 (9.3–6.5kyr BP), a remarkable increase in the concentrations of organic carbon and redox elements is probably linked to the intrusion of the warm/saline Tsushima Current to the basin, which would have enhanced ventilation and upwelling of nutrient-rich sub-surface waters. In parallel, a pronounced decrease in carbonate content indicates extensive carbonate dissolution due to the consumption of large amounts of free pore-water oxygen in surface sediments that would have accompanied by the decomposition of organic matter. In Interval 3 (6.5kyr BP–Present), most geochemical parameters are relatively constant, suggesting little changes in paleoenvironments; these observations indicate that modern oceanographic conditions were established in the East Sea at about 6.5kyr BP. In particular, a prominent decline in carbonate contents centered at around 3–4kyr BP appears to have been caused by a decrease in primary productivity in association with a suppression of the warm Kuroshio Current, rather than by geochemical processes. [Copyright &y& Elsevier]

Changes in terrigenous organic matter (OM) input, productivity and the associated bottom-water redox conditions, together with forcing mechanisms and global carbon cycle implications of such variations, on the western margin of the Western Pacific Warm Pool (WPWP) during the Quaternary remain controversial. In this study, we reconstructed the hydrological dynamics, terrigenous OM input, productivity, and deep-sea redox conditions using one core from the continental slope of the Philippine Sea. The new data were integrated with published proxies from the same core and two additional cores from the abyssal Philippine Sea. The results exhibited noticeable variations in the abovementioned indicators, in correspondence to changes in the supply of terrigenous material. The continental slope deposition featured signals of strong physical erosion and chemical weathering of unconsolidated sediments on the exposed continental shelf during the Quaternary sea-level lowstands, which significantly contributed to increased terrigenous OM input and productivity and, in turn, decreased bottom-water oxygenation and atmospheric CO 2 concentrations. In the abyssal Philippine Sea, increased Asian dust-driven OM input and productivity also acted as a sink of atmospheric CO 2 during sea-level lowstands. Analysis of the data suggested that the enhanced terrigenous OM input and biological pump and thus the decreased dissolved oxygen level of the bottom water on the western margin of the WPWP played important roles in modifying the global carbon cycle during sea-level lowstands. In contrast, the influence of hydrological dynamics on terrigenous OM input, productivity, and redox conditions therein during the Quaternary was limited. • First integrative OM and productivity study on the western margin of the WPWP. • Enhanced terrigenous OM input and productivity occurred during sea-level lowstands. • The studied area was an important sink for atmospheric CO 2 during sea-level lowstands. [ABSTRACT FROM AUTHOR]

To obtain a better understanding of the source compositions of the river sediments around the Yellow Sea and their relationship with source rocks, elements and strontium-neodymium (Sr–Nd) isotopes of different grain-sizes (silt and clay populations) and chemical (labile and residual phases) fractionations in riverine sediments were studied extensively. These results clearly revealed a systematic compositional disparity between Korean river (KR) and Chinese river (CR) sediments, especially in the residual (detrital) fraction. The geochemical dissimilarity between these might reflect inherited signatures of their source rocks but with minor control from chemical weathering. In particular, the remarkable enrichment of some elements (iron (Fe) and magnesium (Mg)) and the behavior of large ion lithophile elements (e.g., barium (Ba), potassium (K) and Sr) during weathering as well as less-radiogenic Sr isotopic compositions implies that CR sediments might be weathering products of relatively more mafic rocks, with abundant ferromagnesian and plagioclase feldspar minerals, compared with KR sediments derived from silicic granites with relatively higher quartz and potassium feldspar contents. This different petrological rationale is clearly evident in an A–CN–K diagram, which estimated the source rock of CR sediments as granodioritic, a composition that reflects accurately the average composition of weathered continental crust in China. The recognition of such geochemical systematics in two river sediments, especially in grain-size and chemically partitioned data, may contribute to the establishment of provenance tracers for the Yellow Sea and East China Sea sediments with multi-sources as well the dust deposition in the western Pacific. [ABSTRACT FROM AUTHOR]

Abstract: Authigenic carbonates were sampled in methane-enriched piston core sediments collected from gas venting sites on the western continental slope of the Ulleung Basin, East Sea of Korea. Multidisciplinary investigations on these carbonates, including the scanning electronic microscope (SEM) observations and mineralogical-geochemical compositions, were carried out to identify the carbon and oxygen sources and the forming mechanism of these carbonates. The authigenic carbonates from the study area correspond to semi-consolidated, compact concretions or nodules ranging from 2 to 9cm in size. X-ray diffraction and electron microprobe analyses showed that most of the sampled carbonate concretions were composed of almost purely authigenic high-Mg calcite (10.7–14.3mol% MgCO3). Characteristically, microbial structures such as filaments and rods, which were probably associated with the authigenic minerals, were abundantly observed within the carbonate matrix. The carbonates were strongly depleted in δ 13C (−33.85‰ to −39.53‰ Peedee Belemnite (PDB)) and were enriched in δ 18O (5.16–5.60‰ PDB), indicating that the primary source of carbon is mainly derived from the anaerobic oxidation of methane. Such methane probably originated from the destabilization of the underlying gas hydrates as strongly supporting from the enriched 18O levels. Furthermore, the strongly depleted δ 13C values (−60.7‰ to −61.6‰ PDB) of the sediment void gases demonstrate that the majority of the gas venting at the Ulleung Basin is microbial methane by CO2 reduction. This study provides another example for the formation mechanism of methane-derived authigenic carbonates associated with gas-hydrate decomposition in gas-seeping pockmark environments. [Copyright &y& Elsevier]

• Coastal zoning aids environmental impact assessment. • Sediment textural and geochemical properties are key characters affecting zoning. • This (Ahn et al., 2001) study applies sediment characters to science-based marine spatial planning. • The South Korean coast can be scientifically divided into three zones. The three zones partly coincide with the previous arbitrarily categorized blocks. • A primary factor constraining the zoning in this case study is tidal range. To assess the environmental impacts of offshore wind farming and sea sand mining, coastal areas are zoned on the basis of their natural oceanographic characteristics. Textural and geochemical properties of South Korean coastal sediments, including mean grain size (Mz), CaCO 3 and organic-matter contents, and metal concentrations (Al, K, Ba, rare earth elements, Zr, etc.), were analyzed and categorized in this case study, practically applying common sediment properties for rational zoning of the South Korean coastal environment. Three characteristic zones are scientifically classified in the study area, although four groups of sediment sampling stations were statistically clustered based on their major sediment properties. Zone 1, in the northwestern part of the Korean west coast, is characterized as covered with coarse-grained sediments containing low concentrations of the measured elements under a macro-tidal regime (6.5–9 m), while Zone 3 is characterized by fine-grained sediments with high elemental concentrations under a micro-tidal regime (>3.5 m). Silty Zone 2 sediments appear to be a mixture of sandy Zone 1 and muddy Zone 3 sediments under a meso-tidal regime. The difference in tidal forces among the zones is proposed as a primary constraint of overall sediment textural and geochemical characteristics, while sediment provenance provides subsequent control. Sediment contamination with anthropogenic pollutants is unperceivable in this case study. However, the K and Li concentrations in coarse-grained feldspar and fine-grained illite, respectively, are likely not limited by the tidal flow regime. [ABSTRACT FROM AUTHOR]

Abstract Long marine sequences deposited in the Arabian Sea are suitable to study the orbital sensitivity of sediment dynamics from a source-to-sink perspective. The clay mineralogy and Sr Nd isotopic compositions have been analyzed for the detrital fraction of sediments from IODP Site U1457 located in the Laxmi basin, eastern Arabian Sea to constrain the sediment sources and reconstruct a high-resolution record of sediment export to the Indus deep-sea fan over the past 600 kyr. The 87Sr/86Sr ratio (varying from 0.7154 to 0.7255) and εNd (varying from −12.9 to −9.5) imply a mixing of sediments derived from not only the Indus River but also the rivers draining the Deccan Traps. The variations in the smectite/(illite + chlorite) ratio combined with Sr Nd isotopes permit the reconstruction of past changes in the relative proportions of sediments derived from the Indus River (mainly illite, chlorite and kaolinite) and the Deccan Traps (smectite). The wavelet and cross-spectral analyses further reveal that sediment transport to the eastern Arabian Sea since 600 kyr is mainly dominated by sea-level variations in the eccentricity (100-kyr) band, while the Indian summer monsoon might contribute moderately to the precession (23-kyr) band. The εNd and turbidite frequency indicate that more turbidite events are associated with Indus River-sourced sediments at IODP Site U1457 during sea-level lowstands, which might reflect a reconnection of deep-sea channels to the Indus River mouth and/or reworking of previously deposited Indus River sediments located northward. Highlights • First high resolution clay mineral record from IODP Site U1457 since 600 kyr. • Deccan Traps and Indus River are the main sediment sources for the Laxmi basin. • Clay mineralogy variations from IODP Site U1457 were controlled by sea-level variations. • Turbidite events are associated with Indus River-sourced sediments at IODP Site U1457. [ABSTRACT FROM AUTHOR]

Constraining the dissolved neodymium (Nd) cycle in the ocean is paramount for using Nd isotopic composition ( ε Nd ) as a tracer to reconstruct deep-sea paleocirculations or continental weathering on different time scales. Dissolved ε Nd has been measured in seawater samples from six hydrological stations collected along ∼89°E North–South transect in the Bay of Bengal (BoB) in order to assess the impact of seasonal freshwater and sediment discharges from the continental river systems. Seawater samples collected in this study during June 2012 reveal more radiogenic ε Nd (a difference of ∼2 Epsilon units for the upper 2000 m, and ∼0.5 Epsilon unit below 2000 m) and ∼3–8 pmol/kg lower Nd concentrations than the reported values of nearby seawater samples collected in November 2008. These observations are most plausibly explained by a seasonal variations in dissolved Nd concentrations and ε Nd in the BoB, induced by seasonal variations in the freshwater and sediment discharges from the Ganges–Brahmaputra (G–B) river system. However, we cannot entirely exclude the possibility of spatial differences given that the water stations collected in this study are not exactly the same positions collected in November 2008. A two-box model suggests, (1) the particulate Nd inputs from the G–B river system mainly control the seasonal shift of ε Nd observed in the BoB seawater, and (2) a very rapid Nd exchange exists between lithogenic particles and seawater (at least on the scale of a few months). Seasonal changes in seawater ε Nd may also occur in other marginal seas and in the outflows of major rivers, and these need to be taken into account when using the ε Nd proxy in the ocean. [ABSTRACT FROM AUTHOR]

The late Quaternary paleoceanography and paleoenvironment of the South China Sea (SCS) have been well reconstructed over the last decade. In contrast, the provenance of the terrigenous sediments that have accumulated in the northwestern continental shelf mud area remains enigmatic. This study investigated the provenance of these sediments and the paleoenvironmental changes archived in Core X2 via the analysis of geochemical elements, grain size, and accelerator mass spectrometry (AMS) 14 C ages. Based on the upper continental crust (UCC)-normalized REE patterns and REE fractionation parameters, southwestern and western Taiwanese rivers and the Pearl River were identified as the main sources of the fine-grained sediment deposited in the northwestern shelf mud area off Hainan Island. This finding further confirms the long-distance transport (> 1000 km) of fine-grained sediment from Taiwanese rivers to the northern SCS shelf and slope. Obvious changes in the grain size and Chemical Index of Alteration (CIA) record occurred at approximately 4.0 cal kyr BP and were likely caused by increased Hainan Island inputs due to sea level changes. [ABSTRACT FROM AUTHOR]

High-resolution sea surface temperature records based on long-chain unsaturated alkenones ( U 37 K ′ -SST) in the south Yellow Sea (YS) during the period of 3500–1300 cal. yr BP were reconstructed in sediment core Z8 from the Shandong mud wedge. The SST records show broad variations between 14.3 and 16.9 °C (15.6 °C on the average), with a high SST phase at 3500-2750 cal. yr BP, a low and intense fluctuating SST period at 2500-2000 cal. yr BP and a sharp cooling period at 1750-1300 cal. yr BP. Superimposed on this trend, five cooling periods occurred in 3360–3250 cal. yr BP, 3150–3050 cal. yr BP, 2750–2650 cal. yr BP, 2350–2150 cal. yr BP, and 1750-1300 cal. yr BP. Variation pattern of the SST records is similar to the fluctuations of the Kuroshio Current (KC), indicating a close relationship between the Yellow Sea Warm Current (YSWC) and the KC. The general U 37 K ′ -SST curve fluctuates with the local air temperature variations. The intensity of the East Asia Winter Monsoon (EAWM) could be a key factor affected the prevailing relationship between the cold coastal current and the warm YSWC, and dominated the SST variation in core site Z8 during 3500–1300 cal. yr BP. Furthermore, our temperature records, within age uncertainty, coincides with the changes of the solar irradiance changes, suggesting a possible link between solar forcing and climate variability. [ABSTRACT FROM AUTHOR]

This study analyzed grain size and elemental concentrations (Al, Mg, Fe, and rare earth elements (REEs)) in 91 surface sediments to elucidate sediment provenance in the Yellow Sea. Elemental concentrations were normalized by Al concentration ( C element / C Al ) to minimize the sediment grain-size effect (GSE). However, noticeable linear relationships between Al concentration (or mean grain size) and the ratio (e.g., Mg/Al or Fe/Al) appeared unexpectedly in pair diagrams. The spatial distribution patterns of Fe/Al and Mg/Al ratios were also similar to the pattern of mean grain size. This implies that the GSE was not removed completely, even after the normalization process. Thus, great care must be taken when applying the ratios of C element / C Al as a proxy of sediment provenance. To improve provenance discrimination of the sediments in the Yellow Sea, the difference between the REE distribution patterns of Chinese and Korean river sediments, expressed as δ ( δ = REE ∗ (La) − REE ∗ (Lu)), was calculated, and the spatial distribution patterns of the δ values were mapped. The δ values gradually increased from the western to the eastern part of the Yellow Sea, except for low δ values in the southeastern part of the Yellow Sea. This result indicates that the majority of Chinese and Korean river sediments are accumulating near to their respective coasts, except for a deposit along the southwestern coast of Korea in which a considerable amount of sediment from Chinese rivers has been accumulating. [ABSTRACT FROM AUTHOR]

Discriminating sediment sources quantitatively of several unique shelf-mud deposits in the Yellow Sea has received considerable attention, because they are active sedimentary depocenters that can elucidate the river sediment dispersal patterns and the depositional systems of the sea. Here, we propose a new sediment source proxy model of rare earth elements (REEs) that reflects innate characteristics of their fractionation distribution patterns and provides a reasonable and practical estimation for quantifying sediment source apportionments in the Yellow Sea. REEs of riverine and shelf-mud sediments were granulometrically and chemically partitioned, and the unique characteristics of their fractionation patterns were recorded and numerically indexed. We found distinct differences in the REE fractionation pattern index of riverine sediments, possibly due to the different source rock compositions. Notably, the acid-leached phase of the clay fraction may be a better material for quantitative evaluation of river contributions in the Yellow Sea. Using the REE-source index model presented here, proportional contributions of Chinese river sediments to the central and southeastern Yellow Sea mud deposits were estimated to be 55–80% and 10–40%, respectively, with higher percentage in the leached fraction. Our results elucidate the disagreement between mud budget and river discharge, particularly in Korean coastal mud deposits, as well as the source interpretation of the Yellow Sea shelf-mud deposits, which have been debated since the 1980s. • REEs of the river and shelf sediments were granulometrically and chemically partitioned. • REE fractionation patterns were categorized and indexed to quantify the sediment source. • We proposed a new REE-source index model applicable to the Yellow Sea sediments. • The results provide significant insights on dispersal systems of riverine sediments in the sea. [ABSTRACT FROM AUTHOR]