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To meet the requirements of alumina ceramics in delicate electronics, there is an urgent need for a low-temperature bonding technology that can realize a good combination of alumina and metal. In this work, alumina ceramics and nickel metals were successfully connected at a low temperature (25–150 °C) by Al-Ni self-propagating nanofoil as a heat source. The interface microstructure and element distributions of the solder joints from cross-section and fracture surface were investigated. In addition, the solder joint formation process was simulated by finite element analysis and molecular dynamics. These results showed that their shear strengths could be continuously improved with the growing temperature, which were 17.4 MPa (room temperature, 25 °C), 19.5 MPa (50 °C), 22.9 MPa (100 °C) and 25.69 MPa (150 °C). The Al 2 O 3 /Al-Ni nanofoil/Ni solder joints were prone to crack at the corner and boundary at Al 2 O 3 /solder interfaces due to the stress concentration. Moreover, the increase in ambient temperature not only raises the melting time and transient temperature during the self-propagating reaction, but also improves the interdiffusion of Ni and Sn atoms at the Ni/Sn interfaces. [ABSTRACT FROM AUTHOR]

Understanding marine sedimentary process and the land-sea interaction is vital to human production and life. Gulf of Thailand is a hotspot of such research due to the strong erosion, transportation, and deposition processes under the control of the monsoon climate in the region over the last deglaciation. Based on comprehensive analyses of lithology, grain size, and element index of core BT-7, we revealed that the sedimentary history of this region could be divided into three stages: (I) 13.5–7.5 cal ka BP, continental deposition period, when the central Gulf of Thailand was completely exposed to the surface; (II) 7.5–6.2 cal ka BP, land-sea interaction period, when the material source varied abruptly and the weathering intensity changed significantly, corresponding to frequent climate fluctuations between cold and warm, along with intermittent sea-level still stands; and (III) after 6.2 cal ka BP, period of stable marine sedimentary facies, when the seawater inundated the central Gulf of Thailand, the weathering intensity was slowly weakened with no significant change, and the climate fluctuated with a trend from warm to cold. Notably, since 3.5 cal ka BP, the weathering intensity has been rapidly weakened, entering a small ice age, and the relatively stable sea level has led to a consistent sedimentary environment in the Gulf of Thailand into modern times. Therefore, this study reveals the evolution of sedimentary environment at the interaction of the Indian Ocean and the Pacific Ocean over the last deglaciation. Based on the robust evidence, our findings could help improve the understanding of the sedimentary patterns and land-sea interactions in history. [Display omitted] [ABSTRACT FROM AUTHOR]

To investigate the evolution of sediment provenances and transport processes in the central Bay of Bengal (BoB) since the Last Glacial Maximum, we present a comprehensive study on the grain size, clay minerals, rare earth elements, and accelerator mass spectrometry (AMS)14C analyses of the core BoB-24 sediments. Six AMS14C dates were obtained from planktonic foraminiferal Neogloboquedrina dutertrei (N. dutertrei) extracted from the core to reconstruct a reliable age model. The assemblage of clay minerals and the (La/Yb) UCC –δEu relationship indicated that the core contained a mixture of sediments from the Himalayas and Indian Peninsula. These results showed that the Himalayas were the main source of erosional materials during 25–6.5 ka BP, whereas those from the Indian Peninsula increased since the mid-Holocene. Between 25 ka BP and 12 ka BP, the sea level was relatively low, and a large amount of terrigenous detrital material were directly transported from the Himalayas and the Tibet Plateau to the study area by submarine canyons, forming a deposition center on the Bengal Fan. Between 12 ka BP and 6.5 ka BP, the sea level gradually rose and the Indian summer monsoon gradually strengthened, whereas the sedimentation rate and the amount of material transported from the Ganges–Brahmaputra River decreased greatly; the deposition center transferred from the Bengal Fan to the shelf of the BoB. Since 6.5 ka BP, the sea level has risen, reaching its present position. A high sea level and a strengthened East Indian Coastal Current resulted in an increase of material contribution from India, while the deposition center was on the shelf of the BoB. Overall, this study confirmed that both sea level fluctuations and variations of the Indian summer monsoon controlled the evolution of sediment provenances in the central BoB and transfer of the deposition center from the Bengal Fan to the continental shelf. This typical sedimentary pattern observed in the northeastern Indian Ocean improves our general understanding of past land–sea interactions. [Display omitted] [ABSTRACT FROM AUTHOR]

• Sediments in the eastern Arabian Sea are mainly derived from Indus River and Deccan Plateau. • Terrestrial sources are characterized by a clear glacial-interglacial cyclical change. • Sea level controlled orbital-scale terrestrial inputs and sources in the eastern Arabian Sea. Although the uplift of the Tibetan Plateau has led to strong land-sea interactions, the characteristics of sediment transport and their controlling factors in typical marine areas in the northern Indian Ocean since the Quaternary are not clear. This work aimed to reconstruct the pattern of change in the sources of sediments since the Marine Isotope Stage 9 (MIS 9) period and to explore the mechanism of their response to changes in the marine environment in the Arabian Sea. To this end, a comprehensive multi-indicator study of the chronology and geochemical elements was carried out in core AS05-7 from the eastern Arabian Sea. Major trace element factor analysis and rare earth element (La/Yb) N -δEu N mapping suggested that sediments in the eastern Arabian Sea were mainly derived from terrestrial inputs from the Indus River and the Deccan Plateau. The sediments showed a clear glacial-interglacial cycle of change, with the contribution of the Indus River increasing during the interglacial period and that of the Deccan Plateau increasing during the glacial period. On average, the Indus River and Deccan Plateau contributed 71 % and 29 %, respectively, to the total amount of sediment. Indicators such as mass accumulation rate and Ca/Ti showed that the inputs from the terrestrial sources showed clear glacial-interglacial characteristics, with inputs during the glacial period being higher than those during the interglacial period. The lowering of the sea level during the glacial period led to an increase in the exposed area of the shelf, the shifting of deposition centers closer to the core, an increase in the rate of mass accumulation, and an increase in riverine inputs to the sea when clastic sediments from the Deccan Plateau increased. The elevation of the sea level during the interglacial period led to the inundation of the shelf, the shifting of deposition centers away from the core, a decrease in the rate of mass accumulation, and a reduction in riverine inputs to the sea when detrital sediments from the Deccan Plateau decreased. Changes in terrestrial inputs and sources revealed the orbital-scale control of sea-level change on sedimentary processes in the Arabian Sea and provided direct evidence for the "source-sink" model of sedimentation in the tropical Indian Ocean. [ABSTRACT FROM AUTHOR]

• The Irrawaddy River and Ganges-Brahmaputra rivers are the main sediment sources of the northern Ninetyeast Ridge over the last 50 kyr. • Millennial-scale periodic changes of weathering and terrigenous input are revealed during the last glacial period. • Shift of depositional center from Bengal Fan to the continental shelf is controlled by sea level changes. The Ninetyeast Ridge is situated within the world's largest sediment "source-sink" system, which extends from the Tibetan Plateau to the Bay of Bengal (BoB). Modest and stable sedimentation rate makes it a suitable region for studying long-term land-sea interaction. Recent research has primarily focused on the northern Bengal Fan, leaving limited knowledge about sedimentary processes on the distant Ninetyeast Ridge. This study aims to address this gap by investigating sediment transport pattern and its response to climatic and environmental changes since the last glacial period, using the gravity core (CJ04–50) selected from the northern Ninetyeast Ridge. The provenance discrimination based on δEu-(Gd/Yb) N revealed that the Irrawaddy (Irr) River, along with the Ganges-Brahmaputra (G-B) Rivers, represented the primary sources of the study area. Quantitative analysis equations indicated that the contribution of the G-B Rivers decreased from the last glacial period (22%) to the Holocene period (16%), while that of the Irr River increased (from 78% to 84%). Chemical index of alteration (CIA*) values, and terrigenous input proxy indicators (Ti/Ca, Rb/Sr) were used to indicate the changes of weathering and terrigenous input over the past 50 kyr. During the last glacial period, CIA*, Ti/Ca and Rb/Sr revealed significantly millennial-scale periodic changes, including the distinct declining trend during the Last Glacial Maximum (LGM) and Heinrich 2–4 (H2-H4) periods, followed by recovery trend during subsequent warm periods. During these cold periods of LGM and H2–H4, weakened Indian monsoon condition, reduced precipitation, cold climate, and expanding ice sheets, adversely affected physical erosion and chemical weathering in the source area, and the reduced river runoff impeded sediment transport. Conversely, these environmental factors reversed during relatively warm periods. Since the Holocene, CIA*, Ti/Ca and Rb/Sr declined, which was contrast to the climate change, and the sea level changes became the dominant factor. The rapidly rising sea level submerged the main terrigenous input channel (the Swatch of No Ground) of the G-B Rivers, made the depositional center shift from the Bengal Fan to the continental shelf, causing the decline of terrigenous input and lower CIA* values. [ABSTRACT FROM AUTHOR]

• The residual sediments were concentrated in the central of the Malacca Strait, while the modern terrigenous sediments were distributed along the coastal side. • The sedimentary environment in the Malacca Strait presented residual, reworked, and modern characteristics. • The sedimentary dynamics restricted the transport of modern terrigenous sediments from the coast to the central region of the Malacca Strait. The Malacca Strait is not only a part of shelf deposition but also a crucial conduit connecting the continental shelf to the deep ocean. Here, we present the grain size characteristics of sediments in the Malacca Strait and regional hydrographic data obtained from global models to delineate its depositional configurations and further identify its sedimentary environments. The results reveal that the residual sediments are concentrated in the central region of the strait, whereas the modern terrigenous sediments are distributed along the coast of Malaysia and the broad northern region of the strait. The central region of MS, ProvinceⅠ, has the coarsest sediments with moderate sorting, indicating a residual sedimentary environment where the sands are residual paleo-river deposits. There are poorly sorted silty sands in ProvinceⅡ, which display finer mean grain size than that of ProvinceⅠ. It suggests a reworked sedimentary environment with variations of sediment sources between the southern and northern regions. It is a palimpsest of the paleo-deltaic deposits in the southern region, which have been intensely altered by modern high-energy hydrodynamic conditions. In terms of the northern part of ProvinceⅡ, it has modern reworked deposits shaped by wave, tide, and monsoon currents. The finer sediments, which correspond to the distribution of higher silt content, are supplied by the surrounding land in ProvinceⅢ indicating a modern environment primarily influenced by seasonally varying sedimentary dynamics, such as monsoon currents, well-developed eddies, and water masses. We thus propose that the depositional configurations in the Malacca Strait are confined by depositional dynamic environments, which restrict modern terrigenous sediments distributed along the coast and scarcely transported into the central region of the strait which exposes residual deposits. This study highlights the importance of both modern and relict sediments in the strait and our findings are important to better understanding modern strait sedimentary systems with high tidal-current-energy. [ABSTRACT FROM AUTHOR]

• Clay minerals are mainly derived from terrestrial sources input from the Irrawaddy River. • Solar activity controlled the weathering and sedimentation of fine-grained sediments. • Monsoon precipitation controlled the millennial supply and transport of fine-grained sediments. The uplift of the Tibetan Plateau has led to the formation of the world's largest sediment "source–sink" system in the northeastern Indian Ocean, and seafloor sediments record rich environmental and climatic information during the accumulation process, making it an ideal area to reconstruct past sedimentary processes. To reveal fine sediment provenance and climatic implications, we present a sedimentary reconstruction during the past 42 kyr based on clay mineral analyses of sediments from core ADM-159 retrieved from the central Andaman Sea. The clay minerals mainly consist of illite (I, 27%–47%) and kaolinite (K, 8%–37%) with minor smectite (S, 11%–37%) and chlorite (C, 11%–37%). Provenance analyses show that the illite-dominated clay minerals are mainly derived from terrestrial sources of detrital material input from the Irrawaddy River, indicating a primary supply of fine sediment from Myanmar terrestrial material. Considering the stable sediment provenance, S/K, S/(I+C), and the illite chemical index were chosen to reconstruct the transport pattern of the fine fraction sediment over the last 42 kyr. S/K and S/(I+C) showed relatively consistent trends over time with relatively high values at 32–25 and 15–6 ka BP, indicating a strong supply and transport capacity of fine particulate matter. In contrast, relatively low values of S/K and S/(I+C) occurred at 25–15 ka BP, indicating a relatively weak deposition process of fine sediments in the study area. The trends in S/K and S/(I+C) are roughly consistent with the variations in solar radiation. Together with the illite chemical index, these trends indicate that solar activity controlled the weathering and sedimentation of fine-grained sediments. We also found significant periodicities in our clay mineral records at 25.05 and 0.473–0.477 kyr, suggesting that the parameters of the Earth's orbit and solar radiation were potential driving mechanisms of the changes in regional climate. Moreover, monsoon precipitation triggered by the movement of the intertropical convergence zone was another important factor controlling the supply and transport of fine particulate matter in the study area, especially the weak precipitation during the last deglacial period and the relatively strong precipitation during the Holocene, so we could draw a conclusion that precipitation during these periods had significant effects on the weathering, erosion, and transport of fine particulate terrestrial materials over the last 42 kyr. [ABSTRACT FROM AUTHOR]

[Display omitted] • Sediments in the southern Bay of Bengal mainly sourced from terrestrial materials transported by inflow rivers. • Multiple rivers dominated the glacial sediment provenance, whereas Indian peninsula materials increased during the Holocene. • Chemical weathering on glacial-interglacial scales was controlled by solar insolation. • Millennial variations of chemical weathering matched well with the Indian monsoon system. Chemical weathering has a significant role in controlling sediments production and transport, both of which are closely linked to environmental conditions and climate change. This study examines BoB-79, a core located in the southern part of the Bay of Bengal (BoB), to investigate the chemical weathering of terrestrial materials since the last glacial period in the Indian Ocean. Multiple geochemical proxies were employed to reconstruct the weathering history and to establish links with global and local environmental shifts. Analysis of rare earth element (REE) indices pinpointed terrestrial materials as the main sediments provenance in the southern BoB. During the last glacial stage, the sediments in core BoB-79 were sourced from multiple rivers surrounding the BoB; these deltaic systems prograded, leading to a mixture of sediments being transported to the southern BoB. Conversely, during the Holocene stage, the sedimentary signature from core BoB-79 more closely resembled that of the Krishna-Godavari rivers, indicating an increased terrestrial supply from the Indian Peninsula. Collectively, TiO 2 , the chemical index of alteration (CIA), αAlNa, and the illite chemical index were observed to align with changes in solar radiation intensity in the northern hemisphere. Millennium-scale fluctuations might be attributed to global climate events such as Heinrich 1 (H1), Younger Dryas (YD), and Bølling/Allerød (B/A) through the Indian monsoon system. Thus, investigation into the chemical weathering process and its reaction to changes of solar insolation and the Indian monsoon provide compelling evidence for understanding air-sea interactions in the southern BoB since the last glaciation. [ABSTRACT FROM AUTHOR]

To understand the modern sedimentation and land-sea interaction processes in the Asian margin seas, we analyze rare earth element contents (REE, i.e., La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu) and grain sizes, detrital minerals from 158 surface sediment samples collected from the western Gulf of Thailand (GoT). The results reveal that the REE contents ranged from 25.42 μg/g to 201.21 μg/g, with an average value of 137.21 μg/g, and that the GoT is characterized by higher accumulations of LREE relative to HREE, together with negative Eu anomalies. Based on the spatial distribution characteristics of REE contents, δCe and δEu, the western GoT can be classified into three geochemical provinces. The Province I covers the northern and northwestern coastal zones of the GoT, including the entire upper GoT; its coarse size fraction and distribution pattern of hornblende- and quartz-dominated minerals caused REE contents to be the lowest, and these sediments were mainly derived from the rivers around the upper GoT, including the Chao Praya River and the Kea Klong River. The Province II is located in the central GoT and has the highest REE concentrations due to finer sediment composition and higher contents of zircon, authigenic pyrite, and biogenetic limestone. The Province II has two accumulation centers around Samui Island and Koh Chang Island, with REE spatial distribution influenced by the seasonal setting and mixed derived from multiple provenances around the GoT. The Province Ш is located in the lower GoT, close to Malaysia. The sediment type in this region is similar to that of Province I except for different detrital mineral compositions, especially the presence of siderite that is responsible for higher REE contents. The sediments in this region exhibits similar distribution patterns to those of terrestrial materials from the Malaysian peninsula such as that from the Kelantan River. The transportation processes of sediments in this region are mainly controlled by the coastal current. [ABSTRACT FROM AUTHOR]

• An oxic condition was identified by geochemical proxies in the southwestern Sumatra waters over the past 35,000 years. • Semi-precession cycles of marine redox environment in the tropic Indian Ocean were revealed. • Millennial-scale variability of marine redox environment was driven by the ITCZ movement and regional monsoon changes. The marine redox environment (MRE) can affect marine productivity and nutrient cycling, as well as governs material and energy transport. However, its evolution process and driving mechanism in different historical periods revealed significant regional characteristics. Southwestern Sumatra waters, located at the Indo-Pacific Ocean convergence, are an ideal region for studying the evolution of MRE due to significant upwelling and variable productivity levels resulting from the seasonal monsoonal activity. In this study, based on the sediment core SO184–10043, systematic trace element geochemical analysis was conducted for reconstructing the MRE over the past 35,000 years using redox proxies, namely, Ni/Co, U/Th, and biogenic Barium (Ba bio). Ni/Co and U/Th varied in a range of 1–4 and 0.2–1, indicating general oxic conditions with matching productivity levels indicated by Ba bio (ranging from 300 × 10–6 to 580 × 10–6). A comparison with other reconstructed archives indicated that the MRE records of the sediment core in this study were in consistence in responding to the high-latitude climate records with strong semi-precession and millennial fluctuations. Suggestively, these fluctuations correspond to the natural summertime insolation, triggering the latitudinal motions of the Intertropical Convergence Zone (ITCZ), as well as leading to corresponding changes in the seasonal Indian monsoon system. Freshwater lids modulate the mixing effect by acting as barriers and influencing the upwelling development, thereby leading to strong oxic conditions in the MRE. Therefore, robust evidence on the millennial-scale variability in MRE driven by the ITCZ movement and regional monsoon changes in the tropical Indian Ocean is provided by the trace element archives employed in the present study, thereby providing novel insights into the evolution of MRE in response to global and local climate changes. [ABSTRACT FROM AUTHOR]

Abstract Grain size, clay mineralogy, 87Sr/86Sr, εNd, and AMS14C analyses of deep-sea sediments cored in the central Bay of Bengal are used to reconstruct the evolution of provenances and climate control since the last glacial period. Clay minerals, 87Sr/86Sr ratios and εNd values indicate a mixture of sediment from the Himalaya source, Indian Peninsula and Indo-Burman Ranges/Irrawaddy River. These analyses show that the Himalaya Mountains and Indo-Burman Ranges/Irrawaddy River are the main suppliers before the Holocene period, while the inputs of erosion materials from the Indo-Gangetic floodplain and the Indian Peninsula increase during the Holocene period, accompanied by reduced inputs of the Indo-Burman Ranges and Irrawaddy sediments. The regional "source-sink" process is significantly controlled by the climate. Warm and wet climate conditions and enhanced Indian monsoon intensity during the Holocene period are responsible for the increase of sediment input from the Indo-Gangetic Plain and the Indian Peninsula by improving erosion in the source area, input from the floodplain to the river channel and the intensity of the southwest monsoon current. In contrast, due to the decrease of the northeast monsoon current during the Holocene period, sediment input from the Irrawaddy and Indo-Burman Ranges are constrained. Deposition center transition between the submarine fan and shelf during the last glacial period and the Holocene period occurs in response to the sea level change, which controls the sedimentary mode and thus significantly influences the transportation and deposition processes in the Bay of Bengal (BoB). [ABSTRACT FROM AUTHOR]

[Display omitted] • Systematic combination and comparation of bedload and suspended load of river sediment. • Effective separation of provenance, weathering and deposition signals in river sediment. • Testing the application of extracted river sediment provenance signals to marine sediment. River sediments compositions in Bangladesh were measured to extract effective signals of chemical weathering, sedimentary processes and provenances and applied to sedimentary record in the Bay of Bengal (BoB). Weathering indexes including the chemical index of alteration (CIA), weathering index of Parker (WIP), αAlE and related diagrams indicated overall weak to intermediate chemical weathering intensity in modern Ganges-Brahmaputra-Meghna (G-B-M) catchment. Sedimentary processes controlled sediment mineralogical and chemical composition to a certain extent, as reflected in the distinctions between suspended loads and bedloads. The suspended loads were richer in phyllosilicates than the bedloads in the Brahmaputra and the Meghna River sediments, and the Meghna River bedload exhibited sedimentary recycling and quartz dilution features. The Ganges River sediments showed multiple recycling and source mixing features. Extracted provenance proxies indicated that the Brahmaputra River sediments got relatively more effects from Himalayan mafic to intermediate rocks, while the Ganges River sediments indicate a mixture from the Himalaya and Indian Peninsula. more effects from ultramafic rocks were revealed for the Meghna River sediments. By comparing the extracted provenance proxies of different rivers and applying them to the identification of sediment sources in the Bay of Bengal (BoB), the Brahmaputra River is suggested to have been the primary supplier of sediments to the central-northern BoB since the last glacial period as a result of the highest erosion rate in the eastern syntaxis, which provides a new understanding of the sediment "source-sink" process in the BoB and indicates that effective extraction of fluvial information is crucial for marine sedimentology studies. [ABSTRACT FROM AUTHOR]

A paleoenvironmental reconstruction of the East China Sea (ECS) is presented using rare earth element (REE) analysis of sediments from Core MZ02, which was retrieved from the inner continental shelf's mud area. The analytic results show that the total REEs in the fine sediment vary between 137.76 μg/g and 231.53 μg/g with an average value of 187.69 μg/g. Obvious changes were found during the process of sedimentation. By comparing with the REE compositions from the potential provenances, the ratios of (La/Sm)ucc and (Gd/Yb)ucc revealed that the sediments were mainly derived from river detrital outputs of the Changjiang (Yangtze River), Minjiang and mountainous rivers from western Taiwan Island. The contributions of terrestrial materials from these three main provenances were controlled by sea level change and the Taiwan Warm Current (TWC)-Chinese Coastal Current (CCC) system, which is mainly driven by the East Asian monsoon. The high sedimentation rate during the transgression period between the late Pleistocene and early Holocene (13000–9800 a B.P.) was caused by a well-proportioned mixed provenance from Changjiang, western Taiwanese rivers and Minjiang sediments, due to the lower sea level and the location of the foreshore-nearshore face. Because of the stronger sediment reworking and erosion at the shelf edge during the early Holocene (9800–7300 a B.P.), the strengthening summer East Asian monsoon transported the Minjiang and western Taiwanese river material northeastward, and it became the main sediment source for fine sediments in the shallow sea region of the ECS, while the Changjiang provided a relatively minor amount of detrital sediment to the shelf. The increasing strength of the TWC might have played an important role in sediment dispersal and deposition on the ECS inner shelf during the period 7300–3500 a B.P., thus mountainous river material became the dominant sediment on the shelf of the ECS. Furthermore, the results indicate that the East Asian monsoon and the weakening of the TWC were linked to an abrupt increase in Changjiang-derived terrigenous detritus material since 3500 a B.P.; the source and sink pattern during this period is consistent with the modern sedimentation environment. [ABSTRACT FROM AUTHOR]

The clay mineral contents in 110 surface sediment samples collected from the middle of the Bay of Bengal were analyzed by X-ray diffraction (XRD) to investigate the provenance and transport patterns. The illite content was highest, followed by chlorite, kaolinite and then smectite, with average weight percent distributions of 52%, 22%, 14% and 12%, respectively. Illite and chlorite had similar distribution pattern, with higher contents in the northern and central areas and lower contents in the southern area, whereas smectite showed the opposite distribution pattern. Kaolinite show no obvious higher or lower areas and the southern “belt” was one of the highest content areas. Based on the spatial distribution characteristics and cluster analysis results, the study area can be classified into two provinces. Province I covers the southwestern area and contains high concentrations of illite and smectite sediments. Province II covers most sites and is also characterized by high concentrations of illite, but the weight percent of smectite is only half of that of province I. According to a quantitative estimate using end-member clay minerals contents, the relative contributions from the Himalayan source and the Indian source are 63% and 37% on average, respectively. Integrative analysis indicates that the hydrodynamic environment in the study area, especially the turbidity and surface monsoonal circulation, plays an important role in the spatial distribution and dispersal of the clay fraction in the sediments. The sediments in province I are mainly from the Indian source transported by the East Indian Coastal Current (EICC) and the surface monsoon circulation with minor contributions from the Himalayan source while the sediments in province II are mainly from the Himalayan source transported by turbidity and surface monsoonal circulation with little contribution from Indian river materials. [ABSTRACT FROM AUTHOR]

A 35.30 m-long core (MZ02) that was recovered from a water depth of 32.4 m from the inner shelf mud deposit of the East China Sea is analyzed to determine its sedimentary characteristics, color reflectance, clay mineral content, element geochemistry components and AMS 14 C dating to investigate the sedimentation rate, sediment provenance and paleoclimate evolution during the fast transgression period. Rare earth element and clay mineral proxies indicate that mixed-provenance sediment accumulated in the foreshore–nearshore region at the beginning of the fast transgression period, with a higher sedimentation rate of 5.58 m/ka. From the early Holocene (9.8–9.5 ka B.P.), the sedimentation rate declined by approximately 1.73 m/ka, and the sediment provenance obviously changed. The silt fraction resembled that of Taiwan's mountainous rivers and the clay fraction was primarily transported from the Yangtze River. A multiple proxy system including sediment redness (a*), chemical index of alteration (CIA), clay mineral ratio (smectite/kaolinite), and major and trace element ratios (CaO/MgO, Ba/Sr), also provides a good paleoclimate record during the fast transgression period, which can be divided into three units. All the proxies barely changed during Unit I (12.88–10.85 ka B.P.), revealing that the climate remained relatively stable. Obvious fluctuations occurred during Unit II (10.85–10.05 ka B.P.), and the temperature kept decreasing for more than 1 ka until the Younger Dryas event, showing a notable regional response to global climate changes. A continuous warming trend resumed again during Unit III (10.05–8.15 ka B.P.), which may mark the threshold of the Holocene warm period. In addition, we find significant 80-yr, 89-yr and 100-yr cycles in the CIA, CaO/MgO and Ba/Sr records, which imply the possible influence of solar activity on regional climate change during the fast transgression period in the Asian margin region. [ABSTRACT FROM AUTHOR]

In the Indian monsoon realm, spatial homogeneity of hydroclimate response to glacial abrupt climate events in the North Atlantic Ocean and its underlying mechanism are contentious. Here we reconstruct sea surface temperature (SST) and seawater oxygen isotope (δ18O sw) in the central Andaman Sea, which span over the past 26,000 years, to investigate the potential driving mechanism of millennial-scale climate changes in tropical Indian Ocean. Our results demonstrate that millennial-scale SST and δ18O sw changes during the last deglaciation are associated with changes in Asian monsoon system which follows North Atlantic climate changes. In particular, during the transition from BØlling/AllerØd (B/A) to Younger Dryas (YD), the strengthening of East Asian winter monsoon (EAWM) promotes southward invasion of northern cold air masses to Indo-China Peninsula, cooling the Andaman Sea. Meanwhile, the enriching δ18O sw is a consequence of reducing local rainfall amount and Irrawaddy River inflow due to a weakening Indian summer monsoon (ISM). With aid of an isotope-enabled climate model, our results further demonstrate that the changes in EAWM and ISM during B/A-YD transition are closely coupled with variations of Atlantic meridional overturning circulation (AMOC), corroborating its pivotal role in millennial-scale changes in tropical Indian Ocean hydroclimate during the last deglaciation. • Andaman Sea characterizes abrupt changes in sea surface temperature and δ18O of seawater during the last deglaciation. • δ18O sw and precipitation are characterized by spatial homogeneity of response to abrupt climate change in North Atlantic. • Millennial-scale temperature changes in Andaman Sea show a local feature controlled by East Asian winter monsoon. [ABSTRACT FROM AUTHOR]

In this study, we analyze major and trace elements (SiO 2 , Al 2 O 3 , Fe 2 O 3 , CaO, K 2 O, MgO, Na 2 O, TiO 2 , P 2 O 5 , MnO, Cu, Pb, Ba, Sr, V, Zn, Co, Ni, Cr, and Zr) and grain size of 157 surface sediment samples from the western Gulf of Thailand (GoT). On the basis of the space distribution characteristics, the study area can be classified into three geochemical provinces. Province I covers the northern and northwestern coastal zones of the GoT, including the whole upper GoT and thus the sediments from the rivers in the area. It contains high contents of SiO 2 . Province II is located in the middle of the GoT and has similar geochemistry composition as the South China Sea (SCS). It contains sediments that are characterized by higher contents of Na 2 O, TiO 2 , Ba, Cr, V, Zn, Zr, and Ni. Province Ш is located in the lower GoT, close to Malaysia. Major and trace elements in this area showed complex distribution patterns, which may be due to terrestrial materials from Malay rivers combining with some sediments from the SCS in this province. The results also indicate that grain size is the controlling factor in elemental contents, and that the hydrodynamic environment and mineral composition of the sediments play an important role in the distribution of these elements. The anthropogenic impact of heavy metal introduction (especially Cr, Zn, Cu, and Pb) can be seen in surface sediments from the nearshore region of Chantaburi province and north of Samui Island. [ABSTRACT FROM AUTHOR]

The ocean heat content (OHC) and associated surface stratification in tropical oceans are ideal variables to monitor global climate change. However, the variations in surface stratification of the tropical Indian Ocean at the millennial time scale have been less understood. In this context, the present study aimed at reconstructing the sea surface temperature (SST) and thermocline water temperature (TWT) using Mg/Ca of planktonic foraminifera in the sediments of the Andaman Sea, which is one of the hot centers in the Indo-Pacific warm pool (IPWP) over the past 42 ka. The study results confirm the SST changes are consistent in response to the high-latitude temperature records with strong sub-orbital and millennial variations, while the TWT patterns trend remarkably different from the millennial-scale SST and show the variations correspond to the natural summer insolation that triggers the latitudinal movements of the Intertropical Convergence Zone (ITCZ). Furthermore, salinity influences the thermal differences (ΔT=SST-TWT) by varying the vertical temperature and stratification. Analysis of available data shows that the mean northward position of ITCZ would input more freshwater into the Andaman Sea. Freshwater lids can reduce mixing by acting as effective barriers and preventing heat from transferring from the surface to the subsurface, thereby causing subsurface cooling and increased stratification. In contrast, more southward ITCZ (boreal winter monsoon) supplies less freshwater into the Andaman Sea. A highly saline surface water and air cooling promotes mixing and subsurface warming, resulting in decreased stratification. The study results reveal a millennial-scale vertical thermal seesaw synchronizing in the tropical Indian Ocean with abrupt Atlantic meridional overturning circulation (AMOC) changes. During the Bolling-Allerod (B/A) warming period, the dynamic AMOC maintains the surface water stratification by controlling the subsurface cooling processes with increased precipitation and freshwater brought by the northward ITCZ. In contrast, Younger Dryas (YD) and Heinrich events (H) are characterized by reduced summer monsoon precipitation associated with the sluggish AMOC and southward ITCZ, resulting in less stratification and subsurface warming in the Andaman Sea. The thermal proxy records adopted in the study afford robust evidence on the millennial-scale variability in surface stratification driven synchronously by AMOC and regional evaporation vs. precipitation changes in the tropical Indian Ocean, offering new insights into the impacts of the IPWP OHC on abrupt climate changes. • Millennial-scale climate variability was reconstructed by SST and TWT in the Andaman Sea. • Salinity influences the thermal differences (ΔT) by varying the vertical temperature and stratification. • Millennial scale variability of surface stratification was driven synchronously by AMOC and tropical dynamic changes. [ABSTRACT FROM AUTHOR]

In this study, we explored the heavy metal elements in 42 surface sediments from the Malacca Strait in terms of distribution, controlling factors, environmental quality, and primary sources. An analysis of grain size revealed finer sediments near the coast of Malaysia, which gradually thickened toward offshore. In addition, heavy metal elements were abundantly distributed near the coastal area of Malaysia, with a gradual decrease toward the sea; their content increased within waters close to the Perak estuary. Source analysis of heavy metals showed that Cr, Hg, Zn, Cd, and Cu were mostly derived from natural weathering, and their distribution was significantly influenced by sediment grain size. As and Pb were affected by human activities. The environmental quality assessment results showed that Cu, Cr, Cd, and Zn in our study regions were pollution-free. Pb elements showed low-to-moderate pollution, and Hg showed a certain degree of ecological risk due to its high toxicity coefficient. The content of As elements in surface sediments increased significantly when compared to the background value, with several evaluation methods indicating a high-risk index. According to these findings, the area near the mouth of the Perak River is the most polluted, followed by the surrounding coastal areas. • Cu, Cr, Cd, Zn were pollution-free, Pb showed low-to-moderate pollution. • Hg showed a certain degree of ecological risk due to its high toxicity coefficient. • As element within surface sediments showed a high-risk index. • The Perak River mouth is most polluted, followed by the surrounding coastal areas. [ABSTRACT FROM AUTHOR]

A high density sampling program during two joint China–Thailand scientific cruises in 2011–2012 included collection of 152 gravity box cores in the Gulf of Thailand (GoT). Samples from the top 5 cm of each core were analyzed by X-ray diffraction for clay mineral content. Several systemic analytical approaches were applied to examine the distribution pattern and the constraint factors of clay minerals in the surface sediments of the western GoT. The clay minerals mainly comprise illite, kaolinite, chlorite and smectite, having the average weight percent distributions of 50%, 34%, 14% and 2%, respectively. Based on the spatial distribution characteristics and statistical results, the study area can be classified into three provinces. Province I contains high concentrations of smectite, and covers the northern GoT, sediments in this province are mainly from rivers discharging into the upper GoT, especially the Chao Phraya and Mae Klong Rivers. Sediments in Province II are characterized by higher values of illite, located in the central GoT, where fine sediments are contributed by the Mekong River and from the South China Sea. Province Ш, in the coastal regions of southwestern GoT close to Malaysia, exhibits a clay mineral assemblage with complex distribution patterns, and may contain terrestrial materials from the Mae Klong River as well as re-suspended sediments. Results of integrative analysis also demonstrate that the hydrodynamic environment in the study area, especially the seasonal various circumfluence and eddies, play an important role in the spatial distribution and dispersal of clay fraction in sediments. [ABSTRACT FROM AUTHOR]

A novel and simple method for preparing Mg–50%Al 4 C 3 (hereafter in wt.%) master alloy has been developed by powder in-situ synthesis process under argon atmosphere. X-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDS) results show the existence of Al 4 C 3 particles in this master alloy. After adding 1.8% Mg–50%Al 4 C 3 master alloy, the average grain size of α-Mg decreased from 360 μm to 154 μm. Based on the DTA test results and calculation of the planar disregistry between Al 4 C 3 and α-Mg, Al 4 C 3 particles located in the central regions of magnesium grains can act as the heterogeneous nucleus of primary α-Mg phase. [ABSTRACT FROM AUTHOR]

We present a paleoclimatic reconstruction for the Holocene by clay mineral analyses of sediments from core MZ02 retrieved from the mud area of the inner continental shelf of the East China Sea (ECS). The clay minerals mainly consist of illite (66%–79%) and chlorite (12%–19%), with minor kaolinite (7%–13%) and smectite (0–6%). Provenance analysis suggests that the illite-dominated clay minerals were derived mainly from the detrital outputs of the Changjiang, Minjiang, and small rivers from Taiwan Island. Our study indicates that the sea level rise since the last glacial, the strength of the Taiwan Warm Current (TWC) and Chinese Coastal Current (CCC) have controlled the dispersal and deposition of clay minerals on the ECS, that in turn determined the clay mineral compositions in the core sediments. During 13,000–9500 BP, due to the lower sea level and shorter distance between these three estuaries and core MZ02, fine sediments on the inner shelf of the ECS were primarily supplied by mixed provenances from the Changjiang, Taiwanese, and Minjiang rivers. During the early Holocene (9500–6200 BP), stronger sediment reworking and erosion at the shelf edge was responsible for the increased lateral transport of fine sediments in the ECS, which lead to a dominance of the sediment source from the Changjiang, while the Taiwanese and Minjiang rivers only provided minor components of detrital sediment to the shelf. Increased strength of TWC might have played an important role in the sediment dispersal and deposition on the inner shelf of the ECS during 6200–2400 BP, with a dominance of more than 60% sediments transported from Taiwanese rivers. Furthermore, our study implies that the Asian monsoon and the weakening of TWC were linked to the abrupt increase of Changjiang and Minjiang derived terrigenous detritus materials since 2400 BP. [ABSTRACT FROM AUTHOR]

[Display omitted] • Millennial-scale climate variability in the Bay of Bengal is reconstructed by TEX 86. • Warming trend during millennial-scale cold events is revealed in the northern Indian Ocean. • Atmospheric CO 2 force SST change during the millennial-scale cold events over the past 40 kyr. To better understand the process of hydrographic and temperature changes in the Indian Ocean, we present Glycerol dialkyl glycerol tetraether data on core BoB-56 from the Bay of Bengal to reconstruct the sea surface temperature (SST) variability during the last glaciation. The results indicate that the TEX 86 -derived SST ranged from 22.00 to 28.30 °C with several fluctuations since 40 ka BP and that the evolution pattern matched well with the marine isotope stage (MIS). During MIS 3, the SST kept around 24.60 °C with some small amplitudes. The SST showed more significant fluctuations during MIS 2 and increased gradually with a ~3 °C cooling during the Last Glacial Maximum (LGM). After the Younger Dryas (YD) stage, Holocene SST values exhibited miniscule variations. During the last glaciation climate variability process, the cold signals of the YD and Heinrich events were recorded well in our core SST series, revealing a regional response to global climate changes. The warming trend during these millennial-scale cold events in the northern Indian Ocean was also identified, and SST increased in the range of 2 °C. A comparison of SST records and atmospheric CO 2 concentration shows that the warming process during the YD, LGM, and Heinrich (1–4) events matched the gradual increase in atmospheric CO 2 concentration in the northern Indian Ocean. Hence, this study implies millennial-scale hydroclimate change linked with atmospheric CO 2 forcing that could improve our knowledge of the role of atmospheric CO 2 in triggering abrupt Indian Ocean climate changes. [ABSTRACT FROM AUTHOR]

Changes of marine paleoproductivity could reflect the history of marine biogenic cycle process, and exploring the evolution and mechanism of marine productivity are important for understanding the global biogenic factor cycle and its roles in past, present and future climate change. Based on the analysis of biogenic silica (BSi) in core ADM-159 and core BoB-56 from the northeastern Indian Ocean, high-resolution curves of paleoproductivity evolution were obtained. The results show that the BSi contents in these two core sediments are less than 1.8%, mainly affected by the low supply of silica skeleton and the high dissolution and dilution of terrigenous materials. Distinct fluctuations in BSi contents could still be reflected, and their relative values were controlled by chemical weathering processes and terrigenous material supply. The power spectrum analysis of BSi content shows reliable periodicities of 5.86 kyr, 1.95 kyr, 1.35 kyr and 1.09 kyr, suggesting that millennial-scale BSi value might be affected by solar activity. Based on the BSi mass accumulation rates (MAR), lower paleoproductivity during the glacial period and higher level during the Holocene were revealed in our records, which matched well with the global climate changes. Temperatures controlled by low latitude insolation changes could influence the nutrient substance supply, further promote productivity variations at the glacial–interglacial scale. Some millennial events, such as the Heinrich stadial 1 (HS1) and Younger Dryas (YD) periods, showed relatively low paleoproductivity, while the Bølling/Allerød (B/A) period and the middle Holocene showed higher paleoproductivity. These millennial paleoproductivity fluctuations may be due to the changes of nutrient supply caused by Indian summer monsoon (ISM). In addition, the BSi MAR of core ADM-159 and core BoB-56 are well correlated with the isotopic compositions of Greenland ice core and Chinese speleothem, providing robust evidence for the link between northeastern Indian Ocean paleoproductivity and global climate change. • paleoproductivity variability since LGM was reconstructed by BSi in the northeastern Indian Ocean. • BSi content were controlled by supply of silica skeleton, dissolution and dilution of terrigenous materials. • Indian summer monsoon have been proved linked with tropic Indian Ocean paleoproductivity. [ABSTRACT FROM AUTHOR]

The heavy metal contents (Cr, Cu, Zn, Cd, Pb, Hg, and As) of 88 surface sediment samples from the western Sunda Shelf were analyzed to determine their spatial distribution patterns and contamination status. The results demonstrated that high enrichment regions of heavy metals were focused in the Kelantan, Pahang, and Ambat river estuaries, and deep water regions of the study area. These high enrichment regions were mainly controlled by riverine inputs and their hydrodynamic conditions. The enrichment factor (EF), geoaccumulation index (I geo), and potential ecological risk index (PERI) were used to assess heavy metal accumulation. The results indicated that the study area was not significantly contaminated overall at the time of the study; however, Cd, As, and Hg were at levels corresponding to moderate contamination at many stations located in the Pahang River estuary, Kelantan River estuary, and north-eastern region of the study area, primarily because of anthropogenic activities. • The heavy metal contents of surface sediment samples from the western Sunda Shelf were analyzed. • High heavy metal enrichment regions were mainly controlled by riverine inputs and hydrodynamic conditions. • The western Sunda Shelf was not significantly contaminated overall at the time of the study. [ABSTRACT FROM AUTHOR]