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To identify and quantify the sediment sources in the South Sea of Korea, a marginal sea of the northwestern Pacific, we analyzed a comprehensive aluminum–magnesium dataset comprising 121 surface sediment samples and two sediment cores. The findings demonstrate pronounced spatial variation in sediment sources, with Korean river sediments dominating in embayment bays and Chinese river sediments prevailing in the shelf area. In the coastal zone, Korean river sediments account for over 60–70%, but their proportion decreased to 10–20% in the shelf zone. This reveals that most of the sediments from Korean rivers are mainly confined to the coastal embayments, with limited transport to the shelf area. Notably, the central South Sea mud (CSSM) deposits are primarily govern by the sediment influx from Chinese rivers (CR), rather than the Seomjin River discharge. The prevalence of CR-sourced sediments in the shelf region is closely linked to the Tsushima Warm Current and Cheju Warm Current, transporting sediments from the East China Sea shelf northwards and the southwestern Korean coastal zone eastwards, respectively. This driving mechanism for the widespread deposition of CR sediments is further supported by an abrupt shift from KR to CR dominance in sediment sources around 8 kyr BP, coinciding with the establishment of the modern current systems in the northwestern Pacific marginal seas. Our study provides a new perspective on the source-to-sink pathways, particularly of Chinese river sediments, in the formation of the Korean coastal mud deposits. [ABSTRACT FROM AUTHOR]

As the second largest dust source on the globe, the tectonic and climatic evolution of continental Asia has an important impact on regional and global climate change. The West Pacific is the main sediment sink for eolian dust transported eastward from the Asian interior. Clay minerals, as the major fine-grained weathering products of continental rocks, can be readily transported by wind or currents over long distances and thus have been widely used in the reconstruction of paleoclimate and weathering history. However, the overall evolutionary tendency and response mechanism of clay mineral records over large spatial and long timescales across Asia remain unclear. Here, two continuous and high-resolution clay mineral records since 30 Ma were reconstructed from sediments at Deep Sea Drilling Program (DSDP) Sites 292 and 296 in the Philippine Sea. Clay minerals and Sr-Nd isotope compositions were used to constrain provenance and reconstruct the drying history of the dust source region since the Oligocene. The results show that the clay-sized detrital sediments in the Philippine Sea are a mixture of Asian eolian dust and volcanic materials from the West Pacific arcs. Based on the clay mineral compositions and eolian flux, we reveal that the Asian interior has been continuously drying since the late Oligocene and that stepwise enhanced aridification occurred at approximately 20, 14, 7, and 3 Ma. Compared with other regions of the world, the relative contents of illite and chlorite increased more dramatically in Asia during the late Cenozoic, and the inconsistency became more obvious at approximately 20 Ma. Since 3 Ma, illite and chlorite have increased consistently across the globe. Combined with the Asian tectonic and climatic history, we suggest that the increase in illite and chlorite from Asia between 20 and 3 Ma was mainly in response to the uplift of the Himalayan-Tibetan Plateau, whereas after 3 Ma, it was primarily controlled by global cooling driven by the expansion of the Arctic ice sheet. [ABSTRACT FROM AUTHOR]

At present, the seasonal melting and expansion of the Antarctic ice sheet affect the location and intensification of the westerlies, as well as the precipitation and continental weathering and erosion in southwest Australia. The Miocene was an important period when the Earth's climate state transitioned from a warmhouse to an icehouse and the East Antarctic Ice Sheet underwent large-scale melting and expansion. At that time, Australia was closer to the Antarctic region than it is now. This makes Australia an ideal target area for studying the coupling relationship among the atmosphere, hydrosphere, lithosphere, and cryosphere. Based on the comprehensive analysis of the siliciclastic mass accumulation rate, grain size, clay minerals, and elemental composition of the sediments at Site U1516 of the International Ocean Discovery Program Expedition 369, we reconstructed the Miocene climate evolution and the continental weathering and erosion history of southwest Australia on a tectonic time scale. Our indicators show that the climate was dry and that continental weathering and erosion were weak, with a small amount of terrestrial material transported to the ocean during the Early to Middle Miocene (22–12.7 Ma). However, as mentioned in previous studies of nearby sites, precipitation and river runoff increased prominently with enhanced continental weathering at 12.7–8 Ma, which was related to the northward migration or intensification of the westerlies, possibly due to increased sea ice in the Southern Ocean. In addition, we found that the evolution of the South Asian monsoon and the westerly belt were synchronized in the Miocene, which indicates that the South Asian monsoon system at that time may also have been affected by the high-latitude signals of the Southern Hemisphere. We speculate that the significant decrease in deep-sea temperature and the expansion of the surface sea temperature gradient in latitude and longitude until the permanent East Antarctic Ice Sheet formed (∼12.8 Ma) played an important role in the transmission of Antarctic signals to low latitudes. [ABSTRACT FROM AUTHOR]

Based on a δO chronology, rare earth elements (REE) and other typical elements in sediments from core MD06-3047 in the western Philippine Sea were analyzed to constrain the provenances of the sediments and investigate quantitative changes in the Asian eolian input to the study area over the last 700 ka. Among the competing processes that might affect REE compositions, sediment provenance is the most important one. Provenance analysis suggests that the study sediments have two provenance end-members; local volcanic sources are dominant, and eolian dust from the Asian continent has a smaller contribution. During glacial periods, eolian input to the western Philippine Sea was enhanced. In contrast, material supply from local volcanics increased during interglacial periods. Changes in eolian input to the study area were probably related to the strength of the East Asian winter monsoon (EAWM) as well as aridity in the Asian continent on an orbital time scale, and were partly influenced by local control factors on shorter time scales. Therefore, we propose that the present study expands the application of the REE-based method for quantitatively estimating the eolian component from the mid-latitude northern Pacific to the low-latitude western Pacific. Additionally, the study preliminarily confirms the influence of EAWM-transported eolian material on sedimentation in the western Philippine Sea since 700 ka. [ABSTRACT FROM AUTHOR]

To synthetically realize the character of major-element compositions as well as its significance for provenance and paleoenvironment recorded in core sediments of the West Philippine Sea over the last 700 ka, grain size and major elements of 221 bulk sediments, together with major-element compositions in the detrital phase of 16 typical samples, in core MD06-3047 collected from the Benham Rise were analyzed. Both discrimination plot and R-mode factor analysis indicate that vertical changes of major elements are mainly controlled by the sedimentation of nearby volcanic matter and the eolian dust input, whereas influences from marine biologic deposition and hydrothermal activity are minor. In particular, AlO and KO are representative of an eolian dust factor. The variation in the eolian dust factor score is characterized by the obviously glacial-interglacial periodicity and can be well compared with the paleotemperature record of the Antarctic ice core and the evolution of the East Asian winter monsoon (EAWM) recorded in the Chinese loess sequence, and then offers a new proxy for the evolution history of eolian dust input into the study area that is controlled by the EAWM intensity and aridity in the continental source regions of atmospheric dust. [ABSTRACT FROM AUTHOR]

Paleoenvironmental changes in the northern Okinawa trough covering the last 25 ka were synthetically reconstructed using REE and organic carbon indices of core CSH1. Variations of these parameters revealed three distinct intervals of major sediment provenance changes that can be related to sea-level fluctuation and Tsushima Warm Current evolution. Interval 1 (16-24.7 ka BP) is characterized by dominantly fluvial discharge from the Changjiang (Yangtze River) and Huanghe (Yellow River) as well as high primary productivity. In Interval 2 (7.3-16 ka BP), the Changjiang and Huanghe mouths regressed with sea-level rising. The newly formed Tsushima Warm Current could carry some sediment loads of Taiwan to the study core, especially during its late phase (7.3-8.2 ka BP). Modern oceanographic conditions were finally established since the beginning of Interval 3, leading to more terrigenous contribution from Taiwan, whereas low sea-surface productivity in the study area. [ABSTRACT FROM AUTHOR]

Rare earth elements (REEs) of 91 fine-grained bottom sediment samples from five major rivers in Korea (the Han, Keum, and Yeongsan) and China (the Changjiang and Huanghe) were studied to investigate their potential as source indicator for Yellow Sea shelf sediments, this being the first synthetic report on REE trends for bottom sediments of these rivers. The results show distinct differences in REE contents and their upper continental crust (UCC)-normalized patterns: compared to heavy rare earth elements (HREEs), light rare earth elements (LREEs) are highly enriched in Korean river sediments, in contrast to Chinese river sediments that have a characteristic positive Eu anomaly. This phenomenon is observed also in primary source rocks within the river catchments. This suggests that source rock composition is the primary control on the REE signatures of these river sediments, due largely to variations in the levels of chlorite and monazite, which are more abundant in Korean bottom river sediments. Systematic variations in ΣLREE/ΣHREE ratios, and in (La/Yb)–(Gd/Yb)UCC but also (La/Lu)–(La/Y)UCC and (La/Y)–(Gd/Lu)UCC relations have the greatest discriminatory power. These findings are consistent with, but considerably expand on the limited datasets available to date for suspended sediments. Evidently, the REE fingerprints of these river sediments can serve as a useful diagnostic tool for tracing the provenance of sediments in the Yellow Sea, and for reconstructing their dispersal patterns and the circulation system of the modern shelf, as well as the paleoenvironmental record of this and adjoining marginal seas. [ABSTRACT FROM AUTHOR]

Based upon analyses of grain-size, rare earth element (REE) compositions, elemental occurrence phases of REE, and U-series isotopic dating, the sediment characteristics and material sources of the study area were examined for the recently formed deep-sea clays in the eastern Philippine Sea. The analytical results are summarized as follows. (1) Low accumulation rate, poor sorting and roundness, and high contents of grains coarser than fine silt indicate relatively low sediment input, with localized material source without long distance transport. (2) The REE Contents are relatively high. Shale-normalized patterns of REE indicate weak enrichment in heavy REE (HREE), Ce-passive anomaly, and Eu-positive anomaly. (3) Elemental occurrence phases of REE between the sediments with and without crust are similar. REE mainly concentrate in residual phase and then in ferromanganese oxide phase. The light REE (LREE) enrichment, Ce-positive anomaly, and Eu-positive anomaly occur in residual phase. Ferromanganese oxide phase shows the characteristics of relatively high HREE content and Ce-passive anomaly. (4) There are differences in each above mentioned aspect between the sediments with and without ferromanganese crust. (5) Synthesizing the above characteristics and source discriminant analysis, the study sediments are deduced to mainly result from the alteration of local and nearby volcanic materials. Continental materials transported by wind and/or river (ocean) flows also have minor contributions. [ABSTRACT FROM AUTHOR]

From systemic research of microstructure, geochemistry, uranium-series and 10Be isotope dating on a new-type deepwater ferromanganese crust from the East Philippine Sea, the paleoenvironment evolution of the target area since the terminal Late Miocene was recovered. The vertical section changes of microstructure and chemical composition are consistent in the studied crust, which indicate three major accretion periods and corresponding paleoenvironment evolution of the crust. The bottom crust zone was formed in the terminal Late Miocene (5.6 Ma) with loose microstructure, high detritus content and high growth rate. Reductions of mineral element content, accretion rate and positive Ce-anomaly degree at 4.6 Ma indicate temporal warming, which went against the crust accretion and finally formed an accretion gap in the terminal Middle Pliocene (2.8–2.7 Ma). The more active Antarctic bottom seawaters in the Late Pliocene (2.7 Ma) facilitated the fast transfer to the top pure crust zone. Hereafter, with the further apart of volcanic source and the keeping increase of eolian material (1.0 Ma), although surrounding conditions were still favorable, mineral element content still shows an obvious reducing trend. It thereby offers new carrier and data for the unclear paleoceanographic research of the target area since the terminal Late Miocene. [ABSTRACT FROM AUTHOR]

AMS14C dating and grain-size analysis for Core DD2, located at the north of the Yangtze River-derived mud off the Zhejiang-Fujian coasts in the inner shelf of the East China Sea, provide us a high-resolution grain-size distribution curve varying with depth and time. Data in the upper mud layer of Core DD2 indicate that there are at least 9 abrupt grain-size increasing in recent 2000 years, with each corresponding very well with the low-temperature events in Chinese history, which might result from the periodical strengthening of the East Asian Winter Monsoon (EAWM), including the first-revealed maximum temperature lowering event at around 990 a BP. At the same time, the finer grain size section in Core DD2 agrees well with the Sui-Tang Warming Period (600–1000 a AD) defined previously by Zhu Kezhen, during which the climate had a warm, cold and warm fluctuation, with a dominated cooling period of 750–850 a AD. The Little Ice Age (LIA) can also be identified in the core. It starts around 1450 a AD and was followed by a subsequent cooling events at 1510, 1670 and 1840 a AD. Timing of these cold events revealed here still needs to be further verified owing to some current uncertainty of dating we used in this study. [ABSTRACT FROM AUTHOR]