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As the largest river of China, the Yangtze River transports large amounts of sediments to the adjacent oceans. Provenance of these ancient marine sediments can only be deciphered when the source-to-sink process of modern sediments in the Yangtze River is fully understood. Many methods have been used to study the provenance of river sediment and an environmental magnetic method is applied in this study because of its fast, nondestructive advantages. Magnetic properties of suspended particulate matter (SPM) along the Yangtze River were measured to provide a holistic understanding about magnetic properties of sediments in this river and its controlling factors. The results indicate that the dominant magnetic mineral in SPM is magnetite, with a small contribution of hematite and goethite. Significant spatial variation was observed in most of the magnetic parameters, which primarily reflects the distribution of major geologic units along the drainage area of the river. Anthropogenic influences are also recorded in the magnetic parameters. The Three Gorges Dam results in a dramatic decrease of magnetic minerals in the downstream reaches, since its construction in 2003. In addition, small variations in magnetic properties of SPM are found along water depth, together with a clear seasonal shift at Datong station. This seasonal variation of magnetic properties of SPM is driven by variability in both hydrology and source contributions. This complicates the use of magnetic parameters for provenance studies. Magnetic properties of sediments in rivers are capable of tracing provenance areas, but caution must be taken into account.

Asian dust has a significant impact on the natural environment. Its variability on multiple timescales modulates the ocean biogeochemistry and climate. We demonstrate that temporal changes in the deposition flux of Aeolian dust recorded in sediments from Lake Suigetsu, central Japan, during the last century exhibit a continuous decreasing trend and a decadal-scale decrease in 1952–1974. The former decreasing trend can be explained by a decrease in the dust storm frequency at source regions due to the warming of Mongolia in the twentieth century, suggesting future decrease of Asian dust transport with further warming in Mongolia. Decadal-scale decrease of Aeolian dust is explained by weaker westerlies in lower latitudes in central Japan, reflecting a weaker Aleutian Low during the corresponding period. Decadal-scale westerly change probably causes north–south shifts of the dominant dust transport path, which affects subarctic northern Pacific Ocean biogeochemistry by changing the micronutrient iron supply.

Atsushi Yoshida, Nobuhiro Moteki, Sho Ohata, Tatsuhiro Mori, Ryuji Tada, Pavla Dagsson-Waldhauserov a, and Yutaka Kondo Department of Earth and Planetary Science, The University of Tokyo, Tokyo, Japan; Faculty of Environmental Sciences, Agricultural University of Iceland, Hvanneyri, Iceland; Faculty of Physical Sciences and Faculty of Earth Sciences, University of Iceland, Reykjav ik, Iceland; Faculty of Environmental Sciences, Czech University of Life Sciences Prague, Prague, Czech Republic; Meteorology and Glaciology Group, National Institute of Polar Research, Tokyo, Japan

Astronomical solutions for planetary orbits beyond several tens of million years (Myr) ago have large uncertainties due to the chaotic nature of the Solar System, mainly Myr-scale cycles related with the Earth-Mars secular resonance. Our only accessible archive for unraveling the Earth's orbital variations in the geologic past are sedimentological records, yet their reliability and uncertainties are still debated. Here, we describe Myr-scale orbital signals of early Mesozoic monsoon records from two different sedimentary settings (lake level records of the equatorial Pangea and biogenic silica burial flux of deep-sea Panthalassa), along with a marine carbon isotope compilation. Although most of the dominant multi-Myr cycles are not exactly of the same frequency, 1.8 Myr cycles during ∼216–210 Ma are detected from the two mutually-independent sedimentary settings, and differ from available astronomical solutions. This finding provides not only convincing evidence for the chaotic nature of the Solar System in the geological past, but also additional constraints on astronomical models. On the other hand, besides the orbital cycles, tectonic forcing and consequent climatic perturbations could also have affected the proxies on multi-Myr timescales during episodes of large igneous province emplacement, such as Siberian trap volcanism (252–245 Ma), Wrangellia (233–225 Ma), Central Atlantic Magmatic Province (202–200 Ma), and Karoo-Ferrar volcanism (184–180 Ma). If we can distinguish orbital signals from other effects, such as tectonic and volcanic processes, the multi-Myr cycles in geologic records have the potential to reconstruct the chaotic evolution of the Solar System.

Continuous and high-resolution records of the content, mass accumulation rate (MAR) and δ 13 C values of black carbon obtained from Integrated Ocean Drilling Program (IODP) Site U1430 in the southwestern Japan Sea have been established and combined with previous results obtained from Central Asia. The main objective of this work is to reconstruct the historical changes in vegetation types (C3–C4), and to constrain the driving force of C4 plant expansion over the last 13 Ma. The stable carbon isotope value of black carbon ( δ 13 CBC) shows a major shift since the Miocene–Pliocene boundary (∼5.3 Ma), suggesting significant expansion of C4 plants in broad areas of Central Asia, including the inland basins of northwestern China and the Loess Plateau. However, a decline in the content and MAR of black carbon reveals the absence of any link between fire and C4 plant expansion in Central Asia, due to the dramatic decrease in biomass under a drying regime. On a global scale, asynchronous expansion of C4 plants suggests that regional hydroclimatic change, rather than decline in CO2 concentration, was the most important factor to influence C4 expansion. We propose that the increased seasonality and the enhanced long-term aridity driven by the concurrent decline in winter westerly vapor, and increase in East Asian summer monsoon precipitation, were the main driving forces of C4 plant expansion in broad areas of Central Asia. Variations in winter westerly moisture have played a significant role in changes of regional climate and vegetation in Central Asia since the late Miocene.

Understanding the behaviour of the global climate system during extremely warm periods is one of the major themes of paleoclimatology. Proxy data demonstrate that the equator-to-pole temperature gradient was much lower during the mid-Cretaceous "supergreenhouse" period than at present, implying larger meridional heat transport by atmospheric and/or oceanic circulation. However, reconstructions of atmospheric circulation during the Cretaceous have been hampered by a lack of appropriate data sets based on reliable proxies. Desert distribution directly reflects the position of the subtropical high-pressure belt, and the prevailing surface-wind pattern preserved in desert deposits reveals the exact position of its divergence axis, which marks the poleward margin of the Hadley circulation. We reconstructed temporal changes in the latitude of the subtropical high-pressure belt and its divergence axis during the Cretaceous based on spatio-temporal changes in the latitudinal distribution of deserts and prevailing surface-wind patterns in the Asian interior. We found a poleward shift in the subtropical high-pressure belt during the early and late Cretaceous, suggesting a poleward expansion of the Hadley circulation. In contrast, an equatorward shift of the belt was found during the mid-Cretaceous "supergreenhouse" period, suggesting drastic shrinking of the Hadley circulation. These results, in conjunction with recent observations, suggest the existence of a threshold in atmospheric CO2 level and/or global temperature, beyond which the Hadley circulation shrinks drastically.

International audience; The Japan Sea is directly influenced by the Asian monsoon, a system that transports moisture and heat across southeast Asia during the boreal summer, and is a major driver of the Earth's ocean-atmospheric circulation. Foraminiferal and facies analyses of a 460-kyr record from Integrated Ocean Drilling Program Expedition 346 Site U1427 in the Japan Sea reveal a record of nutrient flux and oxygenation that varied due to sea level and East Asian monsoon intensity. The East Asian summer monsoon (EASM) was most intense during marine isotope stage (MIS) 5e, MIS 7e, MIS 9e, and MIS 11c when the Tsushima Warm Current flowed into an unrestricted well-mixed normal salinity Japan Sea, whereas East Asian winter monsoon (EAWM) conditions dominated MIS 2, MIS 4, MIS 6, and MIS 8 when sea level minima restricted the Japan Sea resulting in low-salinity and oxygen conditions in the absence of Tsushima flow. Reduced oxygen stratified, low-salinity, and higher productivity oceanic conditions characterize Terminations TV, TIII, TII, and TI when East China Sea coastal waters breached the Tsushima Strait. Chinese loess, cave, and Lake Biwa (Japan) and U1427 proxy records suggest EASM intensification during low to high insolation transitions, whereas the strongest EAWM prevailed during lowest insolation periods or high to low insolation transitions. Ice sheet/CO 2 forcing leads to the strongest EAWM events in glacials and enhanced EASM in interglacials. Mismatches between proxy patterns suggest that latitudinal and land/sea thermal contrasts played a role in East Asian monsoon variability, suggesting that a complex interplay between ice sheet dynamics, insolation, and thermal gradients controls monsoonal intensity.

The evolution of the provenance of aeolian deposits on the Chinese Loess Plateau (CLP) is closely linked to changes in source aridity and dust transport dynamics. Although previous studies have revealed that the provenance of Chinese aeolian deposits may have fluctuated on tectonic timescales, the exact timing and cause of the provenance shifts remain poorly constrained due to limitations of the isotopic and mineralogical tracers used. Here we report the results of electron spin resonance (ESR) signal intensity and crystallinity index (CI) of fine-grained (

High-resolution multi-proxy records, including clay minerals and Sr-Nd-Pb isotopes of the clay-sized silicate fraction of sediments from IODP Site U1429 in the northern Okinawa Trough, provide reliable evidence for distinct control mechanism on fine-grained sediments input from the Yellow River and the southern Japanese Islands to the northern Okinawa Trough since 34 ka BP. Provenance analysis indicates that the sediments were mainly derived from the Yellow River and the island of Kyushu. Since the last glacial, clay-sized sediments transported from the Yellow River to the study site were strongly influenced by sea-level fluctuation. During low sea-level stage (∼34‒14 ka BP), the paleo-Yellow River mouth was positioned closer to the northern Okinawa Trough, favoring large fluvial discharge or even direct input of detrital sediments, which resulted about four times more flux of clay-sized sediments supply to the study area as during the relatively high sea-level stage (∼14‒0 ka BP). The input of Kyushu-derived clay-sized sediments to the study site was mainly controlled by the Kuroshio Current and Tsushima Warm Current intensity, with increased input in phase with weakened Kuroshio Current/Tsushima Warm Current. Our study suggests that the Kuroshio Current was very likely flowed into the Okinawa Trough and thus influenced the fine-grained sediment transport in the area throughout the last glacial and deglacial. During ∼34‒11 ka BP, the Kyushu clay-sized sediment input was mainly controlled by the Kuroshio Current. Since ∼11 ka BP, the occurrence of Tsushima Warm Current became important in influencing the Kyushu fine-grained sediment input to the northern Okinawa Trough.

Variation of dissolved 87 Sr/ 86 Sr in the Yangtze River is poorly documented compared to other Tibetan-sourced rivers. Here, we trace the Sr isotopic composition in space and time across the Yangtze River basin using a systematic sampling strategy. The 87 Sr/ 86 Sr values of samples collected at different depths within the water column at three gauge stations located in the upper, middle and lower reaches of the river are very similar, indicating a well-mixed water body at a given location. Data from basin wide-samples shows low 87 Sr/ 86 Sr values in the upper reaches while higher 87 Sr/ 86 Sr values in the middle-lower reaches which mainly reflect the controls of source rocks. A time series record at the lowermost reaches of the river indicates a temporal variation of 87 Sr/ 86 Sr values from 0.7101 to 0.7109, with a discharge weighted value of 0.7106. We suggest that temporal variations of the isotopic composition result from changes in the relative contributions from different terrains associated with spatial variability of rainfall within the basin. A mixing model based on Sr values deduced from basin-wide sampling from different seasons yields similar temporal variations of Sr isotopic composition compared to experimental data. Calculation of Sr fluxes indicates that the upper reaches contribute 3 times as much as the middle and lower reaches to total Sr flux. The annual Sr flux of the Yangtze River to the East China Sea is estimated to be 1.9 × 10 9 mol · a − 1 , which is one magnitude higher than that of the Brahmaputra and Ganges.

The response of the monsoon climate on the inner shelf of the East China Sea (ECS) to abrupt climate changes events within the monsoonal Yangtze River drainage is contentious. Repositioning of the monsoon front is thought to have been responsible for the changes in hydroclimate over the Yangtze River drainage, which has exerted great impact on the sedimentation of the inner shelf of the ECS during the Holocene. Here, we present high-resolution analyses of grain size and provenance of the sediments from core MD06-3040 recovered from the inner shelf of the ECS during MD155-Marco Polo II-IMAGES XIV cruise. Significant variability occurred in the core MD06-3040 with notable decrease in East Asian Summer Monsoon precipitation (presumably drought events) at 6000 BP, 5300 BP, 4500 BP, 3700-3300 BP, 2200 BP, 1400-1300 BP, and 800-600 BP, which coincide with the delta O-18(w) record in the northern ECS and stalagmite Delta delta O-18(sp) records from southern China. Similar patterns of these temporal variations suggest that the Yangtze River discharge associated with EASM precipitation has been a dominant control on the sedimentation on the inner shelf of ECS. (c) 2014 Elsevier Ltd and INQUA. All rights reserved.

The astronomical time scale (ATS) has provided high-resolution geochronology. However, the early Mesozoic ATS is still under construction partly due to the lack of continuous pelagic sequences of the early Mesozoic. Here we present ca. ∼ 70 Myr long ATS constructed from the early Mesozoic deep-sea bedded chert sequence exposed in the Inuyama area, central Japan. The sedimentary rhythms of bedded chert display a full range of climatic precession related cycles; ∼20-kyr cycle as a chert–shale couplet and ∼100-, 405-, 2000- to 4000-, and 10,000-kyr cycles as chert bed thickness variation. The newly established ATS (Inuyama-ATS) is tuned by 405-kyr eccentricity cycle and is anchored at the end-Triassic radiolarian extinction level as 201.4 ± 0.2 Ma . This Inuyama-ATS gives ages consistent with the radiometric ages projected to the Inuyama deep-sea sequence using biostratigraphy and carbon isotope stratigraphy. The Inuyama-ATS provides the age constraints for the Triassic and Jurassic stage boundaries, which support the “Long-Norian” option of Muttoni et al. (2004) . Because the deep-sea bedded chert sequence covers a long time interval before the Cretaceous, the ATS for the bedded chert will serve as a template for the astrochronology of Mesozoic and older ages.

Two piston cores (PC-05 and PC-08) were collected on the Yamato Rise in the East Sea/Japan Sea during the KR07-12 cruise. Both cores showed typical alternations of light (high L*) and dark (low L*) layers, which are characteristic in the hemi-pelagic sediment deposited in the deep part of the East Sea/Japan Sea. A composite core was achieved with the successful replacement of almost half of the upper part of core PC-05 by the entirety of core PC-08 based on the co-equivalence of L* values and the dark layers, because an interval (170 cm–410 cm) of core PC-05 was considerably disturbed due to fluidization during the core execution. Chronostratigraphy of the composite core was constructed by the direct comparison of L* values to the well-dated core MD01-2407 that was obtained in the Oki Ridge. The lower-bottom of the composite core extended to Marine Isotope Stage (MIS) 14, based on the age estimate by LR04 stacks. Downcore opal variation of the composite core exhibited the distinct orbital-scale cyclic changes; high during the interglacial and low during the glacial periods. However, downcore CaCO3 variation showed no corresponding orbital-scale cyclic change between glacial and interglacial periods. Some intervals of both periods were high in CaCO3 content. Frequent and large fluctuations in CaCO3 content seemed to be more related to the presence of dark layers containing thin lamination (TL) within the glacial and interglacial intervals. It is worthy to note that MIS 2 and MIS 12 are characterized by distinctly high CaCO3 content, showing up to 18% and 73%, respectively, among the glacial periods. Furthermore, in terms of lithology, MIS 2 was characterized by a thick dark layer (low L* values) with TL, whereas MIS 12 preserved the distinctly light layer (high L* values) with parallel laminations. Another remarkable dissimilarity between MIS 2 and MIS 12 was the nature of their CaCO3 constituent; the CaCO3 constituent of MIS 2 consisted of mostly planktonic foraminifera, whereas that of MIS 12 was mostly dump of coccolithophorids, regardless the presence of planktonic foraminifera. The distinctness of the CaCO3 constituents between MIS 2 and MIS 12 indicates that the preservation of CaCO3 contents was different temporarily during the glacial periods in the East Sea/Japan Sea. Enhanced CaCO3 preservation in MIS 2 is attributed primarily to less dissolution during the sinking through the water column or at the seafloor, but increased CaCO3 preservation in MIS 12 is mainly due to the high primary production in the surface water. With respect to the different function of the biological pump which controls CO2 cycles, the East Sea/Japan Sea clearly experienced carbonate-ocean-like state during MIS 12, despite normally silica-ocean-like state.

Previous studies find decadal climate variability possibly related to solar activity, although the details regarding the feedback with the ocean environment and ecosystem remain unknown. Here, we explore the feedback system of solar irradiance change during the Bolling-Allerod period, based on laminated sediments in the northern Bering Sea. During this period, well-ventilated water was restricted to the upper intermediate layer, and oxygen-poor lower intermediate water preserved the laminated sediment. An 11-year cycle of diatom and radiolarian flux peaks was identified from the laminated interval. Increased fresh meltwater input and early sea-ice retreat in spring under the solar irradiance maximum follow the positive phase of Arctic Oscillation which impacted the primary production and volume of upper intermediate water production in the following winter. Strength of this 11 year solar irradiance effect might be further regulated by the pressure patterns of Pacific decadal oscillation and/or El Nino-Southern Oscillation variability.

Changes in the intensity of the influx of the Tsushima Warm Current (TWC) in the south-central part of the Japan Sea (JS), or East Sea in Korean, were reconstructed for the last 460 kyr at IODP Site U1427 using the composition and abundance of the coccolithophore assemblage. In addition, the recent distribution of coccolithophore taxa in the JS and the East China Sea was assessed using electron microscopy. Coccolithophore assemblages, dominated by Emiliania huxleyi and Gephyrocapsa species, and coccolith abundance reveal a strong relationship between sea level and ocean variability over the last five glacial/interglacial cycles, in good agreement with planktic foraminiferal data. Three different circulation modes based on calcareous nannofossil and foraminifera TWC indicators were proposed for the JS. Coccolith production was low and TWC indicators (i.e., Gephyrocapsa oceanica, Calcidiscus leptoporus s.l., and Helicosphaera carteri) absent due to the isolation of the JS during glacials in response to global sea level falls (Mode 1). In contrast, coccolith abundance and TWC indicators reach a maximum due to the most intense TWC flow through the Tsushima Strait during interglacials (Mode 3). Intermediate conditions (Mode 2) are characterized by moderate/high coccolith numbers, presence of TWC coccolith indicators, and rare TWC planktic foraminifera indicators. This mode resulted in intermittent variations in the contribution of the TWC and East China Sea coastal water due to relatively low sea level stands (ca. −90 m to −20 m). Coccoliths dominated the carbonate sequence prior to MIS 8 and were major contributors to the total carbonate of the sediment at Site U1427, suggesting high coccolithophore productivity and a bloom-type environment during MIS 11 and 9. These changes in the carbonate chemistry caused by glacio-eustacy in the JS at the northwest margin of the Pacific Ocean should be considered in future paleoceanographic and paleoclimate models.

[1] The causes of spatial and temporal changes in East Asian summer monsoon (EASM) precipitation on millennial to multimillennial time scales during the Holocene have not yet been resolved. Here, we examine the relationship between spatial variations in EASM precipitation and the westerly jet (WJ) path over East Asia during the Holocene using the provenance of eolian dust in Japan Sea sediments, which we interpret to reflect changes of the WJ path over East Asia and/or surface conditions of desert areas. The contribution of dust from the Mongolian Gobi Desert relative to that from the Taklimakan Desert shows millennial-scale to multimillennial-scale minima at 11.5–10, 7–5, and 3.5–1.5 kyr B.P., which we attribute to earlier seasonal northward progression of the WJ. These dates correlate with precipitation maxima along the present northwestern EASM margin and minima in eastern Northeast China and the Yangtze River Basin, suggesting that the WJ shifted northward earlier in the year, allowing earlier northward migration of the EASM rainband and generating abundant precipitation in the northwestern EASM margin. Therefore, during the Holocene, changes of the WJ path probably contributed to the millennial-scale to multimillennial-scale EASM precipitation changes and its northwest-southeast contrast within China. Our findings suggest that WJ path changes are critical to understand the dynamics of EASM in the past, present, and future.

The temporal change in the number of oxygen vacancies in quartz was investigated by ob-serving the E1’ center in the atmospheric depositions collected at two cities in Japan in the recent past. The depositions collected at Fukuoka in March show the ESR intensities being correlated with the sum of the number of the days, in the month, on which Kosa was observed while no such correlation was found in the deposition those collected at Akita but a trend of decrease with time. The present results suggest that the number of oxygen vacancies in quartz might be useful to estimate quantitatively the contribution of the dust originated from China to the atmospheric deposition in Japan.

[1] Electron spin resonance (ESR) signal intensity and crystallinity index (CI) of fine- ( 16 µm) quartz were measured in surface samples from the Taklimakan desert in western China, the Badain Juran, Tengger and Mu Us deserts in northern China, and the Gobi desert in southern Mongolia to evaluate whether these geophysical parameters can serve as reliable provenance tracers of Asian dust. The results indicate that spatial variability of both ESR signal intensity and CI is evident within the Taklimakan deserts and the Mongolian Gobi, but less significant in the three deserts of northern China. Coarse-grained quartz from the Mongolian Gobi and northern China deserts can be differentiated from the Taklimakan desert using the ESR signal intensity. Fine-grained quartz originating from three major Asian dust sources, i.e., the Gobi-sandy deserts in western China, northern China and southern Mongolia, can be distinguished effectively using the combination of ESR and CI signals. Our results suggest that ESR signal intensity and CI can discriminate the sources of fine-grained quartz better than coarse-grained quartz, providing an effective approach to trace the provenance of fine-grained dust deposition on the land and in the ocean.

Article history: The Paleoproterozoic (2.5-2.0 Ga) is one of the most important periods in Earth's history, and was characterized by a rise in atmospheric oxygen levels and repeated (at least three) severe glaciations (the Huronian glaciations). In this study, we investigate redox conditions in the atmosphere and in shallow- marine environments immediately after the first Huronian glaciation based on the isotopic composition of Os, and the abundance of redox-sensitive elements (Os, Re, and Mo) in sedimentary rocks from the Huronian Supergroup, Canada. We found no significant authigenic enrichment of Os in the sedimentary rocks deposited during the first Huronian deglaciation. The initial isotopic composition of Os in the sediments was close to that of chondrite at the time of deposition ( 187 Os/

In the densely populated region of East Asia, it is important to know the mechanism, scale, and frequency of heavy precipitation brought about during the monsoons and typhoons. However, observational data, which cover only several decades, are insufficient to examine the long-term trend of extreme precipitation and its background mechanism. In humid areas, the transport flux of a suspended detrital material through a river system is known to have an empirical power relationship with precipitation. Thus, the sedimentation flux of a fine detrital material could potentially be used as a proxy for reconstructing past heavy precipitation events. To test the idea that the sedimentation flux of detrital materials records past heavy precipitation events (e.g., typhoons), we focused on the detrital flux estimated from the annually laminated sediment of Lake Suigetsu, central Japan, which is capable of accurately correlating the age of detrital flux with the precipitation record. We first established a precise age model (error within ±1 year in average) beginning in 1920 A.D. on the basis of varve counting fine-tuned by correlation between event layers with historical floods. The flux of the detrital material (g/cm2/year) was estimated on the basis of Al2O3 content (wt%), dry bulk density (g/cm3), and sedimentation rate (cm/year) calculated from the age model. The detrital flux of background sedimentation showed a weak positive correlation with annual and monthly (June and September) precipitation excluding heavy precipitation that exceeded 100 mm/day. Furthermore, the thickness of instantaneous event layers, which corresponds to several maxima of detrital flux and is correlated with floods that occurred mainly during typhoons, showed a positive relationship with the total amount of precipitation that caused a flood event. This result suggests that the detrital flux maxima (deposition of event layers) record past extreme precipitation events that were likely associated with typhoons that hit the middle part of Honshu Island. Based on this result, the record of typhoon-caused flood events can go back to older period (e.g., last glacial period) on the basis of the occurrence, and thickness, or mass flux of event layers using long sediment cores from Lake Suigetsu.

Uplift of the Himalaya and Tibetan Plateau (HTP) and its linkage with the evolution of the Asian monsoon has been regarded as a typical example of a tectonic–climate linkage. Although this linkage remains unproven because of insufficient data, our understanding has greatly advanced in the past decade. It is thus timely to summarize our knowledge of the uplift history of the HTP, the results of relevant climate simulations, and spatiotemporal changes in the Indian and East Asian monsoons since the late Eocene. Three major pulses of the HTP uplift have become evident: (1) uplift of the southern and central Tibetan Plateau (TP) at ca. 40–35 Ma, (2) uplift of the northern TP at ca. 25–20 Ma, and (3) uplift of the northeastern to eastern TP at ca. 15–10 Ma. Modeling predictions suggest that (i) uplift of the southern and central TP should have intensified the Indian summer monsoon (ISM) and the Somali Jet at 40–35 Ma; (ii) uplift of the northern TP should have intensified the East Asian summer monsoon (EASM) and East Asian winter monsoon (EAWM), as well as the desertification of inland Asia at 25–20 Ma; and (iii) uplift of the northeastern and eastern TP should have further intensified the EASM and EAWM at 15–10 Ma. We tested these predictions by comparing them with paleoclimate data for the time intervals of interest. There are insufficient paleoclimate data to test whether the ISM and Somali Jet intensified with the uplift of the southern and central TP at 40–35 Ma, but it is possible that such uplift enhanced erosion and weathering that drew down atmospheric CO2 and resulted in global cooling. There is good evidence that the EASM and EAWM intensified, and desertification started in inland Asia at 25–20 Ma in association with the uplift of the northern TP. The impact of the uplift of the northeastern and eastern TP on the Asian monsoon at 15–10 Ma is difficult to evaluate because that interval was also a time of global cooling and Antarctic glaciation that might also have influenced the intensity of the Asian monsoon.

We investigated the spatial distribution of glycerol dialkyl glycerol tetraethers (GDGTs), alkenones, and polyunsaturated fatty acids in particulate organic matter collected at four sites along a depth transect from the continental shelf to the Okinawa Trough in the East China Sea during the spring bloom in 2008. The maximum alkenone concentration appeared in the top 25 m at all sites and the $$ U_{37}^{{{\text{K}}'}} $$ values were consistent with in situ water temperatures in the depth interval, suggesting that the alkenones were produced mainly in surface water. At the slope and shelf sites, GDGTs in the water column showed a concentration maximum at 74–99 m depth, and the $$ {\text{TEX}}_{86}^{\text{H}} $$ agreed with in situ water temperatures, suggesting the in situ production of GDGTs in the depth interval. The low-salinity surface water above 20 m depth was characterized by low GDGT concentrations and low $$ {\text{TEX}}_{86}^{\text{L}} $$ -based temperatures, suggesting either the production of GDGTs in winter season or the lateral advection of GDGTs by an eastward current. At the slope and Okinawa Trough sites, TEX86-based temperatures were nearly constant in the water column deeper than 300 m and corresponded to temperatures at the surface and near-surface waters rather than in situ temperatures. This observation is consistent with a hypothesis that Thaumarchaeota cells produced in surface waters are delivered to deeper water and also indicates that the residence time of suspended GDGTs in the deep-water column is large enough to mix the GDGTs produced in different seasons.

The East China Sea (ECS) responds to changes in the strength of the Kuroshio and East Asian monsoon activity. Multidecadal resolution records of the palaeotemperature indices and from core KY07-04 PC-1 show that the hydrology of the ECS responded to variability in the East Asian winter monsoon. Unlike Mg/Ca-derived sea surface temperatures, which show neither warming nor cooling trends during the Holocene, the record showed a general warming trend at a rate of 0.2°C ka−1. This warming was attributable to shrinkage of the Yellow Sea Central Cold Water and/or weaker winter cooling of the surface water. The record indicated a centennial-scale variability with an ∼1°C amplitude superimposed on the warming trend that reflected changes in the East Asian winter monsoon and/or the Kuroshio. Temperature minima appeared at ca. 3.0, 4.7, 6.2, 7.9 and 9.0 ka, and spectral analysis of the last 7 ka revealed significant peaks with periodicities of approximately 210, 250, and 440 years that were close to those observed in solar radiation. The reconstructed winter monsoon variability is consistent with Chinese documentary records for the last two millennia. Copyright © 2012 John Wiley & Sons, Ltd.

Dating Carbon Radiocarbon dating is the best way to determine the age of samples that contain carbon and that are younger than ∼50,000 years, the limit of precision for the method. There are several factors that complicate such age determinations, however, some of the most important of which include variability of the 14 C production in the atmosphere (which affects organic samples whose radiocarbon inventories are derived from atmospheric CO 2 ), surface ocean reservoir effects (which affect marine samples that acquire their radiocarbon signatures from seawater), and variable dead carbon fraction effects (which affect speleothems that derive their carbon from groundwaters). Bronk Ramsey et al. (p. 370 ; see the Perspective by Reimer ) avoid the need to make such assumptions, reporting the 14 C results of sediments from Lake Suigetsu, Japan. Analysis of terrestrial plant macrofossils in annually layered datable sediments yielded a direct record of atmospheric radiocarbon for the entire measurable interval up to 52.8 thousand years ago.

After the severest mass extinction event in the Phanerozoic, biotic recovery from the extinction at the Permian–Triassic boundary required approximately 5 my, which covers the entire Early Triassic. It is important to obtain information on the superocean Panthalassa, which occupied most of the world ocean, to explore paleoenvironmental changes during the Early Triassic at the global scale. In order to establish the continuous lithostratigraphy of pelagic sediments in Panthalassa during the Early Triassic, high-resolution reconstruction of the Lower Triassic pelagic sequence in Japan was conducted for the first time based on detailed field mapping and lithostratigraphic correlation in the Inuyama area, central Japan. The reconstructed Early Triassic sequence is approximately 9.5 m thick, consists of five rock types, and is divided into eight lithological units. For the reconstructed continuous sequence, measurement of carbon isotopic composition of sedimentary organic matter (δ13Corg) was carried out. Stratigraphic variation of the δ13Corg value shows large-amplitude fluctuations between −34.4 and −21.0‰ throughout the sequence. In order to establish a higher resolution age model for the reconstructed Lower Triassic pelagic sequence, we correlated δ13Corg records in the Inuyama area with high-resolution isotopic profiles of carbonate carbon (δ13Ccarb) from shallow-marine carbonate sequences in southern China based on the similarity in general variation patterns with age constraints by radiolarian and conodont biostratigraphy. The result provides a high-resolution time scale for the pelagic sequence of Panthalassa during the Smithian and Spathian. The age model suggests a drastic increase in sedimentation rate during the late Smithian, which should have been caused by the increase in terrigenous input to this site.

Bering Sea sediments contain detrital materials from the Yukon River. These materials may contain records of past climate changes in the Arctic area, such as the melting of glaciers around the drainage basin of the Yukon River, which help to understand hydrological cycle in this area. In the Bering Sea, however, the spatial extent and pattern of the detrital materials supplied from the Yukon River is not yet fully understood. Here we developed a method to identify clay- to sand-sized detrital materials derived from the Yukon River based on electron spin resonance (ESR) intensity of the E 1 ' center and the crystallinity of quartz. We then estimated the spatial pattern of quartz contributed by the Yukon River on the Bering Sea shelf by applying the method to core-top samples from the continental shelf and slope of the eastern Bering Sea. The results showed a large contribution of sand-sized quartz from the Yukon River to wide areas of the continental shelf and slope, whereas contributions of clay- to silt-sized quartz from the Yukon River were small, except on the northeastern shelf. These spatial distribution patterns suggest that sand-sized quartz was repeatedly reworked and transported by processes such as storm surges to the outer continental shelf, whereas the clay- to silt-sized quartz on the northeastern shelf was supplied, as suspended materials, directly from the Yukon River.

A high-resolution record of the radiolarian assemblage from 60 to 10 ka was investigated using a piston core (PC-23A) obtained from the northern slope of the Bering Sea. Faunal changes based on the 29 major radiolarian taxa demonstrated that the surface and deep water conditions in the Bering Sea were related to the orbital and millennial-scale climatic variations known as glacial–interglacial and Dansgaard–Oeschger (D–O) cycles, respectively. During interstadial periods of the D–O cycles, the assemblage was characterized by increases in the high-latitude coastal species Rhizoplegma boreale and the upper-intermediate water species Cycladophora davisiana, while the sea-ice related species Actinomma boreale and A. leptodermum and many deep-water species such as Dictyophimus crisiae and D. hirundo tended to be reduced. This trend was more apparent in two laminated intervals at 15–13.5 and 11.5–11 ka, which were correlated with well-known ice-sheet collapse events that occurred during the last deglaciation: melt-water pulse (MWP)-1A and MWP-1B, respectively. The radiolarian faunal composition in these periods suggests that oceanic conditions were different from today: (1) surface water was affected by increased melt-water discharge from continental ice-sheet, occurring at the same time as an abrupt increase in atmospheric temperature, (2) upper-intermediate water (ca. 200–500 m) was well-ventilated and organic-rich, and (3) lower-intermediate water (ca. 500–1000 m) was oxygen-poor. Conversely, the sea-ice season might have been longer during stadial periods of the D–O cycles and the last glacial maximum (LGM) compared to the interstadial periods and the earliest Holocene. In these colder periods, deep-water species were very abundant, and this corresponded to increases in the oxygen isotope value of benthic foraminifera. Our findings suggest that the oxygen-rich water was present in the lower-intermediate layer resulting from intensified ventilation.

The origin and climate implications of authigenic carbonate minerals from Lake Qarun, Egypt, were examined in relation to the mid–late Holocene climate changes. These minerals occur as very thin (0.5–3 mm), very fine, well-sorted, white to pale yellow aragonite or calcite laminae intercalated with olive green clayey silt with sharp and horizontal contacts. Under the scanning electron microscope (SEM), aragonite appears as dense euhedral and ellipsoidal (rice-grained) crystals that range in length from 0.5 to 1 micron and in width from 0.2 to 0.5 micron. The calcite crystals are stubby, equant or blocky polyhedra of about 5 microns in length. δ 18 O values range between 2.7‰ and 3.7‰ for the calcite and between 2.1‰ and 6‰ for the aragonite. δ 13 C values range between 0.4‰ and 1‰ for the calcite and between 0.5‰ and 3.4‰ for the aragonite. A very strong positive correlation is observed between carbon and oxygen isotopes for the aragonite ( r 2 = 0.9) and a more moderate positive correlation with calcite ( r 2 = 0.6). The complete absence of biological and other no-carbonate grains, the sharp contacts of laminae basal, and the occurrence of calcite and aragonite as individual euhedral crystals, rather than clusters of grain aggregation, indicate that aragonite and calcite layers represent rapid inorganic precipitation from the lake water (endogenic). The positive values of δ 18 O and δ 13 C and the strong positive correlation between δ 18 O and δ 13 C suggest prevalence of a low lake level, saline, and dry climatic conditions during their formation. The change from calcite to aragonite indicates a change in the formational conditions from less arid conditions in the case of calcite to severe arid conditions in the case of aragonite. The relative abundance of diatoms in calcite-rich laminae and the less strong positive correlation between δ 18 O and δ 13 C of calcite support this interpretation. The arid conditions in which the carbonate minerals were formed could correspond to the aridification period of the North East Africa between ca 6000–8500 BP due to the north-south shifts of the Intertropical Convergence Zone (ITCZ) that control the evaporation/precipitation balance over North East Africa and/or to dry climate and desert environment conditions in Egypt at the same period. These results are also consistent with the aridification conditions during the mid-late Holocene, suggesting its global trend.

The Asian Monsoon forms an important part of the earth’s climate system, yet our understanding of the past interactions between its different sub-systems, the East Asian and Indian monsoons, and between monsoonal winds and other prevailing wind currents such as the Westerly jet, is limited, particularly in central Asia. This in turn affects our ability to develop climate models capable of accurately predicting future changes in atmospheric circulation patterns and monsoon intensities in Asia. Provenance studies of mineral dust deposited in terrestrial settings such as peat bogs can address this problem directly, by offering the possibility to examine past deposition rates and wind direction, and hence reconstruct past atmospheric circulation patterns. However, such studies are challenged by several issues, most importantly the identification of proxies that unambiguously distinguish between the different potential dust sources and that are independent of particle size. In addition, a single analytical method that is suitable for sample preparation of both dust source (i.e. desert sand, soil) and receptor (i.e. dust archive such as peat or soil profiles) material is desirable in order to minimize error propagation derived from the experimental and analytical work. Here, an improved geochemical framework of provenance tracers to study atmospheric circulation patterns and palaeomonsoon variability in central Asia is provided, by combining for the first time mineralogical as well as major and trace elemental (Sc, Y, Th and the rare earth elements) information on Chinese (central Chinese loess plateau, northern Qaidam basin and Taklamakan, Badain Juran and Tengger deserts), Indian (Thar desert) and Tibetan (eastern Qinghai–Tibetan Plateau) dust sources. Quartz, feldspars and clay minerals are the major constituents of all studied sources, with highly variable calcite contents reflected in the CaO concentrations. Chinese and Tibetan dust sources are enriched in middle REE relative to the upper continental crust and average shale but the Thar desert has a REE signature distinctly different from all other dust sources. There are significant differences in major, trace and REE compositions between the coarse and fine fractions of the surface sands, with the finest 2 O 3 , Fe 2 O 3 , MnO, MgO and K 2 O and the ∗ (all REE normalized to post-Archean Australian shale, PAAS) are particle size-independent tracers, of which combinations of Y/∑REE, La/Yb, Y/Tb, Y/La and Eu/Eu ∗ can be used to distinguish the Thar desert, the Chinese deserts, the Chinese loess plateau and the Tibetan soils. Their independence upon grain size means that these tracers can be applied to the long-range provenance tracing of Asian dust even when only bulk samples are available in the source region. Combinations of La/Th, Y/Tb, Y/∑REE, Sc/La and Y/Er distinguish the Tibetan soils from the Chinese loess plateau and the Chinese deserts. La/Th and notably Th/∑REE isolate the signature of the Badain Juran desert and the combination of Sc/La and Y/Er that of the Taklamakan desert. The similarity in all trace and REE-based provenance tracers between the northern Qaidam basin and Tengger desert suggests that these two deposits may have a common aeolian source.

article Oxidative precipitation and authigenic enrichment of the redox sensitive element Mn in sedimentary rocks can serve as a proxy for the release of high levels of O2 during the Great Oxidization Event (GOE). Here we investigate Mn abundance in sedimentary rocks of the 2.45-2.22 Ga Huronian Supergroup, Canada. We found authigenic Mn enrichments with high Mn/Fe ratios following the appearance of Fe oxides in the Firstbrook Member of the Gowganda Formation of the Huronian Supergroup, which was deposited immediately after the last Huronian glaciation. The Mn-bearing minerals in the Firstbrook Member are spessartine-rich almandine and Mn-bearing chlorite, which are likely to have been formed through post-depositional diagenesis and/or metamorphism using Mn oxides precipitated in the ocean at the time of deposition. When assuming the solution equilibrium between the atmosphere and shallow oceans, oxidative Mn precipitation requires that atmospheric O2 be higher than ~10 �2 times the present atmospheric level (PAL). The cumulative Mn amount per unit area in the Firstbrook Member is comparable in magnitude to that in the Mn deposits in the Hotazel Formation of the Transvaal Supergroup, South Africa. Our results suggest an appearance of highly active aerobic biosphere immediately after the last Huronian glaciation, supporting the hypothesis that climatic recovery from the Huronian glaciation accelerated the GOE.

It has been established that East Asian summer monsoon intensity varies with Dansgaard–Oeschger cycles, suggesting a connection between the climates of East Asia and the North Atlantic on a millennial timescale. However, the dynamics of such a connection are still unsolved. Here we demonstrate that temporal changes in the provenance of aeolian dust in Japan Sea sediments, which we interpret to reflect changes in the westerly jet path over East Asia, exhibit variations in harmony with Dansgaard–Oeschger cycles. The dominance of dust with a Mongolian Gobi provenance during stadials suggests a westerly jet axis located to the south of the Himalaya–Tibetan Plateau throughout most of the year, whereas the co-dominance of dust from both the Taklimakan Desert and the Mongolian Gobi during interstadials suggests that the westerly jet axis jumped to the north of the Tibetan Plateau at latest in summer. As the shift of the westerly jet axis to the north of the Tibetan Plateau is closely related to the onset of the East Asian summer monsoon, changes of the westerly jet path apparently critically affect the teleconnection between the climates of Asia and North Atlantic on a millennial timescale.

OSL components from quartz from two sediment cores (MD01-2407 and KT94-15-PC5) from the Japan Sea are analysed, and the results are compared with the electron spin resonance (ESR) intensity of E 1 ’-center of quartz and the grain size of the detrital component of the sediments. The OSL components of quartz from Japanese granites and rhyolites of different ages are also analysed to investigate the relationship between the host rock age and the relative composition of OSL components in quartz. All these data are then used to examine the potential of reconstructing the provenance of the sediments. The results suggest that the ratio of the Fast component to the sum of Fast and Medium, F/(F + M) appears to increase with increasing host rock age. It is suggested that the F/(F + M) ratio in sedimentary quartz can be used as an indicator of source rock age.

金沢大学理工研究域自然システム学系, The stable carbon isotopic compositions (δ13C) and chain-length distribution [ACL and n-C31/(n-C29+n-C31)] of sedimentary leaf wax n-alkanes were investigated across the Cretaceous-Paleogene (K-Pg) boundary at Loma Capiro, Central Cuba, to reconstruct paleoenvironmental changes that are recorded in terrestrial higher plants. The stratigraphic profiles of the n-alkane δ13C values show a negative excursion in the lowermost Paleocene, although its magnitude is much smaller (~0.3‰) than the global signals (1.5 to 2.0‰) in the surface ocean-atmospheric carbon reservoir. Relations between the n-alkane δ13C values and the C31/(C29+C31) ratios exhibit two different trends, suggesting that our δ13C records are likely affected by two types of paleoenvironmental factors in addition to the δ13C variations in the exogenous carbon reservoir. Rare occurrence of terrigenous organic matter that is usually transported by rivers suggests that the n-alkanes at Loma Capiro are likely to have been transported by trade winds, which recorded paleoenvironmental conditions of the northwestern part of the African continent. The n-alkane δ13C values show a parallel decrease with the ACL and C31/(C29+C31) values in the first 37,000yr following the K-Pg boundary. Such decreases are consistent with plant physiological responses to reduced net evaporation, suggesting a possible influence of the impact-induced warm-humid condition in the early Paleocene. In contrast, the n-alkane δ13C values are negatively correlated with the C31/(C29+C31) ratios from 40,000 to 67,000yr after the K-Pg boundary. This time period matches well with that required for the recovery of terrestrial floras from the K-Pg mass extinction to those with diversity equivalent to the late Cretaceous, suggesting that the n-alkane signals are also likely affected by the plant diversification process after the mass extinction. © 2010 Elsevier B.V.

Astronomical forcing is one of the main drivers of climate change, and astronomical cyclicity recorded in sediments provides a clue to understand the dynamics of the global climate system. Bedded cherts consist of rhythmic alternations of chert and shale beds. Although previous studies have hypothesized that the origin of bedded chert is related to astronomical cycles (e.g. Fischer, 1976; Hori et al., 1993), conclusive proof remains elusive. To explore this possibility, we established a continuous, high-resolution lithostratigraphy of middle Triassic bedded chert in Central Japan. The average duration of each chert–shale couplet is 20 kyr, similar to that of the precession cycle. Spectral analysis of a bed number series of thickness variations in chert beds was performed assuming that each chert–shale couplet represents a 20-kyr precession cycle. The results reveal cycles involving approximately 200, 20, 5, and 2–3 beds, corresponding to periodicities of approximately 4000, 400, 100, and 40–60 kyr, respectively. By further assuming that the 20-bed cycle represents a 405-kyr eccentricity cycle of constant and stable periodicity, we converted the bed number series to a time series. Spectral analysis of the time series revealed distinct periodicities of 3600, 117, 97, and 38 kyr, in addition to 405 kyr. Besides 3600 kyr, these periodicities agree well with the 120, 95, and 37 kyr periodicities for eccentricity cycles and the obliquity cycle during the Triassic. Moreover, we detected amplitude modulation of the approximately 100-kyr cycle of thickness variations in chert beds with a 405-kyr periodicity, which may correspond to amplitude modulation of 100-kyr climatic precession cycle with the 405-kyr periodicity. The approximately 3600-kyr periodicity described above and 1800-kyr periodicity manifested as the amplitude modulation of the 405-kyr cycle are correlated to present-day long-term eccentricity cycles of 2400 and 4800 kyr evolved by chaotic behavior of solar planets. Collectively, these similarities in the periodicities of dominant cycles, their hierarchy, and the nature of amplitude modulation of cycles in chert bed thickness with those of astronomical cycles strongly support the hypothesis that the sedimentary rhythm of bedded chert is paced by astronomical cycles, thereby indicating the potential of bedded chert as a template for a Mesozoic cyclostratigraphy.

The Tibetan Plateau is a key factor in controlling the present-day climate and atmospheric circulation pattern in Asia. The pattern of atmospheric circulation after the uplift of the plateau is well known, whereas direct evidence is lacking regarding the nature of the circulation pattern prior to the uplift. The distribution of desert directly reflects the position of the subtropical high-pressure belt, and the prevailing surface-wind pattern recorded in desert deposits reveals the position of its divergence axis. Cretaceous eolian sandstone of the Phu Thok Formation is extensively exposed in the northern Khorat Basin, northeastern Thailand. We conducted a sedimentological study on this formation to reconstruct temporal changes in the latitude of the subtropical high-pressure belt in low-latitude Asia during the Cretaceous. Spatio-temporal changes in the paleo-wind directions recorded in the Phu Thok Formation reveal that the Khorat Basin mainly belonged to the northeast trade wind belt and subtropical high-pressure belt was situated to the north of the Khorat Basin during the initial stages of deposition, shifted southward to immediately above the basin during the main phase of deposition, and then shifted northward again to the north of the basin during the final stages of deposition. The paleomagnetic polarity sequence obtained for the Phu Thok Formation comprises three zones of normal polarity and two of reversed polarity, correlating to chrons M1n to C34n of the geomagnetic polarity time scale. This result suggests that the Phu Thok Formation is mid-Cretaceous in age (from c. 126 Ma to c. 99–93 Ma), similar to the age of eolian sandstone in the Sichuan Basin, southern China (the Jiaguan Formation). These results, in combination with paleo-wind direction data, suggest the development of low-latitude desert and an equatorward shift of the subtropical high-pressure belt (relative to the present-day) in Asia during the mid-Cretaceous.

Sediment cores from Lake Qarun provide a record of mid-late Holocene climatic changes in Northern and Eastern Africa as well as environmental changes due to the activities of ancient Egyptians. We used sedimentological, mineralogical, and geochemical analyses of the cores to investigate long-term variations in lake level due to changing hydrologic inputs. An age model based on three paired 14C and paleomagnetic measurements suggests that the base of the sediment cores is as old as ∼5000 B.C.E. Geochemical analyses indicated that lake sediments were derived from Nile floods with an admixture of Saharan sand. Laminated endogenic carbonate-rich clayey silt lithofacies with benthic diatoms are indicative of relatively low lake levels, saline waters and dry conditions; massive lithofacies with planktonic diatom species are indicative of relatively high lake levels, fresh waters and humid conditions. Faintly laminated clayey silt lithofacies suggest intermediate conditions. Variations in lithology as w...

The Grain Size Influence on the E1' Centre Observed in Quartz of Atmospheric Deposition at Two Japanese Cities: A Preliminary Study The grain size influence on the number of oxygen vacancies in quartz was investigated by ESR in atmospheric deposition collected at two Japanese cities, Fukuoka and Akita, in 1969 and 1971. The finer grain size fraction shows the highest value of concentration of oxygen vacancies, most closely resembling dust originating in the Taklamakan desert. Month to month and year to year variation of the dependence was also observed which could possibly be attributed to the variation of the mixture ratio of at least two dust sources in China, A conclusive statement can not be made at this stage.

PETER D. CLIFT1*, RYUJI TADA2 & HONGBO ZHENG3 School of Geosciences, Meston Building, University of Aberdeen, Aberdeen, AB24 3UE, UK Department of Earth and Planetary Science, University of Tokyo, Science Building #1, 7-3-1 Hongo, Tokyo 113-0033, Japan Institute of Surficial Geochemistry, School of Earth Science and Engineering, Nanjing University, 22 Hankou Road, Nanjing, People’s Republic of China

A high-resolution abundance curve of the radiolarian species, Cycladophora davisiana, was obtained from a Late Pleistocene sediment core, PC-23A, which was obtained from the northern slope of the Bering Sea. The abundance pattern of this species was high during the glacial period and low during the Holocene. This general stratigraphic pattern was correlated with a previously reported pattern for the subarctic Pacific Ocean. However, planktonic foraminifera-based accelerator mass spectrometry 14C dating revealed that a significant peak in the C. davisiana curve during the glacial period correlates to 15.5 ka, which is younger than that previously estimated as being the Last Glacial Maximum. The higher abundance of this species implies that there was well-ventilated water with a large amount of organic matter in the intermediate-water layer. An unusually high propagation of C. davisiana during the earliest Holocene period, Bolling–Allerod (B-A) and Dansgaad–Oescheger interstadial event # 12, was most likely related to a significant increase in the amount of organic matter released into the intermediate-water depths by a brine pump system via ventilation. In addition, centennial-scale variations in the abundance of C. davisiana during the B-A period suggest that the intermediate-water ventilation was sensitively affected by brine rejection during sea ice formation as well as large-scale atmospheric circulations such as the Arctic Oscillation. Copyright © 2009 John Wiley & Sons, Ltd.

TL layers (i.e., dark mud layers), either thin or thick, as determined by the L* values with lithologic observation, are distinct paleoceanographic signatures in the East Sea (Sea of Japan), which were formed in response to the global eustatic sealevel fluctuations between interglacials and glacials during the Late Quaternary. These lithologic markers were consistently correlated among the three sediment cores (MD01-2407, 05GCRP21, and KR05-09PC1) collected from the Oki Ridge of the southern Yamato Basin, the South Korea Plateau of the northern Ulleung Basin, and the Matsumae Plateau of the northeastern Japan Basin, respectively. Reconstruction of age models for cores 05GCRP and KR05-09PC1 was aided in a good way by the AMS 14C ages of planktonic foraminifera and identification of the tephra layers, and mainly by lithostratigraphic correlation with TL layers of well-dated core MD01-2407, based on the L* values. The correlation of TL layers among the three sediment cores was remarkable, indicating that the East Sea (Sea of Japan) experienced the synchronous and basin-wide scale paleoceanographic events during the Late Quaternary. Our study exemplifies the significant usefulness of these lithologic markers for further Late Quaternary paleoceanographic investigation.

Non-marine Upper Cretaceous strata are widely distributed in the Gobi basin of southern Mongolia and record marked paleoenvironmental and paleoclimatic changes. The climate in this region is considered to have changed from humid during the Cenomanian to Santonian, to semi-arid during the Campanian, and returned to humid during the early Maastrichtian. The change from humid to semi-arid climate is well recorded in the “Djadokhta Formation” (as former division) in the Ulan Nuur basin of the central Gobi basin. In previous studies, the Djadokhta Formation was formally regarded as being characterized by eolian deposits formed under a semi-arid climate. However, the present study revealed that this formation comprises sub-humid fluvial lithofacies in the lower part and semi-arid eolian lithofacies in the upper part. Since the Djadokhta Formation was initially defined as a succession characterized by eolian lithofacies, it is proposed here that the lower part showing fluvial lithofacies should be separated from the “Djadokhta Formation” and is newly named as the Alagteeg Formation. The Alagteeg Formation is characterized by alternating beds of horizontally-bedded sandstone and mudstone, indicating sandy braided river, flood-plain, and ephemeral lake environments under sub-humid climate. The Djadokhta Formation (revised division) is further subdivided into two parts. The lower part is composed of large-scale cross-stratified sandstone, in situ and reworked calcretes, and thick mudstone lens, suggesting desert environments of broad sand dune fields with few inter-dune ephemeral river and pond deposits under semi-arid climate. On the other hand, the upper part comprises structureless sandstone with mature in situ calcretes, exotic pebbly sandstone and large-sized burrows. These lithofacies imply steppe environments with calcic soil development under semi-arid climate. This change from sub-humid to semi-arid climate during the Campanian is recorded not only in the Ulan Nuur basin but also in other regions of southern Mongolia as well as northern China. Hence, the broad aridification in the mid-latitudes of the Asian interior during the Campanian is inferred.

We measured 852 sets of planar deformation features (PDFs) in shocked quartz grains in impactite samples of the Yaxcopoil (YAX-1) core and from 4 Cretaceous/Tertiary (K/T) boundary deposits: the Monaca, the Cacarajcara, and the Pealver formations in Cuba, and DSDP site 536, within 800 km of the Chicxulub crater, in order to investigate variations of PDF orientations in the proximity of the crater. Orientations of PDFs show a broad distribution with peaks at ω {1013}, π {1012}, and ξ {1112}, plus r, z {1011} orientations with minor c(0001), s{1121}, t{2241} plus x{5161}, and m{1010} plus a{11-20} orientations. Planar deformation features with c(0001) orientation are relatively more abundant in the proximity of the Chicxulub crater than in distal sitessuch as North America, the Pacific Ocean, and Europe. This feature indicates that in the proximity ofthe crater, part of the shocked quartz grains in the K/T boundary deposits were derived from the lowshock pressure zones. Moreover, the orientations of PDFs with ξ {1122} plus r, z {1011} are high in our studied sites, and frequencies of these orientations decrease with increasing distance from the crater. On the other hand, absence of c(0001) and the rare occurrence of PDFs with ξ {1122} plus r, z {1011} orientations in the sample from the YAX-1 core that was taken at the top of the impactite layer of the Chicxulub crater suggests that the sampling horizon that reflects a certain cratering stage is also an important factor for variations in shocked quartz.

We report a newly developed provenance-tracing method by using a combination of electron spin resonance (ESR) signal intensity of the E1′ center in quartz and crystallinity index (CI) of quartz, which reflect the formation age and crystallization conditions of quartz in their source rocks, respectively. ESR signal intensity and CI were determined for quartz in fine silt plus clay fraction (

Phosphorite deposits in Egypt, known as the Duwi Formation, are a part of the Middle East to North Africa phosphogenic province of Late Cretaceous to Paleogene age. Phosphatic grains in these deposites are classified into phosphatic mudclasts and phosphatic bioclasts. Phosphatic bioclasts are subdivided into fish bone fragments and shark tooth fragments. All phosphatic grains are composed of francolite. Chemical mapping of the phosphatic grains using Electron Probe Microanalysis (EPMA) indicated that the phosphatic mudclasts are homogeneous in their chemical composition and no concentric texture nor chemical zoning are observed. Some of the bone fragments show Fe and S zoning. No significant difference in chemical composition is observed between the phosphatic mudclasts and bioclasts. Acid-insoluble residues of the phosphorites show lower values of the Chemical Index of Alteration (CIA) compared to the associated rocks. Structural CO2 contents in the francolites range from 3.32% to 7.21% with an average of 5.3%. The d 13 CPDB values range from � 4.04& to � 8.7&, while the d 18 OPDB values range from � 4.3& to � 10.3&. The compositional homogeneity of the mudclasts, Fe and S zoning in some of the bone fragments and the difference in the Chemical Index of Alteration between the acid-insoluble residues of the phosphorites and the associated rocks suggest that the phosphatic grains in the Duwi Formation are derived from pre-existing authigenic phosphorites, which reworked and concentrated afterward. Negative d 13 C values of structural CO2 suggest that the CO2 was derived from degradation of organic matter. Low d 18 O values of structural CO2 can be attributed to the influence of meteoric water. Higher CO2 ,S O 3 and F contents compared to the recent authigenic phosphorites and negative d 13 C and d 18 O values of structural CO2 indicate that diagenesis plays an important role in the modification of the chemical composition of phosphatic grains and that the studied apatite was francolitized during diagenesis. � 2007 Elsevier Ltd. All rights reserved.

We obtained twenty AMS (Accelerator Mass Spectrometry) radiocarbon dates, 2 tephra layer chronologies, and a planktonic foraminiferal δ 18 O stratigraphy for the last 50,000 years from Japan Sea cores from the Oki Ridge. In this paper we report AMS 14 C results that allow us to reconstruct a high-resolution chronology of the cores and discuss millennial scale climate changes recorded in Japan Sea sediments. The sedimentation rate for the site increased dramatically from the glacial stage to the Holocene as a result of significant hydrological changes associated with deglaciation and global sea-level rise. A lighter δ 18 O anomaly for the planktonic foraminifers was found during the LGM (Last Glacial Maximum). This shift corresponds to a freshening of the Japan Sea surface waters, and is mainly due to a global sea-level drop rather than anomalously warm SSTs (sea-surface temperatures) as previously reported. Our record combined with the global sea-level data suggests that the LGM started about 30 kyr ago and that the salinity of the Japan Sea became fresher than at present. The SSTs during MIS (Marine Oxygen Isotope Stage) 3 were relatively stable and global sea-level was not lower than ca. − 80 m. The surface water of the Japan Sea attained “normal” saline levels following the Younger Dryas cold event and reached the present-day δ 18 O values 7 kyr ago.