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Abstract  The internal structure and composition of a 37-mm-thick Co-rich Mn crust from the Lamont Guyot in the Marcus-Wake Seamount cluster have been studied in detail by means of electron-probe microanalysis (EPMA). 184 point analyses for 16 elements were carried out at an average spacing of 0.20 mm and each point was dated using the Co-geochronometer method. Two types of variation in composition were observed in the crust: long-term trends and short-term erratic variations. The long-term trends were identified using the fifth order polynomial. Mn and Ni were shown to increase in concentration from 23.3 Ma to a maximum at about 20 Ma and then decline steadily to the Present, whereas Fe, P and Si showed the opposite trend. By contrast, Co displayed a double humped pattern with maxima at about 19 Ma and 3.5 Ma and minima at 23.3 Ma, about 11 Ma and at Present. The long-term trends in element concentrations in the crust lead us to suggest that much of the Fe in western Pacific Ocean ferromanganese crusts is aeolian in origin and derived from the deserts of central Asia. Cooling of the Asian mainland at about 20 Ma led to an increase in the flux of Fe to the oceans. This was supplemented by an additional input of Fe into the crusts as a consequence of the dissolution of biogenic CaCO3 tests at 4.5−10.5 Ma. For the short-term erratic variations, three periods of 0.61, 0.96 and 1.65 m.y. were identified by spectral analysis. The second harmonics of these periods are 1.22, 1.92 and 3.30 m.y., which may correspond to the highest-order periods for eccentricity of 1.31, 2.04 and 3.47 m.y. This suggests the possibility that the high-frequency oscillations of the time series data are linked to climatic changes controlled by the highest-order periods of the Milankovitch cycles. [ABSTRACT FROM AUTHOR]

Radiochemical separation techniques were applied to measure 210Pb radioactivity in samples to determine spatial distribution of total 210Pb radionuclide in surface sediments and water column for the main waters on the Sunda Shelf. The average 210Pb radioactivity level recorded for the Malacca Strait (MS) is significantly higher than that of the southern South China Sea (sSCS); this is attributed to the supply of input from the Andaman Sea in its northern areas, and massive terrestrial processes from bordering land masses. The results reveal that the decreasing trend of total 210Pb in Peninsular Malaysia's marine sediment starts with the north maritime zone of Malacca Strait (64.28 ± 5.97 Bq/kg) > south maritime zone of Malacca Strait (50.88 ± 6.15 Bq/kg) > east maritime zone of sSCS (41.01 ± 3.07 Bq/kg) > south maritime zone of sSCS (40.78 ± 3.16 Bq/kg). The Kelantan and Pahang Deltas have been identified as two of the main anthropogenic sources of input for total 210Pb in the sSCS with atmospheric transboundary mobilization affecting total 210Pb in the water column. In the Malacca Strait, however, the distribution of total 210Pb might be influenced mainly by in situ processes of the strait's seafloor and sources origin of sediment. [ABSTRACT FROM AUTHOR]

Eolian material within pelagic North Pacific Ocean (NPO) sediments contains considerable information about paleoclimate evolution in Asian dust source areas. Eolian signals preserved in NPO sediments have been used as indices for enhanced Asian interior aridity. We here report a detailed eolian dust record, with chemical index of alteration (CIA) and Rb/Sr variations, for NPO sediments from Ocean Drilling Program Hole 885A over the past 4.0 m.y. CIA and Rb/Sr co-vary with the dust signal carried by combined eolian hematite and goethite concentrations. Changes in CIA around the intensification of Northern Hemisphere glaciation (iNHG) event at ca. 2.75 Ma indicate that dust production in source areas was associated mostly with physical and chemical weathering before and after the iNHG event, respectively. We here attribute the eolian flux increase into the NPO across the iNHG event mainly to increased availability of wind-erodible sediment in dust source areas derived from snow and glacial meltwater runoff, which resulted from glacial expansion and enhanced snowfall in the mountains surrounding the Tarim region in response to global cooling. Our results provide a deeper understanding of Asian interior environmental changes in response to global paleoclimate changes, where dust source areas became intermittently moister rather than more arid in response to global cooling. [ABSTRACT FROM AUTHOR]

This paper presents results of a high-resolution study of bottom sediments from the central and northern parts of the Chukchi Sea. Magnetic susceptibility and grain size distribution within the sediments indicate calm depositional conditions of mainly lithogenic material. The biogenic material is dominated by SiO 2bio (up to 15%) and to a much lesser extent by C org (up to 2%) and N tot (up to 0.25%). The distinct increase of organic material within the uppermost parts of the cores causes a decrease of magnetic susceptibilty and reflects an increase of biological productivity of the Chukchi Sea, triggered by global warming of the climate. Fallout activity peaks of 137Cs, measured in the core taken in the central area of the Chukchi Sea, are assumed to represent the fall-out of the accidents of the Chernobyl nuclear power plant in 1986 and of the Fukushima nuclear power plant in 2011. The two fallout peaks of 137Cs in the sediments of the northern area correspond to the maximum of the atmospheric tests of nuclear weapons in 1963 and to the accident at Chernobyl nuclear power plant in 1986. Rates of recent sedimentation, dated by 137Cs fall-out peaks and by additional measurements of 210Pb are estimated to be 2–2.7 mm a−1 in the central part and 0.9–1.3 mm a−1 in the northern part of the Chukchi Sea. [ABSTRACT FROM AUTHOR]

In order to rationally develop abundant marine clay resources, in view of its large specific surface area, looseness, high porosity, poor crystallinity, and high activity, the magnesium thermal reduction method was used to reduce Si4+ in the pelagic clay minerals to obtain porous silicon. Through targeted process design and reaction condition control, the obtained silicon material not only has higher crystallinity, but also has layered accumulation pores with relatively uniform pore size distribution. It had a BET specific surface area of 81.473 m2·g−1, a pore volume of 0.290 cm3·g−1, and an average pore size of 10.193 nm. In addition, using sucrose as the carbon source, the prepared silicon was modified to obtain a carbon-coated porous silicon material, whose performance as lithium-ion battery negative electrode was preliminarily characterized. The specific capacity, cycling performance and multiplicity performance test results showed that the porous silicon derived from pelagic clay exhibits good cycling and rate performance under the carbon coating conditions, which means that it had a certain potential in the field of lithium-ion batteries. This work opened up a new way for high value-added utilization of pelagic clay. Using pelagic clay as raw material, porous silicon materials that can be used in the anode of lithium-ion batteries were prepared by magnesium thermal reduction method. The obtained porous silicon exhibited good electrochemical properties after a simple carbon coated. [Display omitted] • PC-Si for lithium-ion battery anode applications is prepared by combining PC with MR. • The PC-Si is a three-dimensional layered and porous structure • This work opened up a new way for high value-added utilization of pelagic clay. [ABSTRACT FROM AUTHOR]