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Data report: grain size distribution of unconsolidated sands offshore Shimokita Peninsula, Japan (IODP Site C0020): Expedition 337

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Proceedings of the IODP

Integrated Ocean Drilling Program

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      Abstract

      We report particle size analyses measured from 28 unconsolidated sand samples recovered during Integrated Ocean Drilling Program Expedition 337 from Hole C0020A. These samples span from 1277 to 2002 meters below seafloor (mbsf) across two lithostratigraphic units that record a transition from a nearshore estuarine/intertidal to an offshore hemipelagic paleoenvironment. Most recovered lithologies, including coarse-grained lithologies, are semiconsolidated to consolidated; however, some intervals of sand are unconsolidated and suitable for particle size analysis. Bulk sand samples were measured using a laser diffraction particle size analyzer. All samples fall within the range of sand to silty sand, with silty sand more abundant deeper than 1925 mbsf. Samples contain 49%–97% sand, 3%–42% silt, and 0%–13% clay. Median grain diameter ranges from 55 to 405 µm. Clay and silt content in these sands reach a minimum at ~1500 mbsf and then increase below 1925 mbsf in a coal-bearing unit containing shale, siltstone, sandstone, and unconsolidated sand.

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      A Scale of Grade and Class Terms for Clastic Sediments

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        Variability of deltaic processes in terms of sediment supply, with particular emphasis on grain size

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          Microbial population structures in soil particle size fractions of a long-term fertilizer field experiment.

          Soil structure depends on the association between mineral soil particles (sand, silt, and clay) and organic matter, in which aggregates of different size and stability are formed. Although the chemistry of organic materials, total microbial biomass, and different enzyme activities in different soil particle size fractions have been well studied, little information is available on the structure of microbial populations in microhabitats. In this study, topsoil samples of different fertilizer treatments of a long-term field experiment were analyzed. Size fractions of 200 to 63 microm (fine sand fraction), 63 to 2 microm (silt fraction), and 2 to 0.1 microm (clay fraction) were obtained by a combination of low-energy sonication, wet sieving, and repeated centrifugation. Terminal restriction fragment length polymorphism analysis and cloning and sequencing of 16S rRNA genes were used to compare bacterial community structures in different particle size fractions. The microbial community structure was significantly affected by particle size, yielding higher diversity of microbes in small size fractions than in coarse size fractions. The higher biomass previously found in silt and clay fractions could be attributed to higher diversity rather than to better colonization of particular species. Low nutrient availability, protozoan grazing, and competition with fungal organisms may have been responsible for reduced diversities in larger size fractions. Furthermore, larger particle sizes were dominated by alpha-Proteobacteria, whereas high abundance and diversity of bacteria belonging to the Holophaga/Acidobacterium division were found in smaller size fractions. Although very contrasting organic amendments (green manure, animal manure, sewage sludge, and peat) were examined, our results demonstrated that the bacterial community structure was affected to a greater extent by the particle size fraction than by the kind of fertilizer applied. Therefore, our results demonstrate specific microbe-particle associations that are affected to only a small extent by external factors.
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            Author and article information

            Journal
            10.2204/iodp.proc.337.2013
            Proceedings of the IODP
            Integrated Ocean Drilling Program
            1930-1014
            11 December 2017
            10.2204/iodp.proc.337.203.2017

            This work is licensed under a Creative Commons Attribution 4.0 Unported License. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/

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