Toshitsugu Yamazaki

We have conducted a paleomagnetic study of six sediment cores taken from the equatorial Pacific, three from the West Caroline Basin and three from the Manihiki Plateau, in order to make a relative paleointensity stack during the Matuyama and late Gauss Chrons. The age of the bottom of the cores ranges from 1.2 to 3.0 Ma. The sediments show little downcore changes in the proxies of magnetic grain size and mineralogy and are hence suitable for estimating relative paleointensity. The age of the cor

A continuous record of the inclination and intensity of Earth's magnetic field, during the past 2.25 million years, was obtained from a marine sediment core of 42 meters in length. This record reveals the presence of 100,000-year periodicity in inclination and intensity, which suggests that the magnetic field is modulated by orbital eccentricity. The correlation between inclination and intensity shifted from antiphase to in-phase, corresponding to a magnetic polarity change from reversed to norm

A rock-magnetic and paleomagnetic study was conducted on a sediment core of about 4.4 m long taken from the northeastern part of the Japan Sea. The core covers the last about 30 kyrs, which was dated by nineteen radiocarbon (14C) ages. Remanent magnetization is carried dominantly by magnetite. Reductive dissolution of magnetic minerals occurs between 1.2 and 1.6 m in depth (about 5–8 ka in age). A rapid downcore decrease of anhysteretic remanent magnetization (ARM) begins at the shallowest depth

Research Article| December 01, 1998 Organic carbon flux controls the morphology of magnetofossils in marine sediments Toshitsugu Yamazaki; Toshitsugu Yamazaki 1Geological Survey of Japan, 1-1-3 Higashi, Tsukuba 305-8567, Japan Search for other works by this author on: GSW Google Scholar Hodaka Kawahata Hodaka Kawahata 1Geological Survey of Japan, 1-1-3 Higashi, Tsukuba 305-8567, Japan Search for other works by this author on: GSW Google Scholar Geology (1998) 26 (12): 1064–1066. https://doi.org/

In the Southern Ocean, magnetic mineral concentration increases in glacial periods. The variation pattern closely resembles eolian dust flux records from Antarctic ice cores, but the cause of the linkage remains unclear, as the dust flux is too small for the source of terrigenous materials in the Southern Ocean. We have conducted an environmental magnetic study of late Pleistocene sediments from the south Indian Ocean to investigate the origin of the magnetic concentration changes. Biogenic magn

High-resolution spectroscopy of ${\ensuremath{\pi}}^{+}$ from ${K}^{\ensuremath{-}}$ absorption at rest has been used for the first time to identify ${\ensuremath{\Sigma}}^{\ensuremath{-}}$ hypernuclear states. The observed spectrum from a ${(\mathrm{CH})}_{n}$ target has revealed a ${p}_{\frac{3}{2}}\ensuremath{-}{p}_{\frac{1}{2}}$ doublet of $_{{\ensuremath{\Sigma}}^{\ensuremath{-}}}^{12}\mathrm{Be}$ with narrow widths. The spin-orbit splitting of ${\ensuremath{\Sigma}}^{\ensuremath{-}}$ is de

An environmental magnetic study was conducted to investigate temporal variations of the sources of magnetic minerals in the Pacific Ocean using sediment cores of Pleistocene age. The proportion of interacting (I) to noninteracting (N‐I) single‐domain components was estimated from first‐order reversal curve diagrams, and the proportion of middle‐ (M) to low‐ (L) coercivity components was determined from decomposition of isothermal remanent magnetization (IRM) acquisition curves. The I and M compo

We conducted a rock‐magnetic study of pelagic sediments in order to document variations of Asian eolian input to the North Pacific since the Pliocene. The materials studied consist of five pelagic‐clay (red‐clay) cores of several meters long taken from the central North Pacific and surface sediments of box cores obtained at 40 sites along two lines, a N‐S line along 175°E and an E‐W line along 20°N. The magnetic susceptibility (concentration of magnetic minerals) and S ratio (relative abundance

Understanding magnetostatic interactions in sediments is important for paleomagnetism and rock magnetism. Magnetostatic interactions are known to affect significantly the efficiency of anhysteretic remanent magnetization (ARM) acquisition, and hence the ratio of ARM susceptibility ( χ ARM ) to saturation isothermal remanent magnetization (SIRM), a magnetic grain‐size proxy widely used for environmental applications, can be controlled by magnetostatic interactions. Relative paleointensity estimat

Research Article| February 01, 2012 Paleoposition of the Intertropical Convergence Zone in the eastern Pacific inferred from glacial-interglacial changes in terrigenous and biogenic magnetic mineral fractions Toshitsugu Yamazaki Toshitsugu Yamazaki Geological Survey of Japan, National Institute of Advanced Industrial Science and Technology, Higashi, Tsukuba 305-8567, Japan Search for other works by this author on: GSW Google Scholar Author and Article Information Toshitsugu Yamazaki Geological S

Research Article| November 01, 2013 Abundant bacterial magnetite occurrence in oxic red clay Toshitsugu Yamazaki; Toshitsugu Yamazaki * 1Geological Survey of Japan, National Institute of Advanced Industrial Science and Technology, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8567, Japan2Graduate School of Life and Environmental Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8572, Japan3Atmosphere and Ocean Research Institute, University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 2