
Masako HoriOsaka Kyoiku University
Masako Hori
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36
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Introduction
Skills and Expertise
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August 2012 - March 2015
April 2010 - August 2012
Publications
Publications (36)
The oxygen isotope composition of diatom frustules is a potential paleoclimate archive; however, the temperature-dependent gradient of the oxygen isotopic records of diatoms is not supported by abiotic experiments. We synthesized amorphous silica under controlled water temperatures (10–40 °C) using the traditional sol-gel method to understand the t...
Stalagmites are useful archives in reconstructing paleoclimates: most paleoclimate studies used stalagmites that are distributed in specific locations and ages. We examined a stalagmite (GYM-1) collected from Nara Prefecture, central Japan, where limestone areas are limited. Applying ²³⁸ U– ²³⁴ U method, the ages of GYM-1 were determined as 744 ± 7...
In the East Asian monsoon area, stalagmites generally record lower and higher oxygen isotope (δ ¹⁸ O) levels during warm humid interglacial and cold dry glacial periods, respectively. Here, we report unusually low stalagmite δ ¹⁸ O from the last glacial period (ca. 32.2–22.3 ka) in Fukugaguchi Cave, Niigata Prefecture, Japan, where a major moisture...
We report here hourly variations of Mg/Ca, Sr/Ca, and Ba/Ca ratios in a Mediterranean mussel shell (Mytilus galloprovincialis) collected at the Otsuchi bay, on the Pacific coast of northeastern Japan. This bivalve was living in the intertidal zone, where such organisms are known to form a daily or bidaily growth line comprised of abundant organic m...
We report here hourly variations of Mg/Ca, Sr/Ca and Ba/Ca ratios in a Mediterranean mussel shell ( Mytilus galloprovincialis ) collected at the Otsuchi bay, on the Pacific coast of northeastern Japan. This bivalve was living in the intertidal zone, where such organisms are known to form a daily or bidaily growth line comprised of abundant organic...
Our understanding of stalagmite δ¹⁸O paleoclimate records would be significantly improved by determining the relative influence of the two factors, temperature and water δ¹⁸O. Here we apply carbonate clumped isotope thermometry to a well-dated (18.1–4.5 ka) stalagmite, Hiro-1 from Maboroshi Cave in Hiroshima Prefecture, southwestern Japan. The Δ47...
Spring waters from 16 sites distributed across the Kii Peninsula and surrounding islands in SW Japan were studied, to understand the origins of the metamorphic fluid; they were first classified into five types, based on a Piper diagram. Spring waters enriched in Na-K-HCO3 (referred to as type IV) exhibited rare earth element patterns with strong po...
Calcium carbonates (calcite and aragonite) were synthesized at 10–40 °C to understand the partitioning behavior of sodium during the mineralization of marine organisms. The role of organic ligands (acetic acid) in sodium partitioning into calcium carbonates was also investigated. The partitioning coefficient of sodium, defined as Kd = (Na/Ca)CaCO3/...
Two species of spinose planktonic foraminifera (Globigerinoides ruber and Globigerina bulloides), cultured under controlled seawater temperatures (19, 21, 23, and 25 °C) with newly precipitated walls labeled with Ca isotopes, were subjected to quantitative analyses of Mg/Ca, Sr/Ca and Ba/Ca ratios at a spatial resolution of 2 μm. Mg mapping of calc...
The vestiges of life in Eoarchean rocks have the potential to elucidate the origin of life. However, gathering evidence from many terrains is not always possible1,2,3, and biogenic graphite has thus far been found only in the 3.7–3.8 Ga (gigayears ago) Isua supracrustal belt4,5,6,7. Here we present the total organic carbon contents and carbon isoto...
Bivalve shell is one of the most important archives of past environmental changes because some species can live more than several decades and distribute broadly (e.g., from high to low latitude, fresh/brackish/sea water). We have investigated potential of long-lived cold water bivalve, Mercenaria stimpsoni (Stimpson's hard clam) living in North Eas...
Mercenaria stimpsoni (Stimpson's hard clam) is a shallow-water bivalve species distributed along mid- to high-latitude coasts of the Northwest Pacific influenced by the Oyashio cold current. As this animal can live for decades, oxygen isotopes of its shell can potentially provide long-term seawater temperature and salinity data. However, little is...
The Holocene stalagmite FG01 collected at the Fukugaguchi Cave in Itoigawa, central Japan provides a unique high-resolution record of the East Asian winter monsoon. Because of the climate conditions on the Japan Sea side of the Japanese islands, the volume of precipitation during the winter is strongly reflected in the stalagmite δ18O signal. Exami...
Insolation is an important component of meteorological data because solar energy is the primary and direct driver of weather and climate. Previous analyses of cultivated giant clam shells revealed diurnal variation in the Sr/Ca ratio, which might reflect the influence of the daily light cycle. We applied proxy method to sample from prehistoric era,...
This study examines the distribution of rare earth elements (REEs) in an 18-4.5 ka stalagmite in southwestern Japan, with the aim of assessing the utility of such data in paleoenvironmental reconstructions. Shale-normalized REEs (REEN) of this stalagmite generally contain two features: (1) a positive Eu anomaly and (2) heavy REE (HREE) enrichments....
Stalagmite oxygen stable isotopic records from Chinese and Japanese
caves have described the intensity of the East Asian summer monsoon
(EASM) in the late Quaternary. In this study, we present a stalagmite
δ18O record over the past 10,000 years from Fukugaguchi
Cave, Itoigawa, Honshu, Japan, facing the Japan Sea. The regional
climate is characteris...
To facilitate the measurement of U–Th isotopic compositions suitable for high-precision and high-resolution 230Th dating of coral and speleothem carbonates, secondary electron multiplier (SEM) protocol techniques for multicollector inductively coupled plasma mass spectrometry (MC-ICP-MS) have been developed. The instrumental sensitivities are 1–2%,...
East Asian monsoon (EAM) evolution during the last deglaciation has been shown repeatedly to be aligned with paleoclimatic changes in the North Atlantic, based on climate reconstructions comparing Asian speleothem records with Greenland ice cores. In contrast to this finding, paleoclimatic reconstructions based on Lake Suigetsu sediment cores sugge...
To facilitate the measurement of femtogram-quantity U-Th isotopic compositions suitable for high-precision and high-resolution speleothem Th-230 dating, secondary electron multiplier (SEM) protocol techniques for multicollector inductively coupled plasma mass spectrometry (MC-ICP-MS) have been developed. The instrumental sensitivities are 1-2%, wit...
Evolution of the East Asian monsoon (EAM) in the last deglaciation, synchronous with Northern Hemisphere (NH) thermal dynamics, has been predominately driven by solar insolation and NH climate. However, the mismatch of climate changes between Japan, located in the easternmost front of the EAM, inferred from Lake Suigetsu (Nakagawa et al., 2003, Sci...
To facilitate the measurement of femtogram-quantity U-Th isotopic compositions suitable for high-precision and high-resolution Th-230 dating of coral and speleothem carbonates, secondary electron multiplier (SEM) protocol techniques for multicollector inductively coupled plasma mass spectrometry (MC-ICP-MS) have been developed. The instrumental sen...
Dynamics of Asian monsoon (AM) rainfall in 20-40 degree N over the past millennia have been revealed. To understand ranfall variability in the low latitudinal AM region, duplicatable stalagmite delta18O records, ranging from -9.50/00 to -7.00/00, over the past 2800 years were measured for samples collected from Tine cave (09:44:16.6 N, 122:24:19.7...
The sediments of Challenger Mound, drilled during Integrated Ocean Drilling Program Expedition 307, show alternations of darker and lighter colored layers in ~10 m intervals. Lithified ho- rizons often observed in the lighter layers were interpreted as de- posits of interglacial periods. We performed high-resolution anal- ysis of minor elements (Mg...
Tufas, which are freshwater carbonates, are potential archives of terrestrial paleoclimate. Time series of stable isotopic compositions commonly show regular seasonal patterns controlled by temperature-dependent processes, and some perturbation intrinsic to the locality. We examined three tufa-depositing sites in southwestern Japan with similar tem...
Fluvial tufa deposits in southwest Japan commonly develop biannual lamination consisting of dense summer layers and porous winter layers, and the clearness of the laminae varies among the sites. The laminae have been largely attributed to a seasonally variable inorganic precipitation rate of calcite. This rate-controlled hypothesis was examined by...
Annually laminated carbonates, known as tufas, commonly develop in limestone areas and typically record seasonal patterns of oxygen- and carbon-isotope compositions. δ18O values are principally controlled by seasonal changes of water temperature, whereas δ13C values are the result of complex reactions among the gaseous, liquid, and solid sources of...
Tufas are freshwater carbonates widely developed in limestone areas under temperate and tropical climates. The stable isotopic and the other chemical properties of the tufas changes with climatic conditions. Because of the relatively high depositional rate and development of annual lamination, the tufas can be ideal paleoclimatic archives that supp...
The stable-isotope composition of a tufa collected on subtropical Miyako Island, southern Japan, records climatic and hydrologic changes over a 15-year period (1989-2003). A total of 450 subsamples taken at increments of 0.2 mm define the high-resolution isotopic profile of a 9-cm-long sample. The oxygen isotope values clearly exhibit cyclical chan...
岡山県西部の北部大賀台長屋の沢は,全長約1200 mに及び,大規模にトゥファが発達する.ここでは,石灰岩とその下位の砂岩頁岩相の低角スラスト境界から湧出した水が,長く急傾斜の流路沿いを流れる間にトゥファを堆積させている.湧水の水質の時期的変化は,これまで他地域で記載されてきた変化と類似する.ただし,夏期に溶存Ca2+濃度が低く,水温の季節的変化幅が大きいという特徴があり,これらは長屋の地下水塊が小さいことを示唆する.長屋の沢のトゥファには夏~秋の緻密層と冬~春の孔隙質層による,明瞭かつ規則的な年縞が発達する.孔隙質層中にはシアノバクテリアや珪藻が豊富に認められるが,緻密層には,径の大きな方解石結晶が発達し,微生物の痕跡は少ない.堆積物の組織的変化は,水質から計算された方解石沈殿速度のデータと...
We verified the appropriate conditions and the precisions of stable isotopic analyses for carbonate and water samples using a mass spectrometer with Gas Bench. Standard deviation and reproducibility of the analyses are dependent on the amount of carbon dioxide obtained from samples, and are minimized when the amount of carbonate sample of 0.09-0.14...
Chemical and isotopic compositions of water were measured at 46 carbonate hot-springs in Japan, by applying the methods avoiding the post-sampling alternation. Measured stable isotopic values indicate that CO2 of an endogenic origin was dissolved in water of a meteoric origin, in many cases. The carbonate springs are generally in intermediate tempe...