All issues
Volume 38 (2004)
- Issue 4 Pages 203-
- Issue 3 Pages 117-
- Issue 2 Pages 45-
- Issue 1 Pages 1-
Volume 38, Issue 4
Displaying 1-8 of 8 articles from this issue
- |<
- <
- 1
- >
- >|
Orignal paper
-
Atsuyuki OHTA, Noboru IMAI, Shigeru TERASHIMA, Yoshiko TACHIBANA2004 Volume 38 Issue 4 Pages 203-222
Published: December 27, 2004
Released on J-STAGE: January 19, 2017
JOURNAL FREE ACCESSWe created geochemical maps of the Chugoku region, Japan by chemical analysis of 265 stream sediments and examined the background distribution of elemental concentrations. The geochemical maps strongly reflect the surface geology and mineral deposits. Factor analysis applied for our geochemical data suggests that granite, felsic volcanic, and mafic-ultramafic rocks mainly control the spatial distribution of elemental concentrations in stream sediments. The correspondence of elemental concentrations to respective surface geology is clearly revealed by a multiple comparison. The spatial distributions of Be, Na2O, Nb, rare earth elements, Ta, Th, and U contents correspond to granite distribution. Felsic volcanic rock contributes to high concentrations of Rb, Cs, Ba, and Tl. The distributions of MgO, Al2O3, P2O5, CaO, 3d transition metals (except Cu), and Sr concentrations are controlled by mafic and ultramafic rocks. The ultramafic rock has very strong influence to the spatial distributions of MgO, Cr, Ni, and Co concentrations, although they crop out in a small area. However, limestone in accretionary complexes has no positive effect on CaO and Sr abundances in stream sediments. The distribution patterns of some elements (Cu, Zn, As, Mo, Cd, Sn, Sb, Hg, Pb, and Bi) have close relationships to the distributions of mineral deposits such as Cu, Zn-Pb, As-Sb, W-Sn-Mo, and Hg deposits. Especially, Akenobe and Ikuno mines (the largest hydrothermal deposits in the study area), and Yoshioka, Mihara, and Koizumi mines (hydrothermal and skarn deposits) contribute to highly enrichments of these elements. However, not all geochemical anomalies for these elements correspond to the distributions of mineral deposits. The active erosion and heterogeneity of ores in stream sediments probably hide their influence to elemental distribution.View full abstractDownload PDF (2700K)
Special Section “Coral annual bands and ocean environments in the low latitude”
-
Hodaka KAWAHATA, Atsushi SUZUKI2004 Volume 38 Issue 4 Pages 223-224
Published: December 27, 2004
Released on J-STAGE: January 19, 2017
JOURNAL FREE ACCESSThe latest developments of studies on coral skeleton were compiled in this volume in order to understand the climatic and ocean environmental changes in low-latitude oceans. Recently, high-precession measurement of skeletal oxygen isotope ratios combined with Sr/Ca thermometry has become known as one of the promising methods for reconstruction of paleo-seawater temperature and water budget including rainfall, evaporation and deep-water upwelling. These parameters are closely related to El Niño-Southen Oscillation (ENSO) and Asian monsoon. New proxies for climatic and/or ocean environmental records will promote our understanding of the earth's surface environments.View full abstractDownload PDF (250K)
Reviews
-
Yasushi KITANO2004 Volume 38 Issue 4 Pages 225-239
Published: December 27, 2004
Released on J-STAGE: January 19, 2017
JOURNAL FREE ACCESSIt was happy for me to participate in the Coral Annual Banding Workshop held in Tsukuba on Oct. 20, 2003, as a commentator. In the workshop, I was impressed greatly by the presentation of the fresh and exciting stories. I have made the chemical and geochemical studies on carbonates for these fifty years. I have published many reports on the following subjects: (a) geochemical study on calcareous deposits in 17 hot springs of Japan, (b) factors controlling the polymorphic crystallization of CaCO3, especially the influence of chemical species dissolved in parent solution, (c) partition of minor chemical species between CaCO3 and solution: divalent cations (Mg2+, Cu2+, Zn2+, Cd2+, Sr2+, Ba2+, UO22+), alkaline ions (Li+, Na+, K+, Rb+, Cs+), inorganic anions (halogen ions, SO42-, phosphate ions, borate ions), H4SiO4 and organic materials, (d) geochemical study on marine biogenic carbonates, (e) synthesis of (Ca, Mg) CO3 under normal temperature and pressure condition, (f) transformation of marine biogenic carbonates, (g) origin and evolution of seawater using those of CO2 on the earth, and (h) global warming. At the workshop, I hoped heartily and strongly for active geochemists on coral to promote the basic studies on the strange but interest characters of CaCO3 and also to present the exact data on global carbon cycle. My hope and expectation are shown in this paper with the chemical and geochemical results obtained by myself.View full abstractDownload PDF (1571K) -
Maki MORIMOTO2004 Volume 38 Issue 4 Pages 241-254
Published: December 27, 2004
Released on J-STAGE: January 19, 2017
JOURNAL FREE ACCESSAlthough tropical oceans are a key component of the global climate system, their behavior in the past - even only a few decades ago - remains poorly characterized. Coral skeletons can provide several centuries of continuous paleoclimatic records with weekly to annual resolution. The skeletal oxygen isotope ratio (δ18O) is one of the most commonly used coral-based paleoclimatic proxies. The skeletal δ18O values reflect a combination of temperature and the δ18O of ambient surface seawater, and seawater δ18O and sea surface salinity are affected by similar factors. Many calibration studies have sought to validate skeletal δ18O as a paleoclimatic tracer and to define the relationship between skeletal δ18O, temperature, seawater δ18O and salinity. The time resolution of this calibration is increasing; it currently occurs biweekly in the Palau Islands in the tropical Western Pacific. Generally, changes in sea surface temperature and seawater δ18O have almost the same effect on changes in skeletal δ18O, both temporally and spatially. Local contribution rates of these two factors to skeletal δ18O differ owing to regional climatic conditions. Parallel studies of detailed calibrations and an expansion of coral skeletal δ18O datasets over the next decade are anticipated to lead to many developments in paleoclimatic understanding.View full abstractDownload PDF (1604K) -
Tsuyoshi WATANABE, Anne Juillet-Leclerc, Jean-Pierre Guif, Anders Meib ...2004 Volume 38 Issue 4 Pages 255-264
Published: December 27, 2004
Released on J-STAGE: January 19, 2017
JOURNAL FREE ACCESSMassive corals have been widely used as proxies for past changes in sea surface temperature (SST) of the tropical and subtropical oceans because the oxygen isotopic (δ18O) and strontium/calcium (Sr/Ca) ratios of their aragonitic skeletons are believed to vary quantitatively as a function of the temperature of the ambient sea water. However, recent microanalytical studies using secondary ion mass spectrometry (SIMS) have revealed large chemical heterogeneities for Sr/Ca and oxygen isotopic ratios in coral skeleton, which cannot be explained by temperature variation. The newly developed NanoSIMS has a potential to determine chemical variations within the two basic building blocks of the coral skeleton; centres of calcification and fibers. Such data can provide important new information about the biomineralization process and help constrain the degree to which temperature and/or biological processes affect the composition of skeleton in corals, as well as in biogenetic carbonates formed by other marine organisms.View full abstractDownload PDF (1650K) -
Atsushi SUZUKI, Hodaka KAWAHATA2004 Volume 38 Issue 4 Pages 265-280
Published: December 27, 2004
Released on J-STAGE: January 19, 2017
JOURNAL FREE ACCESSFrequent coral bleaching has been observed in tropical and subtropical seas during the last three decades. These recurrent coral bleaching events may be a response to global warming. The influence of bleaching on the isotopic composition of coral skeletons has been controversial. Some studies reported clear changes associated with bleaching events, while these changes remained less evident in other reports. Since bleaching can result in a substantial decrease in skeletogenesis, a very fine sampling technique would be needed to detect the corresponding isotopic changes in the coral skeleton. We introduce a recent progress achieved by a high-resolution skeletal isotope microprofiling technique. Using this technique, bleached corals from Pandora Reef, Great Barrier Reef and Ishigaki Island, Japan showed a dramatic decrease in skeletogenesis, together with a reduction in the carbon isotopic values, coincident with the worldwide severe bleaching event in 1997/98. Such changes are consistent with the hypothesis that reduced photosynthesis acts to decrease the carbon isotopic values of the skeleton. However, the drastic reduction in growth would lead to an increase in carbon isotope ratios and may have resulted in subduing the 13C-response to bleaching. The results indicate that isotopic microprofiling may be the key to identifying gaps in coral growth that are diagnositic of past bleaching events.View full abstractDownload PDF (2451K) -
Takashi OKAI, Atsushi SUZUKI, Shigeru TERASHIMA, Mayuri INOUE, Masato ...2004 Volume 38 Issue 4 Pages 281-286
Published: December 27, 2004
Released on J-STAGE: January 19, 2017
JOURNAL FREE ACCESSThe chemical composition of coral skeleton and clamshell is closely linked to the composition of surface sea water in which skeletal or shell calcium carbonate is precipitated. For this reason, several chemical components in coral and clam have been determined to be indicatrs of sea surface environmental conditions. However, there is no reference material having the same chemical composition as coral or clam. Therefore, GSJ/AIST has issued the reference materials JCp-1 (Coral Porites sp.) and JCt-1 (Giant Clam Tridacna), for the determination and evaluation of elements in coral, clam and other biogenic carbonates. In this study, collaborative analysis for the certification of reference materials JCp-1 and JCt-1 was carried out in ten laboratories. The analytical data were compiled for 9 components (CaO, Ba, Fe, K, Mg, Mn, Na, P and Sr). The ICP-AES and AAS were mainly used, and the analytical results agreed relatively well. In the statistical analysis, the reference values were mainly decided using the robust method. ISO typically recommends that data should be submitted from no fewer than 15 laboratories for deciding the certified values; the reference values given in this paper could be considered as preliminary certified values.View full abstractDownload PDF (615K) -
Takehiro MITSUGUCHI2004 Volume 38 Issue 4 Pages 287-301
Published: December 27, 2004
Released on J-STAGE: January 19, 2017
JOURNAL FREE ACCESSRadiocarbon (14C) is one of the most important tracers for the global ocean circulation because of its half-life (5,730 years) comparable to the time span taken by surface-ocean water to circulate to the ocean bottom and back (1,000-2,000 years). 14C is produced naturally in the upper atmosphere, quickly combined with oxygen to form radioactive carbon dioxide (14CO2), and incorporated into the ocean, soil, vegetation, etc. Since the atmosphere circulates very rapidly, the global distribution of atmospheric 14C is almost uniform. On the other hand, 14C concentration in the ocean varies markedly according to depth, region, and water mass because of the timescale of the global ocean circulation (1,000-2,000 years), local water-mass movements, etc. Atmospheric testing of nuclear bombs performed in the latter 1950s and early 1960s increased atmospheric 14C concentration by 70-100%. The bomb-produced 14C was incorporated into the surface ocean via air-sea CO2 exchange, and surface water was greatly enriched in 14C relative to deeper water. This provided a favorable opportunity to investigate the vertical mixing between surface water and deeper water. Hermatypic corals secrete CaCO3 skeletons in the tropical/subtropical surface ocean, with some species forming annual growth bands in their skeletons and occasionally growing to form gigantic colonies containing hundreds of years of coral growth. 14C analysis of annually-banded coral skeletons, which started in the 1970s, has provided a lot of information about past sea-surface 14C concentration in the tropics and subtropics, contributing to our understanding of vertical mixing and horizontal advection in the ocean. Here, I enunciate the rationale for 14C analysis of coral annual bands, review the results obtained so far, and discuss the usefulness of this method for the study of ocean environment.View full abstractDownload PDF (1823K)
- |<
- <
- 1
- >
- >|