Pub Date : 1900-01-01DOI: 10.5026/JGEOGRAPHY.118.156
C. Aoyama, R. Matsumoto
During methane hydrate exploration and research, remote and on-board acoustic surveying and monitoring of methane hydrate can be easily and economically conducted using a quantitative echo sounder. Simultaneously, the structure and the floating-up speed of methane plumes can be obtained from an analysis of acoustic data. We conducted a survey of methane plumes from 2004 through 2008 at a spur situated southwest off the coast of Sado Island (tentatively called Umitaka Spur) and at the Joetsu Knoll. In 2007 and 2008, we performed experiments by releasing methane hydrate bubbles and methane hydrate, and letting them float upward. Consequently, we demonstrated that acoustical reflection from the methane plumes correlates with water temperature and depth, that the floating-up speed is constant but depends on the conditions of methane hydrate, that the discharge of methane hydrate bubbles changes, and that there is a wide scattering of materials below the seafloor where methane plumes are located. Furthermore, the amount of methane hydrate bubbles seeping was estimated by a preliminary calculation. The method will be applied not only to basic research on methane hydrate but also to assessments of the environmental impact of methane hydrate exploitation.
{"title":"Acoustic Surveys of Methane Plumes by Quantitative Echo Sounder in Japan Sea and the Estimate of the Seeping Amount of the Methane Hydrate Bubbles","authors":"C. Aoyama, R. Matsumoto","doi":"10.5026/JGEOGRAPHY.118.156","DOIUrl":"https://doi.org/10.5026/JGEOGRAPHY.118.156","url":null,"abstract":"During methane hydrate exploration and research, remote and on-board acoustic surveying and monitoring of methane hydrate can be easily and economically conducted using a quantitative echo sounder. Simultaneously, the structure and the floating-up speed of methane plumes can be obtained from an analysis of acoustic data. We conducted a survey of methane plumes from 2004 through 2008 at a spur situated southwest off the coast of Sado Island (tentatively called Umitaka Spur) and at the Joetsu Knoll. In 2007 and 2008, we performed experiments by releasing methane hydrate bubbles and methane hydrate, and letting them float upward. Consequently, we demonstrated that acoustical reflection from the methane plumes correlates with water temperature and depth, that the floating-up speed is constant but depends on the conditions of methane hydrate, that the discharge of methane hydrate bubbles changes, and that there is a wide scattering of materials below the seafloor where methane plumes are located. Furthermore, the amount of methane hydrate bubbles seeping was estimated by a preliminary calculation. The method will be applied not only to basic research on methane hydrate but also to assessments of the environmental impact of methane hydrate exploitation.","PeriodicalId":356213,"journal":{"name":"Chigaku Zasshi (jounal of Geography)","volume":"115 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128176191","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1900-01-01DOI: 10.5026/JGEOGRAPHY.117.93
K. Michibayashi
Peridotites derived from the uppermost mantle consist dominantly of olivine and subsequently of pyroxene, spinel, garnet, and plagioclase. Crystal-plastic flow of mantle rocks results in various types of structure within peridotite being developed to varying degrees, depending upon the structure sensitivity of the different mineral phases. Plastic deformation leads to the simultaneous development of shape-preferred orientations and crystal-preferred orientations. A shape-preferred orientation is the expression of the average orientation of flattening (foliation) and elongation (lineation) directions, as defined by the orientations of individual grains. A crystal-preferred orientation (CPO) is the expression of crystallographic orientations of grains within the rock, as developed via dislocation creep and recrystallization. During intense homogeneous plastic deformation of a peridotite composed of minerals with a dominant slip system, the preferred orientation of the slip plane and slip direction tends to coincide with the plane of plastic flow and the flow direction, respectively. Recently, a new olivine CPO classification (A, B, C, D, and E types) has been proposed by Karato and co-workers to illustrate the roles of stress and water content as controlling factors of olivine slip systems. An additional CPO type (AG) has also been proposed in recognition of its common occurrence in nature. Given that olivine and the other constituent minerals in peridotites contain intrinsic elastic anisotropies, the development of CPO within peridotite during plastic deformation gives rise to seismic anisotropy in the upper mantle. Thus, the anisotropic properties of mantle rocks derived from the upper 100 km of the mantle, such as Ichinomegata peridotite xenoliths from the northeast Japan arc, have been calculated and applied with the aim of understanding the seismic anisotropy of the Earth's mantle.
{"title":"Structure Sensitivity and Elastic Anisotropy within Peridotites","authors":"K. Michibayashi","doi":"10.5026/JGEOGRAPHY.117.93","DOIUrl":"https://doi.org/10.5026/JGEOGRAPHY.117.93","url":null,"abstract":"Peridotites derived from the uppermost mantle consist dominantly of olivine and subsequently of pyroxene, spinel, garnet, and plagioclase. Crystal-plastic flow of mantle rocks results in various types of structure within peridotite being developed to varying degrees, depending upon the structure sensitivity of the different mineral phases. Plastic deformation leads to the simultaneous development of shape-preferred orientations and crystal-preferred orientations. A shape-preferred orientation is the expression of the average orientation of flattening (foliation) and elongation (lineation) directions, as defined by the orientations of individual grains. A crystal-preferred orientation (CPO) is the expression of crystallographic orientations of grains within the rock, as developed via dislocation creep and recrystallization. During intense homogeneous plastic deformation of a peridotite composed of minerals with a dominant slip system, the preferred orientation of the slip plane and slip direction tends to coincide with the plane of plastic flow and the flow direction, respectively. Recently, a new olivine CPO classification (A, B, C, D, and E types) has been proposed by Karato and co-workers to illustrate the roles of stress and water content as controlling factors of olivine slip systems. An additional CPO type (AG) has also been proposed in recognition of its common occurrence in nature. Given that olivine and the other constituent minerals in peridotites contain intrinsic elastic anisotropies, the development of CPO within peridotite during plastic deformation gives rise to seismic anisotropy in the upper mantle. Thus, the anisotropic properties of mantle rocks derived from the upper 100 km of the mantle, such as Ichinomegata peridotite xenoliths from the northeast Japan arc, have been calculated and applied with the aim of understanding the seismic anisotropy of the Earth's mantle.","PeriodicalId":356213,"journal":{"name":"Chigaku Zasshi (jounal of Geography)","volume":"63 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126829430","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1900-01-01DOI: 10.5026/JGEOGRAPHY.118.776
O. Takano, Mizue Nishimura, T. Fujii, T. Saeki
Since previous research revealed that most of the methane hydrates in the eastern Nankai Trough area occur in matrix pores of turbidite sandstones, the facies distribution of turbidite sandstones may be one of the important keys to evaluate the distributions and actual volume of methane hydrates in the eastern Nankai Trough area. This paper attempts to reconstruct depositional processes of submarine-fan turbidites, and examines the relationship between turbidite facies distributions and bottom simulating reflector (BSR) occurrence as a proxy of methane hydrate using sedimentologic and sequence stratigraphic methodology. First, 2D/3D seismic survey data and well data including cores and logs were used to identify turbidite facies, seismic facies, and depositional sequences. The targeted Plio-Pleistocene Kakegawa and Ogasa Groups can be divided into 17 depositional sequences, and include six seismic facies indicating submarine-fan elements and surrounding slope to basin-floor environments. Next, facies maps for each depositional sequence unit were created by plotting all information on seismic facies, 3D seismic geomorphology, and well facies data. The obtained facies maps reveal that 11 major submarine canyons functioned as positionally fixed sediment supply systems from main land Japan, along which submarine fans were formed in the forearc basins. Submarine-fan depositional styles changed through Plio-Pleistocene from a braided channel type, through small radial fan, trough-fill fan, and muddy sheet fan types, to a channel-levee system type. Finally, the facies maps of each depositional sequence were overlaid with the BSR distribution. The overlaid maps indicate that the BSRs occur on feeder channels, distributary channels, and proximal lobes of submarine fans, suggesting that methane hydrates selectively occur in coarser grained portions of a submarine fan. Because the lower part of the Kakegawa Group is mainly composed of braided channel-type submarine fan turbidites, the lower Kakegawa horizon serves one of the major horizons bearing methane hydrates in the eastern Nankai Trough area.
{"title":"Sequence Stratigraphic Distribution Analysis of Methane-hydrate-bearing Submarine-fan Turbidite Sandstones in the Eastern Nankai Trough Area: Relationship between Turbidite Facies Distributions and BSR Occurrence","authors":"O. Takano, Mizue Nishimura, T. Fujii, T. Saeki","doi":"10.5026/JGEOGRAPHY.118.776","DOIUrl":"https://doi.org/10.5026/JGEOGRAPHY.118.776","url":null,"abstract":"Since previous research revealed that most of the methane hydrates in the eastern Nankai Trough area occur in matrix pores of turbidite sandstones, the facies distribution of turbidite sandstones may be one of the important keys to evaluate the distributions and actual volume of methane hydrates in the eastern Nankai Trough area. This paper attempts to reconstruct depositional processes of submarine-fan turbidites, and examines the relationship between turbidite facies distributions and bottom simulating reflector (BSR) occurrence as a proxy of methane hydrate using sedimentologic and sequence stratigraphic methodology. First, 2D/3D seismic survey data and well data including cores and logs were used to identify turbidite facies, seismic facies, and depositional sequences. The targeted Plio-Pleistocene Kakegawa and Ogasa Groups can be divided into 17 depositional sequences, and include six seismic facies indicating submarine-fan elements and surrounding slope to basin-floor environments. Next, facies maps for each depositional sequence unit were created by plotting all information on seismic facies, 3D seismic geomorphology, and well facies data. The obtained facies maps reveal that 11 major submarine canyons functioned as positionally fixed sediment supply systems from main land Japan, along which submarine fans were formed in the forearc basins. Submarine-fan depositional styles changed through Plio-Pleistocene from a braided channel type, through small radial fan, trough-fill fan, and muddy sheet fan types, to a channel-levee system type. Finally, the facies maps of each depositional sequence were overlaid with the BSR distribution. The overlaid maps indicate that the BSRs occur on feeder channels, distributary channels, and proximal lobes of submarine fans, suggesting that methane hydrates selectively occur in coarser grained portions of a submarine fan. Because the lower part of the Kakegawa Group is mainly composed of braided channel-type submarine fan turbidites, the lower Kakegawa horizon serves one of the major horizons bearing methane hydrates in the eastern Nankai Trough area.","PeriodicalId":356213,"journal":{"name":"Chigaku Zasshi (jounal of Geography)","volume":"106 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126852085","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1900-01-01DOI: 10.5026/JGEOGRAPHY.118.686
M. Radvanec
The extreme effect of the heat rays of the A-bomb explosion on August 6, 1945 at 8:15 a.m. in Hiroshima was studied on two tile fragments that had been excavated during the period from 1977 to 1982 from the west bank of Motoyasu River, about 100 m down the river from the Motoyasu bridge. A number of very hot and melted fragments, which the shock wave brought from buildings that were smashed at the hypocenter 1.318 s after the explosion, were deposited on the west bank of the river. The pieces of tile possibly came from the destroyed stone wall of the Sei Hospital, the Saikoji Temple, and/or the Sairenji Temple, and were quickly cooled by the river water. The tile fragments were composed of andesitic pyroclastic rock and their surfaces were melted to a depth of 3.18 mm. The glass crust had a variable andesite and basalt-andesite composition, which are the melt products of cristobalite and/or tridymite, pigeonite (XFe = Fe/(Fe + Mg) = 0.37-0.44), hornblende (XFe = 0.33-0.42), labradorite (Ab48.2-40.6An51.8-55.5Or0-3.9), and K-feldspar (Ab8.2Or91.8). The temperature of 6287°C was calculated on the surface of an object at the hypocenter after the explosion, according to the depth of 3.18 mm of the melt and different depths and melting points of above mentioned minerals. This surface temperature was deduced by the extrapolating of the depth-temperature relationship obtained by the mineral-relicts between 2.68 and 3.18 mm of depth. According to the regression line T = -1715.1d + 6287 (d is the depth) with R2 = 0.989, the temperature gradient in the andesite tile was 1715°C/mm, reaching a depth from 2.86 to 3.18 mm, where the volume of glass and volume of primary minerals (rock) are equal. For a depth of more than 3.64 mm, the structure and mineral assemblage of pyroclastic andesite rock has an initial composition.
{"title":"Pyroclastic Andesite Tile Melting during the First Two Seconds after the Explosion of the A-bomb at 8:15 a.m. on August 6, 1945 in Hiroshima","authors":"M. Radvanec","doi":"10.5026/JGEOGRAPHY.118.686","DOIUrl":"https://doi.org/10.5026/JGEOGRAPHY.118.686","url":null,"abstract":"The extreme effect of the heat rays of the A-bomb explosion on August 6, 1945 at 8:15 a.m. in Hiroshima was studied on two tile fragments that had been excavated during the period from 1977 to 1982 from the west bank of Motoyasu River, about 100 m down the river from the Motoyasu bridge. A number of very hot and melted fragments, which the shock wave brought from buildings that were smashed at the hypocenter 1.318 s after the explosion, were deposited on the west bank of the river. The pieces of tile possibly came from the destroyed stone wall of the Sei Hospital, the Saikoji Temple, and/or the Sairenji Temple, and were quickly cooled by the river water. The tile fragments were composed of andesitic pyroclastic rock and their surfaces were melted to a depth of 3.18 mm. The glass crust had a variable andesite and basalt-andesite composition, which are the melt products of cristobalite and/or tridymite, pigeonite (XFe = Fe/(Fe + Mg) = 0.37-0.44), hornblende (XFe = 0.33-0.42), labradorite (Ab48.2-40.6An51.8-55.5Or0-3.9), and K-feldspar (Ab8.2Or91.8). The temperature of 6287°C was calculated on the surface of an object at the hypocenter after the explosion, according to the depth of 3.18 mm of the melt and different depths and melting points of above mentioned minerals. This surface temperature was deduced by the extrapolating of the depth-temperature relationship obtained by the mineral-relicts between 2.68 and 3.18 mm of depth. According to the regression line T = -1715.1d + 6287 (d is the depth) with R2 = 0.989, the temperature gradient in the andesite tile was 1715°C/mm, reaching a depth from 2.86 to 3.18 mm, where the volume of glass and volume of primary minerals (rock) are equal. For a depth of more than 3.64 mm, the structure and mineral assemblage of pyroclastic andesite rock has an initial composition.","PeriodicalId":356213,"journal":{"name":"Chigaku Zasshi (jounal of Geography)","volume":"41 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123345410","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1900-01-01DOI: 10.5026/JGEOGRAPHY.118.854
Maki Matsuzawa, S. Nagakubo, T. Fujii
Studies of naturally existing methane hydrate are classified according to their aims; 1. Roles of methane hydrate in the global environment related mainly to global warming, 2. Potential as a natural resource, and 3. Drilling hazards and flow assurance of gas pipelines in oil and natural gas field developments. This report focuses on one of the field operations carried out in the eastern Nankai trough off Japan in 2004, which was part of the Japanese national project for methane hydrate study. The aim of this project is to assess the potential of methane hydrates off Japan as natural resources.
{"title":"Drilling into Methane Hydrate Concentration Zones","authors":"Maki Matsuzawa, S. Nagakubo, T. Fujii","doi":"10.5026/JGEOGRAPHY.118.854","DOIUrl":"https://doi.org/10.5026/JGEOGRAPHY.118.854","url":null,"abstract":"Studies of naturally existing methane hydrate are classified according to their aims; 1. Roles of methane hydrate in the global environment related mainly to global warming, 2. Potential as a natural resource, and 3. Drilling hazards and flow assurance of gas pipelines in oil and natural gas field developments. This report focuses on one of the field operations carried out in the eastern Nankai trough off Japan in 2004, which was part of the Japanese national project for methane hydrate study. The aim of this project is to assess the potential of methane hydrates off Japan as natural resources.","PeriodicalId":356213,"journal":{"name":"Chigaku Zasshi (jounal of Geography)","volume":"34 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123351409","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1900-01-01DOI: 10.5026/JGEOGRAPHY.118.207
A. Hachikubo, H. Sakagami, H. Minami, Yutaka Nunokawa, H. Shoji, T. Matveeva, Y. Jin, A. Obzhirov
New hydrate-bearing seepage structures off Sakhalin in the Sea of Okhotsk were investigated from 2003 to 2006 within the framework of the CHAOS project. We obtained samples of natural gas hydrate and measured the molecular and isotopic compositions of hydrate-bound gas. Methane δ13C and δD were in the range of -67 to -63‰ and -207 to -193‰, respectively. These results indicate a microbial origin produced by CO2 reduction according to Whiticar's diagram. Because ethane δ13C showed a thermogenic origin, hydrate-bound gas contains a small amount of thermogenic gas. The hydration numbers of the samples were estimated as 6.19 ± 0.02 using the Raman spectra of the C–H stretching mode and a thermodynamic calculation. Heat flow calorimetry revealed that the values for dissociation heat of the samples were 18.1 ± 0.3 kJ mol-1 (from hydrate phase to gas and ice phases) and 55.4 ± 0.4 kJ mol-1 (from hydrate phase to gas and water phases), which agree well with the values in of literature.
{"title":"Isotopic Composition and Crystallographic Properties of Gas Hydrate in the Sea of Okhotsk","authors":"A. Hachikubo, H. Sakagami, H. Minami, Yutaka Nunokawa, H. Shoji, T. Matveeva, Y. Jin, A. Obzhirov","doi":"10.5026/JGEOGRAPHY.118.207","DOIUrl":"https://doi.org/10.5026/JGEOGRAPHY.118.207","url":null,"abstract":"New hydrate-bearing seepage structures off Sakhalin in the Sea of Okhotsk were investigated from 2003 to 2006 within the framework of the CHAOS project. We obtained samples of natural gas hydrate and measured the molecular and isotopic compositions of hydrate-bound gas. Methane δ13C and δD were in the range of -67 to -63‰ and -207 to -193‰, respectively. These results indicate a microbial origin produced by CO2 reduction according to Whiticar's diagram. Because ethane δ13C showed a thermogenic origin, hydrate-bound gas contains a small amount of thermogenic gas. The hydration numbers of the samples were estimated as 6.19 ± 0.02 using the Raman spectra of the C–H stretching mode and a thermodynamic calculation. Heat flow calorimetry revealed that the values for dissociation heat of the samples were 18.1 ± 0.3 kJ mol-1 (from hydrate phase to gas and ice phases) and 55.4 ± 0.4 kJ mol-1 (from hydrate phase to gas and water phases), which agree well with the values in of literature.","PeriodicalId":356213,"journal":{"name":"Chigaku Zasshi (jounal of Geography)","volume":"75 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131633067","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1900-01-01DOI: 10.5026/JGEOGRAPHY.118.297
H. Matsuda
Dolomite (dolostone) is a common carbonate rock in the geological records and is also a very important carbonate reservoir rock, which stock about 40% of global oil reserves. Most of the dolomites in the geological record are considered to be of replacement origin, although some were precipitated directly from pore-fluids. A variety of dolomitization models in different diagenetic environments are currently proposed for interpreting ancient dolomites: (1) evaporative dolomitization including sabkha and seepage-reflux models, (2) mixed-water dolomitization, (3) marine dolomitization, (4) burial dolomitization, (5) hydrothermal dolomitization. The dolomites formed by each dolomitization model have different geological, petrographical, mineralogical and geochemical features. Based on these features, we can, therefore, identify dolomitization models and diagenetic environments of ancient dolomites. A dolomite reservoir is often of as good quality as a limestone reservoir. Dolomitization affects carbonate reservoir characteristics, such as porosity and permeability, and, as a result, reservoir characteristics are significantly changed from those of primary carbonate rocks. The important factors associated with dolomitization and controlling the characteristics of carbonate reservoir rocks are: (1) increasing crystal size (2) decreasing porosity due to a net addition of dolomite, (3) developing moldic pores, (4) increasing resistance to compaction, and (5) increasing fractures. Dolomitization and diagenetic history of individual carbonate reservoirs differ from each other and result in the complexity of reservoir characteristics. It is, therefore, indispensable to understand the processes that formed each dolomite reservoir.
{"title":"Dolomitization and Reservoir Characteristics","authors":"H. Matsuda","doi":"10.5026/JGEOGRAPHY.118.297","DOIUrl":"https://doi.org/10.5026/JGEOGRAPHY.118.297","url":null,"abstract":"Dolomite (dolostone) is a common carbonate rock in the geological records and is also a very important carbonate reservoir rock, which stock about 40% of global oil reserves. Most of the dolomites in the geological record are considered to be of replacement origin, although some were precipitated directly from pore-fluids. A variety of dolomitization models in different diagenetic environments are currently proposed for interpreting ancient dolomites: (1) evaporative dolomitization including sabkha and seepage-reflux models, (2) mixed-water dolomitization, (3) marine dolomitization, (4) burial dolomitization, (5) hydrothermal dolomitization. The dolomites formed by each dolomitization model have different geological, petrographical, mineralogical and geochemical features. Based on these features, we can, therefore, identify dolomitization models and diagenetic environments of ancient dolomites. A dolomite reservoir is often of as good quality as a limestone reservoir. Dolomitization affects carbonate reservoir characteristics, such as porosity and permeability, and, as a result, reservoir characteristics are significantly changed from those of primary carbonate rocks. The important factors associated with dolomitization and controlling the characteristics of carbonate reservoir rocks are: (1) increasing crystal size (2) decreasing porosity due to a net addition of dolomite, (3) developing moldic pores, (4) increasing resistance to compaction, and (5) increasing fractures. Dolomitization and diagenetic history of individual carbonate reservoirs differ from each other and result in the complexity of reservoir characteristics. It is, therefore, indispensable to understand the processes that formed each dolomite reservoir.","PeriodicalId":356213,"journal":{"name":"Chigaku Zasshi (jounal of Geography)","volume":"153 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123090547","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1900-01-01DOI: 10.5026/JGEOGRAPHY.118.1247
Y. Tabayashi, M. Yamamuro
We measured major inorganic ions and stable isotope ratios of nitrogen and oxygen of nitrate in the stream water in the Chichibu region during the course of nitrogen saturation. Nitrate concentration showed a high west-east gradient in the study area. Stable isotope ratios of oxygen in nitrate showed clear relationships with nitrate concentration. A direct relationship was apparent in the lower range of nitrate concentrations in that the stable isotope ratio of oxygen increases as the nitrate concentration increases. On the other hand, oxygen stable isotope ratios of nitrate hardly increase in the middle to higher concentrations of nitrate. This phenomenon may suggest that the oxygen stable isotope ratios of nitrate reflect a phase of the nitrogen saturation in the forest ecosystems.
{"title":"Oxygen-Stable Isotope Ratios of Nitrate and Nitrate Concentration in Stream Water during the Course of Nitrogen Saturation","authors":"Y. Tabayashi, M. Yamamuro","doi":"10.5026/JGEOGRAPHY.118.1247","DOIUrl":"https://doi.org/10.5026/JGEOGRAPHY.118.1247","url":null,"abstract":"We measured major inorganic ions and stable isotope ratios of nitrogen and oxygen of nitrate in the stream water in the Chichibu region during the course of nitrogen saturation. Nitrate concentration showed a high west-east gradient in the study area. Stable isotope ratios of oxygen in nitrate showed clear relationships with nitrate concentration. A direct relationship was apparent in the lower range of nitrate concentrations in that the stable isotope ratio of oxygen increases as the nitrate concentration increases. On the other hand, oxygen stable isotope ratios of nitrate hardly increase in the middle to higher concentrations of nitrate. This phenomenon may suggest that the oxygen stable isotope ratios of nitrate reflect a phase of the nitrogen saturation in the forest ecosystems.","PeriodicalId":356213,"journal":{"name":"Chigaku Zasshi (jounal of Geography)","volume":"26 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129683160","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1900-01-01DOI: 10.5026/JGEOGRAPHY.118.717
Takaaki Kawasumi
The timing of the maximum glacial advance during the last glacial period has been determined on the basis of stratigraphic relationships between marker tephras and ridges that form the lowest moraine of Mt. Shiroumadake (2,932 m), at the northern part of the Hida Range in central Japan, extending in the north-south direction for approximately 100 km. The glacier attained its maximum advance in early MIS 4 immediately before the fall of Tateyama E tephra (Tt-E, 70 MIS ka) and retreated with repetitive stagnation. When compared to published information on the northwest and southern parts of the range, glacial fluctuations on Mt. Shiroumadake and other high mountains were common around the fall of Tt-E. The glaciers appear to have attained their maximum advances synchronously in early MIS 4 over the Hida Range.
末次冰期最大冰川推进时间的确定，是根据在日本中部飞驒山脉北部形成Shiroumadake山最低冰碛(2932米)的山脊之间的地层关系确定的，该山脊向南北方向延伸约100公里。冰川在立山E冰川(Tt-E, 70 MIS ka)陷落之前的第4代早期达到了最大的推进，并以重复停滞的方式后退。与已公布的该山脉西北部和南部的信息相比，Shiroumadake山和其他高山的冰川波动在Tt-E下降前后很常见。在MIS 4早期，Hida山脉上的冰川似乎同步达到了最大进展。
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Pub Date : 1900-01-01DOI: 10.5026/JGEOGRAPHY.117.1077
H. Kanno
Mean summer temperatures in northern Japan appear to exhibit cyclical variations after the regime shift—global-scale climatic jump of oceanography and meteorology fields—around the late 1970s. Alternation between cool and hot summers has resulted in cool and hot weather damage to rice crops, respectively. The temperature fluctuations are caused by the Rossby wave propagation (Pacific-Japan pattern) from the tropical western Pacific (Nitta, 1987). This teleconnection also affects other regions, hence many agricultural districts in Asia may experience simultaneous meteorological effects. This paper focuses on the influence of the teleconnection pattern on three areas: northern Japan, northeastern China, and Java, Indonesia. These areas are important in terms of food supplies (mainly paddy rice production) for their countries. In northern Japan, variations of summer temperatures correlate strongly with the 500 hPa height field and SST east-west contrast around the western tropical Pacific. A positive correlation between the SST contrast and northern Japan summer temperatures has occurred since the 1980s, and it is clear that after the regime shift northern Japan summer temperatures have been affected by Rossby wave propagation from the tropical Pacific Ocean. The relations between summer temperatures in northern Japan and in Heilongjiang, northeastern China, and the global meteorology field were analyzed. Summer temperatures in northern Japan and Heilongjiang were found not to exhibit simultaneous variations. Northern Japan summer temperatures have a negative correlation with summer 500 hPa heights over a wide tropical area centered on the Indochina Peninsula and around eastern Siberia, which are the results of Rossby wave propagation and formation of Okhotsk high pressure in summer. In the case of Heilongjiang, there is not a strong correlation with the tropical area and there is no correlation around eastern Siberia. Hence, the teleconnection pattern does not strongly affect summer temperatures in northeastern China. Summer temperatures in northern Japan and spring surface pressure show a negative correlation around the Arabian Sea and the western tropical Pacific. This may signal the pre-Indian monsoon and pre-Asian monsoon pressure field. On the other hand, summer temperatures in Heilongjiang and the spring pressure field show a strong positive correlation over the Tibetan Plateau. This result raises interesting issues about their relationship, such as whether a spring high pressure indicates a dry surface over the plateau and whether an increase of sensible heat from the land affects any feedbacks in the next season. In summary, the factors that cause summer temperature variations over northern Japan and Heilongjiang, respectively, are different. Precipitation in JJA in Java and global surface pressure show a positive correlation around northern Japan. This implies that high precipitation over Java is related to a high-pressure anomaly over nor
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