Carbon and oxygen isotope chemostratigraphies of the Yangtze platform,South China: Decoding temperature and environmental changes through the Ediacaran     

Miyuki Tahata  Yuichiro Ueno  Tomoko Ishikawa  Yusuke Sawaki  Kazuki Murakami  Jian Han  Degan Shu  Yong Li  Junfeng Guo  Naohiro Yoshida  Tsuyoshi Komiya 《Gondwana Research》2013,23(1):333-353

Multicellular animals first appeared on the earth during the Ediacaran period. However, the relationship between the abrupt biological evolution and environmental changes is still ambiguous. In order to examine seawater temperature and the carbon cycle through the Ediacaran, we analyzed the carbon and oxygen isotope compositions of carbonate rocks from drill cores from the Three Gorges area, South China. Importantly, the core samples include the Nantuo tillite, corresponding to the Marinoan glaciation, through the Doushantuo to the lower Dengying Fms. in ascending order.The δ¹³C profile displays five positive and five negative anomalies (PI-1 to 5 and NI-1 to 5), and the oxygen isotopes display very high absolute values around 0‰ with the highest at + 1.83‰. The combined δ¹⁸O and δ¹³C chemostratigraphies display both positive and negative correlations between the δ¹⁸O and δ¹³C values. The occurrence of the negative correlations supports the preservation of primary δ¹⁸O and δ¹³C values.The sample NI-4 has a negative correlation of the δ¹⁸O and δ¹³C excursions. The correlation supports a primary signature for both δ¹⁸O and δ¹³C variations. The positive δ¹⁸O excursion, accompanied by evidence of a eustatic sea-level fall, provides direct evidence for global cooling in the mid-Ediacaran; the 580 Ma Gaskiers Glaciation is a potential candidate for this global cooling event. The negative δ¹³C excursion was possibly caused by an increase in remineralization of dissolved organic carbon (DOC) due to enhanced continental weathering during the glaciation.Sample NI-5 is characterized by very low δ¹³C values, down to ? 10‰, corresponding to the Shuram-Wonoka-Pertatataka Excursion. The cause of the δ¹³C negative excursion is still not clear. However, a ubiquitous occurrence in excursions worldwide, and the lower δ¹³C values in deeper sections favor the enhancement of remineralization and respiration rather than secondary alteration, a restricted sea environment and lithification in coastal areas.  相似文献   

Japan’s Nation-Wide Electronic Geotechnical Database Systems by Japanese Geotechnical Society     

Hiroaki Todo  Koji Yamamoto  Mamoru Mimura  Susumu Yasuda 《Geotechnical and Geological Engineering》2013,31(3):941-963

On October 15, 2010, the Japanese Geotechnical Society (JGS) announced the public release of ‘Nation-wide Electronic Geotechnical Database Systems,’ which provides geotechnical information to the public on the internet. The information the system provides is a collection of ground models at 250 m by 250 m in plan built by using data from various geotechnical information databases. The paper first describes historical development of the geotechnical information databases in Japan, and introduces a 5-year project, ‘Integrated Geophysical and Geological Information Database in Japan,’ led by the National Research Institute for Earth Science and Disaster Prevention (NIED), and participated by the JGS. The paper then presents the JGS’ ‘Nation-wide Electronic Geotechnical Database Systems,’ and describes why such system was proposed and built, followed by the presentation of the examples for possible application of the system.  相似文献   

Three-Dimensional Subsurface Structure Model of Kansai International Airport by Integration of Borehole Data and Seismic Profiles     

Naoto Inoue  Naoko Kitada  Keiji Takemura  Koji Fukuda  Tsuyoshi Emura 《Geotechnical and Geological Engineering》2013,31(3):881-890

The three-dimensional subsurface structure model around Kansai International Airport (KIX) has been developed based on the geologically and geotechnically investigated results of a large amount of borehole data for estimation of subsidence. The model consists of the alternation of marine clay and coarse deposits. The many seismic surveys and borehole drillings were carried out around the KIX before the constructing the airport. The stratigraphy of the model was renewed by the KIX18-1, which was about 1,300 m long drilling core and was drilled near the 2nd runway of the KIX from 2006 to 2007. In this study, the subsurface geological model was revised by integration of renewed borehole data and seismic profiles to incorporate complex warping structure and heterogenic lateral variation.  相似文献   

Lopingian (Late Permian) foraminiferal faunal succession of a Paleo-Tethyan mid-oceanic carbonate buildup: Shifodong Formation in the Changning–Menglian Belt, West Yunnan, Southwest China     

Katsumi  Ueno  Satoe  Tsutsumi 《Island Arc》2009,18(1):69-93

This paper deals with a Lopingian (Late Permian) foraminiferal faunal succession of the Shifodong Formation in the Changning–Menglian Belt, West Yunnan, Southwest China, which has been geologically interpreted as one of the closed remnants in East Asia of the Paleo‐Tethys Ocean. The Shifodong Formation is the uppermost stratigraphic unit in thick Carboniferous–Permian carbonates of the belt. These carbonates rest upon bases consisting of oceanic island basalt and are widely accepted as having a Paleo‐Tethyan mid‐oceanic (seamount‐ or oceanic plateau‐top) origin. Sixteen taxa of fusuline foraminifers and 37 taxa of smaller (non‐fusuline) foraminifers are recognized from the type section of the Shifodong Formation located in the Gengma area of the northern part of the Changning–Menglian Belt. Based on their stratigraphic distribution, three fusuline zones can be established in this section: they are, in ascending order, the Codonofusiella cf. C. kwangsiana Zone, Palaeofusulina minima Zone, and Palaeofusulina sinensis Zone. These three biozones are respectively referable to the Wuchiapingian, early Changhsingian, and late Changhsingian, of which the Wuchiapingian is first recognized in this study in the Changning–Menglian mid‐oceanic carbonates. The present study clearly demonstrates that the foraminiferal fauna in a Paleo‐Tethyan pelagic shallow‐marine environment still maintained high faunal diversity throughout the almost entire Lopingian, although the very latest Permian fauna in the upper part of the Palaeofusulina sinensis Zone of the Shifodong section records a sudden decrease in both faunal diversity and abundance. Moreover, the Shifodong faunas are comparable in diversity with those observed in circum‐Tethyan shelves such as South China. The present Paleo‐Tethyan mid‐oceanic foraminiferal faunas are definitely more diversified than coeval mid‐oceanic Panthalassan faunas, which are typically represented by those from the Kamura Limestone in a Jurassic accretionary complex of Southwest Japan. It is suggestive that the Paleo‐Tethyan mid‐oceanic buildups presumably supplied a peculiarly hospitable habitat for foraminiferal faunal development in a pelagic paleo‐equatorial condition.  相似文献   

Foraminiferal evidence of submarine sediment transport and deposition by backwash during the 2004 Indian Ocean tsunami     

Daisuke  Sugawara  Koji  Minoura  Naoki  Nemoto  Shinji  Tsukawaki  Kazuhisa  Goto  Fumihiko  Imamura 《Island Arc》2009,18(3):513-525

Micropaleontological analysis of nearshore to offshore sediments recovered from the southwestern coast of Thailand was performed to clarify the submarine processes of sediment transport and deposition during the 2004 Indian Ocean tsunami. The distribution pattern of benthic foraminifers showed seaward migration after the tsunami event. Agglutinated foraminifers, which are characteristic of an intertidal brackish environment, were identified in the post-tsunami samples from foreshore to offshore zones. These suggest that sediments originally distributed in foreshore to nearshore zones were transported offshore due to the tsunami backwash. On the other hand, the distribution pattern of planktonic and benthic species living in offshore zones showed slight evidence of landward migration by the tsunami. This suggests that landward redistribution of sediments by the tsunami run-up did not occur in the offshore seafloor of the study area. Our results and a review of previous studies provide an interpretation of submarine sedimentation by tsunamis. It is possible that tsunami backwashes induce sediment flows that transport a large amount of coastal materials seaward. Thus, traces of paleotsunami backwashes can be identified in offshore sedimentary environments as the accumulation of allochthonous materials. This can be recognized as changes in benthic foraminiferal assemblages.  相似文献   

Secondary remanent magnetization carried by magnetite inclusions in silicates: a comparative study of unremagnetized and remagnetized granites     

Yo-ichiro Otofuji  Koji Uno  Takahiro Higashi  Tomomichi Ichikawa  Tsuyoshi Ueno  Toshiaki Mishima  Takaaki Matsuda 《Earth and Planetary Science Letters》2000,180(3-4):271-285

Magnetic carriers in remagnetized Cretaceous granitic rocks of northeast Japan were studied using paleomagnetism, rock magnetism, optical microscopy and scanning electron microscopy (SEM) by comparison with unremagnetized granitic rocks. The natural remanent magnetization (NRM) of the remagnetized rocks is strong (0.3–1.7 A/m) and shows a northwesterly direction with moderate inclination (NW remanence), whereas the unremagnetized rocks preserve weak NRM (<0.5 A/m) with westerly and shallow direction (W remanence). Although thermal demagnetization shows that both NRMs are carried by magnetite, the remagnetized rocks reveal a higher coercivity with respect to alternating field demagnetization (20 mT相似文献   

Rapid Identification of Water-Conducting Fractures Using a Trace Methane Gas Measurement     

Masakazu Niwa Ph.D  Kenji Amano Ph.D  Ryuji Takeuchi Ph.D  Koji Shimada Ph.D 《Ground Water Monitoring & Remediation》2021,41(3):41-50

Identification of water-conducting fractures is important for the safety assessment of underground projects in crystalline rocks at geological disposal sites. We applied a portable methane gas analyzer by wavelength-scanned cavity ring-down spectroscopy to detect the water-conducting fractures in the underground tunnel of the Mizunami Underground Research Laboratory, central Japan. The tunnel is excavated in granite with CH₄-rich groundwater. Two approaches were taken to obtain the profile of CH₄ concentration along the gallery walls: (1) “Scan by walking” at the speed of 0.5 m/s and (2) monitoring for 30 s at 0.5 or 1 m intervals. In the Scan by walking approach, the peaks of the CH₄ concentration corresponded well with the occurrence of high water flow rate fractures. Thus, this method is useful for rapid identification of major water-conducting fractures. Monitoring at constant intervals takes more time than the Scan by walking approach; however, this method can largely detect occurrences of fractures with low fluid fluxes.  相似文献   

Choice of conodont Idiognathodus simulator （sensu stricto） as the event marker for the base of the global Gzhelian Stage （Upper Pennsylvanian Series,Carboniferous System）   总被引：3，自引：0，他引：3  

Philip H. Heckel  ;Aleksandr S. Alekseev  ;James E. Barrick  ;Darwin R. Boardman  ;Natalya V. Goreva  ;Tatiana N. Isakova  ;Tamara I. Nemyrovska  ;Katsumi Ueno  ;Elisa Villa  ;David M. Work 《《幕》》2008,31(3):319-325

We propose that the level at which the conodont species Idiognathodus simulator （Ellison 1941） （sensu stricto） first appears be selected to mark the base of the Gzhelian Stage, because we believe that this is the optimal level by which this boundary can be correlated. This taxon has a short range and a wide distribution, as shown by correlation of glacial-eustatic cyclothems across the Kasimovian-Gzhelian boundary interval among Midcontinent North America and the Moscow and Donets basins of eastern Europe, based on scale of the cyclothems along with several aspects of biostrati- graphy. Outside of these areas, I. simulator （sensu stricto） is known also from other parts of the U.S., and is reported from the southern Urals and south-central China in its expected position between other widespread taxa. Its first appearance is consistent with the current ammonoid placement of the boundary （first appearance of Shumardites cuyleri）, and it is also compatible with certain aspects of the distribution of Eurasian fusulinid faunas （e.g., lectotype ofRauserites rossicus）.  相似文献   

Stress-induced crack path in Aji granite under tensile stress     

Yozo Kudo  Osam Sano  Naokuni Murashige  Yoshiaki Mizuta  Koji Nakagawa 《Pure and Applied Geophysics》1992,138(4):641-656

The double-torsion test using Aji granite was carried out to investigate the interaction between stress-induced crack path and mineral grains. Crack velocities were controlled at range 10^–7 m/s to 10^–1 m/s. After the stressed specimens were dyed, we checked the crack path by thin section analysis, using an optical microscope. The stress-induced crack path was divided into two types, transgranular and intergranular cracks, and each path was subdivided with respect to mineral grains. In spite of the extensive range of crack velocities, the ratios between the transgranular and intergranular crack lengths did not change. The crack paths were all jagged, and often showed detour around the grain boundary when faced with obstacles like hard grains or preexisting cracks. That is to say, quartz grain played an important role as an obstacle. Feldspar grain could change the crack path because of its cleavage plane. Biolite grain had a serious effect on the path even if its constitution ratio is very small. Fractal dimensions of the crack paths were calculated by three methods, as indicators of surface roughness. The fractal dimensions were shown in a slight trend with the change of crack velocity. This trend can be explained from the point of limited cracking rate in stress corrosion.  相似文献   

Model analysis of radar echo split observed in an artificial cloud seeding experiment          下载免费PDF全文

Shimada Masaki  Tomine Kikuro  Nishiyama Koji 《Acta Meteorologica Sinica》2016,30(3):386-400

An artificial cloud seeding experiment was performed over the Japan Sea in winter to show how massive seeding could be effective to mitigate heavy snowfall damage. The results showed that 20 min after cloud seeding, a portion of the radar echo beneath the seeding track was weakened to divide the radar echo into two parts. In order to analyze the results, a numerical simulation was conducted by using the Weather Research and Forecasting model verion 3.5.1. In this simulation, the seeding effects were represented as phenomena capable of changing rain particles by accreting cloud ice and snow to form graupel particles and by changing cloud liquid water to snow particles. The graupel particles fell rapidly, thus temporarily intensifying the rainfall, which subsequently decreased. Therefore, the weakened radar echo in the field experiment is deemed to have been caused by the increase in rapidly falling graupel particles.  相似文献