Kyushu University Academic Staff Educational and Research Activities Database
List of Presentations
Yoshihiro Kuwahara Last modified date:2022.03.24

Professor / Course for Earth Changes / Department of Environmental Changes / Faculty of Social and Cultural Studies


Presentations
1. Thinh Nguyen Van, Yoshihiro Kuwahara, Masaru Matsumoto, Dinh Xuan Thanh, Nguyen Dinh Nguyen, Myo Zaw , Investigation the sources of arsenic and the formation process of arsenic-rich peat in groundwater level in Asia, JpGU2021, 2021.05.
2. 加藤千恵、大野正夫、桑原義博(九大比文)、畠山唯達(岡山理大)、山田康洋(東京理大)、戸塚修平(産総研)、島田和彦、石橋純一郎(九大理)、長瀬敏郎(東北大博物館), Magnetic properties of isocubanite from submarine hydrothermal deposits in the Okinawa Trough, JpGU2021, 2021.05.
3. Bun Liu, Yoshihiro Kuwahara, Keisuke Otsuka, Masato Makio, In situ hot/cool-stage AFM study on crystal growth of barite at 10 – 40°C, JpGU-AGU Joint Meeting 2017, 2017.05.
4. Masato Makio, Masahiko Sato, Tatsuya Hayashi, Yoshihiro Kuwahara, Masao OHNO, Shu Fujita, Shun Chiyonobu, Tokiyuki Sato, Millennial scale linkage between iceberg collapse and ocean circulation after intensification of Northern Hemisphere glaciation, International Union for Quaternary Research XIX Congress, 2015.08.
5. Masato Makio, Masahiko Sato, Tatsuya Hayashi, Yoshihiro Kuwahara, Masao OHNO, Orbital- and millennial-scale change in the components of the North Atlantic sediments resolved by isothermal remanent magnetization acquisition experiments , International Union for Quaternary Research XIX Congress, 2015.07.
6. Masao OHNO, Masahiko Sato, Tatsuya Hayashi, Yoshihiro Kuwahara, Chizuru Miyagawa, Shu Fujita, Itsuro Kita, A rock-magnetic proxy of deep water circulation in the North Atlantic during the early Pleistocene, Asia Oceania Geoscience Society, 2014.07, Ocean thermohaline circulation (THC) plays an important role in global climate change linked with continental ice sheets. To clarify the variation of THC in the early stage of glaciations in northern hemisphere, we studied a deep-sea sediment core with high sedimentation rate between 2.2 and 2.7 Ma recovered at IODP Site U1314 in the North Atlantic..
7. Masao OHNO, Masahiko Sato, Yoshihiro Kuwahara, Tatsuya Hayashi, Chizuro Miyagawa, Itsuro Kita, ROCK MAGNETIC STUDY OF MILLENIAL-SCALE ENVIRONMENTAL CHANGE IN THE SUBPOLER NORTH ATLANTIC AFTER INTENSIFICATION OF NORTHERN HEMISPHERE GLACIATION, International Association of Geomagnetism and Aeronomy 2013, 2013.08, We have investigated the millennial-scale environmental change in the subpolar North Atlantic after the intensification of Northern Hemisphere glaciation from a sediment core drilled at IODP Site U1314, located in the southern Gardar Drift at a water depth of 2820 m. We have performed Ice-rafted detritus (IRD) counts, XRD measurement, rock-magnetic analysis of the sediments at every 2cm interval, that is, at every 100~200 years approximately..
8. This paper reports the results of clay mineral analysis (the amount of clay fraction, clay mineral assemblages, illite crystallinity) of samples collected from a drilled core (Rabibhawan (RB) core) located in the westcentral part of the Kathmandu Basin on the southern slope of the Central Himalaya. The amount of clay fraction in the core sediments between 12 m and 45 m depth (corresponding to ca. 17–76 ka), which belong to the Kalimati Formation, is variable and shows three clay-poor zones (19–31 ka, 44–51 ka, and 66–75 ka). The variations correspond with those of illite crystallinity index (Lanson index (LI) and modified Lanson index (MLI)) and kaolinite/illite ratio as well as the fossil pollen and diatom records reported by previous workers. These data reveal the following transformations occurring during the weathering process in this area:

micas (mainly muscovite)→illite(→illite−smectitemixedlayer mineral(R = 1))→kaolinite

The sedimentation rate (~50 cm/kyr) of clay-poor zones that correspond to dry climate intervals is only half that of clay-rich zones (~120 cm/kyr) that correspond to wet climate intervals, indicating weakened chemical weathering and erosion and low suspended discharge during dry climate intervals. The clay-poor zones commonly show unique laminite beds with very fine, authigenic calcite, which was probably precipitated under calm and high calcite concentration conditions caused by low precipitation and run-off. The variations between dry and wet conditions in this area as deduced from clay minerals appear to follow the Indian Summer Monsoon Index (ISMI) (30°N–30°S, 1 July) and northern hemisphere summer insolation (NHSI) signals (30°N) at 1 July, especially during the dry climate zones, whereas the wet maxima of the wet climate zones somewhat deviate from the strongest NHSI. On the other hand, the dry–wet records lead markedly the SPECMAP stack (by about 5000 years). These results suggest that the Indian summer monsoon precipitation was strongly controlled by the NHSI or summer insolation difference between the Himalayan–Tibetan Plateau and the subtropical Indian Ocean, showing a major fluctuation on the 23,000 years precessional cycle, and that it was not driven by changes in high-latitude ice volume, although the records of clay mineral indices during the wet intervals leave a question that other factors, in addition to insolation forcing, may play important roles in weathering, erosion, and sedimentation processes..
9. The dissolution behavior of the barite (001) surface in pure water at 30°C was investigated using in situ AFM, to better understand the dissolution mechanism and the microtopographical changes that occur during the dissolution. The dissolution of the barite (001) surface could be divided into three stages. The first stage of the dissolution was characterized only by the retreat of various steps that were formed mechanically by the initial cleaving. During the second stage, the change in the retreat behavior (from a step with one layer to a “f” step with an upper half-unit cell layer and a “s” step with a lower half-unit cell layer) and the formation of etch pits were observed. The last stage of the dissolution was characterized by an increase of the stable steps parallel to the [010] direction, followed by a decrease of steps parallel to , and the development of angular deep etch pits..
10. Controlling weathering and erosion intensity on the southern slope of the Central Himalaya by the Indian summer monsoon during the last glacial.
11. In-situ hot stage AFM study on muscovite dissolution at 20-50C under alkaline conditions.
12. In-situ AFM observations on muscovite dissolution at 20-50C under alkaline conditions.
13. Paleoclimate and paleoenvironment changes during the last 50kyr recorded in clay minerals in the Kathmandu Basin sediments, Central Nepal Himaraya.
14. Mineral behavior in Paleoclimate and paleoenvironment changes in the Kathmandu Basin sediments, Central Nepal Himaraya during the last 50kyr.
15. In situ AFM study on smectite and muscovite dissolutions under high pH conditions.
16. The dissolution behaviors of muscovite and smectite under alkaline conditions at 25°C to 50°C were investigated using in-situ atomic force microscopy (AFM) with an air/fluid heater system, in order to understand the dissolution mechanism and to derive reliable dissolution rates of these minerals.The both minerals showed the same dissolution behavior in which the reactive surface was only the edge surfaces and any new etch pits were not formed on the basal surfaces within the experimental durations. The dissolution rates normalized to the edge surface area (ESA) of these minerals were also approximately the same. In addition, the effects of temperature on the ESA-normalized dissolution rates were very similar each other. These results suggest that the dissolution mechanisms (e.g., reactive surface, the rate-limiting step) of muscovite and smectite are identical each other. The dissolution rates normalized to the total surface area (TSA) of initial particle size (smectite) or initial etch pit size (muscovite) varied with the particle or etch pit size, respectively..
17. In-situ, real time AFM study of smectite dissolution under high pH conditions at 25-50°C..
18. 25℃〜50℃における高pH下でのスメクタイト溶解のAFMその場観察.
19. In-site, real time AFM observations of smectite dissolution under high PH conditions..
20. Variations of paleoclimate and paleoenvironment during the last 50 kyr in the Kathmandu Valley, Central Nepal, Himalayas: From the results of clay mineral study.
21. Changes in mineral composition and depositional environments recorded in the present and past basin-fill sediments of the Kathmandu Valley, central Nepal.
22. Variations of Paleoclimate and paleoenvironment during the last 40kyr recorded in clay minerals in the Kathmandu Basin sediments.
23. Variations of paleoclimate and paleoenvironment recorded in clay minerals in the Kathmandu Basin sediments, central Nepal, Himalaya.
24. AFM observation of hydrothermal illite in Izumiyama Pottery stone from Arita, Saga prefecture, Japan.
25. Quaternary paleoclimatic history in the Central Himalaya on the basis of palynological study.
26. Variations of paleoclimate and paleoenvironment during the last 50 kyr recorded in clay minerals in the Kathmandu Basin sediments.
27. Academic core drilling of the Paleo-Kathmandu Lake and its research results---the first report.
28. Paleoclimatic variation during the last 50 kyr recorded in clay minerals in the Kathmandu Basin sediments, Central Nepal Himalayas.
29. Reconstruction of paleoclimatic variations recorded in clay minerals in the Kathmandu Basin sediments by XRD decomposition.
30. Uplift of the Mahabharat Range at 1Ma and its consequence on the sedimentary history of the Paleo-Kathmandu Lake.
31. Measurement of crystallinity and relative amount of clay minerals in the Kathmandu Basin sediments by decomposition of XRD patterns (profile fitting).
32. AFM observation of hydrothermal illite in Izumiyama pottery stone from Arita, Saga prefecture, Japan.
33. Comparison of the surface structure of the tetrahedral sheets of muscovite and phlogopite by AFM in liquid.
34. Atomic scale imaging of the cleavage surface of mica by fluid CMAFM.
35. AFM observation of sericite in Izumiyama pottery stone from Arita, Saga prefecture, Japan.
36. AFM observation of morphology and surface structure of sericite.
37. Observation of surface strucute of sericite by AFM - A comparative study of CMAFM and TMAFM -.
38. Study on mix-layer minerals by TEM with UTW-EDS.
39. Experimental study on alteration process of phlogopite.
40. Experimental study on dissolution process of phlogopite.
41. Reaction of mica on hydrothermal solutions.
42. Alteration of volcanic glass under high alkaline conditions.