越南红河三角洲近五千年来的几个降温事件     

李珍  臧家业  SAITO Yoshiki  徐小薇  王永吉  MATSUMOTO Eiji  张志英 《海洋科学进展》2005,23(1):43-53

根据对越南红河三角洲的2个钻孔的孢粉分析结果，结合沉积特征和高精度的AMS^14C测年数据，恢复了近五千年来百年一千年尺度的气候变化，发现了3个分别开始于4530cal．aBP，2100cal．aBP和620cal．aBP的明显降温事件，其中4530cal．aBP和620cal．aBP降温事件可与全球全新世气候变冷事件中的“新冰期(Neoglacial)”和“小冰期(Little Ice Age)”相对应，可能与由北大西洋地区几个短期变冷事件的全球气候响应机制有关。3340cal．aBP以来，人类干扰性植物成分的增加，表明人类活动对自然植被的影响改造作用增强，因此，本研究中气候的降温事件不排除人类影响的因素，仍需要进一步深入研究。  相似文献   

Correlation between crystallographic structure and infrared spectra of silicon oxide films containing iron or magnesium atoms     

N. SUZUKI  S. KIMURA  T. NAKADA  C. KAITO  Y. SAITO  C. KOIKE 《Meteoritics & planetary science》2000,35(6):1269-1273

Abstract— Films condensed from vapors containing SiO, Fe, or Mg showed an amorphous structure. Infrared (IR) spectra and electron microscopic characterization have been carried out on these films. After the heat treatment of these films in air, IR peaks at approximately 18–23 μm appeared, in addition to peaks attributable to SiO₂. These peaks can be attributed to metallic oxides such as FeO, Fe₂O₃, and MgO. It can be concluded that Fe‐ or Mg‐bearing silicate minerals cannot be produced by the rapid cooling of SiO, Fe, or Mg vapors. Although IR spectra of FeO have been discussed in order to match some spectra obtained with the Infrared Space Observatory, the identification of FeO as the impurity would be very important because the IR spectra of FeO grains are very dependent on the shape and size of the grains. These impurities can also influence the IR spectral feature of SiO₂.  相似文献   

Spatial and temporal distribution of Fe, Ni, Cu and Pb along 140°E in the Southern Ocean during austral summer 2001/02     

Xiaodong Lai  Kazuhiro Norisuye  Michi Mikata  Tomoharu Minami  Andrew R. Bowie  Yoshiki Sohrin   《Marine Chemistry》2008,111(3-4):171-183

The distribution of dissolved (D) and acid-dissolvable (AD) Fe, Ni, Cu and Pb in the upper water column (0–300 m depth) was determined in the Australian sector of the Southern Ocean (140°E meridian) during three cruises conducted between November 2001 and March 2002. For Ni and Cu, there was no significant difference in concentration between dissolved and acid-dissolvable species. DNi and DCu showed significant (P = 0.01) positive correlations with silicate, phosphate and nitrate, reflecting their strong nutrient-type behaviour. For Fe and Pb, the acid-dissolvable concentration mostly exceeded the dissolved concentration, reflecting the importance of labile particulate species for these elements. DPb decreased between January and February in the Polar Frontal Zone and in Antarctic continental shelf water. ADPb maxima occurred in the Antarctic Zone, resulting in a maximum AD/D ratio of 7. The mean DFe concentration in the surface mixed layer was 0.3 nM in the sub-Antarctic zone, 0.4 nM in the Polar Frontal Zone, 0.5 nM in the Antarctic Zone and increased southward beyond the Antarctic Divergence and towards the continent. DFe did not show a clear temporal change in its horizontal distribution, which was in contrast to the other nutrients and trace metals. ADFe substantially increased in Antarctic continental shelf water where the AD/D ratio reached 11. The following conclusions can be drawn from these data. (1) Ni and Cu exist exclusively as dissolved species and their distributions are mainly controlled by their biogeochemical cycling, similar to those of the major nutrients. (2) Pb is dominated by particulate species. The distribution of DPb is temporally and spatially variable due to a sporadic source and strong scavenging. (3) DFe is rather a minor fraction of total Fe in Antarctic continental shelf water where shelf sediments and Antarctic sea-ice appear to be strong sources for Fe. There is substantial temporal variation in the supply of Fe to the upper water column. DFe in the mixed layer of the open Southern Ocean is maintained at low concentrations throughout summer due to uptake by phytoplankton and scavenging.  相似文献   

Observations of Coherent Turbulence Structures in the Near-Neutral Atmospheric Boundary Layer   总被引：1，自引：1，他引：0  

Mitsuaki Horiguchi  Taiichi Hayashi  Hiroyuki Hashiguchi  Yoshiki Ito  Hiromasa Ueda 《Boundary-Layer Meteorology》2010,136(1):25-44

Turbulence structures of high Reynolds number flow in the near-neutral atmospheric boundary layer (ABL) are investigated based on observations at Shionomisaki and Shigaraki, Japan. A Doppler sodar measured the vertical profiles of winds in the ABL. Using the integral wavelet transform for the time series of surface wind data, the pattern of a descending high-speed structure with large vertical extent (from the surface to more than 200-m level) is depicted from the Doppler sodar data. Essentially this structure is a specific type of coherent structure that has been previously shown in experiments on turbulent boundary-layer flows. Large-scale high-speed structures in the ABL are extracted using a long time scale (240 s) for the wavelet transform. The non-dimensional interval of time between structures is evaluated as 3.0–6.2 in most cases. These structures make a large contribution to downward momentum transfer in the surface layer. Quadrant analyses of the turbulent motion measured by the sonic anemometer (20-m height) suggest that the sweep motion (high-speed downward motion) plays a substantial role in the downward momentum transfer. In general, the contribution of sweep motions to the momentum flux is nearly equal to that of ejection motions (low-speed upward motions). This contribution of sweep motions is related to the large-scale high-speed structures.  相似文献   

Lithological and palynological evidence of late Quaternary depositional environments in the subaqueous Yangtze delta, China   总被引：2，自引：0，他引：2  

Zhanghua Wang  Hao Xu  Qing Zhan  Yoshiki Saito  Zhongfa He  Jianlei Xie  Xiao Li  Yonghong Dong 《Quaternary Research》2010,73(3):550-562

AMS ¹⁴C ages of post-glacial core sediments from the subaqueous Yangtze delta, along with sedimentary structures and distributions of grain size, pollen spores, and dinoflagellate cysts, show an estuarine depositional system from 13 to 8.4 cal ka BP and a deltaic system from 5.9 cal ka BP to the present. The estuarine system consists of intertidal to subtidal flat, estuarine, and estuarine-front facies, characterized by sand–mud couplets and a high sedimentation rate. The deltaic system includes nearshore shelf and prodelta mud featured by lower sedimentation rate, markedly fewer coastal wetland herbaceous pollens, and more dinoflagellate cysts. We explain the extremely high sedimentation rate during 9.2–8.4 cal ka BP at the study site as a result of rapid sea-level rise, high sediment load due to the unstable monsoonal climate, and subaqueous decrease of elevation from inner to outer estuary. A depositional hiatus occurred during 8.2–5.9 cal ka BP, the transition from estuarine to deltaic system, caused possibly by a shortage of sediment supply resulting from delta initiation in paleo-incised Yangtze valley and strong tidal or storm-related reworking in offshore areas. The subsequent development of deltaic system at the study site indicates accelerated progradation of Yangtze delta post-5.9 cal ka BP.  相似文献   

Erratum to: Stoichiometry among bioactive trace metals in seawater on the Bering Sea shelf     

Abigail Parcasio Cid  Syouhei Urushihara  Tomoharu Minami  Kazuhiro Norisuye  Yoshiki Sohrin 《Journal of Oceanography》2012,68(3):483-484

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Rapid flooding of the southern Vietnam shelf during the early to mid‐Holocene          下载免费PDF全文

RIK TJALLINGII  KARL STATTEGGER  PAOLO STOCCHI  YOSHIKI SAITO  ANDREAS WETZEL 《第四纪科学杂志》2014,29(6):581-588

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Evidence for ca. 7‐ka maximum Holocene transgression on the Peninsular Malaysia east coast          下载免费PDF全文

PETER R. PARHAM  YOSHIKI SAITO  NORAISYAH SAPON  ROKIAH SURIADI  NOOR AZARIYAH MOHTAR 《第四纪科学杂志》2014,29(5):414-422

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Surface deformation related to the 2008 Wenchuan earthquake,and mountain building of the Longmen Shan,eastern Tibetan Plateau     

Bihong Fu  Pilong Shi  Huadong Guo  Satoshi Okuyama  Yoshiki Ninomiya  Sarah Wright 《Journal of Asian Earth Sciences》2011,40(4):805-824

The 12 May 2008 M_s 8.0 Wenchuan earthquake, China, was one of largest continental thrusting events worldwide. Based on interpretations of post-earthquake high-resolution remote sensing images and field surveys, we investigated the geometry, geomorphology, and kinematics of co-seismic surface ruptures, as well as seismic and geologic hazards along the Longmen Shan fold-and-thrust belt. Our results indicate that the Wenchuan earthquake occurred along the NE–SW-trending Yingxiu–Beichuan and Guanxian–Anxian faults in the Longmen Shan fold-and-thrust belt. The main surface rupture zones along the Yingxiu–Beichuan and Guanxian–Anxian fault zones are approximately 235 and 72 km in length, respectively. These sub-parallel ruptures may merge at depth. The Yingxiu–Donghekou surface rupture zone can be divided into four segments separated by discontinuities that appear as step-overs or bends in map view. Surface deformation is characterized by oblique reverse faulting with a maximum vertical displacement of approximately 10 m in areas around Beichuan County. Earthquake-related disasters (e.g., landslides) are linearly distributed along the surface rupture zones and associated river valleys.The Wenchuan earthquake provides new insights into the nature of mountain building within the Longmen Shan, eastern Tibetan Plateau. The total crustal shortening accommodated by this great earthquake was as much as 8.5 m, with a maximum vertical uplift of approximately 10 m. The present results suggest that ongoing mountain building of the Longmen Shan is driven mainly by crustal shortening and uplift related to repeated large seismic events such as the 2008 Wenchuan earthquake. Furthermore, rapid erosion within the Longmen Shan fold-and-thrust belt occurs along deep valleys and rupture zones following the occurrence of large-scale landslides triggered by earthquakes. Consequently, we suggest that crustal shortening related to repeated great seismic events, together with isostatic rebound induced by rapid erosion-related unloading, is a key component of the geodynamics that drive ongoing mountain building on the eastern Tibetan Plateau.  相似文献   

Proposal for an International Molybdenum Isotope Measurement Standard and Data Representation     

Thomas F. Nägler  Ariel D. Anbar  Corey Archer  Tatiana Goldberg  Gwyneth W. Gordon  Nicolas D. Greber  Christopher Siebert  Yoshiki Sohrin  Derek Vance 《Geostandards and Geoanalytical Research》2014,38(2):149-151

Molybdenum isotopes are increasingly widely applied in Earth Sciences. They are primarily used to investigate the oxygenation of Earth's ocean and atmosphere. However, more and more fields of application are being developed, such as magmatic and hydrothermal processes, planetary sciences or the tracking of environmental pollution. Here, we present a proposal for a unifying presentation of Mo isotope ratios in the studies of mass‐dependent isotope fractionation. We suggest that the δ^98/95Mo of the NIST SRM 3134 be defined as +0.25‰. The rationale is that the vast majority of published data are presented relative to reference materials that are similar, but not identical, and that are all slightly lighter than NIST SRM 3134. Our proposed data presentation allows a direct first‐order comparison of almost all old data with future work while referring to an international measurement standard. In particular, canonical δ^98/95Mo values such as +2.3‰ for seawater and ?0.7‰ for marine Fe–Mn precipitates can be kept for discussion. As recent publications show that the ocean molybdenum isotope signature is homogeneous, the IAPSO ocean water standard or any other open ocean water sample is suggested as a secondary measurement standard, with a defined δ^98/95Mo value of +2.34 ± 0.10‰ (2s).  相似文献